-------
Industrial Emission Impacts in the New Jersey
Environment: Results from a Study Near a Barrel
and Pail Manufacturing Plant
John Jenks - Office of Science and Research, fU
Dept. of Environmental
R. Harkov Protection, CN-409, Trenton, NJ
08625
C. Rugger!
Abstrac t
Industrial emissions can have a significant impact on localized air
quality in many urban areas. Many older urban/industrial areas contain
manufacturing plants in close proximity to residential areas and which do
not possess adequate air pollution control devices to minimize emissions.
The present report summarizes the monitoring results obtained In the
vicinity of a steel barrel and pall manufacturing plant in Jersey City,
NJ. Local residents have complained of odors, headaches and nose bleeds
from emissions from this plant. Although the surface coating materials
utilized by the facility do not contain known carcinogens, these
substances (xylenes, methylethylketone, acetone, butanol, etc.) are known
to have relatively low odor thresholds. A sampling scheme was developed
to obtain upwind, downwind and maximum Impact data resulting from the
emissions from this facility. All fixed site samples (4 hrs.) were
collected on glass cartridges containing 1.1 gm Tenax-GC utilizing
Nutech-221-1MC sampling pumps, while DuPont-Alplia-1 personal monitoring
pumps were utilized to collect short-term (15 min.) peak levels of the
selected substances. Cartridges were analyzed by thermal desorption into
a HP 5995 GC/MS, equipped with a volatile organic column. The entire
study was conducted utilizing a mobile laboratory (MKU) specially
designed for thermal desorption - GC/MS analyses. Results from this
monitoring effort indicate that levels of selected solvents measured in
the community near the barrel and pail plant were not in excess of
351
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published odor thresholds. However, it was clearly demonstrated that the
manufacturing facility caused localized degradation of air quality.
INTRODUCTION - Volatile organic compounds (VOC) are thought to be of some
environmental importance because of their role in: a) carcinogenesis, b)
ozone formation, and c) smog aerosol formation (Harkov et al 1983, NAS
1977). In addition to these impact areas, VOC can be of localized
significance as a nuisance (odor causing agent) and/or as an irritant if
emitted by specific industrial sources. Some VOC that have particularly
low odor threholds and also may cause a hypersensitive response in a
portion of a population include: aldehydes, ketones and organic acids
(Verschueren 1983, Keg et al 1977, Fay and Billings 1980). (n the
present context VOC are delimited as those substances with a vapor
pressure greater than or equal to 0.02 psi.
Industrial impacts on localized VOC levels have been seldom reported
in the technical literature (Sexton and Westberg 1980, Pellizari, 1982).
Odor related VOC emission impacts also have been reported infrequently in
the air pollution literature (Van Langenhose et al 1982). In New Jersey,
studies have been conducted on the levels of selected VOC at urban and
rural background locations (Harkov et a] 1981, Harkov et al 1983, 1984)
and most recently at site specific locations such as Superfund sites
(Harkov et al 1985) and sewage treatment plants (Harkov et al 1986).
Industrial based investigations of VOC in New Jersey have recently been
initiated utilizing a mobile monitoring unit (MMU) (Haggert and Harkov,
1985). The present report contains resulLs from an air quality
investigation near a steel barrel and pail manufacturing facility in
Jersey City, New Jersey. This facility has caused localized odor and
irritant problems in the nearby neighborhood and grade school.
METHODS
Description of Facility - The barrel and pail manufacturing
operations (VF.CC) is located in a residential area in Jersey City, New
Jersey (Figure 1). The plant fabricates and paints pails and barrels
with a normal daily production rate of 3,500 and 15,000 respectively.
Coatings are put on the products by VI.CC using paint spray, lacquer spray
and lithograph roller booths. The lithograph and part of the pail lines
are vented to two separate exhaust incinerators. The VLCC facility is
more than 100 years old and is currently updating equipment to comply
with NJ VOC codes. Odors resulting from the facility can be detected as
far as 2 km from the manufacturing site. Hudson Regional Health
Commission (HRHC) has attributed typical irritation reactions (eye
tearing, and headaches) in the residents living adjacent tu the site and
in children attending a nearby grade school to local odors. According to
the records of the HCR11C the paint products utilized by VLCC contain at
least the following solvents: acetone, methylethylketone,
methylisobutylketone, butanol, ethanol, isopropanol, butylacetate,
ektasolve, xylenes and toluene.
Sampling Design - All sampling Look place during November 1985.
Four permanent sampling sites were located at approximately 90° apart as
indicated in Figure 1. All samples collected at these sites were for 4
hr. in duration and nine days of samples were collected simultaneously at
each site. Site //5 was located within the school building. Short term
(l'-S hr.) and grab samples (15 min.) were collected on Lhe same days as
the fixed site samples to try to characterize transient, peak
concentrations. A total of 11 grab and 6 short term samples were
collected during this study. A meteorological station (wind speed and
352
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direction, temperature) was installed on the roof (2nd story) of the
church adjacent to VLCC.
Sample Collection and Analysis - Fixed site samples (4 hr.) were
collected at a flow rate of 60 ml/min with Nutech-221-IMC air pumps
equipped with 1,1 gm Tenax-GC (60/80 mesh) loaded glass cartridges. Grab
samples (15 rain.) were collected at a flow rate (1 I./mln) utilizing
identical cartridges as described above, but with DuPont-Alphs-1 personal
monitoring pumps. Short term samples (lj hr.) were collected at a flow
of (200 ml/rain) with the DuPont-Alpha-1 pumps.
All analyzes occurred in the MMU equipped with a Hewlett-Packard
5995 GC/MS. The MMU has been previously described by Haggert and Harkov
(1985). Prior to thermal desorptions four internal standards were added
to the cartridges (bromodichloromethane, l-chloro-2-broinopropane,
4-bromofluoro- benzene, and 1,4- dichlorobutane). The Tenax-GC
cartridges were then thermally desorbed at 225°C with a 25 ml/min He flow
into a cryofocusing trap maintained at -148°C. The sample was heated,
then injected onto a 60/80 mesh carbopack-B, 0.1% SP-1000 glass column
(2.4M x 1/8" ID). Oven temperatures began at 40°C and were raised to
236#C at 140C/niin. The mass spectrometer scanned 35-320 amu. All
cartridges were analyzed within 72 hours of sampling. Statistical
analyses were carried out utilizing Statgraphics (STSC 1981).
Quality Assurance/Quality Control - During the course of this study
a number of qa/qc steps were carried out. These procedures included the
use of Internal standards, calibration curves, field blanks, laboratory
blanks, and tandem and duplicate cartridges. Prior to sampling, thermal
flexing of the Tenax-GC resin was accomplished for all cartridges
utilizing a triplicate 2 hour heating/cooling cycle followed by thermal
desorption (Nutech 340-14). Precision estimates based on analysis of
compounds on 5 duplicate cartridges were approximately ±24,3% at the 95%
confidence interval. The minimum detection limits (MDI,) were set at
approximately three times the signal to noise ratio, while the minimum
quantitation limits (MQI,) were set at 2.5 times MDL. The MDL's varied
from 0.07 ppbv (25°C, 760 mm) for toluene and ethylbenzene to 0.64 ppbv
for ethanol. It should be noted that according to the Brown and Purnell
(1979) report breakthrough was probably significant for acetone, ethanol
and isopropanol. Breakthrough for these substances is estimated using
tandem cartridges (N»4) to be on the order of 30%. Tt is thus reasonable
to conclude that the levels for these three compounds are underestimated
in this study.
Results - The monitoring information is presented on a site and
upwind/downwind bases in Tables 1 and 2. Concentrations of
perchloroethylene (perc) were also included in this study as an example
of a ubiquitous urban V0C which was not utilized by VLCC. The highest
VOC levels were generally recorded in grab samples, while location #2 had
the most significant concentrations of the four fixed sites. Most VOC
levels in the school were 50% or less than the nearby fixed site (#3)
when ambient levels were significant (5-10 fold increase) as compared to
periods when the plant impacts were small. Thus indoor/outdoor (I/O)
ratios were nearly 1 during non-impact periods. However, the same
compounds were identified in all samples within the school and In the
adjacent communities. Downward samples were significantly elevated over
upwind samples, particularly for ethanol, acetone, methyl ethyl ketone,
ethylbenzene, and xylenes. The highest individual fixed site and short
term samples are shown in Table 1.
353
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Pairwise correlations (Table 3) indicate that most of the solvents
thought to result from VLCC emissions are highly correlated (R _ 0.70),
while none are related to perc. Factor analysis was carried out to
identify those parameters which can explain the ambient data set and this
effort resulted in a five-factor model (Table 4).
Discussion - Virtually all of the solvents reportedly utilized by
VI.CC and measured in the ambient air adjacent to the facility are known
for their acute toxicity (Sax 1983). Levels of the twelve solvents
measured during the present study were significantly below reported odor
thresholds, although individual samples had total solvent concentrations
above the odor thresholds of specific materials such as ui-xylene (270
ppb ) and isopropanol (130 ppb ). Generally concentrations for selected
VOC in grab samples were greater than fixed site samples, but were not
more than 2 times the levels found at fixed sites. In spite of the
levels of selected solvents found during this study, field personnel from
the MMU experienced typical irritant responses when strong odors were
detected off site, and near the plant boundaries. Because unknown
organic compounds were not the focus of this study, It is uncertain
whether high levels of other odorous materials were being emitted from
VLCC. This issue is of particular concern for lightweight organics that
are poorly trapped by tVie Tenax-GC adsorbent utilized in the present
effort.
Many of the pollutants measured in the current study have been
quantified in ambient air in urban portions of New Jersey. Levels of
alkylbenzenes and perchloroethylene in the urban atmosphere of New Jersey
have been recently reported (Harkov et al 1983, Harkov et al 1984). Both
methylethylketone and methylisobutylketone were measured at a number of
urban New Jersey sites during 1979, but were generally found at
concentrations less than 0.01 ppbv (Harkov et al 1981). Utilizing ATEOS
data as a comparison, significant increases over background VOC levels
resulting from the facility were considered when Vl.CC/Newark ratios
exceeded a factor of 3, which was the case for ethylbenzene and xylenes,
but not for toluene and perc (Table 5). A comparison of upwind/downwind
concentrations indicates that VLCC had significant impacts on localized
air quality for ethanol, ektasolve, acetone, methylethylketone,
ethylbenzene, xylenes and isopropanol when using a three-fold increase
over background as the basis for this conclusion (Table 2). The failure
to detect impacts on butylacetate and toluene levels from VLCC is
probably a reflection of the lower level of use of these substances at
this facility and the high background concentration of toluene in urban
air. It should be noted that because of the high population and
industrial density, it was expected that VOC levels in Jersey City would
be slightly higher than in Newark and also that the shorter sampling
times utilized in the present study would tend to produce somewhat higher
levels than the 24 hour Newark samples.
The pairwise correlation matrix indicates that those substances
utilized by VLCC were highly correlated, but not with perc which was not
a solvent utilized at this facility (Table 4). While the pollutant
levels for those substances were moderately correlated (R ¦» 0.50) with
position of sample collection (upwind/downwind), there was no such
relationship for perc. This result is consistent with the observation
that perc is a ubiquitous urban contaminant, but that VLCC is impacting
localized air quality for a select group of solvents utilized in its
internal processes.
354
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Factor analysis was carried out to Identify those issues which have
the most impact on the correlation between the variables in the data set.
Ideally, factor analysis should be carried out on large (_75 obs) data
sets (Lioy et al, 1985) and the 57 observations from the current effort
are great enough to draw some preliminary conclusions. A five factor
model (Table 5) which explained about 94% of the variance in the model
was produced from this data set. The first factor includes acetone,
ethylbenzene, xylenes, isopropanol and butanol and is most likely related
to a specific spray coating operation and the solvents associated with
this process within VLCC. Hie second factor had high loadings of
methylethylketone, methyllsobutyl- ketone, and ektasolve, which are the
main solvents utilized in the roller operations at VLCC. Both toluene
and butylacetate were highly loaded on factor three which is probably
related to the influence of background levels. Factor four has high
loadings of perc and location which is indicative of the relative
distance of the fixed and grab sites to the nearest dry cleaning
operations on Fowler and Danforth Avenues. Finally, the fifth factor is
related to upwind/downwind positions and was important for influencing
the recorded concentrations.
By utilizing perc as a marker for ubiquitous urban VOC contaminants,
it can be shown that VLCC clearly had an impact on localized air quality
in this portion of Jersey City (Figures 2 and 3). The levels of perc
near VLCC were: a) typical of urban concentrations (Singh et al 1981,
1982), b) not effected by wind direction, c) poorly correlated with the
other VOC measures, and c) location of sample collection was the only
variable in the data set which could partially explain the measured perc
trends. The results for the ketones, alkylbenzenes and alcohols are
directly opposed to those of perc and demonstrate that VLCC has a
measurable impact on localized air quality.
As a final comment it is unclear whether the sample collection
period of November 1985 corresponded with typical operations at VLCC.
The plant personnel were aware of the presence of a sampling crew in the
vicinity of the facility. Also, the HCRHC claimed that the odors were
relatively mild during the present study compared to other periods during
the past few years. For lack of better information, the data presented
here in this report should be considered representative of off-site VOC
impacts near VLCC.
Conclusions - Ambient VOC data was collected to document the impact
of emissions from a steel barrel and pail manufacturing facility on
localized air quality in Jersey City, New Jersey. This facility was
shown to cause increases in selected VOC from 3 to 30 fold over
background levels. These solvents corresponded to those utilized during
coating operations at this facility. In spite of demonstrating the
Impact of this facility on localized air quality, odor thresholds
reported in the literature for individual compounds were not exceeded in
any samples. Whether other materials that were not measured during this
study contribute to the localized odor and irritant problem is not known.
However, these data indicate that for short periods of time total solvent
concentrations can exceed odor thresholds for specific compounds.
Acknowledgements - The authors would like to thank the Hudson County
Regional Health Commission, particularly Mr. John Demjanick and Mr. Gary
Garetano, for assistance during this study. A special thanks to all the
local citizens who provided site access for sample collection during this
effort.
355
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Literature Cited
1. Brown, R.H. and C.J. Purnell 1979. Collection and analysis of trace
organic vapor pollutants in ambient atmospheres. J. Chrom.
I 78: 79-90
2. Fay, B.A. and C.E. Billings 1980. Index of signs and symptoms of
industrial diseases. USOHEW - NIOSH Pub.
3. Haggert, B. and R. Harkov 1985. Design and implementation of a
mobile monitoring unit (MMU) to measure ambient volatile organic
compounds. In, Proceedings of 77th Annual APCA meeting, San
Francisco, Ca. #84-17.2
4. Harkov, R. et al. 1986. Volatile organic compounds in the ambient
air near a large, regional sewage treatment plant in New Jersey,
submitted to JAPCA
5. Harkov, R. et al. 1985. Monitoring volatile organic compounds at
hazardous and sanitary landfills in New Jersey. J. Env. Sci. Health
20:491-501
6. Harkov, R. et al. 1984. Comparison of selected volatile organic
compounds during the summer and winter at urban sites In New Jersey.
ST0TF.N 38:259-274
7. Harkov, R. et al . 1983. Measurement of selected volatile organic
compounds at three locations in New Jersey during the summer season.
JAPCA 33:1177-1183
8. Harkov, R. et al. 1981. Toxic and carcinogenic air pollutants In
New Jersey - Volatile organic substances. In, Proceedings toxic air
contaminant, MASAPCA, Niagara Falls, NY
9. Key, M.M. et al. 1977 . Occupational Disease: A guide to their
recognition. USDHEW, DHS-N10SH Pub. No. 77-181
10. Lioy, P.J. et al . 1985. Receptor model technical series VI: A
Guide to the use of factor analysis and multiple regression (FA/MR)
techniques in source apportionment. USEPA Contract #4D2975NASA.
100 pp.
11. NAS 1977. Ozone and other photochemical oxidants. National Academy
of Science, Washington, D.C. 719 pp.
12. Pellizzari, E.D. 1982. Analysis for organic vapor emissions near
industrial and chemical waste disposal sites. Env. Sci. Tech.
16:781-785
13. Sax, N.I. 1983. Dangerous properties of industrial materials. Van
Nostrand Reinhold Corp., NY, NY, 1135 pp.
14. Sexton, K. and H. Westberg 1980. Ambient hydrocarbon and ozone
measurements downwind of a large automotive painting plant. Env.
Sci. Tech. 14:329-332
356
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15. Singh, H.B. et al. 1982. Distribution of selected gaseous organic
mutagens and suspect carcinogens in ambient air. Env. Sci. Tech.
16:527-528
16. Singh, H.B. et al. 1981. Measurement of some potable hazardous
organic chemicals in urban environment. Atmos. Env. 15:601-612
17. STSC 1981. STATGRAPH1CS. Version 1.1. STSC, Rockville, MD.
18. Vanl.angenhove, H.R. et al 1982. Gas chromatography/ma9s
spectrometry identification of organic volatiles contributing to
rendering odors. Env. Sci. Tech. 16:883-886
19. Verscheuren, K. 1983, Handbook of environmental data on organic
chemicals. 2nd edition. Van Nostrand Reinhold, NY, NY, 1310 pp.
357
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Table 1
- Concentrations of Selected VOC
near VLCC by site
(ppb X+STD)
V 9
c
Max. Peak
4/hr Grab
POLLUTANT 1 2 3 4 5 6 Sample Sample
u
Ul
ethanol
15.2119.1
10.318.0
4.414.4
10. U20.8
4.714.3
25.3127.6
60.7
NR
isopropanol
9.517.7
18.9+15.B
9.9+8.1
10.9+14.6
11.617.5
33.9138.3
45.6
110.0
butanol
10.5+11.0
15.4111 .3
7.3+6.2
10.3111.4
5.9+3.0
24.6119.1
37.3
62.8
acetone
9.3+11.4
14.8110.3
5.5+5.4
9.2+13.4
5." 9
38.6151.2
45.2
191.2
methylethy 1—
10.9+14.2
9.515.9
5.415.6
5.7+10.2
4. .0
29.4123.0
33.7
90.4
ketone
raethylisobuty1-
1.3+1.4
1.4+0.6
1.410.7
1.1+1.5
0.814.0
3.212
4.5
6.8
ketone
butvlacetate
1.4.+1.1
1.71.08
1.410.6
2.612.1
0.810.2
1.2+1.2
4.8
6.4
ektasolve
2.7l4 . 7
2.211.9
1.212.8
1.713.8
1.5+2.1
8.817.7
13.3
26.7
toluene
8.1±7 . 6
8.714.7
5.3+2.9
5.5+4.4
5.711 .8
12.4+6.6
21.8
24.1
ethylbenzene
6.2+7.7
7.2+6.6
4.014 . 7
2.9+4.9
2. 112.0
10. 118. 1
16.7
33.1
tn-xy lene
10.9117.4
12.0116.0
3.818.0
5.7113.8
4.815.1
31.1124.2
42.5
89.5
o&p-xylene
9.4112.2
9.8116.8
4.916.5
4. H8.9
3.212.7
18.0+12.8
27.5
48.3
perchloro-
0.81.07
0.91.08
1.01.0.8
1.111.4
0.910.5
0.710.9
4.5
2.6
ettaylene
N
11
10
10
9
6
11
DESCRIPTION
Danforth
Greenville
Lembeck
Sullivan
School
Grab
Ave.
Ave.
Dr.
Dr.
(indoor)
a- Ektasolve = ethyleneglycol monoprcpylethei
b- NR = Offscale
c- Max. = highest value in AO samples
d— N = includes duplicates
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Table 2
- Comparison of Upwind and Downwind Concentrations
at VLCC.
(ppb XiSTD)
V t
UPWIND DOWNWIND KATTO (D/U)
ethanol 1.7+3. 23.0+23.4 13.5
acetone 4.9+4. 28.1+35.6 5.7
jnethyathylketone 2.7+2.5 23.0+18.0 8,5
inethyisobutylketone 0.9+.07 2.5+1.7 2.8
butylacetate 2.0+2.8 1.8+1.0 0.9
ektasolve 0.2±0,4 6,7+6.1 33.5
ethylbenzene 0,6+1.0 10.0+6.7 16,7
toluene 5.1+2.9 11.9+6.3 2.3
m-xylene 0.9+0.9 26.0i20.4 28.9
o,p-xylene 0.9±1.0 16.3111.5 18.1
butanol 6.5±5.3 22.1+15.2 3.4
isopropanol 6.0i7.0 26.7+27.7 4.5
perchloroethylcne 0.9+0.8 0.8±0.7 0.9
N 13 25
Table 3 - Palrwlse Correlations for Selected VOC
at VI.CC
ETOH ACE MEK
ETBZ
KXYL
PROP
PERC
T.OC
POS
ET0I13
1 0.84 0.71
0.77
0.80
0.54
-0.18
-0.29
0.39
ACE
I 0.84
0.82
o
00
0.73
-0.29
-0.31
0.47
MEK
I
0.65
0.69
0.34
-0.2B
-0.34
0.48
ETBZ
1
0.99
0.70
-0,42
-0.39
0.58
MXYL
I
0.71
-0.38
-0.36
0.61
PROP
I
-0.05
-0.11
0.39
PKRC
1
0.60
-0.22
LOC
1
0.06
l'OS
1
a- ETOH
- Ethanol
ACE
- Acetone
MEK
- Methy 1ethy 1ketone
ETBZ
- Ethylbenzene
PROP
- Isopropanol
PERF.
- Perchloroethylene
LOC
- Location
P0S
- Position
359
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Table 4 - Final Factor Analysis Solution
for VOC from VLCC3
Factor Loadings
Factor 1 Factor 2 Factor J Factor 4 Factor 5
ETOH 0.60
ACE 0.75
MEK (1.79
MIBK 0.97
BUTACE 0.89
ETB7. 0.76
T0L 0.71
MXYL 0.76
OPXYL 0.7 7
PROP 0.97
BUT 0.87
PERC 0.91
F.KTA 0.H4
POS 0.86
1.0C 0.82
a- Principal Factor Analysis (PFA)
utilizing listwise deletion and
b- Factor loadings greater than ur
was conducted on Stagraphics (1981)
varlmax rotation.
equal to 0.60 are shown.
Table 5 - Comparision of Selected VOC Levels at VLCC
and Newark (ppb^)
Newark - Winter 1982
Ratios (VLCC/Newark)
perchlnroethy1ene 0.46
ethylbenzene 0.51
o,m,p-xy1enee 2.21
toluene 4.93
1 .8
12.4
10.9
L.4
a- From - Harkov et al (1984)
b- o,m,p-xylenes are combined due to the different isomeric
separations on packed and capilliary columns utilized in
both studies
360
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Figure 1.
Sampling Sites Around VLCC
Jersey City, New Jersey
'//////////
Avenue
///////////•
Linden Ave.
I oGraenvllte Ave.
rW,
Drive
Lemoeck
•'////// '//////
•y/z/w/z/w
t/f/fi.'fU/f
Stan Rd.
- Key;
> tfitiff
' uJ///////////
VLCC building
"// Residential
— Property line
~ Site
' • Incinerator stack
361
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Figure 2
Upwind concentrations treads for m-xylene and
perchloroethylene.
Plot of perc & mxylene vs sample #
(upwind position)
"" 1 1 1 1
1 1 1 1
1111
I " ! 1 1
¦ r i i i
-
-
pare j
\ ! \
\ ' '
mxylene
-
Y\
\\
l\ I V
V r^J. . A. ./ X
-
¦ VL ;x-
\ / * '—• \
f- • V / -v ' - •
\ / • ' V
f 1 1 ! 1 1 ! 1 I* 1 1 1 ! ! 1 1 I 1" ! '
n1! i i
0 3 6 9 12 15
sample # (upwind position)
-------
Downwind concentrations trends for o-xylene and
perchloethylene.
Plot of perc & mxylene vs sample #
(downwind position)
64.4
mxylene
>
_~
CL
Q-
w
en
c
Ql
1
X
X
E
o<3
U
L
Ql
o
perc
20
25
lG
15
Li
sample # (downwind position)
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IMPLEMENTING A QUALITY ASSURANCE PROGRAM FOR SAMPLING AND ANALYSIS OF
AMBIENT AIR TOXICS COMPOUNDS
Will 1 am E. Oslund
Aerometric Data Division
State of California, Air
Sacramento, California
Resources Board
The California statewide ambient toxic air monitoring program was
established to obtain ambient toxic data for selected compounds. The
toxic air monitoring network consists of 20 sites statewide with ambient
samples taken on selected days. Samples are collected in Tedlar bags, by
filtration, and with solid sorbent tubes. The bags are analyzed for
aromatic and halogenated hydrocarbons, the filters for heavy metals and
the tubes for various organics, e.g., pesticides.
In developing and implementing the statewide ambient toxic quality
assurance program, emphasis was placed on a cooperative approach between
the participating sampling, laboratory and quality assurance staff. The
staff believes that this is the best way to obtain prompt, coordinated
action on a multiplicity of quality assurance elements, namely:
developing an overall project outline, selecting specific workplan items,
documenting laboratory quality control procedures, encouraging
Interlaboratory activities, and conducting performance tests.
Of particular interest are the results of the performance tests. In this
activity the laboratories are challenged with ppb-levels of benzene and
halogenated hydrocarbons. The results of performance tests at four
laboratories are presented.
Progress towards developing and certifying low ppb-level working
standards for laboratory use, the start of a control sample program and
the development of new instruments are also reported.
364
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IMPLEMENTING A QUALITY ASSURANCE PROGRAM
FOR SAMPLING AND ANALYSIS OF AMBIENT AIR TOXIC COMPOUNDS
Introduction
The California Air Resources Board (ARB) is required by state
legislation to identify and then control toxic air contaminants J The
contaminants identified to date and those currently in the identification
process are presented in Table I.
As part of the ARB's overall control program, the staff has
established an ambient air monitoring network to provide the data
necessary to characterize population exposure to toxic contaminants and
monitor trends. The network currently consists of 20 sites located
throughout California.2 Each site is located at an existing state or
local criteria pollutant air monitoring station which is configured in
accordance with siting procedures outlined in the Code of Federal
Regulations, Title 40, Part 58, Appendices D and E for manual sampling
methods. Two samples per month are collected at each site. Volatile
organic ambient air samples are collected in 30-liter Tedlar bags over an
integrated 24-hour period with samplers specially designed by the Board's
staff to minimize sample degradation problems. Once the sample is
collected, the Teldar bag is shipped via courier to the appropriate
laboratory. The analysis is completed within 24 hours of the sampling
end time. The laboratory staffs are using gas chromatographic procedures
for quantitating and gas chromatograph/mass spectrometry procedures for
confirming the amount and identity of the volatile organic compounds.
An interim quality assurance plan has been prepared and partially
implemented to help ensure and document the reliability of the airborne
toxic contaminant data collected from the ambient network. A major goal
is to avoid some of the historical problems.3»4 The plan includes the
essential elements that are usually considered by any group conducting
ambient air monitoring for regulatory purposes.5 The implementation to
date is focused on:
- assessing the current state of analytical capabilities within the
four laboratories reporting or planning to report ambient toxics
data within California,
- documenting possible analytical variability associated with the
respective analysis of known standards, and
- developing a framework within which the quality control and quality
assessment functions can cooperatively and successfully operate.
The full implementation of the plan will lead to the establishment of
a quality assurance program for the assessment of all the data submitted
for regulatory use. An overview of our quality assurance structure is
shown in Figure 1. As indicated, the term quality assurance Is used as
the overall term. Quality control includes field, laboratory and data
activities. Quality assessment includes performance check and audit
activities.
The variety of activities implied 1n Figure 1 are usually assigned to
different staff sections within a given management division. Since more
than four interagency divisions are involved in this program, the
365
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coordination aspects alone are somewhat complex. In view of the newness
of the program, technical measurement problems at ppb-ppt concentrations,
lack of low-concentration gas standards, etc., the reader may foresee the
selective nature of the first-year effort, all of which is not reported
here.
This report is about the start of a program and the implementation of
selected initial elements aimed at producing precise and accurate data
for the regulatory process.
Performance Check Program
One key element (Figure 1) selected for action was performance
checks. The performance check activity was started in the fall of 1984
and continued into 1986. The program was designed to allow the
laboratory staffs an opportunity to challenge their analytical
instruments with the reference gases and concentrations shown in Tables
11-IV. The data in Tables II and III Illustrate the challenges that were
made possible by the availability of cylinders of compressed gas
containing ppb-concentrat1ons of various toxic substances from the
Environmental Protection Agency's (EPA) Environmental Monitoring Systems
Laboratory (EMSL) and the Research Triangle Institute (RTI). The
challenges illustrated in Table IV were based on ARB compressed gas
cylinders certified by the National Bureau of Standards (NBS). The
cylinders were systematically made available to the two ARB laboratories
already engaged in ambient sampling and analysis of toxic substances in
the ambient air and to two regional district laboratories. The program
was aimed at these four air pollution control laboratories because they
were involved in or about to be involved in analyzing ambient air
concentrations of toxic substances. The two district laboratories are
those operated by the South Coast Air Quality Management District and the
Bay Area Air Quality Management District. The two ARB laboratories are
those operated by the Haagen-Smit Laboratory Division and the Aerometric
Data Division.
The specific objectives of the performance check element include;
- developing protocol on a cooperative basis that would also serve as
a guide for the conduct of future audits,
- providing the laboratories with a systematic measure of their
analytical capabilities based on their analysis of high quality,
relatively low concentration compressed gas mixtures with an
assigned concentration,
- providing a baseline of the analytical capabilities at an early
stage in the program against which to measure future progress, and
- providing a vehicle to encourage realistic interagency working
arrangements between the individual laboratory quality control
staffs, the central quality assurance staff and the appropriate
staffs of EMSL, RTI, and NBS.
The results of three "low" concentration checks are presented in
Table II. The data indicate that 80% of the determinations were
generally within +2 ppb of the assigned reference value. The results of
two "high" concentration checks are presented in Table III. The fact
that only one laboratory analyzed for ethylene dibromide (EDB) and
ethylene dichlori'de (EDC) confirms the staffs stated lack of interest 1n
conducting checks at concentrations well above the range that the
366
-------
Instruments, procedures and staff are normally required to work. For
example, the mean ambient concentration for EDB is somewhat less than .01
ppb. Hence the challenge concentrations, 17 (Table II) and 196 ppb
(Table III) are approximately 2,000 and 20,000 times greater than the
mean ambient concentrations. The challenge concentrations and the mean
ambient concentrations are given for each compound 1n both tables. A
check in March 1986 using an EPA cylinder showed the average check vs
assigned concentrations to be 10 vs 9 ppb for EDC and EDB.
The results of the benzene performance checks, which were conducted
in 1985, are presented 1n Table IV. The five cylinders used in these
checks were manufactured by a commercial vendor to ARB specifications and
two of the cylinders were assayed by NBS. Assigned concentrations were
developed for two other cylinders by reference to the cylinders certified
by NBS. The average check vs assigned concentrations reported for the
four cylinders were in close agreement: 3.4 vs 3^4, 5.4 vs 4.9, 7.5 vs
7.6 and 8.9 vs £Lj^ ppb, respectively.
Control Sample Program
The control sample program was selected for implementation in early
1986. In this program we are trying to:
- provide an Immediate practical focus for developing precision and
accuracy data, and
- provide a framework for developing a coherent statewide data base
that will have direct and documented linkage to NBS standards.
As an initial step 1n documenting acceptable error levels in the
analysis of volatile organic compounds in ambient air, an EPA Group I
cylinder was provided to the participating laboratories. The protocol
calls for the laboratory staffs to analyze the control cylinder following
every tenth sample analysis. The protocol also calls for the submittal
of the plotted data within 60 days to the quality assurance staff in
normal Shewhart control chart format. In addition, the average of all
measurements and standard deviations are to be presented. The
laboratories are now participating in this program. The cylinder being
used contains low and known ppb concentrations of chloroform, benzene,
perchloroethylene, carbon tetrachloride and vinyl chloride.
Results
The air pollution control agency laboratories participated in the
performance check program, to varying degrees. As discussed above, there
was not much interest in conducting checks against high concentration
cylinders when daily demands called for determining some of the compound
concentrations at levels just above the limit of detection. Then, too,
there were a number of work crises associated with workload and new
procedure developments. Notwithstanding, it appears that the level of
participation in the overall program in October 1985 was nearly double
that of October 1984.
Laboratory participation is also reflected in the appointment of
laboratory quality control officers and development of documented quality
control procedures. Additionally, for example, the elements to be used
in the laboratory standard operation procedures (Appendix A) have been
defined.
367
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New Developments
Two new developments in the ambient air toxic program concern
standards and sampling instruments.
Most staff members involved in ambient monitoring for toxic
substances reached early agreement about the need for analytical gas
standards. Laboratory staffs have developed or purchased such standards
to the extent possible. Under ordinary circumstances, 1t is not a
quality assurance staff function to provide the laboratories with
analytical standards. However, since low-concentration NBS standards
for volatile organics were not yet available, it was decided that this
would initially be a staff function. From the overall quality assurance
view it appears most desirable to use NBS standards. Hence, we have had
considerable discussion with a number of NBS staff about its development
of such standards. In recent discussions^ it has become evident that
5 ppb NBS traceable standards in compressed gas cylinders may be
available later this year. At this time it appears that the cylinders
will contain about 30 ft^ mix of the following gases: benzene,
chloroform, carbon tetrachloride, trichloroethylene, perchloroethylene,
methylene chloride and 1,2-dichloroethane. The ARB staff has expressed
strong written support for the NBS program and its intention to purchase
standards as soon as NBS sets its specifications and prices.
Early in the monitoring program, the instrument staff developed and
built a prototype ambient air sample collection system for Tedlar bag
sampling over an integrated 24-hour period. Specifications were
subsequently prepared and a contract awarded to an instrument
manufacturer thereby providing commercial availability. This has worked
well for measuring a number of volatile organic compounds. However, as
more varied sampling requirements have appeared (e.g., pesticides and
aerosols) an additional approach to sampling has been taken. This
approach provides for efficient and reliable sampling at several
different flow rates using a multiplicity of independent sample
collection media (filters, sorbent tubes, etc.). As a result, the
performance requirements of an eight component toxics sampler have been
specified by the Instrument staff. It is now in the procurement phase.
Conclusions and Summary
The performance check program was Initiated 1n October 1984 and has
been successfully operated since then. Participation 1n the program has
more than doubled and accuracy has improved. The compressed gas
cylinders used have been provided by EMSL at Research Triangle Park,
North Carolina, through RTI. The protocol developed for the check
program will serve as a guide for future audits. Data obtained from the
checks provide an early baseline of analytical capabilities which can be
used to help measure future progress.
A control sample program has been initiated. When fully implemented
it should provide each laboratory with adequate and defensible
analytical precision data. The compressed gas cylinders used in these
initial control sample checks were provided by EMSL.
All the participants agreed that standards are a key part of a
successful program. The laboratory staffs have worked hard to obtain
and use improved gas standards, but readily available low-ppb NBS
368
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materials are still needed. Discussion with NBS indicate that traceable
standards at 5 ppb may be available later this year in 30 ft3
cylinders containing benzene, chloroform, carbon tetrachloride,
trichloroethylene, perchloroethylene, methylene chloride and
1,2-dichloroethane. We think NBS reference gases are vital to produce
accurate data.
ARB's instrument staff has developed sampling equipment which 1s
currently being used in the ambient air monitoring program.
Specifications have been developed to handle the more varied sampling
requirements for an increasing variety of toxic compounds. Purchase
orders for new multi-filter media instruments are in the procurement
phase.
In addition, the participants have cooperatively established
protocols, defined basic analytical methods, conducted interlaboratory
comparisons, appointed quality control officers, and documented quality
control procedures. The four laboratories are operated by two regional
and two state air pollution control agencies, namely:
- The South Coast Air Quality Management District, El Monte,
- The Bay Area Air Quality Management District, San Francisco,
- ARB Haagen-Smit Laboratory Division, El Monte, and
- ARB Aerometric Data Division, Sacramento.
Some of the essential elements of the program are in place and the
cooperative approach has worked well. The next elements we plan to
focus on include: providing NBS gas standards to all the laboratories
engaged in ambient sampling of toxics for control purposes, upgrading
the sampling network instrumentation, conducting audits, improving the
data screening process, developing and testing standard operating
procedures for a new group of contaminants, and completing more studies
on sample stability and contamination.
References
1. "Status Report to the Legislature on the Toxic Air Contaminants
Program," State of California, Air Resources Board, Sacramento, CA,
1985.
2. "State and Local Air Monitoring Network Plan," State of California,
Air Resources Board, Sacramento, CA, 1985.
3. "Air Quality: Do We Really Know What It Is?," U.S. General
Accounting Office, CED-79-84, 1979.
4. "Problems in Air Quality Monitoring System Affect Data Reliability,"
U.S. General Accounting Office, GAO/CED-82-101, 1982.
5. "Quality Assurance Handbook for Air Pollution Measurement Systems,"
Vol. I, Sections 1.3 and 1.4, U.S. Environmental Protection Agency,
E PA-600/9-76-005, 1984.
6. W. L. Zielinski, National Bureau of Standards, Washington, D.C.,
personal communications, 1986.
369
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Table I. Current status of compounds.
Identified and now In control process
Benzene
Ethylene dibromide
Ethylene dichloride
Hexavalent chromium
Asbestos
Now in identification
process
Dioxins
Inorganic arsenic
Carbon tetrachloride
Vinyl chloride
Ethylene oxide
Perchloroethylene
Cadmium
Methylene chloride
Table II. Statewide performance checks at low concentrations, two or
more laboratories; a) EPA assigned concentration, b) 1985 data,
c) data from one laboratory.
October 1985
Mean
Assigned3
Mean
Assigned
conc.
conc.
conc.
conc.
Compound
(ppb)
(ppb)
(ppb)
(ppb)
Chloroform
4
4
37
37
Benzene
11
12
18
20
Perchloroethyl ene
15
14
11
10
Carbon tetrachloride
17
15
11
10
Mean
ambient
conc. (ppb)
.08
2.8
.65
.14
January 1985 ,
Mean Assigned3 Mean
conc. conc. ambient
Compound (ppb) (ppb) conc. _(ppb)
Trichloroethylene 16 15 .38
Ethylene dichloride 23c 15 .06
Ethylene dibromide 19c 17 .01
Methyl chloroform 19 15 1.9
370
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Table III. Statewide performance checks at "high" concentrations, two
or more laboratories; a) EPA assigned concentration, b) 1985
data, c) data from one laboratory.
October 1984
Compound
Mean
conc.
(ppb)
Assigned3
conc.
(ppb)
Mean0
ambient
conc. (ppb)
Chioroform
157
129
.08
Benzene
162
146
2.8
Perchloroethylene
171
136
.65
Carbon tetrachloride
146
132
.14
January 1985
Compound
Mean
conc.
(ppb)
Assigned8
conc.
(ppb)
Mean''
ambient
conc. (ppb)
Trichloroethylene
184
145
.38
Ethylene dichloride
150C
157
.06
Ethylene dibromide
320°
196
.01
Table IV. Benzene performance checks, 1985; a) nominal concentrations
are as requested from vendor, b) assigned concentrations based
on standardization against NBS values, c) number "N" of
reported values.
Nomi nal
Conc.
(ppb)
Assigned
Conc.
(ppb)
NBS
NC
Mean
Conc.
(ppb)
Low
(ppb)
High
(ppb)
4
3.4
9
3.4
2.8
4.3
5
4.9
4.9
19
5.4
4.0
6.9
8
7.6
9
7.5
6.0
9.7
9
8.2
8.2
14
8.9
7.3
11.0
16
None
9
18.4
16.0
21.0
371
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QUALITY
ASSURANCE
j
Obtain NBS reference materials
I QUALITY CONTROL I I QUALITY ASSESSMENT |
I
I Field I
loperationsI
(Laboratory I
loperations|
I Data I
|documentation!
I Performance I
I checks I
Audits
Develop
sampling
equipment
Select
collection
media
Develop
si ti ng
cri teria
Develop
standards
Run
control
samples
Develop
quality
control
procedures
Screen
Process
Publish
Obtain cylinder,
schedule, conduct:
EPA Group I
EPA Group II
NBS benzene
Conduct
performance
Conduct
system
Document
sample
stab 11ity
Conduct
inter!ab
studies
Figure 1. Quality assurance for ambient air toxic substances monitoring
program.
372
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Appendix A. Elements to be included fn laboratory standard operating
procedures for air analysis.
I. Scope
A. Description of scope and limits of elements to be analyzed.
B. Documents and references upon which method is based.
C. Definitions of any special terms must be given.
II. Summary
A. General description of sampling and analytical procedure.
Enough Information should be included for an experienced analyst
to readily recognize the principles of operation.
III. Interferences and limitations
A. Comments made here should cover both analytical and sampling
problems, known and potential.
IV. Apparatus
A. Instrumentation: As specific a description as possible. Any
modifications or improvements of the basic system must have an
accompanying schematic.
B. Auxiliary apparatus: Give description of function and operating
conditions. Give description of sampling equipment if the
equipment Is specific to this method. For example, "Vacuum
pump, Acme Model 62, capable of maintaining a 1 CFM air flow at
10" vacuum.
V, Reagents and materials
A. Give a list of all reagents used and specify purity/grade.
B. Describe preparation of any special reagents for analysis and
sampli ng.
C. Specify composition, preparation, and concentrations of stock,
intermediate, and working standards.
D. Describe in detail any necessary safety precautions for handling
and disposition of chemicals.
VI. Procedures
A. Field sampling techniques
1. Refer to appropriate Field Sampling S.O.P. for exact
details of sampling, chain of custody and sample
identification procedures.
2. Describe equipment used and provide schematic.
3. List sampling conditions: materials, flow rates, etc.
4. Describe any potential problems and limitations, with means
of controlling such problems.
5. Give calculation methods for sample volumes, flow rates,
times, etc.
6. Describe any methods used to split samples for other types
of analyses, if necessary.
373
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B. Laboratory sample preparation/pretreatment techniques
1. Describe or refer to the appropriate section of the
Laboratory Quality Control Manual for a description of a
protocol for sample 1og-1n procedures, including document
control and sample examination for damage. Any possible
hazards due to toxic or f1ammable chemicals must be clearly
identified. Any sample storage requirements, such as
immediate refrigeration or protection for light must be
noted.
?. Describe any methods used for preconcentration, dilution
clean-up filtration, extraction, etc., after the sample is
received from the field.
C. Analysis
1. Describe as clearly as possible the exact instrument
configuration and set-up techniques. In the case of
chromatographic analysis, a special section should be
indented giving a concise, but complete list of columns,
flow rates, temperatures, detectors, amplifier ranges and
attenuations, sample volumes, etc.
2. Describe analysis blank and calibration procedure with
associated limits on precision and accuracy. Describe
analysis of control samples and limits of the resulting
data. Describe steps taken in an "out-of-control"
situation. Specify the format and location of recorded
calibration and control sample data.
3. Describe sample analysis. Description must include an
example of expected data (for example, a sample chromatogram
with all components of interest labeled).
4. Give calculation procedures for results. Describe data
recording and data submittal.
VII. Performance criteria
A. Describe frequency of duplicate analyses, spikes, field blanks,
and acceptable limits of each.
B. Describe frequency of multiple standard analyses to check method
linearity and detection limit.
C. If confirmatory method is used, refer to specific S.O.P.
VIII. Method sensitivity, precision, and accuracy
A. A table describing linearity (correlation coefficients),
accuracy (method bias), precision (standard deviations at all
levels analyzed), and detection limits (with method of
calculations) is necessary.
B. Data on sampling efficiencies, break through volumes, stability,
and desorption efficiencies must be included, if appropriate.
C. Data on storage stability and conditions for samples and
standards.
D. References to quality assurance information derived from
published and/or interlaboratory sources must be included, if
available.
374
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NMOC CONCENTRATIONS MEASURSO ,*1,011'
Laboratory for Atmospheric Research
Washington State University
Pullman, WA 99164
Bill Lonneman
Atmospheric Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Characterization of NMOC levels in transported air masses is currently of
interest in terms of oxidant production and the formation of acidic species
in the atmosphere. Instrumented aircraft have been used to obtain NMOC data
in background air masse? advected into several urban areas in the
United States. Measurements were made during the morning hours ir» the layer
above the surface inversion ("1000 l"t.) niul below the usual afternoon mixing
height <~h 000 ft.). Special emphasis was placed on isie:;;? ureir<;nt of Individual
hydrocarbon and carbonyl compounds.
Mean hydrocarbon concentrations for the various cities ranged from about 10
to 50 ppbC with individual samples varying from less than 5 to appropriately
90 ppbC. Aldehydes generally contributed less than l()% of the total NMOC
measured. There do not appear to be any strong correlations between NMOC
levels aloft and other chemical and physical parameters.
375
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NMOC CONCENTRATIONS MEASURED ALOFT
Introduct ion
Nonmethane hydrocarbon concentrations in the layer above a morning
surface inversion and below tlie afternoon mixing level are of interest
because oxidant precursors in this layer mix with urban plumes following
breakup of the surface inversion. Most photochemical models that are
designed for regulatory purposes incorporate oxidant precursors from aloft.
Recent modelling studies have indicated that control, requirements are quite
sensitive to the nonmethane hydrocarbon input from aloft.' Therefore, it is
important that hydrocarbon concentrations in this layer be defined.
Hydrocarbon concentrations aloft have been determined in several
oxidant field study programs. While in most of these special studies hydro-
carbon samples were collected primarily in urban plumes, there were always
home samples obtained above the surface inversion during the morning hours.
During the summer of 1985, a field measurement program was initiated with
the primary objective being to define NMOC levels transported into urban
areas from aloft during the morning hours. Studies were conducted In the
vicinity of Dallas, Houston, Tulsa, Atlanta and Birmingham. In this paper
we will summarize the types and concentrations of organic species measured
aloft. Relationships between the organlcs and other pollutant and meteoro-
logical parameters will be described as well.
Data Sources
The nonmethane hydrocarbon data utilized herein were obtained in
airborne sampling programs conducted during the period from 1978 through
1985. Table T provides a listing of the cities near which airborne hydro-
carbon measurements have been made. This table also indicates which
research organizations collected and analyzed the samples. Washington State
University, Brookhaven National Laboratory, Hat telle Columbus Laboratories,
Battelle Pacific Northwest Laboratories and EPA-Las Vegas, each participated
in one or more of the sampling programs. Samples for NMOC analysis were
collected in rigid metal containers. The sampling period in each locality
coincided with the oxidant season in that region.
Sample Selection
Since the objective of this work was to characterize nonmethane hydro-
carbon concentrations in the layer above a morning surface irvnrsion and
below the usual afternoon mixing level, sample selection criteria was based
primarily on collection tino and altitude. All samples that were collected
during the morning hours before 10 am at altitudes between 1000 ft and 5000 ft
above the surface were considered acceptable in the initially screening.
Following the selection of appropriate samples based on time and
altitude, the nonmethane hydrocarbon totals were visually examined for each
sample in all cities. When the total nonmethane concentration exceeded
60 ppbC, additional information was sought which could be used to verify
that the KHr.'.ple had been collected above the morning surface Inversion.
Ozone concentrations at the time of hydrocarbon sMinplo collection provided
a good indicator of mixing heights. A Few samples were removed from the
data base because hydrocarbon concentrations were abnormally high and ozone
levels were very low (<20 ppb). This condition was judged to be character-
istic of pollutant conditions in the surface layer below a low level
inversion. When available, temperature soundings were examined to verify
that samples were collected above the morning surface inversion.
376
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Hydrocarbon Sampling and Analysis
Only a brief summary of the hydrocarbon sampling and analysis
techniques will be provided here. Full details of the procedures utilized
by the various research groups can be found in the references listed in
Table I, Sample collection generally Involved transferring air from a
ram-alr manifold inside the aircraft to the collection container. Rigid
metal containers were filled to a positive pressure by inserting a pump
between the aircraft's inlet manifold and the metal canister. All
hydrocarbon concentration data reported herein were determined by gas
chromatographic methods which provided individual species identification.
The total hydrocarbon levels were then calculated by summing the concentra-
tions of the Individual species that were reported to be present. These
analyses were performed using gas chromatographs equipped with flame
ionization detectors. Each research group used a cryogenic step to
concentrate the organics, two or three column systems in order to obtain
adequate hydrocarbon resolution, and computerized data acquisition systems
for signal processing.
Results and Discussion
There were 97 samples identified in the field studies prior to 1985
that appeared to be. useful for characterizing NMHC levels aloft. This data
base included samples from Atlanta-]981, Baltimore-1980, Bnston-1980,
Houston-1978, Milwaukee-1981, New York-1980, Philadelpbla-1979 and
Washington, DC-1980. The mean NMHC concentration calculated for each of the
eight cities is listed in Table II. Average concentrations ranged from
21.6 ppbC aloft near Atlanta to 47.0 pphC in the vicinity of Baltimore, In
general, cities located in the northeast corridor between Washington, DC and
Kew York City exhibited higher average liydiocarbon levels aloft than cities
in other sections of the U.S. For example, the Washington, PC-Baltlmore-
l'hiladelphia-New York City average was 40.5 ppbC while the combined average
for Atlanta, Boston, Houston and Milwaukee was 25.8 ppbC.
The mean nonmethane hydrocarbon concentration for all cities combined
was 35.4 ppbC with a coefficient of variance of approximately 55%.
Paraffinic species were by far the major type of hydrocarbons present in
samples collected aloft. Saturated compounds comprised approximately 76% of
the identified hydrocarbons while the mean aromatic contribution was about
16% and the olefins averaged 8%. The mean paraffir con emit rat.ion for all
cities was 20.0 ppbC. The aromatic mean wan 4,3 ppbC and the olefin mean
equalled 1.8 ppbC. These data are suiwn r:I ? cd in Table I'll.
Hydrocarbon concentrations measured aloTt in the. vicinity of the eight
cities listed in Table II ranged from 10.0 to 89.6 ppbC. Since this
represents a difference of almost an order of magnitude, it was of Interest
to see if there were obvious correlations between hydrocarbon levels aloft
and other physical or chemical parameters. Tn a few specific cases it was
possible to examine the relationship between hydrocarbon levels aloft and
such factors as wind direction, emission input along back trajectories and
surface ozone readings. The Baltimore and New York areas were selected for
examining these types of correlations because the comprehensive data base
acquired during the 1980 NECRMP and NEKOS programs provided the necessary
meteorological and pollutant information.
Wind directions over the nine hour period prior to sample collection
weto determined for each sampling day in Baltimore and Kew York City. The
back trajectories were based on winds averaged over altitudes of 500 to
1500 in. Three hour intervals were utilized in plotting the back trajectories
377
-------
from each city. Figures I and 2 summarize the relationship between hydro-
carbon levels aloft and wind directions for Baltimore and New York,
respectively. As shown in the center of Figure 1, the mean nonmethane
hydrocarbon concentration for 21 samples collected over Baltimore was
47.0 ppbC. Fourteen of the 21 samples were collected with wind trajectories
originating in the northwest quadrant. The average hydrocarbon concentration
in these cases was 50 ppbC. When winds were out of the southwest quadrant,
the mean hydrocarbon level was 41 ppbC. This corresponds to less than a
20% difference which Js about the same as the accuracy of the hydrocarbon
measurement methodology. Therefore, it appears that hydrocarbon levels
aloft in the vicinity of Baltimore are essentially the same in air masses
transported into the region from the two westerly quadrants. Tn the
New York City area, there appears to be some dependence of hydrocarbon
levels on wind direction. As shown in Figure 2, when winds were out of the
southwest quadrant hydrocarbon levels aloft averaged 55 ppbC. This compares
to a mean hydrocarbon concentration of 36 ppbC when winds were from the
northwest. A logical explanation for this observation is that under a
southwesterly wind regime New York City is near the end of the highly
populated eastern corridor. Consequently, air masses advecced into the
New York City area from the southwest should be more polluted than those
entering from the northwest or moving onshore from the southeast.
Field studies during the summer of 1985 were designed specifically to
measure NMOC levels advected into urban areas from aloft during the early
morning hours. The aircraft flew arcs upwind of the urban area at two
different altitudes above the surface inversion but below the normal
afternoon mixing height. An attempt was made to expand the NMOC
measurements to include carbonyl compounds and PAN. The quality of the PAN
data is questionable so will not be discussed. Ctirbonyl compounds were
trapped by passing air through adsorbant cartridges impregnated with
dinitrophenylhydrazine, The hydrazones that formed were analyzed using
11P1.C. Table IV provides average NMHC and aldehyde concentrations measured
aloft over the five cities studied in 1985. Formaldehyde and acetaldehyde
levels in Houston, Atlanta and Birmingham were generally below the detection
limit of the analytical procedure, while in Dallas and Tulsa, these two
carbonyl compounds accounted for approximately 10% of the NMOC present.
A positive correlation was generally observed between NMHC and aldehyde
concentrations. For example, hydrocarbon levels aloft over Dal.lfu; on the
morning of July 6, 1985 fXi-:a>°cd 20 ppbC with a corresponding mean aldehyde
concentration of about 2 ppb. On July 14, Dallas NMHC levels were down to
about 2 ppbC and the aldehyde concentrations ranged from below the detection
limit ("0.1 pph) up to 0,7 ppb.
The 1985 studies made it possible to examine the variability in
hydrocarbon concentrations aloft during the morning hours since sampling
arcs were flown at different distances and altitudes upwind of the urban
area. Generally, one or more samples were collected along each of three
upwind arcs. Figure .1 graphically illustrates the daily variations in
hydrocarbon levels, observed in Houston. The solid circles in Figure 3
represent measured NMHC levels in individual samples. The vertical lines
connect maximum and minimum levels each clay. On most days, the high NMHC
measurement exceed the low value by at least a factor of two and on several
occasions by as much as a factor of ten. As can be seen in Figure 3, on
days when the NMHC concentration range was large, one sample exhibited a
much higher hydrocarbon level than the others. The reason for this
anomalous behavior is not immediately obvious. The high readings showed no
consistent correlation with altitude or distance from the city.
378
-------
Summary
Characterization of NMOC concentrations In transported air masses Is
currently of Interest because organic species are known to contribute to
oxidant formation. Tn addition, hydrocarbons anil their oxidation products
have been implicated in the production of acidic species in the. atmosphere.
Hydrocarbons can directly contribute to acidity through their conversion to
organic acids (e.g. formic acid) and/or indirectly by promoting the
conversion of S0„ to sulfate. The airborne measurements described herein
provide new knowledge concerning NMOC concentrations typically found in
background air masses.
Acknowledgments
Funds for this research work were furnished by the U.S. Environmental
Protection Agency, Research Triangle Park, NC and the Radian Corp.,
Austin, TX.
References
1. "Guidelines for using the carbon-bond mechanism in city-specific EKMA,"
EPA-450/4/84-005, Environmental Protection Agency, Research Triangle
Park, NC (1984).
2. H. Westberg, B. T.amb, "Ozone production and transport in the Atlanta,
GA region," Final Report for EPA Grant No. CR809?.?.! H984).
3. .1. H. Novak, "1980 northeast regional oxidant study (UEROS) data
compilation, meteorology and assessment division," Environmental
Sciences Research Laboratory, U.S. Environmental Protection Agency,
Research Triangle Park, NC 27711.
4. H. Westberg, L, MacGregor, "Nonmethane organic carbon concentrations In
air masses advected into urban areas in the United States," Data Report
for EPA Grant No. CR812208 (1986).
5. H. Westberg, K. Sexton, M. lloldren, "Measurement of ambient
hydrocarbons and oxidant transport - Houston 19/8," Final Report for
EPA Grant No. F.805343, Environmental Protection Agency, Research
Triangle Park, NC (1979) .
6. 11. Westberg, B. T.amb, "Milwaukee ozone study - 1981," Fi.r.s.l Report for
Contract No. NRA 98571, Wisconsin Department of Natural Resources,
Madison, WI. (198?).
7. H. Westberg, P. Sweany, "Philadelphia oxidant data enhancement study:
hydrocarbon analysis," Final Report for EPA Contract No. 68-02-3339,
Environmental Protection Agency, Research Triangle Park, NC (1980).
8. H. Westberg, L. MacGrogor, "Nonmethane organic carbon concentrations in
air masses advected into the Houston area," Final Report for Radian
Corp. Contract No 33913 (1986).
379
-------
TABLE I. AIRBORNE HYDROCARBON MONITORING PROGRAMS
City
Sample
Col l.ectier.
Sample
An.a I vsls
Sampling
Per loci
Ref erer.<
Atlanta
WSU
WSU
July 1981,
Aug.
1985
2,4
Baltimore
WSU/BNL
WSU
July-Aug.
1980
3
Birmingham
WSl!
WSU
Aug. 1985
3
Boston
BCL
BCL
July-Aug.
1980
3
Dallas
WSU
WSU
July 1985
4
Houston
WSU
WSU
Sept. 1978
, Aug.
, 1985
5,8
Ml lwauk.ee
WSU
WSU
Aug. 1981
6
New York
FNL
WSU
July-Aug.
1 980
3
Philadelphia
EPA-LV
WSU
.July-Aug.
1979
7
Tulsa
WSU
WSU
July 1985
4
Washington, DC
EPA-LV
WSU
July-Aug.
1980
3
WSU: Washington State University
BNL: IVtonkheven National Laboratory
BCL: Battelle Columbus Laboratories
PNL: Battelle Pacific Nor«:hwes.t Laboratories
EPA-LV: EPA-Lap Vegas (Northrup Services')
TABLE II. MEAN NMHC CONCENTRATIONS (ppbC)
MEASURED IN VARIOUS URBAN AREAS
PRIOR TO J 985
CITY ALOFT
ATLANTA
21.6
BALTIMORE
47.0
BOSTON
21.7
HOUSTON
32.7
MILWAUKEE
27.1
NEW YORK
44.5
PHILADELPHIA
23.3
WASHINGTON, DC
38.1
3B0
-------
TABLE 111. SUMMARY STATISTICS FOR HYDROCARBON DATA
COLLECTED ALOFT PRIOR TO 1985
Mean
Standard
Deviation
Coef f,
Variance
Min.
Value
Max.
Value
NMHC (ppbC)
35.4
19.4
54.9
10.0
89.6
Paraffin (ppbC)
20.0
12.3
61.6
3.5
73.0
76
13
17
28
96
Aromatic (ppbC)
4.3
4.2
98.5
0.3
28.5
m
16
10
64
3.6
60
Olefin (ppbc)
1.8
2.0
111
0
11.0
(%)
8.1
8.9
110
0
35
TABLE TV. MEAN NMOC CONCENTRATIONS
DETERMINED PURTNG 1985
FIELD STUDIES
CITY
NMHC
(ppbC)
FORM
(pph)
ACET
(ppb)
HOUSTON
DALLAS
TULSA
ATLANTA
BIRMINGHAM
20.0
17.6
34.6
24.9
10.6
<0.5
1 .7
3.5
<0.7
<0.7
<0.2
0.2
0.9
<0.3
<0.3
381
-------
49ppbC
(7)
51 ppbC
/ NMHC
/ 50ppbC
BALTIMORE
NMHC
470 ppbC
(21)
NMHC
41 ppbC
52ppbC
40ppbC
(6)
Figure 1. Diagram showing rel atton.sliip between hydrocarbon levels
measured aloft over Raltimore and wind direction.
382
-------
43ppbC
(6)
l7ppbC
(2)
52ppbC
(4)
N
1
/ NMHC
s 36ppbC
' (8)
NEW YORK
NMHC
445ppbC
(18)
\ NMHC
^ 55ppbC
\9)
\
5BppbC N
56ppbC
NMHC /
29ppbC'
(0 / -
/
/
/ ?^29ppbC
Figure 2. Diagran showing relatior.F.hip between hydrocarbon levels
measured aloft over New York City and ^Jrri direction.
383
-------
80
70
60
y 50
40
30
20
10
0
HOUSTON
JL
JL
JL
i
N r
-------
FIELD APPLICABILITY AND PRECESSION OF A WHOLE"AIR
SAMPLING METHOD FOR AMBIENT AIR VOLATILE ORGANIC
COMPOUND DETERMINATION
Dennis D. Lane
Associate Professor of Civil Engineering
University of Kansas
Lawrence, Kansas
i
Ray E. Carter, Jr., Glen A. Marotz,
University of Kansas
Lawrence, Kansas
\
J
ABSTRACT
Toxic substances can enter the atmosphere through continuous emission
at relatively low concentration levels. Character1zatIon of such emissions
is difficult. A method of sampling volatile organic compounds from a con-
tinuous point source using 3tainle33 steel spheres a3 whole-air samplers is
described. Laboratory analysis using cryogenic focusing and gas chromatog-
raphy allows assessment of the 3amples.
The method was tested at a gasoline loading station for a pipeline
company. Five of the spheres were located downwind of the source In the
plume centerline; one sampler was located upwind of the source to collect
background concentrations. The compounds chosen for analysis were isopen-
tane, n-pentane, n-hexane, benzene, isooctane, and n-heptane because of
their prevalence in the emissions from the source type. Concentrations of
selected compounds varied from 57.1 ppm to less than 0.01 ppm depending on
the compound itself, location of the sampler relative to the source, and
meteorological conditions.
At two downwind sample point3, co-lccated samplers were used to assess
the precision of the sampling system. Co-located sampler data showed dif-
ferences in compound concentrations ranging from 2.8 percent to 17.9
percent. Most variations, however, fell in the 5 percent to 10 percent
range.
Results showed that the stainless steel spheres performed well in the
field. In comparison with other available ambient air volatile organic
samplers, the system described in this 3tudy has many advantages, including
ease of operation, a wider range of applicability to various organic com-
pounds, and more versatility In actual field monitoring configurations.
385
-------
Field Applicability and precession of a Whole-Air Sampling Method for
Ambient Air Volatile Organic Compound Determination
BACKGROUND
Continuous, low level emission of volatile organic compounds may cause
chronic health effects to various parts of a population. These types of
emissions could be produced by certain industrial source classes.
Characterization of compounds present In such a situation Js difficult at
best, but the necessity for omission safeguards can only be Justified once
ambient air concentration levels are assessed. Unfortunately, no standard
procedure for doing so has been developed to date. In 19811, the U.S.
Environmental Protection Agency completed a report entitled "Compendium of
Methods for the Determination of Toxic Organic Compounds in Ambient Air"
(NTIS #EPA — 600/H — 8U—0141 ) . This document describes five techniques ap-
plicable to the monitoring of volatile organic compounds. All but one of
the methods (cryogenic trapping) are somewhat specific to a certain group of
volatile compounds.
Field testing of these possible methods is limited. The most extensive
work was performed by Riggins (EPA-6OO/I4-83-027), who collected field data
using the five methods and evaluated their applicability for use with
various volatile compounds, but this work was not Intended to compare the
relative performance of each method at a co-located site. Other data that
exist on the five methods discussed in the compendium document are Krost -
Tenax" GC (1982), Pelllzzari - Tenax" GC (1979), Kebbekus - Tenax^ GC,
D
molecular sieve (1982), Walling - Tenax GC, molecular sieve (1982), Holdren
- cryogenic (19 8 4) , Lewis - organochlorine pesticides (1982 and 1 980 ),
BJorkland - organochlorine pesticides (1970), and Grosjean - aldehydes and
ketones (1980).
The moat recent field study of hazardous organic chemicals in the
ambient atmosphere was done by Singh, et al. (1983). Concentrations of
forty-four organic chemicals (many were bacterial mutagens or suspected
carcinogens) were measured in ten USA cities over a nine to eleven day
period using a gas chromatograph-equ1pped mobile laboratory. Results
Indicate that average concentrations of the measured species ranged from 0-
20 ppb.
Of the five techniques developed to date, only the cryogenic trapping
and GC/FID or ECD analysis has more than narrow applicability. It Is
capable of detecting volatile, nonpolar organlcs having boiling points in
the range of -10 to +200°C. The major disadvantage to this technique is its
requirement for cryogenic gas chromatographic measurements in the field,
thereby permitting only single point concentration assessments of a volatile
compound from the suspected source; simultaneous mapping of the plume cannot
be done.
An alternative technique, or compatible add-on technique, is needed to
make the cryogenic trapping method more versatile. One approach is the
development of a secondary collection system capable of storage and
transportion of the sample(s) to a stationary cryogenic gas chromatograph.
In this study, such a procedure Is explored by collecting volatile organic
compounds from a bulk petroleum transfer facility near Topeka, KS using
stainless steel spheres. Five spheres were located downwind, and one up-
wind, of the source. At two of the downwind sampling points, co-located
samplers were used to check the precision of the system. The samples were
then transported to the laboratory for analysis on a cryogenic gas
chromatograph. Laboratory procedures for analyzing the samples were ba3ed
386
-------
on McClenny's work (Pleil, et. al. 19fliJ & Holden, et. al. 1985). General
laboratory use of cryofocusing gas chromatography is reviewed by Brettell
et. al. (1985) and Wampler et. al. (1985).
DESCRIPTION OF METHODS
Field Sampling
Stainless steel spheres (Demaray Scientific Instrument Ltd., Model
06^7, 6.0 liter) equipped with Whltey Microvalves were used to collect
volatile organic compounds emitted from a bulk gasoline transfer station
(Williams Pipeline Company, Wakarusa, Kansas). The collection spheres were
evacuated in the laboratory before placement in the field. To Insure that
no carryover of compounds between different tests occurred, the spheres were
evacuated to 60 microns of mercury vacuum using a Welch Duo Seal vacuum pump
(Model 1U02R); they were then flushed for three minutes and pressurized to
30 psi with hydrocarbon-free air supplied by Llnde Corporation (NBS
traceable). After the spheres had set for approximately one hour, they were
prepared for field sampling by evacuating to 60 microns of mercury vacuum
using the same pump. A Hastings vacuum gauge (Model DV-6) was used to
measure the 60 micron value.
The Whltey microvalves (Model SS-21RS2) were calibrated in the
laboratory using a certified bubble meter. During the calibration proce-
dure, the spheres were treated in the same manner as if they were being used
for field sampling. Microvalve settings were determined to allow a 100-105
mH/min initial flow rate.
Each of the spheres was transported to the field site for a sampling
run. They were attached to two-meter high fence posts which had been driven
at three arithmetically or geometrically-spaced sample points. At two
points, co-located samplers were installed to check the precision of the
sampling system. One sample was always located upwind of the source to
evaluate background levels of the selected volatile compounds. Before each
sampling period began, a hand level was used to ensure that the five
downwind samplers were at the same approximate height above the ground.
A portable meteorological station was monitored to provide an accurate
picture of wind speed, wind direction, relative humidity and atmospheric
temperature during each sample run. The temperature and windspeed were
taken at two and six meters above the ground. Wind direction and relative
humidity were also recorded at two meters above the ground. Data from the
meteorological station were used in aligning the downwind sample points on
the plume centerline which corresponded to the direction of the prevailing
wind (see Figure 1), and in determining atmospheric conditions for future
use in computer dispersion modeling.
Each cf the microvalve settings was checked for proper readings before
a test. The three downwind sample points were chosen 3uch that the sampler
locations were within ± 10° of the plume centerline at the initiation of a
test. This criterion was met using triangulatlon techniques as illustrated
in Figure 1. Values were adjusted until they matched the calculated values
corresponding to a direct centerline alignment, A subsequent check of
meteorological data suggested that we were successful in sampler location
using this approach.
After all the prestart steps had been rechecked, the main valves ad-
Joining pre-set microvalves on the spheres were opened and sample collection
began. In all cases, there was less than a one minute delay between the
first valve opening and the last based upon stopwatch observations.
387
-------
Prevailing Wind Direction
from Meteorological Station
Tan a = a/b
a is Known
x Distance is Measured
y Distance — y = (Tan a)x
Figure 1
N
Line Corresponding
to True North
/
/
/
Plume (£
r Downwind
Samplers
/
/
'oV
/
/
/
/
Transfer Station
* Upwind Samplers
Illustration of Sampler Placement
-------
William's Pipeline Co. allowed access to the on-site product flow computer
system to determine the amount of liquid product transferred during any
sample period.
At the end of the test, the main valve and mlcrovalves on each sphere
were closed, again within a one minute period. The sample collection
spheres were then removed from the field site and transported to the
laboratory for analysis.
The total setup time for a test (Including meteorological equipment)
using a two person crew was thirty-five minutes. If the meteorological
station was not deployed, samplers were In place In less than fifteen
minutes after reaching the site. Takedown time with the meteorological
equipment required twenty-five minutes. The six samplers without the
meteorological equipment could be removed from the site In less than fifteen
minutes. Total time for an actual sixty minute test averaged a little leas
than two total hours with meteorological equipment setup.
Laboratory Analysis
The samples were analyzed with a Nutech cryogenic sampling system and a
Hewlett-Packard 5880A gas chromatograph. A flame ionization detector was
used for all samples. A detailed description of the laboratory procedures
and gas chromatography variables is not presented here; the reader Is
referred to Holden et. al. (1985), Pllel et. al. (1984) and Tripp (1984).
A volume of approximately four liters was collected In each of the six-
liter spheres. The volume was determined using Figure 2. By plotting the
flowrate through the Whltey mlcrovalves versus time, a curve was generated
for each valve system (i.e., stainless steel sphere and Whitey microvalve).
Graphical Integration of the area under this curve yielded an approximate
volume collected for each microvalve of four liters. For example, for
microvalve number Jl;
Initial flowrate = ll'i.9 ml/mln.
Final flowrate - 29.9 ml/mln.
Elapsed time = 60 min.
114.9 ml/min. + 29.9 ml/min. ,n . .
x 50 mln, = 143314. ml
A vacuum was required to remove the samples from the spheres. To avoid
contamination of the samples, a metal bellows pump was chosen for this task.
The 28-minute sampling and analysis cycle allowed for a maximum of 18.5
minutes of sample collection per cycle. To ensure that only pure sample was
circulated through the cryogenic trap, the flow from the sampler to the
sampling manifold was maintained at a value higher than the 25 cc/raln flow
Into the cryogenic sampling system. If the flow was maintained in the 35-40
cc/mln range, samples could be drawn from the sampler for approximately 100
minutes, sufficient for four samples at 18.5 minutes of sample collection
each.
To maintain the flow from the sampler in the 35-,10 cc/min range, both a
Whitey microvalve and a mass flow controller were placed in the sampling
system between the metal bellows pump and the sampling manifold. The mas3
flow controller was set at 40 cc/mln, and the opening of the microvalve was
constantly monitored and adjusted to maintain a reading slightly less than
389
-------
100
90
60
c
'E
£ 40
Q)
«—¦
CO
L-
5
u.
20
¦ Microvalve #4
• Microvalve #2
a Microvalve #1
60
70
50
30 40
Time (min)
Figure 2 - Sampler Flowrate Versus Time For Whitey Microvalves
390
-------
40 cc/mln. Flow from the sampler was started by opening Its top valve
approximately 1.5 mlnute3 before the start of the sample collection period
of the first of four samples taken from each sampler. Flow was stopped by
closing the same valve at the end of the sample collection period. The same
procedure was used for the remaining samples, with the exception that the
flow was started only 30 seconds prior to the start of the sample collection
period.
Each time a change was made from one sampler to the next, the entire
sampling system was flushed with hydrocarbor.-free air. In most cases, the
first of the four analyses of each sample resulted in a slightly lower
concentration than the others. Thus, there Is not absolute confidence that
the 1.5 minutes of sample flow prior to the start of the sample collection
period Is sufficient to fill the lines and the sampling manifold with pure
sample. In order to achieve this confidence, either a higher flow rate must
be used, or the first sample should be discarded.
The gas chromatograph was calibrated using a mixture of gases provided
by Scott Specialty Gases,Inc. This mixture contains NBS-traceable con-
centrations of all of the desired compounds except n-heptane. In order to
obtain a known concentration of n-heptane, a portion of the pure compound
(in the liquid state) was placed In a diffusion tube, which provided a
constant release of vapor at constant temperature. The n-heptane was
released from the diffusion tube into a closed system, through which
hydrocarbon-free air wa3 passed at a known rate, which was controlled by a
mass flow controller. However, because the mass flow controller was found
to yield readings approximately 10$ lower than the actual flow (as measured
by a bubble flowmeter), a correction factor was introduced. Thl3 flow was
mixed with that from the cylinder containing the other five compounds (also
measured with a bubble flowmeter) and introduced Into the sampling manifold.
The diffusion rate of n-heptane was obtained by weighing the diffusion tube
several times, with about a week between each of the weighings. Knowing
this diffusion rate, the concentrations of the compounds in the calibration
mixture (as furnished by Scott), the flow through the diffusion system, and
the flow from the cylinder containing the calibration mixture, the exact
concentrations in the sampling manifold could be calculated.
A calibration method Involving the use of diffusion tubes for all the
analyzed compounds was also used during the course of the 3tudy.
Comparisons of the diffusion tube method and compressed calibration gases
indicate a maximum concentration difference between the two methods of seven
percent. Most of the concentration differences ranged from two percent to
four percent. Due to their high volatility rate In the 20-25°C range, the
diffusion rates of lsopentane and n-pentar.e are variable with slight tem-
perature changes. Therefore, a system capable of holding a constant
temperature (± 0.5°C) several degrees below room temperature (I.e. 10°C) is
necessary.
The performance of the ga3 chromatograph used In this 3tudy is limited
to concentrations above 0.01 ppm for the compounds under consideration and
the type of laboratory protocol followed during the analysis phase.
Characteristics of the gas chromatograph and manufacturer's specifications
indicated that the instrument was capable cf parts per billion determination
of volatiles with a ±5 percent maximum variation. However, simultaneous
dual column runs of the samples and calibration compounds were required to
achieve the necessary precision lr. t'r.is low concentration range. Time
limitations on this study and the expected high concentrations of the chosen
volatiles emitted from the 3lte precluded the need for this type of
laboratory protocol for this series of sample runs.
391
-------
TABLE 1
TEST »l
August 2, 1985, 9:33 a.m., CDT-10.-32 a.m. CDT,~7/10 cloud cover
Temperature (2m): 67~70°F Avg. wind speed <2m) - 6.0 mph
Temperature (6m): 68CF Avg. wind 3peed (6m) - 7.5 mph
Net flow, Regular - 16,064 gal Avg. wind direction - 105°
Net flow, Unleaded - 20,7')8 gal
Concentrations (ppm)
Location
of Samplers Isopentane n-Pentane n-tiexane Benzene Taooctarie r,-Heptane
70ir. downwind
4.6
2.5'
0.22
0.15
0.12
0.044
4.9
2.7
0.24
0.17
0.1 3
0.046
45m downwind
10.3
6.1
0.49
0. 32
0.26
0.094
11.2
6.6
0.54
0.36
0.29
0.10
45m downwind
10.8
6.4
0.51
0.3'i
0.27
0.10
(colocated)
11.2
6.6
0.54
0.36
0.29
0.11
30m downwind
18.0
10.6
0.86
0.56
0.45
0.16
17.5
10.8
0.88
0.59
0.47
0.17
30m downwind
18.2
10.6
0.86
0.57
0.45
0.17
(colocated)
17.0
10.5
n.90
0.60
0.47
0.18
TEST t2
August 8, 1985, 8:52 a.m., COT—9:53 a.m. CDT, scattered clouds
Temperature (2m): 73~30°F Avg. wind speed (2m) - 6.1 mph
Temperature (6m): 76-7S°F Avg. wind speed (6tn) - 7.8 mph
Net flow, Regular - 11,995 gal. Avg. wind direction - 1 Jl00
Net flow, Unleaded - 20,70'! gal.
Concentrations (ppm)
Location
of Samplers
1sopentane
n-Pcntane
n-Hcxanc
Benzene
T sooctane
n-Heptani
Upwind
0.11
0.016
0.015
0.008"
0.006'
0.11
0.012
0.015
0.023
0.006
0.008
80m downwind
0.28
0.13
0.017
0.025
0.007
0.007
0.32
0.15
0.021
0.023
0.008
0.006
52m downwind
1 .7
0.88
0.084
0.057
0.037
0.015
2.0
0.89
0.097
0.071
0.042
0.021
52m downwind
1 .8
0.83
0.090
0.064
0.042
0.016
(colocated)
1 .9
0.86
0.091
0.067
0.04 4
0.017
28m downwind
7.2
3.3
0. 46
0.26
0.17
0.061
7.7
3-9
0.48
0.27
0.18
0.066
28m downwind
7.0
3.2
0.35
0.25
0.16
0.05^
(colocated)
7.3
3.4
0.36
0.26
0.17
0.057
392
-------
TABLE 2
TEST #3
CDT-10:42 a.m. COT, fog lifting at start
August 16, 1 985, 9:43 a.m
changed to scattered clouds
Temperature (2m): 72-77°F Avg. wind
Temperature (6m): 72-77°F Avg. wind
Net flow, Regular - 19,984 gal Avg. wind
Net flow, Unleaded - 30,700 gal
Concentrations (ppin)
Location
of Samplers Iaopentanen-Pentane n-Hexane Benzene Isooctane
speed (2m) - 3-8 mph
speed (6m) - 2.9 mph
direction - 145°
Upwind
0.02'I
0.025
0.01 4
0.011)
0.010
0.010
0.018
0.017
0.025
0.026
n-Heptane
0T002"
0.002
50m downwind 6.2 3-2 0.31 0.20 0.12 0.047
6.4 3.6 0.32 0.21 0.13 0.051
35m downwind 10.1 5.6 0.50 0.32 0.20 0.073
10.8 6.1 0.54 0.35 0.23 0.087
35m downwind 10.6 5.8 0.52 0.34 0.21 0.083
(colocated) 10.9 6.0 0.53 0.35 0.22 0.086
15m downwind 52.0 2*4.6 2.6 1.6 1 .0 0.36
57.1 26.5 2.1 1.8 1.1 0. '12
15m downwind 55.9 25.7 2.8 1.8 1.1 0.12
(colocated) 57.6 27.0 2.4 1.8 1.1 0.44
August 20, 1985, 9:28 a.m.
Temperature (2m): 62-63°F
Net flow, Regular - 12,353
Net flow, Unleaded - 9,321
CDT'
TEST I
-10:28 a.m.
gal
gal
Concentrations
Locat ion
of Samplers
Upwind
CDT, cloudy, occasional drizzle
Avg. wind speed (2m) - 3.5 mph
Avg. wind direction - 110°
(ppm)
Iaopentane n-Pentane n-Hexane Benzene
0.016
0.01'(
0.018
0.016
0.019
o.o'.s
0.029
0.025
Isooctane
0.~008~~
0.006
n-Heptane
o7of3"
0.012
50m downwind
6.7
2.9
0.33
0.26
C.10
0.062
6.2
2.7
0.31
0.25
0.10
0.060
35m downwind
10.5
4.4
0.52
0.42
0.16
0.10
10.4
4.3
0.52
0.42
0.17
0.10
35m downwind
9.6
4.0
0.47
0. 39
0.15
0.094
(colocated)
10.4
4.4
0.52
0.42
0.17
0.10
15m downwind
31.8
12.0
1.6
1.3
0.55
0.28
34.1
12.7
1.7
1 .4
0.60
0.32
15m downwind
33-3
12.6
1 .6
1 .4
0.67
0.30
(colocated)
393
-------
TABLE 3
TEST 05
August 26, 1905, 9:23 a.m., CDT-10:08 a.m. clear
Temperature (2m): 66-69°F Avg. wind speed (2m) - 1.6 mph
Temperature (6m): 67~68°F Avg. wind speed (6m) - Jl.0 mph
Net flow, Regular - 19,315 gal Avg. wind direction - 310"
Met flow, Unleaded - 11,473 gal
Concentrations (ppm)
Location
of Samplers Taopentane n-Pentane n-Hexano Benzene Isooctane n-Heptane
Upwind
0,
,061
0,
,026
C,
,01 3
0.013
0.005
0,
,004
0.
.063
0,
,027
0,
.01 1
0.010
0.004
0,
m
o
o
113m downwind
0.
,006
0,
,00*1
0,
.005
0.009
0.017
0.
.002
0.
.007
0,
O
o
0.
,007
0.01 1
0.015
0,
,002
113m downwind
0,
,003
0.
,002
0,
.002
0.003
0.001
0,
,001
(colocated)
0,
,005
0,
,003
0,
,003
O.OOlJ
0.001
0,
.001
50m downwind
0,
,015
0.
,011)
0,
.012
0.022
0.005
0,
,005
0,
,01 1
0,
,009
0,
,010
0.017
0.004
0,
¦=r
c
c
50m downwind
0.
,011
0.
,008
0.
.005
0.008
0.002
0.
,002
(colocated)
0.
,01 4
0.
.009
0,
.006
0.009
0.002
0.
.002
25m downwind
0.
.031
0.
,017
0,
. 00'1
0.005
0.003
0.
.001
0.
.0*15
0.
,021
0.
.006
0.008
0.004
0.
.002
TEST #6
August 29, 1985, '4:11 p.m., CDT-^:56 p.m., partly cloudy, brief showers
Temperature (6m): 88-89°F Avg. wind speed (2m) -5.4 mph
Avg. wind speed (6m) - 4.0 mph
Net flow, Regular - 12,81U gal Avg. wind direction - 200°
Net flow, Unleaded - 13,083 gal
Concentrations (ppm)_
Location
of Samplers Isopentane n-Pentane n-Hexane Benzene Isooctane n-Heptane
Upwind
0.065
0.011
0.014
0.023
0.010
0.005
0.073
0.011
0.015
0.023
0.010
0.005
52m downwind
3-2
1 .8
0.15
0.11
0.080
0.031
2.9
1.7
0.15
0.10
0.090
0.029
26m downwind
6.8
3-7
0.31
0.21
0.16
0.060
6.6
3.5
0.31
0.21
0.15
0.058
?6m downwind
6.-4
3.7
0.29
0.19
0.14
0.055
(colocated)
6.6
3.6
0-30
0.20
0.15
0.056
13m downwind
12.6
7.3
0.67
0.38
0.30
0. 1 1
13.0
7.4
0.69
o.no
0.31
0.12
394
-------
TABLE 1
TEST It!
September 5, 1985, 2:30 p.m., CDT~3:15 a.m.,CDT, Clear
Temperature (6m): 93~910F Avg. wind speed (2m)-11.3 mph
Net flow, Regular - 7,816 gal Avg. wind speed (6m)-15.0 mph
Net flow, Unleaded - 13,105 gal Avg. wind direction - 310°
Concentrations (ppm)
Location
of Samplers
Isopentane
n-Pentane
n-Hexane
Benzene
lsooctane
n-Heptan<
Upwind
0.01 2
0.011
0.C09
0.016
0.005
O.OOif
0.012
0.010
0.008
0.013
O.OO'I
0.001
61m downwind
2.1
0.9?
0.11
0.073
0.015
0.022
32 downwind
1.5
1.8
0.22
0.15
0.081
0.011
1.7
2.0
0.23
0.16
0.089
0.017
32m downwind
1.8
2.0
0.23
0.1 6
0.090
0.018
(colocated)
16m ground
9.5
3.8
0.13
0.29
0.18
0.088
11 .5
1.6
0.51
0.37
0.22
0.112
I6m~2m nigh
10.6
1.2
0.19
0.31
0.21
0.10
10.8
1.3
0.50
0.35
0.21
0.1 1
DESCRIPTION OF FINDINGS
£Ield Data
Six volatile organic compounds were chosen for evaluation in this study.
These were isopentane, n-pentane, n-hexane, benzene, lsooctane, and n-
heptane. The choice of these compounds was based on a report by the U.S.
Environmental Protection Agency (P383~256206, EPA-l50/3~80-038B), which
shows these to be the primary volatile components of regular and unleaded
gasoline.
Tables 1-1 describe the actual field data collected during each test.The
tables also contain information on weather conditions and sampler location.
A "co-located" designation simply means that two samplers simultaneously
monitored at that point. As shown in the tables, meteorological conditions
varied considerably for each test run. Position (distance from the source)
of the samplers were governed by the meteorological conditions as well as
limitations on how close to the source a sampler could be placed. In
general, safety limitations restricted sampler placement to at least thir-
teen meters from the source. Stable meteorological conditions (i.e., light
surface winds and isothermal or ar. inversion profile) dictated that the
downwind samplers be placed closer to the source In order to remain in the
plume centerline. Unstable atmospheric conditions (i.e., moderate to high
wind speeds and lapse profiles) resulted in the downwind samplers being
located farther away from the source.1
"Due to a large shift in wind direction approximately ten minutes into Test
5, the concentration values do not represent those along the centerline.
395
-------
TABLE 5
SUMMARY OF CO-LOCATED SAMPLER DATA
Concentrations (ppm)
Teat No. Iaopentane n-Pentane n-Hexane Benzene Isooctane n-Heptane
1-A 10.3 6.1 0.49 0.32 0.26 0.094
1 1 .2 6.6 0.54 0.36 0.29 0.10
10.8 6.4 0.51 0.34 0.27 0.10
11.2 6.6 0.54 0.36 0.29 0. 11
1-B 18.0 10.6 0.86 0.56 0.45 0.16
17.5 10.8 0.88 0.59 0.47 0.17
18.2 10.6 0.86 0.57 0.45 0.17
17.0 10.5 0.90 0.60 0.47 0.18
2-A 1.7 0.88 0.084 0.057 0.037 0.015
2.0 0.89 0.097 0.071 0.042 0.021
1.8 0.83 0.090 0.064 0.042 0.016
1.9 0.86 0.091 0.067 0,044 0.017
2-B 7.2 3.3 0.46 0.26 0.17 0.061
7.7 3.9 0.48 0.27 0.18 0.066
7.0 3.2 0.35 0.25 0.16 0.057
7.3 3.4 0.36 0.26 0.17 0.057
3"A 10.1 5.6 0.50 0.32 0.20 0.078
10.8 6.1 0.54 0.35 0.23 0.087
10.6 5.8 0.52 0.3'1 0.21 0.083
10.9 6.0 0.53 0.35 0.22 0.086
3-B 52.0 24.6 2.6 1.6 1.0 O.38
57.1 26.5 2.4 1.8 1.1 0.42
55.9 25.7 2.8 1.8 1.1 0.42
57.6 27.0 2.4 1.8 1.1 0.44
4-A 10.5 4.4 0.52 0.42 0.16 0.10
10.4 4.3 0.52 0.42 0.17 0.10
9.6 4.0 0.47 0.39 0.15 0.094
10.4 4.'I 0.52 0.42 0.17 0.10
396
-------
TABLE 5
(continued)
Concentrations (ppm)
Teat No. Isopentane n-Pentane n-Hexane Benzene Tsoootane n-Heptane
1-B 31.8 12.0 1.6 1.3 0.55 0.28
3JI. 1 12.7 1.7 1.1 0.60 0,32
33.3 12.6 1,6 1.1 0,67 0.30
5-A 0,006 0.001 0.005 0.009 0.017 0.002
0.007 0.005 0.007 0.011 0.015 0.002
0.003 0.002 0.002 0.003 0.001 0.001
0.005 0.003 0.003 0.001 0.001 0.001
5-B 0.015 0.011 0.012 0.022 0.005 0.005
0.011 0.009 0.010 0.017 0.001 0,001
0.011 0.008 0.005 0.008 0.002 0.002
0.011 0.009 0.006 0.009 0.002 0.002
6-A 6.8 3-7 0.31 0.21 0.16 0.060
6.6 3.5 0.31 0.21 0.15 0.058
6.1 3.7 0.29 0.19 0.11 0.055
6.6 3.6 0.30 0.20 0.15 0.056
7"A 1.5 1.8 0.22 0.15 0.081 0.011
1.7 2.0 0.23 0-16 0.089 0.017
1.8 2.0 0.23 0.16 0.090 0.018
397
-------
Teat No.
1 - A
1-B
2-B
3-A
3-B
1- A
14-B
6-A
TABLE 6
SELECTED CO-LOCATED SAMPLER DATA
ISOPENTANE
Percent
Difference
Concentration (ppm) (i)
10.3"
11.2
10.8
11.2 8.0
18.0
17.5
18.2
17.0
5.6
7.2
7.7
7.0
7.3
9.1
10.1
10.8
10.6
10.9
52.0
57.1
55.9
57.6
7.3
9.7
10.5
10. 'I
9.6
10. IJ
8.6
31 .8
3*1.1
33.0
6.8
6.6
6.U
6.6
1.5
1.7
4.8
6.7
5.9
6.2
39B
-------
TABLE 7
SELECTED CO-LOCATED SAMPLER DATA
BENZENE
Percent
Difference
Teat No. Concentration (ppm) (%)
1-B 0?5S
0.59
0.57
0.60 6.7
3-B 1.6
1.8
1 .8
1.8 11.1
m-b 1.3
1.11
1.4 7.1
7-1 0.15
0.16
0.16 6.2
SELECTED CO-LCCATED SAMPLER DATA
n-HEXANE
Percent
Di fference
Test No. Concentration (ppm) (J)
1-B ~ 0.86
0.88
0.86
0.90 4.4
il-B
2.6
2.4
2.8
2.4
1 .6
1.7
1.6
0.22
0.23
0.23
14.3
5.9
4.3
399
-------
Co-located Sampler Data
Two samplers were located 3ide by side at the 9ame height at two
downwind sample points in order to determine sampler precision. Co-located
samplers were treated in exactly the same manner as the other spheres, but
represent two distinct samples because they were not connected to a common
sampler manifold. Tables 5~7 summarize the results of the co-located
sampler data.
The data Indicate excellent correlation among samplers. In the
selected data cases, the difference In co-located volatile compound con-
centrations was less than eighteen percent for co-located samplers. Results
presented in the table3 3how that most of the differences ranged between
five and ten percent.
CONCLUSIONS
The following conclusions appear warranted based on the data:
1) The stainless steel spheres with microvalves are good
sample collection vessels for field use: they are easy
to prepare for field tests; require no maintenance In
the field; are easily transported to and from the field;
and can be adjusted for varying sample collection times.
2) The cryogenic gas chromatograph with flame ionization
detector is compatible with the field samples collected
in this study. if the procedures used herein are fol-
lowed, reliable data can be generated.
3) Co-located sampler data 3how that the precision between
samplers Is very good. The difference in no-located
sampler data ranges between 2.8 percent to 17.9 percent,
although most variations "tie between 5 percent and 10
percent.
'() Data Indicate that the downwind centerllne of the plume
concentrations of isopentane, n-pentane, n-hexane,
benzene, isooctane, and n-heptane vary from 57.1 ppm t<3
less than 0.01 ppm for sampler distances from the source
between 13 m and 80 rr,, respectively. These concentra-
tions are also dependent on meteorological conditions.
5) Visual observations of the source indicate that the
volatile emission fraction settles close to the emission
point and is resuspertded by ambient air flow to form a
plume. Modeling techniques will have to take this point
Into account.
BIBLIOGRAPHY
i. Bjorkland, J., Compton, B., and Zwelg, G., "Development of Methods for
Collection and Analysis of Airborne Pesticides." Report for Contract
No. CPA 70-15, National Air Pollution Control Association, Durham, NC,
1970.
?. Blackmore, 1)., M. Herman, and J. Woodward, "Heavy Gas Dispersion
Models," J. Haz. Mat,., 6:107-1 ?8.
Brottel 1 , T. A., and Grob, R. L., "Cryogenic Techniques in Gas
Chromatography," ^erlean_Laborabory, Pp. 19—33 (October, 1985).
400
-------
4. Grosjean, D., Fung, K., and Atkinson, R., "Measurements of Aldehydes in
the Air Environment," Proc. Air Poll. Cont. Assoc., Paper 80-50.1,
1980.
5. Holden, M., S. Rust, R. Smith, and J. Koetz, "Evaluation of Cryogenic
Trapping as a Means for Collecting Organic Compounds in Ambient Air,"
Draft Final Report on Contract No. 68-02-3187, 1981.
6. Holden, Michael W., Richard N. Smith, and William A. McClenny,
"Reduced-Temperature PreconcientratIon and Ga3 Chromatographic Analysts
of Ambient Vapor-Phase Organic Compounds: System Performance."
7. Kebbekus, B. 3., and Bozzelll, J. W., "Collection and Analysis of
Selected Volatile Organic Compounds in Ambient Air," F.PA-600/1-83"027,
U.S. Environmental Protection Agency, Research Triangle Park, NC, 1979.
8. Krost, K. , Pelllzzari, E. D., Walburn, S. G., and Hubbard, S. A.,
"Collection and Analysis of Hazardous Organic Emissions," Analytical
Chemistry, 51, 810—817. 1982.
9. Lewis, R. G. and Jackson, M. ()., "Modification and Evaluation of a
High-Volume Air Sampler for Pesticides and Semlvolatlle Industrial
Organic Chemicals," Anal. Chern, 51, 592-591, 1982.
10. Lewis, R. G., Jackson, M. D., and MacLeod, K. E., "Protocol for
Assessment of Human Exposure to Airborne Pesticides," EPA-600/2-80-180,
U.S. Environmental Protection Agency, Research Triangle Park, NC, 1980.
11. Pelllzzari, E. 0. and Bunch, J. E., "Ambient Air Carcinogenic Vapors-
Improved Sampling and Analytical Techniques and Field Studies," EPA-
600/2-790-081, U.S. Environmental Protection Agency, Research Triangle
Park, NC 1979.
12. Pleil, Joachim D., and William A. McClenny, "Reduced-Temperature
PreconcentratIon and Gas Chromatographic Analysis of Ambient Vapor-
Phase Organic Compounds: System Automation."
13. Riggln, R. M., "Compendium of Methods for the Determination of Toxic
Organic Compounds in Ambient Air," U.S. EPA-600/1-81-011 (1981).
11. Singh, H. B., L. J, Salas, R. Stiles, and H, Shigeishi, "Measurements
of Hazardous Organic Chemicals In the Ambient Atmosphere," NTIS PB83—
156935, EPA-600/S3-83-002 (1983).
15. Trlpp, R., "Automatic Cryogenic Sampling and Gas Chromatographic
Analysis of Volatile Organic Compounds," U.S. EPA, Region VII, Kansas
City, KS. internal report (1981).
16. U.S. EPA, "Bulk Gasoline Terminals: Background Information for
Promulgated Standards," NTIS />PB83~256206, EPA-150/3-80-038B (1983).
17. Walling, J. F., Berkling, R. E., Swanson, D. H., and Toth, F. J.,
"Sampling Air for Gaseous Organic Chemical-Applications to Tenax," EPA-
-6 00/7-51-82-059, U.S. Environmental Protection Agency, Research
Triangle Park, NC, 1982.
18. Wampler, T. P., Bowe, W. A,, and Levy, E. J., "Splltless Capillary GC
Analysis of Herbs and Spices Using Cryofocusing," American Laboratory,
Pp. 76-81 (October, 1985).
401
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CANISTER-BASED VOC SAMPLERS
William A. McClenny,
T. A. Lumpkin,
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina
J. D. Pleil, K. D. Oliver, D. K. Bubacz,
J. W. Faircloth and W. H. Daniels
Northrop Services, Inc. - Environmental Sciences
Research Triangle Park, North Carolina
ABSTRACT
Canister-based sampling units for volatile organic compounds are a viable
alternative to sampling onto adsorbent-packed cartridges. Units for sam-
pling periods of from one minute to one week (periodic sampling) have been
assembled and tested. Side-by-side field evaluation of weatherized, am-
bient air samplers show ± 5.1% percentage difference at low and fraction-
al ppbv levels; a sequential sampler has been used to document VOC varia-
bility in laboratory air.
INTRODUCTION
Canister-based sampling systems for toxic volatile organic compounds
(VOCs) have been developed by EMSL, US EPA as a possible alternative to col-
lection on solid sorbents. The most frequently used solid sorbent, Tenax GC,
has been shown empirically to give results that are difficult to inter-
pret.1"2 Use of the canister-based sampling systems for toxic VOCs has
evolved as an extension of the use of canisters for halocarbon3 and hydro-
carbon analysis4, primarily with canisters treated by the proprietary
process of SUMMA® polishing. The SUMMA® process is available on license
from Molectrics Corp.5 Demaray Scientific Corp6 and Biospherics7 supply
most of the SUMMA® polished canisters currently in use for collection of
VOCs. Canisters have been used in a number of applications prior to which
some storage stability data were obtained for the specific compounds of
interest. Reference to these previous studies, and the documentation of
storage stability for a group of eighteen VOCs performed by Northrop Ser-
vices, Inc. are now available8 as a result of the EPA-sponsored development
program.
402
-------
Additional storage stability studies have recently been completed by an EPA
contractor, Battelle Columbus Laboratories, and are available on a limited
basis.9 Initial studies with the canisters have included a survey of VOCs
in indoor air10 and comparison studies of VOC sampling procedures.11'12
A related application13 has been the use of canisters as a sampling and
storage medium for a national program to document the nonmethane organic
compound concentration (as ppbC) for the purpose of SIP (state implementa-
tion plans) revision. This program has been effective in establishing the
reliability of methods for shipping the canisters from the sampling loca-
tions to a central analytical laboratory, as well as being a successful
monitoring program. Various canister-based sampling configurations have
been evaluated by the EMSL, EPA to achieve time-averaged continuous (or
periodic, integrative) sampling and to obtain short-term samples for survey
or temporal variability studies. This paper gives a description of the
sampling systems and of representative results.
DESCRIPTION AND SELECTED RESULTS FOR CANISTER-BASED SAMPLING SYSTEMS
Advantages/Disadvantages Relative to Solid Sorbent Cartridges
The canister-based samplers have the following advantages as compared
to solid sorbent cartridges:
1. Canister pressure can be used as an indicator of correct sampler
operation.
2. No thermal desorption is required.
3. Multiple analyses can be performed from a canister.
4. Artifact problems related to the storage of enhanced trace gas concen-
trations, to thermal decomposition of the sorbent, to memory effects in
the sorbent and to the effect of thermal desorption on the target
compound concentration are not present.
5. The operator of the system need not be present at the beginning and
end of the sampling run, i.e., to cap the sorbent.
6. The sample concentrations can be easily diluted if concentrations are
too high.
7. The evacuated canisters can be used for sampling without need for
electricity.
The canister-based samplers have the following disadvantages as compared to
solid sorbent cartridges:
1. The sample is stored after passage through a sampling train, each com-
ponent of which (filter, pump, valve) must be clean. Solid sorbent
tubes are usually the first element in the sampling train.
2. Air leaks in system elements upstream of the canister are a potential
source of error.
3. A limited sample volume (approximately 15 liters) at -24 psig can be
stored in canisters of easily manageable size (6 liters).
4. Because of the limited prior use of the canister-based samplers for
toxic VOCs, some uncertainty remains with respect to potential prob-
lems.
Continuous Samplers for Obtaini ng Time-Averaged Concent rati ons The weather-
ized sampler currently Tn use Tn tPATie'ld studies is shown schematically in
Figure 1. This sampler is designed for limited temperature control of the
inlet line and the interior of the sampler housing. Components have been
selected for proven reliability and not for cost or size. These components
are listed in Table 1 along with corresponding alternate components that
403
-------
have either a cost or size advantage. The alternate components are being
tested for possible updating of the sampler design. The sampling train for
the current EPA sampler is patterned after that used for NMOC sampling'3
except that a Tylan model FC-260 flow controller is used instead of a hypo-
dermic needle flow restrictor. The flow controller was required to main-
tain flow rates at 10 seem over 24 hour periods during which the canister is
filled from vacuum to 24 psig to collect about 15 liters of whole air sample.
A number of preliminary ambient air tests have been performed in prep-
aration for the first field application of the sampler. A code to the
evaluation tests is provided as Table 2. Samplers were numbered one through
five. Sampling locations were either on the roof of the Environmental Re-
search Center Annex Building or in the Northrop Services analytical labor-
atory. Results from these tests for a set of target compounds are given in
Tables 3 and 4. Additional compounds are listed in Table 5. The results
of comparison of samplers are given in nominal parts-per-bi11 ion (ppbv).
These concentration values are only approximate. The average value of
percentage differences for tests 1-4 involving paired samplers #1 and #2
and test 5 involving paired samplers #3 and #4, is ± 5.1% as calculated
by taking the difference between two nominally identical analysis results,
dividing by their sum and multiplying by 100%; excluding the o-xylene
result of test #1, this difference is '-3.5%. As noted in Table 2, evalu-
ation test #6 was not a legitimate side-by-side test and is not included in
the averages. This may explain the large percentage difference for the
estimation of o-xylene in test i?6. With respect to side-by-side ambient
air tests involving the target compounds, the tests show agreement within
0.3 ppbv for concentrations of 5 ppbv or less and agreement of ± 15% for
higher concentrations, except for o-xylene. Aside from the target com-
pounds, some specific contamination was noted in samplers #3, #4, and #5.
Sampler #4 gave consistently high Freon 113 concentration levels of 3-4
ppbv above the concentrations from samplers #3 and #5; #3 sampler gave a
Freon 11 concentration of approximately 1 ppbv above the others; and #5
gave consistently high relative values for an unidentified hydrocarbon. In
summary, the initial comparison tests indicated general agreement among
samplers for the target compounds but there was also evidence that better
quality control procedures should be implemented during assembly of sampler
components.
Sampler components like those listed in Table 1 can be used to fabri-
cate canister-based systems with sampling periods from approximately 1 min
up to 24 hours. For shorter time intervals less stringent performance
requirements are placed on the sampler components, and smaller pumps and/or
less expensive flow restrictors (e.g., hypodermic needles) can be used.
For sufficiently short collection periods of less than approximately 2
hours, the evacuated 6-L canisters can be used without a pump to obtain a
rough time-weighted average sample. Flow profiles for a 500 seem Tylan mass
flow controller and for a hypodermic needle (30 gauge) restrictor are shown
in Figure 2. The advantage of the hypodermic needle is that no electrical
power is required; this would be advantageous for taking samples on buses,
cars, airplanes, etc. On the other hand, the controller provides a more
constant flow rate over the sampling period.
The sampler configuration shown in this section is similar to that in
use by other groups. Of particular interest is the work done by Rasmussen14
on sampler design. One difference from the design shown in Figure 1 is the
order of components. A pump is used to pressurize a backpressure regulator
which vents a large portion of a high throughput while maintaining a con-
stant pressure upstream of a flow rate restrictor that leads into the canis-
ter.
404
-------
Samplers for Obtaining Time-Weighted (Periodic, Integrative) Average Concen-
trations - New versions of the canister-based sampling system are required
to meet EMSL's need for special studies. A pending indoor air survey study
for VOCs will require a sampler to cover a full week, thereby simulating
the major repetitive activity pattern to which occupants are exposed. A
tentative sampling design is shown in Figure 3. This unit will operate in
a periodic integrative mode, taking a limited duration sample during each
increment of time, e.g., every hour. The representativeness of the sample
will depend on the temporal variability of the various VOC sources. For
this reason such a sampler may not be the one actually selected for the
study. As indicated in Figure 3a, the sampler design includes a filter
element, on-off valve, electric timer, flow restrictor and 6-Liter canis-
ter. Two restrictors have been used to test the design over simulated
week-long sampling periods. In the first test a hypodermic needle restric-
tor was used. The inlet configuration was the same as in a recent NMOC
sampler design,13 The valve was opened for 15 s during each of 168 time
increments (simulating 168 hourly samples per week). A gradual 18% decrease
in peak flow rate was noted (See Figure 3b) and a total volume of approxi-
mately 3.5 liters was sampled. Similarly, a Whitey micrometering valve
(SS-21R32) was set for 17.5 seem and operated for 168 times with 1 min.
sampling durations. A 23% decrease in flow rate was noted (See Figure 3c)
while approximately 3.5 liters was sampled. tn both cases, the final
canister pressure is approximately 0.5 atmospheres. To the extent that the
restrictor acts as a critical orifice, the sample flow rate should be
constant until the pressure drop across the orifice approaches 0.5 atomos-
pheres. One set of components for this system are identified by under-
lining in Table 1 (See footnote). The anticipated approximate cost of such a
unit is less than $1000.
Samplers for Temporal Variability Studies - A commercially available sam-
pler using a set of twelve 5UMMA® polished stainless steel syringes (150
ml) has been modified for ease of analysis. The unit, manufactured by
Oemaray Scientific, is made as a sequential sampler. Along with controls
for setting sample period and duration, it can now be returned to the
analysis laboratory with the syringe units in place and be used to exhaust
the individal syringes, one at a time, into a sample line leading into the
analytical instrument. Signals provided by the GC, such as the external
valve control outputs available on a HP5880, trigger the motor drive in
reverse. The action of the drive allows the syringe exhaust port to open
and gradually releases the contents of the syringe into a manifold through
which zero air is passing. The contents are then passed through a reduced
temperature trap to be concentrated prior to analysis.15 Preliminary
tests of the storage stability of a set of target compounds show that a
number of the higher molecular weight compounds are either not efficiently
stored or are not efficiently transferred from the syringes through the
manifold to the analytical system. This ambiguity is still under study.
Results of the evaluation tests are shown in Table 6. Two tests were per-
formed by filling six syringes with a known mixture of eighteen VOCs in
humidified zero air. Individual component concentrations were in the 2-4
ppbv range. The value of concentration averaged over the six syringes was
compared to a direct analysis of the sample mixture. The results show the
percentage difference calculated as a difference divided by a sum, multi-
plied by 100%. In general, the heavier compounds do not store as well as
in the 6-liter SUMMA® polished canisters but, as noted earlier, the cause
may not be the storage characteristics of the syringes. T>ie remaining test
of ambient air data shows the percentage difference between six paired
samples of a direct analysis and of syringe samples taken simultaneously and
analyzed 24 hours later. Concentrations are quite low in most cases
405
-------
(< 5 ppbv), and show lower concentrations in the syringe sample in all but
9 of the 86 individual comparisons (not shown) that lead to the percentage
differences in the ambient air test. Analysis of data show that better
comparisons occur for the higher concentrations indicating that system
precision is important. The result of one indoor air temporal variability
study sequence is shown in Figure 4. The concentration variations are in-
dicative of early morning changes in air ventilation rates as air handling
equipment is turned on. Dichloromethane and chloroform are decreasing in
concentration while Freon 11 and Freon 113 are increasing in concentration,
CONCLUSION
Initial results for canister-based samplers are encouraging in that
side-by-side tests of weather!zed samplers generally show small percentage
differences at low ppbv concentration levels. The samplers can be con-
figured to provide samples collected over collection periods of from one
minute to one day by sampling continuously, with extension to one week if
periodic sampling is used. For short duration sampling the vacuum of the
canister can be used to establish a sampling rate so that no electricity is
required. Sequential samplers using stainless steel syringes with SUMMA®
polished surfaces show an apparent loss on storage of certain compounds, an
observation which is being investigated further.
REFERENCES
1. J. F. Walling, "The utility of distributed air volume sets when
sampling ambient air using solid adsorbents," Atmospheric Environ-
ment, 18:855-859 (1984).
2. J. F. Walling, J. E. Rumgarner, J. 0. Driscoll, C. M. Morris, A. E.
Riley and L. H, Wright, "Apparent reaction products desorbed from
Tenax used to sample ambient air," Atmospheric Environment, 20: 51-
57 (1986)
3. D. E. Harsch, "Evaluation of a versatile gas sampling container de-
si gnAtjno^jjrk Envjj^onmervt^, 14:1105-1107 (1980).
4. M. W. Holdren, H. H. Westberg and H. H. Hill, "Analytical methodol-
ogy for the identification and quantitation of vapor phase organic
pollutants," (Project Report, CRC-APRAC Project No. CAPA-11-71)
Washington State University, Pullman, Washington. (1979).
5. Molectrics, Inc., 1083 East Bedman Street, Carson, California 90746.
6. Demaray Scientific Instrument, Ltd., S.E. 1122 Latah Street, Pullman,
Washington 99163,
7. Biospherics Research Corp., 1121 N.W. Donelson Road, Hi 11sboro,
Oregon 97123.
8. K. D. Oliver, J. 0. Pleil and W. A. McClenny, "Sample integrity
of trace level volatile organic compounds in ambient air stored in
SUMMA® polished canisters," accepted for publication in Atmospheric
Envi ronment.
406
-------
9. M. W. Holdren and D. L. Smith, "Stability of volatile organic com-
pounds while stored in SIJMMA® polished stainless steel canisters,"
(Final Report, Contract 68-02-4127, Environmental Monitoring Systems
Laboratory, U.S. Environmental Protection Agency) Battelle's Columbus
Division, Columbus, Ohio (1986).
10. J. D. Pleil, K. D. Oliver and W. A. McClenny, "Volatile organic
compounds in indoor air: a survey of various structures," Proceed-
ings: APCA Speciality Conference on Indoor Air Quality, Ottawa,
Canada, April 29-May 2 (1985).
11. M. W. Holdren, D. L. Smith and R. N. Smith, "Comparison of ambient
air sampling techniques for volatile organic compounds," (Final
Report, Contract 68-02-3487, WA37, Environmental Monitoring Systems
Laboratory, U.S. Environmental Protection Agency) Battelle's Columbus
Division, Columbus, Ohio (1985).
12. C. W. Spicer, M. W. Holdren, L. E. Slivon, R. W. Coutant and D. S.
Shadwick, " Intercomparison of sampling techniques for volatile organic
compounds in indoor air," (Draft Final Report, Contract 68-02-3745,
WA 25/35, Environmental Monitoring Systems Laboratory, U.S. Environ-
mental Protection Agency) Battelle's Columbus Division, Columbus, Ohio
(1986).
13. F. F. McElroy, V. L. Thompson and H. G. Richter, "A cryogenic pre-
concentration-direct FID (PDF ID) method for measurement of NMOC in
ambient air," (EPA Project Report, EPA/600/4-85/063, Jan. 1986),
Environmental Monitoring Systems Laboratory, US EPA, Research Triangle
Park, NC (1986).
14. R. A. Rasmussen, Personal Communication, Oregon Graduate Center; 19600
N.W. Walker Road, Beaverton, Oregon.
15. W. A. McClenny, J. D. Pleil, M. W. Holdren and R. N. Smith, "Automated
cryogenic preconcentration and gas chromatographic determination of
volatile organic compounds in air," Analytical Chemistry, 56:2947-
2951 (1984).
407
-------
Table 1. List of Canister-Based Sampler Components
Component
Identification
Suppli er
1. Sample canister
2. Vacuum/pressure
3. Chromatographic
grade stainless
steel tubing
4. Metal bellows
pump
4a Stainless steel
diaphragm pump
5. Magnalatch
solenoid valve
6. Control Timer
6a Chrontrol timer
7. Electronic Flow
Controller
6 Liter stainless steel
sampling canisters,
SUMMA® passivated
Model 0647
Model 63-3704
Cat. #8125
Model MB-151
Model FC-1121-35
V52RAM 1100
Model 7008-00
Model CD-4 FZ
Model FC-260, 0-100
seem range with read-
out box, Model R0-14
Demaray Scientific
Instruments, Inc.
S.E. 1122 Latah St.
Pullman, WA 99163
(509) 332-8577
Matheson
P0 Box 136
Morrow, GA 30260
(404) 961-7891
Alltech Associates
Oeerfield, IL
Metal Bellows Corporation
1075 Providence Highway
Sharon, MA 02067
Blospherics Research Corp.
1121 N.W. Donelson Road
Hillsboro, OR
Skinner Valve
New Britain, CT
Paragon Electric Company,
Inc.
606 Parkway Blvd.
P0 Box 28
Two Rivers, WI 54201
Lindburg Enterprises, Inc.
San Diego, CA
Tylan Corporation
19220 S. Normandie Avenue
Torrance, CA 90502
(213) 532-3420
408
-------
Table 1. List of Canister-Based Sampler Components
(continued)
Component
Identification
Stippl ier
7a* Whitey micrometer
val ve
8. Inlet Line
Heater Control
9. Enclosure Heater
10. Enclosure Fan
11. Enclosure Heater
Thermostat
12. Enclosure Fan
Thermostat
13. Inline Filter
14. 2 Micron Filter
Elements for
Inline Filter
15. Elapsed Time
Meter
16. Max-Min Thermo-
meter
Model SS-21R32
Model 6102-J-0/300°F
"Socket Mount"
Controller
Wat low, Part 04010080
EG&G Rotron
Model SUZA1
Model 3455-RC-O100-0222
Open on Rise Sensor
Switch
Model 3455-RC-O100-0244
Close on Rise Sensor
Switch
SS-2FT7-7
Nupro "F" Series
SS-2F-K4-2
Type 6364
P/N 10082
P/N 9327H30
Thomas Scientific
Whitey Co.
Highland Hts., OH
Omega Engineering Inc.
Omega Drive, Box 4047
Stamford, CT 06906-0047
(203) 359-1660
Watlow Co., P0 Box 250
Pfafftown, NC
(919) 922-3993)
EGSG Rotron
Woodstock, NY
Elmwood Sensors, Inc.
500 Narragansett Park Dr.
Pawtucket, RI 02861
(407) 727-1300
Elmwood Sensors, Inc.
500 Narragansett Park Dr.
Pawtucket, RI 02861
(407) 727-1300
Nupro Company
4800 E. 345th St.
Wi 1loughby, OH 44094
Nupro Company
4800 E. 345th St.
Willoughby, OH 44094
Conrac, Cramer Division
Old Saybrook, CN
Brooklyn Thermometer Co.,
Inc.
Alternate Components
Components for Periodic, Integrative Sampler
409
-------
Table 2. Code to Evaluation Tests on Canister-Based Samplers
1. Side by side comparison of Samplers #1 and 92 on the roof of the ERC
Annex building. Sampling period of 24 hours.
2. Same as 1.
3. Same as 1.
4. Sample audit material simulation test -- EPA Group III cpds. Samplers #1
and #2.
5. Side by side comparison of Samplers #3 and #4 in Northrop Services
Laboratory. Sampling period of 24 hours.
6. Same as 1, however, Sampler #1 was sampling with a loose connector
inside box, resulting in a sample of box air.
7. Side by side sampling of humidified zero air through the sampler system
for Samplers II and §2. No canisters involved. Real time sample taken
at the canister position using the analytical system.
8. Three sequential tests for contamination of Sampler #5 by sampling
humidified zero air after passage through the sampler. Real time test
as in Code 7 test.
9. Same as 7 again for Samplers #1 and #2.
10. Side by side comparison of Samplers #3, #4, and #5 on the roof of the
ERC Annex building. Sampling period of 24 hours.
11. Repeat of Test 10.
12. Repeat of Test 10.
13. Repeat of Test 10.
410
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Table 3 - Results of GC-MS Analysis During Evaluation Tests — Values Given in PPBV Based on
Working Standards. See Table 2 for Type of Test.
TEST #
COMPOUND
Vinyl Chloride -,0.7 -,0.2
1.1 Dichloroethene 9.0,9.0 -,0.2 0.2,0.3
Methylene Chloride 2.9,2.6 0.7,0.8 3.9,3.9 65.5,67.5 1.6,1.5
Chloroform 0.1,0.1
1.2 Dichloroethane
1,2 Dibrcmioetharie
1,1,1 Trichloroethane 0.6,0.5 0.3,0.3 1.0,1.0 0.8,0.7
Benzene 1.6,1.4 0.5,0.4 1.5,1.5 0.7,0.6
Tetrachloromethane 0.1,0.1 0.1,0.1 0.1,0.1 0.1,0.1 0.1,0.1
Trichloroetbene 0.2,0.1
Toluene 8.0,7.6 0.8,0.9 2.6,2.3 7.8,9.8 1.9,1.9 1.2,1.0 0.1,0.2 0.1,0.2,0.2
Tetractil oroethene 0.5,0.5 — — 0.1,0.1 0.1,0.1 0.1,0.1 0.1,0.1
Chlorobenzene 8.5,11.0
o-Xylene 2.0,4.2 0.1,0.1 0.6,0.5 0.3,0.3 1.1,0.2
* Test tf> was not performed properly (see Table 2)
-------
Table 4. Results of GC-MS Analysis During Evaluation Tests. Values Given in
PPBV Based on Working Standards. Ambient Air Side-By-Side Sampling
of Samplers 3,4,5. See Table 2 for Type of Test.
TEST §
10 11 12 13
COMPOUND
Vinyl Chloride 1,1,0,9,0.9 0.7,0.5,0.4
1.1 Dichloro-
ethene
Methylene
Chloride 2.4,2.5,2.8
Chloroform 0.03,0.03,0.02 0.1,0.0,0.0 0.1,0.1,0.1
1.2 Dichloro-
ethane
1,2 Dibromo-
ethane
1,1,1 Trichloro-
ethane 0.5,0.4,0.4
Benzene 0.7,0.7,0.7 0.4,0.5,0.5 0.5,0.6,0.5 0.7,0.7,0.7
Tetrachloro- 0.1,0.1,0.1 0.1,0,2,0.1 0.1,0.1,0,1 0.1,0.1,0.1
methane
Trichloro-
ethene
Toluene 1.0,1.1,1.1 0.4,0.4,0.4 0.7,0.8,0.7 1.3,1.4,1.5
Tetrachloro- 0.1,0.1,0.1 0.0,0.0,0.1 0.1,0.0,0.1 0.2,0.2,0.2
ethene
o-Xylene 0.2,0.2,0.2 0.1,0.1,0.1 0.2,0.1,0.2 0.2,0.3,0.3
412
-------
Table 5. Results of GC-MS Analysis for Additional Compounds During Evaluation Tests. Values
Given in PPBV Based on Working Standards. See Table 2 for Type of Test
TEST #
COMPOUND 1 2 3 5 10 12 13
Ethylbenzene 1.1,1.1 0.4,0.4 0.2,0.2
Styrene — 0.1,0.2
co m,p Xylene 3.6,3.5 0.3,0.4 1.3,1.3 0.7,0.7 0.4,0.4 0.3,0.3 0.5,0.5
0.4 0.3 0.6
4-EthyHoluene ~ — 0.2,0.2 0.2,0.2
1,3,5-Methylbenzene 0.6,0.9 0.3,0.2
1,2,4-Methylbenzene 2.7,2.6 0.2,0.2 0.9,0.9 0.4,0.4 0.3,0.3 0.2,0.2
0.3 0.2
Hexachlorobutadiene 0.2,0.2 0.1,0.1
0.1
-------
Table 6. Evaluation Results Comparing Analysis from Sequential Syringe
and Direct Analysis
Mixture with Zero Air
COMPOUND dfl* n* Ambient Air
1,2 Dlchloroethene
-1.1*
10.2%
—
Freon 113
-2.2%
1.8%
—
Chioroform
1.5
0.2%
--
1,2 Dichloroethane
-10.0
12.2
1,1,1 Trlchloroethane
1.7
0.6
-19.9
Benzene
-1.1
-5.7
-9.4
Tetrachloromethane
-7.2
-0.9
-7.8
Trichloroethene
1.6
-1.2
-18.7
cis-Dichloropropene
!
ro
—
—
trans-Dichloropropene
-8.7
—
—
Toluene
7.2
6.6
-17.7
1,2 Dibromoethane
-7.0
-9.9
—
Tetrachloroethene
-0.9
-5.7
-12.9
Chlorobenzene
-10.9
-20.1
--
o-Xylene
-9.1
-9.2
-18.7
Benzylchloride
-24.3
-26.6
—
Hexachlorobutadi ene
-5.6
-12.6
--
F-12
15.4
2.2
-6.7
Methylene Chloride
--
__
-4.1
* (-) Control > Average Syringe
414
-------
NSULATED ENCLOSURE
TO
-<1^ AC
VACUUM/PRESSURE GAUGE
INLET
LEVEL
|HEATED LINE
5 ft.
TIMER
GROUND
LEVEL
FLOW
CONTROLLER
L.
(_ _
CANISTER
METAL BELLOWS PUMP
TO
SX** AC
TO
-"'V'' AC
THERMOSTAT
FLOW READOUT CONTROL UNIT
HEATER
• MAGNALATCH VALVE AND PULSE CIRCUITRY
" PARAGON TIMER MODEL 7008-00
f NUPRO VALVE
FAN
Figure 1. Schematic o( Canister Sampler
415
-------
90
80
70
60
50
40
a = 30 GAUGE NEEDLE
b = 500 seem TYLAN CONTROLLER
30
20
0
0
96
108
84
24
36
48
60
72
SAMPLE TIME, min
Figure 2. Flow rate profiles versus sampling duration for evacuated cannister with restrictors only.
416
-------
FRITTED ftlTER
NEEDLE VALVE
ON OFFVSLVi
CAMNISTER VALVE
~~~
oo
(a) Sampler schematic.
J L
-------
100--
>
•Q
a.
a
DICHLOROMETHANE
CHLOROFORM
I
FREON 11
H FREON 113
5.0
I
MUM
5 6 7 8 9
10
-- 5.0
TIME, a.m.
Figure 4. Variations in VOCs in lab air using sequential sampler.
-------
COMPARISON OF 0600-0900 AM HYDROCARBON COMPOSITIONS OBTAINED FROM 29
ci r its
Mean nonmethane organic carbon (NMOC.) compound concentrations are
presented for 0600-090U samples collected at 29 urban areas during the
summer period of 1984 and 1985. Considerable differences are observed in
those areas that have different volatile organic compound emissions.
Ranges of benzene and toluene concentrations are presented for the 29
urban areas. It appears that variation in the observed concentration
range is more evident for toluene than benzene. This observation suggests
that there may be more discrete sources fur toluene than benzene.
Willi am A. Lonneman
Gas Kinetics and Photochemistry Branch
Atmospheric Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC
Abstract
419
-------
Introduction
A sampling program for nontnethane organic carbon (NMOC) compounds
and the nitrogen oxides (NOx) during the 0600 to 0900 period was conducted
at several urban areas throughout the United States during 1984 and 1985.
The purpose of the study was to obtain NMOC and N0X information needed
to prepare State Implementation Plans for ozone control strategies. Actually
the cities participating in the study were identified in the Federal
Register (1) as non-attaininent areas for the National Ambient Air Quality
Standard (NAAQS) for ozone. The 0600 to 0900 sampling period was selected
to correspond with the guidance for the use of the Empirical Kinetic
Modeling Approach (EKMA) for photochemical ozone control (2). According
to the EKMA guidance, only 0600-0900 AM measurements of NMOC arid N0X are
required at one representative central urban site location in the area to
be modeled. There is also guidance for urban site location in terms of
representing the general NMOC and N0X emission patterns for the modeled
area (3). Ideally, because of EKMA site selection requirements, the NMOC
composition measured in the 29 urban sites reported here should represent
all stationary and mobile sources in these areas.
NMOC determinations at the 29 urban s;tes were obtained from 3 hour
integrated canister samples collected during the 0600-0900 AM period.
The air sample canisters were shipped to a central laboratory facility
located at Research Triangle Park, NC for total NMOC analysis using a
cryogenic preconcentration FID approach (4). The measurement approach
removed air and methane from the air sample permitting direct determination
of NMOC. This approach was selected based upon the unreliable and
inaccurate performance of continuous NMOC analyzers (5,6,/) typically
used for these measurements.
Approximately 10 to 20% of the air samples were analyzed by detailed
gas chromatographic procedures. Although the intent of the GC analyses
was for quality assurance (QA) of the preconcentration total NMOC-FID
approach, the detailed NMOC results are extremely useful for the evaluation
and comparison of the NMOC compositions in these 29 urban areas located
at diverse geographic areas of the United States. Some of the cities
sampled have major industrial activities located within the urban area.
Other cities have predominately vehicular NMOC emissions. Consequently
large variation in NMOC compositions are expected among the 29 cities
studied. Sampling during the 0600 to 0900 AM period provides only a
limited period to compare NMOC composition. However, this time frame
represents a period of active NMOC emissions and poor meteorological
ventilation conditions. As a result, highest levels of NMOC concentration
for these urban areas most likely occur during the 0600 to 0900 period.
The purpose of this paper is to compare NMOC compositions among
the 29 cities to determine similarities and differences. Ranges for
benzene and toluene are presented for the 29 sites since these compounds
are under investigation as suspected toxic compounds.
E xperimenta1
The sample collection device and analysis system used for the 1984
and 1985 studies have been published elsewhere (4). The publication
contains detailed information concerning the sample canisters, the sample
420
-------
collection device, the modified GC-FID system and the preconcentration
procedure. Actually the preconcentration direct FIU (PDFID) system
described in this publication is similar to the ambient air GC-FID procedure
without the GC column. The approximate 500 cc volume of ambient air
trapped in the preconcentration system improves the sensitivity of FID
system to measure ambient air NMOC concentration below 100 ppbC.
Details of the GC system (8) and the preconcentration procedure {9)
have been published elsewhere. GC column conditions including flowrate
and temperature programming conditions were identical for botn the 1984
and 1986 studies. These conditions were unchanged between studies in
order to directly compare 1984 and 1985 sample results. The column used
was a fit! m x 0.32 mm i.d. DB-1 fused silica column (J & W Scientific,
Cordova, CA). The helium carrier gas flowrate was maintained at 2-3
cm^/min. The column temperature conditions consisted of an initial 1 mi n
hold at -50°C followed by temperature programming at 8°C/min to a final
temperature of 200°C with a final hold time of 5 inin. Calibration of the
individual compound peaks were performed with a National Bureau of Standards
(NflS) 2.84 ppm propane in air Standards Reference Material (SUM) No.
1665b cylinder. A single response factor was used to determine all GC
peak concentration. This approach has been determined to be valid for
most hydrocarbon compounds (10). Canister samples were analyzed on the
GC system generally within 2 to 4 days after collection.
At least one sample from each of the 29 urban areas was re-analyzed
with chemical stripper columns (11, 12). A 4" x 1/2" stainless steel
column packed with Ag2$04 - H2SO4 on firebrick was used to remove all
aromatic peaks except benzene which is approximately 60£ removed. A
4" X 1/2" stainless steel column packed with HgS04 - H2SO4 on firebrick
was used to remove all olefins peaks from the air sample.
Results and Discussion
The availability of detailed NMOC composition for 29 cities for the
same calendar time period using the same GC analytical procedure 1s quite
unique. In the past comparison of organic compositions in various cities
consisted of using any available data collected over multi-year time
periods determined by quite different GC analytical procedures. Such an
approach can present serious problems when comparing complex chromatographic
results such as those found in urban ambient air situations. This is
particularly true for the comparison of the unidentified GC peaks observed
in all chromatographic analyses of urban ambient air. The use of a
single GC system, with air samples collected over a relatively short time
span, presents a unique opportunity for the comparison of NMOC composition
in these 29 cities. For the first time comparison among urban areas for
unidentified compounds can be made with sonie reasonable degree of accuracy.
The 29 urban sites studies are listed in Table I. Those cities
sampled in both 1984 and 1985 studies are identified with an asterisks
to the left of the name. Eleven sites were sampled both years with 7 of
these sites located in the State of Texas. The sites were assigned a
different site number in the two studies. These site numbers are only
important for following figures in which data results for the urban sites
are unidentified by these numbers. As can be observed a large diversity
nf urban areas were sampled. These included cities with large industrial
421
-------
sources, such as those in southeast Texas, to urban areas in which
vehicular sources predominatee, such as Washington, DC and Boston, HA.
Two criteria were used to select samples for GC speciation analysis.
First, the selected samples for all sites were equally distributed over
the entire sampling period. An attempt was made to select an equivalent
number of Monday, Tuesday, Wednesday, Thursday, and Friday samples to
avoid possible day-of-wet;k bias. Second, samples collected at sites that
experienced afternoon ozone which exceeded 0.12 ppm were selected. It was
anticipated that the GC analyses for high ozone days would be particularly
useful to the States for their modeling studies. The latter criteria may
result in a biased high average NMOC concentration for the GC samples at
these sites since usually high precursor concentrations are observed on
days of high afternoon photochemical ozone levels. However, NMOC emission
patterns are expected to be somewhat consistent on a day to day basis.
Consequently NMOC composition should not be significantly different on
these high ozone days.
Figures 1 and ?. show a comparison of mean NMOC concentration by site
for all samples analyzed with the POFID procedure with those selected tor
detailed GC analysis. The general comparability between the two measure-
ment procedures is quite reasonable for both the 1984 (Figure 1) and 1913b
(Figure 2) studies. Perhaps the three sites demonstrating the most
significant disagreement are site 1 (Akron, OH), Site I (f.lute, TX) and
site 14 (Miami, FL) all investigated during the 1984 study (Figure 1).
The mean NMOC concentrations obtained by the GC procedure for sites 1 and
14 (Figure 1) are approximately SOX lower than the means measured by the
PDKID procedure for all samples. The GC mean for site 7 (Clute, TX) is
approximately 40% higher than that measured for all collected samples
with the P0F10 procedure. There appears to be little explanation for
these significant variations. Samples were pre-selected by the same
criteria as the other 19 sites. Also no samples were selected at these
sites due to high ozone observations. Only three samples were analyzed
hy GC procedures at site 14 (Miami, FL) during the study period. Obviously
the GC mean at that site is not representative of the NMOC mean con-
centrati on.
The comparison of GC with PDF 1D means for all sites sampled during
the 1985 program (Figure 2) are much improved over the 1984 study. This
is primarily due to the greater number of GC analyses performed at each
site during 1985 program. The two sites that shnw significant disagreement
are the Philadelphia sites 13 and 14. The GC means are approximately 255.
higher than the PDFIO means. For these two sites during the 1985 study
pre-selection sample bias may be a legitimate explanation. Several sam-
ples were analyzed as the result of high afternoon ozone levels observed
in the Philadelphia area.
Year to year comparisons of NMOC mean concentrations can be made for
11 sites common to both the 1934 and 1985 studies by reviewing the data in
Figures 1 and 2. The only city showing a significant change was Beaumont,
Texas. In 1985 the mean NMOC concentrate of 1.9 pprrC is nearly double
the 1.0 ppm mean measured in 1984. None of the other 10 common sites
422
-------
showed such significant changes. It is doubtful that meteorological
changes over the one year period can explain such a significant increase.
It is more likely that the NMOC emission levels were increased at the
Beaumont site during 1985.
The number of GC peaks observed at the sites during both years
ranged from about 100 on low NMOC concentration days to more than 24U
peaks on the higher NMOC concentration days. Currently 6b of the GC
peaks have been identified and verified by retention time location of
pure hydrocarbon compounds. More than 175 peaks remain unidentified. In
an effort to determine the nature of these peaks, collected samples were
re-analyzed using stripper columns selective for the removal of olefin
and aromatic compounds. Using this approach an assignment of the unidentified
peaks as paraffinic, olefinic, and aromatic could be made. At least one
pair of stripper column analyses were performed for each urban site
studied during the 1984 and 1985 programs. No surprises were experienced
with comparison of stripper column results from site to site. Each
unidentified GC peak for all the urban site seemed to be the same type of
hydrocarbon compound. Using the hydrocarbon classification assignments
determined from the stripper column, total paraffin, olefin, and aromatic
percent compositions were determined for each site. These percents of
hydrocarbon compositions are shown in Figures 3 and 4.
In hoth Figures 3 and 4, it is apparent that paraffins are the most
abundant species of hydrocarbon at all sites ranging from bU to bOi of
the total NMOC. Aromatic hydrocarbons are typically the next most abundant
hydrocarbon type ranging from 20 to 3W of total NMOC. Olefins are the
least abundant class of hydrocarbon observed ranging from 15 to 2lft of
total NMOC. This general composition breakdown, however, is not observed
at the industrial-urban sites located on the southeast coast of Texas.
At site 7 (Clute, TX) during the 1984 study (Figure 3) tne percent olefin
level was higher than percent aromatic. Similar observations were made
for Clute (Site 5) during the 1985 study (Figure 4). Site 1 (Beaumont,
TX) showed a more abundant level of olefin than aromatic composition
during the 1985 study (Figure 4). In both the 1984 study (Figure 3) and
the 1985 study (Figure 4) equally abundant levels of olefins and aromaties
were observed at the Orange, IX and Texas City, TX sites. It is obvious
that the petrochemical industries in these areas have a significant
impact on the NMOC composition. The hydrocarbon composition in the urban
areas investigated in both studies appear to be quite similar. This is
not surprising since vehicular sources are expected to comprise the
largest percentage of NMOC emissions ir these areas.
The availability of detailed hydrocarbon compositional information
for these 29 urban areas provides a wealth of information to compare NMOC
emission sources affecting these areas. Mobile and industrial sources
typically have fingerprints or hydrocarbon patterns that discriminate the
NMOC composition. Also the availability of individual species information
enables one to compare concentration levels in these different areas.
This is particularly important when these individual NMOC compounds are
suspected as toxic pollutants such as benzene and toluene.
In Figures 5 and b are plotted mean, median, high and low concentra-
tions for benzene and toluene observed djriny the 1984 study. In Figure
5 the range between high and low concentrateons are not very large and are
423
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perhaps the result of meteorological differences between these two sample
days. Consequently the sources of benzene are suggested to be relatively
consistent during the 0600-0900 AM period. Tne ranges between high and
low at site 3 (Birmingham, AL), site 6 (Chattanooga, TN), and site 12
(Indianapolis, IN) are quite different and suggest that large discrete
benzene sources affect these sites. These periodic high values significantly
affect the mean concentration. This is observed by the comparison of the
mean with the median concentration. In Figure 6 large ranges between
high and low concentration are observed at more sites for toluene. This
would suggest that there are discrete sources of toluene periodically
affecting more of the urban areas. This is not unexpected since toluene
is a very common organic compound used as a solvent, and in many irianufacturing
processes.
Similar benzene and toluene observations can be made for the 1985
study (Figures 7 and 8). Again the range between high and low concentration
at several sites is perhaps a result of meteorological variations. Periodic
discrete sources of benzene are most evident at site ! (Beaumont, TX),
5ite 17 (St. Louis, MO), and Site 18 (Texas City, TX). Again, more
discrete periodic sources of toluene are evident in the range of high and
low concentrations (Figure 8).
Conclusion and Summary
The availahility of detailed hydrocarbon compositional information
for 29 urban areas sampled during the 0600-0900 AM period for two
summer periods and analyzed on one detailed GC system is unique. This
data base allows one to compare NMOC composition for a variety of urban
areas that have significantly different NMOC emission source patterns.
Using one GC system allows the comparison of unidentified compound peaks
between cities. In 1986 an additional 7 cities will be added to the list
of 29. These cities include Denver, CO, Salt Lake City, UT, New York
City, Chicago, Hartford, CT, Bridgeport, CT, and Tulsa, OK. Consequently
these comparisons will be even more extensive.
^EFE_R_EJ^CES_
1. Federal Register, Vol. 48, February 3, 1983, p. 4972.
2. U.S. Environmental Protection Agency, Guideline For Use of City
Specific EKMA in Preparing Ozone SIPS, Research Triangle Park,
NC, TFA^T51T72P5T)-02/, (19807"
3. U.S. Environmental Protection Agency, Guidance for Collection of Ambient
N on-Methan e Organic Compound (NMOC) Oat a fo r Use in 1962 Ozon~e~"$TF
Development and Network Design and Sitinq C7iteria for the NMCRT and NOy
Honi tors, Tesearch Tri a'ngl e Park, MtTTPTT5t)fT-B(T-OTl, (T980TT
4. U.S. Environmental Protection Agency, A Cryogenic Preconcentration-
Oirect FID (PDFID) Method for Measurement of NMUt in Ambient Air,
Research Triangle PaTlT, NC, EPA 600/4-85-063, (1985). ~
5. F. McElroy and V. Thompson, "Hydrocarbon Measurement Discrepancies
Among Various Analyzers Using Flame Ionization Detectors," U. S.
Environmental Protection Agency, Research Triangle Park, NC,
EPA-600/4-75-010, (1975).
424
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6. J. W. Harrison, M. L. Timmons, R. B. Denyszyn, C. F. Decker, "Evaluation
of the EPA Reference Method for the Measurement of Non-methane
Hydrocarbons," U. S. Envviromnental Protection Agency, Research
Triangle Park, NC, EPA-600/4-77-033, (1977).
7. H. G. Richter, "Analysis of Organic Compound Data Gathered During
1980 in Northeastern Corridor Cities," U.S. Environmental Protection
Agency, Research Triangle Park, NC, EPA-450/4-83-017, (1983).
8. F. F. McElroy, V. L. Thompson, D. M. Holland, W. A. Lonneman, and R.
L. Seila, "Cryogenic Preconcentration-Direct FID Method for Measurement
of NMOC: Refinement and Comparison with GC Speciation," OAPCA, in
Press.
9. W. A. Lonneman, "Ozone and Hydrocarbon Measurement in Recent Oxidant
Transport Studies," Proceedings of the International Conference on
Photochemical Oxidant Pollution and~~lTs~Ton"t"roTr~U. S. Environmental
FrotectTon Agency, Research TriangTe Pa'rk, NC, EPA-60()/3-/7-001a, p.
211-223, (1977).
ID. W. A. Dietz, "Response Factor for Gas Chromatographic Analyses",
Gas Chromatog., 5, p. 68-71, (1967).
11. D. L. Klostennan, J. E. Sigsby, "Application of Substractive Techniques
to the Analyses of Automotive Exhaust," Environ. Sci . Technol., 1, p.
309-314, (1967). ~ "
12. W. A. Lonneman, J. J. Bufalini, R. L. Seila, and R. L. Kuntz,
"Subtractive Techniques for Analyzing Natural Olefinic Hydrocarbon,"
J. Environ. Sci. Health, A18(4), p. 627-538, (1983).
425
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Table I. Urban Sites Sampled for Detailed NMOC Measurements During the
1984 and 1985 Studies
Site ID 1984 Site Number 1985 Site Number
Akron, OH
1
Atlanta, GA
2
—
Birmingham, AL
3
--
Beaumont, TX
4
1
Boston, MA
—
2
Baton Rouge, LA
—
3
Charlotte, NC
5
--
Chattanooga, TN
6
--
Ci nci nnati, OH
8
—
Cleveland, OH
__
4
Clute, TX
7
b
Dallas, TX
9
6
El Paso, TX
10
7
Fort Worth, TX
11
8
Houston, TX
—
9
Indianapolis, IN
--
Kansas City, MO
13
10
Lake Charles, LA
—
1 |
Miami, FL
14
—
Memphis, TN
15
--
Orange, TX
16
12
Philadelphia, PA (1)
1/
13
Phi 1adelphi a, PA (2)
--
14
Portland, ME
--
15
Richmond, VA
18
16
St. Louis, MO
--
1/
Texas City, TX
19
18
Wilkes-Barre, PA
20
--
Washington, DC
21
19
West Palm Beach, FL
22
--
*Sampled in both 1 984 and 1985 studies
426
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CJ
A
Pi
a.
b
a
«j
o
0
U
o
a
9
a
S
i>
J
1.5
1.4 -
1.3 -
1.2 -
1.1 -i
1 -
0.9 -
0.8 -
0.7 -
o.a -
o.a -
0.4 -
0.3 -I
0.2
0.1 -
0
I
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 10 17 18 19 20 21 22
NMOC (PDFID)
NMOC (GC)
Fiqure 1. Comparison of average mean concentrations obtained with
the PDFII) and
-------
70
60
50
40
30
20 -
10
1 2 3 4 5 6 7 ft 9 10 11 12 13 14 15 18 17 IB 19 20 21 22
^ParafflDB
fxW! ^Olefins
f//A XAromatlcs
Figure 3. Percentage paraffins, olefins, and aromatics composition
for the cities participating in the l'JB4 twenty-two cities
NMOC study.
u
o
tl
a.
70
60
50
40 H
30
20
10 -|
mf—m -
i 2 3 4 5 e 7 a e io ii 12 13 14 is is 17 ta is
H "Paraffins K33 %01eflns Y//A XAromatloa
Figure 4. Percentage paraffins, olefins, and dramatics composition
for the cities participating in the 198b nineteen cities
NMOC study.
428
-------
200
1 BO
180 H
170
160
ISO
140
130 -
1 so -
110
100
80
80
70 -
80 -
50
40
30
80
10
0
"i"—r —(—| — f-
12 3 4 5
u
t—i—r
£ *
} ' »
t — I"" J
u
7 a B io ii is n 14 is ie 17 ib is so 21 2a
Median
Low
nigh
Mean
Figure 5. Mean, median, high and low concentrations of benzene
observed at each city participating in the 1984 twenty-
two cities NMOC study.
500
400
SOD
200
100
~1 1 1 r- -1 -
I 2 3 4 6
Median
it
~ 1.
n
H
-T._ ,(—,—|—!—|—|—j—-f—-i— — f—r—1—r—
7 B fl 10 11 12 13 14 IS IS 17 IB IS SO 31 22
Low
High
Mean
Figure 6. Mean, median, high and low concentrations of toluene
observed at each city participating in the 1984
twenty-two cities NMOC study.
429
-------
0
200
190 H
ieo
170 H
160
150 -
140
130
120 H
110
100
90
BO H
70
60 -
SO -
40
30 -
20 -
10
0 -
i U *
,— f 1 T
:: I}
i
H •
n 1 n
~1—t —t—i r
~i—t—t—r—r-
7 8 9 10 It 12 13 14 15 16 17 IB 19
Median
Low
Hi jh
Mean
Figure 7. Mean, median, high and low concentrations of benzene
observed at each city participating in the 1985 nineteen
cities NMOC study.
300 -
280
200
240 -
220 -
d
o
A
H
200 -
m
(J
180 -
a
o
3
180 -
M
HO -
u
«
a
120
I
100
a,
80
80 -
40 •
20 -
0 -
9
?
i *
f
r i i
t ii
If
4
"T !
t i
1 2 3 4 5 6 7 a 9 10 11 J2 13 14 15 18 17 10 16
Median + Low o Hifh a Mean
Figure 8. Mean, median, high and low concentrations of toluene
observed at each city participating in the 1985
nineteen cities NMOC study.
430
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AN AIR SAMPLING SYSTEM FOR MEASUREMENT OF
AMBIENT ORGANIC COMPOUNDS
Dave-Paul Dayton, Robert A. McAllister,
Denny E. Wagoner
Radian Corporation,
Research Triangle Park, North Carolina 27709
Frank F. McElroy, Vinson L. Thompson
Environmental Monitoring Systems Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Harold G. Richter
Office of Air Quality Planning and Standards
Office of Air and Radiation
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
A system for automatic collection, transport, and temporary storage of
ambient air samples to be analyzed for concentrations of organic compounds
has been devised and extensively tested. The air sample collection
apparatus, which 1s designed for unattended sample collection at a remote
site, includes a metal bellows pump, critical orifice flow control, a timer
to start and stop sample collection, a noncontaminating solenoid valve, and a
special sample storage container. The system is specifically designed to
collect uniformly integrated air samples over a predetermined time period.
The integrated air samples obtained by the system are pressurized to
approximately one atmosphere gauge pressure and stored in electropol ished,
six-liter stainless steel canisters for transport and subsequent analysis.
Total nonmethane organic compound (NMOC) analyses and speciated organic
compound data indicated that most atmospheric organic compounds are stable
when stored in such treated canisters for periods of up to two weeks.
Following sample analysis, the canisters were readily cleaned for reuse by
repeated evacuation and flushing with cleaned, dried air. The canisters are
rugged and can be shipped repeatedly in special aluminum shipping cases. The
efficacy of the canisters and the entire collection system was proven in
field testing involving about 3,000 air samples collected at 31 sites in
various parts of the United States during 1984 and 1985.
431
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Introduction
In developing appropriate strategies to achieve compliance with applicable
ambient air quality standards for ozone it Is necessary to know ambient con-
centrations of precursor organic compounds and downwind concentrations of
1 ? 1
ozone. ' Some photochemical dispersion models require detailed organic
species data obtained by multlcomponent gas chromatographic analysis of air
2 3 1
samples. ' The simpler Empirical Kinetic Modeling Approach (EKMA) requires
total average NMOC concentration data, sampled from 6 A.M. to 9 A.M. daily.
The 1984 and 1985 NMOC Sampling and Analysis Program, described else-
where,^ was carried out to acquire and to validate data for modeling estimates
of hydrocarbon control requirements to be used in State Implementation Plans
(SIP's) for control of ozone In the participating localities. The program also
afforded an excellent opportunity further to study the performance and merit of
the Cryogenic Preconcentratlon, Direct Flame Ionization Detection (PDFID)
4
method, and further to compare the simpler PDFID method with the Gas Chroma-
tographic, Direct Flame Ionization Detection (GCFID) method.® The results of
the 1984 and 1985 NMOC Sampling and Analysis Program and the comparisons made
of the sampling and analysis methods are presented in another paper.^
The purpose of this paper is to describe the sampling equipment and
procedures used in the 1984 and 1985 NMOC Sampling and Analysis Program and
to present the methods and results used to test and validate that equipment.
Sampling Equipment Considerations
Collecting of valid ambient air samples is a critical aspect of any air
monitoring project, particularly when the samples will be stored and
transported before analysis.
The air sampling equipment used in this study was designed specifically
for the NMOC Program. However, the equipment and procedures described here
are also likely to be suitable for sampling ambient air for determining
concentrations of many specific organic compounds. Ambient air samples were
taken at 31 sites in the Gulf Coast States, Midwestern, and Eastern United
States and shipped by air freight to Research Triangle Park, NC for analysis.
Samples were usually analyzed the next day, except that Friday samples were
analyzed the following Monday. The time period between sampling and initial
analysis was never longer than 72 hours.
Primary concerns regarding the sampling equipment were to verify that
(1) the equipment did not contaminate the air sample collected, (2) the NMOC
concentration of the collected air sample was stable during the storage period
between collection and analysis, and (3) there was no significant carryover
from previously collected samples, i.e., the canisters could be adequately
cleaned and reused.
432
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Field Sampling Apparatus
The sampling system for the collection of Integrated field samples Is
shown In Figure 1. The sample intake port was an Inverted glass funnel
connected to 1/4-1nch (6mm) outside diameter (o.d.) chromatographic grade
stainless steel tubing. The optional auxiliary pump was used with long inlet
lines (over 4m) to ventilate the Inlet line and to ensure that the air at the
stainless steel tee was representative of the ambient air at the intake.
Sample lines leading from the tee to the sample canisters were l/8-1nch (3mm)
(o.d.) chromatographic grade stainless steel tubing. A fritted stainless
steel filter rated at Zfim pore size trapped particulate matter in the
ambient air sample and protected the critical orifice.
Flow control over the three-hour sampling period, from 6 A.M. to 9 A.M.,
was effected primarily by the critical orifice downstream of the filter. The
orifice was sized so that 1n the three-hour sampling period, the pressure in
the sample canisters was raised from vacuum to about 15 ps1 (100 kPa) gauge
pressure. When duplicate samples were taken, two canisters were connected to
the sampling system simultaneously. For those samples, the critical orifice
used for single canisters was replaced with a larger orifice having twice the
flow rate so as to fill two canisters 1n three hours.
The main pump, a stainless steel bellows pump (Metal Bellows Corp.,
Model MB151) was capable of maintaining sufficient vacuum on its intake to
sustain a critical pressure drop across the orifice, while pressurizing the
4
canister. Both critical orifices for single and duplicate samples and the
pump were tested, prior to field Installation, to verify that the flow rate
through the pump was essentially constant over the three-hour sampling
period. This flow control method also minimized internal heating of the pump,
which could contaminate the sample air.
A solenoid latching valve was Installed in the 1/8-inch (3mm) sample
line downstream of the MB151 pump, and connected to the timer. The timer was
set to turn on the two pumps and open the solenoid latching valve at 6 A.M.,
and to turn the pumps off and close the valve at 9 A.M. The stainless steel
solenoid latching valve, with V1ton® seats, provided a positive closure to
the canister, so that when the valve was closed, no vacuum was lost before
sampling and no sample air was lost after sampling. A special electrical
circuit was installed in the timer to provide current pulses to the solenoid
to open and close it. Unlike conventional solenoid valves the latching valve
required no continuous current to keep it open during the sample period. This
prevented heating of the valve during sampling, which could possibly cause out-
gassing from the valve or its seat, and contaminate the sample.
After the sample was collected, the site operator manually closed the
valves on the sample canlster(s) before disconnecting the cantster(s) from
433
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the sampling assembly. The site operator measured the canister pressure by
connecting the canister to a pressure gauge, and opening the canister valve
momentarily. The operator then reclosed the valve and disconnected the
pressure gauge before preparing the canister for shipment to the Research
Triangle Park (RTP) laboratory for NMOC analysis.
The sample containers were 6-Hter spherical stainless steel canisters
(Demarey Scientific Instruments, Ltd., Pullman, WA) with stainless steel
bellows valves (Nupro Co., Willoughby, OH). A small stainless steel base was
welded to the bottom of each canister, and a stainless steel valve guard was
welded at the top to protect the valve from damage in shipment and handling.
A Swagelok fitting was welded Into the sample port of the canister. The
manufacturer electropol1 shed the internal canister surfaces, using the Summa®
process (U.S. Patent No. 764462), to passivate adsorption sites. Similarly
processed canisters were used by Oliver,' e£ in their study on the
storage stability of volatile organic compounds in ambient air. Canisters
were shipped in aluminum shipping containers designed to hold two canisters.
Installation And Operation Of The Sampling Equipment
The field sampling apparatus was housed in an air conditioned facility.
The sample intake point, the inverted glass funnel in Figure 1, was located
outside the building about 7.6 meters above ground level. A checklist of
steps was used to verify the correct operation of the sampling equipment and
its proper assembly. The final step involved training the site operator, who
would connect and disconnect the sample canisters daily, Monday through
Friday. The daily routine of the site operator included checking the
operation of the sampling equipment assembly, checking the timer settings,
changing canisters, filling out field sampling forms, packing the canisters
along with the field sampling forms for shipment, and calling Radian's
Research Triangle Park Laboratory if unanticipated problems were encountered.
Canister Cleanup Apparatus
Canisters were cleaned in preparation for another sample by first evacua-
ting the canisters to a pressure of 5mm Hg absolute (667 Pa), followed by pres-
surizing the canisters to 40 pounds per square inch gauge (psig) pressure (276
kPa), with cleaned, dried air. This cycle was repeated three times. Tests in-
dicated that carryover of NMOC from one sample to the next averaged less than
0.10%.
Figure 2 shows the apparatus used to clean up to 12 sample canisters at a
time. An oil-free compressor with a 45-liter reservoir provided a source of air
for the system. The oil-free compressor assured a minimum of hydrocarbon con-
tamination. The compressor reservoir was drained of condensed water each mor-
ning. A coalescing filter provided water mist and other particulate removal
434
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down to a 5-micron particle size. Permeation dryers (Perma-Pure, Oceanport,
NJ) removed water vapor such that moisture indicators downstream of the
permeation dryers never showed any detectable moisture in the cleaned air.
The air was then passed through catalytic oxidizers (MSA Model B) to
destroy any hydrocarbons. One-micron inline filters were attached to the
outlets of the oxidizers. A single-stage gas regulator controlled the air
flow rate to the canisters as well as the final canister pressure. The flow
was measured by a rotameter installed in the dry air line. A shutoff valve
was installed between the rotameter and the manifold where the canisters were
connected for cleanup.
A bellows valve installed in the line between each canister manifold and
the vacuum pump regulated access of vacuum to the manifold. The cryogenic
trap between the manifold and the vacuum pump prevented any back diffusion of
hydrocarbons from the vacuum pump into the cleanup system or the canisters.
Canister Cleanup Procedure
After NMOC analyses were completed, six canisters were connected to each
manifold shown in Figure 2. The valve on each canister was opened, with the
shutoff valves and the bellows valves closed. The vacuum pump was started
and one of the bellows valves was opened, drawing a vacuum on the canisters
connected to the corresponding manifold. After reaching 5mm Hg absolute
pressure (667 Pa), the vacuum was maintained on the six canisters connected
to the vacuum manifold for 15 minutes. The bellows valve was then closed and
the cleaned, dried air was introduced into the evacuated canisters until the
pressure reached 40 psig (276 kPa). The canisters were filled from the clean
air system at the rate of 7.0 l/min, a flowrate specified by the
manufacturer as the highest flowrate at which the catalytic oxidizers would
handle elimination of hydrocarbons with a minimum 99.7% efficiency.
When the first manifold had completed the evacuation phase and was being
pressurized, the second manifold was then exposed to the vacuum by opening
the bellows valve. After 15 minutes of exposing the second manifold and
canisters to <5mm Hg absolute pressure, the second manifold was isolated from
the vacuum and connected to the clean air. The first manifold of canisters
was then taken through a second cycle of evacuation and pressurization. Each
bank of six canisters was subjected to three cleanup cycles.
In the third cycle, after the canisters had been pressurized to 40 psig
(276 kPa), the canister on each manifold that had contained the highest NMOC
concentration sample prior to cleanup was selected for cleanup testing. It
was removed from the manifold under pressure and analyzed for its NMOC content,
which averaged 1.5 parts per billion carbon (ppbC). If the analysis measured
less than 2.5 ppbC then all six canisters on the manifold were considered to
be clean. The canister that had been removed from the manifold for cleanup
435
-------
testing was reconnected to the manifold and all six canisters were evacuated
to <5mm Hg absolute pressure the fourth and final time. They were kept at
that pressure for 10 to 15 minutes, after which time, the canister valves
were closed, and the canisters were disconnected from the manifold and packed
into the shipping containers.
In the 1985 NMOC Program, all the canisters cleaned by the procedure
described above met the 2.5 ppbC criterion for cleanness after three cleaning
cycles. Per cent carryover was defined as the percentage of the NMOC contained
in an ambient air sample that remained after the canister was cleaned via the
cleanup procedure. Measured per cent carryover ranged from 1.16% to 0%, with
an average percent carryover of 0.10%. The overall average carryover was
probably less than 0.10% because the canisters were evacuated a fourth time
after the per cent carryover had been measured.
Important aspects of the 1985 NMOC study were (1) to investigate the
effect of the length of the storage time on the NMOC concentrations of an
ambient air sample in the sample canisters, and (2) to determine whether the
NMOC concentration was affected by the pressure of the sample In the canister
at the time of analysis. Two studies were done:
1. Radian selected 26 canisters at random during the summer program
for a sample degradation study. NMOC measurements were made on
each canister by the PDFID method seven days after the initial
analysis. On the 14th day after the initial analysis, one or more
analyses were done until the pressure in the canister fell below 5
psig (34.5 kPa).
2. Four canisters were selected from among the site samples for sample
degradation studies by the GCFID method. These studies were
conducted in the U.S. Environmental Protection Agency's Atmospheric
Sciences Research laboratory (EPA-ASRL). Seven days after the
initial analysis, the samples were reanalyzed. On the 14th day
after the initial analysis, the sample was analyzed three times.
Data for the Radian sample degradation study are given in Table 1;
similar data are given for the EPA-ASRL study in Table 2. Sample ID numbers
in Tables 1 and 2 were those assigned by Radian for each ambient air site
sample as It was prepared for analysis. The pressures recorded In the Tables
are the absolute canister pressures measured before each analysis. For each
sample, 2 to 5 sets of pressures and NMOC values are given. The first
pressure and NMOC value are the results from the first analysis. The second
pressure and NMOC value for each sample are the results for the second
analysis done seven days after the initial analysis. The rest of the
pressures and NMOC values for each group are the results for the Nth day
after the Initial analysis.
436
-------
To detect a possible change of the NMOC measured concentration upon
storage In the sample canisters for the two-week period after the Initial
analysis, the hypothesis that the mean of the second through the fifth (or
6th) NMOC concentration determination was equal to the first NMOC
g
concentration in each data set was tested. Two data sets, Sample ID Nos.
1399 and 1739, 1n Table 1 and one data set, Sample ID No. 2135, from Table I
show the NMOC mean after the first analysis to be different from the Initial
NMOC value at the 5% level of significance. In the first two cases, the
final NMOC mean was less than the initial value, and in the third case, the
EPA-ASRL results, showed the final mean to be greater than the Initial value.
To look for a pressure-related effect, correlation coefficients for the
linear relation of pressure as the independent variable, versus NMOC concentra-
tion, were calculated for each data set. Four out of the 26 data sets in the
Radian study (Table 1) showed a correlation coefficient significantly greater
O
than zero at the 5 percent level of significance. None of the EPA-ASRL
sample data sets (Table 2) showed a significant correlation coefficient for
the linear relation of pressure vs. NMOC. In Table 1, Sample ID Nos. 1486,
1738, 2129, 2150 showed significant correlation coefficients. It should be
noted for that Sample ID Nos. 1486, 2129, and 2150, NMOC values "increased"
4.3%, 11.8%, and 4.3%, respectively while for Sample ID No. 1738, the NMOC
value "decreased" 2.8%. It 1s also to be noted that 1n the linear correla-
tion with from 3 to 6 total data sets, the correlation 1s not a robust or
definitive measure because two degrees of freedom are taken by the constants
in the linear correlation. The amount of Increase or decrease of NMOC with
decreasing pressure 1s within the repeated error measurement of 10.5%,^ with
the exception of Sample ID 2129. This means that there is a significant
probability that the successively Increasing (or decreasing) NMOC values
could have occurred due to random variation.
The final point to be made Is that the Sample ID Nos. found to have NMOC
values differing significantly from the Initial value were different from the
Sample Nos. showing significant linear correlation coefficients with respect
to pressure.
There was no well defined Increasing or decreasing trend In the NMOC
concentration versus pressure or time after Initial analysis. For the few
cases that had a dlscernable trend the results were conflicting and small,
I.e., within the average error for the method. It was therefore concluded
that there was no significant NMOC concentration change (1) when the canister
pressure was decreased, and (2) when the ambient air samples were stored in
the canisters for a two-week period after the Initial analysis. These
results also supported the assumption that there was no change 1n the NMOC
concentration between the time of sampling and the time of analysis.
437
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Conclusions
The automated sampling system described, reliably collected integrated
ambient air samples suitable for NMOC or species analysis. The canisters
used in this study were rugged and utilitarian for collecting, storing, and
shipping air samples. The sample cleanup procedure was reliable and
effectively reduced average sample carryover to less than 0.10% from one
sample to the next. No significant NMOC concentration changes were related
to storage of the sample for up to 14 days, or related to pressure of the
sample air in the canister.
REFERENCES
1. U.S. Environmental Protection Agency, "Uses, Limitations, and Technical
Basis of Procedures for Quantifying Relationships Between Photochemical
Oxidants and Precursors." EPA-450/2-77-021 a (Nov. 1977).
2. U.S. Environmental Protection Agency, "Guidance for Collection of
Ambient Nonmethane Organic Compound (NMOC) Data for Use in 1982 Ozone
SIP Development." EPA-450/4-80-011 (June 1980).
3. H.B. Singh, "Guidance for the Collection and the Use of Ambient
Hydrocarbons Species Data in Development of Ozone Control Strategies,"
U.S. Environmental Protection Agency, EPA-450/4-80-008 (April 1980).
4. U.S. Environmental Protection Agency, "Cryogenic Preconcentration and
Direct Flame Ionization Detection (PDFID) Method for Measurement of
Nonmethane Organic Compounds (NMOC)," Environmental Monitoring Systems
Laboratory, Research Triangle Park, NC 27711 EPA-600/4-85-063 (October
1985).
5. R.A. McAllister, D-P. Dayton, D.E. Wagoner, "1984 and 1985 Nonmethane
Organic Compound Sampling and Analysis Program," APCA/U.S. EPA Symposium
on Measurements of Toxic Air Pollutants, Raleigh, NC, April 27-30, 1986.
6. F.F. McElroy, V.L. Thompson, D.M. Holland, W.A. Lonneman, and R.L. Seila,
"Cryogenic Preconcentration-Direct FID Method for Measurement of Ambient
NMOC: Refinement and Comparison with GC Speciation," J. Air Pollut.
Control Assoc.. submitted for publication.
7. K.D. Oliver, J.D. Pleil, and W.A. McClenny, "Sample Integrity of Trace
Level Volatile Organic Speciated Compounds in Ambient Air Stored in
Summa Polished Canisters," Atmos. Environ., in press.
8. N.L. Johnson and F.C. Leone, "Statistics and Experimental Design In
Engineering and the Physical Sciences," John Wiley and Sons, Inc., New
York (1964).
43B
-------
TABLE 1. SAMPLE DEGRADATION STUDY,
RADIAN RESULTS
Sample Pressure, NMOC,
ID No. psia ppmC
Sample Pressure, NMOC,
ID No. psia ppmC
Sample Pressure, NMOC,
ID No. psia ppmC
1642
33.7
28.7
26.7
29.7
0.440
0.420
0.362
0.386
1874
37.2
32.7
25.2
22.7
2.274
2.302
2.317
2.289
2363
32.7
27.7
22.7
16.7
0.840
0.938
0.807
0.932
1486
33.2
28.7
24.7
19.7
0.966
0.985
0.990
1.008
1318
32.7
26.7
22.7
19.2
0.154
0.178
0.202
0.179
2129
39.7
32.7
27.2
18.7
1.565
1.579
1.687
1.750
1399
32.7
25.7
19.7
0.984
0.425
0.426
1768
41.7
34.7
30.2
22.2
2.500
2.472
2.590
2.513
1470
33.7
26.7
22.2
17.7
0.965
1.050
1.014
0.990
1875
37.2
31.7
27.7
18.7
2.284
2.257
1.469
2.076
1848
33.2
27.7
23.7
17.7
1.557
1.544
1.532
1.579
1324
31.7
24.7
20.7
17.7
0.177
0.167
0.168
0.209
2305
31.7
28.2
21.2
1.084
1.110
1.189
2360
32.7
25.2
19.7
0.412
0.324
0.399
1738
31.7
27.7
22.7
0.675
0.663
0.656
1302
31.7
27.7
23.2
19.7
0.413
0.399
0.447
0.455
2635
18.7
31.2
27.7
19.7
0.651
1.071
0.959
0.947
1739
32.7
26.7
22.7
16.7
0.695
0.676
0.678
0.671
1847
33.7
29.7
26.2
22.7
20.7
0.460
0.449
0.458
0.438
0.438
1093
47.7
38.7
31.7
23.7
19.7
1.170
1.151
1.180
1.100
1.134
2203
33.7
28.7
24.2
23.7
18.7
0.852
0.825
0.934
0.882
0.795
2150
32.7
25.7
17.7
0.862
0.873
0.889
2322
26.7
25.7
20.7
0.208
0.187
0.230
1124
34.2
26.7
16.7
2.115
2.055
1.780
1000 47.7 1.076 2103 28.7 0.984
40.7 1.089 17.7 0.929
29.7 1.168
25.7 1.041
21.7 1.099
1LJ LIU
a 2
Pressure reported here is lb/in absolute pressure. Multiply by 6.894757 to
convert to kPa.
^There was a correlation of pressure and NMOC concentration at the 0.05 level
of significance.
cThe mean of the last two NMOC values Is significantly less than the first
NMOC value at the 5% level of significance.
dThe mean of the last three NMOC values 1s significantly less than the first
NMOC value at the 5% level of significance.
439
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TABLE 2. SAMPLE DEGRADATION STUDY,
EPA-ASRL RESULTS
Sample
ID No.
Pressure,
psia
NMOC,
ppmC
Sample Pressure,
ID No. psia
NMOC,
ppmC
2461
24.0
0.895
2151
25.5
0.815
23.7
0.890
21.8
0.839
22.2
0.931
18.7
0.802
20.7
0.897
16.7
0.808
16.7
0.884
16.2
0.834
213 5b
25.0
23.2
22.2
16.7
16.2
0.919
0.981
0.984
1.003
0.984
2323
21.2
20.2
19.2
16.7
15.2
0.204
0.204
0.174
0.173
0.171
a 0
Pressure reported here Is lb/In absolute pressure.
Multiply by 6.894757 to convert to kPa.
^The mean of the last 4 NMOC values 1s significantly
greater than the first NMOC value at the 5% level of
significance.
440
-------
tm
Oil
RHar
ArfiyMBI&l
figure 1. Sampling system for collecting integrated ambient air samples.
Ccatoflcln0 Fitter
Pftrmsaikwi Oryeis
Q* Shutotf V*lve
Six • Port Manifold
Six • Port Minlfcrfd
Turbomolecular
Vacuum Pump
Trap
Figure Z. Canister cleanup apparatus.
441
-------
1984 AND 1985 NONMETHANE ORGANIC COMPOUND
SAMPLING AND ANALYSIS PROGRAM
Robert A. McAllister, Dave-Paul Dayton, Denny E. Wagoner
Radian Corporation
Research Triangle Park, North Carolina 27709
Frank F. McElroy, Vinson L. Thompson
Environmental Monitoring Systems Laboratory
Office of Research and Development
U. S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Harold G. Rlchter
Office of Air Quality Planning and Standards
Office of Air and Radiation
U. S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
A Cryogenic Preconcentration Direct Flame Ionization Detection (PDF ID) method
was used to measure nonmethane organic compound (NMOC) concentrations in
about 3000 samples of ambient air from 31 locations in 14 States and the
District of Columbia during the Summers of 1984 and 1985. Air samples under
pressure where shipped air freight in electropolished stainless steel
containers and analyzed the next day, or the following Monday for Friday
samples. Analyses were done at Radian Corporation's Research Triangle Park
(NC) Laboratory on two dual-channel PDF ID instruments. A number of the
samples were also analyzed on the U. S. Environmental Protection Agency's
PDFID instrument in their Quality Assurance Division (EPA-QAD) laboratory,
and by a Gas Chromatographic Flame Ionization Detection (GCFID) instrument in
EPA's Atmospheric Sciences Research Laboratory (EPA-ASRL).
Repeated analyses of 155 of the field samples gave an average absolute
precision of 10.5% for the four Radian Channels. Audit sample analyses,
using propane concentration standards, showed that Radian NMOC concentrations
averaged 3.6% higher than the Research Triangle Institute's GCFID results,
that EPA-QAD NMOC concentrations averaged 3.9% higher than RTI's, and that
EPA-ASRL's results averaged 6.10% higher than RTI's.
Local ambient air samples were collected weekly and analyzed on each Radian
Channel, and on both EPA instruments. There was a 0.72% NMOC concentration
difference between Radian Channels, and a 5.6% within-laboratory coefficient
of variation. The EPA-QAD NMOC concentrations averaged 8.9% higher than the
Radian results, and there was a 7.7% between-laboratory coefficient of
variation. The EPA-ASRL, GCFID method gave NMOC values averaging 2.5% lower
than the Radian results.
NMOC concentrations for the combined 1985 data were reported In parts per
million carbon (ppmC) by volume, were lognormally distributed, ranged from
0.05 to 5.27 ppmC, and averaged 0.75 ppmC.
The study has provided an extensive data base of NMOC concentrations, and has
shown the PDFID method of analysis to be precise, accurate, and cost
effective relative to the GCFID method of analysis.
442
-------
Introduction
t 2
Photochemical dispersion models ' describe quantitative relationships
between ambient concentrations of smog precursor organic compounds and subse-
quent downwind concentrations of ozone. The models are used to determine the
degree of control of organic compound concentrations 1n air required to meet
applicable ambient air quality standards for ozone. Measurement of NMOC con-
centrations In ambient air Is required for the models. The Gas Chromatographic,
Flame Ionization Detection (GCFID) method has been one of the most accurate
and widely used methods for determination of the NMOC concentration 1n air.
A Preconcentratlon Direct Flame Ionization Detection (PDFIC) method was
developed and used In 1984 and 1985 NMOC studies to measure NMOC concentrations
In ambient air. The PDFID method 1s faster, simpler, and less costly to
operate than the GCFID speclatlon method of NMOC analysis. The purpose of
the NMOC studies was to assist the States In achieving the National Ambient
Air Standard for ozone by 1987. These studies also afforded an excellent
opportunity further to refine the PDFID method, to build a NMOC data base at
several key sampling sites In the United States, to test and validate the
equipment used, to determine the precision and accuracy of the sampling and
analysis, and to compare the simpler PDFID method with the GCFID method.
The purposes of this paper are to discuss quality assurance procedures
used to test and validate the sampling and analysis techniques, to describe
the NMOC data characteristics, and to Indicate the results of a quantitative
comparison between the PDFID method and the GCFID method. A description of
the sampling equipment and the procedures used to test and validate that
equipment are given elsewhere.^
The experience and data of the 1984 study were used to refine the experi-
mental design for the 1985 study. The results described below refer primarily
to the data obtained 1n the 1985 study.
Experimental Design
Photochemical smog and haze occur more frequently In the summer months and
the phenomenon 1s related to the NMOC and NOx content of ambient air. The
objective of the 1984 and 1985 NMOC studies was to obtain NMOC concentration
measurements during the 6 A.M. to 9 A.M. time period on days when the ozone
concentration was most likely to be the highest. These data can then be used
to develop NMOC control plans based on the Empirical Kinetic Modeling Approach
(EKMA).' All of monitoring sites chosen were in metropolitan areas, and
several were located near petrochemical facilities.
Integrated, 3-hour, ambient air samples were scheduled to be taken
during the Summer of 1985 at 19 sites from 6 A.M. to 9 A.M., Monday through
Friday, except on holidays. Sampling was scheduled from early June through
443
-------
September for most of the sites. The number of sample days scheduled for the
various sites ranged from 44 to 88.
The determination of precision and accuracy was an Important part of the
1984 and 1985 NMOC studies. Repeated analyses of some samples provided meas-
ures of analytical precision, while analysis of duplicate samples collected
simultaneously once every two weeks at each site gave overall sampling and
analysis precision results.
Electropolished, cleaned stainless steel canisters, under vacuum, were
shipped via air freight from Radian's Research Triangle Park (RTP) Laboratory
to each site. After sampling was completed, the canisters, filled with
ambient air to about 15 psig (103 kPa), were returned via air freight to
Radian's RTP Laboratory for NMOC Analysis the next day (or Monday for Friday
samples).
Each day the first two samples analyzed were reanalyzed on another of the
Radian analytical channels. These repeat measurements provided one measure
of the wlthin-Radian laboratory precision among the four Radian Channels
(Channels A, B, C, and 0). Another wlthin-Radlan precision was obtained from
the analysis of the local ambient samples discussed below. Two samples daily,
after being analyzed by Radian, were reanalyzed by the PDFID method 1n the
EPA-QAD Laboratory. Four samples daily, after analysis by Radian, were
reanalyzed by the GCFID method In the EPA-ASRL.
Each week, duplicate ambient air samples were collected In Raleigh, NC
and analyzed by both EPA Instruments, and by each of Radian's four channels.
This series of duplicate ambient air samples was the most direct comparison
of each channel's precision and accuracy relative to each other channel,
since each channel analyzed the same sample twice, counting the duplicate
sample. One of the duplicate local ambient samples was analyzed first by the
Radian laboratory and the other duplicate was analyzed first by the EPA-QAD
and ASRL laboratories. The purposes of this procedure was to test whether
the order of analysis by a particular laboratory showed any detectable bias
In the measured NMOC values.
Accuracy was monitored on four days each week on the Radian channels by
in-house quality control propane-1n-a1r samples. On Mondays, Tuesdays,
Thursdays, and Fridays, a mixture of propane (0.03 to 9 ppmC) In air was
analyzed by each Radian channel. Two external propane samples having
different propane concentrations, were used as the primary basis for
determining bias or accuracy for the four Radian PDFID channels, the EPA-QAO
P0F10 channel, and the EPA-ASRL GCFID channel. The Research Triangle
Institute's Center for Environmental Studies was chosen as the reference
laboratory 1n providing a basis for determining accuracy, or bias. Analysis
of the audit samples by RTI was done by the GCFID gas speclatlon method, the
same method used by EPA-ASRL.
444
-------
Analytical Technique
The PDFID method for measuring the NMOC compounds In ambient air Is
described by the EPA.* The Radian PDF 10 Instruments utilized a modified
Hewlett-Packard, Model HP-58B0, dual-FID chromatograph, along with the
auxiliary equipment shown In Figure 1. The 6-port value was Installed in an
auxiliary heated zone, and the sample trap Itself was located inside the
chromatograph's column oven. Figure 1 shows the valve setting for
introducing a constant volume of sample from the canister Into the cryogenic
sample trap, which was cooled with liquid argon. Once the sample had been
trapped, the 6-port valve setting was changed to bring the carrier gas (He)
through the sample trap Into the FID, the liquid argon was removed, and the
chromatograph's oven door was closed. The chromatograph's automatic program
then assumed control of raising the oven temperature, at a preset rate, which
released the trapped sample to the FID.
The dally calibration procedure began with an Initial zero (blank)
reading, followed by determination of a calibration factor, using propane of
a known concentration. At the end of the day, a zero reading and calibration
factor were again determined, and the calibration factor drift for that day
was calculated. The Initial calibration factor determined each day was used
to calculate NMOC concentrations for the day. The acceptance criterion for
the calibration factor measured at the end of the day was that 1f the largest
NMOC value measured for the day changed 1n the third significant figure to
the right of the decimal point, using the afternoon calibration factor, all
NMOC values calculated for that day would be adjusted, using an average
calibration factor for the day. This kind of a adjustment was never needed
In the 1985 NMOC program.
The zero response was determined by averaging the peak area responses in
area counts from two analyses of cleaned, dried air. An oil-free compressor
provided source air for the clean air system. The air was filtered and
permeation dryers removed water vapor. Catalytic oxidizers destroyed any
hydrocarbons contained in the air. Zero readings averaged less than 1.0
ppbC, mornings and afternoons. Calibration factor drifts ranged from -11.7 to
+7.7 percent, averaging +0.2* drift. The average of the absolute values of
the calibration factor drift was 1.6*.
nUQLUltl
The 1985 NMOC data are presented 1n Figure 2 as a stem-and-1eaf plot,''
along with statistics for the entire data set. The plot Is a frequency
histogram (rotated 90°) which plots the NMOC concentrations, sorted from the
smallest to the largest, and truncated to the nearest hundredth ppmC. The
stems are the numbers to the left of the vertical open space and the leaves
are to the right. As Indicated on the graph, the smallest NMOC value 1s 0.045
445
-------
ppmC, truncated to 0.04, and Is shown at the top of the plot as "0 4* In the
first sten and leaf. The second sten and leaf (or row) of the plot shows
"0 799", which describes the next three largest of the sorted NHOC values to
be 0.07, 0.09, and 0.09. The maximum NHOC value In the 198S study was S.267
ppmC, shown as "52 6" at the bottom of graph as the last stem and leaf. The
M shown In the vertical open space locates the stem and leaf containing the
median, which Is 0.603 ppmC for this data set. The "H's" 1n the stem-and-leaf
plot locate the stems and leaves containing the upper and lower hinges, which
are the NMOC values dividing each half of the sorted data Into quartlles.
Figure 2 suggests that the overall NMOC data approximately fit a log-
normal frequency distribution. Additional tests confirmed this hypothesis.
The mean NHOC value given 1n Figure 2 Is the arithmetic mean and Is 0.755 ppmC.
7 2
For the lognormal distribution the mean, a , equals exp(/t +
-------
Accuracy was monitored with four Internal propane standards per week
analyzed by each Radian channel. Average per cent differences between the
calculated and the measured NMOC concentrations of the Internal propane
standards ranged from -3.29% to 4-2.06% among the Radian channels. The
overall per cent difference for the four Radian channels was -0.69%.
External audit samples having propane concentrations of about 3 ppmC and
9 ppmC, respectively, were analyzed three times each by the four Radian chan-
nels, the EPA-QAD PDF ID Instrument, and the EPA-ASRL 6CFID speciation Instru-
ment. The average bias of the Radian results was +3.00%; EPA-QAD bias aver-
aged +3.88%; and EPA-ASRL bias averaged +6.00%, all relative to the RTI results.
Canister cleanup studies^ established that there was little carry-over
of NMOC from one sample to the next. Twenty-six sample degradation studies'*
by Radian and four by EPA-ASRL showed than NMOC samples from the field sites
did not change significantly 1n NMOC concentration over a 14-day period of
storage In the sample canisters after the Initial analysis.
Comparisons of Radian PDFID NMOC analyses with EPA-ASRL GCFID NMOC
analyses and with the EPA-QAD PDFID NMOC analyses are given 1n terms of
orthogonal regression statistics 1n Tables 1 and 2 and Figures 3 and 4.
Figure 3 compares the NMOC values determined by EPA-QAD PDFID channel with
the Radian NMOC results for the same site samples. Figure 4 gives a similar
comparison for the EPA-ASRL and the Radian NMOC measurements. Table 1 compares
the orthogonal regression statistics for the two curves. For Rad1an--EPA-ASRL
results the slope is closer to 1.000 than the Rad1an--EPA-QAD results. The
comparison of the regression results 1s further Illustrated in Table 2. Using
the slopes and Intercepts from Table I, EPA-QAD and EPA-ASRL NMOC predicted
values are calculated at 3 arbltlarlly selected Radian NMOC values which cover
most of the range of NMOC values measured In the 1985 NMOC study. It is seen
that the EPA-QAD NMOC values are less than the Radian NMOC values above 0.5
ppmC (because the slope of the regression line is about 0.942). For the EPA-
ASRL--Rad1an comparison, above 0.5 ppmC, the EPA-ASRL NMOC results are only
siightly higher.
Additional definition of the comparisons between and within laboratories
for the PDFID method, and the comparisons between methods for the PDFID and
the GCFID methods 1s given In Tables 3, 4, and 5, and Figures 5 and 6.
During the period of June through September 1985, duplicate local ambient air
samples were taken weekly and analyzed by each Radian channel, by the EPA-QAD
PDFIO Instrument, and by the EPA-ASRL GCFID instrument. Tables 3 and 4 show
comparisons made between each channel pair that analyzed each duplicate local
ambient a1r sample. Table 3 shows the results for the duplicate analyzed
first by the Radian Channels, and Table 4 shows the results for the duplicate
analyzed first by the EPA channels. The mean difference refers to the
average of the NMOC differences determined by the first-named channel of the
447
-------
pair and the second-named channel, I.e., (NMOCpa(j ^ f0r the
first row 1n the table. The third column refers to the standard deviation of
the differences and the 4th column gives the number of comparisons.
Table 3 shows the overall Radlan-to-Radlan, within-laboratory average
differences to be +0.0106 ppmC. The between Radian-laboratory and EPA-QAD-
laboratory differences average +0.0567 ppmC. The comparison between Radian
laboratory results and the EPA-ASRL results are between-NMOC-method compari-
sons and are shown In Table 3 to average 0.00365 ppmC. Table 4 shows similar
results for the duplicate local ambient sample that was first analyzed by the
EPA Laboratories, followed by analysis 1n the Radian laboratory.
These results are shown graphically 1n another way In Figures 5 ana 6.
In these figures, the mean ppmC differences are plotted for each channel
pair, along with the 95% confidence Intervals on the means. For the most
part, the comparison show mean differences not significantly different from
zero. Visual observation, confirmed by an analysis of variance, shows no
significant difference between the duplicate local ambient sample results.
There was likewise no difference between the duplicate sample NMOC results
that could be attributed to the order of analysis. The between-laboratory
results for the Rad1an--EPA-QAD PDFID determinations show the EPA-QAD results
to average significantly less than the Radian results, while the EPA-ASRL
NMOC results are slightly higher than the Radian channel averages. These
mean differences are summarized in Table 5, which show the Radian within-
laboratory differences to average less than 1.0*. The EPA-QAD NMOC
determinations averaged about 8.0% lower than the Radian NMOC results, while
the EPA-ASRL GCFID speclation method results averaged 1.6% higher than the
Radian PDFID NMOC measurements.
Conclusions
The results of the 1985 NMOC study show the PDFID method to have a bias
which averaged less than +4* with respect to propane standards using RTI's
NMOC measurements by the GCFID method as reference values. The overall
absolute values of the sampling and analysis precision averaged 12.4%, and the
absolute values of the analytical precision averaged 10.5%. The PDFID method
was shown to compare favorably with the GCFID speclation method, giving NMOC
values which averaged only 2% lower than the GCFID speciation method, well
within the precision of either method.
The PDFID method of measuring NMOC concentration 1s accurate, precise,
and cost effective relative to the GCFID speclation method, and should become
the method of choice.
448
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REFERENCES
1. U.S. Environmental Protection Agency, "Uses, Limitations, and Technical
Basis of Procedures for Quantifying Relationships between Photochemical
Oxidants and Precusors," EPA-450/2-77-021a (Nov. 1977).
2. U.S. Environmental Protection Agency, "Guidance for Collection of
Ambient Nonmethane Organic Compound (NMOC) Data for use in 1982 Ozone
SIP Development," EPA-450/4-80-011 (June 1980).
3. H.P. Singh, "Guidance for the Collection and the Use of Ambient
Hydrocarbons Species Data in Development of Ozone Control Strategies,"
U.S. Environmental Protection Agency, EPA-450/4-80-008 (April 1980).
4. U.S. Environmental Protection Agency, "Cryogenic Preconcentration and
Direct Flame Ionization Detection (PDFID) Method for Measurement of
Nonmethane Organic Compounds (NMOC)," Environmental Monitoring Systems
Laboratory, Research Triangle Park, NC 27711 (October 1985)
EPA-600/4-85-063
5. D-P. Dayton, R.A. McAllister, D.E. Wagoner, F.F. McElroy, V.L. Thompson,
and H.G. Richter, "An A1r Sampling System for Measurement of Ambient
Organic Compounds," 1986 EPA/APCA Symposium on Measurement of Toxic Air
Pollutants, Raleigh, NC, April 27-30, 1986.
6. John W. Tukey, "Exploratory Data Analysis," Add 1 son-Wesley Publishing
Company, Reading, Massachusetts. (1977).
7. J. Aitchison and J.A.C. Brown, "The Lognormal Distribution," Cambridge
at the University Press (1957).
449
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TABLE 1.
COMPARISON OF RADIAN AND
EPA ANALYSES; ORTHOGONAL
REGRESSION PARAMETERS
EPA
Channel
Slope
Intercept n
Correlation
Coefficient
QAD +0.941771 +0.066219 128 0.927851
ASRL +1.008515 -0.008069 281 0.948292
TABLE 2. COMPARISON OF PER CENT DIFFERENCES
OF RADIAN AND EPA NMOC ANALYSES AT
THREE CONCENTRATIONS.
Radian
PPMC
QAD
PPMC
ASRL
PPMC
EPA-QAD
% Diff.
EPA-ASRL
% Diff.
0.5
1.2
5.5
0.53710
1.19634
5.24596
0.49619
1.20215
5.53876
+7.42
-0.31
-4.62
-0.76
+0.18
+0.70
450
-------
TABLE 3. LOCAL AMBIENT SAMPLE
RESULTS, FIRST ANALYSIS
BY RADIAN.
Meana
Difference
Standard
Channel Pair
ppmC
Deviation
Number
Radian A-Radian B
0.0178
0.0381
12
Radian A-Radian C
0.0057
0.0351
12
Radian A-Radian D
0.0279
0.0376
12
Radian B-Radian C
-0.0122
0.0615
12
Radian B-Radian D
0.0101
0.0545
12
Radian C-Radian D
0.0223
0.0398
12
Average or Pooled Value
0.0106
0.0325
72
Radian A--(EPA-QAD)
0.0704
0.0829
8
Radian B--(EPA-QAD)
0.0481
0.0605
8
Radian C--(EPA-QAD)
0.0675
0.1069
8
Radian D--(EPA-QAD)
0.0408
0.0994
8
Average or Pooled Value
0.0567
0.0891
32
Radian A--(EPA-ASRL)
-0.0017
0.0570
9
Radian B--(EPA-ASRL)
0.0100
0.0726
9
Radian C--(EPA-ASRL)
0.0159
0.1034
8
Radian D--(EPA-ASRL)
-0.0096
0.1232
9
Average or Pooled Value
0.00365
0.09323
35
The mean difference is the average NMOC difference between the
first channel of the pair and the second channel, e.g., for the
first row it refers to the difference between the Radian Channel A
NMOC value and Radian Channel B NMOC value, - (NMOCR ^ A - NMOCR d B).
451
-------
TABLE 4. LOCAL AMBIENT SAMPLE ANALYSIS RESULTS,
FIRST ANALYSIS BY EPA LABORATORIES
Mean3
Difference
Standard
Channel Pair
ppmC
Deviation
Number
1st Analysis bv EPA Laboratories
Radian A-Radian B
-0.0123
0.0465
11
Radian A-Radian C
-0.0074
0.0410
11
Radian A-Radian D
-0.0047
0.0458
11
Radian B-Radian C
0.0072
0.0618
12
Radian B-Radian D
0.0112
0.0297
12
Radian C-Radian D
0.0040
0.0665
12
Average or Pooled Value
+0.00006
0.0503
69
Radian A--(EPA-QAD)
0.0628
0.0915
10
Radian B--(EPA-QAD)
0.0684
0.1031
10
Radian C--(EPA-QAD)
0.0670
0.1248
10
Radian D--(EPA-QAD)
0.0604
0.0949
10
Average or Pooled Value
+0.0646
0.1044
40
Radian A--(EPA-ASRL)
-0.0325
0.0809
10
Radian B--(EPA-ASRL)
-0.0254
0.0657
11
Radian C--(EPA-ASRL)
-0.0237
0.1047
10
Radian D--(EPA-ASRL)
-0.0279
0.0755
10
Average or Pooled Value
-0.02745
0.0830
31
The mean difference Is the average NMOC difference between the
first channel of the pair and the second channel, e.g., for the
first row it refers to the difference between the Radian Channel A
NMOC value and Radian Channel B NMOC value, - (NM0CR ^ A - NMOCR d B).
452
-------
TABLE 5. COMPARISON OF LABORATORIES
AND NMOC METHODS
Mean
Mean
NMOC
D1fference
Per Cent
Channels
Method
ppmC
Difference
Rad1an--Rad1an
PDF ID
0.0053
+0.7%
Radi an--EPA-QAD
PDF ID
0.0606
+8.0%
Rad1an--EPA-ASRL
GCFID
-0.0118
-1.6%
Estimated using 0.75 ppmC as the mean NMOC value.
453
-------
Absolute
Pressure Gauge
Low Pressure
Regulator
Vacuum
Valve —i
Sample
Valve
Vacuum Pump
He
Sample
Metering Valve
/ \
1.7 Liter
Reservoir
Vent
6- Port
Valve
Sample Injection
Glass Beads
By - Pass
Rotameter
Cryogenic
Sample Trap
Canister Valve
Liquid Argon
Air
Hydrogen
FID
Integrator -
Recorder
Sample Canister
Figure 1. Schematic diagram of system for analysis of total nonmethane hydrocarbons
by cryogenic preconcentration and flame ionization detection.
-------
Smallest value at top of plot is: 0 045 ppmC
cn
CJl
5
3
G
6
7
7
e
a
9
9
10
10
11
11
12
12
13
13
17
18
IS
2C
21
22
23
24
25
a
27
28
29
JC
31
32
33
36
37
12
799
00111 12222 23333 34444 4
55566 6666666677 7777 7 77777 88899999
00000 00011 11111 11111 11122 2222222333 33333 4333344444 *4444 44
56555 55555 55566 66666 66666 67777 77777 77777 788888 68888 68899 9999999989
0000001111 11111 11111 11122 22222 22222 22223 33333 33333 33333 35333 4*444 44444 44444 44444 4
55665 S5565 55555 55556 66666 66666 66666 66687 77777 77777 77777 77777 78888 68888 88888 80009 99980 99999 090
H 00000 00000 00000 00000 00C111111111111 11111 12222 2222222222 2222222222 22222 22222 33333 33333 33333 34444
56655 56555 56565 5566666666 66686 77777 77777 77777 77777 77777 88888 888868888888888 88999 98999 990909909990009 9999999
00000 00000 OOOOO 00111 11111 1111111111 12222 22222 22222 22223 33333 33333 33333 33444 44444 4444
56666 69655 55455 66686 6668868886 68677 77777 77777 77777 77788 88686 88888 89999 99999 99
M 000000000001111 11111 11111 22222 22222 2333333333 33333 44444 44444 44444 444
------ - J--» n HJ ¦ »-»-» AA7T7 »|11 MflU Mmm »«*«* »*wwwi maq
Trrfvinj JUUW OQQDO WJWI DC r n Mr// rOMO OOOOO ODOPQ fUffVV VMW vm
000000000000000 11111 111 tl 1111! 11111 11112 22222 22222 23333 33333 33333 33334 44444 44444 44
rr — — - ^ - AJLTT1 7TTT7 TBOfHI n
3JMP JJOtO WWW UUWU OPOOlt OC f • r / M / / /DODO WWW fWW WWW »
00000 00111 11122 22222 22233 33333 33344 44444 44
ufu 7777Q iwwi Ms
TTi f i' 1 jP33Q JUUUO / 0 I t O WUftf ffJJ/w TV
H 0000000011 1111111122 22233 33333 33344 44444 444
55555 55656 66666 66677 77777 778888999999
00111 11112222223333333444 444
56555 56566 66666 66677 77778 88899 99999 9
00111 12222 22233 33344
55677 889999
OOOC1 11122 22222 344
55566 66667 77777 77776 8899
00011 12222 23334 4444
55656 6666 7 788889
011112233334444
678
00C11 2223344444
56667 786
00C12 233
67/77 68
00123
33566 77B
00123 35566676
01113 34457 689
01125 79
1123567
22467 789
46T7B
12589
255669
468
0*67
6
37?
56
7
08
4
e
7
6
NMOC.ppmC
N OF CASES
1500
MINIMUM
0.045
MAXIMUM
5.267
MEAN
0.755
MEDIAN
0.603
STANDAR0 DEV
0.541
SKEWNESS
2.166
KURTOSIS
7.232
Figure 2. Stem-and-leaf plot of NH0C data.
-------
ANALYSIS COMPARISON — RADIAN vs. QAD
(Orthogonal Regression)
2.2
2 0
O
06
0 4 -
02
0 0.4 OS 12 16 2.0 2 4
RACHAN NMOC PPMC
Figure 3. Cooparlson of Ridfan P0FI0 intlyiet with EPA-C|u»lity Anurance
DWIiion POfID rtsulti.
ANALYSIS COMPARISON - RADIAN vs. ASRL
(Orthogonal Ragresslon)
e
5
4
3
2
1
0
4
2
0
RADIAN NMOC PPMC
Figure 4. Comparison of Radian PDF 10 iralyils with EPA-At»ospherlc Sciences
Research Laboratory GCF10 results.
456
-------
Local Ambient Sample Results
Radian 1*t Analysis • EPA 2r*j Analysis
0 20 -
0 is •
010 -
OOB
RADIAN C RADIAN D
ppmC span lof Mch DPA^ Numb«r !• (ha 96*A conHd*nc«
tni«Y« «Oou< fta im*n viIin
EPA
GAP
EPA
ASRt
waw
RAOIAN A
RADIAN-B
RADiANA
RAOIAN C
3
RAOIAN-A
RAOIAN 0
RADIAN A
EPA QAO
RAOIAM A
EPA-ASRL
S
RAOIAN B
RADIAN C
RAO AM B
RADIAN 0
RADIAN B
EPA QAO
9
RAOIAN 8
EPA-ASRL
10
RACHAN C
RAOIAN 0
11
RAOIAN C
EPA GAD
12
RAOUN C
EPA- asrl
13
RADIAN D
EPA-QAO
14
RAOIAN 0
EPA-ASRL
15
EPA QAO
EPA-ASRL
1 r r r 7 r » I
1 2 3 4 5 6 7 8
OPAfRNumter
' "f '1 * I* I r * >
10 11 12 13 14 15
Fi|vr« S IouthJ roblr> i*«tys«i, first antlyitt by (Udlsn-
Local Ambient Sample Results
EPA 1st Analysis - Radian 2nd Analysis
RADIAN C RADIAN 0
I I
EPA
QAO
ppmC ip*n tor MCti DPAiR Humbert! 1h« M% conftd*nc«
inUfvii iCouf th« imin value
1 EPA-
, ASflL
10 11 12 13 M 15
DPAffl Number
OP AiR
NUMBER
CHANNEL PAIR
RADIAN
A
- RADIAN 6
RAOIAN
A
- RAOIAN C
3
RAOIAN
A
- RADIAN D
RADIAN
A
- EPA QAD
RAOIAN
A
- EPA Asm
8
RADIAN
B
- RAOIAN C
RAOIAN
B
- RAOIAN D
RAOIAN
B
- EPA QAO
RAOIAN
B
• EPA ASRt
10
RAOIAN
C
- RAOIAN 0
11
RAOIAN
C
- EPA QAO
12
RAOIAN
c
- EPA-ASRL
13
RAOIAN
D
- EPA OAD
U
RAOIAN
D
• EPA-ASRL
1&
EPA•QAO
- EPA ASRL
Figure 6. Round robin tnilysss, first artslysas by tPA.
457
-------
SELF SERVICE STATION VEHICLE REFUELING EXPOSURE STUDY
Andrew E. Rond, Vinson L. Thompson, Gordon C. Ortman
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Francis M. Black and John E. Sigsby, Jr.
Atmospheric Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Abstract
A four-day, ten vehicle study was conducted to quantify the concentration
and composition of gasoline vapor at five fixed distances from a single
island refueling point during February 1985, in Raleigh, N.C. Liquid and
vapor grab samples were collected to identify and quantify the specific
components of a commercial unleaded regular gasoline and associated refueling
vapors. This study also provided information as to the potential individual
exposure during self-service refueling operations. Vapor samples were
collected in evacuated six-liter stainless steel canisters at five fixed
distances from the vehicle refueling intake point. The sampling was conducted
under three different wind directions relative to the vehicle intake point.
Meteorological data (wind speed, wind direction, temperature, and relative
humidity) was collected at the study site during all sampling periods.
Vapor samples were analyzed hy both cryogenic preconcentration direct f1 aire
ionization (PD-FID) and by gas chromatography/f1ame ionization detection
(6C-FID) for total non-methane organic carbon. Analysis by GC-FID also
provided a detailed hydrocarbon profile (82 compounds) for all liquid
samples and vapor samples greater than 20 parts per million as carbon (ppm C).
458
-------
Int roducti on
On August 8, 1984, EPA announced in the Federal Register the
availability of a document prepared by the Office of Air Quality Planning
and Standards (OAQPS) describing the risk analysis and control options for
gasoline vapors*. This document indicated that although there are several
sources of public exposure to gasoline vapors, eighty percent of the estimated
cancer incidence was due to exposure during self-service refueling of motor
vehicles. Estimates of typical exposure during self-service refueling were
made from a limited amount of data taken from a report prepared by Clayton
Environmental Consultants (CEC) for the American Petroleum Institute (API)^.
Unfortunately, the Clayton report did not describe many of the key variables
that could influence exposure (e.g. distance from the pump nozzle to the
breathing zone of the exposed person, wind speed, wind direction). A
limited amount of data was also available from the City of Philadelphia^.
The City of Philadelphia's data indicated that such variables can account
for orders of magnitude changes in exposure.
OAQPS requested assistance from the Environmental Monitoring Systems
Laboratory (EMSL) at Research Triangle Park in an effort to expand the
limited data base which describes the exposure to and composition of gasoline
vapor concentrations associated with self-service refuelings. EMSL and
OAQPS jointly developed a limited four-day study design based on what could
be reasonably accomplished by EMSL with in-house personnel and equipment
resources, and utilizing analytical support from the Atmospheric Sciences
Research Laboratory (ASRL).
The principal objectives of this study were: (1) to quantify the
concentration and composition of gasoline vapor at fixed distances from the
refueling point, and (2) to identify and quantify the specific components
of commercial unleaded regular gasoline in a vapor and liquid phase.
Experimental Methods
A. Site. EMSL obtained the use of the North Carolina Department of
Administration Motor Fleet Management Garage on Blue Ridge Road, Raleigh,
N. C. as the study site. This location was selected because it contains a
single pump island, refuels with only unleaded regular gasoline and contains
a large pool of available vehicles requiring daily refuelings. A "study"
vehicle was defined as one that requires refueling from the right or left
rear side, uses unleaded regular gasoline, and is a sedan design. The
vehicles used in this study were either Plymouth Reliant "K" (Model Year
1981-83) or Mercury Zephyer (Model Year 1980).
Meteorological monitoring was conducted during all sampling periods
with a mechanical weather station (Model 1076 Meteorology Research, Inc.
(MRI)). The MRI station was used to collect data on wind speed,wind direc-
tion, and temperature. Relative humidity data was obtained by the use of a
psychrometer (Model 566 Bendix Environmental Science Division). The MRI
station was located forty feet from the pump island and the measurements were
obtained at an elevation of six feet above ground level. The separation
distance (40 feet) from the pump island was necessary to obtain an adequate
indication of wind speed and direction without being influenced by the
garage or pump island facilities.
B. Samp!ing Approach. Sampling was limited to periods when the wind
speed was no greater than twelve miles per hour (IE mph), the ambient tempera-
ture was above freezing (0° Centigrade) and no forecasted precipitation.
During the four days of sampling all vehicles were obtained from the vehicle
pool located at the Motor Fleet Garage. These vehicles had been parked in
459
-------
the lot at least overnight and were selected based on refueling intake point
location and indicated volume of gasoline in the tank reservoir by the
gasoline gauge. Only vehicles with an indicated gasoline volume of <_ one
fourth tank were selected for use in the study. As a result of the overnight
parking all vehicle gasoline tank temperatures approximated the ambient
temperature.
Three types of gasoline samples were collected during each sample day.
They were vapor, liquid, and bulk liquid samples. Vapor samples were
collected in evacuated six-liter stainless steel canisters at five fixed
distances from the vehicle refueling intake point during a ninety second
refueling period (Figure 1). A daily background vapor sample was collected
in the breathing zone "A" (BZA) position prior to the commencement of any
other sampling. Immediately following the collection of the background
sample the temperature of the vehicle tank reservoir was obtained by removing
the gas tank cap and inserting a temperature probe (Model 5650 Digital
Thermometer, Markson Scientific, Inc.) into the tank reservoir.
The fixed distance vapor grab sampling was conducted under three
different wind directions relative to the vehicle intake point. They were
parallel, perpendicular, and reverse parallel (Figure 2).
Liquid samples and bulk liquid samples were collected from the pump
nozzle immediately following the refueling operations on the last study
vehicle for each sample day. Two types of liquid samples were necessary
due to differing analytical techniques and laboratories involved in their
analysis. Liquid samples were collected in four milliliter glass conical
reaction vials with twin septum mininert® caps (Wheaton Inc. and Dynatech
Inc.) and stored on ice for the return trip to the laboratory. These
samples were collected and analyzed to provide a detailed hydrocarbon
profile of the study site gasoline. Bulk liquid samples (aproximately 0.8
gal.) were collected in a stainless steel can and also stored on ice for
the return trip to laboratory. Bulk liquid samples were collected and
analyzed to monitor the gasoline's Reid vapor pressure (RVP). Upon return
to the laboratory and until analyzed the bulk liquid samples were stored at
5°C and the liquid samples at -10°C. The study site was supplied with fuel
under contract to the State of North Carolina from Texaco, Inc. On the 1st
and 19th of Fehruary 1985, the station was supplied with fuel (approximately
8850 gallons on each occasion).
C. Sample Col lection. Specific sampling points were selected perpen-
dicular to the vehicle's refueling intake point. These points are defined
below and can be located on Figure 1. Emission Point (EP): located at a
distance of six inches from the refueling intake point and at the same
elevation above ground level. Breathing Zone Point A and B (BZA and BZB):
located at a distance of two feet from the refueling intake point and at an
elevation of five feet above ground level. The breathing zone position was
selected as the approximate location of an individual during a refueling
operation. These samples were simultaneously collected (for duplicate
analyses) through a common intake connected by six inches of stainless
steel tubing. Profile Sampling Points (PS5, PS7, and PS9): located at
distances of five, seven and nine feet fron the refueling intake point and
at an elevation of five feet above ground level. Utilizing a perpendicular
orientation of the sampling support frame to the vehicle intake point,
sampling was conducted under three different wind orientations, A parallel
wind configuration was defined as a wind blowing from the direction of the
fuel intake point and along the axis of the vapor sampling frame. A perpen-
dicular wind configuration was defined as a wind blowing across the axis of
the vapor sampling frame. A reverse parallel wind configuration was a wind
blowing toward the fuel intake point and along the axis of the vapor sampling
460
-------
frame. Four refueling operations were conducted under a parallel and
perpendicular wind configuration and two refueling operations under a reverse
parallel wind configuration. During each of the refueling operations an
individual held the pump nozzle in place during the ninety second period in
order to regulate the pump rate and to minimize spills. The position
occupied by the attendant during the refueling operation was adjacent to
the sampling apparatus and such that it minimized the blocking of the air
flow around the emission point.
The six-liter canisters used in this study were manufactured by Demaray
Scientific Instruments, Ltd., Pullman, WA. These canisters contain an
electropolished interior (Summa® treatment) and were equipped with a leak
free shutoff valve (Nupro® Model SS4H). The attachment position on the
sampling frame was equipped with a two liter per minute stainless steel
critical orifice (Model XX5000020, Millipore Corp.) to maintain a constant
flow rate during sampling. The orifice was attached to a stainless steel
Whitney® toggle valve to facilitate the manual opening and closing of the
canister valve during sampling. Prior to use in the field all canisters
were leak tested by pressurization to thirty-five pounds per square inch
absolute (35psia) with zero air. Following leak testing ail canisters were
cleaned and assigned sample numbers. The canisters in groups of five were
cleaned by attachment to a metal vacuum manifold and evacuated for a four
hour period. A cryogenically-cooled trap of liquid Argon was placed in the
vacuum line to eliminate the possibility of back-diffusion of hydrocarbons
or oil from the vacuum pump. Following the evacuation procedure twenty
percent of the canisters were pressurized to 35 psia with zero-grade com-
pressed air passed through the liquid Argon cryogenic trap. The pressurized
canister was then analyzed on a preconcentration direct flame ionization
detection (PD-F1D) system for a check on the background total nonmethane
organic carbon (NMOC). The maximum allowable background level of total
NMOC established for this study was no greater than 0.01 parts per million
as carbon (ppm C). In the event this standard was not achieved, all canisters
in the group were re-evacuated for an additional four hours and re-analyzed.
All canisters used in this study were cleaned with the above procedure and
met the established standard.
After field sampling and upon return to the laboratory the canisters
containing the vapor samples were attached to a pressure gauge and an
ending pressure was recorded. The canisters were then pressurized to 35
psia with zero-grade air passed through a cryogenic cold trap. The dif-
ference in absolute pressures recorded from each canister enables the analyst
to calcualte the Dilution Factor (DF) associated with each sample collected.
This calculation is shown below:
DF = Final Pressure psia e.g. 34.95 psia = 4.21
Sample Pressure psia-Initial Pressure psia (8.40-0.1Q)psia
The canister analytical concentration (ppm C) would then be multiplied by
the dilution factor to determine the total NMOC concentration. D.F. x
Analytical ppm C = Total NMOC concentration in parts per million as carbon
(ppm C).
D. Sample Analysis. Total NMOC and speciated data was developed on
all liquid samples and on as many vapor samples as possible. Two similar
techniques were selected to provide an analytical comparison. Initially,
all vapor samples were analyzed by cryogenic preconcentration direct flame
ionization (PD—FID}^and then by gas chromatography/flame ionization
taction (GC-FID)\if possible. Liquid samples were only analyzed by
-FID. The bulk liquid samples were analyzed by the North Carolina Depart-
ment of Agriculture, Standards Division, Fuels laboratory located in Raleigh,
461
-------
N.C. The chromatographic system precision required canister total NMOC
concentrations greater than 5 ppm C, which with dilution equated to about
20 ppin C ambient concentrations.
Results
The parallel wind configuration based data is emphasized in the
following discussion as illustrative of the higher concentrations observed
in this study.
Table 1 summarizes the meteorlogical and gasoline volume data collected
during the four-day study. Table 2 profiles the average NMOC concentration
values for the four refuelings conducted under a parallel wind configuration
and the expected benzene exposure reported as ppm C. Table 3 summarizes
the levels of exposure to NMOC at the breathing zone position under the
three wind configurations. Table 4A contrasts the composition of both the
liquid fuel and vapor samples collected under a parallel wind configuration.
Table 4B shows the breathing zone fraction greater than and equal to carbon
number six for the gasoline and the refueling vapors.
Figures 3A and 3B graphically compare the detailed hydrocarbon compositions
of the fuel and the vapor at the breathing zone position under a parallel
wind. Percent aromatic, parrafin, and olefin compositions are also shown.
Conclusions.
The limited data collected in the short term study indicates that the
level of exposures to NMOC during refueling operations is similiar to data
reported in earlier studies.2»3 The effect of wind direction shown by the
significant drop in exposure at the breathing zone position may explain the
differences reported in the City of Philadelphia Study. The detailed
hydrocarbon composition data indicates that the exposure during refueling
is predominately volatile C4 & C5 hydrocarbons.
The evaluated stainless canisters used in this study provided an
extremely stable and safe storage container for the vapor samples collected
in this study. The canister cleanup procedure used demonstrated that NMOC
concentrations as high as 10,000 ppm C created no background contamination
to the study canisters.
A copy the complete report containing detailed hydrocarbon and additional
NMOC data from all five sampling points is available from the authors.
Acknowledgement
The authors wish to acknowledge the excellent analytical support
provided by il. Duncan and W. Crews, Northrop Services, Inc., Research
Triangle Park, N. C.
462
-------
REFERENCES
1. "Evauation of Air Pollution Regulatory Strategies for Gasoline Marketing
Industry," Office of Air and Radiation (ANR-443), EPA-450/3-84-012a (1984).
2. J. Singh, "Gasoline Exposure Study for the American Petroleum Institute,
Washington, D.C. CGC Job Jo. 18629-15." Clayton Environmental Consultants,
Inc. (1983).
3. K. Ellis and R. Obendonfer, "Survey of Benzene Concentrations in Ambient
Air," Air Management Services, Philadelphia Dept. of Public Health
(1984).
4. Dimitriades, B. and D. E. Scizingen, "A Procedure for Routine Use in
Chromatographic Analysis of Automotive Hydrocarbon Emissions," Environ.
Sci. Techno!., 5: p. 223 (1971 ).
5. "Determination of Atmospheric Nonmethane Organic Compounds (NMOC) by
Crygenic Preconcentration and Direct Flame Ionization Detection,"
Quality Assurance Division, EMSL, RTP, NC (1983).
6. F. McElroy and W. A. Lonneman, "Cryogenic Preconcentration - Direct FID
Method for Measrement of Ambient NMOC: Refinement and Comparison with
GC Speciation," EMSL and ASRL, RTP, NC (1984).
TABLE 1. METEOROLOGICAL & GASOLINE VOLUME DATA
Wind
Relative
Average Gasoline
Sample
Speed
Wind
Humidity
Temp.
Sampling
Volume Pumped
Date
(mph)
Direction
(%>
<-C)
Configuration
(gal)
02/07
9.0
NE
41
4
Perpendicular
10.6
02/11
6.5
SW
30
13
Reverse Parallel
9.1
02/20
4.5
SE
69
14
Parallel
8.9
02/26
3.0
NE
77
16
Perpendicular
10.2
4G3
-------
TABLE 2. AVERAGE EMISSIONS UNDER PARALLEL WIND CONDITION
Total NMOC (ppm C|
benzene (ppm C)
EP
6.313 ± 1877
63 J 21
BZA
110 + 26
1.4 ± 0.4
BZB
108 + 27
1.4 + 0.5
PS5
47 » 20
0.56 ¦+ 0.3
PS7
36 ± 18
0.40 1 0.3
PS9
24-12
0.36 1 0.2
TABLE 3. BREATHING ZONE CONCENTRATION AS
FUNCTION OF WIND DIRECTION
Wind NMOC (ppm C)
parallel (4.5 mph) 109 i 27
pcrpundicutar (9.0 mph) 9.2 1 12.4
reverse parallel (6.5 mph) 0 33 t 0.1
TABLE 4A. COMPOSITION OF BREATHING ZONE VAPORS
Volume %
Aromatic Benzene Toluene Olefinic ParaHinic
Vapor 5.6 1.2 1.3 139 00.5
Fuel 48 2.0 7 3 7 45
TABLE 4B. BREATHING ZONE FRACTION >C6
Vapor 186
Fuel 8/4
464
-------
DISTANCES: 1t
INLFT W/ORIHCE
NEEDLE '*JL\
VALVE /pS7)
ll*S9!
COLLECTION
SPHERE
(EPI
SUPPORT FRAME
ADJUSTABLE
HEIGHT
Figure 1. Selected sampling points.
PUMP
¦v-y
RtVf USE PARAI I EL <£ W1NOS PAHALLfl
MCT
station
PERPENDICULAR
Figure 2. Wind directions during sampling.
465
-------
20-
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466
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PRA71 0O71 <5
iiiiiiiiiiniiiii
PART 2 OF 2
COMPUTER ASSISTED INTERPRETATION OF
GAS CHROMATOGRAPHY/MASS SPECTRAL DATA
FROM COMPLEX MIXTURES
VI. J. Dunn III and S, Emery
College of Pharmacy
University of Illinois at Chicago
8 3 3 S. Wood Street
Chicago, Illinois 60612
The analytical method of choice for determining the composition
of complex mixtures, as observed in the EPA's air quality
monitoring program, is gas chr om a togr a ph y /ma ss spectrometry
(GC/MS). With this method it is possible to observe very large
numbers of components in a sample. The gas chromatography
retention data and the mass spectral data contain information
which can be used to identify the specific agents present in
mixtures. A number of methods of pattern recognition are used in
the interpretation of GC/MS data. In this report, these methods
are reviewed. Also, methods are being developed at the
University of Illinois at Chicago for interpretation of air
quality monitoring data. These techniques involve the use of
computational methods of pattern recognition for the
interpretation of mass spectral data. As part of data
interpretation, molecular modelling and computer graphics methods
are used to develop parameters which can be used to predict the
gas chromatographic retention data for analytes.
Pattern recognition, as applied to GC/MS data, is the process of
comparing the spectra of unknown (test) compounds with those of
known (training) compounds with the objective to identify the
test compounds. Visual inspection of spectra by a trained mass
spectrometrist is the most reliable method of pattern recognition
but it is also the most inefficient and time consuming. With the
large volumes of data generated by the air quality monitoring
program, there are advantage to applying methods of artificial
intelligence to the problem of mass spectral interpretation.
There are two general types of pattern recognition: 1) syntactic
and 2) computational. In the former case, grammatical rules are
applied to match test spectra with training data. In the latter
467
-------
case mathematical functions are derived from the training data
which describe the spectral differences between chemical classes
or the variation in the data of specific classes. These rules
are then used to identify test compounds. Syntactic methods of
pattern recognition are extensively used in mass spectral
interpretation and form the basis for searching algorithms (1).
In order to be effective, syntatic methods require that very
large data bases of reference spectra be available for searching
and matching. Most data bases resident on mass spectrometers
contain 30,000-60,000 spectra. Syntactic methods are most useful
with instruments that are general purpose machines.
Computational methods have only recently been used in mass
spectral interpretation (2,3). Such methods are generally
applicable to cases in which the number of chemical types and
substances of interest is small and limited. This could be the
case in which a spectrometer is dedicated to a very specific
task. Large data bases are not necessary here so it is possible
to limit the reference data to those of specific interest.
Computational methods have advantages in thi3 case. Data can be
transferred from the instrument to a small desk top computer
where the necessary calculations and interpretation can be done
thereby freeing the instrument for data acquisition.
Examples of computational methods of pattern recognition are
class discrimination or hyperplane methods such as linear
discriminant analysis (LDA), distance methods such as k-nearest
neighbor ( k N N ) , and class modelling methods such as SI MCA. In
this work SIMCA and k N N methods are applied.
A typical gas chromatogram of an air quality field sample is
given in Figure 1, This sample contains a large number of
components, some of which are potential health hazards.
Approximately 80 compounds are in this category and
interpretation of the mass spectral data associated with the
chromatogram involves determining the presence or absence of the
toxic agents. The list of potentially toxic air pollutants has
been published (3) and are given in Table T. These are low
molecular weight aromatic hydrocarbons and halocarbons. Due to
the structural similarity of the reference substances, this
classification problem is particularly suited for computational
pattern recognition.
The reference compounds were initially grouped into 3 classes by
chemical type: 1) nonhalogenated aromatics, 2 ) chlorocarbons, and
3) bromo- and bromochlorocarbons. These classses are referred to
as the training data. In addition two standards and
tetrahydrofuran and dioxane were included as uncatagorized
agents. The mass spectral data were obtained from the NIH/EPA
library resident on the mass spectrometer.
The initial application of STMCA to the mass spectral data for
the training sets was of only limited success. It has been
published that mass spectral ion intensity data is not
appropriate for computational pattern recognition (4,5) and that
the autocorrelation transform of the mass spectrum should be
used. This tranform converts the ion intensities to frequency of
loss of fragments as shown in Figure 2 which compares the mass
spectrum of 1,2,3-trichloropropane. The high values of the
transform at 35, 36, 37 and 38 indicate a high frequency of loss
468
-------
of 35ci , 37ci and the corresponding hydrochlorides. The
coefficient at 2 indicates the occurrence of peaks 2 mass units
apart. The transform is typical of a chlorocarbon.
After transformation of the mass spectral data and applying SIMCA
to the training sets, class models were derived for the three
classes. These class models correctly classified 931 of the
training set data. In order to be correctly classified, it was
necessary that a reference compound be predicted to be a member
of its class and a nonmember of the two other classes. With this
significant classification outcome, it was decided to test the
approach on calibration data used in the monitoring process.
SIMCA pattern recognition, being a class modelling method, can
only identify compounds according to chemical class. In order to
assign a structure to a compound it is necessary to use another
method. Once a class assignment is obtained for an unknown the
kNN method was used to determine the 3-nearest neighbors to the
unknown in the appropriate training set. The kNN calculation was
carried out on the autocorrelation spectra. This provided ranked
possibilities for a structure assignment. To confirm a structure
assignment, the normalized correlation coefficient was calculated
for the unknown with its 3-nearest neighbors. This calculation
was done on the mass spectral data, i.e. in mass intensity space.
The normalized correlation coefficient is the cosine of the angle
between the unknown and the reference vector. As the two vectors
become identical the cosine of the angle between the two
approaches 1. Therefore, correlation coefficients > 0.9 indicate
that two spectra are very similar.
It is possible to observe compounds with very similar
autocorrelation spectra but very different mass spectra. This
would lead to an inconclusive assignment of structure in the
first step of the classification procedure. Therefore, a
feedback correction loop was necessary. If an inconclusive
classification result is obtained from the correlation
coefficient, the 3-nearest neighbors in the next closest class
were calculated and the procedure continued. In most cases this
will lead to the correct classification.
TABLE T
Compounds on the Air Quality Monitoring List
Compound Class* Name
1.
0
1-FLUOROTOLUENE (STANDARD)
2 .
n
1- FLUORO-2-IODO BENZENE (STANDARD)
3 .
1
1 ,M-DIMETHYLBENZENE
4 .
1
1 , 3 , 5-TRIMETHYLBENZENE
5 .
1
(1-HETHYLETHYL) BENZENE
6.
i
BUTYL BENZENE
7 .
1
1-METHYL-M-(1-HETHYLETHYL ) BENZENE
8.
2
1,2-DICHL0R0BENZENE
9 .
2
1,H-DICHLO ROBENZ ENE
10.
2
1-CHLORO-2-METHYL BENZENE
1 1 .
2
l-CHLORO-'l- METHYL BENZENE
1 2 .
2
1-ETHYENYL-H-CHL0R0 BENZENE
1 3 .
2
1,1-DICHL0R0ETHANE
1 M .
2
1 , 1 , 1 ,2-TETRACHLORETHANE
469
-------
15 .
2
1,2, 3-TRICHRL0RPR0PANE
16.
2
3-CHL0R0-1-PR0PENE
17.
2
2-CHL0R0BUTANE
1 8 .
2
1,3-DICHLOROBUTANE
19.
2
1 , 4-DICHLOROBUTANE
20 .
2
1 , 4-DICHLORO-2-BUTENE (CIS)
2 1 .
2
3.4-DICHLORO-1-BUTENE
22 .
0
1 ,4-DIOXANE
m
CM
2
1-CHL0R0-2,3-EP0XYPR0PANE
21) .
2
2-CHL0R0ETH0XYETHENE
25 .
1
1-PHENYLETHANONE (ACE TOPHENONE)
26 .
1
BENZONITRILE
27 .
1
BENZENE
28 .
1
METHYLBENZENE (TOLUENE)
29 .
1
1,2-DIMETHYLBENZENE
30.
1
1,3-DIMETHYLBENZENE
31 .
1
ETHYLBENZENE
32.
1
ETHENYLBENZENE (STYRENE)
33.
2
CHLOROBENZENE
3^ .
3
BRGMOBENZENE
35.
2
1 , 3-DICHLOROBENZENE
36.
2
1-CHLCRO-3-METHYL BENZENE
37 .
2
7RICHL0R0METHANE (CHLOROFORM)
38.
2
TETRACHLOROMETHANE (CARBON TETRA-
CHLORIDE
39 .
3
BROMOCHLOROMETHANE
40.
3
BROMOTRICHLOROMETHANE
41 .
3
DIBROMOMETUANE
42 .
3
7RIBR0M0METHANE
43 .
2
1,2-DICHLOROETHANE
4 4 .
2
1,1, 1-TRICHLORETHANE
45.
2
1,1,2-TRICHLOROETHANE
46.
2
1,1,2,2-TETRACHLOROETHANE
47 .
2
PENTACHLOROETHANE
48 .
2
1 , 1-DJCHLOROETHANE
49 .
2
TR ICHLOROETHANE
50 .
2
TETRACHLOROETHANE
51 .
3
BRCMOETHANE
52.
3
1 ,2-DIBROMOETHANE
53 •
2
1-CHLOROPROPANE
54 .
2
2-CKLOROPROPANE
55 .
2
1 , 2-DICHLOROPROPANE
56.
2
1 ,3-D ICHLOROPROPANE
57 .
3
1-BROMO-3-CHLOROPROPANE
58.
3
1,2-DIBROMOPROPANE
59 .
2
2,3-DICHLOROBUTANE
60 .
0
TETRAHYDROFURAN
61 .
1
BENZALDEHYDE
62 .
3
1-BROM0-2-CHLOROETHANE
63 .
3
2,2-DIBROMOPROPANE
64 .
3
2-BROMO-1-PROPENE
65.
3
2-BROMPROPANE
66.
3
3-BROMO-1-PROPENE
67.
3
1 -BROMOPROPANE
68.
2
1-CHLOROBUTANE
69 .
3
1-BROM0-2-CHLOROETHANE
70.
3
BRCMODICHLOROMETHANE
7 1 .
3
1-BROMOBUTANE
72.
2
2,2-DICHLOROBUTANE
73.
i
DTBROMOCHI.OROMETHANE
470
-------
7 4 .
75.
76 .
77 .
78 .
79 .
80 .
2
3
2
2
3
2
3
1,1,2-TRICHLOROPROPANE
1,3-DIBROMOPROPANE
1 , 1 , 1 , 2-TETRACIILORPROPANE
1,2,2,3-TETRACHLOROPROPANE
1.3-DIBROMOBUTANE
1,1,2,3-TETRACHLOROPROPANE
1.4-DIBROMOBUTAHE
Class 0 = standard; class 1 = nonha 1ogenated aromatic;
class 2 = alkyl- or aryl chloride; class 3 =
bromo- or bromochloro carbon
TABLE II
Summary of classification results
Sample
Correct/Total
8 5 110 2 5
28/35
85 II052
25/26
85 II072
14/18
Total
6 7 /7 9 ( 35 J)
A hierarchical classification scheme results which is shown in
Figure 3. To test the approach, the scheme was applied to data
used in the calibration of the air monitoring mass spectrometer.
Since these data were obtained on a different instrument from the
library data, this is a more difficult test.
A summary of the results is given in Table II. At this point the
results are very good. It was not possible to achieve 1001
correct classification results and to expect to do so would be
unreasonable. The difficulties with the approach appear to be
the result of assumptions made about the data. One difficulty
arises from instrument variability. The reference data were
obtained from the NIH/EPA library while the calibration data were
obtained on the EPA monitoring instrument. It is very difficult
to precisely reproduce the spectrum of a compound on a different
instrument. Also, it is assumed that the unknown compounds are
resolved and that the mass spectra are of the pure substance. In
a number of cases, mass spectra of the unknowns contain ions from
coeluting or otherwise contaminating compounds. An example is
shown in Figure H in which the mass spectrum of 1,2-dibromoethane
is compared with that of the same compound as observed in the
calibration data. The calibration sample bears little
resemblence to that of the reference and an identification in
this case would be impossible. Even in view of these limitations
it is felt that the approach can be used advantageously as an aid
to mass spectral interpretation and efforts are underway to apply
the technique to field data.
471
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REFERENCES
1. F. W. McLafferty and D. B. Stauffer, "Retrieval and
interpretative computer programs for mass spectrometry,"
J.Chem. Info. Comp. Sci., 25: 245-252 (1985).
2. P. C. Jura and T. L. Isenhour, Chemical applications of
pattern recognition. John Wiley and Sons, New York, 1971.
3. D. R. Scott, "Determination of chemical classes from mass
spectral of toxic organic compounds by SIMCA pattern
recognition and information theory," Anal. Chem. , 881 -890,
( 1 986) .
1. D. L. Duewer, B. R. Kowalski and J. L. Fasching, "Improving
the reliability of factor analysis of chemical data by
utilzing the measured analytical uncertainty," Anal. Chem. ,
48 : 2002-20 10 ( 1 976) .
5. S. Wold and 0. H. J. Christie, "Extraction of mass spectral
information by a combination of autocorrelation and
principal components models," Anal. Ch1m. Acta, 165: 51-59
(1984) .
472
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28?
100.0
*Tf
RIL
66!
78
1000
1ZOO
GOO
BOO
200
400
2:50 9: 40 8". 30 11:20 14:10 17: 00
Figure 1. Reconstructed ion chromatogram of an air quality field
sample .
1-2-3-TRICHLOHOPROPANE
IT i "I Mill H l I 111 I I i i | 111 I i I 11 I |i 111] 11 111 i 11 I |
50 100 150 200 250
n/e
1-2-3-TRICHLOROPROPAHE
tHt
{—III" I 1 I 'l I' 'Mil IT) " 'It i {ill"1 - -j
10 20 30 40 50 60 70 80 90 100
Mass of fragment lost
Figure 2. Mass arid autocorrelation spectra of 1,2,3-
trichloropropane .
473
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ANALYSIS OF MASS SPECTRA
Training Sat
>
r
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r
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Traoafonn
p. .
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tu Cliia Uodoia
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r
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r
Convert to
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1
r
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TraailoriA
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I
Calculata K-MN
Clan
I
K naaraat compound*
1.2.3, .
Calculate CorrolaUoo
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Identify
Compound 2 or 7
Figure 3 ,
Flowchart of hierarchial classification scheme
474
-------
i:
58
l-2-DIBR
-------
APPLICATIONS OF INFORMATION THEORY AND PATTERN
RECOGNITION TO GAS CHROMATOGRAPHY-MASS
SPECTROMETRY ANALYSIS OF TOXIC ORGANIC
COMPOUNDS IN AMBIENT AIR
Donald R. Scott
Environnental Monitoring Systems Laboratory
II. S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
The number of information channels contained in the gas chromatographic,
mass spectrometric, and combined gas chromatography-mass spectrometric
analysis of 78 toxic organic compounds has been determined. The toxic
compounds are those routinely monitored in ambient air samples using Tenax
collection and gas chromatography-mass spectroinetric analysis. The Shannon
information content of the binary encoded and full intensity mass spectra,
of the gas chromatographic retention times, and of the combined gas
chromatographic-mass spectrometric spectra of the /H compounds has been
calculated. The maximum binary information contents of the 35 channel gas
chromatographic, 17 key channel mass spectral, and the 595 channel gas
chromatographic-mass spectral methods were 6.4, 15.4, and <21.8 hits,
respectively. The 17 masses with the highest binary information content
with regard to the 78 compounds were used with SIMCA pattern recognition to
determine four classes among the 78 compounds. These included aromatics
without chlorine substitution, chloroaromatics, bromoalkanes and alkenes,
and chloroalkanes and alkenes. Alkenes and alkanes with both chloro- and
bromo substitution were classified as bromo compounds. The principal
component models generally consisted of only one component, per class, with
five masses per class. However, the total alkene and alkane class had two
components with twelve masses. Classification accuracy was 96% for the
total aromatics and total alkanes and alkenes and 82% for the four
subclasses. The pattern recognition study was performed on a commercially
available microcomputer with a 64 k CPU. The information content of
gas chromatography, mass spectrometry, and gas chromatography-mass
spectrometry in general and with regard to this analytical problem
is discussed.
476
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APPLICATIONS OF INFORMATION THEORY AND PATTERN RECOGNITION TO GAS
CHROMATOGRAPHY-MASS SPECTROMETRY ANALYSIS OF TOXIC ORGANIC COMPOUND IN
AMBIENT AIR
INTRODUCTION
At the present time the most commonly used analytical procedure for
the determination of volatile organic compounds in ambient air is gas
chromatography-mass spectrometry. This is due to its high selectivity,
sensitivity, and applicability to a very large number of compounds. The
present study is concerned with the development of methods for efficient
extraction of information regarding chemical class identification from data
obtained during routine gas chromatographic-mass spectrometrlc analyses.
The pattern recognition techniques are empirical in nature and therefore
do not require any expert knowledge regarding the mass spectra of the
classes. The development of such methods would allow retrospective
analysis of routine data files for determining the presence or absence of
defined chemical classes of interest. The determination of the classes
could be done on a small microcomputer without additional analytical costs
and does not have to be confined to the compounds originally sought. Such
information may be of interest 1n survey studies of health hazards and in
preliminary scans of mass spectral data files before detailed
Interpretation is accomplished.
A set of 78 toxic organic compounds was chosen from those ca. 100
compounds presently routinely sought in ambient air samples. The set of 78
toxic compounds investigated contained primarily aromatic compounds,
haloalkanes, and haloalkenes together with an additional four ethers and
epoxides. Approximately 80?, of tnese compounds contain chloro and/or
bromo groups. All alkanes and alkenes contained at least one halogen.
Shannon information theory and SIMCA pattern recognition were used. The
Shannon information contents of the gas chromatographic, mass spectro-
raetric, and the combined gas chromatography-mass spectrometric methods
for the identification of the set of 78 compounds also were determined.
THEORETICAL BACKGROUND
Shannon Information Theory
The Shannon information content of a message (1) is related to the
reduction in uncertainty gained by the receiver of the message. The
information content will depend on the probability of occurrence of the
symbols used, correlation between the symbols, encoding and decoding
errors, and other uncertainties due to random errors. After chemical
analysis the uncertainty with regard to the presence of certain species in
the sample is reduced. Therefore the analysis produces a certain amount of
Shannon information concerning the sample. In low resolution mass
spectrometry the message is equated to the mass spectrum itself. The
symbols are the intensities at a given unit mass channel. Neglecting
errors, the information content per mass channel, I(j), is given by
m
I(j)= - I Pi(i) log p j (i)
i-1 "
where m is the number of discrete intensity values available for mass
channel j. The probabilities of occurrence of a mass intensity, pj (i), are
calculated over the entire set of reference spectra. The total information
477
-------
content of a given mass spectrum is the sum of the information contents of
the individual channels, if correlation between masses is neglected.
Since correlation between masses is well known in mass spectra, this in-
formation content should be regarded as an upper limit to the true
information content. This formula can also be used to calculate the
informational contents of gas chromatography channels (retention time data)
and of gas chromatography-mass spectral channels if the distribution of the
data representations over the respective channels and compounds are known.
In the case of binary data the Shannon Information content can be
calculated from a simplified formula. For example with binary encoded
spectra there are only two possibilities for the intensity of a mass peak,
1 or 0, corresponding to the presence or absence of the peak above a
threshold level. Therefore the information content for mass channel j can
be calculated from
I(j) = -Pj log pj- (l-pj)log (1-pj).
Here pj is the probability of a peak occurring at the mass channel j
calculated over the set of mass spectra of the 78 compounds. In the case of
the gas chromatography data the binary data corresponds to the presence or
absence of a peak in a given channel. In the combined gas chromatography-
mass spectral channels the binary data corresponds to the presence or
absence of a compound-mass spectral peak in that channel. If the logarithm
used is to the base two, then the information content is expressed in bits.
The maximum information content per channel for the binary case is one bit
and occurs at a probability of 0.5. Nonoccupied channels and those with
probabilities of 1.0 contribute no information content.
SIMCA Pattern Recognition
The SIMCA (Soft Independent Modeling of Class Analogy) pattern
recognition techniques were developed by Wold and coworkers and have been
described in the literature (2,3). The statistical pattern recognition
techniques are based on disjoint principal component models for
classification of objects. The SIMCA class models are bilinear projec-
tion models obtained by decomposing the class data matrix (X) into a
score matrix (T) (n x F), a loading matrix (P) (F x p) and a residual
matrix (E) {?.).
(X) = 1 * x + (T) (P) + (E) (1)
The row vector x is composed of all the averages of the variables in the
class data matrix. The n x F score matrix (T) describes the projection of
the n object points down on the F dimensional hyperplane defined by the F x
p loading matrix (P). The residual matrix (F) contains that part of the
data matrix due to measurement and modeling errors. If the residuals in
(F) are small compared with the variation in (X), then the model is a good
representation of (X). When F is two or three, the columns in the
score matrix (T) can be plotted against each other to get two dimensional
pictures of the objects in hyperspace (measurement space). The model-
ing power, i.e. the reduction of variance, for a given variable can be
used as a measure of its relevance to the class model. Judicious
use of the variable loadings and modeling powers obtained in preliminary
analyses of the data allows one to polish t.he model and remove variables
which arc not significant to the class.
The number of principal components determined and retained for a
particular class model is an important consideration. Within the SIMCA
47B
-------
procedures the process of cross validation (4) is used to determine the
number of statistically significant principal components for a given class.
In this process subsets of the training set of objects are used to fit a
class model with one principal component. The objects not used in
determining this class model are then fitted to the model, and the sum of
squared residuals for the withheld objects is calculated. This is repeated
until all of the objects in the training set have been withheld from the
model fitting. The overall sum of squared residuals is then calculated for
all the withheld objects for this particular model. The entire process is
repeated with a class model containing an additional principal component.
Addition of principal components to the model is continued until comparison
of the sums of squared residuals for the previous and present model show no
improvement. Generally, if the number of principal components for a given
class model is much smaller than the number of either objects or variables
for the class; then the model will be statistically stable.
Once the class models have been determined, objects are classified by
fitting their data to the various class models. A standard deviation for
each model is calculated from the residuals. This represents a class
tolerance level around the principal component model in measurement space.
The standard deviations for the objects are calculated from the residuals,
and the objects are classified based upon their distances from the class
models.
EXPERIMENTAL
Data Set
The low resolution mass spectra of the 78 compounds were obtained from
the EPA-NI Hi Mass Spectral Library on an I NCOS data system. A typical spec-
trum contained approximately 16 peaks. The range of mass/charge ratios
was fron 35 to 25fi with 151 different peaks occurring in the total set.
For the full intensity data the intensities were scaled to give a maximum
of one for the base peak. The data were also binary encoded by assigning
an intensity of one to any peak over the threshold level, which was U of
the base peak intensity. A list of individual conpounds in the set is
given in Table I. The retention times were determined on a 50 meter, open
tubular, SL 30 wall coated column relative to perfluorotoluene and 1-fluoro
-2-iodobenzene internal standards.
Hardware and Software
In this study an Osborne 1 microcomputer (Z80A) with a CP/M operating
system and *54 k memory was used. This amount of memory is sufficient to
handle a data matrix of size b() objects by 5!) variables. The SIMCA 3B
software package was ohtained from Principal nata Components, Columbia, Mo.
Data Analysis
The information content of the 151 different nonzero intensity mass
channels was calculated from the distribution of the binary encoded mass
spectra of the set of 78 compounds us^ng the formulas given above. The
full intensity mass spectra of the data set were encoded into ten discrete
levels above the threshold level, and the Information content for the mass
channels also was calculated using this distribution. No correction was
made to account for encoding errors or for correlation between mass channels.
In the case of the gas chromatography analysis, the width of a channel was
determined from the reproducibility (three standard deviations = ca. 0.35
min.) of the relative retention times. The total number of channels was
479
-------
calculated from the channel width and the time spread from the first and
last compounds eluted. The binary information content of the retention
times was calculated from their distribution over these channels. The
number of combined gas chromatographic-mass spectral channels was
limited by using only the 17 most informative mass channels and combining
these with the gas chromatographic channels as determined previously. The
binary information content of the distribution of the compound occurrence-
mass spectral peaks over these channels was then calculated. Since no
corrections were made for correlation or for residual errors, the
calculated information contents should represent upper limits to the true
values.
The class modeling and object classification were performed with the
SIMCA 3H software. The data were preprocessed by binary encoding of only
those 17 mass channels selected after calculation of the Shannon
information content. All data were class scaled. The training sets for
each of the classes were selected after investigating the inherent
structure of the data set. All objects in a given class were used for the
training sets, except for bromohenzene which was only used in the total
aromatic training set. The numbers of compounds used in the training sets
for the classes were 23 for total aroinatics; bl for total alkanas and
alkenes; 8 for chl oroaromati cs ; 14 for nonhaloaromatics; ?.\ for bromo-
alkanes and -alkenes; and 30 for chloroalkanes and -alkenes. Cross
validation was used to determine the mini mum number of statistically
significant components for each class model. Variables with modeling
powers less than 0.18 for the principal component models were deleted in
the initial stages of the refinement of the class models.
RESULTS AND DISCUSSION
Pattern Recognition of Classes from Mass Spectra
The binary encoded mass spectra of the 78 compounds yielded
Information contents per channel of 0.10 to 1.00 bit with the higher
information at mass channels below 107. Of the channels from 107 and
below, 70% had 0.5 bit or greater information. Of the channels greater
than 107, only 7.4% had 0.5 hit or greater information content. The
information content for the full intensity spectra of the 78 compounds
ranged from 0.10 to 2.29 bit with no channels above 107 exceeding 1.02 bit.
In general the information contents of the binary and full Intensity mass
spectra show a linear correlation up to a binary information content of ca.
0.9 bit. Even in the case of the higher information channels there is good
qualitative agreement as shown in Table 11 where the 17 mass channels with
the highest binary spectral information content are compared with those
from the full intensity spectra.
Table II also contains the information content of the same masses
evaluated for a set of 9600 binary mass spectra (5). Comparison of the
information content of these 17 mass channels for the binary spectra of
the 78 compounds with those found for the set of 9600 compounds also
shows a good correlation. The 17 highest information mass channels for
the set of 78 compounds yielded 0.80 to 1.00 bit with a median of 0.92
bit, while the same nass channels with the set of 9600 compounds gave 0.62
to 1.00 bit with a median of 0.91 bit. Those channels have the highest
information content, i.e. greater than 0.80 bit, for the binary encoded
spectra with the exception of channel 39, which is not listed. This
latter mass channel was not used since it is one of the most frequently
occurring peaks in mass spectrometry (6). Thus it is clear that this set
480
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of 17 most "informative" mass channels contains very much information not
only with regard to the set of 78 compounds but also with regard to the
much larger set of 9600 compounds.
It is well known that the information in a complete mass spectrum is
highly redundant and that compressed binary encoded spectra retain a large
portion of the information present in the complete spectrum (5,7,8). to
solve the present pattern recognition problem on a microcomputer, the
number of mass channels considered was reduced from 151 to the 17 channels
listed in Table II. This set of binary encoded, 17 mass channel spectra,
which will be designated hereafter as the compressed spectra, was used
as the trial set of variables in the pattern recognition classification of
the 78 compounds. The use of the compressed set of hi nary spectra caused
nine pairs and one trio of compounds to have identical mass spectral
representations.
The inherent structure of the data should determine the nature of the
classes and not some preconceived scheme based on chemical training or
intuition. For a preliminary overview of the data a two dimensional
principal component plot of the 17 mass, full intensity data was
constructed. Only 49 of the 78 compounds were considered in this plot due
to limitations of the SIMCA program used. However, the compounds selected
included representatives of all apparent chemical classes in the set.
There was no class separation of any type visually apparent in the
resulting plot. This result was not unexpected since it has been pointed
out in previous studies (9,10) that untransfonned mass spectral data
should not be used for pattern recognition studies. An examination of the
binary encoded, 17 mass data for the same 49 compounds in a two dimensional
principal component plot gave the results shown in Figure 1. It Is apparent
from this plot that there is some basic separation of the compounds into at
least three classes and probably four. In the lower right corner is a
bromo substituted group of alkanes/alkenes including bromochloro substituted
alkanes/alkenes. In the lower left corner is a group of nonhalogenated
aromatic compounds. At the top center is a group of chloroalkanes/alkenes.
Lying between and partially overlapping the latter two groups is a group of
chloroaromatics.
It is clear that the compressed set of data contains enough
information for useful classification of the 78 compounds. We have chosen
to use two general classes: aromatics with 23 compounds and alkanes/alkenes
with 51 compounds. For further detailed classification four subclasses
were used: nonhalogenated aromatics with 14 compounds; chloroaromatics
with 8 compounds; chloroalkanes/alkenes with 30 compounds; and bromo-
alkanes/alkenes with 21 compounds. The seven alkanes/alkenes with both
chloro and bromo substituents were found during initial calculations to fit
with the bromo alkaenes. The additional four compounds, the three ethers and
one epoxide, were withheld from the training sets and used as test objects.
With the use of the variable modeling power and the compressed set of 17
mass spectra, it was found that only five masses were required for each
refined class model except for the total al kanes/alkenes class. In the
total al kanes/al kenes case 12 masses were required. The use of cross
validation resulted in the refined models having only one principal com-
ponent per model except for the total alkanes/alkenes model which had two.
The model parameters including loadings are given in Reference 11. The
unexplained variance ranged from a low of 19% for the chloroaromatic model
to a high of 47% for the chloroalkane/alkene model. The residual standard
deviations, which are a measure of the spatial extent of the models, ranged
from 0.49 for the chloroaromatic model to 0.77 for the chloroalkane/alkene
model.
481
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After the class models were determined, the entire set of compressed
spectra of the 78 compounds was run through all of the six models to
determine classification accuracy. Compounds were considered as members
of the class to which they were closest. In the case of the two major
classes, aromatics and alkanes/alkenes; the training set accuracy was 91
and 98%, respectively, with an overall accuracy of 96%. Only 1 and 3% of
the 74 compounds were incorrectly classified as members of the two classes.
All of the four test set compounds, which do not properly belong to any
of the classes, were classified as al kanes/alkenes, which is correct
when interpreted as "not aromatic".
In the case of the four subclasses: nonhaloaromatics, chloroaromatics,
hroinoalkanes/al kenes, and chloroalkanes/alkenes; the training set accuracy
was 79, 87, 86, and 80%, respectively. The overall accuracy was 82%. The
number of compounds misidentified as members of the four classes were 3,
4, 3, and 8%, respectively. In this case bromohenzene was added to the
four test set compounds. The two chlorosuhstituted al kane/alkene type
compounds were correctly classified. lironiobenzene was classified as a
chloroaromatic which is the most suitable of the four possible classes.
The two cyclic alkane ethers were classified as bronioalkane/alkenes,
which if regarded as "alkane/alkene, but not chloroalkane/alkene", is
correct within the available models.
It was also possible to construct a class model for chlorinated
alkane/alkenes based upon the number of chloro groups present in a
compound. A single principal component model using the five masses - 63,
65, 75, 77, 91- was found to be statistically valid for the class of rnono-
and dichloroalkane/alkenes, which did not include compounds substituted
with both chloro and bromo groups. This model gave an unexplained variance
of 42% for the 16 training set compounds with a residual standard deviation
of 0.73. The loadings of the principal component were ca. 0.4-0.5 with
mass 63 and 65 having negative loadings. The training set accuracy
was only 62%, but the overall accuracy for 78 compounds was 91%. Only
two compounds, both monochloromonobromoalkanes/al kenes, were misidentified
as members of this class.
Information Content of Analytical Methods
The relative retention times of the 78 compounds on the SE-30 column
and their reproducibiIity resulted in 45 discrete gas chromatography chan-
nels for this problem. No compounds were eluted in ten of these channels,
so there were only 35 nonzero channels to consider. Since there were less
than one-half as many channels as compounds, complete separation (one com-
pound per channel) was not achieved with this column. Of the 35 channels
8.5% contained five compound peaks in each; 5.7% had four compound peaks;
17% had three compound peaks; 37% had two compound peaks; and 31% had only
one compound peak. The zero-filled channels contribute no information con-
tent. The maximum information content of the 35 gas chromatography channels
was 6.41 bits, which was obtained by summing the individual channel infor-
mation contents.
In the case of the mass spectral channels only the 17 channels used in
the pattern recognition study were considered in order to keep the
calculations at a manageable size. The largest correlation coefficient
among these mass channels was 0.75 between masses 81 and 93, and only four
pairs of masses had correlation coefficients greater than 0.5. The maximum
information content of these 17 mass spectral channels was 15.4 bits.
482
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One would expect the number of channels available for the combined gas
chromatography-mass spectral method to be the product of the two individual
methods, i.e. 45 % 17 = 765. This is illustrated in Figure 2, where N =45
and M =17. The shaded areas are zero-filled channels. However, due to the
ten zero-filled gas chromatography channels there is a general loss of 170
combined channels, leaving 595 channels. The maximum information con-
tent of the combined method can not exceed the sum of the information
contents of the individual methods and can not be less than the smaller of
the two methods. Therefore the maximum information content of the combined
methods is less than 21.8 bits and, with much less certainty, greater than
6.4 bits.
The number of channels, the information contents for the three methods,
and the maximum and actual number of compounds distinguishable are summa-
rized in Table III. The maximum number of compounds distinguishable was
calculated by using the maximum bits of information as a power of two to
obtain the maximum number of different spectral representations. The actual
number of compounds distinguished is the average number which is found
to be different in a given method. Even though the theoretical maxi-
mum number of compounds which can be distinguished is 78 for gas chroma-
tography to ca. four million for gas chromatography; the actual number
is much less and only amounts to 76 for the combined gas chroma-
tography-mass spectrometry method. Correlation and uncertainties remaining
after analysis account for much of the difference, but some of the
difference is due to excess capacity which is not relevant to this parti-
cular analysis problem.
CONCLUSIONS
Shannon information theory has been used in this study for selection of
relevant variables in SIMCA pattern recognition studies of mass spectral
data and as a quantitative measure of maximum information content of
analytical methods for a specific problem. In the pattern recognition
study of the 78 toxic compounds 151 different mass channels were compressed
into 16 which were actually used in the different class models. The major
classes found were nonhaloaromatic, chloroaromatic, bromoalkane/alkene,
and chloroalkane/alkene compounds. A subclass of alkanes/alkenes
containing one or two chlorosubstituents was also found. In all models
except the all alkane/alkene model only one principal component containing
five masses was found to be statistically significant. The accuracy was
96% for alkane/alkene vs. aromatic classification and 82% for clas-
sification into the four groups.
SIMCA pattern recognition is an empirical classification technique
and does not require particular spectroscopic expertise for its applica-
tion. Its successful application to the present problem on a microcomputer
with limited memory should demonstrate to chemists the availability and
power of the technique and the large amount of useful information in the
low resolution mass spectra.
The numbers of channels and information content for a given method
should not be confused with those relevant to the solution of a particular
problem. As has been shown here the amount of maximum information for a
given analytical method may be very large, but all of the capacity of the
method may not be applicable to a specific analytical problem.
483
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REFERENCES
1. P. Cle1j, A. Dijkstra, Z. Anal. Chem., 298: 97 ( 1979).
2. S. Wold, C. Albano, W. J. Dunn III, U. Edlund, K. Esbensen, P. Geladi,
S. Hellberg, E. Johansson, W. Undberg, W., M. Sjostrom, 1n
B. R Kowalski, Ed., "Chemometrlcs, Mathematics and Statistics
in Chemistry", D. Reidel Publishing Co., Boston, 1984, pp. 17-96.
3. S. Wold, Pattern Recognit., 8_: 127 ( 1976).
4. S. Wold, Technometrics. 20: 127 (1978).
5. G. van Marlen, A. Dijkstra, Anal. Chem., 48: 595 (1976).
fi. G. M. Pesyna, F. W. McLafferty, R. Venkataraghavan, H. E. Dayringer,
Anal. Chem., 47: 1161 (1975).
7. S. L. Grotch, Anal . Chem., 42: 1214 ( 1970).
8. J. B. Justice, T. L, Isenhour, Anal. Chem., 46: 223 (1974).
9. J. R. McGill, B. R. Kowalski, J. Chem. Inf. Coroput. Sci., 18: 52
(1978).
10. S. Wold, H. J. Christie, Anal. Chim. Acta, 165: 51 (1984).
11. 0. R. Scott, Anal . Chem., 58: 881 (1986).
484
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TABLE I. COMPOUNDS INCLUDED IN THIS STUDY
1. p-xylene
2. 1,3,5-trlmethylbenzene
3. isopropylbenzene
4. n-butylbenzene
5. 1-methyl-4-fsopropylbenzene
6. o-d1chlorobenzene
7. p-dichlorobenzene
8. l-chloro-2-methylbenzene
9. 1-chloro-4-methylbenzene
10. p-chlorostyrene
11. 1,1-dichloroethane
12. 1,1,1,2-tetrachloroethane
13. 1,2,3-trichloropropane
14. 3-chloropropene
15. 2-chlorobutane
16. 1,3-dlchlorobutane
17. l,4-d1chlorobutane
18. l,4-dichloro-2-butene (c1s)
19. 3,4-d1chlorobutene
20. 1,4-dioxane
21. 1-chloro-2,3-epoxypropane
22. 2-chloroethoxyethene
23. acetophenone
24. benzonitrile
25. benzene
26. toluene
27. o-xylene
28. m-xylene
29. ethylbenzene
30. styrene
31. chlorobenzene
32. bromobenzene
33. m-d1chlorohenzene
34. 1-chloro-3-methylbenzene
35. chloroform
36. carbon tetrachloride
37. bromochloromethane
38. bromotrlchloromethane
39. dibromomethane
40. bromoform
41. 1,2-dichloroethane
42. 1,1,1-trichloroethane
43. 1,1,2-trlchloroethane
44. 1,1,2,2-tetrachloroethane
45. pentachloroethane
46. 1,1-d1ch1oroethene
47. trichloroethene
48. tetrachloroethene
49. bromoethane
50. 1,2-dibromoethane
51. 1-chloropropane
52. 2-chloropropane
53. 1,2-dichloropropane
54. 1,3-dichloropropane
55. l-bromo-3-chloropropane
56. 1,2-dfbromopropane
57. 2,3-d1chlorobutane
58. tetrahydrofuran
59. benzaldehyde
60. 1-bromo-l-chloroethane
61. 2, 2-dibroinopropane
62. 2-bromopropene
63. 2-bromopropane
64. 3-bromopropene
65. l-bromopropane
66. 1-chlorobutane
67. l-broiro-2-chloroethane
68. bromodichloromethane
69. 1-bromobutane
70. 2,2-dichlorobutane
71. dibromochloromethane
72. 1,1,2-trichloropropane
73. I,3-dibromopropane
74. 1,1,1,2-tetrachloropropane
75. 1,2,2,3-tetrachloropropane
76. 1,3-d1bromobutane
77. 1,1,2,3-tetrachloropropane
7B. 1,4-dibroniobutane
485
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TABLE II. 17 KEY MASSES WITH HIGHEST INFORMATION CONTENT
FOR 78 TOXIC COMPOUNDS
MASS
INFORMATION CONTENT
MASS
INFORMATION CONTENT
BINARY3
FULL"
9600c
BINARY
FULL
9600
(BITS)
(BITS)
41
0.92
1.92
0.90
77
0.94
1.75
1.00
49
0.98
1.68
0.62
78
0.84
1.31
0.93
50
0.84
1.18
0.98
79
0.96
1.27
0.97
51
0.99
1.78
1.00
81
0.80
1.02
0.91
61
0.82
1.36
0.75
91
0.92
1.47
0.96
62
0.95
1.61
0.81
93
0.87
1.22
0.83
63
1.00
1.95
0.97
95
0.90
1.39
0.83
65
0.92
1.35
0.98
107
0.82
1.08
0.74
75
0.89
1.42
0.89
a. Binary spectra of 78 compounds.
b. Full intensity spectra of 78 compounds.
c. Binary spectra of 9600 compounds, Reference 5.
TABLE III. GC, MS, GC-MS INFORMATION CONTENT FOR 78 COMPOUNDS
USING 17 KEY MASSES
METHOD
CHANNEI
TOTAL
.S
NONZERO
MAXIMUM I
(BIT)
CMPOS DISTINGUISHABLE
MAXIMUMS ACTUAL13
GC
45
35
6.4
78
27
MS
17
17
15.4
43000
60
GC-MS
765
595
< 21.8
< 3700000
76
a. The
number obtained by raising
two to the
power of maximum
I.
h. The number of different compounds actually distinguished by the method.
486
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¦ ¦
O AHOW'TIi:
« ahoM*> 11c c:i
¦ A. r A I- N( CI
~ AiKAt Nt B>
ii AiftAtttf H. Cl
£ G1M1.M
A
00
00
PRINC'PAl COMPOMTNT I
~ u
u
Figure 1. Principal component plot of 17 key mass spectra.
INFORMATION CHANNELS
I-OR GC. MS AND GC-MS
/L==j! ¦"
ATlVI- milliNTiON I'Mt
L.(. C.HANNI iS
1 j 4
MS IjlANNi I i
«r. MS C.I10NNI I s
Figure 2. Combination of t.iC and MS channels.
487
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USING THREE DIMENSIONAL GRAPHICS
TO VISUALIZE MULTIVARIATE SCIENTIFIC DATA
S. L. Grotch
Lawrence Livermore National Laboratory
Livermore, California
The two dimensional plot is unquestionably the most commonplace graphics tool of
the scientist. Yet in dealing with problems often involving high dimensionality, more
sophisticated representations (such as 3D) are only infrequently used.
In the work reported here, several real-world examples are used to illustrate the
wide variety and the resultant interpretive potential possible through the use of three
dimensional graphics. These examples are a study of climate data and of air pollution
monitoring. Among the variety of 3D plots presented are discrete point plots; mesh-like
surface plots showing either theoretical or empirical model behavior; and combinations
of points and surfaces. Some of the many techniques available to enhance the utility of
such graphics are shown.
48S
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USING THREE DIMENSIONAL GRAPHICS
TO VISUALIZE MULTIVARIATE SCIENTIFIC DATA
Climate Data Example
A better understanding of climate would yield many obvious practical benefits.1
In a continuing study at the Lawrence Livermorc National Laboratory of the possible
climatic effects of greenhouse gases 2, particularly carbon dioxide, a large number of
historical temperature records have been examined. To determine and isolate possible
statistically significant changes in these climate records, "noise" inherent in these data
must be characterized. Here, this noise will be estimated as the standard deviation of
surface temperature (ct(T)), measured at a specific point over some extended time period.
Because climatic changes of variotis types may be occurring, this estimate may, include
multiple effects: eg. volcanic eruptions and even changes due to slow increases due to
greenhouse gases. In more detailed studies, we may have to be. more selective in our
definition of "noise."
In the example given here we will examine the spatial distribution of the estimated
c (T) of monthly temperatures measured over the past century over the North American
(NA) mainland. The data record used is one of the most complete gridded sets available.3
We wish to examine the variation of the estimated standard deviation of temperature as
a function of: (l) latitude, (2) longitude, and (3) month of the year.
In the following discussion a variety of 3D plotting techniques will be used to illustrate
how these data can be graphically presented to better facilitate understanding. From
these examples, it is hoped that the reader will gain a better appreciation for both the
promise and the difficulties which arise in graphically showing abstract data using three
dimensions.
Before showing these results using three dimensional plots, let us examine a simple,
more conventional, two dimensional representation of the January distribution of cr(T)
(Figure l). Here, the numerical values for <7(T), in °C, are shown next to their spatial
positions. These a estimates are made using 100 successive January mean temperatures
over the period: 1881-1980, placed on a regular 5ux 10° grid.3 Another common 2D
representation is the contour plot, routinely produced by many software packages.
There are several very practical advantages to such plots. They are easily gener-
ated using widely available software, and one can certainly infer many of the important
characteristics of the data from them. Because of the emphasis here on 3D plots, one
Bhould definitely not infer that plots such as Figure 1 are outmoded or, of little value!
On the contrary, the contention here is that in conjunction with any and all such 2D
representations, the three dimensional plot can convey a richer, deeper, and generally
more profound understanding of the data.
Figure 2 showB these same data in a simple three dimensional plot with the vertical
axis indicating the nns value of January temperatures and the lower plane, the geograph-
ical location over NA. In this first 3D representation, The points are drawn using two
dimensional symbols. This representation is ambiguous since the relative positions of
the points are difficult to sense, and consequently the plot is not readily interpretable.
In the following scries of plots, a variety of visual enhancements are used to illustrate a
number of techniques that can substantially increase the utility of such plots.
Merely connecting the points in space with their location on the base plane results in
a significant improvement in our ability to interpret these data (Figure 3). The locations
of the points are now much clearer, and we can see immediately that the January c(T)
489
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increases markedly as we move away from the equator. Our understanding is further
enhanced if the data points are shown as shaded three dimensional cubes and their
locations on the base plane are further accented using tilted projections, as in Figure 4.
Probably the most significant improvement in our understanding of these data is
achieved by changing our viewpoint relative to the data, as is shown in the four sub-
plots of Figure 5. Here, we have "walked" around the scene and tilted it to show more
clearly various aspects of the data. The increase in January temperature variability with
latitude is particularly apparent, but now we can better sense another aspect of the
variation, the increase in c(T) as we move inland, away from the moderating effects of
the ocean, the continentality effect.
We have examined the variability of temperature for only the month of January.
How does it change for different months of the year? Specifically, how does it vary
between summer and winter over North America? Figure C shows the analagous plots
for July seen from the same viewpoints and drawn with identical scaling to those of
January (Figure 5). The striking difference between summer and winter is immediately
evident. Both the increase of a(T) with latitude and with continentality have moderated
considerably, and in July there is much less variability than in January.
In an attempt to quantify these spatial distributions for computational purposes,
quadratic surfaces (in terms of latitude and longitude) were separately fit to these data
lor each month. The surface for January is shown in Figure 7. Both the quadratic
surface (derived by linear least squares) and the actual data points are shown. Points
above the surface are shown as open cubes, those below are shaded. Four different views
of this surface (without the data points) are plotted in Figure 8. These points provide a
better sense of the bowed nature of the surface. Finally, Figure 9 contrasts the January
and July surfaces using superposition. The dramatic difference in cr(T) between the two
months is immediately evident. A capability for graphics software editing such as that
used in Figure 9 is of great value in effectively manipulating such graphics.
At this juncture, it is worthwhile to emphasize several practical considerations. The
necessity for real-time or near-real-time viewing of these plots should be apparent. The
software producing such plots should ideally provide the user with considerable flexibility
in the choice of options excercised, and these must be available in a "user-friendly"
framework. The choice of the "best" viewpoint and the "best" combination of features
to include is often both subjective and data dependent, and thus cannot generally be
made, a priori. The challenge of three dimensional plotting is judiciously choosing from
the wide range of enhancements available to facilitate our ability to derive informaion
from such plots.
Spatial distributions of chemical pollutants
A second example, drawn from our air quality studies illustrates another application
of three dimensional plotting. With virtually the same software used to generate the
previous plots, other types of spatial distributions can be represented. The numerical
results of computer simulation models can be directly used with such software to generate
3D plots showing the geographical distribution of a variety of variables: (l) terrain, (2)
concentrations of various chemical species, (3) winds or mass fluxes. By combining
a series of such "snapshots," at different times, all viewed from the same perspective
and drawn with the same scaling, the evolution of different variables can be graphically
followed in time.
In a numerical simulation of air pollution over the San Francisco Bay Area/ the con-
centrations of a variety of chemical species were calculated as » function of geographical
490
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position (x, y) and of time. In this example, hourly concentrations were available for
each of five species at 400 grid points over the San Francisco Day Area. From the model,
mass flux vectors at each grid point were also calculated as a function of time. The
challenge is to represent these variables graphically in a manner that is both accurate
and interpretablc by both the specialist and the non-scientist.
Using a Gaussian random number generator to calculate displacements from each of
the central grid points (in all three dimensions), a cloud of hundreds of discrete points can
be generated that is spatially centered in 3D about each grid point. If, for a given species,
the number of points comprising each cloud is made proportional to the concentration
of that species at that gridpoint, a plot can be developed in which the spatial density
of points is proportional t-• the calculated concentrations. By appropriately choosing
the spreading parameters o. .lie pollutant, cloud (it:, the standard deviations of the dis-
placements), u faithful rendition of the model predictions can be obtained. The use of
contrasting colors in highlighting important features, for example, the coastline and the
Ray, can be extremely valuable. The vertical exaggeration of terrain and of the cloud
positioning can be interactively modified by the user until a meaningful representation is
achieved. Coordinate axes and grids can be included if more quantitative locations are
required.
Note that, in this case, both the vertical positioning and the vertical scaling of the
pollution cloud are arbitrary. Here, the central vertical level chosen for each point cor-
responds to the terrain height at the grid point. This offset from the lower terrain was
necessary because the graphics software that was available did not have a hidden line
removal capability when drawing the cloud points. Thus, to avoid confusion, particularly
when overprinting with color, this vertical offset was used.
As with the earlier examples, there are a wide variety of modifications that can be
used to facilitate the interpretation of these graphics. Among these are: different view-
points, cloud dispersion characteristics, offsets, scaling, colors, numbers of points, and
connectors between surfaces. To facilitate the process of generation, the graphics soft-
ware should provide the user with many "knobs and switches" that can be interactively
manipulated to achieve the desired result. Since each application is likely to call for
different characteristics, even within the same project, such user controls are virtually
essential in providing the flexibility which is generally required. Equally vital is the
capability for real-time or near-real-time viewing of any graphics generated.
Figure 10 shows the model prediction of the early morning (8 AM) distribution of
ozone over the Bay Area. To aid in spatially locating "hot spots" of concentration for
any species plotted, the software locates and then connects with the terrain, the desired
N-highest grid point concentrations. These locations may be further highlighted using
contrasting colors in both the cloud and on the projections to the lower surface. In
Figure 10 this has been done for the 10 highest concentrations. Alternatively, it might
be useful to highlight only specific locations, for example, to connect only those grid
points over San Francisco.
Figure 11, shows additional snapshots of the ozone concentration, at three hour inter-
vals. The increase in ozone during the day and the movement of the peak concentrations
to the South Bay arc evident. To facilitate these intercomparisons for the viewer, all plots
should be drawn from the same perspective using the same scaling factors, particularly
the proportionality factor relating the number of cloud points to concentration.
Once again, the choice of viewpoint can be important with such graphics. By rotating
the perspective and viewing at a lower angle, a different sense of the distribution can be
achieved (Figure 12). A continuous rotation capability would be highly desirable, but
491
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the computing requirements needed in generating many thousands of 3D points in real
time would tax most computing systems.
Many other refinements of these plots are possible, dictated by the desired applica-
tion. More than a single chemical species can be followed by generating multiple point
clouds at separate vertical levels (Figure 13). If the depiction of the wind field is impor-
tant, wind vectors might also be included at other vertical positions (Figure 14). Particle
trajectories, from point of origin to the time shown might also prove valuable. Software
flexibility is essential since it is usually unlikely that all desired features would have been
foreseen at the outset. Care in the application of these methods is also important since
the user may be saturated by too much information appearing on a plot.
CONCLUSIONS
A variety of examples showing the practical utility of 3D plots in meteorological
and pollution applications has been presented. Such graphics can be of great value in
providing a inore profound understanding of the results of experimental measurements
or of model calculations, particularly to a broader 11011-scientific audience.
Today, computer technology is literally exploding before our very eyes. The area
of computer graphics is achieving particularly impressive growth. Under such circum-
stances, it may be dangerous to predict the future, but I believe it can be safely said
that we will be seeing far more routine use of three dimensional techniques as both in-
creasing software and hardware availability place such tools in the hands of the working
scientist/engineer.
Acknowledgment
This work was performed under the auspices of the U.S. Department of Energy by
the Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.
REFERENCES
1. H. H. Lamb, "Climate, Present Past and Future," Vol 2, Climatic History and the
Future, Methuen & Co., London, 1977.
2. M. C. MacCracken, "Climatic warming and carbon dioxide," Energy & Technology
Review pp 1-17, September 1984.
3. P. D. Jones, et al., "Northern hemisphere surface air temperature variations: 1851-
1984." J. Climate and Applied Meteorology, 25, 161-179 (1086).
4. J. E. Penner, J. J. Walton, and T. Uineda "Air quality model validation: Application
to the San Francisco Bay Area and St. Louis," Air Pollution Control Assoc., 76th
Annual Meeting and Exhibition, Atlanta, GA, June 19- 24, (1983).
492
-------
¦o «
\ '
t 1
14.69 | 3.03 | 4.45
ti
$ }
i /
^ \
JAN
k XT) v
I K^i. |J.e» |a.o7 |4.i« | j.21
•\ . -i
/'/ -d
J / V
.,1 v
|2.e« |3.S3 | 4.07 | jVV/to 2 ',S7 |2^>i K 67
1 -- .f
/ P
12.02 12.35 14.30 §3.10 §2.7?
\ !
11 1.41 | 1.10 | 2 .47 | 2 . 92 |2 >'S0
A
iH
_A\,L
| 1.22 |2.^#.(i.7i i|2.28
I I I I
L0N
-------
Figure 3. 3D distribution of cr(T) for January over NA with 2D symbols and connectors to
the lower surface.
Figure 4. 3D distribution of cr(T) for January over NA with 3D cubes used to locate
points an(i their projections shown on base plane.
494
-------
Figure 5. Four views of a(T) for January over NA.
JULY
I RT I Tl/ii
Figure 6. Four views of <^(T) for July over NA.
495
-------
Figure 7. Quadratic surface fit to January a(T) data for NA, including original data points.
Figure 8. Four views of January quadratic surface for c(T).
496
-------
JANUARY
JULY
p*
100 90
LONGITUDE
Figure 9. Superimpose ct(T) surfaces for January and July.
Figure 10. Early morning distribution of ozone over the San Francisco Bay Area terrain. Ten
highest concentration grid points are highlighted.
497
-------
Figure 11. Ozone distribution over the San Francisco Day Area at different times
2 PM 5 pm
Figure 12. Ozone distribution over the San Francisco Bay Area, second viewpoint.
498
-------
Figure 13. Concentrations of both ozone (top layer) and N02 (middle layer)
over the liay Area.
Figure 14. Ozone concentration cloud and mass flux vectors.
499
-------
SOURCE-RECEPTOR ANALYSIS OF VOLATILE
HYDROCARBONS COLLECTED IN NEW JERSERY
Mardi Klevsa
Air Management Division
U.S. EPA Region V
Chicago, IL 60604
Peter A. Scheff
Pritzker Department of Environmental Engineering
Illinois Institute of Technology
Chicago, Illinois 60616
A Chemical Mass Balance (CMB) receptor model for total non-
methane hydrocarbon concentration (NMHC) was developed based on
ambient measurements of 24 volatile hydrocarbons collected at two
sites in New Jersery. The CMB model was used to quantify the
contributions from petroleum refineries, gasoline vapors, vehicle
exhaust, paint solvents and petrochemical industries to ambient
NMHC. A total of 135 one-hour integrated air samples collected at
0600 and 0800 EDT during July and August were selected for this
study. The CMB equation was solved using a weighted least squares
procedure. Source profiles (mass fractions of the individual 24
hydrocarbons in the emissions from each modeled source category)
were developed from published data.
For the 8 AM samples collected at Linden and Newark, N.J.,
the average contributions to ambient NMHC (defined as the sum of
the 24 individual hydrocarbons) were: 92 and 47 jjg/m from
refineries^ respectively; 83 and 45 ;,g/m from gasoline v^por; 29
and 7 \iq/m from petrochemical industries; 49 and 50 lig/m from
vehicle exhaust; 26 and 23 jig/m from paint solvents; and 77 and
51 tig/m from other sources. A validation of the CMB predictions
for point source contributions showed the results to be consistent
with source geometry and wind direction relationships. For the
early morning samples analyzed in this study, hydrocarbon
reactivity does not have a significant effect on the CMB
predictions.
aThis study was performed by M. Klevs as a graduate student at IIT
and does not reflect the policy of the EPA.
500
-------
SOURCE-RECEPTOR ANALYSIS OF VOLATILE HYDROCARBONS COLLECTED IN
NEW JERSEY
Introduction
Increasing attention is being paid to the chemistry of
organic compounds in the atmosphere. In addition to their toxic
and in some cases carcinogenic effects, many of these materials
play an important role in the photochemistry of air pollution. Any
regulatory strategy aimed at controlling the problems associated
with organic pollutants will require a better understanding of
their emission sources as well as the relationship between
emissions and ambient air quality.
Air dispersion models are a widely used tool for relating the
emission of a pollutant to its ambient air concentration.
Conceptually, these models follow the dispersion of pollutants as
they travel downwind. Great uncertainties in our understanding of
the emissions from the sources of organic pollution, however,
makes applying these models to defining source-receptor relation-
ships for organic materials extremely difficult. An alternate
approach using receptor oriented models has been developed to
predict source-air quality relationship. In contrast to
dispersion models, receptor models start with a measurement of
air quality and by using a variety of mathematical techniques,
predict the relative contribution of each of the major sources of
a pollutant (such as inhalable particulate matter or total non-
methane hydrocarbon, NMHC) from measurements of the composition of
the pollutant at a receptor site.
One type of receptor model is the chemical mass balance
(CMB) or source reconciliation model. ' The CMB requires that the
chemical composition of the pollutant be known in the emissions
from each source category affecting the air quality at a receptor,
and that the chemical composition of a source, or source
fingerprint, be stable to the point where it can be quantitatively
identified at the receptor. CMB models have been applied tg and
validated for particulate matter in a variety of locations. ' '3
The method has also been applied in a more limited form to fit 6
sources6of total hydrocarbons from 9 chemical components in Lo^
Angeles and 5 sources from 15 components in Sydney, Australia .
A recent study in Tokyo, Japan used 18 igdj^idual hydrocarbon
components to resolve 4 sources of NMHC. '
This paper reports on a study of the application of the CMB
to NMHC data collected at Newark and Linden, New Jersey in July
and August of 1980. In this study, 24 individual hydrocarbons
were used to quantify the contributions from petroleum refineries,
gasoline storage facilities, petrochemical industries, vehjgle
exhaust and paint solvents to ambient NMHC concentrations.
Experimental
Data Set. The data for this project were taken from the Northeast
Corridor Regional Modeling Project (NECRMP). For the two receptor
sites selected, Newark represents a high traffic density, city
center location and Linden represents an industrial location.
Note, however, that the two receptor sites are located 16 km apart
501
-------
and many of the major NMHC sources would be expected to impact
both receptors. A map of the area with the locations of the two
receptor sites and major NMHC sources is shown in figure 1. One
hour integrated air samples were collected at 0600 and 0800 EDT
and a total of 135 samples analyzed for the concentration of 24
hydrocarbons were selected for this study. NMHC was defined as
the sum of the 24 individual hydrocarbons. Details of the
sampling, analysis and quality control procedures have been
previously published.
CMB Model. The general equation of the CMB receptor model is:
Y = Z B + E (1)
where Y is a vector of i molecular concentrations, iig/m , measured
at the receptor? Z is the pollution source molecular composition
matrix of i components for each of j sources, g of i/ g of NMHC
from source j; ^ is a vector of j source coefficients, (ig of NMHC
from source j/m ; and E is a vector of i errors. The values of B,
therefore, represent the contributions to the NMHC at the
receptor from the source categories.
Equation 1 was solved using the weighted least squares
procedure (WLS) for each of the 135 air samples evaluated. The
WLS analysis adjusts for unequal variances among the residuals by
normalizing the errors (vector E) by the variance of the
measurements. The standard deviation ( ;) ) of each measurement
was calculated as the product of the molecular concentration and
coefficient of variation (CV) of the analytical technique. A
conservative estimate of the CV for the NECRMP species data of
0.15 was used for this study. The weight is then the inverse of
the square of the measurement y.
The only restriction on the solutions of Equation 1 was that
the source coefficients had to be > 0. For each run, sources with
negative coefficients were dropped from the model, the remaining
non-negative coefficients re-calculated using the reduced model,
and the coefficient for the eliminated source assumed to be zero.
The prediction of negative source coefficients did not cause a
significant problem with this data set.
Source characterization. Five source categories were selected for
the CMB analysis. These categories were chosen because they
represent major sources of NHMC in the study area and reasonable
estimates of their fingerprints could be developed. It should be
noted, however, that some major categories were not included (e.g
printing solvents and pharmaceutical manufacturing). It was not
expected or desirable, therefore that the predicted NMHC (i'.B.) add
up to the measured NMHC. 2,8
The source compositions are shown in Table I. The petroleum
refinery fingerprint was derived from a study of the air
concentrations of hydrocarbon species downwind of an oil
refinery. The gas vapor fingerprint is basedgOn^apors from a
composite sample of summer blend gasoline at 23 C. The
petrochemical fingerprint is based on 36 monthly measurements near
a polyethylene plant in Japan. Vehicle exhaust is based on the
emissions of four different models of cars burning three separate
fuel mixtures. The paint solvent fingerprint is base^on air
samples down-wind of a large automative painting plant.
502
-------
Reactivity. A basic assumption of the CMB form of receptor model
is that the fingerprint from a particular source remain unchanged
from the time of emission to collection. While this assumption
allows for overall decay and deposition, selective decay of
components before collection could distort the finger-print.
Because various hydrocarbons have different reaction rates, the
time between emission and collection of the NMHC should be less
than the time interval which would allow significant relative
changes in concentration due to reactivity. If this is not true,
significant changes in the fingerprints could lead to invalid
predictions. The extent to which this occurs was evaluated by
considering hydrocarbon reactivity in the analysis. The hydroxyl
radical reaction rate constant, kQ„ was used to quantify
hydrocarbon reactivity, and the six most reactive materials (ra-and
p-ethyltoluene, o-ethyltoluene, m-,p-and o-xylene, propylene,
1,2,4-trimethylbenzene, and 1,3,5-trimethylbenzene) were removed
to form a reduced data set. CMB predictions with the reduced data
were developed to test for the effect of selective decay.
Results
Table II shows the average concentrations of the chemical
species selected for the CMB analysis. Included on the table are
the average NMHC concentrations and the reaction rate constants of
the organics with the hydroxyl radical. Table III lists the
average of the source coefficients predicted for each hydrocarbon
sample for the 6 and 8 AM samples from Linden and Newark. There
were a total of 33 valid 6 AM and 8 AM samples from Linden and 35
6 AM and 34 8 AM samples from Newark. The results shown for 24
components represent a summary of solutions with all the
hydrocarbons selected contributing to the model. The 18
components solution represents CMB predictions without considering
the six most reactive materials. For most samples, the sum of the
source predictions was less than the measured NMHC. Given the
number significant sources of VOC not included in the model, this
result was expected. For each sample, the unexplained fraction
which represents the unmodeled sources was calculated as the
difference between the measured NMHC and CMB predictions (EB,).
The unexplained fraction is also shown on Table III.
Discussion
The results summarized on Table III are generally consistent
with receptor site characteristics. Linden, which was considered
the more industrial site, has significantly higher average
contributions from petroleum refineries, gasoline vapor,
petrochemical, paint solvents and unexplained. Looking at the
results as average percent contributions, vehicles represent 14%
and 19% of the 8 AM NHMC at the Linden receptor based on the 24
component and 18 component solutions, respectively. On the other
hand, Newark, considered a city-center site is more dominated by
vehicle exhaust with about 22 and 23% of the NMHC at 8 AM for the
24 and 18 component solutions, respectively.
Hydrocarbon reactivity has a subtle effect on the CMB
predictions. Examining Table I, the 6 most reactive materials are
m-p-ethyltoluene, o-ethyltoluene, 1,3,5 trimethylbenzene, m-p-o-
xylene, 1,2,4-trimethylbenzene, and propylene. Because of their
reaction rate constants, these materials are preferentially
503
-------
removed from the atmosphere. This could result in
disproportionately lower ambient concentrations for these selected
materials. However, Table III does not show a significant
difference between the 24 and 18 component solutions (i.e. the
difference in average source coefficient between the two solution
sets was always less than 5.3% of the measured NMHC). Table IV
shows the correlations between the 24 component solutions and the
18 component solutions. The high correlations on this table show
that both solution sets predict the same day to day variation in
source contributions. It appears, therefore, that for early
morning samples, even in the summer, hydrocarbon reactivity does
not have a significant effect on the CMB predictions.
2
The coefficient of determination (R ) of a multiple
regression model is the square of the correlation between measured
hydrocarbon concentration and predicted hydrocarbon concentration.
It is, therefore, a measure of overall quality of fit of a
regression model. Table V summarizes R of the individual
solutions for the 24 and 18 component CMB models. This table
shows generally higher R (or lower errors) for the 18 component
solutions and, therefore, that the 18 component source profiles
are more representative of the hydrocarbon patterns measured at
the receptor sites than the 24 component profiles. Given the more
homogeneous atmospheric life-times of the 18 component materials,
this result is expected.
The distributions of the daily CMB predictions of NMHC from
the individual sources were compared with each other. It is
interesting to note that most of the correlation coefficients
between daily CMB source predictions are low (r < 0.5). This
suggests that the model is responding to the complex variation in
daily source contributions and resulting hydrocarbon patterns
rather than simply loading all sources in proportion to the total
hydrocarbon concentration.
Figure 1 shows the location of the major hydrocarbon point
sources with respect to the receptor monitoring sites. Because
these sources are not homogeneous throughout the study area,
variations in source impact predictions with wind direction are
expected. Table VI shows the source coefficients averaged by wind
quartile for the combined 6 AM and 8 AM results for the 24
component solutions. A number of points are worth noting. There
is a clear relationship between the location of gasoline storage
facilities and gas vapor source predictions. For example, there
are three major storage facilities SE of the Newark receptor site.
As shown on Table VI, gas vapor predictions are highest for SE
winds. The location of gasoline storage NE and SE of the Linden
site is also shown on Table VI as increased source contributions
from these wind sectors.
The same relationship between source location and CMB
prediction is seen for paint operations. The three major paint
sources are located NE of the Linden receptor and E and SE of the
Newark receptor. The averages on Table VI are consistent with
this geometry. Petrochemical sources are all south of the Newark
receptor and surround the Linden site. Again Table VI shows
results that are reasonably consistent with this source pattern.
However, the relationship between source location and CMB
predictions for refineries is less clear. With a major refinery
point source east of the Newark site, the Newark predictions of
504
-------
major contributions from the SE is not unreasonable. On the other
hand, the prediction of significant refinery contributions from
the SE of Linden do not agree with source location.
One should be cautious in interpreting the wind direction
information. Given its proximity to the ocean, the area is
frequently influenced by sea breezes on summer mornings. The wind
direction information used for this analysis was collected at the
Newark airport, and may not, therefore, be representative of the
actual air flow at the receptors during the morning sampling
periods. A more sophisticated validation proceduj<= using plume
trajectories could not, therefore, be applied. '
conclusions
1. The average prediction of source contributions for the two
receptor sites are consistent with the general characteristics of
the sites.
2
2. Despite the consistently higher R for the 18 component
solutions, there was very little difference in source fraction
explained between the 18 and 2 4 component solution sets. Both
solutions represent the same daily variation in source-receptor
relationships and predict the same average source contributions.
3. In general, the CMB predictions for point source contributions
to the NMHC at both receptor sites are consistent with source
geometry and wind direction relationships. For gasoline storage
facilities, paint operations, petrochemical, and to a lesser
extent, refineries, winds from the areas where point sources are
present show higher contributions from the sources compared to
winds from other directions. These relationships appear to
represent specific source-receptor relationships rather than
generally higher predictions across all source categories
resulting from higher receptor NMHC.
Acknowledgments
We would like to thank Harold G. Richter of the USEPA Office
of Air Quality Planning and Standards for his generous assistance
in providing the NECRMP species data. We also thank Bill Oliver
of Systems Applications Inc. for the update to the VOC species
manual and Barry Bolka of Region V EPA for the emission inventory.
References
1. G.E. Gordon, "Receptor Models", Environ. Sci. and Technol¦
14:792 (1980).
2. P.A. Scheff, R.A. Wadden and R.J. Allen, "Development and
Validation of a Chemical Element Mass Balance for Chicago",
Environ. Sci. and Technol. 18:923 (1984).
3. M.S. Miller, S.K. Friedlander and G.M. Hidy, "A Chemical
Element Balance for the Pasadena Aerosol", Colloid
Interface Sci. 39:165 (1972).
4. G.R. Cass and G.J. McRae, "Source-Receptor Reconciliation of
Routine Air Monitoring Data for Trace Metals: An Emission
505
-------
Inventory Assisted Approach", Environ. Sci. and Technol.
17:129 (1983).
5. R.K. Stevens and T.G. Pace, "Status of Source Apportionment
Methods: Quail Roost II" in Receptor Methods Applied to
Contemporary Pollution Problems, S.C. Dattner and P.K. Hopke,
eds., Air Pollution Control Association, Pittsburgh, PA. pp.
46-59, 1983.
6. c.E. Feigley and J.H. Jeffries, "Analysis of Processes
Affecting Oxidant and Precursors in the Los Angeles
Reactive Pollutant Program", Atmos Environ. 13:1369 (1979).
7. P.F. Nelson, S.M. Quigley, and M.Y. Smith, "Sources of
Atmospheric Hydrocarbons in Sydney: A Quantitative
Determination Using A Source Reconciliation Technique", Atmos
Environ. 17:439 (1983).
8. P.A. Scheff, and R.A. Wadden, "Predicting Unidentified and
Secondary Sources with Chemical Mass Balance Receptor Models"
in Receptor Methods for Source Apportionment, T.G. Pace,
editor. Air Pollution Control Association, Pittsburgh, PA.
pp. 78-93 1986.
9. H.G. Richter, "Analysis of Organic Compound Data Gathered
During 1980 In Northeast Corridor Cities" U.S. Environmental
Protection Agency EPA-450/4-83-017 (1903).
10. M. Klevs, "Source-Receptor Analysis of Volatile Hydrocarbons
Collected in New Jersey", M.S. Thesis, Illinois Institute of
Technology (1986).
11. K. Sexton and H. Westberg, "Photochemical Ozone Formation
from Petroleum Refinery Emissions", Atmos. Environ. 17:467
(1983) .
12. W.R. Oliver and S.H. Peoples, "Improvement of the Emission
Inventory for Reactive Organic Gases and Oxides of Nitrogen
in the South Coast Air Basin," Prepared for the Air Resources
Board, Sacramento, CA, Contract 076-32 (1985).
13. R.A. Wadden, I. Uno and S. Wakamatsu, "Source Discrimination
of Short-term Hydrocarbon Samples Measured Aloft", Environ.
Sci. and Technol., (in press).
14. F.M. Black and L.E. High, "Composite of Automobile
Evaporative and Tailpipe Hydrocarbon Emissions", J^ Air Poll.
Cntl Assoc., 30:1216 (1980).
15. K. Sexton and H. Westberg, "Ambient Hydrocarbon and Ozone
Measurements Downwind of a large Automotive Painting Plant.
Environ. Sci. and Technol. 14:329 (1980).
16. R. Atkinson, K.R. Darnall, A.M. Winer, A.C. Lloyd and J.N.
Pitts, "Reactions of the Hydroxyl Radical with Organic
Compounds in the Gas Phase", In Advances in Photochemistry,
J.N. Pitts, G.S. Hammond, K. Gollnick and D. Grosjean, eds,
Vol II, pp 375-488, John Wiley, New York, 1979.
506
-------
Table I Hydrocarbon Source Fingerprints
Weight %
Gasoline
Petro-
Vehicle
Component
Refinery
Vapor
chemical
Exhaust
Paint
ethane
1.88
.26
3 . 0
5. 03
_a
ethylene
. 52
-
50 . 0
10.08
-
acetylene
.01
—
1.8
2 . 32
—
propane
11.57
2.50
4 . 3
2.24
-
propylene
. 56
—
3.9
2 . 06
—
i-butane
5. 16
14.65
2 . 6
1. 58
-
n-butane
20. 29
34.21
5.5
11.94
-
i-pentane
21. 67
32 . 09
4 . 0
12.52
-
n-pentane
8 . 55
10.28
2.8
—
—
2-methylpentane
8.78
-
1.5
3.12
.71
3-methylpentane
5. 28
2.34
1.1
1.56
.59
n-hexane
4.55
1.83
4.3
1.02
1.13
benzene
1. 63
.76
3.4
8 . 54
—
n-heptane
2.19
. 27
.0
1. 07
9 . 14
toluene
4 .02
.55
7.7
22 . 28
70. 68
n-octane
—
. 02
. 0
.89
5.46
ethylbenzene
. 60
. 04
1.6
1. 84
5.99
p,m,o-xylene
2 .32
. 14
2.5
7.23
.25
n-nonane
.11
.01
-
.44
—
n-propylbenzene
-
-
-
.68
.71
m,p-ethyltoluene
. 16
—
—
•
2 .25
1,3,5-trimethylbenzene.00
.00
-
-
.77
o-ethyltoluene
. 11
.02
. 65
1,2,4-trimethylbenzene.05
.02
-
3 . 54
1.66
100.00
100.00
100.0
100.00
100.00
aNot measured, however, assumed to be zero for CMB calculations.
507
-------
Table II Average Concentration and Reactivity for Selected
Hydrocarbons
Average Concentration, ng/ra3
Linden Newark kOHa
Component
6 AM
8 AM
6AM
SAM
ethane
50.8
16. 4
14.1
11. 2
1.7X1011
ethylene
acetylene
19.2
5.4
17.8
6.5
6.3
6.2
7 . 3
7.4
4.9x10^
4.1x10
propane
propylene
34 . 4
6.2
22.4
8.2
11.5
6.3
10.1
5.6
12
1.lxior^
1.5x10
i-butane
n-butane
33.9
59.3
21.8
49 . 9
10.7
21.8
11.8
25.3
12
1.6x10,,
2.0x10
i-pentane
n-pentane
68 . 0
50.0
52 . 5
28.9
25.2
11.0
29.8
13 . 3
12
2.1x10,,
3.0x10
2-methylpentane
3-methylpentane
20. 1
12 . 5
13 . 6
8.7
7.4
4 . 9
7.7
5.0
12
3.0x10,,
4.1x10
n-hexane
benzene
14 . 8
9 .1
13 . 4
9.0
5.3
5.2
5.7
6.0
12
3 . 5x10,,
8.5x10
n-heptane
toluene
5.3
38.0
5. 1
37.9
2.9
23 . 3
3.8
29. 5
12
3.7x10,
3.7x10
n-octane
ethylbenzene
2 . 6
6.8
1.9
6.3
1.1
5.3
1.5
5.5
12
4.9x10,,
4.9x10
h
p,m,o-xylene
n-nonane
18. 6
1.5
17. 2
1.5
14.3
1.3
17.4
1.7
13
1.3x10,,
4.3x10
n-propylbenzene
m,p-ethyltoluene
1.7
5.8
1.5
5.5
1.2
4.4
1.0
5.5
5 . 8xl0^c
1.8X10
1,3,5-trimethylbenzene
o-ethyltoluene
1 . 2
7.1
1. 2
6 . 4
1.2
5.7
1.3
6.4
13
5.2x10,^
1.3x10
1,2,4-trimethylbenzene
NMHC
2.7
475.0
2 . 9
357.2
2.5
199. 1
2 . 8
222 . 6
13
3.5x10
a 3
cm /mole'sec; from reference 16.
m-xylene
m-ethyltoluene
508
-------
Table III Summary of CMB Results.
, , 3
Source Coefficient, ug/m
Number
of
LINDEN Components
6
AM
8
AM
Average( o)
Range
Average( o )
Range
Refinery
24
141
(233)
0
- 1310
92
(71)
0 -
¦ 356
18
124
(202)
0
- 1150
80
(65)
0 -
- 325
Gas Vapor
24
152
(350)
0
- 1680
83
(122)
0 -
¦ 616
18
171
(373)
7
- 1870
90
(122)
7 -
¦ 617
Petrochemical
24
29
(32)
0
96
29
(31)
0 -
- 150
18
24
(31)
0
- 101
21
(19)
0 -
- 66
Vehicle
24
62
(49)
0
- 252
49
(32)
0 -
- 96
18
79
(98)
0
- 550
68
(61)
0 -
- 275
Paint
24
22
(24)
0
- 100
26
(43)
0 -
- 245
18
17
(20)
0
84
20
(36)
0 -
- 212
Unexplained
24
65
(283)
-1370
- 508
77
(77)
-4 2 -
- 291
18
56
(276)
-1400
- 314
79
(71)
11 -
- 323
NEWARK Average( a ) Range Average(g ) Range
Refinery
24
52
(71)
0 -
406
47
(40)
0
- 193
18
50
(65)
0 -
368
44
(38)
0
- 187
Gas Vapor
24
33
(36)
0 -
149
45
(45)
8
- 222
18
35
(36)
0 -
149
47
(45)
9
- 222
Petrochemical
24
6
(10)
0 -
34
7
(10)
0
- 53
18
5
(8)
0 -
26
5
(9)
0
- 48
Vehicle
24
38
(40)
0 -
187
50
(42)
0
- 143
IB
43
(50)
0 -
253
52
(45)
0
- 148
Paint
24
16
(20)
0 -
90
23
(23)
0
- 94
18
13
(17)
0 -
68
19
(20)
0
- 84
Unexplained
24
54
(38)
11 -
188
51
(38)
16
- 181
IB
53
(40)
13 -
195
55
(41)
21
- 202
509
-------
Table IV Correlations Between the 24 and 18 Component Solutions
Linden Newark
Source
6 AM
8
AM
6 AM
8 AM
Gas Vapor
0.99
0,
.97
0.99
0.99
Refinery
0.99
0,
. 97
0.99
0.99
Petrochemical
0. 87
0,
. 89
0.94
0.96
Vehicle exhaust
0.91
0,
. 62
0.97
0.97
Paint
0.86
0,
.98
0.97
0.99
Table V Summary of the Coefficient of Determination for the
24 and 18 Component Solutions
Number of
Site
Hour
Components
Median
Min
Max
Linden
6
24
0.745
0.047
0.801
18
0 . 826
0.334
0.941
8
24
0.741
0. 255
0.821
18
0.842
0. 304
0.906
Newark
6
24
0.706
0. 183
0. 770
18
0.814
0.228
0.883
8
24
0.721
0. 321
0.778
18
0.838
0. 343
0.884
510
-------
Table VI Source Coefficients Averaged by Wind Quartile
Average !
Source
Coefficient3 (uq/
3. .
m ) by
Wind Quartile
LINDEN
NE
SE
SW
NW
ALL
DIRECTIONS
Refinery
80
201
104
96
117
Gas Vapor
121
312
59
44
118
Petrochemical
18
31
31
36
29
Vehicle exhaust
43
63
58
54
55
Paint
38
21
18
24
24
NEWARK
Refinery
50
79
41
36
49
Gas Vapor
35
62
30
37
39
Petrochemical
4
7
9
4
6
Vehicle Exhaust
51
66
38
29
44
Paint
26
27
14
18
20
a 24 chemical solutions
511
-------
5 UOO
m e t ers
~ RECEPTOR SITE
A GAS VAPOR
O REFINERY
~ PAINT
O PETROCHEMICAL
>1 V\'9e^-C-°;
/ / ^
NEWARK
Union
LINDEN
csex
OOO
Figure 1. Locations of receptor sites and VOC sources.
512
-------
ESTIMATING SPECIFIC SOURCE EXPOSURES TO TOXIC
AIR POLLUTANTS
Sylvia A. Edgerton
Department of Environmental Science, Battelle Columbus Division,
Columbus, Ohio
The evaluation of the extent to which a chemical, or a class of chem-
icals, presents a health hazard to the public relies on an accurate
assessment of human exposure to that chemical. To control emissions
of toxic substances effectively, the source of exposure must be iden-
tified. Exposure models have been developed which assess total exposure
from all sources to a chemical. Source-receptor models can identify
source contributions to the concentration of a chemical in an individual
environment. A Source Exposure Model (SEM) is developed here which
combines both types of models to give estimates of human exposure
to chemicals from specific source categories. The SEM combines the
Chemical Mass Balance receptor model with a discreet form of exposure
model, and provides an assessment of the fraction of total chemical
exposure due to various source types.
A simplified form of the SEM is applied in a snail residential commu-
nity to assess atmospheric exposure to fine particles and benzo(a)pyrene
indoors and outdoors from both automobiles and woodburning stoves.
Atmospheric tracers are used to estimate source contributions.
513
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ESTIMATING SPECIFIC SOURCE EXPOSURES TO
TOXIC AIR POLLUTANTS
INTRODUCTION
A human exposure model and a source-receptor model are combined to
form a Source Exposure Model (SEM) which can he used to estimate
human exposure to specific source categories. This type of information
is useful in targeting source categories for regulatory efforts.
Personal exposure information may be obtained by the use of personal
monitoring equipment which is worn on the individual, or by estimation
of exposure through theoretical models using concentration information
from fixed monitoring sites in many different environments, together
with activity profiles of the movements of the individual in and
out of those environments. The exposure of an individual to a pollutant
is a measure of pollutant concentration available to the body, while
the dose is the actual quantity that enters the body. Exposure calculations
are used to estimate dosages.
METHODOLOGY
The total exposure is the product of the concentration of pollutant
times the length of exposure. Since the length of exposure in a
microenvironment may vary from a few minutes to many hours, the concentra-
tion information must be representative of the concentration over
the particular period of individual exposure. The average integrated
exposure to a pollutant, E, of an individual may be calculated by
summing over the time periods t^ spent in each microenvironment k
that the person encounters during a dayl;
E = £ c t , (1)
k k k
where C|< is the concentration of the pollutant in the microenvironment
k during period t^. For the integrated exposure to be truly represent-
ative of the dosage received, the measured concentration must be
determined specifically for each period t^. In fixed site monitoring,
a sampling period should be chosen over which concentration fluctuations
are small and therefore the measured concentration is representative
of the exposure within the period. For example, concentration of
inhalable particulate material averaged over 24 hours may underestimate
a short 1 hour exposure by a factor of 2 to 3. Nephelometry readings
may be examined for periods of maximum acceptable concentration fluc-
tuation and used to determine the sampling period of the fine particulate
material or gases related to the fine particles.^
In the Source Exposure Model (SEM), the average individual exposure
to a pollutant from source j over period i, Ejj is:
Eji = 1//ni J sjik tik,
where tj^ is the number of hours spent in microenvironment k during
period i, Sjj^ is the contribution of source j to the pollutant in
microenvironment k during period i as determined by the 0MB and n,-
is the number of hours in each period i. In the application of the
514
-------
SEM presented here, the sampling period is 4 hours (n-j = 4). For
non-continuous sampling, the sampling period is generally equal to
or greater than the minimum activity profile period to assure that
it is representative of the exposure concentration (nj > t^ minimum).
A typical minimum activity profile period is one hour since 1) detailed
activity dairies over time periods shorter than one hour are difficult
to maintain, and 2) sampling periods for toxic pollutants of less
than one hour are often not practical both for analytical and economic
reasons.
Where unique tracer characterizations nay be found to represent a
source of interest, the jth source contribution during period i in
the microenvironment, Sj-j^ is:
5jik = ajk C"Tik' ^
where aj^ is the ratio of the pollutant concentration to the tracer
T concentration in source j in microenvironment k, and is the
concentration of the tracer T during period i in microenvironment
k. The average individual exposure to source j during period i then
becomes:
Eji = 1/nj l ajk CTik tik.
If a is invariant with k, it may be removed from the summation.
In this case, the exposure to a pollutant from source j may be directly
ascertained with the use of personal exposure badges over any time
period, and
Ej = aj CT' (5)
The daily average individual exposure for person type p, with person
type being defined as a category of individuals with similar activity
diaries (e.g. office worker), to the pollutant from source j, E(D)pj(
is:
E(D)Pj = 1/24 E n. Ejf, (6)
The dally weighted population exposure to the pollutant from source
j, P, is:
Pj = 1 fp Epj' (7)
P
where fp 1s the fraction of person type p in the population. A weigh-
ing factor may also be included here to represent relative risk to
varying types within the population, e.g. the very young, sick or
elderly. An annual weighted population exposure may also be calculated
1n a similar manner. The weighted population exposure may be used
in risk assessment models to determine if regulatory control should
be initiated on a particular source of a pollutant.
MODEL APPLICATION
A simplified form of the SEM was applied to assess source exposures
to automobiles and residential woodburning in a small community near
Portland, Oregon. Through the use of gaseous tracers in a receptor
model, these two sources have previously been determined to be the
major wintertime contributors to fine particulate pollution in the
515
-------
residential neighborhoods of this community3.
The contribution from automobiles and wood stoves to the ambient,
outdoor fine particle and benzo(a)pyrene (BaP) concentrations were
estimated by applying a two component Chemical Mass Balance Model.
The gases methyl chloride (CH3CI) and carbon monoxide (CO) were used
as surrogate tracers for these sources. Methyl chloride has been
shown to be a unique tracer for wood combustion in residential neighbor
hoods 2-4 B0th woodburning and automobiles contribute to the local
carbon monoxide concentrations. The value for a (woodburning) in
equation (3) an(j (4) was experimentally determined for the ambient
outdoor environment 5, f^e value for a (automobiles) was taken from
calculations based on the local traffic mix
Typical indoor concentrations of woodsmoke in homes where there is
wood being burned were estimated from previous studies The
concentrations vary widely between the individual homes and fluctuate
greatly over the day. The highest concentrations occur during the
stoking of the fire, as indicated by spikes in the CO concentrations.
An average indoor concentration of woodsmoke during periods of wood-
burning is 20 pg/m3. A survey has shown that of those who burn wood
(56 percent of the population in this community do), 23 percent of
wood stove burners burn all day on the weekdays and 44 percent burn
all day on the weekends 9. yhe simplifying assumption is made that
there is no infiltration of particulate material from outdoors into
homes.
Source exposures are estimated for two categories of people: an
office worker and a person who spends most of the day at home, such
as a homemaker or elderly person. The activity patterns for these
two types are taken from studies of population mobility It is
assumed that the employed person (office worker) spends one hour
in the morning and evening period outdoor in transit to and
from work and one hour during the lunch period in the outdoor envi-
ronment. The transit mode and outdoor environment are considered
to be the same. The unemployed person spends two hours in the after-
noon in transit and in outdoor activities.
The contribution of woodburning to the fine particle concentration,
Sjik to which a person in each category is exposed during each period,
t1|() is shown in Table 1 and Table 2 for persons living in woodburning
households (WB), and non-woodburning households (NWB). The daily
average exposures, E(D), for each category, are calculated using
equation (6) and shown in the tables. For the employed person, the
average daily exposure to woodsmoke is 13 pg/m3 for the individual
in the woodburning home. The corresponding concentration for the
unemployed person is 18 pg/m3 in the woodburning home and 1 ug/m3
in the non-woodburning home. Despite the higher concentrations in
the outdoor ambient air, the indoor exposures dominate the total
dosage of woodsmoke that an individual receives over the day. A
similar calculation for the average daily exposure to auto exhaust
gives a value of 1 pg/m3 for both the employed and unemployed. Assum-
ing 60 percent of the population can be classified as employed and
40 percent as "at home", the weighted population exposures, Pj from
equation (7), to fine particles from woodsmoke and auto exhuast are
9 pg/m3 and 1 ug/m3 respectively.
The source exposure model may be applied to calculate exposures to
516
-------
toxic compounds from specific sources, if the ratio of the compound
to the tracer, a, in that source is known. Such a calculation has
been carried out for exposure to benzo(a)pyrene (BaP). The ratio
for BaP to methyl chloride in woodsmoke is calculated from the ratio
of fine particles to methyl chloride used above and a value for the
ratio of BaP to fine particles of about 0.06 percent 11,12, /\n
estimate for the value of. about 0.001 percent for BaP to fine particles
in auto exhaust is from the literature The weighted population
exposure to BaP from woodburning and auto exhaust is 5 ng/irr and
.01 ng/m^ respectively. The weighted population exposures to
fine particles and BaP from woodburning and from automobiles is shown
in Table 3.
The weighted population exposure may be used in risk assessment models
to calculate the contribution to health risk of toxic chemicals from
specific sources. This type of assessment is useful for targeting
sources for regulatory control. The weighted population exposure
to BaP calculated above, for example, may be converted to an average
daily intake of BaP using a value for daily air inhalation of 19
m^/day 14. The average wintertime daily intake of BaP is calculated
to be 100 ng/m^ from woodsmoke and 0.2 ng from auto exhaust. This
is compared with a recommended daily intake of 48 ng. A comparison
of BaP intake from other sources is shown in Table 4.
This simple application illustrates the use of the Source Exposure
Model to evaluate the health hazard of toxic chemicals in the environment.
A more thorough application of the model may include many more chemicals,
chemical sources, people types, microenvironments, transport mechanisms
between microenvironments, and risk factors. With the increasing
awareness that many chemical exposures occur in environments other
than that of the outdoor ambient air, this type of model should find
increasing applicability in the assessment of public health hazards
from toxic chemicals.
Acknowledgments
This work was supported in part by the U.S. Environmental
Protection Agency. Additional support was provided by the
Biospherics Research Corp. and the Andarz Co.
REFERENCES
1. W. R. Ott. "Concepts of Human Exposure to Environmental
Pollution," SIMS Technical Report No. 32. Stanford,
Calif., Stanford University, Department of Statistics
(1980).
2. S. A. Edgerton, M. A. K. Khalil and R. A. Rasmussen.
"Methodology for Collecting Short Period Integrated
Gas Samples: Estimating Acute Exposure to Woodburning
Pollution," J. Environ. Sci. Health, A 20(5), pp.
563-581 (1985T
3. S. A. Edgerton. "Gaseous Tracers in Receptor Modeling:
Methyl Chloride Emission from Wood Combustion," Ph.D.
517
-------
dissertation, Oregon Graduate Center, Beaverton, Oregon
(1985).
4. M. A. K. Khalil, S. A. Edgertor and R. A. Rasmussen.
"A Gaseous Tracer Model for Air Pollution from
Residential Woodburning," Environ. Sci. Technol., 17,
pp. 555-559 (1983).
5. S. A. Edgerton, M. A. K. Khalil and R. A. Rasmussen.
"Source Emission Characterization of Residential
Wood Burning Stoves and Fireplaces: Fine Particle/
Methyl Chloride Ratios for Use in Chemical Mass
Balance Modeling," Environ. Sci. Techno!., in
press (1986).
6. Metropolitan Service District estimate for Portland,
Oregon (1984).
7. D. J. Moschandreas, J. Zabransky and H. E. Rector,
"The Effects of Woodburning on the Indoor Residential
Air Quality," Environ. Int., 4^, pp. 463-468 ( 1980).
8. John E. Core, John A. Cooper and James E. Houck, "A
Study of Residential Wood Combustion: Task 7,
Indoor Residential Sampling Program," NEA Inc.,
Beaverton, Oregon. Final Report to the U.S.
Environmental Protection Agency, Region X (1981).
9. Carol Cummings. "Portland Area Wood Heat Survey,"
Oregon Department of Environmental Quality, Air
Quality Division (1982).
10. A. Szalai. The Use of Time. Mouton Press, Paris
(1972).
11. Lars Rudling, Bengt Ahling and Goran Lofroth.
"Chemical and Biological Characterization of Emissions
from Combustion of Wood and Wood-Chips in Small Furnaces
and Stoves," in Residential Solid Fuels, J. A. Cooper
and D. Malek, eds., pp. 34-53, published by Oregon
Graduate Center (1982).
12. Thomas Ramdahl, Ingrid Alfheim, Stale Rustad and
Torbjorn Olsen, "Chemical and Biological Characterization
of Emissions from Small Residential Stoves
Burning Wood and Charcoal," Chemosphere, 11, pp. 601-611
(1982).
13. Jean L. Muhlbaier and Ronald L. Williams, "Fireplaces,
Furnaces, and Vehicles as Emission Sources of
Particulate Carbon," presented at the International
Symposium on "Particulate Carbon: Atmospheric Life
Cycle," General Motors, Warren Michigan (1980).
14. International Commission of Radiological Protection.
"Report on Task Group of Reference Man," Pergamon
Press, N.Y. (1974).
518
-------
Philip H. Howard, Joseph Santodonata, Dipak Basu
and Robert Bruce, "Multimedia Human Exposure to
Polycycllc Aromatic Hydrocarbons and Their Association
with Cancer Risk," in Residential Solid Fuels,
pp. 620-647, J. A. Cooper and D. Makek, eds.,
published by Oregon Graduate Center (1982).
519
-------
TABLE 1. DAILY INTEGRATED EXPOSURE TO WOODSMOKE
FOR PERSONS EMPLOYED INDOORS IN OFFICE
BUILDINGS
Microenvironment (ME)
(# hours spent in ME
in period 1,2,3,4)
s j i k
Concentration of Fine Particles from
Woodburning pg/m^
Period 1 Period 2 Period 3 Period 4
6-10am 10am-6pm 6pm-2 am 2-6am
r,i
4
WB*
NWB
_T
WB
NWB
WB
8
NWB
4
WB
NWB
k
tik
(i = 1,2,3,4)
Home
(2,0,7,4)
20
0
20
0
20
0
10
0
Work
(1,7,0,0)
0
0
0
0
0
0
0
0
Street
(1,1,1,0)
29
29
19
19
42
42
24
24
Average
fQr Period
17
7
2
2
23
5
10
0
Total Dai1y Average:
E(D;
WB Household
NWB Household
13 ng/nH
4
TABLE 2. DAILY INTEGRATED EXPOSURE TO WOODSMOKE FOR
PERSONS WHO SPEND MOST OF THE DAY IN THE
HOUSE
Microenvironment (ME)
(# hours spent in ME
in period 1,2,3,4)
S iik
Concentration of Fine Particles from
Woodburning pg/m^
Period 1 Period 2 Period 3 Period 4
6-10am 10am-6pm 6pm-2am 2-6am
m
4
WB*
NW
8
WB
NWB
8
WB
NWB
4
WB
NWB
k
ti k
(1 = 1,2,3,4)
Home
(4,6,8,4)
20
0
20
0
20
0
20
0
Street
(0,2,0,0)
29
29
19
19
42
42
24
24
Average
for Period
20
0
20
2
20
0
10
0
Total Daily Average;
E(D]
WB Household
NWB Household 1 |ig/m"^"
*WB means woodburning household and NWB means non-woodburning household
520
-------
TABLE 3. POPULATION WEIGHTED SOURCE EXPOSURES TO FINE
PARTICLES AND BENZO(a)PYRENE FROM WOODBURNING
AND AUTO EXHAUST IN A RESIDENTIAL NEIGHBORHOOD
DURING THE WINTER
Woodburning
Auto Exhaust
Fine Particles pg/m^
9
1
Benzo(a)pyrene ng/m^
5
.01
TABLE 4. AVERAGE DAILY EXPOSURE TO BaP FROM WOODSTOVES AND
AUTOMOBILES, CALCULATED WITH THE SOURCE EXPOSURE
MODEL COMPARED WITH ALLOWABLE DAILY INTAKE AND
EXPOSURE FORM OTHER SOURCES 15.
Daily BaP Intake
Allowable Daily Intake
48 ng
Woodstoves
100 ng
Automobiles
0. 2 ng
Food
160 - 1600 ng
Smoking
400 ng
521
-------
PERFORMANCE AND RESULTS OF THE ANNULAR DENUDER SYSTEM IN
THE SAMPLING AND ANALYSIS OF AMBIENT AIK NEAR LOS ANGELES
.1. E. Sickles, II
Research Triangle Institute
Research Triangl.11. Park, North Carolina
C. Perrino, I. Allegrini, A. Febo and M. Possanzini
Consiglio Nazionale delle Ricerche
Rome, Italy
R. J. Paur
U.S. Environmental Protection Agency
Research Triangle Park., North Carolina
Airborne gaseous and particulate chemical species contribute to acid
deposition. Among them are gaseous nitric acid (HNOj), nitrous acid (HNO2)
ammonia (NH3), and sulfur dioxide (SO2); and particulate nitrate (NO3),
sulfate (SO/;-) , and ammonium (NH^). Accurate measurements of the atmospher-
ic concentrations of these chemicals are needed to facilitate an understand-
ing of the important chemical and physical processes that lead to acid depo-
sit ion.
Although commercially available instrumentation is available to monitor some
of these pollutants, the sensitivity is frequently inadequate at concentra-
tions typical of nonurban sites. As a result, researchers have devised sev-
eral approaches to determine the ambient levels of these pollutants. A
methods' intercomparison study was conducted from September 11 to 19, 1985 011
the Pomona College Campus at Claremont, California near Los Angeles. Approx-
imately 20 different research groups participated, using various state-of-the-
art methods for sampling and analyzing ambient air. This paper describes the
performance of the annular denuder system (ADS) anil presents results collected
using the system during this study.
522
-------
PERFORMANCE AND RESULTS OP THE ANNULAR DENUDER SYSTEM IN
THE SAMPLING AND ANALYSTS Of AMBIENT AIR NEAR LOS ANGELES
Int roduct" i on
Airborne gaseous and particulate chemical species contribute to acid
deposition. Among them are gaseous nitric acid (HNO3), nitrous acid (HNO2),
ammonia (NH3), and sulfur dioxide (SO2); and particulate nitrate (NO3),
sulfate (SO^~), and ammonium (NH^). Accurate measurements of the atmospheric
concentrations oE these chemicals are needed to Facilitate an understanding of
the important chemical and physical processes that lead to acid deposition.
Although commercially available ins!'r iincnr at. i 011 is available to monitor
some of these pollutants, the sensitivity is frequently inadequate at concen-
trations typical of nonurban sites. As a result, researchers have devised
several approaches to determine the ambient levels of these pollutants. A
methods' intercomparison study was conducted from September 11 to 19, 198") on
the Pomona College campus at Claremont, California near T.os Angeles. Approxi-
mately 20 different research groups participated, using various state-of-the-
art methods for sampling and analyzing ambient air. This paper describes the
performance of the annular denuder system (ADS) and presents results collected
using the system during this study.
Experimental
The ADS was developed by the Istitito Inqu i naimint o Atmosferico of the. C011-
siglio Nazionale delle Ricerche (CNR) of Rome (Italy). As illustrated in Fig-
ure 1, the ADS is a denuder-filtor pack assembly for the simultaneous collection
of atmospheric trace gases (i.e., HNO3, HNO2, SO^, and NH-j) and fine particles
(i.e., NO3 , SO^-, and Nll^). Two denuder-ifi 1 ter pack sampling trains are
contained in a weatherproof box. Air enters the ADS at 15 1 pin through a Teflon
cyclone (2.1) ;im cut size) and flows through a Teflon manifold sequentially into
one of the two denuder-fi1ter pack sampling trains. Sampled air contacts only
Teflon surfaces or the coated glass surfaces of the denuder tubes. The compo-
nents of each train are assembled with threaded rings and connectors. In each
train, air passes through: two Na2COj-coated, 22 cm-long annular denuders (AD)
to collect HNO3, HNO2, and SO2; one citric acid-coated, 13 cm-long AD to collect
NH3; a 47 mm diameter Teflon 2 pm pore size filter to collect fine particles (NO3,
S0jj~, and Nll£) ; a 47 mm diameter I pn pore size nylon filter to collect nitrate
volatilized as HNO3 from the Teflon Eilter; a citric ac i.d--coated 13 cm-long AD
to collect ammonium volatilized as NH3 from the Teflon filter; and .1 micropro-
cessor-controlled air sampler.
In each annular denuder, air is drawn under laminar fLow conditions through
the annular space between two concentric glass cylinders coated with a chemical
appropriate for retention of the trace gas of interest. The walls of the denuder
are etched so that the surface area available for chemical coating is increased.
As the sample stream passes through the annular apace, the gaseous species travel
by molecular diffusion from the bulk gas to the reactive surface and are
collected. The collection efficiency of an annular denuder depends on the air
Elow rate, the tube length, and or. the inner and outer tube diameters. At
equivalent tube lengths and outer tube diameters, larger sampling rates are
achievable with annular denuders l.han with open tube denuders (I). The capacity
of the denuder is in the milligram range (2).
523
-------
The denuder removes reactive gaseous molecules from air samples. Parti-
cles are collected on back-up filters, minimizing artifact formation from gas-
particle interactions on the filter surface. Di.fEusi.onal and inertial deposi-
tion of particles at the denuder inlet has been shown to be negligible (1,2).
The transit time of air through the denuder is short (< 0.1 sec); this retards
the reestablishment of a gas-particle equilibrium that is appreciably different
from that existing in the sampled atmosphere (3).
Samples collected with denuders and with filters were extracted in virgin
Nalgene containers with distilled water and subsequently analyzed. The extract
solutions were analyzed for NO3 and So£~ by ion chromatography, and for NO^" and
by colorimetry (4,5). Other substances deposited on the denuder may give
rise to the formation of the same ions: for example, the sorption of NO2 and
PAN on an Na2C03~coated denuder produces nitrite, which interferes with the
measurement of HNO2; deposition of particulate matter containing sulfates
nitrate interferes with the measurement of SO2 and HNO3 (2,6). The collection
of the interfering species is small (1-3 percent). By placing two denuders in
series, the amount collected on the first one will he approximately equal to
that found on the second one, which can be used to correct data obtained from
the analysis of the first denuder. The use of two devnulers in series then
permits the simultaneous analysis of several acidic compounds over a wide range
of gas-to-particIe analyte ratios.
The filter extractions and the bulk of the chemical analyses were per-
formed by Global Geochemistry of Canoga Park, California. The denuder extract
volume was 10 mL, and the filter extract volume was 20 inL. The units on the
species concentrations in the liquid extract solutions are reported in ug/tnL.
By combining the liquid species concentration, the extract volume, and the sam-
pled air volume, an ambient air species concentration may be computed and
expressed in ug/m^.
The air sampler, specifically developed for the ADS, consists of a mem-
brane pump and a microprocessor. The measurement of the flow rate is achieved
by measuring the pressure drop, the temperature across a downstream orifice,
and atmospheric pressure by means of suitable electronic transducers. Data are
sent to the microprocessor, which corrects the flow rate to normal temperature
and pressure (20°C and 760 mm Hg). By integration of the flow rate, the volume
of air which, has been sampled is obtained. The microprocessor adjusts a valve
to achieve a constant inlet flow rate regardless of temperature, air pressure,
and the pressure drop across the filter pack.
Tn the current study, two ADS's were used for collocated sampling. The
sampling flow rate was 15 1pm. Two types of sampling periods were used. Short
duration samples were collected for the following periods: 0000-0600; 0800-
1200; 1200-1600; 1600-2000; and 2000-0000 PUT. Long duration samples were col-
lected from 0800 to 2000 and from 2000 to 0600 PI)T. This arrangement permits
comparison of the sum of two or three short duration samples with the corre-
sponding long duration sample. In the current study, one ADS was used to col-
lect short duration samples, while the second was used simultaneously to col-
lect either short or long duration collocated samples.
Per formance
Several measures were taken to assure that the data collected with the ADS
were of both high and known quality. Results of these studies are highlighted
iu the following paragraphs.
524
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Analytical Quality Control
Quality control (QC) solutions for NllJ, NO2, NOj, and SO/-- were prepared
independently of the routine calibration standards and analyzed daily to deter-
mine if the analytical results were biased. The concentrations of these QC
samples were chosen to be representative of those, found in the authentic envi-
ronmental samples. The concentration of each species found was compared with
the amount expected, and a percent recovery was determined. These results may
be used to infer 95 percent confidence intervals for the species recoveries (x
t 2a, where n = 85): 100 * 2.7 % for NllJ; 98 f 9.9% for N<>2; 102 8.2 X for
NOj, and 102 ± 3.7X for S0^~. These find ings show quant it ative recovery with
very good precision and suggest that there was no bias Ln the analyses.
Replicate Analyses
Samples collected on each day of the study were selected for replicate
analyses to provide estimates of analytical precision. Between 22 and 33
paired comparisons were considered for NH£, NO2, NO^ and S0^~. For each pair
of data, a mean and a coefficient of variation (CV - lOOs/x) were computed.
The average of the individual GV's is 6 percent or less for each species.
The individual data were ordered by mean concentration, and average CV's
were determined for the upper and lower concentration quartiles for each spe-
cies. Comparison of these results shows no appreciable difference for NllJ. In
contrast, the remaining species, NO2, NO3, and SO^ , exhibit more relative
variability at the low concentrations than at the high concentration.
Concentrations were identified below which the relative variability showed
appreciable, increases. These liquid concentrations, referred to as critical
concentrations, are 0.20 Mg NO^/mL, 0.15 ug NO^/m!,, and 0.10 i
-------
Ammonia Cone ami nat: ion
During the coarse of the study, prompt, analysis of samples permit ted
timely examination of results. Although the field blanks showed no evidence of
NH3 contamination, examination of actual field data revealed variable, and
sometimes suspiciously high, NII3 concentrations. Subsequent tests during the
field study suggested contamination from a source within the sampling box.
Later tests confirmed that the interior foam insulation does release ammonia.
This resulted in the invalidation of most of the ammonia data.
Quality Assurance Filters
Independently prepared quality assurance (QA) filters were extracted and
analyzed Lo assess the precision and accuracy associated with nitrate and
sulfate recovery from Teflon and nylon filters. Known amounts of KNO3 and
K2SO4 from gravimetrically prepared stock solutions were deposited on 47 mm
diameter, 1 pm pore size Teflon and nylon membrane filters. For both the
Teflon and the nylon filters, each of three 3-filter sets was loaded at a
different analyte level. A loading precision of 0.3 percent is claimed.
Prompt extraction and analysis of these QA samples permitted early
detection of an apparent species instability at low loading levels on nylon
filters. As a result, the study was repeated with a second allocation of 18
spiked filters. The CV1s for analyses of three identically loaded filters show
good precision (5 percent or less) for both nitrate and sulfate on Teflon
filters at each of the three loading levels. This good precision is seen only
at the medium and high loading levels for nylon filters, with considerable
variability at the lowest loading level. Quantitative recoveries at each of
the three loading levels were found for both nitrate and sulfate from Teflon
filters. Low recoveries for nitrate and sulfate were found on nylon filters.
This bias is largest (50 to 60 percent) at the low loading and decreases (to
2 to 18 percent) at the high loading. These results indicate that no bias is
associated with Teflon filter extraction and analysis for nitrates and
sulfates. An appreciable bias is indicated for the extraction and analysis of
nitrates and sulfates from nylon filters. The implications of these findings
are: increased confidence in the accuracy of the particulate nitrate 4nd
sulfate data from Teflon filter extracts; and expectation that since volatile
nitrate data (based on nylon filter results) are subject to a low bias, they
represent a lower bound estimate of the Lrue values.
Equivalent Atmospheric Levels
• • 1 • «
Using the critical NO2, NO3 and SO5" concentrations, extraction volumes,
and the extremes of sampled air volumes, estimates of equivalent atmospheric
levels (EAL's) for good analytical precision were made. These result3, shown
in Table I, suggest that in the current study, the relative variability associ-
ated with analytical precision should be negligible at EAL's above approximate-
ly 0.5 |:g/m^. The fraction of data above this level is also .shown for each
species. These results suggest that moat of the HNO2, Htv03, SO2, and Sojj- par-
ticulate data are relatively free from analytical imprecision. It is likely,
however, that much of the NO3 particulate data are not of such quality.
Interlaboratory Comparisons
Authentic field samples were selected and analyzed by the regular analyti-
cal laboratory and then reanalyzed by two other laboratories to provide bases
for interlaboratory evaluation of the quality of the analytical results. Dur-
ing the first: week of September 1985, before the start of the current study,
the ADS was u9ed on the RTI campus to sample ambient air. The resulting sam-
ples were analyzed in the RTI laboratory, and three sets were taken to Los
Angeles for reanalysis by the laboratory that would be performing the routine
526
-------
analyses. The results of these analyses are given in Table II under the head-
ing, "RTI/Regular Laboratory." For each data pair, a mean, standard deviation,
and coefficient of variation were computed. The tabulated results summarize
these findings by providing the mean of the individual CV's (CV), the number of
pairs of data considered, and a qualitative indication of whether the second
measurement exceeded the first. Comparisons were made only for those cases
where both paired data points were nonzero; in a few cases, subjectively
identified outliers were omitted from consideration. Usually, the outliers
were at low concentrations, below those identified earlier as critical
concent rat ions.
The results for the RTT/Regtil.ar Laboratory comparison show good interlab-
oratory agreement. Except for So£~, results of the second analysis were gener-
ally smaller than the first.
At the conclusion of the field study, after initial analysis by the regu-
lar analytical laboratory, six sets of field samples were selected and returned
to RTI for reanaly9is. The results are presented in TabLe II under the heading
"Regular Laboratory/RTI," using the previously described analytical format. In
tli is case, the interlaboratory agreement is good. The second measurement
exceeded the first for NllJ and SO^~, but not for NO2 and NO3.
Three sets of samples were selected and sent to Rome, Italy for reanalysis
in the CNR laboratory. These results are presented in Table 11 under the head-
ing, "Regular Laboratory/CNR." The interlaboratory agreement in this case is
also good for NO2, NO3, and S0^~, and the second measurement for each species
exceeded the first.
Since the duration between the first and second analysis for the interlab-
oratory comparisons was at least a week, an aging study was conducted with
analyses performed by the regular laboratory. In this study, three sets of sam-
ples were selected from those collected on the second day of the field study.
After their initial analysis, they were stored under refrigeration and reana-
lyzed 8 days later with the last batch of field samples. Results of this study
are presented under the heading, "Aging," in Table II. The. comparison in this
case has CV's ranging from 1 to 7 percent. The second measurement exceeds the
first for So£~ and NH^ but not for ND^ and NO3.
Overall, the interlaboratory comparisons show good agreement for each spe-
cies. The results generally agree to within 20 percent or less. The species
concentrations show evidence of aging influences, as indicated by the compari-
son of the mean magnitudes of the first and second analyses. I11 each of four
cases, the sulfate concentration increased with time, while ammonium increased
in two of three cases. Both nitrite and nitrate levels decreased in three of
four cases.
Collocated Samples
On selected days during the study, collocated sampling was performed.
Two types of sampling strategies were followed. The first strategy involved
operating two identical samplers side by side over the same 4- or 6-hour
sampling period. There were 17 cases using this approach. Results of this
study are summarized in Table III for each of the test species. A coefficient
of variation wa9 computed for each data pair. The tabulated results give the
number of cases where both paired data points were nonzero (n) arid the mean of
the individual CV's (CV).
527
-------
In general, the collocated samples were in good agreement with CV's of 20
percent or leas. The best comparisons were found for SOjj" and SO2, where
agreement was better than 10 percent. Nitrous acid, NH3, Nlljj (particulate),
and HNO3 exhibit comparisons showing agreement of 10 to 20 percent. Agree-
ment was poorest for NO3 (total), NO3 (particulate), and NO3 (volatile): 20 to
25 percent. Subjective inspection of the data also revealed apparent outliers.
After elimination of apparent outliers, the comparisons improved and showed
agreement of 15 percent or better.
Inspection of collocated results gives an indication of the precision
associated with sampling and analysis using the ADS. based 011 previously dis-
cussed results, the precision of analysis only should be 1 to 2 percent, except
for the particulate and volatile NO3, where the analysis precision should not
exceed 9 percent. Examination of the CV's for the side-by-side collocated
samples, in light of the analytical precision estimates, suggests that most of
the variability of ADS results is associated with sampling operations rather
than chemical analysis.
Since 100 percent of the collocated results tor Sf^and SO/j- are at concen-
trations above EAL's, the analytical precision should be better than 1 percent.
After eliminating apparent outliers from consideration among eide-by-side col-
located samples, the sampling and analytical precision for SO2 and S()£~ is 6.7
and 6.1 percent. The resulting relative variability associated with ADS sam-
pling of SO2 and SOJj should be Blightly less but still between 6 and 7 per-
cent. If Sf>2 and SO^j" may be considered stable, representative gas and partic-
ulate species that are not subject to interferences, then the sampling varia-
bility for these species may be indicative of the best sampling precision to be
expected for the ADS when operated for A- to 6-haur sampling periods. As a
result, a best case relative variability of 6 to 7 percent may be associated
with sampling operations for gases and particules using the ADS in its current
configuration.
The second collocated sampling strategy involved using one sampler to col-
lect a long duration (10- or 12-hour) sample and using additional samplers to
collect short duration (4- and/or 6-hour) samples simultaneously with the long
duration sampler. The 10-hour sample was a nighttime sample (2000 to 0600),
while the 12-hour sample was a daytime sample (0800 to 2000). Volume-weighted
average concentrations were computed using the individual short duration sam-
ples to compare with the long duration samples, and CV's were computed for each
data pair. Ratios of weighted average to long duration results were also
determined for each data pair. These results are presented in Table 111 as
means of the individual CV's (CV) ami as mean ratios (Ratio). Those mean
ratios are tabulated for all the pairad results.
The volume-weighted average concentrations from the short duration samples
are in good agreement with the concentrations from the longer duration samples.
The tabulated CV's show agreement of better than 10 percent for Nil3, SO^~, SO2,
and HNO2; better than 20 percent for UNO), NIl^, and NO3 (total); and above 20
percent for volatile and particulate NO3. The CV's from the volume-weighted
comparisons are also in good agreement with those for the side-by-side sam-
ples .
Except for particulate and volatile NO3, the weighted averages agree well,
with the long duration samples having ovuralL mean ratios of 0.92 to 1.19.
This suggests that collection efficiencies for most species are comparable for
4- to 6-hour and 10- to 12-hour samples.
528
-------
Result 9
The ambient concentrations of gaseous HNO3, HNO2, and S0'2, and fine parti-
cle NO3, NH£, and SO?" near Los Angeles were determined using the ADS. The
range, mean, and median concentrations for each species over the duration of the
study are shown below.
Mean and Concentration Range (jig/m^) of Species Determined
in Ambient Air Near Los Angeles Using the ADS
fiaa Mean Median Range Particle Mean Median Range
UNO 3
4.8
2.0
0.2
10
32
NO3
3.3
1.9
0.0
Co
19
UNO 2
3.4
2.8
1.0
to
9
nh£
1.0
0.7
0.3
to
5
so2
3.2
3.1
0.6
to
10
soj£-
2.4
2.0
0.8
t 0
7
Concentration trend profiles for each species were prepared from the results of
short duration samples. A representative profile is shown in Figure 2; this
trend profile is for nitric acid. In this diagram, points representing the 4~ to
6-hour average concentrations were connected to permit the trend to be distin-
guished easily. The diurnal behavior showing daytime accumulation and nighttime
depletion is connistent with the concept of UNO3 being generated photocheniical-
ly during the day with nocturnal surface deposition.
Conclusions
The performance of the ADS for the determination of HNO7, HNO-j, Nil 3, Stl^,
and fine particle NO^j, S0^~, nnd NII^, hasi been evaluated using the results of a
field study conducted near L06 Angeles. Most of the variability of AOS results
is associated with sampling rather than analytical operations. The best-case
relative variability associated with gas and particle sampling using the ADS for
ii- to 6-hour sampling periods is between 6 and 7 percent. For the species under
consideration, except for fine particle nitrates, the collection efficiencies are
comparable for 4- to 6-hour and 10- to 12-hour samples. Statistics summarizing
the. ambient concentrations of each species are given, and an 8-day concentration
profile for HNO3 is presented, which illustrates a pattern typical of species
in the atmosphere having a photochemical source and a surface deposition sink.
References
1. M. Possanzini, A. Febo, and A. Liberti, Atmo. Env., 17: 2605-2610, (1983).
2. F. De Santis, A. Febo, C. Perrtno, M. Possanzini, and A. l.iberti, Proceedings
of the Workshop, "Advancements in Air Pollution Monitoring equipment and
Procedures," Freiburg (FRG) 2-6 June 1985.
3. 1. Allegrini, F. De Santis, V. DiPalo, 0. Perrino, and A. Liberti,
Proceedings of the Wjrkshop, "Advancements in Air Pollution Monitoring
Equipment and Procedures," Freiburg (FRC) 2-6 June 1985.
4. E. L. Kolhny, "Tentative Method of Analysis for Ammonia in the Atmosphere
(Indophcnol. Method)," Health Lab. Sci., 10(2): 115-118 (1973).
5. B. K. Saltzinan, "Colorimetrie Mic rodet ermi 11at ion of Nitrogen Dioxide in the
Atmosphere," Anal. Chein., 26: 1949-1955 (1954).
6. R. K. Stevens, R. J. Paiir, I. Allegrini, F. De Santis, A. Febo, C. Perrino,
M. Possanzini, K. W. Cox, E. E. Rstes, A. R. Turner, and J. E. Sickles, IL,
Proceedings of the "Fifth Annual National Symposium on Recent Advances in the
Measurement of Air Pollution," Raleigh, NC, 14-16 May 1985.
529
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TABI.fi I, ESTIMATES OF THE EQUIVALENT ATMOSPHERIC LEVELS (EAL's)
CORRESPONDING TO GOOD ANALYTICAL PRECISION
1st and 2nd I>enuder
Teflon Filter
"pec i es
•102
"°3
soj"
N'
'3
„„2-
v'4
;3
EAL3 >3 ( ug/tr.3 )a
0.61
0.46
0. 30
0,
.68
0.
.53
0.
,80
EALjq (ug/ni3)
0.21
0.15
0. 10
0.
.22
0.
,17
0.
,26
Fraction >0.5 (pg/m^)^
1.00
0.77
O
o
0.
,53
1.
.00
0,
,63
aEAl. - equivalent atmospheric concentration, computed using the critical
concentrations for good analytical precision, the extraction volumes, and the
extremes of sampled air volumes, 3.3 and 10 m^.
''Fraction of the atmospheric concentration data exceeding 0.5
TABLE II. INTERLABORATORY COMPARISONS
Comparison
Nil
NOn
NO,
SOf
RTI/Regutar laboratory
CV, %
2nd > 1st?
22. 7
6
no
15.4
f>
no
19.8
5(2)a
no
4.2
7(2)
yes
Regular Laboratory/RTI
CV, %
n
2nd > 1st?
4.3
9(1)
yes
16.8
7(2)
no
5.0
16(6)
110
3.5
11(2)
yes
Regular Laboratory/CNR
CV. %
2nd > 1st?
21 .8
6
yes
8.3
11
yes
5.5
6
yes
Aging
CV, 7.
n
2nd > 1st?
4.0
7
yes
2.8
8
5.0
8(3)
no
6.7
6(2)
yes
Parentheses contain the number of outliers not considered in the compiled
statistics.
530
-------
TABLE III. COMPARISON OF COLLOCATED SAMPLING RESULTS
HN02 HNO3 S02 NH3 So£~* RO3* NO3** NO3
Side-by-Side Samples
Pairs of Nonzero Data
n 13 17 17 5 17 14 12 17 17
CV 12.6 17.0 9.2 15.1 6.9 24.2 24.9 20.9 15.4
Weighted Average Versus
Long Duration Samples
n 566277677
CV 8.8 15.1 8.7 1.6 6.1 32.4 28.6 19.9 15.9
Ratio 1.09 1.19 1.00 1.00 0.93 1.41 1.50 1.19 0.92
*Particulate
**Volat ile
***Total
-------
AIR
SAMPLER
LINE 2
LINE 1
M A N I FOLD
Nylon Filter
Teflon Filter
Citric
A aid
threaded
rings
n»2co3
TEFLON
CYCLONE
AIR
Figure 1. Annular denuder system.
532
-------
34.OO
30.00
22.00
20.00
1 O.OO
1 4 .OO
1 2 -OO
10.00 -
.OO
rrrnrti 1 ri inTti 1
1 92
O.OO
11
24
O
96
1 44
Hour;; Frcvm Stnrt Of Thn Study
+ collocotad data
Figure 2. Nitric acid concentration profile near Los Angeles from
0000 PDT September 11 through 0600 PDT September 19, 1985.
-------
A SIMPLIFIED TEM ANALYSIS METHOD
FOR ASBESTOS ABATEMENT PROJECTS
George Yamate,
TIT Research Institute, Chicago, Illinois;
Sandra S. Yamate, Lord Bissell & Brook., Chicago,
Illinois; Michael E. Beard, U.S. Environmental
Protection Agency, Research Triangle Park.,
North Carolina
Recently the Office of Toxic Substances, U.S. Environmental Protection
Agency, revised the document "Guidance for Controlling Friable Asbestos-
Containing Materials in Buildings" with the 1985 edition entitled,
"Guidance for Controlling AsbestoB-Containing Materials in Buildings"
(EPA 560/5-85-024, June 1985).
Air monitoring has a well-defined role in determining when an abatement
project is completed. The transmission electron microscopy (TEM) method,
although technically superior, has cost, turnaround time, and instrument
availability a6 disadvantages when compared to the Phase Contrast Micros-
copy (PCM) method with its inherent limitations.
This paper condenses the TEM method that was developed to cover a broad
spectrum of asbestos analysis problem situations. That method has been
streamlined within the abatement requirements of the 1985 edition. Data
necessary for clearance standards are collected, while extraneous informa-
tion is not.
The applications of the simplified method plus changes such as filter size,
carbon coating, counting criteria, and scheduling are presented. Data and
results obtained are al9o shown. Although the method still will not com-
pare in time and cost with the PCM method, the gap has been reduced and
thus provides a better option for prospective abatement work.
534
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A SIMPLIFIED TEM ANALYSIS METHOD
FOR ASBESTOS ABATKMKNT PKO.IKCTS
Introduction
Asbestos is a generic term applied to several commercially useful
fibrous silicate minerals and categorized aa chrysotlle asbestos and amphi-
bole asbestos. The unique properties of asbestos, such as heat resistance,
strength, chemical resistance, and morphology led to its extensive use in
the construction Industry. Sprayed-on troweled-on asbestos-containing
materials were commonly used in fireproofing and insulation of the struc-
tural components of a building. Asbestos was also incorporated in pipe and
boiler room Insulation, floor tiles, and decorative wall coverings.
The potential for Injury by respiratory exposure to asbestos fibers
has been well documented. Asbestosis, lung cancer, and mesothelioma (an
Incurable cancer of the pleura) have been attributed Lo asbestos inhalation
and the numbers of these cases have been Increasing yearly. The latency
period for these asbestos-related diseases has been projected at 20 to
40 years, which makes It difficult to assess dose-response relationships,
threshold values, or size/shape effects.
Since the U.S. Environmental Protection Agency (EPA) banned the use of
asbestos-containing material (ACM) In these construction activities, the
problem remained as to what to do with the ACM already in place. The EPA
established a Technical Assistance Program (TAP) to provide technical
expertise on how to identify and control ACM. The presence of asbestos in
schools, public-access buildings, and commercial buildings required iden-
tification (location) and Its condition (risk). Guidance documents were
prepared and distributed in 1979—Orange Book,' in 1983—Blue Book," and
1985—Purple Book, which incorporated state-of-the-art results from
numerous EPA sponsored studies.
A high risk situation contains deteriorating asbestos designated fria-
ble (when dry, could be easily crumbled, pulverized, or reduced to powder
by hand pressure) in a location where many Individuals would congregate for
extended periods of time. Since children have the greatest potential for
long term exposure, schools were the first choice objective In asbestos
abatement. Building tenants and occupants were also In the. risk group.
In asbestos abatement, the owner or manager has already surveyed his
building and is aware of the presence, condition, and relative quantity of
ACM. The building owners or managers, in considering the health and
welfare of their occupants, are also aware of possible legal consequences
and public reaction. At present there are four options for the responsible
owner/manager. These are:
1. remove the ACM
2. encapsulate the ACM
3. enclose the ACM
4. establish a sound operation and maintenance plan.
The guidance documents provide to the owner/manager a course of action for
controlling the ACM.
535
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Asbestos abatement is a growing industry, with a concurrent Increase
in rules and regulations at the Federal and State levels. The Occupational
Safety and Health Administration (0HI1A) maintains responsibility for activ-
ities inside the enclosed abatement workplace. The EPA responsibility
resides outside of the enclosure, checking for asbestos leakage and most
important, whether the clean-up of asbestos in the enclosed air space is
adequate for removal of the enclosure barriers without release of addi-
tional asbestos to the environment. State agencies responsible for
asbestos abatement usually incorporate Federal rules, regulations, and
guidelines into their regulatory procedures, thus enlarging the area of
enforcement.
The EPA presented its latest findings in the 1985 document entitled,
"Guidance for Controlling Asbestos-Containing Materials in Buildings," the
so-called Purple Book. In this document, release of the abatement con-
tractor is based on visual inspection and air testing to determine that the
source of asbestos fiber release has been controlled and the asbestos gen-
erated during the abatement activity is below a designated level of accep-
tance .
Three microscopic methods are used in airborne asbestos analysis.
These are phase contrast microscopy (PCM), scanning electron microscopy
(SKM), and transmission electron microscopy (TEM).
The TEM method is the state of the art in identifying and quantifying
the asbestos concentration levels in ambient air. It gives the most com-
plete information on airborne asbestos since it can detect the extremely
small and thin fibers as well as distinguish asbestos from other fibers.
However, it has the reputation of being expensive ($200 to $600 per sample)
and time-consuming (two- to seven-day turnaround), and the instrumentation
is not widely available.
This presentation is made to show that in air testing for asbestos
abatement projects, the recommended, comprehensive TEM analysis method
developed under contract to EPA can be simplified. Using the guidelines of
the Purple Book and without any sacrifice of quality, the method will
result In a less costly and time-consuming analysis. The increased use of
TEM analysis should result in a corresponding increase in the number of
TEMs.
Method Development
Background
The EPA sponsored an in-depth study of various electron microscopy
procedures that resulted in the provisional methodology manual, "Electron
Microscope Measurement of Airborne Asbestos Concentrations." Limitations
in the provisional method resulted in a follow-up study and the development
of a refined transmission electron microscope method for the determination
of asbestos in the ambient environment. The refined method, "Methodology
for the Measurement of Airborne Asbestos by Electron Microscopy," incor-
porates the basic concept of the provisional methodology as one of its pro-
tocols. However, both methods are referenced In the Purple Hook for air
testing for abatement clearance.
The refined methodology is divided into three levels of data acquisi-
tion. Level I is a relatively rapid procedure and provides Information on
536
-------
fiber number, size distribution, visual selected area electron diffraction
(SAED) pattern, and a calculated mass concentration. Level II adds elemen-
tary chemical analysis for individual fibrous structures, and Level III
confirms asbestos identification by quantitative electron diffraction pat-
tern analysis.
To meet the objectives of the method's development, emphasis was
placed on eliminating non-essential parts of the Level 1 analysis, incorpo-
rating time-saving features of data acquisition and reduction, and changing
to a smaller filter size In the air sampling equipment.
Non-Essential Features
The first feature eliminated was the size measurement of the indi-
vidual fibrous structures. Measurement required positioning of the struc-
ture relative to concentric circles of known radius, taking length and
width estimates, and finally repositioning back to its original location in
order to continue traversing across the grid opening. The writing of
lengths and widths onto the data sheet also added to the time factor. Once
voice-activated input to a computer is perfected, tills feature may be added
back to the method.
The second feature to be eliminated was the transfer of data into the
computer for a computerized printout of the results. The computer gener-
ates calculated mass of individual fibers, aspect ratios, average dimen-
sions, etc. However, according to the Purple Book, only the number of
fibers per cc is of importance, and it Is used to compare Inside and
outside levels of the enclosed abatement area. Therefore, the data sheet
can be simplified without concern for computer input requirements.
The third feature to be eliminated was the cumulative fibrous struc-
ture classification, since in asbestos abatement clearance testing the
concentration levels inside the enclosure are monitored during the workday
with phase contrast microscopy. Asbestos levels are minimal when clean-up
is completed.
Time-Saving Features
The data sheet for the electron mlcroscoplst has been redesigned. All
pertinent information that was included in the Level I data sheet, computer
printout, and report form were incorporated Into the abatement data sheet
that would be filled in and calculated by hand. The results themselves
would then be reported directly to the requestor ot the analysis (asbestos
project manager); the data sheet would be kept on file.
Change to 25 mm Filter Size
The TEM methods have in the past recommended the 47 mm and 37 mm
filter sizes. A change to the 25 inm size results In several time and cost
savings.
1. A smaller sampling volume would be required for the same detection
limit, or a lower detection limit would be attained for the same
sampling volume, as shown in Table I.
2. With the use of a smaller size filter, more filters can be carbon-
coated at one time.
537
-------
3. The coat of 25 mm filters Is less than half that of the 37 mn
size. The possibility of a box of filters being contaminated
exists, and replacement costs would not be as great. The other
filter cassette components would be correspondingly lower in
cost. Although field samples and field blanks would be supplied
by the asbestos project manager, each laboratory has to prepare
its own laboratory blanks.
Results (Simplified Method)
This simplified TEM asbestos analysis method is specifically designed
for air testing in an asbestos abatement project and includes the following
steps:
1. The 25 mm, 0.4 gra polycarbonate filters in a box are spot checked
for asbestos contamination prior to use of the remainder.
2. The three-piece filter cassettes are loaded on a clean bench. A
support pad is placed into the cassette base, then a 5.0 urn pore
size cellulose ester backing filter is placed on the support pad.
Finally, a clean 0.4 [im polycarbonate filter with the shiny side
up is placed on the backing filter. The cassette assembly is
pressed tightly together to hold the filters in place and prevent
leaks from the sides of the cassette. An added precaution is to
use a plastic tape to seal the sides. The assembly is then placed
in a plastic bag to keep ft dust-free until needed.
3. A known volume of air is passed through the polycarbonate filter
to obtain approximately 5 to 10 pg of particulates per cm2 of
filter surface. Knowledge of the particulate loading of the
source of make-up air into the abatement enclosure will aid in the
selection of the sampling volume.
4. Periodic flow rate checks are made with a calibrated flow meter.
5. Upon completion of sampling, the cassette is removed while up-
right, placed carefully into a plastic bag, and placed in the
carry case and hand-carried back to the laboratory.
6. The filter is carboii-eoated while still in the cassette by
removing only the top lid.
7. The particulates are transferred to an electron microscope (EM)
grid using a refined Jaffe Wick Washer.
8. The EM grid is examined under low magnification (250X and 1000X),
followed by high magnification search and analysis (20,000X or
approximately 16,000X on the fluorescent screen).
9. A known area (measured grid opening) is scanned and the fibrous
structures (fibers, bundles, clusters, and matrices) are iden-
tified as to asbestos, ambiguous, or non-asbestos; length measured
for categorization; and counted. No distinction is made between
chrysotile and amphtbole asbestos.
10. The observations are recorded for 10 grid openings on the data
sheet. For better statistics, another 10 grid openings in a
second grid from the same filter may be examined. Figure 1 is an
example of a completed data sheet.
Since rates per hour vary between personnel, a standard of comparison
may be the analytical time necessary to complete a filter analysis. Previ-
ously, a Level I analysis took 3 to 4 hr per sample. With the new method
it takes 2 to 2-1/2 hr to complete an analysis.
538
-------
Thus, for an abatement clearance test, if samples arrive by 3:00 P.M.,
carbon coating and grid transfer is started before 5:00 P.M. The next
morning by 9:00 A.M., samples could be examined in the electron microscope.
Results could be telephoned out to the Job site 40 hr after receipt of the
samples.
Conclusions
A simplified TEM analysis method for asbestos abatement projects is
described. The important data necessary for proper evaluation of the air-
borne levels of asbestos in the abatement enclosure are obtained while
eliminating extraneous Information. An actual time period of 2 to 2-1/2 hr
per sample is estimated for performing the analysis. However, because of
grid transfer time, a total of 40 hr is necessary to approve or disapprove
contractor clearance.
References
1. "Asbestos-Containing Materials in School Buildings: A Guidance
Document," Parts L and 2, U.S. Environmental. Protection Agency,
Washington, D.C., 1979.
2. "Guidance for Controlling Friable Asbestos-Containing Materials in
Buildings," U.S. Environmental Protection Agency, Washington, D.C.,
1983.
3. "Guidance for Controlling Asbestos-Containing Materials in Buildings,"
U.S. Environmental Protection Agency, Washington, D.C., 1985.
4. A. Samudra, C. F. Harwood, J. D. Stockham, "Electron Microscope
Measurement of Airborne Asbestos Concentrations: A Provisional
Methodology Manual," Office of Research and Development, U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina
(revised 1978).
5. G, Yamate, S. C. Agarwal, R. D. Gibbons, "Methodology for the
Measurement of Airborne Asbestos by Electron Microscopy" (Draft Report,
Contract No. 68-02-3266), Office of Research and Development, U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina
(1984).
539
-------
TABLE I. DETECTION LIMITS
1.0
Filter Size
25 nm
37 nan
2.0
Effective Filtration Area
3.8 cm2
8.55 era2
3.0
Average Area of Grid Opening
(75 pm per aide)
.00005625
cm 2
.00005625
cm^
4.0
Number of Grid Openings
10
10
5.0
Sampling Volume—Detection
Limit
3000—2.25
liter
fibers/
3000—5.07
liter
fibers/
6.0
Sampling Volume—Detection
Limit
2000—3.38
liter
fJ bers/
2000—7 .6
liter
fibers/
7.0
Sampling Volume—Detection
Lirni t
1332—5.07
liter
f i bers/
—
540
-------
TEM ASBESTOS ABATEMENT ANALYSIS REPORT
Sample 1.1). C701-275 Date Analyzed I/16/86 Grid Box Misc. #23
I1TRI I.D. CD8820-C70I Accl. Voltage 100 kV Grid Location B2 + B3
Date Sample Received 1/15/86 Beam Current 100 uA Volume Sampled 2520 liters
Filter Type 25 mm Nuclepore EM Magnification 20,00QX Method of Sampling Aggressi ve
Filtration Area (cm2) 3.8 Fluor. Screen Magnif. 1 u » 16 mm
Description of Location Northeast corner of enclosure Results 0.017 asbestos structures per cc
C'nrvsotile
and Amphibole Asbestos
Grid
Fibers
Bundles
Non-
Opening
< 1 U
1 to 5 p
> 5 u
< 5
> 5 u
Clusters
Matrix
Ambiguous
Asbes tos
1
0 / 0
n
L.
/ 0
1 1
3
/ 0
1
1
4
0/0
5
/ 15
1 1
fi
0 / 16
1
1
1
1
1
/
/ 0
1
8
/ o
1 1
1
|
9
/ 19
1
1
1
| 1
10
/ o
|
1
TOTALS
3
8
0
1
1
0
1
2
3
Per
Filter Area
9186
24,496
BDL*
3062
3062
BDL*
3062
6124
9186
No.
per Liter
3.65
9.72
—
1.22
1.22
1.22
2.43
3.65
No.
per cc
.004
.01
—
.001
.001
-
.001
.002
.004
*BD1
= Below detection level
Detection Li ait;
1215 asbestos structures per m3
Area of G.O.—Start 63 x 63 0 1000X - 64 x 64 Area of G.O.—End 63 x 63 @ IQOOX - 61 x 62
20 (No. of G.O.s Examined) x .00006205 (Avg Area of G.O., cm2 ) = .001241 (Total Area Examined, cm? )
EM Description of Sample Medium loading; opaque spheres and combustion aerosol
Figure 1. An example of a completed data sheet.
-------
A NEAR REAL-TIME INSTRUMENT FOR
MONITORING TOTAL, COHBUSTIBLE,
AND ASH PARTICULATE FROM INCINERATORS
Richard E. Gibbs
James D. Hyde
Bureau of Air Research
New York State Department of
Environmental Conservation
Albany, New York 12233
Harvey Patashnick
Georg Rupprecht
Rupprecht and Patashnick Company
P.O. Box 330
Voorheesville, New York 12186
The basic concept of the tapered element oscillating microbalance
instrumentation as it has been previously applied to realtime particulate
measurements is described, A new instrumental form is then described
which subjects samples of collected particulate to a high-temperature
oxidation step that yields total, oxidizable, and ash residue mass data
for a 15-minute instrument cycle time. This unit is fully automatic and
has been demonstrated for near-realtime characterization of the carbon
content of fl.yash from a coal-burning power plant. Applications of this
measurement technique for combustion control research and emission
monitoring characterization at waste incinerators are discussed.
542
-------
A NEAR REAL-TIME INSTRUMENT FOR MONITORING TOTAL, COMBUSTIBLE,
AND ASH PARTICULATE FROM INCINERATORS
Introduction
Background
Particulate mass is a common surrogate parameter for detailed
emission species for a wide variety of regulatory, research, and
combustion control purposes. Particulate weight as obtained by
conventional filter techniques necessarily yields a single average datum
per filter, this after a post-experiment gravimetric analysis. The
measurement needs of emission characterization research, combustion
process control, and continuous emissions monitoring (CEM), are not always
well-served by this historic particulate sampling approach, even though it
occupies a central position for regulatory compliance determination. Over
the years various techniques have been proposed to bring particulate
measurement into the "on-line" category of process measurement. These
usually suffer from the problem that some additional surrogate property,
such as opacity, is introduced in plane of mass, with the correlation to
mass then depending on non-mass related particulate properties. This
dilemma represents an acute problem if the realtime measurement is to
serve the dual purposes of characterization and compliance testing.
This paper is not a general survey of realtime instrumentation
concepts or their current status; it is rather an introduction to one
emerging technique for realtime measurement of collected mass on a filter
substrate. Here, a mass sensitive instrument is brought to the particle
sampling point and a large number of realtime mass determinations are
provided while particulate collects on a single filter. The mass
measurement is accomplished by a proprietary concept wherein the
particulate collection filter sits atop a hollow tapered tube which
oscillates in a lateral plane while sample flow passes through the filter
and out through the center of this tapered element. The frequency of
oscillation for the tapered element is analogous to a common tuning fork,
in that the frequency is uniquely related to the oscillating mass. This
patented tapered element oscillating microbalance (produced exclusively by
Rupperecht and Fatashnick Company, Inc. under the trade name TEOM®)
technology has been the subject of numerous demonstration projects applied
to a wide range of particulate measurement conditions. These include
ambient air1, underground mine air'', fire research, turbine exhaust,
diesel emissions1,4'^6 , stack testing from stationary combustion
sources7.8, and is also being prepared for particle measurement in space.
From this early phase of prototype TEOM instrumentation one can anticipate
a subsequent phase wherein the TEOM concept will gain a wider acceptance,
where several applications will become instrumentally routine.
Identification of clear measurement goals will thus become significant in
directing these developments, since the question is not "Can one measure
particulate mass in realtime," but rather "To what end will the
demonstrated capability be applied?"
This paper describes a prototype TEOM instrument constructed for the
goal of monitoring not only total particulate mass, but also the mass
fraction removed by heating to = 800°C in air. Through repeated
programmed time-cycle instrument steps of collection, oxidation, and ash
543
-------
removal, this instrument operated on a near-realtime basis. This TEOM
instrument thus provides near-realtime data indicating total,
"combustible", and ash residue data from an experimental test in a coal-
burning power-plant.
The array of regulatory, research, and combustion control needs
facing the expected large scale introduction of waste incinerators makes
this TEOM concept a logical candidate for some of these purposes.
Potential uses for the data generated by the TEOM would include: more
efficient operation of the combustion and flue gas cleanup equipment, a
refined correlation parameter for chemical species studies, and a useful
CEM parameter to insure regulatory compliance and public acceptance.
However, since the near-realtime partitioning of total particulate mass
into combustible and ash residue fractions remains to be applied to a com-
bustion source burning the variety of fuel/feed components typical of
waste incineration, these applications are deserving of demonstration
research study.
TEOM Concept
A schematic of the TEOM concept for particle mass measurement is
shown in Figure 1. Particle laden gas passes through the filter and down
through the hollow tapered element t:o inass flow control components, not
shown. Mass measurement during this sampling process is achieved by
detection of a change in oscillation frequency of the tapered
element/filter/particulate composite. The following steps described how
these oscillations are established and detected; referenced to Figure 1.
1) A constant DC electric field is set up between the field
plates.
2) An image of the tapered element is projected on a
phototransistor by the illumination provided by a light
emitting diode (LED).
3) The mechanical oscillation of the tapered element produces an
AC voltage at the phototransistor.
!*) This AC voltage is amplified and fed back through a conductive
path on the tapered element. This voltage then Interacts with
the DC electric field and maintains the oscillation of the
element at its resonant frequency.
5) The frequency of oscillation is determined by a counter/timer
interfaced to an electronic control and data processing module.
When an increment of particulate mass, <5m, has accumulated on the
oscillating filter, the frequency of oscillation changes (decreases)
according to:
6m = K (f~2 - f"2) (1)
o 1 o
where 6m = deposited mass on filter
K = calibration constant
o
f = frequency before addition of mass, 5m
fj =* frequency after mass addition, <5m
544
-------
SIDE VIEW
TOP VIEW
FLOW
M/
FILTER
i=P^OSC!LLATlON
LED
OSCILI. ATiON
-O-
o-
• FIELD PLATES
O-
—PHOTO TRANSISTOR
TAPERED ELEMENT
¦H- CONDUCTIVE PATH——A
ON TAPERED ^
ELEMENT
TO PUMP
COUN f fc R
DATA
PROCtSSING
Typical Taptred Element Oscillating Microbolance (TEOlU®) Configuration
Figure 1
By proper dimensioning of the Lapered element the sensitivity of the
mass/frequency relationship can be selected according to the measurement
application. TEOM instruments have been built that span the range of
sensitivity from picograms to grams. Previous work by the authors has
explored calibration techniques*' and found the inherent linearity
sufficient to enable single point calibration capable of ±1% accuracy over
a wide range of mass additions. in Equation 1, K represents a constant
based on the physics of an a harmonic oscillator, and in practice the TEOM
unit conforms to this description sufficiently well that K. can be treated
as a constant for incremental mass additions to a clean filter as well as
final mass additions to a dirty filter. Thus, a frequency comparison
between any two times in a long series of data acqusition points provides
an accurate mass differential on the filter corresponding to these times.
A TEOM Instrument for Measuring Carbon in Flyash
Background
A common characteristic of flyash used by plant operators for
combustion evaluation is the Loss-On-lgnition test (LOT) to determine the
carbon (combustible, or oxidizable) content of flyash. This is a
laboratory analysis test providing retrospective data on the plant,
whereas the TEOM instrument to accomplish this particulate
characterization is automatic, and performs the analysis on a 15-minute
time cycle basis with immediate graphic reporting of results.
545
-------
Mode of Operation
This instrument uses a ceramic filter placed on the tapered element,
with three different sequential instrument functions performed on the
ceramic filter. Particulate sample is first collecLed, then heated to
drive off the oxidizahle portion of the collected sample, and finally the
ceramic filter is cleaned to remove the non-oxidizable portion of the
particle sample, A mass determination is recorded between each of these
steps from which results are obtained for total particulate, loss of
combustible particulate, ash residue, and clean-up efficiency. The
sequence of functional steps in a complete instrument cycle is shown in
Figure 2,
Key Instrument Features
The key features that describe this Instrument are briefly outlined
below, although numerous critical details such as flow control, computer
software, graphic display options, and automatic fault diagnosis are
omitted for this conceptual presentation.
PREPARATION
FOR NEXT CYCLE
FIRST
WEIGHING
SAMPLE
COLLECTION
FOURTH
WEIGHING
SECOND
WEIGHING
SAMPLE
REMOVAL
SAMPLE
OXIDATION
TEOf^® CARBON CONCENTRATON MONITOR INSTRUMENT CYCLE
Figure 2
546
-------
Instrument Sub-System Schematic. Figure 3 is a block diagram
showing the various sub-systems and their functional relationships. A
desk top computer controls all sequencing of the instrument operations and
displays results and error messages. The computer, which can be located
remotely from the measurement system, is interfaced with an electronics
module that 1) controls and extracts mass data from the TEOM frequency
signals, 2) controls the moveable stage and heated sample probe to the
stack, and 3) controls the pumping and valving systems to achieve the
various functions previously described. Figure A schematically shows
SAMPLE
PROBE
ELECTRONICS
PUMP H
VAI.VING
SYSTEM
SAMPLING 8
OXIDATION
STAGE
DISPLAY
TEOI#
COMPUTER
CARBON MONITOR SUB-SYSTEMS
Figure 3
these subsystems as they were configured for operation with the
computer/printer situated next to the sampling, sensing, and flow control
elements.
Movable Stage Design. The functions of particulate collection,
heating, and ash residue clean-up were all incorporated into a movabLe
stage assembly as shown schematically in Figure 5. The movable stage
provides precise location in both the lateral and vertical directions
under instrument computer control. The TEOM and ceramic filter assembly
are fixed below this moveable stage.
Operation Cycle. The sequence of instrument operations that
constitute a complete measurement cycle was previously shown in block
diagram form as Figure 2. With the unloaded filter in position for
sampling, a frequency determination is made to start the cycle. Sample
547
-------
3m port to SMOKESTACK
SAMPLE 6 SENSOR UNIT
CRT OiSPLAY
MOVEABLE STAGE
DESKTOP COMPUTER
JE
PUMP B VALVING
UNIT
SCHEMATIC OF SYSTEM COMPONENTS
Figure 4
PNOBE MOVEMENT (VERTICAL)
SAMPLE
NLET TUBE
CLEANING
nozzle;
MOVEABLE STAGE
STAGE MOVEMENT i HORIZONTAL)
•WIRE BRUSH
Ml
PLATE
//////////A
VACUUM DURING CLEANING
TfcOH®
HOUSING
THE MOVEABLE STAGE IN SAMPLING MODE
Figure 5
548
-------
collection then follows for either a prescribed time interval or
particulate mass loading on the filter, after which a second frequency
determination is obtained yielding the total mass collected. The heating
element is then moved into position and the sample temperature is raised
to approximately 800°C for a few minutes. A second frequency measurement
is recorded after cool-down. The computer monitors TEOM frequency and
stability before final mass determinations to insure that filter mass
loadings are not changing when readings are taken.
Sample removal then proceeds with the moveable stage positioned to
direct the air nozzle over the filter. Compressed air is then back
flushed through the tapered element and ceramic filter while vacuum draws
the dislodged residue away from the sensing area. Simultaneously,
compressed air is directed through the nozzle to aid the cleaning process.
Nozzle flow is stopped while the back flush flow continues, and the stage
moves back and forth to cause a wire brush to wipe across the filter to
complete the cleaning process.
The stage then moves back to the sampling position, and the
frequency of the cleaned filter recorded to determine both the efficiency
of particulate removal for the current instrument cycle and the baseline
filter mass for the next cycle. The entire instrument cycle was, for this
application, set to 15 minutes.
Ceramic Filter. A new ceramic filter, shown in Figure 6, was
designed for the TEOM instrument so that a high-temperature oxidation
period would not damage the filter during the LOI tests. The porous
ceramic filter for particulate collection is supported and sealed by solid
ceramic elements, with the ceramic stem of the filter tapered to fit the
oscillating tapered element. This filter was designed to have both low
mass, which increases the mass sensitivity of the final TEOM instrument,'
as well as low thermal mass, which aided in optimizing the cycle time
required for heat-up and cool-down.
The filter is removable from the tapered element, allowing filter
exchange as needed. In this application the filter was not changed but
was automatically cleaned as part of the event cycle, as described below.
Heater Design. Particulate collected on the ceramic filter was
heated by a spiral-wound nichrome ribbon that forms a disc-shaped element,
shown schematically in Figure 7. Height of the heater element above the
ceramic filter is adjustable, and is set to provide rapid heat-up of the
particulate sample when the heater is powered. A thermocouple positioned
on the ceramic filter indicated a steady 800°C temperature after one
minute of heater operation. From previous LOI test characterizations of
flyash this heating level was considered ideal.
Flow Control. Throughout the entire cycle of instrument operation
several flow conditions are demanded, including sample flow through the
TEOM filter, reverse flow through the heated stack sample probe prior to
reestabl ishment. of sample flow, reverse flow through the TEOM ceramic
filter after ash determination to clean the ash from the filter, nozzle
flow directed at the face of the ceramic filter during the clean-up
segment, and also vacuum flow to collect the dislodged ash particles
during this clean-up phase.
549
-------
DETAIL
FILTER SUPPORT
AIR PASSAGES
CERAMIC FILTER
V V V \ V. ^ \ \ V
CERAMIC SEAL'
CERAMIC PLATE
CERAVIC TUBE
CERAMIC FILTER DESIGN
Figure 6
TT
ELECTRICAL
GROUND
ELECTRICAL
POWER
COOLING FINS
VHEATER COIL
CERAMIC FILTER
HEATER ELEMENT OVER FILTER
Figure 7
-------
Results
Laboratory Tests
Flyash samples with carbon content ranging from 2.3% lo 12.2% as
determined by standard I.OI techniques were used to test t.he TEOM
instrument. Each flyash sample was desiccated and then aspirated into the
instrument, which then cycled through the steps as previously described.
The nominal loading of total particulate for these tests was program set
to be 35mg. The average difference between the 1,01 valves and those
obtained by the TEOM instrument was 0.5% by weight. Since no errors of
determination were available for the laboratory 1.01 values, this result is
a comparative and not an absolute value.
Determination of LOT valves at low carbon content is more demanding
than at higher levels since the subtraction of two large numbers (before
and after oxidation) to yield an accurate weight loss of small magnitude
increases the influence of any other sampling or measurement errors. The
flyash sample with 2,3% carbon as determined by the standard 1,01 method
was tested seven times by the TEOM instrument with the a 2.38 ± 0.19
(t'.V. = 8%) result for these runs.
The removal efficiency of particulate frnm the ceramic, filter
between sampling runs averaged 98.7% for these seven runs, Obviously if
the filter slowly loads up with material that is not removed, it will
increase in pressure drop and require a new filter. Both the laboratory
and stack tests with flyash exhibited very high removal efficiencies which
permit fairly long periods of instrument operation. If filter plugging is
a problem encountered in further application testing, the ceramic filters
could be mass produced as a replaceable instrument item.
Stack Tests
The TEOM instrument was used for stack-test evaluation at a
coal-burning power plant. The cycle time was set to 15 minutes. Figure 8
shows the results from 12 hours of operation, with the flyash carbon
concentration displayed in parallel with power output of the plant and
excess oxygen. Changes in flyash character as determined in near-realtime
by the TEOM are evident in concert with plant operation adjustments.
Discussion
A new instrumental method capable of providing near-realtime
particulate, oxidizable fraction, and ash residue has been demonstrated
for application to coal-burning power plants. Kxtension of this prototype
instrument to characterization of particulate emissions for waste
incineration inay require further instrument modifications since the
particulate source is more complex and varied, but these can reasonably be
anticipated to be solvable given the existing work. The ultimate use or
value of such data will not really be evident until some representative
data are first obtained. As compared to combustion monitoring through
standard gas analysis, particulate and particulate break-down data should
provide results more directly related to the species of emission concern.
551
-------
U1
cn
rs»
70-
50-
30
A
(%)
to
o
(MW)
20
15-
10-
0-
¦
C/o)
Excess Oxygen (%)
Power (V W)
CarDon Concenfrotior.
in Flyash (%)
—r~
<4
Tr-
io 12 <4 16 18
HOURS
flyash carbon concentration results from a coal-burning power plant
Figure 8
-------
Given the proto-type nature of the present TEOM instrument, these studies
should at present be viewed as research topics by which to advance both
the applicability of the technique and the understanding of incinerator
emissions. Beyond those goals, the TEOM instrumental technique presented
would appear to have significant long-term potential for CEM use to insure
that incinerator facilities are routinely operated in accordance with
permit specifications.
Acknowledgements
Funding for the TEOM Carbon Concentration Monitor project was
provided by the Empire State Electric Energy Research Corporation and the
New York State Energy and Research Development Authority.
The authors thank Linda Stuart for manuscript preparation and Gary
Lanphear for cartographic contributions.
References
1. Patashnick, H. and Rupprecht, G. , "A New Real Time Aerosol Mass
Monitoring Instrument: The TEOM," Proceedings: Advances in
Particulate Sampling and Measurement, Daytona Beach, FL, 1979,
EPA-600/9-80-004, 1979.
2. Walters, Sam, "Clean-up in the Colliery," Mechanical Engineering,
105, 46, 1983.
3. Whitby, R. et al.f "Real-Time Diesel Particulate Measurement
Using a Tapered Element Oscillating Microbalance," Society of
Automotive Engineers Paper 820463, 1982.
4. Whitby, R. , Johnson, R. , and Gibbs, R. , "Second Generation TEOM
Filters: Diesel Particulate Mass Comparison between TEOM and
Conventional Filtration Methods," Society of Automotive Engineers
Paper 850403, 1985.
5. Shore, P.R. and Cuthbortscn, R.D., "Application of a Tapered
Element Oscillating Microbalance to Continuous Diesel Particulate
Measurement," SAE Paper 850405, 1985.
6. Hales, J.M, and May, M.P., "Transient Cycle Emissions Reductions
at Kicardo - 1988 and Beyond," Society of Automotive Engineers
Paper 860456, 1986.
7. Wang, J.C.F., Patashnick, H., ar.d Rupprecht, G., "New Real Time
Isokinetic Dust Mass Monitoring System," Journal of the Air
Pollution Control Association, 30 (9), 1018, 1980.
8. Wang, J.C.F., Kee, B.F., Linkins, D.W,, and Lynch, R.W.,
"Real-Time Total Mass Analysis of Particulates in the Stack of an
Industrial Power Plant," Journal of the Air Pollution control
Assoc iation, 33 (12), 1172, 1980.
553
-------
AMBIENT ATMOSPHERIC CONCENTRATIONS OF
TOXIC METAL AND TOXIC ORGANIC SPECIES
IN NEW YORK STATE URBAN ENVIRONMENTS
Robert Whitby,
Donald E. Gower, Edward W. Savoie
New York State Department of
Environmental Conservation
Albany, New York
The New York State Department of Environmental Conservation, in
cooperation with the NYS Department of Health's Wadsworth Center for
Laboratories and Research, has initiated I'.lie Toxic Air Monitoring (TAM)
project to monitor air toxics on a routine basis and for determining the
background concentrations in selected urban environments across the state.
Ambient atmospheric measurements for seven toxic metal species (Cd,
Cr, Mn, Ni, Pb, V, and Zn) and four classes of toxic organic species
(phthalates, hexachlorocyclohexanes, polychlortnated biphenyls, and
ber.zo [ a ] pyrene) at. ten siLes in urban areas of New York State indicated
that ambient concentrations were lower than the concentrations currently
used as the New York State acceptable ambient levels (AAL).
Vanadium at Poughkeepsie and lead at Hempstead (Long Island)
exhibited the highest ambient mean concentration to AAL ratios.
Statistical estimates of the upper limit of the annual means for these two
highest data sets were 0.51 AAL and C.38 AAL respectively. The means of
the data sets (21 to 27 samples taken over one year periods) were
typically 0.05 AAL to 0.25 AAL for Pb and V and below 0.05 AAL for the
other metal species monitored. Organic species were not observed at con-
centrations above 0.025 AAL with the excepLioti of benzol a Ipyrene, which
was frequently observed in the 0.015 AAL to 0.15 AAL range.
In addition, the first unambiguous measurement of dioxins and furans
in ambienL air in the U. S. was conducted at two sites in New York State
and resulLs indicate no immediate or acute health concerns. However, the
existing database is very limited and more monitoring data is needed to
form better conclusions.
554
-------
AMBIENT ATMOSPHERIC CONCENTRATIONS OF TOXIC METAL AND TOXIC ORGANIC
SPECIES IN NEW YORK STATE URBAN ENVIRONMENTS
Introduct ion
This work was undertaken as a part of the New York State Department
of Environmental Conservation's Toxic Air Monitoring (TAM) program. The
purpose of the TAM program is to provide, for the first time, long-term
systematic collection and analysis of selected toxic air contaminants at
sites located statewide. Previous studies have been short-term source
oriented and not sufficiently developed arid funded to adequately identify
atmospheric toxics or to detect temporal and spatial variations of
contaminant concentrations. Additionally, the minimum detection level was
not always low enough in previous studies to adequately measure the
background concentrations of toxic contaminants.
The contaminants chosen for this study were selected primarily
because of their interest within the Department and because only minimal
research effort would be required for an expeditious start of the program.
Funding levels also limited the scope of the study.
Measured values were compared to acceptable ambient levels (AAL)*
obtained, except where noted, from "Air Guide-1," a publication of the
New York State Department of Environmental Conservation which serves as a
guideline document for the control of toxic ambient:, air contaminants' .
The AAL values for measured species are presented in Table I.
The Division of Air Resources (Department of Environmental
Conservation) was responsible for the selection and operation of sample
sites and the collection of all ambient samples. All analytical chemistry
to determine concentrations of the selected toxic contaminants in samples
was performed by the Wadsworth Center of the Division ot Laboratories and
Research (Department of Health).
Study Sites
The Toxics Air Monitoring sites were selected to provide measurements
representative of urban, industrialized, residential, and background
areas. Personnel from the Department of Environmental Conservation were
responsible for the selection and establishment of the sampling sites.
Some of the study sites were continuous air monitoring stations (CAMS)
which are part of the Division of Air Resources' air monitoring network.
Other sites were stations that are also in the total suspended particulate
(TSP) monitoring network or in use for special studies. The Lake Placid
site was specifically selected for this study to provide background
measurement data.
The use of existing CAMS and TSP sites maximized the information
available with minimal expense. CAMS personnel were employed to operate
the organic toxics sampling equipment and TSP filter samplers. The TAM
study sites and sampling periods are presented in Table II and described
in detail below. Some sites remain currently active in the TAM program.
"Acceptable Ambient Levels (AALs) in New York State are defined by: NYS
Department of Environmental Conservation, "NYS Air Cuide-l, Guidelines
for the Control of Toxic Ambient Air Contaminant, 1985-86." A calculated
AAL value (such as TLV/300) is used when a contaminant specific AAL
analysis based on health effect criteria is not available.
555
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° The Poughkeepsie site is located in the western portion of the city
next to the Hudson River, in an urban area close to Columbus School. The
site is a continuous monitoring station for SO^, 0.^, and meteorological
parameters, and is operated by Department personnel.
° The Buffalo site is located on the roof of Public School 66 at Parkside
and Tacoma Avenue in the central part of Buffalo. it is primarily a
residential area, downwind of industry located along the Niagara River.
The site is operated by Department personnel.
" The Lake Placid site is located on the roof of the Lake Placid arena,
216 Main Street. The village is situated in the north central portion of
the Adirondack Mountains. The site is operated by Department personnel.
° The Rochester site is on Farmington Road in eastern Rochester. The
site is a continuous monitoring station for S0?) 0^, CO, and
meteorological parameters and is operated by Department personnel.
" The Hempstead site is at Eisenhower Park and Merrick Avenue in eastern
Nassau County. This is a continuous monitoring station for SC^, CO, NO ,
and meteorological parameters operated by County personnel.
° The Niagara Falls site is at 63rd Street and Glrard Avenue, in the
southeastern part of the city. The site is a continuous monitoring
station for SO^, 0^, CO, and meteorological parameters, operated by
Department personnel.
° The Syracuse site is located on the roof of Lakeland Elementary School,
on Bury Drive in the western portion of Syracuse. This TSP site is
operated by State personnel.
° The Rensselaer site is on Riverside Drive at the southeastern part of
the city, on the eastern side of the Hudson River. This is a continuous
monitoring station for 0^ and meteorological parameters operated by
Department personnel.
0 The Greenpoint site is on the roof of the Sewage Treatment Plant at 301
Greenpoint Avenue in northern Brooklyn. This station is located in an
industrial area and continuously monitors for SO2. The station is
operated by Department personnel.
° The Susan Wagner site is located in Staten Island at the Susan Wagner
High School at 50 Brielle Avenue. This is a residential location. The
station also monitors continuously for S0^, 0^, and meteorological
parameters under the operation of Department personnel.
" The Travis site is located on the roof of Public School No. 26 at 4108
Victory Boulevard in Staten island. This is a residential location. This
TSP site is operated by Department personnel.
Procedures and Methods
Toxic Metal Species
Toxic metal species are found in particulate form in ambient air. To
determine the selected metal species concentrations, particulate samples
were collected on glass fiber filter paper. Filter paper manufactured by
Schleicher and Schuell or by Whatman were used during the January to
March 1982 study period. Following this initial period, only Whatman
556
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filters were used. Samples were collected using the standard high volume
air sampling unit (General Metal Works) used throughout the TSP network.
Air samples were collected over 24 hour periods, from midnight to
midnight.
After air sample collection, the filters were first weighed to obtain
TSP data for each site and then subjected to chemical analysis to
determine concentrations of toxic metal species. Portions of the filters
were subjected to a heated nitric acid extraction procedure using 15 ml of
3 molar nitric acid. Distilled, deionized water was added to the acid
solution (after cooling) to bring the volume to 40 ml. The sample solu-
tion was shaken and centrifuged and the supernatant liquid transferred to
plastic vials. The samples were then analyzed by atomic absorption
sectrophotometry. During the 1982 portion of the project., flame atomic
absorption spectrophotometry (FAAS) was the analytical method employed for
lead, zinc, and copper species. FAAS was also used to determine cadmium,
chromium, and nickel concentrations for January through March 1982
samples. The latter species, however, were determined by graphite furnace
atomic absorption spectrophotometry (Gr'AAS) for the remainder of 1982.
During the 1983-84 phase of the project, samples were first analyzed for
toxic metal species by FAAS and sample extracts below predetermined con-
centrations were further analyzed by the more sensitive GFAAS technique.
Analytical determination of copper species was discontinued at the
end of 1982 due to suspected contamination of samples from electrical
arcing in the high volume sampler blowers which draw air through the
filters. Copper data are, therefore, not reported here in view of the
possible sample contamination. Vanadium and manganese were added to the
1983-84 phase of the project, primarily to serve as tracer species data
for the acid rain program.
Toxic Organic Species
Toxic organic species may exist in gas phase or particulate forms in
the ambient atmosphere. Many organic species may be collected on a
suitable sorbent material contained in a cartridge through which ambient
air is drawn. An organic solvent extraction of the collected species,
followed by chemical analysis of the resultant extract, determines the
concentrations of the toxic organics in the ambient atmosphere.
In this study polychlorinated biphenyls (PCB), hexachlorocyclohexanes
(BHC), and phthalate species were selected as toxic organics to be
determined in ambient air samples by collection on sorbent media. An
additional toxic organic, benzo[a]pyrene (BaP), was determined using TSP
filter samples.
Sorbent cartridges (0.75 x 5 inch glass tubes) containing activated
Florisil (7-8 grams, 60-100 mesh, held in place by glass wool end plugs)
were attached to ollless vacuum pumps by Tygon tubing. A total of 17 to
20 cubic meters of air was drawn through the cartridge at a constant rate
over a 24 hour period for each sample.
Following sample collection, the sorbent was eluted with a 1:1
hexane:ether mixture (100 ml) and the eluat.e (containing collected PCBs,
BUCs, and phthalates) concentrated to about 1 ml. The concentrate was
rechromatographed on a column (1 x 30 cm) packed with 3% deactivated
Florisil (10 g). Two 100 ml fractions were collected. The first fraction
was eluted with 6Z ether in hexane and contained the PCBs and BHCs.
557
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Phthalates were collected in the second fraction which was eluted with 20%
ether in hexane. Both fractions were concentrated to I ml and transferred
to vials for analysis by gas chromatography (GC).
Analysis was performed by electron capture (EC) detection on a
Hewlett Packard 5840 gas chromatograph equipped with an SE-54 capillary
column (60m) using hydrogen carrier gas and argon/methane makeup gas.
Following a one minute initial hold, the column oven was temperature
programmed from 80°C to 260°C at a rate of 5°C/min with a 15 minute final
hold. The injector and F,C detector temperatures were 225°C and 310°C,
respectively.
BaP analysis was performed on one TSP sample per month, using the
same filter sample which was analyzed for toxic metals, provided
sufficient sample remained after the metal analysis. Otherwise, another
filter collected during the same month was used. FifLy percent of Lhe TSP
filter was extracted with benzene and the extract concentrated to 1 ml.
The concentrate was chromatographed on a 3% deactivated silica gel column
(1 x 30 cm, 35-70 mesh, 10 g) in hexane. Elution with 25 ml hexane was
followed by a 60 ml, 6i4 hexane:methylene chloride elution. The first
fraction was discarded and the second fracLiori concentrated to 1 ml then
transferred to vials for automatic injection to a GC for analysis by flame
ionization detection (FID).
A Hewlett Packard 5880 GC-FID instrument was equipped with an SE-30
capillary column (30m) for BaP analysis. The column oven was temperature
programmed from 80°C to 275°C at 10°C/min with a 20 minute final hold.
Injection port and FID temperatures were 225°C and 280°C, respectively.
Helium was used as both carrier and makeup gas.
Field Sampling
TSP filters were collected according to Federal Reference Methods2'3
which address such necessary issues as flow rate calibration, total volume
air sample calculation, and sample handling and transport to analytical
laboratory facilities. Detailed information on the TSP network procedures
may be found in the Division of Air Resources Annual Report4.
Air flow measurements were performed on the Florisil cartridges
before and after sampling. The average flow was used to calculate the
total air volume sampled. During 1982 and 1983, additional flow
measurements taken at the sample sites were found to be within 8.4% of the
average flow calculations.
Filter and cartridge samples were collected over 24 hour periods
(midnight to midnight) on a 6 day schedule from January through March 1982
and generally on a 12 day cycle thereafter. Site operators were respon-
sible for ensuring proper sample identification, recording flow related
equipment measurements, preparing clean filters and cartridges for the
succeeding sampling period, and forwarding collected samples by mail to
project analytical staff.
Quality Assurance
Quality control measures for toxic metals included reagent and filter
blank analyses, spiked sample recovery determinations from clean and
sampled filters, and duplicate analysis of filter aliquots.
558
-------
Quality control for BaP included recovery analysis from spiked glass
fiber filters and recovery analysis from the 3% deactivated silica gel
column. Spiked Florisil cartridge tests were performed for PCBs, BHCs,
and phthalates. In addition, blank (clean) filter and Florisil cartridge
analyses were also performed.
Assurance testing was undertaken to insure against organic break-
through in the Florisil cartridge and also to establish analytical
procedures which unambiguously separated BHCs and phthalates into separate
elution fractions. The procc ires previously described accomplished the
latter by rechroroatographing the Florisil sampling cartridge eluate into
two fractions on a second Florisil column. This procedure was necessary
because BHCs were potentially more mobile in the cartridge and con-
sequently may have been partitioned into either or both fractions of a
simple two stage elution of the sampling cartridge.
Results
Toxic Metals
The 1982-84 TAM study collected nearly 400 TSP filters at the 11
sites given in Table II. The 1982 sites were located in western and
central New York and in the upper Hudson Valley. The 1983-8A sites were
lower Hudson Valley and metropolitan New York City locations. The
background Lake Placid site was operative in both periods of the study.
Five toxic metal species were determined throughout the study
(cadmium, Cd; chromium, Cr; nickel, Nij lead, Pbj and zinc, Zn). In
1983-84 two additional metal species were added (vanadium, V; and
manganese, Mn). In the 1982 phase, 20 to 24 measurements (24 hour
samples) were available at each site for Pb and Ni. For the other metal
species, several samples yielded less than detectable levels during the
first three months of the project. Also, during this period Zn was not
included in the analysis of some samples. For the remainder of 1982
significant improvement in the minimum detectable levels (MDL) for Cd and
Cr provided greater sensitivity for these species. However, only 9 to 11
samples using improved analytical procedures with lower MDLs were
available at several sites for some species.
Ambient concentrations of toxic metals at each site are expressed as
ratios relative to the acceptable ambient level (AAL). This normalization
simplifies presentation and discussion of the data. Typical ambient
concentrations are less than one-tenth or one-twentieth of the AAL (0.1
AAL or 0.05 AAL). In some cases, however, maximum observations (single
samples) may exceed 0,5 AAL. Figures 1-3 present the maximum and mean
(arithmetic) concentrations as AAL ratios for each toxic metal species
measured at each site. The 1982 Lake Placid results are not presented, as
the data for measured species yielded similar mean and generally lower
maximum concentration values relative to the 1983-84 results at that site.
With regard to maximum values, it is important to note that a single
sample which approximates or exceeds the AAL concentration does not
necessarily indicate a danger to public health. The AAL values for each
toxic species are generally derived from the occupational health and
safety exposure regulations and include a large margin of safety
(typically a factor of about 300). Thus, an ambient concentration equal
to the AAL would, in most cases, be approximately 1/300 the maximum
acceptable concentration in the work environment. Furthermore, the AAL is
559
-------
established as an annual mean concentration. For this reason the mean
concentrations relative to the AAI, are important while maxima must be
considered relative to short duration exposure criteria. Maxima are given
as AAL ratios for convenience in data presentation.
In order to facilitate representation of data in which AAL ratios may
encompass two to three orders of magnitude, a logarithmic rather than
linear scale is used in Figures 1-3. The study means at each site were
below the AAL for each toxic metal species. There were, however, two
individual measurements which exceeded the AAL value. An ambient
concentration of 1.6 AAL for V was determined from one Poughkeepsie sample
and an ambient concentration of 1.1 AAL for Pb was determined from one
Hempstead sample.
Lead and V were the metal species which were most consistently
observed at the highest AAL ratios. In addition to the Hempstead maximum
noted above, maximum Pb concentrations were 0.19 to 0.56 AAL at urban
sites and 0.17 at the Lake Placid background site. In addition to the
Poughkeepsie maximum for V, other urban site maxima ranged from 0.27 to
0.42 AAL and a maximum of 0,10 AAL was observed at Lake Placid.
Mean normalized ratios for Pb ranged from approximately 0.08 AAL at
Lake Placid and Syracuse to 0.30 AAL at Hempstead. Vanadium study means
were 0.02 AAL at Lake Placid, 0.07 AAL at Niagara Falls, and, at the
remaining 1983-84 sites, ranged from 0.10 AAL at Hempstead to 0.35 AAL at
Poughkeepsie. No other study means exceeded 0.10 AAL for any metal
species at any site, and only Cr at Greenpoint (0.06 AAL) exceeded 0.05
AAL.
Relatively high maximum observations for Cd and Cr, 0.16 to 0.42 AAL,
were observed at Hempstead, Greenpoint, Travis, and the background Lake
Placid site. An unusually high Zn maximum, 0.79 AAL, was found in one
sample at Hempstead, This single observation was nearly an order of
magnitude greater than the next highest Zn concentration reported in the
study. Similarly, a rather high Mn maximum, 0.24 AAL, for one sample at
Niagara Falls was more than five times greater than the next highest
observation at that site and nearly two orders of magnitude greater than
the highest maximum at the other sites.
Figures 1-3 demonstrate that the toxic metal data are sometimes
characterized by maxima several times to an order of magnitude greater
than the mean value. One possible explanation for such observations is
that a specific toxic metal source may occasionally impact the receptor
site directly. This study did not, however, attempt to identify any
specific toxic metal sources.
Cadmium and Cr maxima were frequently much greater than mean values
while Pb maxima were less than a factor of 3 greater than the mean at
seven of the 11 sites and less than four times the mean at all sites. The
relatively narrow distribution of Pb concentrations at all sites may be
expected, given automotive emissions as the primary source. Automotive
emissions are likely to be more uniformly distributed both temporally and
spatially than other species.
Statistical Considerations
The annual mean is the average of the ambient concentrations for each
day of the year. However, everyday sampling was not performed in this
56Q
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study and is not the norm for most studies. Everyday sampling is
generally available only for the gaseous criteria pollutants (ozone,
sulfur dioxide, carbon monoxide, and oxides of nitrogen) through the
continuous air monitoring system. Toxic metal samples were obtained on a
12 day schedule; however, the schedule could not always be maintained so
that sets of only 21 to 27 data points (less for some data in 1982) were
available to compute the study means.
Statistical methods permit the estimation of population means on the
basis of the individual sample values from small data sets. Statistical
analysis using the "bootstrap" resampling technique6 determined the 95%
confidence upper limit of the annual mean AAL ratio for the two highest
toxic metal study means: V at Poughkeepsie, 0.35 AAL; and Pb at
Hempstead, 0.30 AAL. The results are given in Table III.
Since Table III is for the highest AAL ratios, there is a high degree
of confidence that the annual mean for measured toxic metal species is
less than one-half the AAL at all study sites. Much lower annual means,
0.01 to 0.1 AAL, are indicated at most sites for all species except Pb and
V. It should be noted, however, that the data sets exhibit considerable
scatter, as evidenced by the high relative standard deviation values.
Comparison with Historical Data
Toxic metal ambient concentration data from previous studies may be
compared t:o TAM data. Toxic metal data has been obtained nationwide for
over a decade by the Environmental Protection Agency's National Air
Sampling Network (NASN). NASN samples were collected using a biweekly
random schedule (26 samples per year) in 1970-71 and a 12 day sampling
schedule in 1972-74®. Quarterly means and annual means were reported for
six toxic metal species common to TAM. A New York State DEC study7 for
six study sites in Buffalo and a background site at Angola during 1978-79
also provided data for six toxic metal species. A quantized presentation
of the means and maxima for these studies may be found in Figures 4 and 5,
providing a historical perspective on nominal urban ambient concentrations
for toxic metal species. It is cautioned that sites are not necessarily
the same, although located in the same city. Differences in analytical
procedures may also bias comparisons. Nonetheless, the data would appear
to indicate an improving picture for Pb and V, the species with the
highest AAL ratios. Furthermore, for other metals, the historical and
present indications are that mean concentrations are typically less than
0.1 AAL and maxima above 0.5 AAL are not frequent.
Figures 4 and 5 present the maxima and means as AAL ratios,
segregated by general site geographical location within New York State.
The presentation of individual metal concentrations within a discrete AAL
ratio regime is given for comparative convenience and does not represent
relative relationships within the regime.
For both maxima and means, Pb and V are the toxic metal species which
have been observed at the highest AAL ratios. Comparisons may best be
made for those sites which were the same in both the TAM study and NASN
studies (Niagara Falls, Rochester, Syracuse, and Albany-Rensselaer). In
all cases, the Pb concentrations are lower, most dramatically at Syracuse
and Albany-Rensselaer, in 1982-84 relative to 1970-74. Vanadium data was
not available for all sites and several different sites were employed in
the New York City metropolitan area, making V trends more difficult to
discern. Nonetheless, it would appear that somewhat lower V maxima and
means have been observed in the New York City area in 1983-84 relative to
the NASN data of over a decade ago.
561
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Toxic Organic Species
Phthalates. The extracts from the Florisil cartridges were analyzed
for eight phthalate species: dimethyl, phtbalate (DMP), diethyl phthalate
(DKP), diisobutyl phthalate (DIBP), dibutyl phthalate (DBP), butylbenzyl
phthalate (BBP), diisooctyl phthalate (D10P), diphenyl phthalate (DPP),
and dloctyl phthalate (DOP). Of these species, DPP and DOP were never
observed at atmospheric concentrations above a 5 nanogram/m3 minimum
detectable level (MDL) for 369 cartridge samples at the 11 sites over the
three year study period. DMP was detected in excess of a 3 ng/m3
atmospheric concentration MDL in less than 3% of the samples (highest
measurement 31 ng/m3). Of the remaining five phthalate species, DIOP and
DIBP were most frequently detected; however, maximum concentrations (303
and 130 ng/m3 respectively) were very low relative to the established
16700 ng/m3 AAL. Furthermore, these measurements were complicated by the
fact the DIOP and DIBP were potentially system contaminants (from plastic
components of the system and tubing) and significant amounts were measured
in analytical blanks, necessitating correction by blank subtraction for
ambient sample concentration calculations. Thus, there is the possibility
of incorrectly attributing to the atmosphere quantities of DIOP and DIBP
which were collection system interferences.
The maximum total phthalate atmospheric concentration (sum of the
eight phthalate species) determined in this study was less than 400 ng/m3,
or less than 3% of the AAL. Average concentrations at each site were less
than 0.6% of the AAL. In the event that interferences were significant,
the actual ambient concentrations would be less than cited above. Thus
phthalate species appear to be well below the currently established AAL
concentration values.
BHCs (hexaclilorocyc tohexanes) ¦ The AAL concentration for BHCs
( 1670 ng/m3) is an order of magnitude Jess than the phthalate AAL. The
BHC species measured in this study represent four of eight known BHC
stereoisomers^.0 , All isomers were detecLed at very low ambient
atmospheric concentrations (less than 10 ng/m3) and very infrequently
above 1 ng/m3 in the case of the $ , J and S isomers (2.2%, 1,4%, and
1.1% of 368 cartridge samples). The isomer was found at ambient
concentrations in excess of 1 ng/m3 in 31% of the samples. This
observation is interesting in that the 5 isomer is the only one of the
BIIC isomers which is biologically active and is solely responsible for the
insecticidal properties of BHC commercial products®.9 . Lindane is 99%
pure 6 isomer, but other commercial products may be mixtures of BHC
IsomersO.io . Thus the relative frequencies of observation at detectable
levels of the «=-< and 8 isomers suggest BHC sources other than Lindane
in the environment, or chemical mechanisms which would account for
observed concentrations.
Total BHC concentrations in the study environments did not exceed 1%
of the AAL in any single sample and yearly average concentrations were
estimated to be on the order of 0.1% of the AAL or lower.
PCBs (polychlorinated biphenyls). Florisil cartridge air samples
were analyzed for four PCB species (Aroclors 1016, 1254, 1221, and 1260).
Of 368 samples, none were found to exceed th 1 ng/m3 atmospheric
concentration MDL for Aroclor 1260 and only one sam^e was found to exceed
this concentration for Aroclor 1221. Aroclors 1016 and 1254 were found to
exceed this level in 24% and 22% of the samples, respectively.
The highest total PCB concentration measured was approximately 13
ng/m3, less than 1Z of the AAL (1670 ng/m3). Annual averages were
estimated to be on the order of 0.2% of the AAL or lower.
5G2
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BaP (benzol ajpyrene), Atmospheric BaP concentrations were
determined by analysis of particulate filters. In 1982, samples were
analyzed on a nominal one month basis (10 to 12 samples at each site). In
1983-84, between 9 and 16 samples were available from each site. The AAL
concentration for BaP is 33 ng/m3, The maximum ambient concentrations
determined were 2,2, 2.1, and 4.5 ng/m3 in 1982, 1983, and 1984,
respectively, while typical concentrations were less than 1 ng/m3, The
maxima were approximately 7Z to 14% .of the AAL while annual averages may
be estimated at 2% of the AAL or lower.
Dioxins and Furans. One year studies were conducted at Niagara
Falls and Hempstead, Long Island, to determine ambient atmospheric
concentrations of dioxins and furans. Sample collection was performed by
NYSDEC and chemical anaLysis by gas chromatography - mass spectrometry
(GC-MS) was accomplished by the Wadsworth Center for Laboratories and
Research of the NYS Department of Health. The results were evaluated by
.VYSDEC and the Division of Environmental Health Assessment of the NYSDOH.
The study results are available in detail from the NYSDEC 1 . In summary,
the data represent the first unambiguous measurement, of these species in
ambient air in the U, S.; however, evaluation of the data did not indicate
any acute or immediate heaLth hazard.
Twelve samples were obtained at Niagara Falls and four samples
contained quantifiable amounts of furans. Three samples were found tD
have non-quantifiable traces of furan species. The remaining five samples
did not yield detectable levels of furans. The measurable quantities,
calculated as ambient air concentrations, ranged from 1.0 to 13.6 pg/m3
(picograms/m3) with three samples in the 1.0 to 1,3 pg/m3 range. Only one
of the twelve samples contained a quantifiable amount of dioxin, 1.2 pg/m3
(expressed as an ambient air concentration). At the Hempstead site, alL
samples resulted in below detectable concentrations of dioxins and furans.
A statistical analysis of the furan data at Niagara Falls using the
"bootstrap" resampling technique6 was performed by NYSDEC to give a 95%
confidence interval for the annual mean furan concentration. The upper
bound of the annual mean was approximately 4 pg/m3.
Seasona L Variation
Ambient organic measurements (PCBs, BHCs and phthalates) were grouped
by three month periods, and the average ambient measurement for each
quarter determined to provide Insight on seasonal variation in the data.
The average ambient organic measurements in each quarter at each site are
given in Figure 6. For 1'CBs and BHCs, the maxima appear primarily during
the third quarter. The seasonal variation for total phthalate species is
much less pronounced; however, 5 of 11 sites observed maximum average
measurements in the third quarter and 4 sites observed maximum average
measurements in t.he fourth quarter. In four of the six cases when the
third quarter average measurement was not the seasonal maximum, the third
quarter average measurement was 50% or more of the maximum,
These results must be considered preliminary and additional
statistical evaluation of the small data sets involved is required. It
would appear that certain factors (chemical use or meteorology, for
instance) associated with I he third quarter may induce relatively higher
ambient organic concentrations.
563
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Conclusions
* For ten sites representative of urban New York communities, there is a
high degree of confidence that the mean ambient air concentrations of
seven toxic metal species, phthalates, BHCs, PCBs, and BaP do not exceed
the established AAL concentrations.
>'< At Niagara Falls, the detected ambient air concentrations of dioxins and
furans do not pose immediate or acute health hazards, based on the limited
avaialble data. Sampling during the same period at Hempstead did not
detect the presence of dioxins or furans.
A Pb and V are the toxic metal species observed in the highest
concentrations relative to the AAL. Historical data indicates a decline
in both maxima and mean concentrations for these species.
* The mean ambient concentrations of Cd, Mn, Ni and Zn have been
consistently below 0.05 AAL at sites similar to TAM sites and were also
below 0.05 AAL at all TAM sites.
* TAM data and historical data indicate mean ambient concentrations of Cr
have declined from the 0.05 to 0.25 AAL range to below 0.05 AAL at the TAM
and similar sites with the exception of Greenpoint (Brooklyn) where the
estimated 1983-84 mean concentration was 0.06 AAL.
* Mean phthalate, BHC, and PCB ambient concentrations were estimated to be
less than 0.01 AAL at all TAM sites. The mean BaP ambient concentrations
were estimated to be less than 0,03 AAL at all TAM sites.
Acknowledgements
The authors wish to thank Dr. J.Y. "Mike" Ku, NYSDEC, Division of Air
Resources, for providing the bootstrap statistical analysis for toxic
metals data. Additionally, the authors gratefully acknowledge the
assistance of NYSDEC staff members Carol Clas, Linda Stuart and Stephanie
Liddle in preparing the graphics and the typewritten copy for this
manuscri pt.
564
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References
1. "NYS Air Guide-1, Guidelines for the Control of Toxic Ambient Air
Contaminant, 1985-86" New York State Department of Environmental
Conservation, Division of Air Resources, 50 Wolf Road, Albany, NY
12233-0001.
2. US Federal Register, 36, 8186, April 30, 1971.
3. US EPA, "Quality Assurance Handbook for Air Pollution Measurement
Systems, Vol, II: Ambient Air Specific Methods,"
EPA-600/4-77-027a, May, 1977.
4. "Division of Air Resources Annual Report," Now York State
Department of Environmental Conservation, 50 Wolf Road, Albany,
NY 12233-0001.
5. B. Efron, The Jackknlfe, the Bootstrap, and Other Resampling
Plans, Society for Industrial and Applied Mathematics,
Philadelphia, PA, 1982.
6. G.G. Akland, "Air Quality Data for Metals 1970 through 1974 from
the National Air Surveillance Networks," US EPA Environmental
Monitoring Series, EPA-600/4-76-041, August, 1976.
7. N.P. Kolak, J.D. Hyde, R. Forrester, "Particulate Source
Contributions in the Niagara Frontier," EPA 902/4-79-006,
December, 1979.
8. C.R. Noller, Chemistry of Organic Compounds, 3rd ed., W.B.
Saunders Co., Philadelphia, PA, 1965, pp. 466-467.
9. The Merck Index, 10th ed., M. Windholz, Editor, Merck & Co. Inc.,
Rahway, NJ, 1983, p. 789.
10. Kirk-Othmer Concise Encyclopedia of Chemical Technology, M.
Grayson, Editor, Wiley-Interscience, New York, 1985, pp. 269-270.
11. "Ambient Air Monitoring for Chlorinated Furans and Dioxins at the
New York State DEC Air Monitoring Station, Niagara Falls, New
York," Division of Air Resources, NYSDEC, 50 Wolf Road, Albany,
NY 12233-0001, October, 1985.
565
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TABr.E I
TOXIC AIR MONITORING CONTAMINANTS AND A AT
AAL*
Pollutant (nanoerains/n: ) Hajor Emission Source (s)
Cadini urn
Chrcraiwr:
Copper
Nickel
Lead
Zinc
Vanadium **
Manganese **
167
<.000
3300
1500
167
16700
Ore processing, plating
operations, pigirent
manufactu r i n g
Iron, steel, and non-
ferrous alloy production,
chrome plating, pagrcent
production
The manufacture of bronzes,
brass, copper alloys,
electrical conductors, etc.
Iron and steel alloy
production, combustion
of coal and fuel oil
Automotive vehicles,
battery manufacturing,
non-ferrous foundries
1670D Ore processing
galvanizing
Byproduct of ore
processing, combustion
of coal ar.d fuel oil
Soeltlng and refining of
iron ore, coobustlon of
coal and fuel oil
VALUES
Health Effect
Potential human
carcinogen
HvLTLan carcinogen
Low to*icity.
Soluble salts as
copper sulfate are
irritants to skin
and mucous mambranei.
Potential human
carcinogen
Organic Pb com-
pounds nay cause
permanent brain
damage* colic
anecia and changes
in bone marrow.
Zinc is relatively
non-toxic orally.
Inhalation of zinc
oxide fume causes
"Metal Fume Fever".
Carcinogenesis is
contradictory.
Respiratory effects,
gastro-intest inal,
kidney injury,
nervous disorders
Potential mutagen,
respiratory effects
Beniofajpyrtne
Folychlorinated
biphenyIs
(PCBi)
33 Cake plants, combustion
of coal, oil and wood
1670 Electrical applications,
pl&stlcixers, hydraulic
fluids, etc.
Human carcinogen
Potential human
carcinogen
Hexachloro- 167 0 Insecticides - Lindane is
cyclohexanes also used as a therapeutic
(BHCs) Agent in veterinary medicine
Carcinogenic in
animals; neurotoxic
effects in huuans.
Cirrhosis and car**
cinoger.icity in
huiaans require
further evaluation.
Phthalate
compounds
16700 The manufacture ,
fabrication, and use
of plastics
In general are
slightly toxic.
Hay cause eye, akin
and mucous membranea
irritation.
* Acceptable Ambient Level, from guideline document Air Guide-1 (1983-1904)
published by NYS Department of Enviroru&ental Conservation
** Preliminary AJiL values - not yet published.
566
-------
TABLE II
TOXIC AIR MONITORING SITES AND SAMPLING PERIODS
Site
Location Type
Sampling Period
Western
New York
Sites
Central
New York
Site
Hudson River
Valley Sites
Metropolitan
New York City
Sites
Rural,
Background
Buffalo
Niagara Falls
Rochester
Syracuse
Residential
Industrial/Residential
Urban
Urban
Rensselaer
Poughkeepsie
Greenpoint (Brooklyn)
Susan Wagner (Staten Is.]
Travis (Staten Is.)
Hempstead (Long Is.)
Lake Placid
Urban/Indus trial
Resldential
Industrial
Residential
Residential
Urban
Background
1/82-12/82
1/82-12/82
1/82-12/82
1/82-12/82
1/82-12/82
6/83-7/84
6/83-7/84
6/83-7/84
6/83-7/B4
6/83-7/84
1/82-12/82
6/83-7/84
TABLE III
STATISTICAL DATA FOR HIGHEST METAL AAL RATIO OBSERVATIONS
Toxic
Metal
Site
Number Study
of Mean Study
Samples (AAL Ratio) SD
95Z Confidence Level
Estimate of Annual
Mean to AAL Ratio
Upper Limit
Pb
Poughkeepsle
Hempstead
25
27
0.35
0.30
0.36
0.20
0.51
0.38
587
-------
NIAGARA FALLS 1982
AAL RATIOS
1 0
0 1 -
s o oi -
0 001-
B!
~ mean
Cd Cr Ni Pd Zn V
TOXIC METAL
Mr
NIAGARA FALLS 1983*84
AAL RATIOS
2 001 -
0 001-
Cd Cf Ni PD Zn V Mn
TOXIC METAL
MAX
_ Dmean
1 0 _
BUFFALO
AAL RATIOS
Cd C' Ni Pd Zn v
TOXIC METAL
¦ MAX
Q ME AN
4 0
ROCHESTER
AAL RATIOS
i
Cd Cf Ni PD Zn V
TOXIC METAL
¦ MAX
Q MEAN
Mn
Figure 1. Maximum and mean ambient concentration to AAL ratios
for toxic metal species at western New York sites.
568
-------
RENSSELAER
AAL RATIOS
POUGHKEEPSIE
AAL RATIOS
10 _
0 I _
001 _¦
¦
0 001_
1
¦ MAX
~ MEAN
Cd Cr Ni PD Zn V Mn
TOXIC METAL
o 0 01
a 0 00
~ MEAN
Cd Cr Ni PD Zn V Mn
toxic metal
1 0 _
SYRACUSE
AAL RATIOS
LAKE PLACID 1983-1984
1 0 _
AAL RATIOS
0 1
OOi I
0 001.
1
A
t
I
Cd Cr Ni PC Zn V Mn
TOXIC metal
¦ VAX
~ mean
< 0 001
~ MEAN
Cd Cr Ni PC Zn V Mn
TOXIC METAL
Figure 2. Maximum and mean ambient concentration to AAL ratios
for toxic metal species at study sites in the upper
and lower Hudson Valley regions (Rensselaer and
Poughkeepsie), the central New York region (Syracuse) ,
and the Adirondack Mountain region (Lake Placid).
569
-------
SUSAN WAGNER
AAL RATIOS
9 0 01
OCOi"
MAX
£2 MEAN
PD Zn
TOXIC METAL
GREENPOINT
AAL ratios
1 0 -
4
4
0 1 -
e o oi
0 001-
ii
Cd Cr
Ni Pd 2n V
toxic metal
Mn
¦ MAX
. ~ mean
TRAVIS
AAL ratios
4
<
<
X
to
0 1 -
0 01 •
OOCM-
1
¦ i
If
'A A
¦ MAX
. Dmean
Cd Cr Ni Pt> Zn V Mn
TOXIC METAL
HEMPSTEAD
AAL ratios
1 0
0 1 -
2 0 01
0 001-
I
£
Cd Cr Ni PC Zn V
TOXIC METAL
¦ max
.~mean
Mn
Figure 3. Maximum and mean ambient concentration to AAL ratios
for toxic metal species at study sites in the New York
City metropolitan region.
570
-------
Mean Urban and Rural Background Air Toxics
Contaminont Concentrations Relative to AAL'
from Independent Studies in New York State, 1970-1984
Centra
New
York
Western
New York
Metropolitan
New York City
RATIO
la AAL
Pt on
PO PD
0 50-1 0
025-0 50
V I V |PdI Cr PC I pp| V I Pfc
Pb p»
010-0 25
Cr ! Pb
005-0 tO
<05
Cd
Cr
Cd
Cd
Cd
Cd
Cd
Ctf
h*
Cr
Mn
O
Cr
Mn
Cr
SI
N,
Si
Ni
Ni
Ni
Ni
Zn
Zn
1 Zn
Ni
HJ
Zn
Cd
Cd
Cd
Cd
Cd
Cd
Mn
Ma
Mr»
O
O
O
Ni
Ni
NI
Un
tM
Mn
Zn
r*
Ni
NI
C
Zr
Ir.
Zn
STUDY KEYb
~ NASNcd
1970-74
I NFd
11978-79
TAMa
] 1982
TAM
1983-84
0
a - AAL Acceptable tabient Laval for tonic air contaainant (NYS),
t> - KASN ¦ National Air Stapling Network (EPA), EPA-600/4• 76-041.
NF • Particulate Source Contributions In tha Niagara Frontier
(NYSDEC. Kolab, ec *1.), EPA-902/4-79-006.
TAM • TokIc Air Monitoring (NYSDEC), thla study,
c * NASN valuea presented are highest reported annual seen In 1970-74 period,
d ~ Ln not Maaurtd In NASN Study
Cd not aeaaured ln NF Study
Hn and V not aeaaurad ir> TAM-1982 Study
Figure 4. Historical comparison of mean toxic metal AAL ratios
in several geographic regions of New York.
571
-------
Maximum Urban and Rural Air Toxics
Contaminant Concentrations Relative to AAL"
from Independent Studies in New York State, 1970-1984
Central
New
York
Metropolitan
New York City
Western
New York
I
RATIO
fo AAL
2 0-50
1 5-20
10- 1.5
075-1.0
PbrPb
U.50- .75
0 25-0 50
010-025
0 05-010
C4
-------
2
¦»»»
I
BHC SEASONAL VARIATION
AVERAGE AMBIENT MEASUREMENT BY QUARTER
4.0
3.0
2.0
1.0
0 0
sw
Ttr 7
2 3
QUARKS
3.0
2.0
1.0
0.0
PCB SEASONAL VARIATION
AVERAGE AMBIENT MEASURE K€MT BY QUARTER
ao -
IP
¦Ojx"
Bf «
v--\
2 3
OtJARTTVt
4.0
3 0
2.0
1.0
0.0
i
-
—
Cp
/ SW
X.
/
/ /a*a
2 3
OUARHIt
PHTHALATE SEASONAL VARIATION
AVERAGE AMBIENT MEASUREMENT BY QUARTER
120 i
10
1
1
r
i
y/1
1
M
S!^
<^Pk
2 3
QUARTER
Figure 6. Seasonal variation, estimated by averaye quarterly
ambient measurement s, for BIICs, PCBs, and phthalates
at TAM study sites : NF=N'iagara Falls, Bf = Duf£jlo,
Ro=Rocliester, Sy ^Syracuse, Kn-Rensselaer , LP=Lake Placid,
SHsSusan Wagner, Tr=Travis, Gp=Greer.point, H=Heinpstead,
Pk=Poughkeeps ie.
573
-------
A CONTINUOUS ISOKINETIC GAS/MIST SAMPLER
FOR FLUE STREAM EXTRACTIVE ANALYSIS
Jan E. Kolakowski
U.S. Army Toxic and Hazardous Materials Agency
Aberdeen Proving liround, Maryland 21U10
Daniel P. Lucero, Member of the Technical Staff
Materials Control Directorate
The Aerospace Corporation, Suite 4000
9t)5 L'Enfant Plaza, S.W.
Washington, U.C. 20024
A special-purpose stream sampler is required for the automated and
continuous extractive analysis of saturated mist-laden flue gas streams.
Isokinetic sampling is essential for those applications In which the
arialyte molecules are miscible in or otherwise associated with the mist
droplets. Essentially, continuous isokinetic sampling is accomplished
over a 30- to 60-ft/sec flue stream velocity range by a heated sampling
probe through which a large sample (~50 to 100 liter/min) is pumped solely
by the flue stream dynamic pressure and returned directly to the flue.
The probe geometry arid dimensions are configured to permit the probe
pressure losses experienced by the sample stream to vary in proportion to
the flue stream dynamic pressure, i.e., flue stream velocity, to maintain
an isokinetic condition at the probe entrance. As the sample flows
through the probe, it is heated, arui the mist droplets are^vaporized by
the energy from the probe wall, which is maintained at 340°F. Near the
probe exit and prior to return of the sample stream to the flue, a second
probe extracts continuously a small fraction (~1 to 2 per cent) of the
sample stream for further processing, if required, and subsequent
analysis. Because the analyte and water molecules at the heated probe
exit exist in gas phase, isokinetic sample extraction is not required for
operation of the second probe. Efficient sample transport through the
heated probe is attained by vaporization of the mist droplets and liquid
phase altogether, which precludes the formation of absorbing wetted-wall
surfaces.
574
-------
A CONTINUOUS ISOKINETIC GAS/MIST SAMPLER
FOR FLUE STREAM EXTRACTIVE ANALYSIS
Introduction
Flue gas monitoring of waste incinerator systems for hazardous and
toxic emissions imposes two major requirements on the overall analytical
process not associated normally with source monitoring systems;! (n an
analyzer lower detection limit at sub-ppm to sub~ppb or lower levels^
and (2) relatively high molecular detection specificity.4>5 Because of
the detection response requirements, extractive analytical techniques are
used in most applications. Cross-stack, in situ, and remote analyses
usually do not possess the sensitivity or zero-span stability to attain
the lower detection limit required and do not accommodate dynamic
calibration methods well.
However, attendant to extractive analysis are sample stream
conditioning ana processing (particulate filtering, dilution, heating,
etc.).l>6~^ Additional requirements arise for applications in which the
analyte species is above its dew point in the flue stream but miscible in
a liquid medium, such as mist, that the flue stream may carry or in liquid
films attached to solid surfaces.
For most mist-laden flue streams, a substantial fraction of miscible
analyte molecules can be dissolved in individual mist droplets. Thus, for
those applications, two additional constraints are imposed on the
extractive sampling process: (1) it is imperative to perform the sampling
isokinetically within the flue to obtain a sample stream representative of
the larger mist droplets (>0.5 urn)* carried by the flue streanr0-13 and
(2) the sample stream must be transported to the analyzer or detector
module in a fashion that eliminates entirely the deposition of mist
droplets on any conduit walls or surfaces. An accumulation of mist on
surfaces can eventually transform the external sample stream conduit into
an absorbing wetted-wall column that will deplete the gas stream of
miscible analyte molecules^,15 prior to its arrival at the analyzer.
Waste Incineration Effluent
A typical incineration system was examined that included a downstream
in-line water quench tower, a venturi scrubber, a packed-bed scrubber, a
inist eliminator assembly, and a forced-uraft flue. The average flue gas
temperature is 170*F and gas velocity varies from 30 to 60 ft/sec. It is
saturated with water vapor and can carry a mist load of 10-2 to 10-3
mass-liquid/mass-gas. A significant inist load is present despite mist
elimination in-line equipment. 16
The resultant liquid mass loading and its dispersion as a mist is
sufficient to absorb a large fraction of the miscible analyte molecules
into solution and cause a significant positive or negative interferent
response in the analytical process. An engineering analysis shows that
the rale of mass transfer of miscible analyte molecules from gas phase to
^English and metric units are used throughout this document for the
convenience of the reader.
575
-------
individual droplets over the residence time of the incinerator effluent in
the flue is sufficient to scrub efficiently the flue gas of analyte
molecules.17-19 Thus, isokinetic sampling for extractive analysis of
the incineration system effluent is very likely required to obtain a
representative extractive sample of the miscible analyte molecules.
Isokinetic Gas/Mist Sampling System
All extractive sampling systems must operate under various
environmental and flue conditions. In each case, constraints are
established by sampling requirements that are defined by the analyte
molecules, the flue and its effluent properties over a range of operating
conditions, the interface constraints of the sample probe/collector in the
flue stream, and the analyzer interface constraints.
The unique ana most severe system requirements are those related to
simultaneous gas and mist collection uncer isokinetic conditions. In
addition, it is imperative to transport the sample to the analyzer in the
gas phase entirely without mist deposition on the sample conduit walls.
This constraint arises primarily from analytical considerations, as well
as from system reliability and low maintenance considerations.1.6.8.20
Figure 1 is a functional illustration of the isokinetic gas/mist
sampling system. It comprises two subsystems: (1) the effluent probe and
sample processor, operating inside the flue, and (2) the sample transport
network and processor, operating outside the flue.
A special-purpose effluent probe and sample processor was designed to
perform the isokinetic sampling and processing within the flue. It is
called VapaTroy for brevity. It is a 2-stage sampling probe comprising a
heated and insulated tube that is oriented longitudinally in the flue, as
Shown in Figure 2. Effluent enters the heated tube at a velocity near
that of the free stream (i.e., isokinetically). As the effluent sample
stream flows through the tube, it is heated, and the mist droplets are
vaporized. The effluent sample stream continues out the heated tube and
is returned directly to the flue. Upstream of the tube exit,
approximately 1 to 2 per cent of the effluent stream is bled off by the
bleed stream probe, which is at a slightly reduced pressure. The bleed
stream is transported through heated lines that pass through the flue wall
to the sample transport network and processor and subsequently to the
analyzer. It is important to note that only the flue effluent stream is
samplea isokinetically. There is no need for isokinetic sampling at the
bleed stream probe because, at this station in the heated tube, the
effluent sample stream does not contain mist droplets; these have been
vaporized. Thus, to minimize the ingestion of solid aerosols, the bleed
stream probe is oriented to the fh.e stream as shown by Figure 2 to force
the gas to negotiate a 180-degree turn (i.e., to sample nonisokinetically).
mean
VapaTrog performs the isokinetic sampling function entirely by passive
s, i.e., the effluent probe itself is self-adjusting to a varying flue
gas velocity without active assistance from downstream valves, pumps,
etc. This action is possible because of VapaTrog's pneumatic
configuration, whereby an effluent sample stream passes through a tube and
is returned directly to the flue. The effluent sample stream is thus
pumped solely through the heated tube by the flue stream dynamic
pressure. Its flow rate varies in proportion to the flue stream dynamic
pressure.
576
-------
The isokinetic condition exists when the effluent sample stream
velocity at the probe entrance plane is equal to the flue gas free stream
velocity.13 p0r isokinetic flow, the effluent sample stream is
described by:
Wv = kpfVcAj
(1)
where Wv = effluent sample stream flow rate through the heated
tube, Id/sec;
k = isokinetic factor proportional to the probe inlet to
free stream gas velocity ratio, dimensionless;
pf = flue gas density, lb/ft^;
Vf = flue gas velocity, ft/sec; and
^i = tube inlet area, ft?.
For isokinetic sampling, k = 1.00.
To obtain the effluent san:ple stream flow rate described by Eq.
(1), a combination of the tube dimensions and geometry and the inlet area
are designed such that the pressure loss incurred by the effluent sample
stream in flowing through the tube is equal to the total pressure
difference available from the tube entrance to its exit. The total
pressure difference established aerodynamically is proportional to the
dynamic pressure as follows:
(ap),
U * ck)
if
(2)
where (aP)v = maximum aerodynamic pressure difference available
from the tube entrance to exit, lb/ft^;
Cfo = base pressure coefficient at tube exit,
dimensionless; and
qf = flue gas dynamic pressure, lb/ft^.
The total pressure loss experienced by the effluent sample stream
in traversing the length of the tube is the sum of entrance, expansion,
contraction, frictional, and exit losses. For entrance and exit sections
designed for low pressure losses, the sum of entrance, exit, expansion,
and contraction losses can be minimized to less than 2 per cent of the
total pressure loss. VapaTrog was designed such that the effluent sample
stream operating pressure drop is mainly frictional, as shown below:
(lp)c = 4f U/;)) qv
(3)
577
-------
where UP)t = total or frictional pressure loss of effluent sample
stream in traversing the length of the tube, lb/fts
f = effluent stream Fanning friction factor,
dimensionless;
L = tube length, ft;
D = tube inside diameter, ft; and
qv = effluent sample stream dynamic pressure, lb/ft^.
Because the effluent sample stream frictional pressure loss, UP)t> is
equal to the maximum aerodynamic pressure difference available from tube
entrance to exit, (aP)v, a combination of Eqs. (1), (2), and (3) is
reduced to:
A.
(Pv/Pf) (1 ~ cb)
1/2
where k
pv
64f
1.00 for the isokinetic condition and
(4)
average gas density of the effluent sample stream in
the tube, lb/ft^.
Note that flue gas velocity, Vf, drops out of the relationship and k is
independent of Vf.
It is certain that variations in pv, pf, and f arise over the
range of flue conditions encountered, and these variations will produce
corresponding variations in the isokinetic sampling as described by Eg.
(4). For example, the flue gas temperature will vary from 160 to 180 F,
and the effluent sample stream flow rate will vary from 50 to 100
liter/min, as determined from the flue gas velocity range and Eq. (1).
Temperature changes affect primarily the gas density terms in Eq. (4).
There is also negligible change to the effluent sample stream Reynolds
number arising from changes to the gas viscosity with temperature. A +1
per cent deviation from isokinetic sampling is ascribed at a i70°F
temperature level and to a ±10°F variation in the flue and heated tube.
Pneumatic effects on f in Eq. (4) are more difficult to predict
analytically. It is estimated that the Reynolds number of the effluent
sample stream will be 2300 and 4600 at flue gas velocities of 30 and 60
ft/sec, respectively. At these levels, the effluent sample stream flow is
in the transition region between laminar and turbulent flow modes. By a
tenuous interpolation of the Fanning friction, f, curve?! in the
transition region, f may vary from 0.U0B5 to 0.0095, to produce a ±2 per
cent variation. The total maximum departure from isokinetic sampling is
estimated to be ±3 per cent for the flue conditions described earlier.
578
-------
Vapatrog Design
A prototype VapaTrog unit was designed and fabricated for test and
evaluation. Figure 3 illustrates its basic functional elements, geometry,
and configuration. The dimensional specifications are established
primarily by the maximum total flow rate requirement of the effluent
sample stream and the heating load constraint defined by the sample stream
heat capacity and mist loading. Inlet area is defined by Eq. (4); the
heated tube length and diameter are constrained by Eqs. (3) and (4). To
ensure that the effluent bleed stream aoes not interfere significantly in
processing the effluent sample stream the bleed stream is maintained at a
flow rate level sufficient to supply the analyzer interface requirements
and not exceed 2 per cent of the effluent sample stream at any time. For
example, an analyzer interface requiring a 1-1iter/min minimum bleed
stream flow rate will constrain the minimum effluent sample flow rate of
50 liter/min at any operating and flue condition.
The heated tube dimensions must be compatible with the thermal and
pneumatic constraints imposed functionally by the VapaTrog performance
requirements. A combination of heat transfer surface area and convective
film coefficient must be developed to provide a heat flux of sufficient
magnitude to heat the effluent sample stream to 340 °F and to vaporize the
mist droplets the stream carries. Yet the combination of heated tube
lenyth and diameter must also provide the means to limit the effluent
sample stream flow rate to incur the pressure drop prescribed by Eq. (3).
VapaTrog comprises a two-concentric-tube assembly 56 in. long with its
annular gap sealed at each end: a nose cone seals the front end, and a
base plate seals the rear end. The outer surface of the inner tube, i.e.,
the heated tube, is surrounded over nearly its entire length by two 500-W
wrap-around heaters, a layer of thermal insulation, and finally, the outer
tube, 4 in. in diameter. The nose cone is interfaced mechanically with
the inner and outer tubes.
Test and Evaluation
Tne VapaTrog test and evaluation was focused primarily on two
objectives: (1) establish and demonstrate the aerodynamic characteristics
of VapaTrog regarding isokinetic sampling performance over a 30 to 60
ft/sec flue gas velocity range and (2) define VapaTrog performance
regarding its mist collection and processing characteristics.
In both cases, a fully instrumented vertical wind tunnel?? was used
to simulate the flue and flue stream. All aspects of the flue were
simulated, with the exception of gas temperature and composition. The
VapaTrog unit was suspended longitudinally in the wind tunnel, with the
inlet facing downward and opposed to the wind direction.
The aerodynamic characterization was performed by a quantitative
examination of the mass conservation relationship at the VapaTrog inlet
and exit. At the inlet, the flow rate entering VapaTrog is described by
Eq. (1). The wind tunnel gas stream and properties and VapaTrog gas
sample stream and properties were measured over wind tunnel gas velocities
from 30 to 60 ft/sec. By mass conservation at tne VapaTrog inlet (Eq.
(1)) and at the exit (denoted by the subscript, x), the inlet isokinetic
579
-------
factor, k, is related to the measured parameters of the experiment as
described below:
k =
(5)
where px
the average gas density of the effluent sample stream
at the heated tube exit, lb/ft^;
the average velocity of the effluent sample stream at
the heated tube exit, ft/sec; and
cross sectional flow area at the heated tube exit,
ft2.
Eq. (5) describes how well VapaTrog is operating isokinetically. For
absolute isokinetic sampling, k = 1.00. Deviations of k from 1.00 are
its departure from isokinetic sampling. Wind tunnel free-stream density
was determined from static temperature and pressure measurements, and
velocity was obtained from the free-stream dynamic pressure. Five
individual dynamic pressure measurements were made in the VapaTrog heated
tube for all operating conditions to construct the exit velocity
profi le<^,24 arid obtain an average exit velocity, Vx.
The dynamic pressure measurements were reduced to velocity data at
each radial position for each VapaTrog inlet over 30 to 60 ft/sec wind
tunnel stream velocity, as shown in Figure 4, With these data and the
wind tunnel free-stream measurements, Eq. (5) was evaluated to assess the
isokinetic sampling performance of VapaTrog.
The VapaTrog mist collection and processing evaluation was performed
in a vertical wind tunnel subsequent to the aerodynamic evaluation. The
evaluation comprised operation of the wind tunnel and mist generator and
measurement of the wind tunnel free-stream parameters, mist droplet
population density, and droplet size distribution. In addition, the
VapaTrog unit was equipped with a bleed stream probe and line of
l/b-in.-OD bare TFE tubing immersed approximately 4 in. into the heated
tube exit and insulated thermally thereafter.
The effectiveness of VapaTrog to collect a representative sample of
flue gas and mist is a function of the VapaTrog isokinetic sampling and
its efficiency in vaporizing the mist droplets carried by the effluent
sample stream. A mass conservation relationship is used to assess
VapaTrog's mist collection and processing characteristics. It relates the
water entering VapaTrog as liquid ana vapor to the total water content of
the bleed stream.
Gas and mist are sampled continuously by VapaTrog over a given time
increment, and the tunnel gas mist loading is measured at the VapaTrog
inlet by a droplet-counting anemometer. Simultaneously, the bleed probe
and line transport a 1000-inl/min stream of effluent sample to an assembly
of three containers in series immersed in an ice bath and subsequently to
Mist Collection and Processing
580
-------
a flow meter. The liquid water collected at 0oC is the water vapor that
condenses out of a water-saturated stream at 0 C. The mass of liquid
water collected in the ice bath is equal to the water vapor enterjng the
ice bath less the water vapor leaving the ice bath saturated at 0°C. The
mist loading of the wind tunnel is obtained from these parameters as shown
by Eq. (6):
W
V1 PI + (wH20)0° (*t) QtJPr
QBPr (At)
wH20 (6)
where V] = liquid water volume collected at 32 °F, cm^;
PI = liquid water density at 32 °F, g/crn^;
W = tunnel air mist loading, mass liquid water/mass air;
(at) = collection time interval, min;
pr = room or tunnel air density, g/cm^;
Qa = bleed stream flow rate measured downstream of the
collection bath, ml/rain; and
(Wh o)o" = saturated air specific humidity at 32 *F, mass water
2 vapor/mass dry air.
An indirect but important measure of the VapaTrog k is obtained from a
comparison of the mist loading calculated frocn Eq. (6) with the mist
collection test parameters and the mist loading measured at the VapaTrog
inlet. This approach represents independent verification of the
isokinetic sampling action because nonaerodynamic parameters are used in
the execution of Eq. (6).
Results
The mist collection test and evaluation results are summarized in
Tables I and II. Figure 4 illustrates the reduced aerodynamic data. All
final data reduction was executed by Eqs. (b) and (6) for the aerodynamic
and mist collection characteristics, respectively.
Aerodynamic Characteristics
The primary objective of the VapaTrog aerodynamic test and evaluation
was to define experimentally the isokinetic sampling factor, k, over the
range of flue gas conditions described earlier. However, only the more
important conditions affecting k were simulated. Operational data were
obtained at ambient conditions as a function of wind tunnel air velocity
and VapaTrog inlet diameter as listed in Table I. In addition,
supplementary data were obtained to augment design information and to
support the validity of Eq. (4).
Aerodynamic data were recorded for the 0.440-, 0.423-, and 0.405-in.
inlet diameter over 20 to 48°F and 29.30- to 30.21-in. Hg ambient
5B1
-------
temperature and pressure ranges, respectively. Ambient temperature
variations for the 0.384-in. inlet diameter extended from 74 to 78 F. For
practical reasons, the wind tunnel ana VapaTroy were operated such that
the pitot-tube position in the VapaTrog exit plane was maintained constant
while the inlet diameter was varied. These measurements were performed
over periods lasting several days with attendant changes in ambient
temperature. Thus, normalization thermally of the VapaTrog performance as
prescribed by Eq. (4) for a given inlet diameter cannot be discharged
consistently to k. Tnis limitation in the data reduction process results
from the derivation of the local exit velocity of the VapaTrog effluent
sample stream velocity profile and subsequent resolution of average exit
effluent sample stream velocity (i.e., exit velocity profile data were
derived from cross-plots of raw data of the local exit velocity
measurements at different tunnel gas temperatures).
An examination of Table 1 data reveals that the VapaTrog sampling
operation is described satisfactorily by Eq. (4). The isokinetic factor,
k, is reasonably constant over the wind tunnel air velocity range scanned
for each VapaTrog inlet diameter, regardless of its magnitude. In
audition, the variation of k with Af is shown by Table I. For the
conditions of the test normalized to 35°F wind tunnel temperatures, k =
1.03 for Aj = 0.116 in.^ or a 0.3b4-in. inlet diameter.
For example, considering only the data for the 0.440-, 0.423-, and
0.405-in. diameters, the k variance from the average k for each inlet
diameter extends from a ±0.7 per cent minimum to a ±3.2 per cent maximum
at 0.440- and 0.405-in. inlet diameters (see Table I, notes),
respectively. It is estimated from Eq. (4) that a maximum ±4 per cent
variance in k may be ascribed to the changes in the ambient conditions
experienced. Because of the experimental procedure by which the
aerodynamic tests were performed, it is not possible to establish the
direction of the thermal variance induced in k.
The thermal variance k for the 0.384-in. inlet diameter was minimized
in a relative sense. In this case, ambient temperature variations ranged
from 74 to 78*F, which account for less than a *2 per cent variance after
normalizing the data to 32*F. Yet the variance in k is ±5.8 per cent. An
examination of the effects of variations in the Fanning friction factor,
f, as prescribed by Eq. (4) indicates that variances of ±4.8 per cent can
be induced in k. The friction factor, f, will vary from 0.0105 to 0.0085
for corresponding effluent sample stream Reynolds numbers of 3400 and 7200
as calculated from effluent sample stream average exit velocity
measurement at 30 and 60 ft/sec wind tunnel air velocities, respectively.
However, Eq. (4) describes the effect of f on k as proportional inversely
with f. This is contrary to the data on k shown in Table I (i.e., k
decreases with increases in wind tunnel air velocity).
Variations in the base pressure coefficient, Cb, of Eq. (4) were
examined with varying effluent sample stream flow rates and wind tunnel
air velocities. For solid disks and ellipsoids of revolution, however,
the base drag coefficients over Reynolds numbers of 2000 and 500,000 are
reasonably constant at 1.0 and 0.6, respectively.25,26 Qn this basis,
variations of Cb are minimal. To determine whether the effluent sample
stream flow rate affects Cb as wind tunnel velocity varies, calculated
estimates of were obtained from the static pressure measurements of
582
-------
Table I at the VapaTrog heated tube exit. The average over a wind
tunnel velocity rariye from 60 to 30 ft/sec was 0.430, +1.5 per cent, -3.8
per cent, without showing any trend with wind tunnel velocity. It is a
small variation and does not affect k to any significance.
The preceding discussion on the effects of such parameters as pf,
C[j, and f on k suggests that some of the variance in k for the 0.384-in.
inlet diameter is due to errors arising from experimental method,
technique, or procedure.
Table I lists other aerodynamic data that substantiate the VapaTrog
principle of operation and support the validity of the measurements. It
is noted in all cases that the ratio of the average velocity to the
centerline velocity is near the theoretical value for fully developed
turbulent flow in a tube, 0.79.24 The variance of the velocity ratio
from the theoretical level as well as from the measured average is
acceptable in all cases. The maximum velocity ratio occurs with the
0.384-in. inlet diameter. The largest variance in k also occurs for this
dimension.
In addition to the performance data, verification of the VapaTrog
sampling process principle of operation was obtained. The total and
static pressure measurements listed in Table I at the VapaTrog exit plane
show a reasonable consistency at each wind velocity regardless of
variations in other operating and dimensional parameters. This condition
correlates well with the notion that despite varying conditions,
dimensions, and configuration, the VapaTrog effluent sample stream flow
rate self-adjusts to a level that attains a given pressure drop
proportional to the dynamic pressure of the flue gas. The maximum
variance from the average exit total pressure is +2.5 per cent, -1.3 per
cent at 50 ft/sec wind tunnel air velocity; the maximum variance from the
averaye exit static pressure is +2.4 per cent, -3.6 per cent at 40 ft/sec
wind tunnel air velocity. These data substantiate further the VapaTrog
principle of operation.
Mist Collection and Processing Characteristics
The primary objective of the mist collection test and evaluation was
to ascertain the quantity of mist sampled and processed by VapaTrog during
operation in a mist-laden airstream. Also, an indirect measurement of the
VapaTrog isokinetic sampling factor was obtained from a comparison of the
liquid water collected in the ice bath to the mist load measured at the
VapaTroy inlet. A 0.384-in. inlet diameter was used for all the mist
collection tests. Mist was generated by a Sonotek ultrasonic mist
generator. Measurements were made of the parameters comprising t'q. (6);
subsequently, Eq. (6) was used to derive the tunnel mist gas load.
The time-weighted average mist load at the VapaTrog inlet varied from
2.2b x 10-3 to 4.07 x 10~3 as measured by the droplet-counting
anemometer (KLD Associates Droplet Measuring Device). There was no
detectable mist at the VapaTrog outlet over the entire mist load range.
Thus, vaporization of the mist carried by the effluent sample stream
appeared to be complete.
583
-------
The mist loading, W, is calculated from the Table II summary of raw
and reduced data produced by the tests. For exact isokinetic sampling
(k = 1.00) and excluding experimental errors, the calculated mist loading,
Wc, should compare exactly with the measured mist loading, W^.
Three individual mist collection runs were taken over 275-, 336-, and
300-min intervals at corresponding wind tunnel air speeds of 39.2, 43.6,
and 47.1 ft/sec, respectively. Although the test conditions including
mist loading were reasonably similar, an examination of Table II reveals
that a large discrepancy was attained between the calculated and measured
mist loadings for two of the three test runs. This discrepancy is
inexplicable without consideration of experimental errors and the effects
of unanticipated sampling malfunctions at the VapaTrog inlet.
The most probable experimental error arises from the instabilities in
the mist generation process and the limitations of mist loading measuring
equipment at the VapaTrog inlet. As described, these circumstances led to
a measured mist load comprising a time-weighted-average over the entire
run time interval. In this regard, it is significant that run 2 yielded
the mist load comparison minimum discrepancy (+11.4 per cent), and runs 1
and 3 yielded +39.9 per cent and +47.4 per cent discrepancies,
respectively. The measured mist load for run 2 is based on 34 individual
readings over a 336-min time interval while those of runs 1 and 3 are
based on 16 and 15 readings over 275- and 300-min time intervals,
respectively. The implication is that the measured time-weighted-average
mist loading for run 2 is more accurate than those of runs 1 and 3 because
approximately twice as many readings were made.
It is also significant that the mist load comparison discrepancy is
positive for each run (i.e., it appears that more water is entering the
VapaTrog inlet than is carried by the effluent sample streams entering
isokinetically). Table I shows the isokinetic factor for the 0.384-in.
VapaTrog inlet to be 1.02 and 1.0B at 40 and 30 ft/sec, respectively. The
effect of these isokinetic factors on ingesting additional mist particles
is minimal. Only tne smaller particles (<5 pm diameter) will be ingested
by VapaTrog in greater proportion than they exist in the mist population
at the VapaTrog inlet. Tne average mist droplet diameter was near 36 to
39 pm, and the total volume per cent of mist comprising droplets less the
5 pm is less than 0.1 per cent.
A more plausible explanation for additional liquid water entering
VapaTrog arises from a combination of effects descried during the
testing. At low wind tunnel air speeds (~50 ft/sec), mist droplets
collect on the nose cone surface. Evidently, the nose cone average
temperature must be higher than 150°F to evaporate the liquid water
collecting on the nose cone surface. Eventually, a sufficient number of
the aroplets attached to the nose cone coalesce, developing into a liquid
film. The film enlarges until it forms a relatively thick toroia attached
to discontinuities on the nose cone surface (e.g., edges, grooves, joins,
etc.) where gas flow separation occurs. Also, if the mist load is high
and the wind tunnel air speed is low, this toroid of liquid can attach
itself to the sharp edge of the VapaTrog inlet. As the toroid enlarges,
it becomes unstable and oscillates vigorously in the wind tunnel airstream
until it detaches from the nose cone and is carried away in the form of a
few large droplets. There are times that a part of the liquid toroid is
584
-------
ingested directly into the VapaTrog heated tube. In this event, more
liquid water is entering the VapaTrog inlet than predicted from the
aerodynamic circumstances and mist population characteristics. It is very
probable that this effect accounts for a significant part of the positive
discrepancy between the calculated and measured mist loads.
In this regard, it may be of significance that the per cent
discrepancy between calculated and measured mist load increases with the
measured mist load as shown by Table II. In other words, these data
substantiate the likelihood that liquid water from liquid film attached to
the nose cone is ingested by the VapaTrog inlet at higher mist loading.
Di scussion
VapaTrog is a continuous gas/mist sampling and sample conditioning
probe that operates isokinetically in a completely passive manner (i.e.,
the effluent stream velocity at the VapaTroy inlet will self-adjust with
flue gas velocity without manual or automated operation of downstream
valves, vacuum pumps, or feedback devices). Tne wind tunnel test and
evaluation of the VapaTrog design provided confirmation of its isokinetic
sampling performance and its mist processing capabilities. More
specifically:
• The VapaTrog performance and operation regarding its isokinetic
sampling action as described by Eqs. (1) and (4) were verified by
the relatively small response of the isokinetic sampling factor,
k, with wind tunnel or flue gas velocity, Vf.
• The VapaTrog unit possesses sufficient thermal and heat transfer
capacity to heat the effluent sample stream from 32°F to 340°F
and to vaporize a water load of at least 6 x 10"^.
• Eq. (4) was verified because both k and Ai were shown to be
relatively independent of Vf.
• Eq. (4) can be used to design a VapaTrog unit, design
modifications, scale changes, and establish its operational
limitations for different applications and conditions than tested
in the wind tunnel.
• It is essential that the VapaTrog nose cone outer surface be
smooth or otherwise free of discontinuities that cause flow
separation and subsequent water film growth and eventual
ingestion by VapaTrog. For identical reasons, it is important
that the VapaTroy nose cone be maintained al temperatures above
212 ° F.
Acknowledgements
The authors thank the Aerodynamics Research and Concepts Assistance
Branch of the U.S. Army Chemical Research and Development Center, Aberdeen
Proving Ground, Maryland, for use of the vertical wind tunnel and
attendant facilities in the aerodynamic and water mist collection
experiments. Successful completion of this work was due to a large
585
-------
measure to the expert advice and support of Miles Miller and his staff,
Joseph Huerta, John Molnar, and Owen Smith. Their contributions are
appreciated greatly.
The authors also thank Susan Hendrickson of Sermantown, Maryland, for
managing the preparation of this manuscript.
References
1. R.L. Chapman, "Continuous stack monitoring," Environ Sci Technol, 8:
520 (1974).
2. R.R. Bumb et al., "Trace chemistries of fire: A source of chlorinated
dioxins," Science, 210: 385 (1980).
3. A. Friedman, M. Zohniser, 0. Frankel, "Spectroscopic detection of
chlorinated aromatic hydrocarbons," Symposium on Analytical Chemistry
of the Environment, 1984 International Chemical Congress of Pacific
Basin Societies (May 1, 1984).
4. C.F. Rodes, "Dilution sampling system for gaseous pollutants,"
Instrum Technol, October 1973: 41 .
5. T.W. Sonnichsen, M.W. McElray, A. Bjorseth, "Polynuclear aromatic
hydrocarbons: Chemistry and biological effects," A. Bjorseth and A.J.
Dennis, Eds., Battelle Press, Columbus, Ohio. 1980, pp. 617-732.
6. G.A. Junk, B.A. Jerome, "Sampling methods for organic compounds in
stacks," Am Lab, December 1983: 16.
7. P.W. Jones, "Measurement of PA'rl emissions from stationary sources—an
overview," presented at Polycydische Aromatische Kohlenwasserstoffe,
Hanover, Germany, September 18-21, 19/9.
8. D.P. Lucero, "Continuous N0X source analysis by a
chemiluminescent/diffusion technique," ISA Trans, 16: 71 (1977).
9. J.D. Barden, D.P. Lucero, "Monitoring industrial sulfur scrubbers by
flame photometry," Power Generation: Air Pollution Monitoring and
Control, K.E. Hall and W.T. Davis, Eds.
10. Fed Regis, _36(247):2488 (December 23, 1971).
11. Fed Regis, 41(111):23076, (June 8, 1976).
12. P.N. Cheremisinoff, A. Morresi, Air Pollution Sampling and Analysis
Deskbook, Ann Arbor Science, Ann Arbor, Michigan. 1978.
13. H.J. Paulus, R.W. Thron, Air Pollution, 3rd Edition, Vol. 3, A.C.
Stern, Ed., Academic Press, New York, New York. 1976, pp. 525-587.
14. J.H. Perry, Chemical Engineers Handbook, 4th Edition. 1963, pp. 18-56.
15. D.P. Lucero, "Theoretical aspects of a liquid chromatographic gas
phase interface," J Chromatoqr Sci, 23: 293 (1985).
586
-------
16. L.O. Johnson, R.M. Statnick, "Measurements of entrained liquid levels
in effluent gases from scrubber demisters," EPA Report No.
650/2-74-050, The Environmental Protection Agency, 1974.
17. D.P. Lucero, "VapaTrog: an isokinetic gas/mist sampler for the CAMDS
incinerator stack," Aerospace Report No. T0R-0083(3712)-2, August 1983.
18. R.W. Coutant, E.C. Penski, "Experimental evaluation of mass transfer
from sessile drops," IEC Fundamentals, 21: 250-254 (1982).
19. J.H. Perry, Chemical Engineers Handbook, 4th Edition. 1963, pp. 5-62.
20. R.D. McRanie, G.O. Layman, "Evaluation of sample conditions and
continuous stack monitors for the measurement of sulfur dioxide,
nitrogen oxides, and opacity in a flue from a coal-fired steam
generator," Southern Services, Inc., Technical Report, Birmingham,
Alabama. 1975.
21. J.H. Perry, Chemical Engineers Handbook, 4th Edition. 1963.
22. M.C. Miller, "Experimental aerodynamic facilities of the aerodynamics
research and concepts assistance section," ARCSL-SP-83007, Chemical
Systems Laboratory, U.S. Army Armament and Research Command, Aberdeen
Proving Ground, Maryland 21010.
23. W.M. Rohsenow, H.Y. Choi, Heat, Mass and Momentum Transfer,
Prentice-Hall, Inc. 1961, pp. 35-36, 72-75.
24. H. Schlichting, Boundary Layer Theory, 4th Edition, McGraw-Hill.
1952, pp. 168-17T.
25. R.C. Binder, Fluid Mechanics, Prent1ce-Hal1 Engineering Series, K.D.
Wood, Editor. 1946, pp. 133-5.
26. A.M. Kuethe, J.O. Schetzer, Foundations of Aerodynamics, John Wiley
and Sons, Inc. 1957, p. 188.
587
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Table 1. VapaTrog Aerodynamic Characteristics
The reduces ciata listed was obtained over 20'F to 48*F and 29.30- to 30.21-in. Hq ambient temperature and pressure conditions except for the 0.384-in.
inlet diameter data, which were taken at 74*F to 78*F amiient temperature. fill exit velocity data were corrected for pilnt-tutx.' blockage. The reduced
data listen oelow for the 0.384-in. inlet diameter were normalized Iron /u*F to 35°f ambient conditions per E.q. (4).
Values at Each Wind Tunnel Velocity (ft/sec)
Operating Para/neter 60 t>0 40 35 30 Notes
At. Inlet Uiaireter: 0.440 in.
isokinetic factor
Averaye isokinetic factor
Cxit centerline velocity (ft/sec)
txit average velocity (ft/sec)
Average velocity/tenter 11ne velocity ratio
txit total pressure at cencerline (in.
Exit static pressure at centerline (in. H?0)*
At Inlet 0 i aiiic.tcr~: U.423 in.
CJi isokinetic factor
5 Average isoKinetic factor
tne (in. H^U)*
At inlet Lia* ete°: 0.384 in.
isokinetic factor
Average isokinetic factor
Lxii. centerline velocity (ft/sec)
txit avsraye velocity (tt/sec)
Average velocity/center 1ine velocity ratio
txit toLal pressure at centerline (in. H2O)*
txit static pressure at centerline (in. H^O)*
0.U31
0.83£i
Q.C32
0.842
0.836
i,
0.U36
(- 0.D06,
-0.005)
b2.2
44.0
35.0
30.5
27.0
2.
40.9
34.4
27.3
2.1.2
20.3
0.7B6
0.781
0.77S
0.7S5
0.750
2.25
1.61
1.00
_
0.63
3.
1.97
1.35
O.SO
-
0.49
0.071
0.3E6
0.880
0.097
0.918
1
0.890
(* 0.028
-0.019)
S1.0
43.0
34. b
30.0
2b.0
36. b
33.6
26.7
23.8
20.6
2.
0.771
U.781
0. 774
0.792
0.792
2.25
1.56
0.97
-
0.63
1.9b
1.35
O.H4
-
0.47
3,
0. 'J06
0.923
0.'J2a
0.921
0.953
li
0.926
(* 0.020
-0.027)
48. b
41.5
34.0
31.0
27.5
3 /. ti
32.1
25.8
22.4
19.6
2
0.78
0.77
0.76
0.72
0.72
2.23
1.55
0.99
_
0.61
1.97
1.3b
0.85
-
0.47
3
o.y7
1.0!
1.02
1.05
1.08
1
1.03
(+ 0.0b,
-0.06)
43.0
38.0
33.0
30.5
27.5
34.0
30.2
24.5
21.5
19.5
2
0.80
0. 78
0.75
0.71
0. 71
(not measured)
(no: measured) 3.
k variance from average k +0.7 per cent, -0.6 per cent
Averaye/centerline velocity ratio variance *7.1
per cent, -3.6 per cent
k assumed to operate at 35*F
k variance from average k +3.2 per cert,
-2.1 per cent
Average/centerline velocity ratio variance + 1.3
per cent, -1.4 per cent
k assumed to operate at 35*F
k variance from average k, *2.7 per cent,
-2.9 per cent
Average/centerline velocity ratio variance +4.0
per cent
k assumed tc operate at 35°F
k variance frop average k, +4.9 per cent, -5.B
per cent
Average/centerline velocity ratio variance + 6.7
per cent, -6.3 per cent
V normalized to 35*F per tq. (4)
'The maximum variance ot exit total and static gauge pressure from the average at a given wind tunnel air velocity is + 2.8 per cent, -3.6 per cent.
-------
Table II. VapaTrog Mist Collection and Processing
Eq. (b) was used to calculate tne average mist loading with jr = 1.16 x 1C-3
g/in'i, o] - 1 a/mi, ano (W'h^oJo" 3 3.3 * 10"3. The air specific tumidity
was oefined from dry ana wet euls temperatures. A 0.384-in. diameter inlet was
used in these experiments.
Run Nunber
Parameter
I
2
3
kind tunnel air velocity (ft/sec)
3S.2
43.5
47.i
Mist loaclng measure.'nents
over at
iS
36
15
Nose cone average
temperature I *F J
14 7 to 109
160 to 130
16C to 130
(•list droplet average diameter ;asi)
36
35
39
Collection time—it (min)
27b
335
300
Bleeo flow race—Og (ml/.nin)
107C
i ISO
1110
Liquio water collected—Vj (ml)
5.4b
6.50
6.15
Air specific humidity—g
I
1.532 x 10-2
1.532 x 10-2
1.374 x 10-2
C&lculatea average mist
loading—*c
4,1 x IC"3
2.5 x 10-3
o.O x 10--*
.Measureo time weighted average
mist loaaing—
2.93 x 1CT3
2.25 x lO"3
4.07 x :0"3
Percent aiscreoancy between
w_ and »~
*39. 9
-11.4
*47.4
589
-------
Internal to Flue
External to Flue
Excess Processed Effluent
Bleed Stream
Returned to the Stack
Processed
Effluent Returned
Directly to the Flue
Stream
Processed Effluent
Bleed Stream
Flue Wall
Processed Effluent
Bleed Stream
to Analyzer
Flue Stream Effluent
(Gas/Mist) Flows
into the Probe
Sample Transport
Network and Processor
Effluent Probe
and
Sample Processor
Figure 1. Isokinetic gas/mist sampler.
590
-------
Processed Effluent Sample
Stream Returned to the Flue
Bleed Stream Probe
"V
Bleed Stream Heated
Line to Sample
Transport Network
and Processor
—D-
Heated/lnsulated
Tube
Effluent Sample
Stream
Flue Wall
Isokinetic Gas/Mist
Sampling at Entrance
Gas/Mist Effluent
Figure 2. VapaTrog (effluent probe and sample processor).
591
-------
VapaTrog Exit
Base Plate
Outer Tuba
Heated Tube
Insulation
Wrap-around
Heaters
Nose Cone
Heaters
Nose Cone
Nose Insert
VapaTrog Inlet
Figure 3. VapaTrog probe.
592
-------
2-
8
Dimensions: Inlet Diameter 0.405 in.
Operating Mode: 11) VapaTrog Controlled at 340 °F
12) Zero 3leed flow Rate
Nate; Velocity profile points interpolated
from data in Figure 0.
Wind Tunnel Stream Velocity
— 60 fT/s !©}
— 50 ft/s !xi
_ 40 fl/s <13
— 35 ft.s iA>
— 30 ft'S m
Radial Position
Figure 4. Effluent sample stream exit velocity profile.
593
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DEFINING AMBIENT IMPACT OF VOLATILE
ORGANIC COMPOUNDS EMITTED FROM AN
AUTOMOBILE ASSEMBLY FACILITY
i. — i
Peter t. Dahigren
General. Motors Corporation
Environmental Activities Staff
Warren, Michigan
General Motors (GM) organized a five-day analysis of ambient
concentrations of twenty-one volatile organic compounds near a high-
capacity automobile assembly facility applying low-solvent coatings. A
consultant was retained to perform on-site measurements using a mobile
TAGA® 6000 tar'aeni mass spectrometer. In addition to providing
quantitative results for twenty-one target compounds, all organic
materials were .ientified. Ambient air monitoring was conducted in the
late summer and early fall of 1985. GM received preliminary data in mid-
March, ^986. This paper describes project objectives, monitoring strategy
and data analysis techniques. Project results are not included, due to
the late arrival of preliminary data and the need for further analysis.
However, it was found that the minimum detection limit of the 7AGA® 6000,
as used in this study, was generally not low enough to enable a comparison
of ambient concentrations with fractional occupational limits. This
project was a first attempt at applying an emerging technology to better
understand the ambient impact of VCC's emitted from a large automobile
assembly plant applying low-solvent coatings.
594
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DEFINING AMBIENT IMPACT OF VOLATILE ORGANIC COMPOUNDS EMITTED FROM AN
AUTOMOBILE ASSEMBLY FACILITY
Introduction
Within the past five years, regulatory agencies and the general
public have shewn an increasing concern ever the industrial emission of
toxic air pollutants. This concern is evident by tne introduction of
bills to revise the Clean Air Act, articles in leading national newspapers
and numerous government research projects.'1 In addition, many state ana
local agencies either have developed, or are now developing, air toxics
regulatory programs apart from federal activities^. As such, General
Motors (GM) has intensified its long-standing efforts in evaluating and
reducing the impact of potentially hazardous sir pollutants resulting from
the operation of its products and facilities. GM has elected tc
participate in further analyses of potentially hazardous stationary source
emissions in order to 1) contribute in a positive fashion to the formation
of reasonacle and effective air toxics regulations, and 2) icent.fy and
correct as a responsible citizen any potential problems resulting from
current piant emissions.
In tnid-1984, GM decided to examine further the ancient impact of
specific volatile organic compounds (70C) emitted from an automobile
assembly center, as some of these compounds, such as toiuene. were, and
still are, under review as potentially harmful to humanso. Stringent
federal surface coating requirements designed to attain tne national
ambient air quality standard for ozone hava necessitated the use of low-
solvent coatings at most GM assembly centers. However, few comprehensive
studies have measured the ambient impact, of specific VGC's emitted from
facilities applying these coatings.
A reference facility for this ambient monitoring study was selected
based upon several factors. First, the surface coating operations had to
be representative of those in current and near-future GM vehicle assembly
centers. Second, no variances in production should be anticipated curing
the scheduled monitoring period. Next, the area surrounding the piant had
to contain numerous public streets to facilitate monitoring with the
proposed mobile analytical laboratory. Finally, some pnior measurements
of ambient VOC concentrations should be available from the site in order
to check project results. The selected facility, one of GM's highest
volume vehicle assembly operations, continues to be in compliance with all
applicable air pollution regulations.
Project Tasks
Six tasks were identified to guarantee that the project results would
satisfy the objectives of the Corporate air toxics strategy as described
above. These are:
1) Determine known hazardous, nigh-usage VOC's from production
operations; (These, arid other organ:cs selected by the consultant, would
be target compounds for which quantitative ambient results were desired.
This step was required to calibrate proposed mooile analytical equipment,
and for identification of production material constituents.)
595
-------
2) Measure ground level concentrations of all target compounds in
the community near the automobile assembly facility under various
meteoroi og i ca1 cond i t ions;
3) Identify all organic materials i n detected plumes;
(Quantification of these compounds could be performed in later studies.)
1) Calculate annualized concentrations for identified target
compounds using maximum short-term average levels and meteorological
scaling factors;
5) Compare annualized concentrations to fractions of occupational
threshold limit values and cancer assessment group values, and
6) Compare peak concentrations to documented threshold odor levels.
Selection of Target Compounds
Three criteria were evaluated in order to select target compounds for
this study: emission rate, priority ratio and expert opinion. A prior GM
study identified the usage of production materials containing VOC's. From
this internal study, and a thorough review of vendor supplied material
safety data sheets, it was possible to rank the know:-. VOC emitted by the
facility according to maximum potential emission rate. Next, a priority
ratio was developed for each compound by dividing the maximum potential
emission rate by its respective Threshold Limit Value (TLV) set by the
American Conference of Governmental Industrial Hygienists. This ratio
reflects both maximum potential emission rate and a degree of toxicity. A
high priority-ratio qualified the compound for further review. If no TLV
existed for a compound, then an arbitrary high value was assigned in order
to calculate that specific compound's priority ratio. Typically, this
high TLV value created a low priority ratio. This practice was deemed
justifiable, in the absence of a better method, because it was felt that
if the compound was a widely used toxic material, then it would likely
have an assigned TLV. The last criteria used in selecting target
compounds was the advice of Dr. Pat Beattie of (i.M Toxic Materials Control
Activity, and Dr. Kay Jones of Roy F. Weston, Inc.. These individuals
recommended additional compounds on the basis of other air toxics studies
and the unique compound identification characteristics of the proposed
mobile analytical equipment. Table I identifies the selected target
compounds.
Mobile Analytical Laboratory
Roy F. Weston, Inc. and their subcontractor Vork Research
Consultants, Inc. were retained to conduct the ambient monitoring. The
monitoring equipment consisted of a TAGA® 6000 tandem mass spectrometer
(MS/MS) mounted in a 33-foot modified Bluebird motorhome. The TAGA® 6000
system has the ability to analyze complex gaseous mixtures for individual
components without prior entrapment of sample. This feature enabled the
mobile analytical laboratory to conduct real-time monitoring over a large
geographic region near the plant. Further, the mobile analytical
laboratory was able to locate plume center Iines qir.ckly and obtain maximum
time-averaged concentrations of detected target compounds.
The existing conventional methodologies for the detection of low levels of
organics in ambient air require that the compounds be adsorbed onto a
596
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substrate over a finite period cf time. The substrate is then taken for
analysis in an off-site laboratory, where the compounds are either-
thermal iy desorbed or solvent eluted from the substrate and analyzed by GO
or GC/MS. The conventional monitoring techniques suffer from several
drawbacks. Extensive sampling using a network of ironizcring locations is
necessary to quantify maximum ambient levels of organic compounds.
Results are obtained several days or weeks after the sampling is
performed. Also, temporary fluctuations cannot be identified, as the
results are always time-averaged over the duration of tne sampling period.
Uncertainties are also introduced in the desorptior. process.** These
difficulties are minimized or eliminated by employing a mobile tandem mass
spectrometer.
Tandem mass spectrometry emerged as an analytical tool in tne early 1980's
and several reports are available which descrioe the system and its
development.5 Whi.e the intent of this paper is to discuss the ambient
monitoring strategy, it is important to note some of ;he 1 imitations of
the TAGA® 6000 system in this application. Interferences are possible in
tne measurement of some target compounds. For example, except tnrough
detailed study of the mass spectra, ethyibennene cannot be cistir.gjished
from the xylenes. Likewise, methylene chloride cannot be distinguished
from chloroform, and the aliphacies hexane and r.opcar.e cannot be
distinguished from the corresponding olefins hexene ana heptene.- Also,
the detection limit of the TAGA6 6000 as usee for this project kas net as
low as other methods currently accepted by the Environmental Protection
Agency, such as tne volatile organic sampling train (VCST).? Manual
sampling techniques can achieve lower detection limits by increasing
sampling tiir.e, while the minimum detection limit cf tne TAGAj£ 6000 is
defined as three standard deviations above instrument noise.
Monitoring Procedures
Based on estimated project costs and the consultant's assurance that
meaningful results could be obtained from five days of testing, the
ambient monitoring was scheduled for August 29-30 and September <»-c, "935.
Nearly all monitoring was conducted during the hours ir. which the plant
was operating at full capacity. During the first three days and the fifth
day monitoring was conducted between the hours of 7:00 A.M. and 4:00 P.M.
corresponding to first shift production operations. Cn the fourth cay
monitoring was initiated at 3:00 A.M. in effort to assess the ambient
impact of methylene chloride ana other organic compounds emitted from
paintshop maintenance activities performed during the early morning hours.
Sampling was conducted both upwind and downwind of the assembly
facility. One of the first operations performed each day was an upwind
background scan. Background scans were conducted upwind of the facility
in various rural locations, and the corresponding spectra were stored
onboard electronically. Later, the background spectra were subtracted
from the downwind spectra in order to identify unique components or those
compounds present in higher concentrations than background levels.
The TAGA® 6000 was calibrated for each target compound at tne
beginning and end of each monitoring day using pure laboratory standards
kept in the liquid pnase in an onboard freezer. A known mass of the
standard was injected at a precise rate incc the constant flow of the
ambient sampling stream. Calibration curves were generated by noting the
corresponding rise ir. signal intensity from the known concentration of
introduced sample.
597
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The TAfifl® 6000 was utilized for bolh mobile arid stationary
monitoring. Wind conditions dictated the major quadrant around the
facility in which the mobile laboratory would begin monitoring. Wind
.speed, wind direction and other meteorological cata were continuously
collected at an on-site station. The mobile mode of operation was used
first to locate specific geographic areas having the highest
concentrations of target compounds. Later, the mobile laboratory was
parked in these areas, and operated in the stationary mode. Sensitive
receptors, such as schools and hospitals, were given priority as
monitoring sites. While operating the TAGA® 6000 system in the stationary
mode, fluctuations in plume concentration at individual locations were
recorded. After examining these fluctuations over a ten minute interval,
time-weighted average concentrations were calculated. The spectra from
twenty-two mobile and twenty-one stationary runs was analyzed.
Data Analysis
The specific techniques used in the analysis of the raw data are
critical to obtain meaningful project results. Time-weighted average
concentrations can be calculated in several different ways and for varying
periods of time. Use of different techniques and averaging periods may
yield significantly different project results. For this analysis, ten-
minute average concentrations of target compounds were calculated using
recognized integration techniques.8 A standard time-frame of ten minutes
was selected, because this was typically the longest period for which
conclusive measurements were recorded repeatedly over the five-day
monitoring period. However, these ten-minute maximum concentrations do
not accurately represent average maximum levels in the community over the
course of a year. The maximum ten-minute concentrations were annualized
using conservative scaling factors developed from EPA guidelines.9 These
annualized concentrations will be compared with acceptable ambient levels.
Instantaneous peak levels of target compounds are relevant only in
comparison to documented threshold odor concentrations.
A number of states and localities derive acceptable ambient
concentrations for certain compounds by applying a safety factor to the
corresponding occupational TLV. The most stringent, safety factor in use
in the United States applicable to most compounds is 1/120.10 Annualized
concentrations of target compounds will be compared to recommended levels
calculated with this stringent safety factor. However, as shown in Table
II, the minimum detection limits reported for many compounds during
portions of this study were not low enough to permit a comparison of
pi'oject results with fractional occupational limits.
Conclusions
The mobile, real-time analysis capabilities of the TAGA® 6000
permitted plume tracking and location of sites experiencing maximum
ambient levels of detected target compounds. However', the minimum
detection limit of the TAGA® 6000, as used in this study, was generally
not low enough to enable a comparison of ambient concentrations with
acceptable community health levels.
598
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References
la. H. Waxman, T. Wirth and J. Florio, "The Toxic Release Control Act
of 1985", H.R. 2576, (1985).
lb. S. Diamond, "Problem of Toxic Emissions", New York Times. 20 May
1985, See. D, p.1,5.
1c. R. Mead, C. Benton and A. Pelland, "Air Toxics Information Clear-
inghouse: Ongoing Research and Regulatory Development
Projects",Radian Corp., EPA Contract 463-02-3889", WA 16, ( 1985).
2. S. Smith, "Air Toxics Information Clearinghouse: Second Interim
Report of Selected Information on State and Local Agency Air Toxics
Activities", Radian Corp., EPA Contract #68-02-3889. WA 15, (1985).
3- A. Feiiand, B. Post and R. Meac, "Air Toxics Information Clearing-
house : Bibiiograpny of Health Effects/Risk Assessment Information",
Raciar. Corp., EPA Contract #68-02-3513, WA 52, ( 1984).
h. D. Een-Kur, "Ambient Air Toxics Characterization Study", R. F.
Westcn, Inc., West Chester, PA, W.Q. 1138-30-01. (1986).
5. J. Zoldak, B. Duirdei, "Characterization of Toxic Air Emissions From
T3DF'5 in Heavily Industrialized Areas Using a Mobile MS/MS Labor-
atory", TRC Advanced Analytics, Inc., paper 85-17.3, presented at
78th Annual APCA Meeting, •1985).
6. Bsn-Hur.
7. D. Schraid, J. Osborne, "VOST vs. MS/MS—A Case Study", 3M Corp.,
paper 85-65.3, presented at 78th Annual APCA Meeting, (1935).
8. Ber.-Hur.
9. R. Ruc'n, R. F. Weston, Inc., interpretation of "Guidelines for Air
Quality Maintenance Planning and Analysis Volume 10 (Revised):
Procedures for Evaluating Air Quality Impact of New Stationary
Sources", EPA-450/4-77-00! (0AQPS NO. 1.2-029 R), p. U-21, (1977).
10. Smith.
599
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Table I. Selected Target Compounds
1)
acetone
2)
1,3-butadiene
3)
r.-butanol
*)
n-butyl acetate
5)
epichlorohydr in
6)
2-ethoxyethanoi
7)
2-ethoxyethylacetate
3)
ethyl acetate
9)
heptar.e
10)
hexane
11)
isobutyi alcohol
12)
methylene chloride
13)
methyl ethyl ketone (ME!K)
14)
methyl isobutyi ketone (MIBK)
lb)
2-propano i
16)
styrene
17)
toluene
18)
tetrachlorethylene
19)
1,1,1-triehloroethane
20)
vinyl chloride
21)
xylene (o,m,p)
Table II. Range of TAGA® Detection Limits During Study
vs. TLV/420
Target
Range of TAtJA® 6000
TLV/420
Compound
Detection Limits (ppb)
(ppb)
1
acetone
58-630
1,786
2
1,3-butadiene
11-120
24
3
n-butanol
38-1,100
119
i!
n-bntyl acetate
140-9,500
357
5
epichlorohydrin
5-69
5
6
2-ethoxyethano1
not determined
12
7
2-ethoxyethy '.acetate
not determined
12
8
ethyl acetate
78-3,000
952
9
heptane
54-2,900
952
10
hexane
540-25,000
119
1 1
isotutyl alcohol
not determined
119
12
methylene chloride
1,400-4,800
238
13
methyl ethyl ketone
34-630
476
14
methyl isobutyi ketone 6-76
119
15
2-propanol
not determined
476
16
styrene
360-3,400
119
17
toluene
28-1,900
238
18
tetrachloroeth.y 1 ene
340-3,300
119
19
1,1,1-trichloroethane
38-2,800
833
20
vinyl chloride
25
12
21
xylene (o,m,p)
5-79
238
600
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QUALITY ASSURANCE FOR NON-ROUTINE AIR MEASUREMENT PROGRAMS: EPA' s
EXPERIENCE WITH THE NATIONAL DIOXIN STUDY
Richard V. Crume3
Research Triangle Institute
Research Triangle Park, North Carolina
Michael A. Palazzolo
Radian Corporation
Research Triangle Park, North Carolina
William B. Kuykendal
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina
William H. Lamason
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina
ABSTRACT
In recent years, air measurement programs have become more and more
sophisticated. For example, today it is not unusual for an industrial
process emissions research program to require the use of a variety of stack
and ambient air sampling trains and continuous emission monitors, the
collection of numerous process and soil samples, the recording of voluminous
amounts of process operating data, and the use of several complex analytical
techniques, including gas chromatography/mass spectroscopy. As interest
develops in the measurement of air toxics, air measurement programs have
become further complicated by the use of non-routine methods. The net
result of these complexities is often confusion over the appropriate use of
equipment and procedures, resulting in the generation of pogr, or at least
unknown, data quality. A few organizations, including the U.S. Environ-
mental Protection Agency (EPA), have addressed these problems through the
implementation of a quality assurance strategy as part of the overall test
plan. EPA's experience in implementing a quality assurance program for Tier
k (Combustion Sources) of the National Dioxin Study is discussed. The study
involved the measurement of dioxin (2,3,7,fi-TCDD) and dioxin precursors
(i.e., chlorophenols and chlorobenzenes) at thirteen emission sources, and
analyses associated with these measurements. Lessons learned from the study
and recommendations for the designers of future air toxics measurement
programs are presented.
a Now with the Department of Marine, Earth, and Atmospheric Sciences,
North Carolina State University, Raleigh, North Carolina.
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In troduc tlon
During the past several years an increasing need for quality assurance
(QA) in environmental test programs involving air measurements lias become
evident. This need has resulted largely from the substantial number of
measurements now made in many test programs, the use of contractors and
subcontractors who are inexperienced with new and non-routine test methods,
and the increasing necessity to defend test results before industry and the
public, sometimes in litigation. Recently, as Interest has developed in the
measurement of toxic air pollutants, the need for QA has become even more
important. This is due to; (1) the high costs associated with many air
toxics measurement programs; (2) the complexity of the measurement and
analytical methods; and (3) the importance of these measurements in estab-
lishing a potential health risk to the public. Unfortunately, as QA has
become more important, it has also become more challenging to effectively
i mplemen t.
QA, which Involves a series of independent checks of test program
procedures and documentation, is intended to help:
o Define the quality of data produced by the test program; and
o Assure that the quality of data produced is adequate to achieve
the objectives of the test program.
The experience of the U.S. Environmental Protection Agency (EPA) in imple-
menting a QA program for Tier 4 (Combustion Sources) of the National Dioxln
Study is presented here. Since similar large-scale sampling and analysis
programs Involving toxic air pollutants will be performed in the future, it
is hoped that EPA' s Tier 4 experience will be useful to future investigators
in planning their air toxics measurement programs.
Background
In 19B4 EPA implemented a national strategy to study the nature and
extent of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) contamination
in the environment. The strategy, known as the National Dioxin Study,
established seven categories (or Tiers) of Investigation, ranging from the
most probable contamination to the least. The category dealing with air
emission sources, Tier U, was defined as:
o Combustion sources such as the Incineration of hazardous and
municipal wastes, internal combustion engines, wood-burning stoves,
and others.
The responsibility for investigating Tier 4 sources was assigned to the Air
Management Technology Branch (AMTB) of EPA's Office of Air Quality Planning
and Standards. AMTB's contractor for the Tier 4 sampling and analytical
support activities was Radian Corporation of Research Triangle Park, North
Carolina. Additionally, EPA's Troika Laboratories (i.e., the three dioxin
analytical facilities at Research Triangle Park, North Carolina; Bay St.
Louis, Mississippi; and Duluth, Minnesota) performed all of the analyses for
chlorinated dioxins and furans. The Tier k activities performed by these
two organizations, including the sampling and analytical techniques U3ed,
are summarized In Table I. A total of thirteen emission sources were
investigated during the study.
QA support for the study was provided by Research Triangle Institute
602
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(RTI) of Research Triangle Park, North Carolina. RTl's responsibility was
to independently evaluate the test procedures used in the study and to
report its evaluation, with any recommendations, to AMTB. This effort
resulted in three separate on-site evaluations of the test systems in use in
the field, nineteen performance audits of the measurement and analytical
equipment, eight reviews of various reports and documents, and a final
report.'- RTl's cost in performing these duties was approximately four
percent of the total Tier 4 budget. Although AMTB personnel played a role
in determining which tests, equipment, and documents should be evaluated,
these individuals remained independent of the conclusions and recommenda-
tions presented by RTI.
In addition to RTl's QA support program, several other organizations
also performed independent QA evaluations. For example, both Radian
Corporation and the Troika Laboratories had their own QA and quality control
(QC) programs in effect.^>3 Additionally, EPA had its own observers present
during all stack tests.
Elements of the QA Program
The Tier 4 QA program can be divided into three categories: QA
Management, Internal QA/QC Operations, and External QA Evaluations. The
first category, QA Management, consists of the set of requirements and
procedures specified by EPA management. The second category, Internal QA/QC
Operations, covers the responsibilities of Radian Corporation. The final
category, External QA Evaluations, involves the audit and review activities
performed primarily by RTI. Although the Troika Laboratories' internal
QA/QC program is not discussed here, these Laboratories were evaluated as
part of RTl's QA effort.
QA Management
As noted earlier, EPA's AMTB had overall responsibility for the Tier 4
study, including QA management. QA was recognized early in the program
planning stage as a key factor in determining the overall success of the
study. Therefore, it was determined that a ieu 1 ti face ted QA effort would be
needed. The major program components that affected data quality were
identified as the sampling activity conducted by Radian and the analytical
activity which was the responsibility of EPA's Troika Laboratories. Both of
these functions would have their own internal QC. Additionally, it was
decided to have RTI, a completely independent QA contractor, provide an
independent and unbiased assessment of the data quality generated under the
s tudy.
In addition to the QA contractor's oversight role, an on-site EPA
representative was present at each source test site as a test observer. The
EPA on-site observer was familiar with the sampling protocols and provided
additional QA verification that field operations had followed the estab-
lished protocols.
Major emphasis under the QA portion of this study was placed on the
sampling activity. The primary reason for this emphasis was that Troika
represented established laboratories which had considerable experience in
the analysis of chlorinated dibenzo-p-dioxins (CDDs) and chlorinated
dibenzofurans (CDFs), and which already had rigorous QA programs in place.
In contrast, the sampling activity had to develop its own written sampling
procedures, prepare a detailed QA Project Plan (QAPP), and refine these
603
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procedures through experience gained in the field. Thus, greater QA empha-
sis was placed on the field sample phase of the study.
Data quality objectives can be established In one of two ways. One
means of establishing these objectives involves an analysis of the
parameters to be measured, an assessment of the allowable uncertainties in
measuring these parameters, and the selection of appropriate methods to
measure these parameters, based upon the established measurement criteria.
The task of QA then becomes one of determining whether or not the data
generated satisfies the specified quality objectives. The second approach
to setting data quality objectives, and the one used in this study, involves
the specification of a particular sampling and analytical methodology. Once
the methodology has been specified, the task of QA is to determine whether
the methodology was properly followed. Under this study, state-of-the-art
methods were specified for both sampling and analysis to obtain results that
deliver the highest level of data quality possible.
The remaining QA management functions were operational In nature. It
was necessary to maintain an oversight responsibility to ensure that the
various elements of the QA program functioned properly and were properly
coordinated. For example, It was important to schedule a QA field audit of
Radian's stack sampling program early in the study. Thus, if difficulties
were identified, there would be ample time remaining in the program to
implement corrective action. Also, future QA field audits could verify that
proper corrective action had been taken.
Perhaps the most significant QA management responsibility involved the
decision of how to resolve problems that affect data quality after the QA
program has identified them. Each situation is unique. Two examples from
this study will serve as illustrations. In the first example, the QA
contractor, RTI, Identified a problem In Radian's laboratory method for the
analysis of low levels of chlorine In fuel oil audit samples. The problem
was identified as an inappropriate analytical methodology for low level
chlorine analysis. Radian elected to subcontract this analysis to another
laboratory that had experience in analyzing these types of samples. In this
example, the problem was Identified, a remedy implemented; and all data
reported achieved satisfactory data quality.
In the second example, the EPA Troika Laboratories' internal QA program
Identified a data set that did not meet their own internal data quality
objectives. The QA management decision in tills case was to report the data
(even though data quality objectives were not satisfied), but to clearly
identify In the report that this was tin: case. The reader of the report was
cautioned that these data did not satisfy QA criteria and should be regarded
as estimated values.
Internal QA/QC Operations
Radian's QA activities for the Tier 4 study centered around the
preparation and Implementation of a sound and comprehensive Quality
Assurance Project Plan (QAPP). The need for good planning cannot be
overemphasized with regard to assuring high quality data from any field
sampling effort. In preparing the QAPP, special attention was given to the
samplLng effort and the need for this plan to be a working or reference
document for field sampling personnel. The plan, therefore, provided
specific details on the sampling, analysis, calibration, data reduction, and
QA reporting activities to be conducted under the Tier 4 program. The
604
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process of specifying these details led to invaluable communications between
the technical and QA project teams within Radian, EPA, and RTI. Ultimately,
a sound and comprehensive plan acceptable to all parties was developed. The
QAPP, being a working document, was later modified as certain procedures
were refined through experience gained in the field.
The QA/QC planning efforts for Tier k were supplemented by the prepa-
ration of site-specific test plans for each of the thirteen test sites.
These plans provided details to the technical and QA project teams on the
particular combustion process, the number and types of samples to be
collected, and any special QA/QC considerations to be noted.
The Tier A QAPP emphasized: (1) adherence to prescribed sampling/
analytical procedures; (2) careful documentation of sample collection and
field analytical data; and (3) internal (but independent) systems ana
performance audits similar to those conducted by RTI. Standard QC proce-
dures, such as equipment calibrations, leak checks, etc., were implemented
for each of the sampling/analytical methods. Additional QC measures
implemented to further ensure valid data and/or to provide a measure of da ta
quality are summarized below.
Modified Method 3 (Dioxins). Extensive glassware pre-cleaning proce-
dures and blank sample train collections were implemented for the Modified
Method 5 sampling effort. The purpose of the pre-cleaning procedure was to
minimize the potential for sanpie contamination with substances that may
interfere with the dioxin analysis. Flue gas dioxin concentrations at the
part-per-tri1lion level were targeted for the method.
Two types of sample train blanks were collected. One of the blanks
(called a proof blank) was collected from a set of unused, pre-cieaned
glassware to verify that the cleaning procedure was effective. The second
blank was a site-specific sample train field blank. The field blank was
obtained using a train that had previously been used to collect at least one
actual sample from the test site. The field blank provided data on the
effectiveness of the sample recovery procedures.
Continuous Monitoring. Specific acceptance criteria for continuous
monitor calibrations were set forth in the QAPP to provide field personnel
with a basis for accepting or rejecting calibration curves. All data,
including calibration results, were collected and recorded using a micro-
processor-based data acquisition system, thereby reducing the potential for
errors from manual data reduction. Daily drift checks and QC gas analyses
were also performed to provide a measure of data quality and to identify the
need for instrument maintenance.
Process Sample Collection. The types of process samples collected for
Tier h varied widely from liquids/slurries (e.g., scrubber blowdown and fuel
oils) to sluages/so1ids (e.g., sewage sludge and wood chips). Methods used
to sample these materials were detailed in the si te-spec i F ic test plans and
agreed to by all team members before testing was performed. Whenever
feasible, these samples were collected from a moving stream as close as
possible to the equipment being sampled. Duplicates for the process samples
were analyzed to assess sampling/analytical precision.
Sample Custody. Since samples collected during the Tier k study were
analyzed in several different laboratories, sample custody and handling was
an important part of the field sampling effort. Key elements of the sample
custody and handling procedures included the following:
60S
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~ Preformatted data sheets for a 1L sampling efforts.
o An Informal dally log to document events.
o A unique alphanumeric Identification number for samples from all
si tes.
o A "master" logbook to document all samples collected,
o Labels, custody seals, and chain-of-custody forms specific to
Tier A.
o Sample shipment letters prepared prior to leaving for the field.
o Packing and shipping procedures that minimized sample loss due to
spillage or breakage.
Laboratory Analyses. Procedures for laboratory QA/QC consisted of
laboratory blanks and duplicate analyses. In addition, blind audit samples
were submitted to the laboratories to assess analytical accuracy,
External QA Evaluations
RTI's QA activities took the form of technical systems audits, per-
formance evaluation audits, and documentation reviews. A technical systems
audit is a qualitative, on-site evaluation of a measurement system. The
objective of the technical systems audit is to assess and document the use
of all:
o Test facilities and equipment.
o Recordkeeping and data validation procedures.
o Equipment operation, maintenance, and calibration procedures.
o Reporting requirements.
o QC operations.
In contrast to the technical systems audit, a performance evaluation audit
involves a quantitative evaluation of the measurement system. Ordinarily,
this type of evaluation requires the measurement or analysis of a certified
or verified reference material having associated with it a known value or
composition. The third RTI QA activity, documentation review, is simply the
evaluation of pertinent test documentation (usually QA or teat plans)
against a standardized set of QA criteria. Each of RTI's QA activities are
described in more detail below.
Technical systems audita were performed at three test sites. In
preparing for these audits, RTI compiled a series of checklists covering
every significant operation, calibration, and adjustment associated with
each critical measurement. (The critical measurements included operation of
the inlet, outlet, blank, and ambient Modified Method 5 sampling trains;
operation of the HC1 sampling train and continuous emission monitors; the
collection of process samples; sample handling, transportation, and storage;
and the collecton of soil samples.) Similar checklists were also prepared
for Radian's laboratory operations. The questions contained on the check-
606
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lists were based on a review of all applicable test methods and on the
auditors' experience with those methods. The advantages of using checklists
to perforin technical systems audits are that they: (1) help guide the
auditors in identifying what aspects of the testing to focus on; (2) help
assure objectivity and completeness in the selection of questions to be
asked on-site; and (3) provide thorough documentation of all critical test
procedures and operations.
It was not practical to attempt to complete the entire series of
checklists (i.e., eight checklists containing a total of 202 questions)
during each of the three technical systems audits. Instead, the complete
set was used only during the first audit, and abbreviated forms were used
thereafter. (The abbreviated forms focused on recommendations made by RTI
as a result of the first audit.) For each audit, the use of checklists was
augmented with visual observations of critical test procedures and discus-
sions with the test team le.ders.
In preparing materials for use in RTl's performance evaluation audits,
RTI followed, where appropriate and feasible, these procedures: (1) the
most critical measurements and analyses were evaluated; (2) blind samples
were submitted (i.e., samples indistinguishable from actual field samples);
(3) the audit sample concentrations were certified or verified; (4) a por-
tion of each sample was stored at RTI in case the integrity of the audit
sample should be called into question at a later date; (5) the audit samples
covered the range of concentrations expected to be encountered in the test
program; (6) duplicate audit samples were submitted to check analytical
precision; (7) the audit sample matrices were selected to be the same as or
similar to those encountered in the field; and (8) the samples were sub-
mitted early enough in the test program to allow for procedural changes to
be made without seriously compromising final results.
RTl's performance evaluation audits of analyses performed by Radian
examined the following systems:
o Analysis of chlorine in fuel oil
These analyses were evaluated by submitting to Radian a set of four
(and later a second set of two) Number 2 fuel oil samples that had
been spiked with methylene chloride. The concentrations of the
spiked samples were verified at RTI using the same method later used
by Radian.
o Analysis of HC1 train Implnger water
These analyses were evaluated by submitting to Radian a set oc two
impinger water samples taken during a earlier test program. The
concentrations of the samples were verified by RTI before analysis
by Ra d i a n .
o Dry gas meter calibrations
The calibrations of the sampling train dry gas meters were evaluated
using a calibrated orifice supplied and certified by EFA.^
o Computerized calculations
Radian used a computer to perform routine data calculations asso-
ciated with operation of the sampling trains. This system was
607
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evaluated by providing for input to the computer a set of hypo-
thetical data for which the expected calculated results were known
only to RTI,
The analysis of 2,3,7,8-TCDD by the Troika Laboratories was evaluated by
submitting the following samples obtained from the National Bureau of
Standards (NBS):
0 NBS Urban Particulate (SRM 1648) and Urban Dust (SRM 1649)
The concentrations of 2,3,7,8-TCDD in these samples had been
verified earlier by DOW Chemical.
o KBS Dioxln In Isooctane (SRM 1614), Two Samples
These were preliminary samples made available to RTI by NBS. (This
audit material has since been made available to the public. ?)
RTl's original intention was to prepare its own 2,3,7,8-TCDD audit materials
and submit them as blind samples to Troika. However, when the costs associ-
ated with the preparation of these samples in a toxicological laboratory and
the verification of the samples using sophisticated HRGC/HRMS techniques
were considered, a decision was made to use an alternative approach. (The
health risks associated with the preparation of the samples were also a
factor in this decision.) The alternative approach was to submit directly
to Troika, without modification, the NBS samples. The disadvantages of this
approach are that: (1) the samples would not be blind j (2) Troika may have
been able to guess the concentrations due to previous experience with
similar samples (although the isooctane samples were not formally available
to the public at that time, and Troika would not have known whether the dust
samples had been spiked by RTI); and (3) the sample media were not the same
as experience by the field samples (i.e. , XAD-2 resin). Despite these
shortcomings, it is believed that the Troika Laboratories made a good faith
effort to analyze the samples without bias.
The third aspect of RTl's audit activities involved the review of
documentation, primarily Radian's QAPP and several site-specific test plans.
This review process was guided by the set of QA criteria specified in tPA's
"Interim Guidelines and Specifications for Preparing Quality Assurance
Project Plans" (QAHS-005/B0), and by the experience of the auditors with the
methods being evaluated. The QAMS-0Q5/80 criteria are listed in Table 2.®
Assessment of the Tier 4 Program
Although data analysis will continue, It appears that the Tier 4
sampling effort was quite successful. Data quality objectives were gener-
ally achieved, sampling and analytical requirements were fulfilled, and
little data were lost. Only a few test runs had to be repeated due to
technical or procedural problems (e.g., a filter mounted backwards), and 8o
series of testsonducted at a specific site had to be repeated due to
deviations from program procedures. Thus, when judged by the quality of
data produced, it appears that the QA/QC program was a success.
One outcome of the Tier 4 program was evidence, based on the use of
audit samples, that the sampling and analytical procedures were performed
608
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correctly. For example, the analytical results for 2,3,7,8-TCDD compared
favorably to the expected results, as indicated below:
Sample Expected Reported
Descrlp tion Value Value^
SRM 1648 0.047 ppb 0.07 ppb
SRM 1649 0.0067 ppb Not Detected
(C.L. = 0.04 ppb)
SRM 1614 (i>l) 98.3 ppb 99 ppb
SRM 1614 (#2) 98.3 ppb 100 ppb
In the only case where audit results were not achieving data quality objec-
tives (i.e., the chlorine-in-fue1-oi1 analyses), the early use of audit
samples allowed the implementation of an acceptable method without loss of
da ta .
As discussed earlier, QC was also essential in producing the desired
quality of data. In one case, the cleanup and analysis of a blank Modified
Method 5 sampling train revealed that significant dioxin contamination had
occurred. Apparently, the sampling glassware, which had been used earlier
in the test program, had not been completely cleaned by the hexane and
acetone rinses in use. Reasoning that dioxins were more soluble in
methylene chloride than in hexane or acetone, a decision was made to switch
to methylene chloride rinses for the dioxin sampling trains.^® This
decision was made early enough to avoid significant loss of data.
Despite the apparent success of the Tier 4 sampling program, there were
several QA activities that couLd have been improved. For example, it would
have been useful to provide more audit samples, such that the systems under
evaluation could have been audited periodically throughout the entire study.
Another area for improvement concerns the preparation of audit samples for
the Z,3,7,8-TCDD analyses. Samples which were truly blank and which were
prepared in a matrix similar to that of the field samples would have been
preferable. Finally, it would have been useful to perform technical systems
audits of every field sampling operation rather than the three of a possible
thirteen actually evaluated. Nevertheless, given the cost and tine con-
straints inherent in the study, we believe that the design of the QA program
was appropriate.
Recommendations for Future Air Toxics Measurement Programs
It has been our experience that when sophisticated or non-routine
sampling and analytical procedures are part of any air pollution study, the
implementation of a well-planned QA program is essential. Such programs
usually pay for themselves in reduced re-testing and loss of data, and
provide thorough documentation for the quality of data produced. It is not
unreasonable for up to twenty percent of the entire budget of an air
pollution study to be devoted to QA.
A number of QA procedures which we have found useful in designing air
609
-------
pollution studies, including the Tier 4 study, are listed below:
o Establish a budget for quality assurance from the very beginning of
the test program.
o Develop the QA plan and test plan simultaneously.
o Define a QA official who is not part of the test team and who
reports directly to management.
o Use the QA plan to establish data quality objectives as well as to
anticipate and plan for any unexpected problems or delays.
o Be sure to allow sufficient tirue for laboratory work, especially
where non-routine methods are in use or where difficult sample
matrices are to be handled.
o Include the periodic use of audit materials for all critical.
measurements. Where materials to assess accuracy are not available,
provide for a thorough technical systems audit of the system.
o Make liberal use of blanks (including blank trains) as well as
duplicate and replicate analyses.
o Sample identification and tracking is very important. Hake use of
field, transportation, and laboratory custody sheets und log books.
o Consider performing an audit of data quality (i.e., an assessment of
all data transfer and reduction steps) for studies generating large
amounts of data.
o Do not overlook the importance of documentation for procedures used
and conditions encountered during the study.
S u mma ry
If Judged by the quality of data produced, the Tier 4 QA program was
successful. Not only were all procedures and conditions thoroughly docu-
mented, but also several potential problem areas were detected and corrected
early enough in the test program to prevent serious loss of data. Addition-
ally, the performance of each critical measurement system was assessed in
terms of precision and accuracy. During future studies, QA could be
Improved by Increasing the number of audit samples employed, providing more
realistic 2,3,7,8-TCDD audit samples, and increasing the number of technical
systems audits of field sampling operations. Nevertheless, despite the time
and cost constraints inherent in the study, the QA program was efficient and
cos t-ef f ec ti vre .
References
1, R.V. Crume, "National Dioxin Study Tier 4 -- Combustion Sources,
Quality Assurance Evaluation," EPA-450/4-84-014f, U.S. Environ-
mental Protection Agency, Research Triangle Park, North Carolina.
January 1986.
610
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2. M.A. Palazzolo, R.F. Jongleux, L.E. Keller, ana J. Bursey,
"National Dioxin Study, Tier 4 -- Combustion Sources, Quality
Assurance Project Plan," Radian Corporation, Research Triangle
Park, North Carolina. March 5, 1985
3. U.S. Environmental Protection Agency, "Analytical Procedures and
Quality Assurance Plan for the Analysis of 2,3,7,8-TCDD in Tier 3-7
Samples of the U.S. Environmental Protection Agency National Dioxin
Study," EPA 600/3-65-019, U.S. Environmental Protection Agency,
Environmental Research Laboratory, Duluth, Minnesota. April 1985.
4. R.T. Shegehara and C.3. Sorrell, "Using Critical Orifices as Method
5 Calibration Standards," Newsletter of the Source Evaluation
Society, Research Triangle Park, North Carolina. August 1985
5. T.J. Nestrick, L.L. Laciparski, and W.B. Crummett, "Proposed
Adoption of National Bureau of Standards SRMS #1648 and #1649 as
'Reference Particulate Matrices' for Analytical Methodology Quality
Assurance in CDDs/CDFs Determination," presented before the
Division of Analytical Chemistry, American Chemical Society,
Washington, D.C. August 29, 1983.
6. L.L. Lamparski and T.J. Nestrick, "Determination of Tetra-, Hexa-,
Hepta-, and Octachlorodibenzo-p-dioxin Isomers in Particulate Sara-
pies at Parts-per-Trii1ion Levels," Anal chera, 52, 1980 (2040-2054).
7. National Bureau of Standards, "Standard Reference Material 1614:
Dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin) in Isooctane," N33
Standard Reference Material (Factsheet), Ga i the rsbu rg, Marylana.
June 1985.
8. U.S. Environmental Protection Agency, "Interim Guidelines and
Specifications for Preparing Quality Assurance Project Plans,"
QAMS-005/80, Washington, D.C. December 29, 1980.
9. R.L. Harless, "Analysis for CCDs and CDFs in Extracts of Stack Gas
Sampling Trains and Dust/Ash Samples," Memorandum, U.S. Environ-
mental Protection Agency, Research Triangle Park, North Carolina.
November 8, 1985.
10. W.B. Kuykendal, "Change in Sample Recovery Reagents for Modified
Method 5 Sampling on Tier 4 Sites," Memorandum, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina.
February 27, 1985.
611
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TABLE 1. TIER U ACTIVITIES PERFORMED BY
RADIAN CORPORATION AND THE TROIKA LABORATORIES
Ac tivity
Procedure
RADIAN CORPORATION
I. Stack Gaa Sampling
o Dioxins and Precursors
o HC1
o CO, C02, 02, NOx, S02, THC
II, Ambient Air Sampling
o Dioxins and Precursors
III. Collection of Process
Samples and Data
o Feed Materials and
Supplementary Fuels
o Ashes, Liquors, and
Other By-Products
o Process Data
IV. Soil Sampling
o Dioxins and Precursors
V. Analyses
Dioxin Precursors
(i.e., Chlorophenols and
Chlorobenzenes)
HC1
Chlorine-in-Fue1 Oil
Modified Method 5 (MM5) Sampling
Tra i n
HCI Train (Modified Method 5)
Continuous Emission Monitoring
Sys tern
Ambient XAD Train
Grab Samples
Grab Samples
Recorded by Hand From Control Room
Grab Samples
GC/MS
Ion Chromatography
Parr Bomb/Ion Chromatography
TROIKA LABORATORIES
I. Ana lyses
o Dioxins and Furans
HRCC/HRMS
612
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TABLE 2. QUALITY ASSURANCE CRITERIA DERIVED FROM
EPA'S QANS-005/80 DOCUMENT
QA Category
Key Elements
I. Project Description
Project description
Experimental design
Intended use of acquired data
Start and completion dates
Appropriate diagrams, tables,
and figures
II. Project Organization and
Responsibili ty
Organization of project
Line of authority
Key individuals (including
quality assurance official)
III. Quality Assurance Obiectives
for Measurement Data
Precision
Accuracy
Comple teness
Represents tiveness
Comparabili ty
IV. Sampling Procedures
Site selection
Sampling procedures
Description of containers for
sample collection, preservation,
transport, and storage
Procedures to avoid sample
con tamina tion
Sample preservation methods and
holding times
Procedures for recording sample
history, sampling conditions, and
analyses to be performed
V. Sample Custody Records
Preparation of reagents or
supplies associated with sample
Location and conditions where
sample was taken
Sample preservation methods
Labeling
Field tracking forms
Field and laboratory sample
cus todians
Laboratory custody log
Laboratory handling, storage, and
dispersement procedures
613
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TABLE 2. QUALITY ASSURANCE CRITERIA DERIVED FROM
EPA's QAMS-005/80 DOCUMENT
(Con tinued)
QA Category
Key Elements
VI.
Calibration Procedures
Description of, or reference to,
calibration procedure
Frequency of calibration
Calibration standards, including
sources and traceability procedures
VII.
Analytical Procedures
Analytical procedure
Appropriateness of method
VIII.
Data Reduction, Valida-
tion, and Reporting
Data reduction scheme
Equations to t>e used
Validation procedures
Identification/treatment of outliers
IX.
Internal Quality Control
Checks
Replicates, blanks
Spiked and split samples
Control charLs, internal standards
Zero and span gases, reagent checks
Quality control samples
Calibration standards and devices
X.
Performance and Systems
Audi ts
Schedule for audits
Systems to be audited
Sources of audit materials
XI.
Procedures to Assess Data
Precision, Accuracy,
and Completeness
Central tendency and dispersion
Measures of variability
Significance tests, confidence limits
Testing for outliers
XII.
Preventive Maintenance
Schedule of maintenance tasks
List of critical spare parts on Viand
XIII.
Corrective Action
Predetermined limits for data
accep tabili ty
Procedures for corrective action
Responsible individuals
XIV.
QuailLy Assurance Reports
to Management
Frequency of reporting
Significant problems and
recommended solutions
614
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ALKALINITY TESTING OF HI-VOL FILTER5 BY A NEW METHOD
Rita M. Harrel1,
John C. Hoi 1 and
Northrop Services, Inc. - Envirormental Sciences
3.0. Box 12313
Research "Triangle ParK, NC 27709
Hi-Vol filter alkalinity measurements are important in that the EPA has set
upper limits on values for the filters because of an. apparent correlation with
artifact formation.
Reproducibility problems between the laboratories involved in making the mea-
surements, using the method A57M D 202^, prompted a study into factors in-
fluencing observed alkalinity values.I-3 On the basis of the results a new
alkalinity testing procedure, which was simpler and mere reproducible than
ASTM D 202, was developed and was accepted by the EPA.
Introducti on
Hi on volume (Hi-Vol) air samplers are widely used by air pollution con-
trol agencies and industries to determine the concentration of total suspended
particulate matter by collection on 8" x 10" Hi-Vol filters (typically com-
posed of glass or quartz fibers;.
Alkalinity measurement p'ays a useful role in the evaluation of Hi-Vol
filter performance. It is signigicant in that alkaline sites on the filters
have been shown to interact with acid gases such as SC^, N0x and HNO^ form-
ing artifact sulfate and nitrate on the filters.Sulfates and nitrates
of this type are indistinguishable from particulate sulfate and nitrate. In
turn, the total weight of particulates, sulfate content and nitrate content
determined would be falsely high. Alkalinity may not be the only factor in-
volved in artifact formation on Hi-Vol filters,^ but its measurement does
provide relative guidelines for comparing filters of different lots and
615
-------
materials as well as testing filters for compliance with EPA specifications.
Northrop Services began measuring the alkalinity of Hf-Vol filters for
the EPA in order to assess and document the quality of filters being used
nationwide. Investigation into the factors effecting observed alkalinity
values was initiated as the result of reproducibility problems between the
laboratories using the alkalinity testing procedure ASTM D 202.^ ASTH D 202
was designed for measuring the total acidity or alkalinity of electrical in-
sulating papers. A capsule summary of the procedure is as follows:
1. Extract a 1 gram sample in 100 ml of C0~-free water, at 95-100°C,
while pulping for 5 minutes using high speed agitation.
2. Vacuum filtration twice through a perforated porcelain disk, with
the initial filtration forming a mat to remove all solids during the
second filtration.
3. Titration of the hot extract to pH 7 either by pH meter or neutral
red indicator.
The results of that study, presented previously,^ led to the development of
a simpler, more reproducible method to replace ASTM D 202. Also, the study
served to help rationalize the differences observed between laboratories.
This report places emphasis on the NSI method itself, comparison of it
with ASTM D 202, and verification of its precision and reproducibility.
Experimental
Fi1ters: Whatman EPM 2000 glass and Whatman QMA quartz Hi-Vol filters were
used for most tests. Samples weighed -1 g with the exception of cases where
sample size was deliberately varied.
Reagents; Certified NaOH and HpSO. solutions were diluted quantitatively to
make 0.005N NaOH and 0.0100N H„S0. titrants, respectively. The pH meter was
calibrated at pH 7 and 10 using color-coded pH buffer solutions.
Equipment: The original extraction apparatus consisted of a 250 ml Phillips
Beaker, a mechanical stirrer with the stirrer shaft adapted with a single-
holed stopper, and a boiling water bath. Extracts were filtered from the
pulped filter through a Whatman 41 or 541 filter circle lining a heated 7 cm
ID Buchner funnel. Extracts were titrated using an Amber Science Solution
Analyzer No. 4503A with Broadley-James combination pH electrodes.
The final extraction apparatus consisted of a Phillips beaker resting direct-
ly on a stirring hot plate employing a 2" magnetic stirring bar. A glass,
water-cooled, reflux condenser was fitted in the top of the Phillips beaker
with a Meoprene or rubber stopper. Extracts were filtered and titrated as
above with the exception that the funnel was not heated.
Results and Discussion
Portions of ASTM D 202, such as sample size and extraction volume, were
retained in the NSI method. Other features were changed completely to reduce
errors in observed alkalinity values and to improve reproducibility. Table
I. provides a brief summary of the two methods.
The most dramatic difference between the two methods is extraction time.
This modification was a direct result of extraction time studies carried out
by NSI.13 In the study numerous glass and quartz fiber filters were extracted
at times ranging from 1 minute to 30 minutes. Extraction times both shorter
and longer than 5 minutes shoed substantial differences, with quartz filters
exhibiting a less pronounced effect. Table IT sumnarizes the mean % differ-
616
-------
ences for both filter types based on yeq/g. It is evident that at five min-
utes timing differences of a minute or more between analysts leads to measur-
able errors. Plots of alkalinity versus extraction time, Figure 1, were lo-
garithmic. Examination of the change in alkalinity with time (i.e. slope),
summarized in Table III, indicates that such errors can be greatly reduced
at longer extraction times. At 15-30 minutes the change in alkalinity with
time is small and timing differences become less significant.
For several reasons, high speed mechanical stirring with a hot water bath
was replaced by lower speed magnetic stirring with a 2" stirring bar and di-
rect heating on a hot piate/stirrer. To compare high speed and low speed
stirring, a 1" long magnetic stirring bar was selected first. The net result
for a set of glass filters was a difference in alkalinity of -9.6 + 3.4% be-
tween extraction using magnetic stirring and high speed mechanical stirring.
However, when a 2" stirring bar was substituted, the difference was -0.5 +
4.0%. Thus, magnetic stirring simplified the alkalinity testing procedure
without sacrificing agitation efficiency. An additional benefit of switching
to magnetic stirring was the direct heating of the extraction vessel. Pre-
viously, extract temperatures were found tc vary from 31 to 98 C at the end
of the ASTM D 202 pulping and extraction period.^ Such temperature, varia-
tions were attributed to differences in initial water temperature, poor heat
transfer from the water bath to the extraction vessel and rapid evaporative
cooling when room air was drawn into the extracting water by the high speed
stirring. Direct heating of the extraction vessel is more efficient because
the extracting water reboils within a few seconds after transfer into the
vessel and boiling is maintained throughout the extraction period. A reflux
condenser was added to prevent evaporation of water throughout the extraction.
The extraction volume was retained at 100 ml because the curve obtained
from previous volume studies^ had a slope predicting a negligible error at
this and higher volumes. Also, inspection of the combined volume and time
data showed that larger volumes increased the sloce in the time dimension more
than the reduction in the volume dimension.
Filter samples ranging in weight from 0.25 g tc 1.50 g were extracted
and the observed alkalinity values compared to the values obtained for 1.0 g
samples of the same filters. Table IV summarizes the differences observed
for both glass and quartz fiber filters, formalized alkalinity, i.e. the
alkalinity value determined for the test sample divided by the alkalinity
value determined for the sarre filter at 1.00 g, was calculated in order to
conveniently plot a large number of data points on a single graph and to con-
vert the alkalinity data for glass and quartz filters into a form that allowed
plotting of the data on the same set of axes (Figure 2). Both fitted curves
were logarithmic. The equations obtained for the fitted curves were used tc
determine if small variations from 1.0 g caused significant variations in
the observed alkalinity. In earlier routine analyses, sample weights had
not varied by more than +2%, which constituted an alkalinity variation of
+0.6% for both glass and~quartz filters. In a worst case situation, where
a +10?i variation in sample weight occured, the variation in alkalinity for
gl¥ss filters was _+3.6% and for auartz filters +3.0®. If filter samples are
confined to a weight between 0.99 and 1.01 g, where the alkalinity variation
is +0.3%, errors resulting from sample size variations remain small. Thus,
sample size was retained at -1.0 g, but as a result of this evaluation, was
restricted to a range of _+0.01 g. Cutting the filters into >{' x '¦<" squares
provided small enough pieces to easily achieve these weight limits.
Recognizing that electrodes and pH meters are not universal, the contri-
butions of three brands of electrodes and two pH meters to variations in al-
kalinity values were examined. Broadley-James combination electrodes were
used for most pH measurements. For determination of reproducebi1ity between
G17
-------
electrodes the Broadley-James electrode was compared with two other brands of
combination electrodes. Comparison with a similarly priced Fisher Scientific
combination electrode showed a difference of 0.3 + 0.1% and comparison with
a more expensive Corning X-EL combination electrode showed a difference of
-1.9 + 1.5%. Thus, differences between electrodes were relatively small.
This is especially true for comparably priced electrodes. The Corning X-EL
electrode does offer the advantage that a shorter stabilization time was re-
quired before taking a pH reading. Extracts from the same filters were ana-
lyzed using a Corning 125 pH meter and an Amber Science 4503A pH meter. The
mean % difference found was 0.8 + 1.4%. A difference of this magnitude was
expected based on earlier pH meter calibration studies^ where a difference
of -0.8 + 1.2% was observed for the alkalinities of filter extracts analyzed
with the pH meter properly calibrated and with the meter purposely adjusted
off by 0.5 pH units. Comparative laboratory studies^ also confirmed that
differences between pH meters was small.
In order to test the reproducibility of the NSI alkalinity testing pro-
cedure, interlaboratory and intralaboratory comparisons were made on a range
of difference filters. Two analysts in the same laboratory analyzed the same
set of filters with two completely difference sets of equipment and with both
analysts using the same apparatus. Overall a mean difference between analysts
of 1.0 + 2.031 was observed. Also, no significant difference was observed be-
tween sets of equipment. The best previous intralaboratory comparison had
been 3.0 + 3.5%. Thus, for analysts in the same laboratory, reproducibility
had been improved.
Collaborative alkalinity measurements^ made on a series of Hi -Vol fil-
ters in the EPA Environmental Research Center (ERC) at Research Triangle Park,
NC and in the State of California's Air and Industrial Hygiene Laboratory
(AIIIL) at Berkeley, CA provided the ultimate proof of the reproducibi1ity and
precision of the NSI alkalinity testing procedure. Previously, the AIHl. had
also been using a modified version of ASTM D 202 and attempts by NSI to re-
produce their results had been unsuccessful. Table V compares the two methods.
Six selected filters were analyzed once at Research Triangle Park and trans-
ported to California for repeated analysis. Six additional filters of vari-
ous types were selected by the AIHL and analyzed four times at that labora-
tory by both procedures. To examine the reproducibi1ity of the NS1 method,
the six filters analyzed in the AIHL by different analysts were compared and
the six filters analyzed once in RTP and once in California were compared.
Statistical analysis of the raw data, the % differences and the graphical
representation in Figure 3 indicated no significant analyst bias for the AIHL
ASTM method with 95% probability. A large degree of variability or impreci-
sion observed with that method may have masked a small analyst bias. Analysis
of data obtained with the NSI method indicates good reproducibi1ity between
analysts and 1 aboratories. Combining statistical results gives a mean percent
difference of 1.3 + 2.5%, and Figure 4 has a correlation coefficient of 0.998
between analysts. For comparison of the new NSI and AIHL ASTM methods, the
mean alkalinity values for 12 filters were plotted (Figure 5), and a linear
relationship having a correlation coefficient of 0.985 was obtained. Exclu-
sion of the very low alkalinity values did not improve the correlation. Al-
kalinity data obtained for a set of filters using NSI ASTM D 202 and the new
NSI procedure was also plotted (Figure 6), and a linear relationship was de-
rived which had a correlation coefficient of 0.936.
Conclusion
The new NSI alkalinity testing procedure^ was recommended to and ac-
cepted by the U.S. Environmental Protection Agency to replace ASTM D 202. It
is simpler, the equipment used more readily accessible, and the reproducibi-
1ity of the method has been shown to be excellent between analysts in the same
618
-------
laboratory and different laboratories. Also, the AIHL concluded that the NSI
procedure can be substituted for their procedure without sacrificing previous-
ly obtained alkalinity-SO^ retention correlations.^ jn addition the linear
correlations obtained between the NSI method and the other procedures allows
for relating previous data to current.
A cknowledaement
--
This work was supported by the U.S. Environmental Protection Agency under
Contracts 68-02-4035 and CR806734. The contents do not necessarily reflect
the views and policies of the EPA nor dees mention of trade names or commer-
cial products constitute endorsement or recommendation for use.
References
1. J.W. Coffer, "SOp Oxidation to 5ulfate on a High Volume Air Sampler",
M.S.E. Thesis, University of Washington, 1974; J.W. Coffer, C. McJilton,
and R.J. Charlson, Paper No. 102, Division of Analytical Chemistry, Ameri-
can Chemical Society, 167th National Meeting, Los Angeles, California,
April 3, 1976.
2. Robert W. Coutant, "Effects of Environmental Variables on Collection of
Atmospheric Sulfate." Envi ron Sci and Tech, 11(9):S73 ( 1977).
3. C.W. Spicer, "The Fate of Nitrogen Oxides in the Atmosphere" in Advances
in Environmental Science £nd Technology, Vol. 7 , 163 ( 1977).
4. C.W. Spicer, "The Fate of Nitrogen Oxides in the Atmosphere", Battelle-
Columbus Rep. to Coordinating Res. Council and U.S. Environmental Pro-
tection Agency Report 600/3-76-030 (1974).
5. C.W. Spicer, "Photochemical Atmospheric Pollutants Derived from Nitrogen
Oxides", Atmos Environ, 11:1089 (1977).
6. C.W. Spicer and P.M. Schumacher, "Interference in Sampling Atmospheric
Particulate Nitrate", Atmos Environ, 11:873 (1977).
7. Samuel Witz and R.D. MacPhee, "Effect of Different Types of Glass Fil-
ters on Total Suspended Particulates and Their Chemical Composition",
JAPCA, 27(3):239 (1977).
8. D.A. Trayser, E.R. Blosser, F.A. Creswick, and W.A. Preison, "Sulfuric
Acid and Nitrate Emissions from Oxidant Catalysts", paper presented at
SAE Congress and Exposition (1975).
9. B.R. Appel , E.L. Kot.'iny, Y. Tokiwa, M. Haik and J.J. Wesolowski , "Effect
of Environmental Variables and Sampling Media on the Collection of At-
mospheric Sulfate and Nitrate". Air and Industrial Hygiene Laboratory,
California Department of Health Services, 2151 Berkeley Way, Berkeley,
California 9470^-9980, Fourth Quarterly Report to CARB, Contract No.
ARB-5-1032, (1977).
10. C.W. Spicer and P.M. Schumacher, "Particulate Nitrate: Laboratory and
Field Studies of Maior Sarr.plina Interferences", Atmos Environ, 13:543
(1979).
11. Samuel Witz and J.G. Wendt, "Artifact Sulfate and Nitrate Formation at
Two Sites in the South Coast Air Basin. A Collaborative Study Between
the South Coast Air Quality Management District and the California Air
619
-------
Resources Board", Environ Sci and Tech, 15 f 1): 79 (1981).
12. B.R. Appel, V. Tokiqa, M. Haik and E.L. Kothny, "Artifact Particulate
Sulfate and Nitrate Formation of Filter Media", Atmos Environ, 18:409
(1984).
13. Rita M. Harrell and John C. Holland, "Alkalinity Measurements in Evalu-
ating Hi-Vol Filter Performance", paper presented at the Fifth Annual
National Symposium on Recent Advances in the Measurement of Air Pollu-
tants, Raleigh, NC (May 14, 1985). Submitted for publication.
14. "Standard Methods of Sampling and Testing Untreated Paper Used for Elec-
trical Insulation", ASTM D 202-77, in Annual Book of ASTM Standards,
39:62 ( 1977). ~ " " ~
15. J.C. Holland, "Collaborative Evaluation of Alkalinity Tests for Hi-Vol
Filters" Report on NSI/AIHL joint study at AIHL Laboratory, Berkeley,
California (June 1985).
16. B.R. Appel, V. Povard, E.L. Kothny, and J.J. Hesolowski, "Sampling and
Analytical Problems in Air Pollution Monitoring Phase 11", Third Quar-
terly Progress Report, Air and Industrial Hygiene Laboratory, Califor-
nia Department of Health Services, 2151 Berkeley Way, Berkeley, Cali-
fornia 94704-9980, EPA Cooperative Agreement No. CR 810798-02-0, (July
1985).
17. Rita M. Harrell, "Measuring the Alkalinity of Hi-Vol Air Filters", EMSL/
RTP-S0P-QAD-534 (October 1985).
620
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TABLE I. Comparison of ASTW D 202 and NSI Alkalinity Testing Procedures
Parameter
Method
ASTM 0202
NSI
Extraction vessel
Sample size
^0 Extraction Volume, ml
Heating technique
Extraction time, min
Mi xer
Filtration procedure
Titration vessel
Endpoint
Endpoint determination
250 ml wide mouth Erlenmeyer flask
ig
100
Boiling water bath (sample temp,
ca 95-100 C)
5.0
Mechanical stirrer, high speed
Vacuum filtration twice through a
Buchner funnel with or without
filter paper
250 ml filter flask
pH = 7.0 + 0.1
pH meter or neutral red indicator
250 ml Phi 11i ps beaker
1g + 0.01 g
100
Hot plate, reflux con-
denser (sample temp, ca
100°C)
20.0
Magnetic stirrer w/2" stir
bar
Vacuum filtration twice
through a 7 cm ID unheated
Buchner lined with Whatman
41 or 541 filter paper
250 ml filter flask
pH = 7.00 + 0.01
pH meter
-------
Table II. Alkalinity vs. Extraction Time at 100 ml
Extraction Time
Mean % Difference from 5 min
(mi nutes)
Quartz
G1 ass
1.0
-10.4
-37.0
2.0
-4.3
-25.6
3.5
-8.2
6.5
5.5
10.0
2.1
15.3
15.0
14.6
39.3
20.0
16.4
38.4
30.0
16.3
74.3
Table III. Slope Change with Extraction Time
Extraction Time
(minutes)
Quartz
Glass
1.0
1.7
32.2
5.0
0.3
6.1
10.0
0.2
3.0
15.0
0.1
2.0
20.0
0.1
1.5
30.0
0.1
1.0
Table IV. Effect of Sample Size on Alkalinity
Sample Size (g)
Mean % Difference from 1.0
Quartz
Glass
0.25
-58.8
46.5
0.50
-13.3
20.5
1.00
0.0
0.0
1.50
-9.2
-11.5
622
-------
Table V. General Description of Aim. and NSI Filter Alkalinity Procedures
Parameter
Sample Container
H^O Extraction Volume, ml
Heating Technique
Extraction Time, M1n
Mixer
Filtration Equipment
Filtration Procedure
Titration Vessel
Titration Techniques
Endpolnt
AIIIL
250 mL Phillips Beaker
100
Boiling water bath, no
reflux condenser
(sample temp. 00-87oC)
5
Polytron PCU-2-110
homogenlzer at 70T
full scale
9 cm I.D. steam-heated
Buchner funnel, 500
mL filter flask
Twice through Whatman
41 or 541
Original Phillips beaker
after transfer of extract
Potentlometrlc without
temperature control
or exclusion of atm. CO^
pH = 7.0 + 0.2 after 1 mln.
equilibration (electrode
stationary)
NSI
250 mL Phillips Beaker
100
Hot plate, relux condenser
(sample temp. ca. 100 C)
20
Magnetic stirrer with 2" stirring bar
7 cm I.D. unheated Buchner funnel,
250 mL f1Iter flask
Twice through Whatman 41 or 541
250 mL filter flask (no transfer needed)
Potentlometrlc without temperature
control or exclusion of atm. C0^
pVI » 7.00 + 0.01 after 5 mln.
equilibration (electrode stationary)
-------
FIGURE I
NORMALIZED HLKRLINHY vs EXTRACTION TIMF at JBfc!*!
0U98
QUARTZ
e.e
s
B
IB
15
2B
35
3B
IB
EXTRACTION TlfC <*1n)
FICUtE 2
NORMALIZED RLKflLINITY va SAMPLE SIZE
2.0
QLASS
B.B
624
-------
next 3
Analyst Bits Hlth RIHL Method: Holland vs. Kothny
150
130
110
U
¦
50 -
£
a!
-te
38
70
110 130 130
10
-10
50
M
ALKALINITY, KOTHNY, (Mfcroaq/g)
riamt 4
Rna1ys t Bias with New Method
KB
U
200
o
108
c
8
Alkalinity, Holland, ¦Icroiq/g
625
-------
newt i
New Method vs. RIHL RSTM DE02 Mkillnlty
300
V
cr
5
o
¦
>N
c
m
M.
IBB
I
#¦
I
50 |00
RIW. flSTH D202 Rlkttlnlty (atcroeq/g)
150
nam *
Neu Method vs. NS1 RSTM D202 fllktlInlty
«a
v
•r
5
o
15B *
>s
4»
C
IBB
m
M,
cc
1
i
i
150
58 100
MSI HSTH 0202 RlkiHMty, >lcra«q/g
626
-------
PRECISION AND ACCURACY
AMBIENT AIR MONITORING
OF STATE AND LOCAL AGENCY
DATA
Raymond C. Rhodes
Quality Assurance Division
U.S. EPA, Environmental Monitoring Systems Laboratory
Research Triangle Park, North Carolina 27711
Mm
In accordance with federal regulations, state and local air pollution
control agencies have been performing since January I, 1981, special checks
of their ambient air measurement systems to assess the. precision and accu-
racy of the monitoring data. The measurement methods involved are those for
total suspended particulate, nitrogen dioxide, sulfur dioxide, carbon monox-
ide, ozone, and lead.
The precisions of the measurement systems are estimated by some type
of replicate measurement, including the use of collocated samplers. Accu-
racies of the measurement systems are estimated by measurement of, or com-
parison vlth, reference materials or devices. Because the variations of
imprecision and inaccuracy tend to become proportional to pollution concen-
tration levels with increasing concentrations, the assessments are expressed
on a percentage basis.
State and local agencies submit their precision and accuracy assess-
ments to the EPA. The EPA, in turn, produces annual reports summarizing
and evaluating the data quality. Appreciable variation of data quality
exists across the regions, states, and local agencies of the nation. Since
1981, some improvement in data quality has been evidenced. Whenever data
users request monitoring data from the National Aerometric Data Bank, the
users automatically receive precision and accuracy assessments of the
agencies. Planned revisions to the reporting
the. precision and
corresponding air monitoring
procedure will require that
identified to each individual monitoring site.
accuracy assessments be
627
-------
PRECISION AND ACCURACY OF STATE AND LOCAL AGENCY AMBIENT AIR MONITORING DATA
INTRODUCTION
While ambient air pollution measurements have been made for many years
by state and local air pollution monitoring agencies, the establishment of
the U.S. Environmental Protection Agency (EPA) in 1970 and the subsequent
establishment of National Ambient Air Quality Standards has led to a con-
siderable increase in the number of measurements made by the state and
local agencies to monitor air quality. Measurements of the air pollutants
for which standards exist (the 6o-called criteria pollutants) have been
supplied to EPA's National Aerometric Data Bank (NADB) in Durham, NC. The
EPA uses these data to track, long-term trends in air quality, to measure
the effectiveness of air pollution control, activities, and to develop
control strategies for the nation.
Although EPA had developed and issued a number of guidance documents
recommending quality assurance practices, each state and local agency plan-
ned and Implemented its own quality assurance programs. However, In 1979
the EPA Issued regulations which required the quality assurance programs of
the states to meet certain minimum requirements. The regulations also re-
quired that the states conduct or participate in two different audit pro-
grams to assess the quality of the routine monitoring data. The first was
the performance of an internal-hut-Independent audit to assess the preci-
sion and accuracy of the measurement systems and to report the results to
EPA. This program is called PARS, the Precision and Accuracy Reporting
System.1 The second was the participation b^ the states in an external
EPA-conducted performance audit (PA) program.- A description of these two
audit programs and a discussion of some of the results follow.
To provide a comparison of pollutant concentration levels used in the
two audit programs with the concentrations specified in the National Ambi-
ent Air Quality Standards (NAAQS), the standards for the criteria pollutants
currently are as follows:
Pollutant Primary Standard, ng/m3 (ppm)
Total Suspended Particulate (TSP)
Annual Average
75
24-Ilour Average
260
Sulfur Dioxide (SO2)
Annual Average
80
( 0.03)
24-Hour Average
365
( 0.14)
Nitrogen Dioxide (NO2)
Annual Average
100
( 0.05)
Carbon Monoxide (CO)
8-Hour Average
10,000
( 9)
1-Hour Average
40,000
(35)
Ozone (O3)
1-Hour Average
235
( 0.12)
Lead (Pb)
Quarterly Average
1.5
METHOD: PARS
Federal regulations require that the states or subordinate districts
within the states perforin certain specified checks to assess the precision
628
-------
and accuracy of their measurement systems. The precision checks are dupli-
cate or repeated measurements made at ambient concentration Levels. The
concentration levels and frequencies of the checks are given in Tables I
and II.
The accuracy checks are internal-but-independent accuracy audits made
at specified concentration or flow levels. The audits of continuous ana-
lyzers are performed by challenging the analyzers with independently pre-
pared calibration sources traceable to the NationaL Bureau of Standards
(NBS). The audits of the manual methods check the accuracy of only a por-
tion of the total measurement method. For TSP, only the flow measurement
portion is audited. For the SO2 and NO2 methods, only the analytical por-
tion is audited. For Pb, the analytical portion is audited directly; how-
ever, the sampling is obtained by use of the TSP sampler, and thus assess-
ments of both the flow and analytical portions of the method are available.
For the continuous methods and TSP, accuracy audits for each site must
be performed at least once each year. Accuracy audits for the manual SO2,
NO2, and Pb methods must be performed in the laboratory each analysis day.
The results of the precision and accuracy checks are expressed as per-
centage deviations of the observed values from expected or "known" values.
Each state or subordinate district summarizes the results of its checks
each calendar quarter and reports the results as 95 percent probability
limits. The probability limits are calculated by the following expression.
D ± 1.96S
where D = the average of the percent differences
S = the standard deviation of the individual percent
di f ferences
1.96 = the standard deviate value corresponding to 95
percent probability, assuming a normal distribution
The standard deviation, S, of the percent differences is, in effect, the
coefficient of variation for the measurement method at the concentration
level involved. For precision, the standard deviation (or coefficient of
variation) represents the withir.-instruraent variability for the continuous
and manual methods. For accuracy, the standard deviation (or coefficient
of variation) represents the between-lnstruraent variability (or biases) for
continuous methods, and the within-laboratory variability of the particular
portion of the manual method checked.
The audit results presented in this report are the average coefficients
of variation of all the participating agencies in the nation.J Obviously,
the results of about half of the agencies are better than the average and
about half are worse.
Precision
The precisions of the various measurement methods, expressed as coeffi-
cients of variation, CV, (or relative standard deviation), for a recent
year are listed below:
629
-------
Manual Methods
CV, %
Continuous Methods
CV, %
so2
20.4
SO2
5.9
no2
16.1
NO 2
6.6
TSP
6.4
°3
4.8
Pb
7.9
CO
4.1
The variabilities of the manual methods are larger than For the con-
tinuous methods. However, these comparisons are not strictly valid because
the precision checks for the continuous methods are made at the specified
concentration levels (Table I) and the precisions of the manual methods are
obtained from the results of collocated samplers (duplicate filter strips
for Pb) at various ambient concentrations. Comparisons of greater validity
could be made for the SO2 and NO2 methods if the results from the collocated
samples were obtained at the same concentrations as those for the continuous
methods. Nevertheless, the magnitude of the variabilities of the manual
S(>2 and NC>2 methods are appreciable and provide Justification to change to
the continuous, but more expensive, methods.
Accuracy, Manual Methods
Figure 1 presents the accuracy results for the manual methods. The
coefficient of variation for accuracy represents the variability of the ac-
curacy audits across the monitoring agencies in the nation. As expected,
the average of the CV's fur all the agencies was very close to zero, and
the variabilities of the accuracy audit results, expressed In percentage
form, are larger at low concent ration levels.
Components of Variability, Manual Methods
The manual methods are reasonably accurate; however, It la emphasized
that only a portion of the total measurement system Is being checked. The
true accuracies of the manual methods cannot be any better than the preci-
sions. Under the optimum but unrealistic assumption that the inaccuracies
are the result of Imprecision only, i.e., no average biases within agencies,
it is interesting to compute the extent of variability that is unexplained
by tile accuracy audit results. Under the above assumption, the following
relationship exists:
(CV)
precision,
total method
(CV)2 t . , ^ + 2 1 . j
accuracy, (.precision) unexplained
portion of method
precision
The following table presents the computed coefficients of variation unex-
plained by the accuracy audit results.
Manual
Method
Total
Method
Precision
CV, %
Portion
of Method
Accuracy
(Level 1)
CV, %
Variation Unexplained
by Accuracy Audit
CV
fir
TSP
SO2
NO 2
Pb
6.4
20.4
16.1
7.9
3.5 (flow)
5.5 (analytical)
3.8 (analytical)
4.8 (analytical)
5.4 (71% of Tot. Var.)
19.6 (92% of Tot. Var.)
15.6 (94% of Tot. Var.)
6..1 (647. of Tot. Var.)
630
-------
The results for the TSP and N0£ methods are presented In graph form in
Figures 2 and 3. Similar charts could be drawn for the Pb and SO2 methods.
The sources of variability that contribute to the unexplained variability
include the factors listed below.
Possible Sources of Variability Unexplained by
Method Accuracy Audit Results
TSP Filter weighing, before and after exposure
Filter conditioning for weighing, before and
after exposure
Loss of particulate or fibers from filter after
pre-weighing
Collection of particulate
SO2 j_ Collection efficiency variation
NO2 _| Loss of absorbing solution during sampling or
in transport or handling prior to analysis
Variation in flow rate measurement
Pb Variation from strip-to-strip within a filter
Loss of particulate in transport, handling, or
cutting of strips
Inaccurate cutting of filter strips
Because the manual SO2 and N'CH methods are being replaced by the con-
tinuous methods, it would not be worthwhile to investigate the source of
variability for these methods. However, for the TSP and Pb methods, stud-
ies should be performed to determine the contributions of the various sources
of variation, with the goal of reducing the total variability.
Because the Pb method Involves the sampling method of the TSP method
and a chemical analysis for Pb of the particulate collected, it is possible,
as well as interesting to combine the estimates of variability. First,
combining the accuracy audit results for the TSP flow audit (CV ¦ 3.5%) and
the accuracy audit results for the Pb analysis (CV = 4.3%) gives a result-
ing "total" coefficient of variability of 5.9% (Figure A), in accordance
with the following equation:
(CV)2 + (CV)2 . = (CV)2 , . ^
flow analysis combined
(3.5)2 + (4.8)2 = (5.9)2
However, it is noted that the 5.95J value is less than either of the coef-
ficients of variation for precision of the Pb analysis (CV » 7.9.*) or that
of the TSP method (CV = 6.4%)! If it could be assumed that weighing por-
tion of the TSP method is very small (i.e., negligible), then the CV for
the TSP precision Includes the error variations of flow rate, the variation
in collection of Pb particulate from sampler to sampler, and possible loss
of particulate from the filters I11 handling, all of which affect the Pb
concentration. It Is then considered appropriate to combine the two CV's
to estimate the total imprecision of the Pb method. These variations are
represented in Figure 5 and expressed by the following equation.
(CV)2 + (CV)2 - (CV)2
sampling analysis combined
(6.4)2 + (7.9)2 - (10.2)2
631
-------
The CV of 10.2% for Imprecision Is nearly twice the CV of 5.9 for
accuracy 11 Thia can be explained by the following three factors:
1. the precision estimate for sampling Is based on differences be-
tween real samples collected over a 24-hour period, whereas the
accuracy estimate Is based on an audit check of the flow measure-
ment made only at a point In time,
2. the precision estimate for the chemical analysis 13 based on dif-
ferences between duplicate strips from real particulate filter
samples, whereas the accuracy estimate Is based only on an anal-
ysis of an unexposed filter strip to which a synthetically pre-
pared solution containing Pb has been added, and
3. the accuracy audits for both flow and chemical analysis may have
been performed with more-than-routlne care, whereas the routine
flow measurements and particulate determinations for the collo-
cated TSP samplers and the routine analysis of the duplicate fil-
ter strips were given only routine care.
In light of the three factors described above, the combined CV for Pb
(10.2Z) Is probably a more realistic estimate than the 5.9%.
Accuracy, Continuous Methods
Figure 6 presents the results of the accuracy audits for the continuous
methods. The results In terms of the coefficient of variability are plotted
at the accuracy audit levels 1, 2, and 3. Note that the variabilities are
higher at the lower concentrations, the same as for the manual methods, and
that the variabilities tend to become constant at the higher levels.
Also shown In Figure 6 for comparison purposes are the precision re-
sults located at their approximate relative concentration level. Note that
for CO, SO2 and O3 the values for precision fall closely In line with the
curves for the accuracy results, Indicating that practically all of the var-
iability In accuracy la the result of imprecision. In other words, any
errors of the calibration process are very small. Such Is not the case,
however, for the NO2 method. As Indicated on Figure 6, the expected vari-
ation of accuracy at the concentration level of the precision check Is
about 8.2%, compared to 6.6% for the precision variability.
Components of Variability, Continuous Methods
The following appropriate relationship for the NO2 method gives an
estimate of unexplained variability.
(CV)2 - (CV)2
accuracy precision
+ (CV)
une
2
xplalned
(8.2)2 = (6.6)2 + (CV)Z
unexplained
(CV)2 - 23.7
unexplained
CV - 4.9
unexplained
632
-------
Thus, an unexplained variability of 4.9% may possibly be explained by
variablity in the calibration process. The calibration process for contin-
uous NO2 instruments is more complicated than for the CO, SO2, and O3 meth-
ods. It may be worthwhile to investigate the NO2 calibration process to de-
termine more precisely the cause of the additional variablity. Appropriate
modification of the calibration process may reduce some of the variability.
In 1972, the EPA's Environmental Monitoring Systems Laboratory (EMSL),
located in Research Triangle Park, NC began a national performance audit
program whereby blind samples are distributed to state and local air moni-
toring agencies and other interested participants for analysis. Perform-
ance audits for various pollutant measurement methods were commenced in the
years indicated below.
Year Pollutant Measurement Method
1972 Manual SO2 (analytical portion)
As indicated, only the analytical portions of the Pb, NO3-, SC>4», manual SO2,
and manual NCb methods are audited. Only the flow measurement portion of
the TSP method is audited. Audits for the continuous NO2 and O3 methods and
for trace elements in particulate are planned for future implementation.
The audit materials for the manual SO2 and NO2 methods are freeze-dried
materials of synthetically prepared solutions. The audit materials for the
Pb, SO4", and NO3- methods are unexposed filter strips containing known
amounts of the particular chemicals. The audit devices for the flow meas-
urement of the TSP method consist of a series of test plates containing
various numbers of holes. Each plate has been calibrated against NBS-
traceable flow scandards.
The analyses for the audits for the manual SO2 and NO2 methods, and
the Pb, NO3- and 30^= methods are conducted at the state or local agency
chemical laboratories since only the analytical portion of the methods is
involved. However, the audits for the continuous methods are conducted at
individual air monitoring sites.
Sample materials or devices are furnished at multiple levels (from
three to six) to cover the range of values normally encountered in ambient
monitoring. The materials or devices are characterized extensively by com-
parison with NBS or NBS-traceable standards to ensure that the "known" val-
ues have very small associated uncertainties.
The participating agencies report their results to EMSL for evaluation
and analysis. The known, or true, values are then transmitted by EMSL to
the agencies for their self-evaluation and for corrective action, if indi-
cated by excessive deviations of their results from the known values.
EMSL analyzes and summarizes the results from all the participants
and Issues annual reports.^ A part of the analysts consists of identifying
METHOD: PA
CO
1974
1975
1976
1977
1981
Manual NO2 (analytical portion)
NO3— and SO4* in particulate (analytical portion)
TSP (flow measurement portion)
Pb in particulate (analytical portion)
Continuous SO2
633
-------
any outlier results. I.e., results that are grossly In error. Such results
are eliminated to avoid an excessive effect upon the general pattern of
results. The averages of all the participants' results are, In general,
very close to the EPA known values. However, there Is some appreciable
variability among the reported agency results. The results of 1983 audits
are presented In Figures 7 and 8.
RESULTS: PA
Manual Methods
Figure 7 presents the results of the performance audits for the manual
methods. The results of the flow measurement audits fur the TSP method are
shown only at one level corresponding to the nominal flow rate of 50 cfm.
The ranges of the concentration levels used In the other audits were:
Minimum
Maximum
S02
48 yg/ra3
178 |jg/m3
no2
0.4 iig/w3
0.9 (ig/m3
Pb
0.6 (jg/ra3
7.5 pg/ro3
SO 4=
1.2 ug/ni3
24 |ig/m3
no3-
0.8 ug/m3
14 |jg/m3
The general pattern of variabilities Is similar to those previously
shown — higher GV's at low concentration levels with the CV's becoming
nearly constant at high concentration levels.
The results for Pb analyses seem to be discontinuous between levels 3
and 4. A possible explanation Is that at higher concentrations, the levels
exceed the capacity of the Instrument readout or the linear response region
of the calibration curve, thereby requiring a dilution of the sample prior
to analysis. This additional step In the analytical process increases the
variability of the results.
Continuous Methods
Figure 0 presents the results for the continuous methods, CO and SO2.
Note that CO Is audited at only three levels, whereas SO2 is audited at five.
The ranges of the concentrations were as follows:
Minimum Maxlmm
CO 6 ppm 44 ppm
SO2 0.04 ppra 0.9 ppm
For the CO audits, three separate cylinders are used, each containing
a different concent ration. The gas from only one cylinder la used for each
analysis. For the SO? audits, a zero gas and five concentration levels are
employed through the use of a zero gas and one SO2 cylinder equipped with
three separate take-offs. The zero gas and each of the three take-offs are
valved with a restricting orifice. The valves from the gas cylinder are
numbered 1, 2, and 3 with valve 1 permitting the highest flow and valve 3,
the least flow. The various concentrations are achieved as Indicated be-
low.
634
-------
Approximate
concentration
level
.75
.52
.27
.21
.07
zero
Concentration
level
5
4
3
2
1
Number of valve(s) open
Analyzers with
0-.5 ppm range
1
2,3
2
3
all three
valves closed
Analyzers with
0-1.0 ppm range
1,2,3
1
2,3
2
3
all three
valves closed
The flow rate for each restrictive orifice is individually calibrated
with the corresponding valve in the open position.
The variability for CO decreases almost linearly, although previous
audits revealed a pattern more similar to those of Figures 1,6, and 7. The
variability of the SO2 audits are more nearly constant across audit levels.
Note that the smooth curve through the points for levels 1, 2, and 4 give
the expected pattern. The point for level 3 Is somewhat above the line.
The point foe level 5 is farther from the line. These added variabilities
arc; explained by the fact that for levels I, 2, and 4, only one gas cylin-
der valve is open; for level 3, two valves are open; and for level 5, three
valves are open. These added variabilities result from the variations in
the calibrations of the flow rates for the additional restrictive orifices
involved.
CONCLUSIONS
The precision and accuracy assessments of the internal-but-independent
checks performed by the state and local agencies, and the results of the
external audit results of the EPA performance audit program both provide
valuable information concerning the quality of ambient air monitoring data
collected by state and local agencies. The results of both programs show
that the coefficients of variation (relative standard deviations) for all
the pollutant measurement methods are higher at low concentrations and
become nore constant at higher concentrations.* Uoth programs reveal that
the manual methods for NO2 and SO? exhibit more variability (i.e., less
precision and accuracy) than the corresponding continuous methods.
REFERENCES
1. "Precision and accuracy reporting system (PARS)," Regional User's Guide
(November 1984).
2. R.C. Rhodes, B.I. Bennett, and J.C, Puzak, "EPA's national performance
audit program," Air Pollution Control Association, Pittsburgh (1982).
3. "Summary of precision and accuracy assessments for the state and local
air monitoring networks, 1982," EPA-600/4-35-03I (April 1985).
4. "National performance audit program, atihlent air audits of analytical
proficiency, 1983," EPA-600/4-84-977 (October 1984).
5. R.C. Rhodes, W.J, Mitchell, J.C. Puzak, and R.C. Evans, "Comparison
of precision and accuracy estimates from state and local agency air
monitoring stations with results of EPA's national performance audit
progr-nn," Journal of Testing and Evaluation, 13(5): 374-373 (1985).
G35
-------
TABLE I. REQUIREMENTS FOR PERFORMING PRECISION CHECKS
Parameter
Precision check level
Frequency
CO (continuous analyser)
3-10 ppm
Once every
2
weeks
SO2, NO21 and O3
(continunua analyzer)
0.08 - 0.10 ppm
Once every
2
weeks
TSP, SO2, and NO2
(manual)
Collocated samplers
(Ambient concentration)
Once every
6
days
Pb
Duplicate filter strips
(Ambient concentration)
Once every
6
days
TABLfi II. CONCENTRATION LEVELS FOR CONDUCTING
ACCURACY AUDITS
Parameter
Level 1
Le ve1 2
Level 3
Level 4
S02, N02, 03
(continuous)
0.03-0.08 ppra
0.13-0.20 ppm
0.3 5-0.45
ppra
O.RO-0.90
ppm
CO
3-8 ppm
15-20 ppm
35-45 ppm
80-50 ppm
TSP (flow only)
1.13-1,70 nrVrnln
SO2 (manual)*
0.013-0,020 ppm
0.033-0.040 ppm
0.053-0.059
NO2 (manual)*
0.010-0.028 ppm
0,046-0.055 ppm
ppm
0.074-0.083
Pb**
0.6-1.8 Mg/m^
3.5-5.9 ws/m3
ppm
*Concentration levels corresponding to flow rates of .2 L/min
**Conceat ration levels corresponding to flow rated of 50 cfm.
1 vr—1 1—1 vr
ACCU R AC V AUDIT LEVEL
Figure I. Accuracy audit results for manual methods for PARS,
63G
-------
UN EXPLAIN EO
Components of
variation for the
TSP method.
ANALYSIS
Figure 3. Components of variation
for the manual NO2 method.
7.9
CHEMICAL ANALYSIS
Figure 4.
Components of
variation for the
accuracy of the
Pb method.
Figure 5. Components of variation
for the precision of the
Pb method.
637
-------
C CO
~ SO]
A NO;
00|
S
I
z
o
<
£
>
Q
>-
z
u
5
14-hr — '
ACCURACV Al.OiT LEVEL
Figure 6. Accuracy audit (and precision) results for continuous methods
for PARS.
> t«
1-yf—X *
ACCUPflC* AUDIT lEVtl
34-Kr-
3 (no—> L. i .yr
Figure 7. Performance audit results for manual methods for 1983,
ACCURACY AUDIT LEVEL
Figure 8. Performance audit results for continuous methods for 1983
638
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SOME NEW COST-EFFECTIVE APPROACHES FOR MEASURING
ORGANICS ASSOCIATED WITH HAZARDOUS WASTES*
R. B. Ganmage, T. G. Matthevs, T. Vo-Dinh
Health and Safety Research Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee 37831
A number of newer and often highly sensitive analytical techniques and field
monitoring devices are described that have potential suitability for
monitoring organic hazardous vastes. The focus is on devices and methods that
are cost-effective and permit either direct measurements in the field or
screening-type measurements on samples returned to the laboratory for
analysis. Most of these methods are directed at categories of less volatile
organic compounds. The results of some very preliminary field tests are
given. Most promising were the results obtained for a wide variety of ground
and surface waters screened spectroscopically using synchronous fluorescence.
*Research sponsored by the Division of Remedial Actions Projects,
U.S. Department of Energyj under Contract No. DE-AC05-840R21400 with
Martin Marietta Energy Systems, Inc.
639
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Introduction
Land disposal facilities are subject to compliance with the 1981 Resource
Conservation and Recovery Act (RCRA) groundwater monitoring requirements. The
procedures for compliance are expensive. They typically involve general
hydrological investigation and drilling of monitoring wells to obtain samples
of groundwater. Chemical analysis using gas chromatography-mass spectroscopy
(GCMS), which EPA favors for priority pollutants, costs about $1000 per set of
analyses' '.
Methods for improving the cost-effectiveness of detecting contaminant
plumes and screening groundwater for the presence of priority organic
pollutants have an obvious attractiveness. Considerable activity has been
reported recently for improving the detection and analytical capabilities for
underground organic pollutants. A few noteworthy examples will be given
below.
A fiber optic probe carrying UV light can be lowered down a test well
Fluorescence is excited directly in the water from organics such as benzene
and other aromatic compounds. This quick and relatively inexpensive, but
non-compound selective, test procedure is claimed to be useful for determining
whether more expensive laboratory tests are needed. Specific and sensitive
analysis of volatile organics chlorides in groundwater has been accomplished
by attachment of an optrode to the distal end of the fiber'^'. Part-per-
million concentrations of volatile organic chlorides have been quantified in
aqueous media.
A rather simple GC screening technique has been developed by EPA for
analyzing volatile organic compounds (VOC) in collected samples of
groundwater'^'. The technique involves partiocing of VOC between water and
air inside a small sample vial. A headspace sample of equilibrated air is
withdrawn by a syringe inserted through a septum. The VOC are analyzed with a
portable gas chromatograph equipped with a photoionization detector. This
headspace technique for GC screening and quantification is complementary to
the more accurate and informative EPA Method 624 that employs CGMS. It
becomes especially cost-effective in situations where the accuracy and
precision of the Method 624 is not required.
Other field devices have been developed for the collection and analysis
of VOC in soil gases. One such technique measures emission rates from land
surfaces using a hemispherical emission flux chamber placed at ground
level' . The gaseous emissions are swept through an exit port. The VOC
concentrations are monitored in real time with a portable total hydrocarbon
analyzer or else discrete air samples are analyzed by GC for specific VOC.
Rods driven into the ground are used to sample soil gases at different
depths up to 15 feet'"'. Soil air is withdrawn through the rod and
subsequently analyzed for VOC, usually with a GC. For sampling at shallow
depths, a device composed of a passive charcoal sorbent inside a test tube is
buried below the surface and left for an extended period of time, usually
1 day'^. After retrieval, the VOC are desorbed thermally and analyzed by
GCMS. A plot of land can be contoured relatively inexpensively for VOC by
laying out a grid of these devices all at the same time.
640
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This presentation focuses on some alternative methods that have
attractive potential for measuring organic compounds in soil, soil gas, and
groundwater. The methods are described briefly and results from a preliminary
field investigation are given.
Field Monitoring Devices
TheBe are monitoring devices that can be operated in the
they can provide real- or near real-time measurements of
pollutants or else they are devices that sorb chemical
subsequent analysis.
Fluorescence Monitors
Two hand-carried devices have been developed at ORNL
fluorescent contamination in the field.
Spill Spotter. A beam of UV light is shone through a telephoto lens at
the object of interest^®]. The UV light is modulated at 1 KHz. Any returning
fluorescence, at a frequency of 1 KHz, is demodulated and filtered. The
signal output is used to drive an audio oscillator, the pitch of whose noise
increases with increase in the fluorescence intensity. The recorded
fluorescence intensity is distance independent over distances ranging from
0 cm to 80 cm when the illumination beam is focused 40 cm from the spotter.
An accompanying battery pack is used for field work. Readings can be taken
even in direct sunlight.
The spill spotter readings can be converted to benzo[a]pyrene (BaP)
fluorescence equivalent units by reference to fluorescence from a standard of
BaP embedded in a block of epoxy. Because fluorescence is often strongly
quenched in real-life situations, the spill spotter is best suited to
providing yes or no answers about the presence of fluorescing contamination.
Two 6uch applications are delineating the boundaries of surface contamination
or measuring skin contamination on workers handling process oils at a coal-
liquefaction plant^'J.
Lightpipe Luminoscope. Fiberoptics direct ultraviolet light to a
stethoscopic cap pressed against the surface of intereBt^^. Induced
fluorescence is returned along the bifurcated lightguide, processed and
recorded either as an audio signal or meter reading. The principal intended
use was measurement of Bkin contamination but, in principal, any solid surface
can be examined. Liquid sampleB can also be spotted on filter paper and
examined for fluorescing content with the luminoscope. If need be, this
operation can be conducted in the field. Tar and oil can be detected
typically at concentrations as low as 10 ng/cm^ on filter paper. Above about
300 ng/cm^, quenching effects reduce the intensity of the fluorescence and
produce non-linearity of response. The lightpipe luminoBcope is also being
adapted as a small remote sensor for fluorescing contaminants in groundwater.
field. Either
hazardous wa6te
pollutants for
for measuring
641
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Derivative Ultraviolet Absorption Spectrometer (DUVAS)
This email (liftable) microprocessor-controlled spectrometer can be
operated either with a gas cell for air monitoring^^' or a small quartz cell
for measuring liquid samples. Within complex mixtures of compounds it is
possible to selectively analyze specific compounds that have narrow absorption
bands. This is possible because in the second-derivative mode, where one is
measuring band curvature, the spectrometer response to narrow bands is
enhanced while response to broad bands is reduced.
A functional prototype device produces a second-derivative signal by use
of numerical methods in an integral microcomputer. Compared to an instrument
based on wavelength modulation with detection of the second harmonic of the
modulated frequency, an instrument using numerical derivatization considerably
simplifies the optics, reduces the size, and improves the reliability of a
portable DUVAS.
The DUVAS is suitable for measuring phenol and methyl-substituted phenols
in water of variable turbidity' . A small flow-through cell and a small
peristaltic pump can be employed if continuous monitoring of a water source is
needed. Phenol can be measured directly at concentrations of 1 ppm and above.
Sensitivity can be improved by extraction and concentration of the phenol in a
solvent phase. But then one looses the direct capability for eaBy on-site
measurement s.
Passive Gas Sorption Monitors
Surface Emission Rate Monitor for Volatile Organic Compounds. This
device is composed of a circular canister with one open face'^]. it i8
placed open face down on the ground during sampling. The sorbent of granular
charcoal rests on a mesh screen. The amount of charcoal is sufficient to sorb
all the volatile organic compounds that are emitted from the ground area
enclosed by the container.
After the period of time for sampling is completed, the charcoal is
removed, sealed in a small container, and returned to the laboratory.
Analysis is conducted by solvent extraction of volatile organic compounds with
carbon disulphide and gas chromatography with flame ionization and electron
capture detectors.
Filter Paper Sorption Monitors. This simple device consists of a small
disk of filter paper that iB placed within a small holder. The filter paper
is the vapor sorption element. During the period of time of sampling, the
device i6 exposed to soil gases either underground or else within an open-
ended small container set at ground level.
After exposure in the field, the device is returned to the laboratory
inside a sealed container.
Analysis is conducted by the room-temperature-phosphorescence
technique^. The filter paper is pretreated with a solution containing a
heavy-atom salt that facilitate emission of phosphorescence at room
temperature'*5]t reader is a standard spectrofluorimeter with a
642
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phosphorescopic attachment. Only Luminescing compounds are detected. These
are usually in the claBs of compounds known as polynuclear aromatic
hydrocarbons. These are compounds of intermediate or low volatility that can
be detected in sub-ng amounts on the filter paper. It is anticipated in the
future that some weakly or non-luminescing molecules will become amenable to
sorption on silver or gold coated substrates and analysis by surface-enhanced
Raman scattering^ . The technique makes detection of several peBticidee and
herbicides a possibility. Detection of vapors of the insecticide Parathion is
an example.
Laboratory Analysis of Water SampleB
Synchronous Fluorescence (SF)
To use this technique, the excitation and emission monochrotnators of a
fluorescence spectrometer are locked together at a fixed wavelength separation
such that a spectrum can be scanned synchronously'^. Samples of water,
or other solvents that are UV transparent, are loaded into a small cuvette for
the analyses of fluorescing analytes. The principal advantage of recording a
fluorescence spectrum synchronously is that compound or groups selectivity is
enhanced by spectral simplification. Considerable success has been achieved,
especially in the ranking of a series of related environmental samples
containing complex mixtures of aromatic compounds^^^.
Room-Temperature Phosphorescence (RTP)
Often this technique is employed in conjunction with SF measurements
since it provides information about luminescing constituents that is often
complementary^^. A few uL of water are spotted on filter paper pretreated
with the salt of a heavy atom, such as lead acetate. The heavy atom serves to
promote the conversion of singlet to triplet excitated states from which
phosphorescence can occur' The small disk of filter paper is first dried
and then inserted into a fluorescence spectrometer equipped with a
phosphorescopic attachment. As with SF, RTP has already enjoyed successes in
the ranking of a Beries of environmentally related samples'- *5,20 J _
Results and Discussion
A pilot study was initiated recently on the DOE reservation in Oak Ridge
at a number of disposal sites for hazardous waste. Oils and degreasing
solvents used in machine shop operations were the principal sources of
contamination.
Surface Measurements
At an oil landfarm disposal area, luminescing constituents were sought
with the spill spotter and RTP passive monitors. The spill spotter detected
weak fluorescence in oily surface dirt. The fluorescence intensity was,
however, weak and equivalent to only 0.3 ppm BaP. It is conceivable that the
fluorescence was weak because cf quenching caused by an overabundance of
aromatic compounds. This possibility can be checked by adding a solvent to
643
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the dirt to dilute the aromatic compounds and increase their ability to
fluoresce strongly. Treatment of the dirt with solvent did not, however,
increase the fluorescence induced by the spill spotter. The oily dirt must
have been contaminated largely with non-fluorescing organic compounds.
Neither did RTP filter paper monitors left at the site pick up measurable
amounts of phosphorescing organic vapors. These devices were left overnight
inside open-ended canisters placed upside down on the ground. This finding
again points to low concentrations of high-boiling aromatics in the oily dirt.
The passive surface emission monitor for detecting volatile organics was
left overnight on the ground at a number of different locations. At the oil
landfarm area, several organics with a wide range of volatilities were
detected. Analyses of water from wells drilled in this region have also shown
VOC to be present in rather low concentrations. On the other hand, at a
surface location downhill from an old solvent disposal area, a large number of
VOC were detected in abundance including VOC identified tentatively as carbon
tetrachloride, trichloroethylene, and tetrachloroethylene. Trichloroethylene
and tetrachloroethylene were measured by GCMS in the well water at this
location at concentrations of about 2 ppm and 17 ppm, respectively. These
chlorinated hydrocarbons are resistant to biodegradation. A different
admixture of VOC were measured on the banks of a oil retention pond. About 20
compounds with a wide range of volatilities were detected.
TheBe minor successes open up the possibility of being able to use these
passive monitors to measure rates of emission of VOC at ground level. Large
numbers of these monitors could be dispersed at a site to provide contour maps
of emission intensity and to enable estimates to be made of total release of
VOC into the atmosphere.
Water Measurements
SampleB of different well water and some surface waters were examined by
the two techniques of derivative ultraviolet absorption spectroscopy and
synchronous fluorescence.
Water from one well (designated GW15) located close to the inactive
solvent disposal area was known to contain benzene at a concentration of about
100 ppm. Additionally this well water contained a host of other VOC at lower
concentrations. The direct measurement in this well water of the UV-absorbing
benzene was made using the DUVAS without any sample preparation or solvent
extraction. The benzene concentration in the well water was 80 ppm. The ease
with which the analysis was accomplished suggests that the DUVAS would be
ideal for monitoring temporal fluctuations in benzene concentration at this
particular location. Laboratory tests using cyclohexane to extract benzene
from the aqueous phase point to a lower limit of detection of 0.1 ppm.
The results of synchronous fluorescence analysis of 1 ml samples of water
were most encouraging. Fluorescence was detected synchronously in virtually
all of the water samples that were collected from a wide variety of well and
surface locations. These SF spectra are shown in Figures 1 and 2. The
surface waters give mainly weakly structure a SF emission. The well waters on
the hand produce SF emission with sufficient structure to indicate that
specific compounds or groups of compounds should be identifiable and
644
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quantifiable. Whether or not peak resolution happens to be possible, the
water samples can be ranked according to their integrated SF. The ranking of
this group of water samples according to integrated SF is listed in Table I.
This ranking is made on the basis of arbitrary units of total fluorescence
intensity. Alternately, by reference to a standard mixture of polynuclear
aromatic (FNA) hydrocarbons of known concentrations, it would be possible to
quantify the fluorescence of a particular sample in units of PNA equivalent
concentration (ng/ml). The limit of detection for a fluorescent compound such
as anthracene is about 0.1 ng/ml (0.1 ppb).
There is every reason to believe that SF screening of water samples will
become a useful technique for quickly evaluating the overall quantity and
nature of fluorescing constituents.
A number of new field monitoring devices and analytical screening
techniques are described that have the potential for measuring and screening
organic hazardous wastes in soil, soil gas, and water. The majority of these
approaches are directed at the detection of categories of less volatile
organic compounds, such as higher-boiling aromatics. These techniques will
serve to complement a number of screening methods for VOC that have been
developed by others. Some very preliminary field tests have been conducted
using some of these new devises and analytical methods. The most promising
method to date was SF screening as it was applied to a number of ground and
surface waters.
Acknowledgements
Several other individuals played significant roles in the collection of
field samples, conduct of laboratory analyses, and data treatment. In this
regard, the efforts of G. H. Miller, D. L. Wilson, A. R. Hawthorne, and
J. E. Mrochek are recognized and appreciated. The help of G. E. Kamp was
invaluable in the organization of the field studies.
645
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References
1. R. M. Dowd, "Groundwater Monitoring," Environ. Sci. Technol. 19(6): 485
(1985).
2. W. Chudyk, "Laser Technology for Detecting Toxic Contaminants in
Groundwater." C&E News (1986).
3. F. Milanovich, T. Hirschfeld, H. Miller, D. Garvis, W. Anderson,
F. Miller, S. M. Klainer, "The Feasibility of Using Fiber Optics for
Monitoring Groundwater Contaminants II Organic Chloride Optrode," Report
AD-89-F-2A074, March 25, 1985, prepared for Advanced Monitoring Systems,
Environmental Monitoring Systems Laboratory, Office of Research and
Development, VSEPA, Las Vegas, NV 89114.
4. A. F,. Clark, M. Lataille, E. L. Taylor, "The Use of a Portable FID
Chromatograph for Rapid Screening of Samples for Furgeable Organic
Compounds in the Field and in the Laboratory," Report dated June 29,
1983, USEPA Region I Laboratory, 60 Westview Street, Lexington, MA 02173.
5. M. R. Kienbusch, "Measurement of Gaseous Emission Rates from Land
Surfaces Using an Emission Isolation Flux Chamber: User's Guide," EPA
Report 600/8-86/008, USEFA Environmental Monitoring Systems Laboratory,
P.O. Box 15027, Las Vegas, NV 89114-15027, February, 1986.
6. D. L. Marriu, "Delineation of Gasoline Hydrocarbons in Groundwater by
Soil Gas Analysis," to be published in Proc. 1985 Hazardous Materials
West Conference by the lower Conference Management Company.
7. K. J. Voorhees, J. C. Hickey, R. W. Klusman, "Analysis of Groundwater
Contamination by a New Surface Static Trapping/MasB Spectrometry
Technique," Anal. Chem. 56:2602-2604 (1984).
8. D. D, Shuresko, "Portable Fluorimetric Monitor for Detection of Surface
Contamination by Polynuclear Aromatic Compounds," Anal. Chem. 52:371-373
(1980).
9. R. H. Hill, "Ultraviolet Detection of Synthetic Oil Contamination of
Skin." Am. Ind. Hyg. Assoc. J. 45:474-484 (1984).
10. T. Vo-Dinh, R. B. Gammage, "The Lightpipe Luminoscope for Monitoring
Occupational Skin Contamination." Am. Ind. Hyg. Assoc. J. 42:112-120
(1981).
11. A. R. Hawthorne, "DUVAS: A Real-Time Aromatic Vapor Monitor for Coal
Conversion Facilities." Am. Ind. Hyg. Assoc. J. 41:915-921 (1980).
12. A. R. Hawthorne, S. A. Morris, R. L, Moody, R, B. Gammage, "DUVAS as a
Real-Time, Field-Portable Wastewater Monitor for Plienolics," J. Environ.
Sci. Health. A19(3):253-266 (1984).
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13. T. G. Matthews, A. R. Hawthorne, C. R. Daffron, T. J. Read, "Surface
Emission Monitoring for Formaldehyde: Source Strength Analysis," Proc.
APCA Specialty Conference on Measurement and Monitoring of Non-Criteria
(Toxic) Contaminants in Air, pp 441-452 (1983).
14. T. Vo-Dinh, "Room Temperature Phosphorimetry for Chemical Analysis,"
John Wiley, New York (1984).
15. T. Vo-Dinh, J. R. Hooyman, "Selective Heavy-Atom Perturbation for
Analysis of Complex Mixtures by Room-Temperature Phosphorimetry, "
Anal. Chem. £1:1915-1921 (1979).
16. T. Vo-Dinh, M.Y.K. Eiroiaoto, G. M. Begun, R. L. Moody, "Surface-Enhanced
Raman Spectrometry for Trace Organic Analysis," Anal. Chem. 56:1667-1670
(1984).
17. T. Vo-Dinh, "Multicomponent Analysis by Synchronous Luminescence
Spectroscopy," Ana1. Chem. ,50:396-401 (1978).
18. T. Vo-Dinh, R. B. Gammage, A. R. Hawthorne, "Analysis of Organic
Pollutants by Synchronous Luminescence Spectrometry," Polynuclear
Aromatic Hydrocarbons, ed. P. W. Jones and P. Leber, Ann Arbor Science,
Ann Arbor, MI, pp 111-119 (1979).
19. T. Vo-Dinh, D. W. Abbott, "Ranking Index to Characterize Polynuclear
Aromatic Pollutants in Environmental Samples," Environ. International
10:299-304 (1984).
20. T. Vo-Dinh, T. J. Bruewer, G. C. Colovos, T. J. Wagner, R. H. Jungers,
"Field Evaluation of a Cost-Effective Screening Procedure for Polynuclear
Aromatic Pollutants in Ambient Air Samples," Environ. Sci. and Technol.
18^477-482 (1984).
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TABLE I. INTEGRATED SYNCHRONOUS FLUORESCENCE INTENSITY FOR SAMPLES
OF SURFACE AND WELL WATER NORMALIZED TO THE SYNCHRONOUS
FLUORESCENCE INTENSITY OBTAINED FOR DRINKING WATER
Integrated synchronous Ranking of samples
Water fluorescence normalized according to
sample to drinking water fluorescing content
GW23
4.8
1
GW14
3.2
2
Fuddle by
Retention
Pond No. 1
2.8
3
S-3 Pond
2.5
4
GW8
2.2
5
Retention
Pond No. 1
2.2
6
GW15
1.9
7
Retention
Pond No. 1
Run Off
1.6
6
64B
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CO
I—
500
300
WAVELENGTH (m)
Figure 1. Synchronous fluorescence spectra for (1) drinking water,
(2) run-off water fron oil retention pond no. 1, (3) surface
water from oil retention pond no. 1, (4) surface water from
S-3 pond, and (5) puddle water on bank of oil retention pond
no. 1. Wavelength separation (ii) between excitation and
emission monochromators was 5nm.
649
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(/)
f-
>-
cx
I
8
<
Vw'
1—4
DR1N>. INC- WATER 1.7
300
WAVELENGTH (NT-*)
Figure 2. Synchronous fluorescence spectra (M=5nin)
for samples of well water close to an inactive
solvent disposal area (GW14, GW15 samples), waste
retention pond no. 2 (GW23 sample), and oil land-
farm area (GW8). The values for integrated SF
are noted in arbitrary units.
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SURFACE-ENHANCED RAMAN SPECTROSCOPY:
HAZARDOUS CHEMICAL POLLUTANTS *
DETECTION OF
Vo—Dinh
and R. L. Moody, Health and Safety
Research Division, Oak Ridge National
Laboratory, Oak Ridge, Tennessee
Hazardous pollutants emitted from waste materials have toxicological1y
important chemical groups that can be characterized and detected by Raman
spectroscopy. The conventional Raman technique, however, is often limited by
its low sensitivity due to the inherently weak Raman cross section of organic
chemicals. In this paper we report on a new detection technique based on the
Surface-enhanced Raman Scattering (SERS) technique. The SERS effect is based
on recent experimental observations, which have indicated enhancement of the
Raman scattering efficiency by factors up to 10 when a compound is adsorbed
on rough metallic (silver) surfaces having submicron protrusions. In this
report we describe the development of the SERS technique as a new tool for
monitoring hazardous chemical emissions.
Substrates developed in this laboratory consist of flexible materials
such as filter paper and cellulosic membranes or rigid surfaces such as glass
or quartz plates coated with submicron size polystyrene latex spheres. The
microsphere—coatcd substrates are then covered with silver by vacuus
evaporation. Another type of substrate consists of thermally etched quartz
substrates having prolate SiO^ posts coated with silver particles. The
results for a variety of hazardous polycyclic compounds and multicomponent
mixtures demonstrate the usefulness of this technique for detecting low-level
toxic organic chemicals.
•Research jointly sponsored by the U.S. Department of the Army
(Interagency Agreement No.'s DOE 40-1294-82/Army 3311-1450), and the Office
of Health and Environmental Research, U.S. Department of Energy, under Con-
tract DE-AC05-840R21400 with Martin Marietta Energy Systems, Inc.
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SURFACE-ENHANCED RAMAN SPECTROSCOPY: DETECTION OF HAZARDOUS CHEMICAL POLLUTANTS
INTRODUCTION
Hazardous pollutants emitted from energy-related technologies, chemical
industries, or waste materials are of increasing public concern because of
their potential adverse health effects. Many pollutants have chemical groups
of toxicological importance that can be characterized and detected by Raman
spectroscopy.
Raman spectroscopy, however, has not been widely used in trace organic
detection, even though the information contained in a Raman spectrum is most
valuable for chemical identification. One limitation of conventional Raman
spectrosocpy is its Low sensitivity that often requires the use of powerful
and costly laser sources for excitation. However, a renewed interest has
recently developed among Raman spectroscopists as a result of various
observations that indicate enhancements in the Raman scattering efficiency by
factors up to 10*> when a compound is adsorbed on or near special metal
surfaces*. These spectacular enhancement factors of the normally weak Raman
scattering process help overcome the normally low sensitivity of Raman
spectroscopy. The technique associated with this phenomenon is known as
Surface-Enhanced Raman Scattering (SERS) spectroscopy. The Raman enhancement
process is believed to result from a combination of several electromagnetic
and chemical effects between the molecule and the surface^' .
In this communication we report the use of the SERS technique as a tool
for monitoring compounds of environmental interest. An important class of
environmental pollutants includes the polynuclear aromatic (PNA) compounds.
The PNA compounds present a potential health hazard because some of these
species are known to be carcinogenic in animal laboratory assays^. Extensive
studies have been devoted to developing analytical techniques for the
identification and quantification of PNA species in environmental samples such
as air, soot, water, and soils^. In previous studies we have described the
development of various luminescence techniques for trace analysis of PNA
compounds in complex environmental samples®''. In this study we describe the
use of SERS for the characterization of a variety of important PNA air
pollutants. Several examples of detection of PNA compounds commonly found in
air particulates, such as anthracene, pyrene, and carbazole, Illustrate the
usefulness of the SERS technique using substrates developed in our
laboratory®--*-^. The specificity of SERS for the analysis of complex mixtures
is also illustrated in the characterization of a three-component sample
containing benzo[a]pyrene, pyrene, and 1-nitropyrene, The potential of the
SERS technique for air pollution detection is discussed,
EXPERIMENTAL SECTION
Apparatus
The instrumental system has been described in detail previously®. Only
the salient features are given here. A high-resolution Raman spectrometer
with double grating (SPEX, Model 1403) was used for SERS measurements. The
excitation light sources were an argon ion laser (Spectra Physics, Model 164)
and a krypton ion laser (Coherent, Model INNOVA 90K) . The spectrometer
652
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detector was a gallium arsenide photomultiplier (RCA, Model C31034) operated
in the single-photon counting node. Data storage and processing were
performed on a SPEX Datamate DN1 Processor. All spectra were recorded with
slit widths of 400 pm providing a 0,2-nm spectral resolution. A Vacuum
Industries, Inc. plasma etcher using CHF3 plasma was used for etching
substrate snrfaces. A quartz crystal thickness monitor (Kronos, Inc., Model
QM-311) was used to measure the thickness of the silver layers on the
substrate s.
Chemicals and Reagents
Polynuclear aromatic compounds including anthracene, benzo [a]pyrene,
carbazole, and 1—nitropyrene, were purchased in the purest grade commercially
available. The solvent used was ethanol, spectroscopic grade (Aager
Chemical) .
Preparation of SERS-Active Substrates
We have investigated experimental procedures for producing SERS-active
substrates that can be easily prepared and yet yield results with good
sensitivity and reproducibility. Two practical approaches involve:
(1) coating various solid surfaces first with submicron spheres and then
depositing a layer of silver to produce a uniformly rough metal surface, and
(2) etching a crystalline Si02 surface to produce submicron prolate posts
which are also coated with silver. The detailed descriptions of these various
SERS techniques have been given elsewhere®-^. Only the major features of the
experimental conditions are provided here.
Substrates with Silver-Coated Spheres: A 200-(iL volume of a suspension
of 0 .364—fim latex microspheres was applied to the surface of the substrate of
interest (cellulose, quartz, or glass plate). The substrate was then placed
on a spinning device (Headway Research, Inc.) and spun at 800-2000 rpm for 20
seconds. The solid substrates investigated in this work were filter paper and
quartz microscope slides. The silver was deposited on the sphere-coated
substrate in a vacuum evaporator at a rate of 1.5-2 am/sec. The depth of
silver deposited was 150-200 nm.
Silver-coated Prolate Posts: The preparation of Si02 prolate posts
involves plasma etching of Si02 with a silver island film as an etch mask**-".
Since fused quartz etches much more slowly than thermally deposited quartz, a
500—nm layer of Si02 was thermally evaporated onto fused quartz at a rate of
0.1-0.2 nm.s-*. The resulting crystalline quartz was annealed to the fused
quartz for 45 minutes at ca 950®C. A 5-nm silver layer was then evaporated
onto the thermal Si02 layer and the substrate was flash-heated for 20 seconds
at ca. 500°C. This heating causes the thin silver layer to bead up into small
globules which act as etch masks. The substrate was then etched for 30-60
minutes in a CHF3 plasma to produce submicron prolate Si02 posts, which were
then coated with an 80 nm silver layer at normal evaporation angle.
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RESULTS AND DISCUSSION
SERS Detection of PNA Compounds
In most previous studies, SERS neisurements were performed mainly for
small compounds such as highly polarizable monocyclic molecules^. In this
work we evaluate the SERS technique for a variety of PNA species. Figure 1
shows the SERS spectrum of anthracene adsorbed on a silver/quartz-post
substrate. Anthracene was selected since this compound is an important species
on the EPA Priority Pollutants List. Several major SERS peaks, at 1275,
1412, and 1564 cm-* correspond to the normal Raman bands observed in
polycrystal1ine anthracene at 1258, 1403 , and 1556 cm"* . These three Raman
peaks were assigned to ag symmetry, with the last two peaks attributed to
totally symmetric C-C stretch modes. The SERS spectrum indicates also that
several non-totally symmetric modes can be observed in the spectrum; these
peaks are not prominent in the SERS spectrum, but are quite visible at the
spectral frequencies 405, 1190, and 1477 cm-1. These three peaks could be
assigned to the b3g Raman bands observed in anthracene at 394, 1185, and 1477
en"' .
Figure 2 shows the SERS spectrum of pyrene using the 647.1 nm laser
emission line for excitation. Pyrene is also an important EPA Priority
pollutant commonly found in air samples. The spectrum of pyrene was obtained
using a prolate post substrate. The signal corresponds to the SERS emission
from 7,2 ng of the pyrene sample spot illuminated by the laser beam. The SERS
spectrum of pyrene exhibit a series of sharp peaks that could be assigned to
ag symmetry: The major peaks at 385, 785, 1038, 1180, 1220, 1235, 1380, 1490,
1540, and 1618 cm-* have frequencies close to ag symmetry bands observed
in the Raman spectra of pyrene in solution at 408, 802, 1040, 1192, 1233,
1242, 1395, 1504, 1553, and 1632 cm-*, respectively. In addition the SERS
spectrum exhibit a peak at 1582 cm-*, which has the spectral frequency close
to the b3g symmetry band at 1597 en"' observed in Raman spectra of pyrene in
solut ion.
Figure 3 depicts the SERS spectrum of carbazole adsorbed onto 0another
type of solid substrate (0.364-jim spheres on glass with a 2000 A silver
layer). Carbazole is an important nitrogen-heterocyclic compound often found
in polluted airs and cigarette smoke emissions. In the SERS spectrum the
peak at about 300 cm-* is essentially the same as in the conventional Raman
spectrum of solid carbazole (305 cm-*), but the positions of the other
enhanced peaks at 690, 996, and 1061 cm-* are shifted considerably from the
bulk carbazole peaks found at 435, 555, 746, 1015. and 1112 cm-*. Some
spectral changes are expected in SERS spectra relative to conventional Raman
spectra and are indicative that the vibrations responsible for the shifted
peaks are affected by adsorption onto the metal. It is expected that the
spectral shifts will be greater in cases of chemisorption than in cases of
simple adsorption. Figure 3 shows the 996 and 1061 cm-* carbazole peaks from
a 10 |iL spot of 10_® M solution. This represents only 1.7 ng of material. We
have investigated the dependence of the SERS signal intensity upon the
excitation wavelength usigg the two emission lines of the argon-ion laser at
4880 and 5145 A. Jhe 5145 A excitation line produced a stronger SERS signal
than did the 4880 A line.
654
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Characterization of Mixtures
A major advantage of Raman spectroscopy is the spectral selectivity of
the technique for the analysis of complex mixtures because of the sharpness of
the Kxman emission peaks. Figure 4 illustrates this spectral selectivity for
the SERS technique for the characterization of a synthetic mixture containing
benzo[a]pyrene (BaP), 1-nitropyrene, and pyrene. We have selected these three
PNA pollutants for several reasons. Benzo[a]pyrene is an important
environjnental air pollutant, which was found to induce cancer in animal
bioassays^. Nitro-PNA compounds have also received intensive interest.
These species are often produced in atmospheric reactions of PNA with N0X or
during incomplete combusion in automobile engines^. Nitro-PNA species have
been detected in a variety of products including ambient particulates, diesel
exhause emissions, and carbon black and xerographic toners. Recent studies
have indicated that nitro-PNA compounds induce carcinogenic activity in rats.
Special attention is devoted to the detection of 1-nitropyrene (1-NP), a
potent direct-acting bacterial mutagen often found in light—duty diesel
exhaust particulate extract. In a previous work, we described the use of SERS
to detect nitro-compounds^^-. In this study we further illustrate the use of
SERS to detect 1-NP in the presence of other PNA species. As shown in Figure
4 the SERS spectrum of the three—component mixture exhibit a series of sharp
peaks that can be assigned to 1-NP, BaP, and pyrene. The results of spectral
assignment are given in Table I. It is noteworthy that 1-NP can be easily
differentiated from its parent compound, pyrene, by the SERS technique. The
results in Table I show that each of the three compounds can be unambigonsly
identified by several peaks. Recently we have successfully applied the SERS
technique to detect subpicogram levels of organophosphorous pesticides and
diesel particulate samples; the results of these studies will be reported
el sewhere^ t
CONCLUSION
Much of the research in SERS has been devoted to achieving a fundamental
understanding of the "giant Raman" enhancement. As the general features of
the enhancement effects continue to emerge, SERS should also become a powerful
tool for the analytical chemist. However, in spite of the great interest in
fundamental research of the SERS phenomenon, there has been few reports on the
analytical applications of this effect for trace organic analysis. Most of
the basic studies reported in the literature mainly dealt with samples at
concentrations between 10—^ and 10-^ M (i.e., well above the concentration
range of interest to analytical spectroscopists). In general the SERS studies
only involved specific surfaces, such as microscopically roughened electrodes,
and dealt mainly with highly polarizable small monocyclic molecules, such as
pyridine and its derivatives and a few ionic species. This study demonstrates
the analytical usefulness of SERS for the detection of a variety of organic
compounds using substrates that can be easily prepared for practical
applica tions.
The SEAS technique has several advantages for trace detection. The
procedure requires only a small amount of sample for measurement. Usually a
3-^L sample is needed for the measurement. Therefore, the absolute detection
limit for PNA compounds detected from a 10~^M solutions is in the nanogram and
subnanogram range. If we also take into account the fact that the laser beam
illuminates an area 1/100 smaller than the actual sample spot, the actual
655
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detection limits are only in the picogram range.
ACKNOWLEDGMENTS
These studies were carried out as applied development research within a
collaborative project, with M. C. Buncick, T. L. Ferrell, T. A. Callcott, E.
T. Arakawa, R. J. Warmack, and D. Bailey, sponsored by the U.S. Department of
the Army (IAG 3311-1450) to study the fundamental physical mechanisms
producing SERS. The quartz post substrates used in the studies were prepared
with the technical assistance of P. Enlow and M. C. Buncick, which we
gratefully acknowledge.
REFERENCES
1. R. K. Chang and T. E. Furtak, Eds., Surface-Enhanced Raman Scattering.
Plenum Press, New York. (1982).
2. F. Kerker, J. Chem. Phvs.. 62: 1812 (1975).
3. A. Wokaun, Phvs. Rev. B, 25: 2930 (1982).
4. 11. V. Gelboin and P. 0. P. Tso, Ed6., Polvcvc1ic Hydrocarbons and Cancer.
Academic Press, New York (1978).
5. G. Grimmer, Ed., Environmental Carcinogens: Polvcvolic Aromatic
Hydrocarbons. CRC Press, Boca Raton, Florida (1983).
6. T. Vo-Dinh, Room Temperature Phosphorimetrv for Chemica1 Analysis. J.
Wiley and Sons, New York (1984).
7. T. Vo-Dinh, M. Y. K. FHromoto, G. M. Begun, and R. L. Moody, Anal.
Chem., £6: 1667 (1984) .
8. J. P, Goudonnet, G. M. Begun, M. Arakawa, Chem. Phvs. Le11., 92: 197
(1982) .
9. M. C. Buncick, R. J. Warmack, J. W. Litter, and T. L. Ferrell, Bui 1. An.
Phvs. Soc.. 29: 129 (1984).
10. M. Meier, A. Wokaun, and T. Vo-Dinh, J. Phvs. Chem.. 89: 1843 (1985).
11. P. Enlow, M. Buncick, R. J. Warmack, and T. Vo-Dinh, Anal. Chem.¦ 58:
1119 (1986) .
12. M. C. Buncick, Ph.D. Thesis, to be submitted to the Department of
Physics, University of Tennessee, Knoxville, Tennessee.
13. C. M. White, Ed., Nitrated Polvcvc1ic Aromat ic Hydrocarbons. Hue thing
Publishers, New York (1985).
14. A. L.. Morrison, R, L. Moody, and T, Vo-Dinh, to be published.
656
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Table I Spectral Identification of a Three-Component
Mixture By Surface-Enhanced Raman Analysis
SERS Peaks
SERS Peaks
for Individual
Compounds (cm 1)
In Mixture
(cm-*)
Pyrene
BUJP1
1-NP2
342
337
339
409
407
406
444
441*
465
462*
481
479*
507
505*
53 0
529*
565
56 0*
594
591
5 90
635
632*
720
719*
801
804
800
824
820*
893
890
890
921
917
916
1050
1045
1046
1074
1081*
1127
1125
1127
1124
1176
1177*
1194
1189
1190
1224
1220
1224
1240
123 9
1249
1235
1277
1280
1278
1335
1328
1350
1351
1348
13 85
13 83
13 82
13 80
1420
1413*
1506
1501
1504
1500
1528
1584*
1524*
1607
1600*
1622
1625
1620
1615
^¦B(a)P = Benzo[a]pyrene
^l-NP = 1-iNitr opy rene
* Spectral Position uniqne to each component
657
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(Sjjun AjDJjiqjD) A1ISN31NI
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658
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8
SERS SPECTRUM
OF PYRENE
7
6
PIO
5
4
3
2
0
200 400 600 800 1000 1200 1400 <600 1800
RAMAN SHIFT (cm-1)
Figure 2: Surface-Enhanced Raman Spectrum of Pyrene on Quartz Post
Substrate.
-------
CARBAZOLE
1.7 ng
SILVER-COATED
MICROSPHERE
(0.364 fim
SPHERE)
¦4-
C
3
>»
L-
O
L-
>-
k-
o
CO
z
UJ
H
z
{/>
a:
UJ
CO
1000 1100
RAMAN SHIFT (cm-1)
Figure 3: Surftoe-Enhanced Raman Spectrum of Carbaiole on Silver-Sphere
Paper Substrate.
660
-------
8
7 -
to
E 6 -
>>
o 5 -
Lm
1 -
0 1 1
200 400
Figure 4
l 1 1 1 T
i—j—r
j I i I i I i I i I L
600 800 1000 1200 1400 1600 1800
RAMAN SHIFT (cm-1)
Analysis of a Complex Mixture by Surface-Enhanced Raman
Spectroscopy.
-------
A FLUX CHAfCER/SOLID SCRBENT SAMPLING SYSTEM FCtt
VOLATILE ORGANIC AIR EKISSICN MWIIORING FROM
HAZARDOUS S&STE LAM) TREATMENT SYSTEM: FIELD RESULTS
R, Ryan Dupont
Utah Water Research Laboratory, Utah State University
Logsn, Utah
A laboratory and field evaluation of a flux chamber/Terax'**' solid sorbent sampling systen
for the monitoring of volatile hazardous emissions from hazardous waste land treatment
systsns fcr air anission release rate (AERR) model verification is described. The
laboratory phase involved the investigation of chamber interior pressure development and
mixing conditions as a function of purge flow rate, Tenax1*' and Tenax^Vchamber compound
collection and recovery efficiency, sanpler manifold between-trap variability, ana Ttjiax^
treakttrougi volumes as a function of mass of contaminant collected. Field studies included
the evaluation of field blanks, field spikes, sample 'creaktlrougi results, trap manifold
variability, and temperature build-up within the chamoe* air spaoe and soil below the
sampler during sampling activities at an operating hazardous waste land treatment facility.
Laboratory results indicated that low purge flow rates (CI 1/min fcr flux chamber used in
t'nis study) are required to prevent pressure increases and subsequent emission suppression
within the 3ampl(r inless a oonstant volume ptrge pump is incorporated into sanpler design.
Ter-ax'TM breakthrough voiunes were found to be a strong function cf collected mass levels,
with observed field breakthrough data generally agreeing -with laboratory results. T'ne unda—
predicticr. of treakth-cugh volumes fcr a number of oompoinds emphasizes the need fcr
breaktfrougf. traps in field sampling using Tenax^. Chamber air temper atire increases were
greatly moderated through the use of sample" shading, however, model and measured results
indicate that 6.5 cm soil tor,per at ire, not chamber air tanperatire, should be used fcr
emission rate modeling.
Finally, field breakthrough, blank and manifold variability data suggest that ths flux
Chamber/Tenax^ systan is best suited fcr use under higi emission rate conditions, as
experienced during field sampling activities following waste application, due to its
susceptibility to background contamination.
662
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A FLUX CHAMBER/SOLID SCREENT SAMPLING SYSTEM FCR VOLATILE ORGANIC AIR EMISSION MONITORING
FROM HAZARDOUS WASTE LAND TREATMENT SYSTEMS: FIELD RESULTS
Introduction
The lass of volatile constituents from hazardous waste treatment, storage and disposal
facilities has received increasing interest with the passage of the 19S1' RCRA anaialT.er.ts
that require EPA to pranuligate air enission standards fcr such facilities within 30 rncnths
of the law's enactment. Volatile emissions fran such facilities are of concern frcm the
standpoint of potential health effects and the role these ccmpoinds may play in nunercus
photochemical reactions that take place in the lower atmosphere. Fcr land treatment
facilities, evaluation and quantification methods fcr volatile organic emissions are also
necessary to provide a comprehensive approach to the determination cf the ultimate land
limiting constituent under a given set of soil/site/waste conditions.
The wcrk described in this paper was mdertaken to evaluate the applicability of a
solid scrbent/isolation flux chamber sampling protocol that oould be used for the
quantification cf specific volatile organic air anissions fran soil surfaces following
hazardous waste application. The sampling concentration analytical methodology was evaluated
both on a laboratory and field scale at an active refinery land treatment facility to
determine its operating limitations and performance characteristics.
Ejcperirnental Methods
Solid Scrbent Evaluation
Althougi established solid scrbent collection and concentration p-ocedires fcr a wide
range of volatile hazardous constituents are available fran the U3EPA1 and the US Public
Health Service2, limited wor'< has been reported on their use in hazardous waste land
treatment emission measurements. Also, critician has been leveled against solid scrbent
concentration metrcds^>J as misuse of sampling crocedires Fas occurred in the past with
respect to quantification of scrbent collection, concentration, recove-y and breatftrrou^:
efficiency fcr specific canpounds of interest. When applying solid 3(3"bent collection,
methods to air emission measiranents from land treatment facilities, concern over ccrcpcuid
retention, breaktlrough volune and recovery efficiency becomes even mere critical than in
ambient air sampling due to the elevated levels of constituents released fran the soil
sirfaoe, especially irrmeciateiy following waste application.
Charcoal and Tenax^ were considered as possible sorbents fcr use in the soil emission
sampling system, however, consistent quantitative recovery of naphthalene fran the charcoal
at levels greater than 50S using carbon disulfide were not possible fcr mass injection
levels fran 15 tc 1COO ug'tube. Similar difficulties have been reported for the recovery cf
aranatics fran charcoal using a pentane solvent^. Because cf the interest in monitoring
naphthalene in subsequent labcratcry and field studies, charcoal was not used in further
sanpling system analyses and will rot be discussed firther in this paper.
Tenax^ Scrbent Callect 1 orVRecovery and Breakthrougi Evaluation. All Tenax^' scrbent
traps used in laboratcry canpomd collection/recovery studies were prepared according to
EMSL/RTP° and Research Triangle Institute? standard operating procedures for the preparation
of Tsrax^ cartridges fcr volatile organic air contaminant sanpling, Tenax1^ scrbent traps
consisted of 5 nn i.d., 10 cm leng stainless steel tubing loosely packed in the interior 8
on with 0.27 to 0.28 g of prepared All tech Associates, Inc., 60/80 mesh Tenax™ GO solid
scrbent material. Once picked, the traps were thermally descrbed fcr a minimun of 2 hours at
290°C to ensure the conditioning cf oolunn packing material aid to minimize background
crganic levels in the cartridges. A single trap from a lot of 20 was checked fcr background
contanination via thermal aescrpticn/CE-FID analysis. A cartridge was rejected and a lot was
reconditioned if backgroird contamination was evident. Once the cartridge tested as clean,
cartridges in the lot were placed in muffled Teflon lined screw capped cultire tubes. The
culture tubes were then placed in air tight metal containers and stored at 2 to i|«C until
needed. All Taiax^ scrbent tubes used in field measLTtrnents were prepared as described
663
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above, were Individually checked and were rejected If background contamination was evident.
Tubes used in the study were prepared no earlier than three weeks prior to their use to
accomodate the recommended tube atcrage time of four weeks.
Tenax™ recovery data were collected utilizing EMSL/RTP® standard operating procedures
fcr the spiking of Tenax^ cartridges with a known mass of an organic constituent utilizing
the flash vaporization technique. A heated Injector tube was maintained at approximately
300°C, and data were collected fcr compoind mass irijcctlon levels ranging fran 0.09 to 250
lag. Spikes for recovery/descrpticn efficiency experiments were prepared using a sariple
volime of 200 ml (purge flow of 40 ml/mln, sample time of 5 mln), the approximate
breakthrough volime of methanol. Breaktlrough analyses were conducted at scrbent tube
temperatures of 19~23°C aid 28-32°C using a purge flew rate of 200 ml/min, comparable to
that used in laboratory and field emission measurements, fcr sample durations yielding
sample volumes fran 1 to 24 liters.
Analysis of the Tenax™ scrbent tubes was oarried out using the Telenar LSC-1 Licp.rid
Sample Concentrator equipped with a modified trap oven to accommodate the Suttk'.O an scrbent
tubes using descrb and trap bake tenperatires of 2*jO°C and a desorb tine of 4 minutes.
Samples were desorbed into an HP 5880 Gas Chranatofyaph equipped with an FID detector . A 2
m long, 2 rm i.d. small bore glass colinn packed with SP-1200/1.75J Dent.one 3't on 100/120
Supelooport was used fa1 peak separation and quantification. The following (E conditions
Wire used throuigjiout tie study period:
I reenter Tenperatire-250 °C Detector T(iip0rature=25O °C
Cirrier Klc»#=35 ml/min
Oven Temperature Prog-aa Initial Tcmxratiro^°C
Initial Tim*^ mlnuLes Progran Rate 1=2°C/min t.o 60 °C, no hold tine
Ptx^-an Hate £=10°C/minute to 165°C, 20 minute hold time.
Laboratory Isolation Flux Chamber Evaluation
Tne use of an enclosed chamber far the measirsnait ol' gases released fran soil and
plant surfaces to been practiced to seme extent in the soil are) biological sciences but. has
only been recently applied to the investigation of volatile hazarcbus ar.issiocis from land
treatment facilities. An "emission isolation flux chamber" encloses a defined head space
above a cfcfined 3oil surface area to allow the collection and concentration of volatile
crganlcs emitted fran a soil surface following waste application. An organic-free purge gas
is introduced into the chamber at a loicun controlled rate to sweep volatile oontamirtints out
of the chamber fcr eollectloiV concentration by any means appropriate for the oontamlnanta of
interest. The flux chamber Investigated In this study was a modification of a desigji
developed for the llShPA Environmental Monitoring Laboratory, ],as Vegas, NV, by Radian
Corporation^10, and consisted of a 68.7 x 68.Y an squire exterior diirmsion (emission
surfaoe area- ^560 aii2), clear acrylic; double-duned skylight modified for isolation flux
sampling as shown in Figure 1. Tre acrylic double-dome Interior was lined with opaque,
adhesive Teflon tape to provide a nor-adsorbing, non-reactive Interior surface, and to
prevent contamination of the sampling system via out-gassing from the chamber interior.
Double-dcme construction, as well as the opaque lining, were incorporated into sampler
design in an effort to reduce the effects of incident radiation on heating within the
chambers in field monitoring studies. Teflon was used fcr all bulk head fittings and pirge
fps inflow find outflow lines. Bulk head openings were provided for influent and effluEnt
lines as well as fcr temperature and chanber interior pressure measurements. Flow
calibration was carried out using a l liter bubble tube flow meter and a glass aid Teflon
mlcrcrvalve flow controller. Interior pressure measurements were determined by meaTS cf a
Dwyer Magiehellc gauga reading +_0.5 inches water full-scale.
Chamber Pressure Development/Mixing Studies. The flow regime within the flux chamber is
of critical importance as component emission rate calculations are based on t!ie assumption
that emission measurenents from the chamber' effluent are representative of a
completely-mixed chanber volume^ 10. In addition, adequate flow and tirbulenoe must be
provided to assure rr> canponent concentration accumulation within the etiarnber that may
664
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affect the component' s flux fran the soil surface into the Iowa" atmosphere^»Ccxr.ter
to the desire for maximizing flew and turbulence within the flux chamber is the need to
minimize positive pressure development within the chamber due to the potential far anissicn
suppression and possible flux reversal during emission sampling. The i/npact of purge flew
rate on chamber pressure cievelopnait wss evaluated tl-rough the monitoring of chamber
intericr pressure (with respect to ambient) indicated by the Dwyer Ma^iehelic as a function
of purge flew dstsTTuned at the chamber effluent port. The chamber was sealed air ti^.t
with a Teflon ooated acrylic sheet, arid pressure determinations were made over a range of
purge flows fran 1 to 10 1/min as suggested in Radian protocol^*10.
Mixing within the flux chamber as a function of purge flow rate was evaluated using
standard tracer techniques. The flash vsporization apparatus described above was placed
up-stream of the flux chamber and was used to vaporize an acetone tracer. Chamber effluent
acetone vapcr concentrations wa-e monitored us ng an AID portable X equipped with a
protoicnizaticn deteetcr. Flow curves were evaluated utilizing standard procedures13.
Flux Char.ber/Scrbent Tube Collectior/Recovery Evaluation. Contaminant collection and
recovery efficiency for the combined flux chanber/solid scrbent sampling train was evaluated
with the flux chamber configured as described above fcr the nixing studies, with a five
position Tenax1** scrbent split-stream sanpiing systan placed in the effluent line- as
indicated in Figure 1. The solid scrbent tubes (sanpiing and tre=KtrrougR trace) were
connected to the chamber effluent line via a Teflon and glass constant flow, capillary
manifold with all connections made via brass cr stainless steel, Teflon lined Swagelok
connecters. Ths effluent ends of the scrbent traps were connected to a second glass
manifold to which a constant flew personal sampling puip, operated at 1COO ml/minute, was
connected. Compound recovery data using the flux chamber/scrbent tube sampling train were
collected in a Tanner identical to that explained above fcr the Tenax"' trap spike recovery
experiments fcr compound -nass levels ranging fron 0.5 to 90 ug. Sampling continued fcr
tfree theoretical chamber retention times to ensure representative sairpling of the chamber
vcIutk. Scrbent traps were analyzed as described above, and individual trap data we"e pooled
to indicate overall recovery efficiency, contarcinant breaktrrcush, and collection
variability between positions on the constant flow sanpiing manifold.
Field Isolation Flux Chamber Evaluation
Field sanpiing was carried out at an operating refinery lane treatment facility at
various time increments befcre waste application. (BBT), before waste application following
tilling (EAT), inmediately following waste application (WBT), following an initial tilling
(iuRT), and following a second tilling (VET). Ambient air, chamber air, 0.5 an soil and 6.5
cm soil temperature conditions were monitored with digital thermocouple thermometers during
sanpiing, with and without isolation chamber shading, to ascertain heat build-up and its
effect on measured emission rates.
Six isolation flux chamber/Tensx^'' solid scrtent sanpiing systems shown in Figure 1
(less the heated injector tube) were transported to the full-scale facility in the suimer of
1985 fcr field emission measurement and emission model validation studies. A constant
volume, hi$i capacity purge purp (2 to 6 1/min) was incorporated into sampler design to
allow desireahle higi purge rate and shcrt chamber residence tines, while at the sane time
(rinimizing flux chanber intericr pressure development and subsequent emission suppression.
A ttree position constant flow capillary manifold was used in field sampling, and sample
collection was carried out fcr a period of 5 to 15 minutes at a sanple collection rate of
200 to 350 ml/trap depending upon the absolute sample time in relation to waste application.
Scrbent tube breakthrough traps were utilized fcr all sampling events immediately following
waste application, and at various other sanpiing times for quality control purposes.
Field sampler operation entailed the initial systematic random placement of the six
sampling units in a 68.7 on x 68.7 cm grid location within the approximate 6 m x 183 m
application area. Once placed at a particular sanpiing location, all sanpiing during the
study was conducted at the same relative position to preserve sample spatial identity. Both
purge and sample punps were calibrated on at least a daily basis using a bubble tube flow
655
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meter. At the Initiation of sampling, each flux chamber was plaoed in the appropriate
location within the application area and was fcreed Into Ihe soil such that the Teflon lined
acrylic dome rested on and sealed the soil sirface. Purgs gfis and purge piunp flew were
Initiated and oontlnued fcr 15 minutes prior to sample collection to assure a
representative atmosphere within tie flux chamber diring sampling. The sorbent trap
manifold/sample pimp systan was opened to the chanber effluent line via a glass and Teflon
valve, and the manifold pimp was started, Initiating a sampling event. Cold packs wa'e
placed over the Tenax™ tubes in an effort to reduce trap tunperatires below the 30 to 3S°C
ambient temperatures which occirred during sanpllng.
Tenax™ scrbent tubes were randcmly selected fcr use at the various sanpl lng locaticri3
and sampling times during the field study. Following sampling, the traps were placed in
cultire tubes, and were maintained in air tight" metal oontai rxrs at 2 to ^°C at all times
prior to final analysis as per methods describee above. All field sorbent tube samples were
analyzed within six weeks of collection. Field blanks were obtained by exposing sorbent
tubes to ambient conditions fcr approximately 15 seconds (approximate time required fcr
placement of tubes in sampling manifold) before being stared and processed as other samples
for analysis.
Resul ts
Laboratory Isolation Flux Chamber Rvp.1uat.ion
Pressire Development Results
As reviewed by Dupont^1', the development of pressire inder tit; flux chamber ckring
pirging was fotrsd to be significant at pirge (lav rates as low as 1 1/min without an
effluent sampling manifold. Pressire increased rapidly at purge flows greater than 1 1/min,
reaching nearly 7 Inches of water with respect to the outside of the chamber at a pirge rate
of 6 1/mln. Because the Radian prctoool reoarmerids purge rates between 1 and 10 l/.nlri^O,
pressire increases should be quantified as a function of flow rate for the particular
chamber being used in anission sampling. Tf a sealed sanpllng chamter is utilized, purge
flows on the order of 1 to 1.5 1/min should be the upper pirge flow limit unless a constant
volutie sanpllng punp downstream of the sanpllng cliamber is used to provide' a means of
balancing chamber interior and ambient pres3ire.
Mixing Results
Became of the law flow rate necessary to minimize pressure build-up under the flux
chamber, concern was raised regarding the mixing characteristics of trie chamber at low pirge
rates. Canplutc-ml x conditions are assimed within the sanpl ing chamber whun using chamber
effluent concentrations for the estimate of surface flux rates, and flux chamber mixing
results were used to test this aasunption. Table I Includes indicator retention time
parameter ana index data frcm mixing studies obtained frcm flow cltvcs generated without
internal rrtocftanical mixing at pirge flaw rates ranging frcm 0.73 to 3-73 1/min. The decay
portion of all flew cirvea observed did not vary mere than 15* frcrn corresponding
theoretical complete-mix cirves, meeting suggested Radian protocol fir the use of flux
chambers fcr soil sirface emission measuranents1 °. Mixing conditions within the sampling
chamber are seen to be relatively insensitive to pirge flow rate based on calculated
retention time parameters and Mcrrll Tndex values. No traid in dispersion with purge flow
rate wa3 evident from the mixing indices used, and these results indicate that tlie
oomplete-inix aosirnptlon for- flux chamber contents appears to be valid, even at flow rates as
low as 0.73 1/mln.
Solid Scrbent Reeovery/Dcscrptlcn Efficiency Results
Constituent mass recovery data fran tre Tenax™ and Tenax™/chamber reoovery studies
fcr the sevan aremailc conipoiiids of Interest are discussed by Dupontll and are sinnarized in
Figure 2 along with field spike recovery data. Figure ? indicates the mean aid %%
666
-------
Confidence Intervals resulting fcr each compound for mass injection levels fcr Tenax^1 alone
of 0.1 tc 250 yg/trap, fcr Tenax-^/chamber recovery of 0.2* to 90 yg/trap, arc fcr field
blanks of 0.5 and 2 ug/trap. Te'.ax'^' mean reoovery efficiencies resulted in coefficients cf
variation under 10? fcr all cot poinds except naphtha! er.e(C.V.=-1. T enax^/ chamber aid
spiked Tanax^1 field trap data recovery represent a much wider range of variability than
with the scrbent tubes used alone. The variability associated with the Tmax^Vchamber
studies is attributed to oanponent lcsse3 within the sanpling unit, sampling manifold
betweerrtube variability, and purge flew/ scrbent tube/sampl ing flew variability during the
sanpling event in addition to analyses e-rors inherent in tu'oe descrpticr. and QC analysis.
Field spike variability is associated with sarple storage, transportation aid analysis
procedures, and is particularly apparent fcr banzeie aid naphthalene. Field reoovery values
were essentially identical to laboratory Taiax*^ recovery data fcr the mid-range boiling
point conpounds, ethyl benzene to cr xylene, and are not significantly different (cr-0.05) frar.
laboratory recovery efficiencies fcr all compounds due to the large variability in field
spike recovery data. Coefficients of variation were < 30? except fcr benzene snd
naphthalene, which produced C. V. values of 38$ and 69%, respectively.
Tanax"^ Breakthroufjn Results
Results of laboratory breakthrough studies are shown in Table II and are expressed as
S3fr.ple volume in liters/0.28 g Tenax™ at a given compound mass level fcr 50% or 90%
retention of the said mass on the first trap of two traps Ir. series fcr a range of mass
injection levels fran 1.1 to 120 ug/tube at 19~23°C and 28-32*0. These values were generated
from linear least-squares regressions of all collected breakthrough data fcr benzene and
toluene which yielded regression coefficients greater than 0.870. All other ocmpouids did
not breakthrough in sufficient quantities to allow development of breakthrough volume
predictcr equations ever, with 120 ug injection masses and 21 1 collection volumes. A number
of references report data fcr breakthrough volume fcr benzene, tolucre and ethylbenzene
utilizing Tenax™ sorbent tutes'5.16 ^ indicated in Table II. Reported data do not
adequately address the effect mass tes on breakthrougn volume. Ur.de- conditions of high
volatile oenstituent .thss loadings to the scrbent tubes, breakthrougn volunes may be greatly
overestimated based on current EPA sailing protocol1*3.
Field fcreakthrough data shown in Table II were generated frar. linear and second order
polyncfual recession analyses, all of which were significant at the 95? confidence level.
Field data represent a 1.31 1 sample volume which resulted in total collected mass levels
much higher than evaluated in labcratcry studies fcr benzene (>900 ug) and toluene (>1550
305 at 120 -jg
collected} at a 1.3^ 1 sample volume which was ret observed in laboratory studies even at
31 °C collection temperature.
Fran results cf this study, for enission measurement sanpling frcm land treatment
sources fa' which XI5 pg are to be expected during sampling, a 500 to 100C ml sample
collection volune is reccrtmesided to ensure mini,tun (< 10?) breakthrou#i of the most volatile
compounds being collected.
Field Blank Results
Blank scrbent tube cfeta collected throughout the field study are presented ir. Table
III. These data are divided into blanks collected befcre waste application and these
collected following waste application due to the method of blank trap collection as
described above. As others have indicated4''3, occurrence of a number of very high levels of
benzene and toluene occurred throughout the blank collection event. A number of these high
blank values were attributed to GC analysis techniques which were corrected trrou^n post
analysis tar.peratire prog-arming to rid the coluircrv'injectcr of high residual contaminant
masses between samples. Hign benzene and toluene blank mass levels we-e traced to nign
level waste before tilling samples run just prior to these blank tubes, and these values
B67
-------
wsre riot Included in field data blank corrections. Blank correction vslies generally
decreased as compound vapcr preasire Increased, and the levels Increased during the waste
application period before slowly falling to prewaste levels by tiie first tilling after waste
application event.
Laboratory and F'ield Trap Manifold Variability
Laboratory manifold variability, expressed as ths relative standard deviation (RSD) of
collected mass within a manifold group, was found to range fran 1M to 20% fcr all compounds
lnvestigited. Field data variability was much greater than laboratcry data and appeared to
be significantly affected by mass collection level. During sampling events when the highest
mass of contaminants were being emitted, I.e., just following waste application, manifold
variability approached those values observed In a controlled laboratcry setting fcr all
compounds (RSD-22 to itfJ?) except naphthalene (RSCMG'tJ). Prlcr to waste application (RSD=fi3
to 140%) aid after tilling (RSD-30 to 126$), acrbent tube characteristics and backg-xxjid
oontaninatlcn beccrae significant for all ocmpomds, retiring a strict QA/QC program to
ens ire adeqiately prepared and stored Tenax^ tubes.
Temperatire Effects During Field Sampling
Temperatire data collected diring sampling events following waste tilling are shDwn In
Figire 3. Significant temperatire differentials, >^0°C, with respect to ambient temperatire
were observed In flux chamber air dirlng midday when the sanpllng units were not shaded.
Shading using simple Inclined plywood sheets was successful in reducing chamba^ air
temperatires by 20 to 25°C dirlng midday, significantly reducing air phase temperatire
g"adlents. Shading had a much smaller effect on soil tenperatires as would be expected,
producing only a 5 to 10°C reduction in 0.6 cm soil differentials, and only 1 to 2°C
reductions at the 6.5 cm level with respect to field plot soils not covered with sampling
chambers. Results of modeling activities correlating field data with Thibodeaux^Hwang land
treatment emission model predictions11 suggest that the 6.5 on soil temperatire depth is
representative of mean 3011 temperatires occurring during waste volatilization. Tte use of
temperatire data at this depth fa- parameter temperatire corrections has resulted in
measired and predicted emission values consistently within a facta1 of 2 to 10 for most data
collected diring the field sampling described in this paper.
CONCLUSIONS
Baaed on the data and results presented above, the following conclusions were reached
regarding flux chamber/solid scrbent sampling for soil surface emission measirasents:
1. Tenax-^ is recommended far land treatment mission sampling due to its
effectiveness fcr the ocmpounds of Interest In this study and to its performance within the
flux chamber sampling system.
2. The Isolation flux chamber sampling system must be operated at lew p^rge flew rates
(<_ 1 i/min fcr the 22.25 1 chamter used in this study), if ro purge pump Is utilized, to
limit excessive pressire build-up and potential emission suppression. At these low flow
rates, canplete-mlx behavior is exhibited within the flux chamber, allowing for
representative a-ab sampling of a iniform air apace meter the (tenter.
3. Tenax™ breakthrough vol lines were found to be a strong function of col-lected mass
level as well as temperatire. When iBing Tenax™ fcr soiree emission measirements, it is
highly recommended that reported breakthrotigh volune315.l6 tx_. critically evaluated for the
mass loading and operating conditions expected in laboratcry and/or field emission
measirement applications. It is firther suggested that "in sampler" data should be
collected to allow the quantification erf1 specific "as usecf collection and recovery
efficiency values.
'I. Field breakthrough data generally ax-related with laboratory results, however,
laboratory under~ prediction of ethyl benzene, rrr and crxylene breakthrough vol lines at low
mass levels stresses the requirement fcr breakthrough traps wlien using Tenax^ fcr field
sanpling.
668
-------
5. Flux chamber air ternperatire differentials wane not obea-ved to artificialiy affect
emission rates and were fouKl to be significantly reduced through tte use cf sanpler
shading. Measu-ed mission rates appear to be predictable using parameter temperature
corrections based cr 6.5 cm soil depth data.
6. Results of field breakttrcugi, blark and manifold variability data suggest that the
flux chamber/solid 3crbent system is best suited for high emission rate conditions, I.e.,
immediately following laid treatment waste application, but requires diligent QA/QC
procedures to minimize background oontamination to ensure representativeness during lew
emission rate events.
DISCLAIMER
Althou^i the irfcrniaticfi in this paper fas been funded in part by the US Envirormaitai
Protection Agaicy inder Cooperative Ag-eenent CR810999, it has not been subject to Agency
peer review and does net necessarily reflect the view's of the Agency, therefore no Agency
endorsanent should be inferred.
References
1. USEPA, "Characta"i2ation of hazarcteus waste sites-a methods manual: Vciune II.
Available sampling methods,'' EPA-SOQ/M-SBKWO Cl98^).
2. US Public Health Service, "NICSH manuals of analytical methods," 2nd Ed.,
Department of Health and Hunan Services, Volunes 1 througi ^ (1978).
3. Walling, J. F., "The utility of distributed air valine sets when sanpling ambient
air losing solid scrbents," Atm. Env. *8(4):855 (19BM).
4. Jarke, F. H., "Aisbient air monitoring at hazardous waste facilities," Presented at
the 78th Annual Meeting cf the Air Pollution Control Association, Detroit, MI. Jine 16-21
(1965).
5. Tiranons, K. D., D. Karlesky, E. Johnson, arid I. M. Warner, "Desorpticn
efficiaicies cf vapcr phase polynuclear aromatic compounds on solid adsorbents,"
DOE/ER/601 C0"3 (Decanter 1965).
6. USEPA, "Standard operating procedure for the preparation of clean Tcyiax'*'"1'
cartridges," E>SL/RTP-S0P-2CK)13 (198;).
7. Research Triangle Institute,"Standard operating procedure fcr Tenax^ cleanup and
preparation of Tsiax^ cartridges fcr use in the collection of crganic compounds,"
an/ACS- SCP-32G-OC1 (1983).
8. USEPA, "Standard operating proceAre fcr the preparation of TaTax™ cartridges
containing known quantities cf crganics using flash vaporization," E^EL/RIP-SOP~1•^>-012
(1981).
9. Schmidt, C. E., and W. D. 3alfour, "Direct 51s measiranmt techniques .and the
utilization of emissions data fran hazardous waste sites," Proceedings of the 1983 ASCE
National Specialty Corfa-ence on Envircrmental Engineering, Boulder, CC, July 6-3, pp
690-699 (1983).
10. Balfour, W. 0., R. M. Ekluid, and S. J. Williamson, "Measurement of volatile
organic emissions fran surface contaminants," Proc. of the National Conference on Management
of Uncontrolled Waste Sites, Washington, D.C., pp 77_3C (1983).
*1. Thibodeaux, L. J., and S. T. Hwang, "Landfarming of petroleun wastes ntxieling the
air mission problem," Env. Process 1(1):J42 (1982).
669
-------
12. Hwang,3.T., "Model prediction of volatile anlssicne," Env, Progress ij(2):l4l
(1985).
13. Marske, D. W., and J. D. Boyle, "Chlcrlne contact chamber desigra field
evaluation," Water and Sewage Works 120(1):?0 (1973).
1't, Dupont, R. R., "A flux chamber/sol Id scrbent system fcr volatile organic emission
measurements from land treatment facilities," Paper 86-21.6, Presented at the 79th Annual
Meeting of the Air Pollution Control Association, Minneapolis, MN (Juie 1966).
15. Pelllzzarl, E. D., aid L, Little, "Collection and analysis of pu-geable organlcs
emitted fran wastewata" treatment plants," EPA-600/2-80-017 (1080).
16. IJSEPA, "Standard operating procedire fcr sanpllng gaseous crganlc air pollutants
fcr quantitative analysis using Tenax™," EMSl./RTP-S0P--f:M)-016 (1982).
670
-------
Table I. Rux Chamber Mixing Retention Time Parameter Data
Theoretical
Flow Rate Retention Time Wcr l
iml/Vnin)
T (min)
Ti (min)
Tm (mm)
Ta (mm]
Ti/T
Trn.T
TaT
T10 (min)
T90 (min)
Index
732
30 4
1.28
6.67
30.44
0 04
0.22
1.00
7.51
83.39
M. 1 7
732
30.4
0.55
5.65
14.91
0 02
0 19
0.49
3.82
30.65
8 02
1650
13.5
0.40
4 16
8.97
0.03
0.31
0.67
2.62
17.87
6 62
1650
13 5
0.24
2.00
8.35
0 02
0 15
0.62
2 16
17.C7
7 90
2727
8.2
0 18
0 44
4.73
0.02
0.05
0.58
0 88
10.39
11.81
2727
8.2
0.10
0.19
4.G1
0.01
0.02
0.56
0 60
10.S9
17.82
2727
8 2
0 40
0.92
8.78
0.05
0 11
1.08
1.10
20.50
18.64
2727
8 2
0.14
0.49
4.68
0 02
0 06
0.57
0 54
10 92
20.22
3726
6.0
0 30
0 46
3.78
0.05
0.08
0 63
0.66
3.42
12.76
3726
6.0
C.10
0.19
3.04
0.02
0.03
0.51
0 52
6.32
13.12
3 7? 6
6 0
0.40
0.68
4 12
0 07
0.11
0.69
0.76
9 35
1? 30
3726
6.0
0 45
0 86
7.30
0 08
0 14
1.22
' .06
15.98
1 6.02
• Ti « Time to initial tracer detectton
• Tm « Time to peak concentration of tracer
• Ta - Time to centred of area ^ average reti
• TlO - Time to 1C% area under tracer curve
• T90 » Time to 50% area under tracer curve
» Mornl Dispersion Index -> T9C'l 10
Table II. Tenax™ Sorbent Tube Breakthrough Volumes ;is a Function of Temperature* and Mass ln;ectioo Levrl
28 32 "C (1S-?3*C) Laboratory Tenax Breakthrough Volumes (!) for a Given Percent Recover/ or. First Trap ol Two Trap Scios
Mass
Level
Benzene
Toiuone
Eidyibenzena
p-Xviene
m-Xyrere
o-Xylene
Naohthaionn
(Literature 32'C(21"C)]t
3.4(6.9)
15 5(31.2)
43.3(88 2)
120.0 ug
90%
0.28(0.20)
0.20(5 1)
11 3(25.0)
12.1(32.5)
11.0(25 S)
12.8(2" C)
>>24(>>24)
50%
0.60(3.2)
2.50(14.7;
22.2(110.6)
22.5(150.0)
24.1(115.1)
25.4(9'.a)
»24(»24)
60.0 ug
90%
0.71(1.9)
0.22(>24!
14.3(»24)
14.9(»24)
15 ?f>>24)
14 9i>>24)
*:>?4(:>>24)
50%
1.8(4.9)
6.0(»24)
24 9(»,24)
25 4(»24)
27.1 (>>24)
23.6'»24)
>>24{>>24)
8.5-15.0 jig
10-15.3 ug
9.7 ug
13.4
29.8 .ig
11.2 ug
18.0 >ig
90%
1.2(3.0)
17.4(25.4)
»24(>>24)
»>24(>»24)
>>2*J(>>24)
»24(»24)
>>24f»24)
50%
3.5(7.8)
33.2(49.5)
>»24(»24)
»24(»24)
»24{»2*)
»24(»24)
>>24(»24|
1.8-2.0 iig
2.2 Mg
11 MS
1.8 jig
4.2 ug
1.9 tig
2.4 ug
90%
4.5(5.3)
19.2(>>24)
»24(>>24)
>>24(>>24)
>>24(>>24)
>>24{>>24)
»24(»24)
50%
13.7(28.1)
40.4(»24)
»24(>>24)
»2A(>> 24)
>>2«S(>>24)
»24(»24)
>>24(>»?4;
F ittid Percent Tenax Breakthrough Data *cr Ambient Temperature®25.4-31 4 'C , Trao Temperafure-;2G'C
Mass
%
Breakthrough
Level (pg)
Benzene
Toluene
Elhylbenzena
p-Xylene "i-Xylene
o-Xylene hbohiha;
1600
..
49
1000
70
is
-
..
7 0 0
74
9
-
_
-
450
51
4
«
..
--
200
29
3
-
17
-
1 20
21
3
33
1 1
60
">6
3
11
0 7
14
1 5
12
4
3
0 5
3 0
t Breakthrough volumes shown are those reported by Reference 15 representing a 50% mass breakthrough.
671
-------
OacVground
Wjsle Bofore Tilling
Nul IndudingProbJem
Traps
Waste Afler Tilling
wIc A1tiunil l/ijeclion
HaJf-Hule Septum
'tMl
Pu*o« inflow
lledted Injector Tube
T empcrtlure
Measurement
Capillary
Flow Controller*
Figure I Flash vaporiz-ilion/llux cruniberfsolnl «,orh«nt tube lim^liny ayalem
B72
-------
Compound
Naphthalene
60-5^;9fi jis™*tt\
77.6±3.8 1 1
87.3+9.4
97.3+1.9
o-Xylene
irnmmrnmmmimmmMm
81.5+7.8
93.4
m-Xylene
75.1+8.4
p-Xylcne
89.3±15.2
90.5+1
91.4 + 14.1
90.6+1
Etnyoenzene
94.0±12.5
96.0±2.4
[126.6=38.6
io:uena
m
0±11.6
87.0±2.6
136.7±54.4
Tenax Recovery
Efficiency Data
m Tenax/Chamber
Recovery
Efficiency
~ Field Spike
Tenax!M Recovery
Cata
Benzene
¦r 1 1 f i 1 i-
0 20 40 60 ao 100 120 140
Recovery Efficiency (Mean %±95% Confidence Interval)
Figure 2. Laboratory and field Tenax™ recovery efficiency data
T CO
Ambient
Chamber Air AT
(NOT Shaded)
Chamber Air AT
(Shaded)
1/4 In A T {NOT
Shaded)
1/4 in AT
(Shaded)
2 in Soil AT
(NOT Shaded)
900 1100 1300 1500 1700 1900 2100 2300
Time of Day
Figure 3. Field ATemperature Profiles With and Without Shading (aT
based on values at start of chamber purge)
673
-------
APPLICATION OF CAPILLARY GAS CHROMATOGRAPHY/
MASS SPECTROMETRY TO THE VOLATILE ORGANIC
SAMPLING TRAIN (VOST) ASSAY TO FACILITATE
CHARACTERIZATION OF PRODUCTS OF
INCOMPLETE COMBUSTION
Thomas A. Buedel
Dr. Joan T, Bursey
Radian Corporation
Research Triangle Park, North Carolina
Robert G. Fuerst,
Thomas J. Logan ,
M. Rodney Midgett,
U.S. Environmental Protection Agency
Environmental Monitoring SystemE Laboratory
Research Triangle Park, North Carolina
The extensive characterization of Products of Incomplete Combustion in
Volatile Organic sampling train samples is greatly facilitated by
improving the chromatographic resolution producing quality mass spectra
that are easier to characterize. Cryotrapping and the substitution of a
wide bore, thick film, fused silica capillary column for the packed
column (6' x 1/8", IX SP-1000 on Carbopack B) now required is the
easiest and most economical improvement.
(K) dD
This procedure desorbs the contents of a Tenax or Tenax /charcoal
cartridge through a purge and trap apparatus and onto a sorbent trap.
Thi6 sorbent trap is de6orbed onto a nickel trap that is cooled with
liquid nitrogen to approximately -198 C and rapidly heated to
approximately 225 C. Approximately 2 mL/min of carrier gas sweeps the
contents into a wide bore, thick film, DB-5 fused silica capillary
column that is programmed and eluting compounds are detected by mass
spectrometry. Further experiments are scheduled to evaluate the
reproducibility of measurements obtained with the capillary system, a
well as compound recovery. If reproducibility and recovery are
acceptable, a field test i6 scheduled for spring.
674
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INTRODUCTION
Background
The environmental scientific community is interested in the
characterization of Products of Incomplete Combustion (PICb) in Btack
emissions. ^ The current Volatile Organic Sampling Train (VOST)
methodology analyzes samples of stack gaBes that are acquired on Tenax
and/or Tenax/charcoa1 cartridges. The cartridges are analyzed by
thermal desorption with a subsequent purge through water, concentration
of organics on a sorbent trap, and then introduction into a gas
chromatograph/masB spectrometer (GC/MS) system as outlined in EPA
Method 624. The analytical separation performed on the GC employs an
1/8 in z 6 ft column packed with 1Z SP-1000 on Carbopack B. If the
sample is not extremely complex and the level of products of combustion
(POCs) does not saturate the mass spectrometer (MS) detector, then the
quantitative analysis of the principal organic hazardous constituents
(P0HC8) is straightforward ar.d a qualitative analysis of non-target
compounds may be performed on chromatographica 1ly resolved peaks with an
acceptable level of confidence. If the sample is complex and the level
of POHCs nears saturation of the MS detector, then the high level of
background may interfere with the compound identification. A PIC peak
may easily coelute with the POHC compound because a packed column
chromatographic peak is typically very broad (20-45 seconds).
Identification is complicated when peaks coelute. The extensive use of
background subtraction for PIC identification, by manual interpretation
or by computerized library search, is time consuming and requires
considerable experience and skill. Improvement of the analytical
process by upgrading the chromatographic resolution would produce a
better quality mass spectrum and a higher level of confidence in their
identification. The use of a capillary column would provide this higher
chromatographic resolution. The narrow peaks (typically 8-14 seconds)
would decrease the chances of compound coelution and improve the level
of confidence in compound identification. The capillary column is also
capable of a shorter analysis time while retaining a sample capacity as
high as ~500 ng on column.
Ob jec t ives
The objective of this program was to develop a working method of
introducing a VOST sample to a capillary GC column in order to improve
the chromatographic resolution and thus to facilitate characterization
of PICs. Analytical precision and recovery had to be verified with any
alteration of the VOST methodology and they could not be sacrificed for
the additional chromatographic resolution.
EXPERIMENTAL METHODS
We approached this assignment with a two-part plan. The initial
development was performed on a gas chromatograph/flame ionization
detector (GC/FID) to keep costs at a minimum while experimenting with
the assembly of the apparatus, program times on the Purge and Trap
Concentrator (P-T) and temperature programs. The second portion was
performed by GC/MS as described in the VOST protocol with the technology
developed on the GC/FID.
675
-------
GC/FID
The GC/FID portion of the program was performed using a Tekmsr LSC-2
concentrator, a Nutech 320 Cryotrap/Nutech 320 Controller, a Varian 3700
GC equipped vith a FID, and a Varian CDS 401 Data System. The LSCji2 is
a F-T unk equipped vith a "trap" column that may contain Tenax ,
Carbopack , SP-2100, charcoal, or some combination of these sorhents.
The effluent of the trap is directed into the Nutech 320 Cryotrap via a
heated stainless steel transfer line.
The Nutech 320 Cryotrap includes a six-port valve containing a
stainless steel nickel-coated trap loop (SSNCTL). The 320 has a cooling
cycle controlled by bleeding liquid nitrogen (LN) into a reservoir
surrounding the SSNCTL and haB a heating cycle controlled by a
Nutech 340 Temperature Controller that pulse heats the SSNCTL from
-198°C to ~240 C in ~1 minute. The Nutech 320 is operated by setting
the valve to the Desorb position and freezing the SSNCTL to —196°C,
while the LSC-2 i6 deaorbed vith the effluent being passed into the
Nutech 320 and through the SSNCTL vhere all compounds will freeze,
venting only N^ carrier gas to the atmosphere. When the l.SC-2 has
finished the desorption cycle, the Nutech 320 valve is switched to the
Sample position and the trap iB pulse heated to 240 C by activating the
Nutech 340 Temperature Controller. The heated SSNCTL volatilizes the
trapped compounds which are swept to the column head via a diverted CC
carrier gas.
The DB-5 thick film, 0.32 mm x 30 m fused silica capillary column
receives the organic compounds vaporized from the Nutech 320 through a
stainless steel transfer line via a zero dead volume fitting. A DB-5
vas selected for the program because it is a nonpolar, bonded silicone
phase that is very resistant to solvent, has an operating range of -60 C
to 320 C, high resolution capability and its 0.32 mm I.D. x 30 m length
allows a carrier flow rate to maximize resolution while minimizing
analysis time. The thick film (1.0 urn) is excellent for highly volatile
compound analyses, exhibits maximum sample capacity and raises the
elution temperature of compounds for maximum separation and retention of
low boiling compounds. The effluent end of the capillary column iB
connected to the FID of the Varian 3700 Model GC.
The Varian 3700 GC/FID was operated with the injection port heated
to 220 C and the detector to 300 C. All analytical data were recorded
by the Varian CDS-401 Data System which plots the chromatogram and
integrates the chromatographic peak areas.
GC/MS
The Tekniar LSC-2 and the Nutech 320 were transferred to the GC/MS
Laboratory upon completion of the development work on the GC/FID and
connected to a Finnigan 4500 GC/MS. The capillary column was connected
to the Nutech 320 as before but the other end was inserted directly into
the MS source. The GC/MS system is controlled by an INCOS Data System
which is used to record and process data. A summary diagram of this
system is shown in Figure 1.
RESULTS
Initial experiments optimizing the the analytical conditions using
GC/FTD, yielded well resolved chromatographic peaks of reproducible
areas with linearity over the range of calibration.
676
-------
Purge and Trap Apparatus
The P-T apparatus was connected to the cryotrap^Jby a heated
transfer line and fitted with a Method 624 trap (Tenajf™/SP-2100/silica
gel). The purge time was 11 minutes, trap desorb time 3 min at 180 C,
and trap bakeout time 12 min at 200°C. The initial GC analyses failed
to produce good analytical results ao the purge time and trap desorb
times were adjusted. Although moisture did not efficiently block the
cryotrap, it was of sufficient quantity to extinguish the FID. The trap
was replaced with an all-Tenax trap in an attempt to alleviate the
problem. The purge time was tested as low as 5 minutes which did not
purge compounds from the water and as high as 22 minuteB which did not
improve compound recovery. Increasing the trap desorb time to 5 minutes
increased signal level by 1.5-2 times, but when desorb time was
increased to 7 minutes or 10 minutes the signal level did not increase.
2
A "dry purge" cycle was also tested. A "dry purge" is a technique
performed after the carrier gas has passed through a purging vessel
containing 5 ml E^O for 11 minutes. The carrier gas is then diverted
past the purging vessel and directly onto the LSC-2 trap. The dry purge
eliminates the possibility of trapping excess moisture from the purging
vessel on the LSC-2 trap and helps to remove any moisture already sorbed
by the LSC-2 trap. The dry purge cycle had no effect on the Bignal of
the compounds for this portion of the experiment. The final parameters
were:
Purge Time: 11 min. 40 tal/min ambient temperature
Desorb Time: 5 min. 1.5 m 1/min 180 C
Gas Chromatography
The GC program was selected to allow analysis to begin at room
temperature. The initial temperature of the GC oven was |et at 35 C and
held for 3 minutes, then programmed to 225 C at 8 C min and held at
225 C for 15 min. Varying the initial hold times from 1 minute to
5 minutes did not improve peak shape or resolution. Changing the ramp
rate to 6 C/min reduced the peak resolution and lengthened retention
times but a ramp rate of 10 C/min did not improve the chromatography.
The final program was:
Initial Temperature
Ramp rate
Final Temperature
Injector Temperature
FID Temperature
Flow Rate
35°C for.3 min
8°C min
225°C for 15 min
200°C
300°C
1.5 mL/min
GC/FID Results
Precision and linearity of the method described above, when tested
with a mixture of benzene, toluene, ethylbenzene, a-xylene, m_xylene,
and ^.-xylene, suggest that transfer of the system to the GC/MS was
feasible. This may be seen in the coefficient of variation in Table I
and by correlation coefficient in Table II.
677
-------
Gab Chromatography/Mass Spectrometry
The purge and trap/cryotrap apparatus was fitted to the GC/MS and
operated under conditions identical to those used for the GC/FID
analyses. A series of experiments was conducted to determine the best
analytical trap composition and the best F-T methodology. Table HI
outlines a summary of these experiments and their results. The best
trap composition is 10Z charcoal and 90Z Carbotrap by weight. Carbotrap
is graphitieed carbon black with a particle size distribution of
20/40 mesh and is very hydrophobic. The dry purge of seven minutes
removes most of the moisture sorbed by the charcoal and allows maximum
sensitivity of all Method 624 compounds including gases (Figure 2).
The analytical parameters for optimal analytical performance is as
follows:
Sample Cartridge Desorb
Temperature 180°C
Time 11 min.
Purge and Trap
Purge Time: 11 minutes
Dry Purge Time: 6 minutes
Purge Flow: 40 mL/min (@20 psi head pressure)
Purge/Desorb Temp.: 25°C/180°C
Desorb Time: 3 minutes
Cryotrap
Sample Temp.: -198°C
Desorb Temp.: 225°C
GC/HS
Injector Temp.: 225°C
Transfer Oven Temp.: 225°C
HS Manifold Temp.: 100°C
Ion Source Temp.: 150°C
Scan Rate: 1.0 sec/scan from 35 AMU to 265 AMU
GC Oven Program
Initial: 35°C 3 minutes
Program: 8 C/ninutc
Final: 220°C 5 minutes
CONCLUSIONS
The purge and trap/cryotrap/capil lary column/MS system i6 workable,
and would require a minimum of capital and time to add to the presently
accepted VOST methodology. The cryotrap used for this task was manually
operated but there are 6emi-automatic and automatic traps commercially
available to simplify the analytical procedure. Use of a cryotrap added
a few minutes to the initial portion of the analysis, but the capillary
column required approximately twenty minutes less per analysis than che
SF-1000 packed column (Figure 3, Figure 4). The peak resolution of the
capillary column made the identification of compounds easier with less
chance of coelution and uiis ident i f ica t ion .
678
-------
The capillary vill alio allow a qualitative examination of
compounds that elute beyond the VOST range of interest (<30 C and
>100°C). Semi-VOST compounds (b.p. > 100°C) for example vill elute
from the capillary column that would never elute from the SP-1000 packed
column. This finite elutioo time of compounds with boiling points
>100 C may help to screen VOST samples for compounds that may be
present in an accompanying Semi-VOST or Source Assessment Sampling
System (SASS) type test; the only restriction being what compounds are
sorbed and desorbed by Tenax and charcoal -
Further method development is underway to maximize the sensitivity
of this procedure. This will include studying dry purge efficiencies
and minimum detection limits. A field test is scheduled for June, 1986
to collect samples to evaluate the capi1lary-VOST method with
incinerator emission samples.
ACKNOWLEDGMENTS
This 6tudy was supported by the U.S, Environmental Protection
Agency, Environmental Monitoring Systems Laboratory (EPA-EMSL) under
contract no. 68-02-4119.
REFERENCES
1. Earl M. Hansen, "Protocol for the Collection and Analysis of
Volatile POHCs Dsing VOST," EPA Report 600/7-78-054, March 1978.
2. Eric Johnson, Finnigan Corp., Sunnyvale, CA, private communication
(1986) .
3. Earl M. Hansen, "Protocol for the Collection and Analysis of
Volatile POHCs Using VOST," EPA Report 600/7-7 8-054, March 1978.
4. Ibid, Section 3.1.
G79
-------
TABLE I. PRECISION OF COMPOUNDS (THREE INJECTIONS BY GC/FID
(100 ng each compound)
Compound
Average Raw
Area Counts
Standard
Deviation
Benzene 29382
Toluene 32602
Ethylbenzene 31700
tt- and ^-Xylene* 64930
ft-Xylene 33727
2686
1525
155
263
887
Coefficient of
Variation
9.1
4.7
0.5
OA
2.6
~These compounds co-elute,
TABLE II. LINEARITY OF COMPOUNDS (THREE POINT CURVE) BY GC/FID
Compound
Benzene
Toluene
Ethylbenzene
4
a- and ^.-Xylene
a-Xylene
Correlation Coefficient
.9993
.9962
.987 9
.9931
.9893
~These compounds co-elute.
680
-------
Table III. ANALYTICAL TRAP EXPERIMENTS
Xrflp—Composition
Tenax®
fi> • . .
Tenax with dry purge
(£),
Tenax /Charcoal
®
Tenax /Charcoal with dry purge
(2)
Tenax /Charcoal with dry purge
6) A)
Carbotrap /Tenax
CarboCrap
(5)
Tenax /SP-2100/SP-1000
65* Carbotrap/352 Charcoal
90Z Carbotrap/107 Charcoal with
5 ainute dry purge
Egfltflt
High moisCure - no compounds of
b.p. 30°C
Poor chromatography detector
High moisture
Poor chromatography
High moisture; poor chromatography
No compounds at b.p. 30°C detected
No compounds at b.p. 30°C detected
Two of four compounds at b.p. 30°C
de tec ted
High moisture
- all compounds detected
- good chromatography
- low moisture
681
-------
/ NUTECH \
' 340
Tamparatura
\Controll«r/
'5.0 Qrada
Helium
Carrier Qaa
Syat<
Data
NUTECH 320
Cryotrap
TEKMAR L8C-3
Puraa and Trap
Sampla Daaorbar
Fhinlgan 4500
Qaa Chromatograph -
Maaa Spaetromatar
Figure 1. Schematic of GC/MS analytical apparatus.
-------
3N31XX"d * 3M31AX~N
301 3N31AH13W
T
T
6B3
-------
n
3NM«-d T 3N31M-*
m
3CIH01HD 3M31AHX3N!
684
-------
EVALUATION OF THE SEMI-VOST METHOD FOR
MEASURING EMISSIONS FROM HAZARDOUS WASTE
INCINERATORS
Joann Rice, Denny Wagoner, Robert McAllister,
and James Homolya
Radian Corporation
P.O. Box 13000
Research Triangle Park, NC 27709
John Margesoo, Joseph Knoll, and M. Rodney Midgett
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
A field evaluation study was completed which assessed the performance of
the Semi-Volatile Organic Sampling Train (Semi-VOST) methodology in
measuring the concentrations of principal organic hazardous constituents
(POHCs) that are emitted from hazardous waste incinerators. The
Semi-VOST method is used to measure POHCs with boiling points greater
than 100 C. Semi-VOST method performance characteristics pie evaluated
by previous experimental work performed in the laboratory. Three POHCs
examined in the laboratory (toluene, chlorobenzene, and
1 ,1,2,2-tetrachloroethane) were selected as spiking compounds to
evaluate method precision and bias under field conditions. In order to
determine compound retention volume of the XAD-2-' resin module,
distributive volume experiments were performed.
Following the field study, additional laboratory experiments were
performed to investigate the analytical methodoloojr used for Semi-VOST
and possible interactions of POHCs with the XAD-Z^ adsorbent resin.
Four compounds with poor or variable recoveries in the laboratory
evaluation were selected: aniline, pyridine, phenol, and resorcinol.
In addition to the discussion of experimental results, several
recommendations are presented in order to address elements of the
evaluation and Semi-VOST methodology requiring further experimentation.
685
-------
INTRODUCTION
Resource Conservation and Recovery Act (RCRA) requirements for
vaete disposal by incineration are that hazardous waste incinerators
have a destruction and removal efficiency (DRE) equal to or greater than
99.991 for certain predetermined POHCs. The DREs for particular FOHCs
are determined by standardized sampling and analysis methods. A listing
of potential POHCg appears in Appendix VIII of the Code of Federal
Regulations (40 C.F.R., Part 261).
The U.S. Environmental Protection Agency (EPA) has published a
compendium of sampling and analytical roethod8 to be used in determining
the concentrations of POHCs in the discharge from waste incinerators.
Methods are presented for application to various segments of the
incineration process including waste feed, aqueous effluents (cooling
water or spent scrubber liquor), fly or bottom ashes, and stack gases.
Sampling and analytical methodology for the determination of POHCs in
stack gases emitted from hazardous waste incinerators have been
identified in waste incinerator operation permit applications, and is
commonly referred to as Semi-Volatile Organic Sampling Train (Semi-VOST)
methodology.
The major focus of the Semi-VOST method evaluation study discussed
in this paper is to determine precision and accuracy of the method under
actual field operating conditions. Prior to the field test, several
laboratory experiments were performed to evaluate the sampling train
configuration and the analytical protocols: 1) evaluation of the method
formulation; 2) construction of the Semi-VOST sampling hardware; 3)
selection of test compounds to challenge the sampling and analytical
protocols; and 4) the Semi-VOST laboratory evaluation. Results of the
laboratory studies are reported in Reference 3.
METHOD FORMULATION
In the application of the Semi-VOST methodology, gaseous and
particulate components are isokinetically withdrawn from an emission
source and collected in a multicomponent sampling train (Figure 1). Key
elements of the train include a high-efficiency particulate filter and a
packed bed of a porous polymeric adsorbent resin (XAD-Z5; . The filter
is U6ed to separate stack Aas particles from gaseous substances which
are then ad semi-volatile
advantage or high surlace area 13UU m /gj combined with an average pore
size of 90 A. Following sample collection, the train components are
extracted with solvent which is concentrated, and identified/quantified
using high resolution gas chromatography coupled with low resolution
mass spectrometry.
FIELD EVALUATION STUDY
A field test program was conducted to evaluate the Semi-VOST method
performance at an operational hazardous waste incineration facility.
The incinerator was designed to destroy hazardous industrial waste
(excluding polychlorinated biphenyls) by high temperature combustion.
The test program included collecting a matxixed sequence of samples to
evaluate method precision, bias, and XAD-Z^ module breakthrough.
compounds
a polystyrene-divijjylbenzene copolymer
has the
686
-------
The tup ling iyB tea «n designed to u*e four simultaneously
operating Semi-VOST train*• In order to obtain identical samples of the
stack gases at a point of average velocity for each of the trains, a
common fixed, heated probe system (quad probe) was used (Figure 2).
Previously obtained laboratory data .indicated that compounds which
vere collected predominantly on the XAD-Z^ resin nodules , exhibited the
highest recoveries over a range of test conditions simulating combustion
gas conditions. Thsjee of the teat compounds with good adsorption and
recovery from XAD-Z^ included toluene, chlorobenzene, and
1 ,1,2,2-tetracbloroethane. To determine method bias under field
conditions, single gas cylinder standards vere obtained containing 8 to
10 ppm levels of each of the three compounds in a nitrogen balance. The
cylinder gases were passed through a manifold and a series of mass flow
controllers to provide a continuous three-component gas stream metered
into two of the four simultaneously operating trains. The configuration
of the dynamic spiking apparatus is shown in Figure 3. The flow
controllers were adjusted to provide an equivalent of 10 times the
Minimum Detection Limit (MDL) of each compound as determined by GC/MS
through a glass "tee" inserted in front of the condenser coil over a
2-hour sample collection period.
Overall method bias was evaluated by determining the percent
recovery of spiked levels of test compounds. Method precision was
evaluated by determining the mean percent coefficient of variation (CV)
for measured differences between levels of POHCs collected by a series
of paired unspiked trains. Retention of semi-volatile organic
incinerator emission compounds by the adsorbent resin was evaluated
through a series of distributive volume experiments designed to explore
the potential for breakthrough of POHCs from the XAD-Z^ module. During
an experiment series, each of the four trains was operated at the same
sample flow rate. Two of the four trains were allowed to sample for
twice the time of the other two. If breakthrough did not occur, the
twofold increase in time at constant sampling rate should have resulted
in a similar increase in the amount of sample collected on a
compound-by—compound basis, assuming the source was constant in
emissions.
For each train, six individual components were recovered and
returned to the laborator.ii for analysis. These were the probe rinse,
particulate filter, XAD-2 , coil rinse, condensate and rinse, and
impinger contents and rinse. The mixture of eight surrogate compounds
listed in Table 1 was selected for sample fraction spiking. Surrogates
were added to 9ample fractions during preparation and analysis to
determine extraction efficiency.
RESULTS AND DISCUSSION
Surrogate Recovery
Table 1 lists the mean overall surrogate recoveries from all sample
fractions. Mean values range from 75 to 124 perj^nt with CVs ranging
from 13.6 to 46.3 percent. The C7 measured for C-labeled
pentachlorophenol (PCP) recoveries was large for all fractions and can
be associated with variances typically found in the chromatography of
this compound.
687
-------
Method Bias Determination
Table 2 presents a summary of the analytical results of the dynamic
•piking experiments for a measure of method bias. Bun numbers are
listed as a set of four trains; i.e., runs 1A, IB, 1C, and ID are trains
A, B, C, and D from run number 1. A and B were trains spiked vith the
test compounds, and C and D were unspiked trains. For toluene, spiked
recoveries varied between 55 and 110 percent. The mean recovery was
101 percent after adjusting the value for the recovery of the d^-toluene
surrogate. Thus, the calculated bias was 4-1 percent.
Toluene was measured in the probe and coil rinses, as well as the
condensate and condensate rinse. The concentrations were found to be in
the same range as the corresponding values reported for the train blank
sample fractions. In addition, two samples of the same solvent lot used
for field sample analysis were analyzed for toluene by GC/HS. The
reaults, when adjusted for the approximate volumes of solvent used for
rinsing the coil and condensate reservoirs in the field, were 2 and 3
ng/uL toluene. The toluene concentrations reported in all train blank
and sample run fractions, excluding XAD-T^ modules, are therefore due to
toluene contamination of the solvent used for sample recovery. For this
reason, the concentration of toluene in the above fractions was not
included in the bias calculation.
For chlorobenzene, the dynamic spike concentration was low relative
to the unexpected high levels measured in the stack gas. Therefore, the
resulting small concentration differences between the spiked and
unspiked samples prevent a realistic estimate of recovery for
calculating bias.
The recoveries of 1 ,1,2 ,2-tetrachloroethane ranged from 48 to 96
percent. The test compound was detected in one of four condensate
rinses analyzed, an in<^:ation of compound breakthrough or possibly
channeling in the XAD—2 resin module for this particular train. The
average of the paired, spiked recoveries for run 1 is 84 percent. The
average recovery for 1,1,2,2-tetrachloroethane of 52 percent in run 2
suggests a problem with the dynamic &piking system. During the
development and evaluation of the system in the laboratory, several
design modifications including the addition of heat tracing were
incorporated specifically to reduce the time required for all three
compounds to reach an equilibrium. 1 ,1 ,2 ,2-Tetrachloroethane was always
the last compound to reach an equilibrium concentration. However the
ambient temperatures during field sample collection were extremely cold
and may have been responsible for the low recoveries of
1 ,1 ,2,2-tetrachloroethane from run 2. Excluding run 2 data, the bias
was calculated as -16 percent for 1 ,1 ,2 ,2-tetrachloroethane.
Overall method precision was determined using a pool of seven
paired unspiked sample analyses for chlorobenzene. Chlorobenzene was
used because it was the only compound always present in the stack gas at
sufficient concentration levels to allow method precision determinations.
The method precision for chlorobenzene can be separated into three
components — sampling, sample preparation, and GC/MS analysis — in
terms of percent of total variance and percent CV for each component.
For the preparations and analyses used, the number of preparations per
6ample and analyses per preparation is one. The preparation variance
was 6.4 percent of the total variance, while the GC/MS analytical
688
-------
variance vas 93.6 percent of Che variance. The percent of total
variance indicate* the aaount of scatter in the data; the percent CV
indicate* the precision of the data. The percent of total variance for
sampling, sample preparation, and GC/HS analysis for the field
evaluation vere 78.5, 1.4, and 20.1 respectively. Most of the variance
during the field test was due to sanpling. The corresponding percent
CVs vere 17.6, 2.3, and 8.9, resulting in method precision for
chlorobensene of 19.9 percent, uncorrected for surrogate recovery, and
calculated from a data set representing seven degrees of freedom.
Distributive Volume Experiments
Chlorobenzene vas detected in all unspiked stack emission samples
collected for distributive volume analyses. Sample volumes ranging from
one to three cubic meters were used to assess the breakthrough potential
for ajj^ek gas components. The chlorobenzene levels measured from the
XAD-Z^ fractions doubled with corresponding increases in sample volume,
demonstrating good adsorption, retention, and recovery. Analysis of
condensate and impinger rinses from the chlorobenzene samples also
indicate that breakthrough did not occur.
Data presented in Table 3 are plotted in Figure 4 to test
linearity between the chlorobenzene concentration measured and the
volume of flue gas sampled. Other POHCs were not consistently found in
a sufficient number of unspiked samples to warrant additional
distributive volume analysis. A least squares analysis vas performed
and the variables were found to be correlated (r=0.95) with a "zero"
sample volume intercept of 0.1 ug chlorobenzene. The analytical data
confirms that no breakthrough occurred because distributive volume
theory predicts that the amount of compound retained on the adsorbent is
a direct linear function of the sample volume collected when the levels
of POHCs are constant. Non-linearity occurs at the compound
breakthrough volume.
ADDITIONAL LABORATORY ANALYSIS
Following the field study, additional laboratory experiments vere
performed to investigate the analytical methodology used for Semi-VOST
and possible interactions of POHCs with the XAD-7^ adsorbent resin.
Four compounds were chosen for experimentation: aniline, pyridine,
phenol, and resorcinol. Pyridine, phenol, and resorcinol were chosen
because of either p^or or variable recoveries measured during previous
laboratory studies. Aniline, a basic organic compound, wa^g^hosen for
its potential to form a salt in an acidic medium. The XAD-2 resin was
spiked with an internal standard and transferred to an all-glass Soxhlet
extraction thimble. The nodule was rinsed with methylene chloride, the
solution was added to the Soxhlet, and extraction was conducted for
16 hours. The methylene chloride solution vas passed through anhydrous
sodium sulfate to remove water, concentrated in a Kuderna-Danish (KD)
evaporator/concentrator to reduce volume, and a quantitation standard
added prior to analysis. o-Xylene was added to the samples as the
Bystem internal standard. The IAD-Z^ sorbent during Semi-VOST sampling
becomes vet and acidic due to the presence of water vapor and
hydrochloric, Bulfuric , and/cws nitric acid in the stack. During the
laboratory studies, the XAD-2 resin was acidified to pH 2 with aqueous
689
-------
hydrochloric acid to sinulate these sampling conditions. Test compounds
were added to pH 2 water and spiked into the resin. Three separate
layers from the resin extract were analyzed: methylene chloride, vater
from a separatory funnel phase separation of methylene chloride, and
methaaol/vater obtained by methanol Soxhlet extraction of the acidic
XAD-Z^ resin. The results are given in Table 4.
The following observations can be made: 1) basic organic compounds
(aniline and pyridine) react with an acidic environment to form salts
which are soluble in water and insoluble in the methylene chloride
extraction medium, thuB resulting in poor recoveries; 2) compounds that
are vater soluble (such as resorcinol) vill associate with any vater
present in the system. The present analytical method involves solvent
extraction of vet resin. The solvent is then dried by sodium sulfate
for subsequent concentration and GC/M5 analysis. Compounds associated
with the vater present in the solvent are removed by thiB drying process
and not recovered in the analysis. Based on the above, a base
extraction of the vater phase, and a more polar extraction solvent must
be used in the analytical methodology to^xecover salts and vater soluble
compounds from the water phase and XAD-2 .
CONCLUSIONS AND RECOMMENDATIONS
Based on results of the method evaluation studies presented in this
paper, the following recommendations are made:
• Method bias and precision have been Bhovn to be compound-
specific according to properties 6uch as water Bolubility,
chemical reactivity, and adsorption strength (retention
volume) on XAD-2. Therefore, a screening method Bhould be
developed to determine vhich Appendix VIII compounds are
suitable for sample collection and analysis by the Semi-VOST
method .
• Semi-VOST analytical methodology requires modification to
include procedural steps that account for salt formation from
the basic organic compounds with acids collected by the train
during sampling and compounds of high water solubility which
are difficult to extract with methylene chloride.
• Additional laboratory dynamic spiking experiments should be
performed using a dynamic spiking system redesigned to
accommodate single cylinder use. Single gas cylinder use
excludes mixing and manifolding the spiked compounds, which
will eliminate a large number of flow variables. Deuterated
compounds blended in one certified gas cylinder should be used
in these experiments. Unlabeled compounds present in the
stack emissions can be differentiated from the spiked
compounds by GC/MS analysis.
• Dynamic spiking field experiments should be repeated at a
hazardous waste incineration site using the redesigned spiking
system. The experimental test plan would include
determinations of precision, bias, and distributive volume
experiments.
690
-------
SUMMARY
Three test compounds (toluene, chlorobenzene, and 1,1,2,2-tetra-
chloroethane) were chosen for dynamic spiking experiments to determine
bias. The bias values for toluene and 1,1,2,2-tetrachloroethane are +1
and -16 percent, respectively. Bias could not be determined for
chlorobenzene since the dynamic spike concentration was low relative to
the unexpectedly high levels measured in the stack gas. Method
precision for chlorobenzene vas calculated from unspiked sample train
results, and vas separated into three components: sampling, sample
preparation, and GC/MS analysis. The results vere 17.6, 2.3, and 8-9
percent, respectively. The overall method precision vas 19.9 percent
for chlorobenzene uncorrected for deuterated spike recovery.
Distributive volume experiments vere performed using chlorobenzene
concentrations of the stack gases to determine sample train
breakthrough. No breakthrough vas observed at a flov rate of 0.5 cfm
for a sample collection period of 4 hours.
Laboratory experiments performed using aniline, pyridine, phenol,
and resorcinol shoved that basic organic compounds (aniline and
pyridine) react with an acidic environment to form salts. The salts of
these compounds are insoluble in the extraction solvent and soluble in
vater that is present in the system. Resorcinol vas found to be
extremely soluble in vater and requires a more polar extraction solvent.
Based on the laboratory data, vithout modification of the Semi-VOST
method formulation, compound loss due to vater solubility can range from
34 to 75 percent for pyridine and resorcinol.
DISCLAIMER
Although Che research described in this article has been funded
vholly or in part by the United States Environmental Protection Agency
through EPA Contract No. 68-02-4119 Co Radian Corporation, it has not
been subjected to Agency reviev and, therefore, does not necessarily
reflect the vievs of the Agency and no official endorsement should be
inferred .
REFERENCES
1. J. Bursey, M. Hartman, J. Homolya, R. McAllister, J. McGaughey, and
D. Wagoner, Contract No. 68-02-4119, "Laboratory and Field
Evaluation of the Semi-VOST Method," Volumes I, PB 86 123551/AS and
Volume II, PB 86 123569/AS) , September 5, 1985.
2. U.S. Environmental Protection Agency. Test methods for evaluating
9olid waste: physical/chemical methods. EPA Report No. SW-846 ,
U.S. Environmental Protection Agency, Washington, D.C.: 1982.
3. J. Homolya, J. McGaughey, D. Wagoner, M. Rartman, J. Margeson,
J. Knoll, and M. Midgett, "Validation of the Semi-Volatile Organic
Sampling Train Method for Measuring Emissions from Hazardous Waste
Incinerators," for presentation at the 78th Annual Meeting of the
Air Pollution Control Association, June 16-21, 1985. Paper
No. 65.1 .
691
-------
Table I. OVERALL SURROGATE RECOVERIES FROM ALL FRACTIONS
£
Surrogate compound Mean recovery, Z CV, Z
d^-1 ,4-Dioxane 86.6 17.1
d,.-Pyr id ine 82.3 23.7
d -Toluene 75.0 26.A
o
d^-Chlorobenzene 85.5 22.2
d5-Phenol 96.1 13.6
d^-Nitrobenzene 117 16.9
dg-Kaphthalene 106 15.8
13
C^-Pentachlorophenol 124 46.3
'Mean of 39 values,
692
-------
Table II. ANALYSES OF DYNAMIC SPIKING RONS
CO
M
Compound
concentration
» ng/uL
Impinger
Probe
Coi 1
Condensate
and
_ £
Tea t
Recovery
Run
r inse
XAD-2
rinse
and rinse
r inBe
Total
Compound
(Z)
Toluene
1A
9.2
10.1
3.6
ND°
ND
10.1
18.5
55
IB
7 .0
17.A
3.2
ND
ND
17 .4
18.5
94
1C
4.5
2.4
3.7
ID
5.1
ND
4.3
L
2 A
2 .8
16.0
2.8
1 .9 (KDL)
ND
16.0
18.5
87
2 B
ND
20.4
3 .2
3 .1
ND
20.4
18.5
110
2C
ND
2D
ND
Train
3 .1
ND
3 .0
4.0
ND
b lank.
1A
ND
23.8
ND
0 .7
ND
24.5
3.7
d
IB
ND
28.0
ND
ND
ND
2 8.0
3 .7
d
1C
ND
26.1
ND
in
ND
22 .6
ND
2A
ND
34.7
ND
ND
ND
34.7
3 .7
d
2B
ND
60.1
ND
ND
60 .1
3.7
d
2C
20.3
2D
20.8
Train
ND
ND
ND
ND
ND
b lank
Adjusted
recovery
(X)
K
110
I02b
129^
(continued)
-------
Table II. ANALYSES OF DYNAMIC SPIKING RUNS (continued)
Compound concentration, ng/uL
Imp i nger
Adjusted
Run
Probe
rinse
XAD-2®
Coil
rinse
Condensate
and rinse
and
r inse
Total"f
Tes t
Compound
Recovery
(Z)
recovery
(J)
1 .1 .2.2
1A
ND
1 .8
ND
ND
ND
1.8
2.5
72
e
IB
ND
2 .0
ND
0 .4
ND
2 .4
2 .5
96
e
IC
ND
ND
ND
ID
ND
ND
ND
2A
NT
1 .4
ND
ND
1.4
2 .5
56
e
2B
ND
1 .2
ND
1 .2
2 .5
48
e
2C
ND
2D
ND
Train
ND
ND
ND
ND
ND
b lank
A [v
Including only the XAD-2 trap for toluene.
^Toluene dynamic spike recovery adjusted for mean recovery of d0-toluene surrogate.
o
c
ND = compound not detected at its MDL.
^Not calculated due to high levels of ch lorobenzene in stack emiBsions.
6
No adjustment made for surrogate recovery.
^Particulate Kilters were analyzed and no target compounds were detected.
-------
Run
3A
3B
3C
3D
4A
4B
4C
4Da
5A
5B
5C
5D
Train
b lank
Value
Table III. ANALYSES OF DISTRIBUTIVE VOLUME RUNS
Sample
volume Chlorobenzene
(m ) ug
I .48
118
2 .91
270
1 .51
124
2 .69
255
0-99
100
1 .73
188
1 .01
106
1 .70
97
0 .91
132
1 .71
165
0.91
75
1 .65
154
__
ND
eliminated due to mechanical problems during test.
695
-------
Table IV. XAD-^f® RESIN EXPERIMENTS
Z RECOVERY3
Compound
Methylene
Chloride
Water
Methanol/
Water
Totalb
Z CVb
o-xylene
2 CVb
Ani1ine
86.6
0.00
2.89
88-5
A .40
88.2
2.58
Pyridine
54.3
28.0C
0 .00
82.3
2.01
88.2
1.33
Phenol
84.3
0 .00
0.00
84.3
6 .91
91 .2
1.17
Resorc inol
22 .9
69.1°
0 .00
92.0
6 .58
87 .9
4.79
aThe determination of % recovery is based on the quantitation standard
ethylben2ene
bThe total percentage recovery and 1 CV (coefficient of variation)
calculations are based on three individual experiments on each compound.
°Based on the normal Semi-VOST methodology, pyridine and rjisorcinol present
in the methylene chloride extract of the wet acidic XAD-2~ resin will
associate with the residual water and be lost when passed through
anhydrous sodium sulfate.
696
-------
Fill** H«M«»
CMcfc Vsfva
TMtNMMOapM
ycton*
T TriM MUt
Slack Wmnyr
NtlKd Z«M
lem ¦•(!»
f WllN KMCkoM
Raclrcniatisii Pmm*
Otitic*
Mm Vaitt
(J
Di« Om Ali-Tlflht
kitlM Pump
Vkm Lb*
Figure 1. Semi-VOST train diagram.
-------
TRAM D
TRAM C
G=r
C=r
ff°
w
TRAMS
TRAM A
Figure 2. Quad probe.
698
-------
r-
PC-t
0-lOOce/mln,
T« Trala AO
•a «•/¦<¦.
PC-4
O-
FC-a
O-IOae/nln
Nil TriM
TiDm LImi
Ta Trala B
'Mia
Chi
FC-3
O-ioeo/Mla
¦•a I
Figure 3. Dynamic spiking apparatus.
-------
~~1—
40
—j—
80
—I—
120
—I—
160
—I
20O
—I—
240
200
CHLOROBENZENE (ug)
Figure 4. Distributive sample volume collected
versus chlorobenzene concentration measured.
700
-------
DETERMINATION OF ORGANIC AND INORGANIC CHLORINE
IN USED AND WASTE OILS
Alvia Gaskill, Jr.
Eva D. Estes, David L. Hardison
Research Triangle Institute,
Research Triangle Park, North Carolina and
Paul H. Friedman, Office of Solid Waste,
U. S. Environmental Protection Agency,
Washington, D.C.
The U. S. Environmental Protection Agency (EPA) has issued a final
rule prohibiting the sale for burning in nonindustrial boilers of used
oils contaminated above specified levels with certain metals and total
chlorine. When burned as fuel in a small boiler, the contaminants may
be emitted to the ambient air at hazardous levels. This regulation
establishes a rebuttable presumption that used oil containing more than
1,000 ppm total chlorine has been mixed with haloger.ated solvents and is
a hazardous waste. Rebutting the presumption requires the seller of the
oil to prove that this chlorine is not due to halogenated solvents or
other hazardous halogenated organics. If the rebuttal is successful,
the oil can be sold as fuel up to a level of 4,000 ppm total chlorine.
Methods for determination of total, inorganic, and organic chlorine
were investigated and developed to provide the regulated community with
appropriate test methods to meet the chlorine testing requirements of
this regulation.
Total chlorine was determined by Parr oxygen bomb combustion
followed by ion chromatography (IC). An aqueous extraction method,
developed for determination of inorganic chlorine, involves the dissolu-
tion of an oil sample in toluene (to reduce the effects of surfactants
on the extraction) followed by three sequential aqueous extractions and
analysis of the combined extracts by IC. Organic chlorine is determined
from the difference between total and inorganic chlorine.
These methods were evaluated on both unspiked and spiked virgin and
waste oils. Recoveries of total chlorine (when spiked as both organic
and Inorganic species) of around 90% were achieved at levels between
1,000 and 10,000 lig/g In the presence of water levels ranging fror. 0 to
50 percent. Recoveries of inorganic chlorine around 90Z were achieved
at levels between 1,000 and 5,000 Ug/g inorganic chlorine.
701
-------
DETERMINATION OF ORGANIC AND INORGANIC CHLORINE IN USED AND WASTE OILS
1. Introduction
More than 1 billion gallons of used lubricating oil are produced
in the United States annually. A significant fraction is sold for
burning in small nonindustrial residential, commercial, or institution-
al boilers, typically after blending with virgin nos. 4 or 6 fuel oils.
These used oils frequently arrive at fuel reprocessing or blending
facilitiej contaminated with chlorinated solvents, lead, cadmium, and
arsenic. These contaminants may be present as a result of the oil's
use or may have been added through mixing with hazardous waste.
Reprocessing, with the exception of rerefining, typically fails to
remove these contaminants.
When burned as fuel in a small boiler, the contaminants or their
combustion byproducts may be emitted to the ambient air in amounts high
enough to present potential health hazards to exposed individuals.
This concern has lead EPA to propose and later finalize a regulation
prohibiting the sale and burning of used oil contaminated at levels in
excess of those given in Table 1. When a person first claims used oil
fuel meets these specification levels, he must obtain an analysis or
other information to support the claim.
The final rule establishes a rebuttable presumption that used oil
containing >1,000 ppm total chlorine is mixed with halogenated hazard-
ous waste and, therefore, is a hazardous waste. (Because total halogen
content cannot easily be determined in the field or laboratory, EFA
has agreed^to interpret "total halogen" in the final rule as total
chlorine. ) The presumption may be rebutted by snowing that the used
oil has rot been mixed with hazardous wastes (.e.g., by showing it does
not contain significant levels of halogenated hazardous constituents).
Used oil presumed to be mixed with hazardous waste is subject to
regulation as hazardous waste fuel when burned for energy recovery.
In addition, the rule establishes a specification for used oil
fuel (i.e., used oil not mixed with hazardous waste) that Is essentially
exempt from all regulation and may be burned In nonindustrial boilers,
provided that allowable levels for designated toxic constituents, flash
point, and total chlorine (4,000 ppm) are not exceeded. Used oil
exceeding any of the specification levels is termed "off specification
used oil" and Is subject to regulatory control. This second chlorine
threshold is set to ensure that harmful emissions of hydrochloric acid
are net emitted from the boiler or allowed to corrode it and reduce its
efficiency. The decision process to determine whether the oil can be
burned is shown in Figure 1.
The rebuttable presumption has changed from the proposed to the
final regulation. In the proposed regulation, the presumption was
based on proving that most of the chlorine was inorganic and thus not
hazardous. The final regulation requires the seller of the oil fuel to
prove that none of the solvents listed under EPA Hazardous Waste
Numbers F001 and F002 is present at > 100 ppm or that no other hazard-
ous chlorinated organics are present. These include the degreasing and
spent halogenated solvents methylene chloride, tetrachloroethylene,
1,1,1-trichloroethane, trichloroethylene, 1,1,2,2-tetrachloroethane,
dichlorodifluoromethane, and l,l,2-trichloro-l,2,2-trifluoroe thane.
702
-------
Between proposal and final rulemaking, EPA decided that levels of
inorganic chlorine seldom would cause an oil to exceed the 1,000-ppm
level. In addition, EPA based their presumption on the total chlorine
level because a practical method for determining the organic chlorine
content was unavailable.
Between the time of the proposal and the final rulemaking, the
EPA Office of Solid Waste (OSW), and its contractor, Research Triangle
Institute (RTI), Investigated methods for determining total, inorganic,
and organic chlorine in used and y;aste oils. The results are summarized
here and are detailed elsewhere. Another study evaluating methods for
determining total chlorine in used and waste oils is in progress.
Results will be presented at the EPA/OSW Symposium on Solid Waste Testing
and Quality Assurance In July 1986.
2. Development and Validation of Sample Preparation and Analysis
Procedures for Total, Inorganic, and Organic Chlorine
2.1 Results of Literature Review
A literature review was conducted to identify the sources and
composition of chlorine and other halogens in used and waste oil and to
evaluate the previous development and testing of methods for determining
chlorine in waste oils. This review indicated that automobile crankcase,
industrial hydraulic, and metalworking oils accoynt^for nearly two-thirds
of the waste oil produced in the United States. Major chlorine
sources in waste oils are chlorinated solvents deliberately added to the
oil, with smaller quantities of other chlorinated organics entering the
oil through normal use. Waste oil sampling and aliquoting procedures
greatly Influence testing program results. Interpretation of results
from such testing should consider the representativeness of the
sampling, the laboratory aliquoting, and the potential contribution o^ g
bottom sediment and water in determining the oil's chlorine content. '
Methods for determining total chlorine and other halogens have
included oxygen bomb combustion/tjtrations, sodium alcoholate
extraction/titration, x-ray fluorescence, neutron activation analysis,
microcoulometric titration by an analyzer, oxygen bomb combust Ion/'ion
chromatography (IC) , and field kits using g ^emical colorimetric
reaction or a flame photometric response.
Methods for determining inorganic chlorine include dissolution of
the oil in methyl isobutyl ketone (MIBK), followed by aqueous extrac-
tion folljyed by ion chromatographic or automated chloride analyzer
analysis and speciation by a total chlorine analyzer.
Methods for determining organic chlorine as specific organics by
gas chrorcatography/tuass spectrometry (GC/MS) generally do not.ac^ount
for all of the chlorine expected from a total determination. '
2.2 Selection and Development of Test Methods
2.2.1 Total Chlorine Determination. Based on the literature review
and our familiarity with these techniques, Parr oxygen bomb combustion
followed by IC j|er^selected for determining the total chlorine content
of waste oils. '
703
-------
The sample (0.5 g) is oxidized by combustion in a bomb containing
oxygen under pressure. The liberated halogen compounds are absorbed in
a sodium carbonate/sodium bicarbonate solution. Approximately 30-40
min. are required to prepare an oil sample by this method. Samples with
very high water content (>50%) may not combust efficiently and may
require the addition of a mineral oil to facilitate combustion.
The resulting aqueous sample is injected directly into the ion
chromatograph and is carried through the separator column under high
pressure by a continuous eluent flow. The separated ions are then pass-
ed through a post-separator-column suppressor device that converts the
analyte ions into a highly conducting form while converting the eluent
ions into a less conducting form. Detection is typically by conduc-
tivity. Sample analysis requires approximately 15 min.
The precision and accuracy of IC for determining chloride, fluoride,
and bromide in aqueous solution are around 5% RSD and 90% recovery for
levels >0.1 mg/1 in solution. Detection limits are better than 20 ug/1
for chloride and fluoride.
IC is an attractive analytical finish because several halide
ions—chloride, bromide, and fluoride-~mav be determined simultaneously,
although bromide in combusted waste oils is best detected with electro-
chemical detection. If a total halogen determination is desired, these
other halogens must also be quantified. In this study, data are
reported for both chlorine and fluorine.
2.2.2 Inorganic Chlorine Determination. An aqueous extraction method
was developed for determining inorganic chlorine. The method involves
the dissolution of an oil sample in toluene (to reduce the effect of
surfactants on the extraction) followed by three sequential, aqueous
extractions and analysis of the combined extracts by IC. Approximately
2 to 3 hr. are required to obtain the combined extracts. Attempts to
develop a method to measure organic chlorine directly were unsuccessful
because of losses of the volatile chlorinated constituents during the
extractions. Instead, organic chlorine is determined by the difference
between total sr.d inorganic chlorine measured on separate alJquots of
the same sample.
To ensure that the "oil phase" could be separated from the aqueous
phase, the oil sample was dissolved in an organic solvent prior
extraction, as is the case with the qualitative ASTM procedure, which
recoranends MIBK. In a previous study, MIBK was found to interfere
with halide determination by IC. Discussions with Dionex, a manufacturer
of IC systems, disclosed that toluene may be used successfully instead
of MIBK if the sample sits for a sufficient time to allow the toluene
that partitions into the aqueous phase to separate from it and
evaporate.
Initially, duplicate 2-ml aliquots of a spiked oil sample were
placed in 40-ml glass centrifuge tubes and 20 ml of toluene added to
each to dissolve the oil. Then 10 mL of water were added to each tube
and the samples vortexed and centrifuged. A white, insoluble material,
probably a result of surfactants in the oil, formed at the toluene/
aqueous phase interface of both samples. Ulien the toluene and aqueous
phases were analyzed for halide content, total recoveries for both
chloride and fluoride were 1*17,, with a greater quantity of each
704
-------
remaining In the toluene phase. It was concluded that most of the
organic chlorine was probably lost in the extraction procedure and that
the Inorganic chlorine was incompletely extracted or trapped in the
white emulsion at the interface of the two phases.
To test the efficiency of this extraction procedure for inorganic
halides, a virgin motor oil was spiked with halide solution. A 2-ml
aliquot of the spiked oil was extracted three successive times with
10-ml portions of deionized water. Each extraction removed approximately
25% of the available chloride and fluoride. The three extractions
removed approximately 60% of the fluoride and chloride.
An alternate extraction procedure was designed that involves a
1:100 dilution of oil with toluene to reduce the level and impact of
surfactants associated with the oil. The procedure's extraction
efficiency was evaluated by analyzing a variety of spiked virgin and
waste oils. One ml of the oil was dissolved in 100 ml of toluene, the
sample was thoroughly mixed, and a 20-ml aliquot of this mixture was
removed and extracted sequentially three times with deionized water.
After each extraction, the aqueous layer was transferred by disposable
pipet to a beaker and the toluene allowed to evaporate. Chloride and
fluoride in the three separate extracts were determined by IC. The
total mass of chloride and fluoride removed per extraction was calculated
so that carry-over from extract to extract was not included in the next
extraction. This procedure was adopted for determining inorganic
chlorine in waste oils.
2.3 Sample Preparation Procedures
2.3.1 Homogenization Procedure. Immediately before removing an aliquot
for Parr bomb combustion, each sample was homogenized by vigorously
shaking the closed sample container. None of the analyzed samples
required the addition of a surfactant to emulsify an insoluble fraction.
Because loss of volatile organic components could occur during the
homogenization step, the collected samples should have only enough head-
space to ensure complete mixing. Replicate and spiked samples were used
to evaluate the homogenization procedure.
2.3.2 Preparation of Inorganic Halide-Spiked Oil. Virgin and waste
oils, characterized for total halogen content, were spiked with known
quantities of an aqueous mixture containing fluoride and chloride such
that the amount of water added was approximately 25% of the total volume.
The resulting fluoride and chloride levels were between 1,000 and 6,000
|jg/g. Each oil and water mixture was shaken in a nearly headspace-free
Nalgene® bottle until a homogeneous emulsion formed.
2.3.3 Preparation of Organic Halogen-Spiked Oil. Virgin and waste
oils were spiked with water and with either trichlorotrifluoroethane
(TFE) or an organic mixture consisting of equal volumes of TFE, 1,1,1-
trichloroethane, trichloroethylene, and tetrachloroethylene. The
resulting mixtures contained 5 to 50% water and 5,000 to 20,000 Ug/g
fluorine and chlorine. Each oil mixture was homogenized as described in
2.3.2.
2.3.4 Preparation of Mixed Organic/Inorganic Halogen Spiked Oil.
Virgin and waste oils were first spiked with an aqueous inorganic
halogen mixture as described in 2.3.2. Then an organic halogen mixture
705
-------
(as described in 2.3.3) was added to the emulsion that formed, and the
sample shaken again. The resulting oil mixtures contained approximately
25% water and 2,000 to 20,000 Vg/g fluorine and chlorine.
3. Results and Discussion
3.1 Total Chlorine Determination
Virgin and waste oils, both unspiked and spiked, were analyzed in
duplicate or triplicate for chlorine and fluorine content to evaluate
the homogenization and Parr bomb combustion procedures. Results are
summarized in Table II. The precision of the measurements, expressed
as the relative percent difference (RPD) for duplicate analyses or
relative standard deviation (RSD) for triplicate analyses, is an
indicator of the oil sample's homogeneity. The chlorine and fluorine
RSDs and RPDs for all samples analyzed ranged from 1 to 16%, indicating
that the homogenization procedure is adequate for samples of this type.
Chlorine and fluorine recoveries obtained for the spiked virgin
and waste-oil samples were used to evaluate the homogenization and Parr
bomb combustion procedures. Recoveries from the oil samples ranged from
85 to 101% for chlorine and 73 to 90% for fluorine. In general,
recoveries of total chlorine (when spiked as both organic and inorganic
species) of around 90% were achieved at levels between 1,000 and 10,000
Mg/g in the presence of water levels ranging from 0 to 50%.
The method detection limit has not been evaluated, but chlorine and
fluorine levels of 50 Ug/g in the original oil can be determined. If
0.5 g of an oil containing 50 Ug/g chlorine is combusted and the
combustate diluted to 100 mi, the IC will measure a solution of around
250 yg/1 chloride.
3.2 Inorganic Chlorine Determination
Duplicate aliquots of inorganic halogen-spik.ee virgin motor oil
were extracted according to the procedure described in 2.2.2, yielding
chloride and fluoride recoveries of 103 and 70%, respectively. However,
the same oil spiked with both inorganic and organic halogen did not mix-
well, and duplicate analyses of this sample yielded average chloride and
fluoride recoveries of 48 and 46", respectively. The spiked oil sample
was allowed to stand overnight, was remixed, and then reanalyzed,
starting with the toluene dissolution step. Recoveries for chloride and
fluoride were 92 and 96%, respectively.
To test the procedure further, three types of waste oil samples
(hydraulic, crankcase, and grinding/cutting) were analyzed in triplicate
for extractable chloride and fluoride. With the exception of the
chloride value for the grinding and cutting oil, the RSDs were less than
25". The hydraulic and crankcase oils were then spiked with both
inorganic and organic halogen and analyzed in duplicate. Chloride
and fluoride recoveries from the spiked hydraulic oil were 42 and 40%,
respectively; the chloride and fluoride recoveries from the spiked
crankcase oil were 65 and 55%, respectively.
There is a problem in obtaining a representative aliquot from the
oil dissolved in toluene. Water in the oil tends to form small beads
and settle to the botton of the flask. No improvement in recoveries
706
-------
was observed, even when the solution was stirred while an aliquot was
removed. To eliminate the aliquoting step, an alternate procedure was
developed. A 0.2-g aliquot of a spiked hydraulic waste-oil sample was
weighed by difference directly into a 40-ml centrifuge tube, 20 ml of
toluene were added, and the tube was vortexed to dissolve the sample.
This results in a 1;100 dilution of the oil sample as in the previous
method. The sample was extracted sequentially three times with 10-mL
portions of deionized water. The aqueous extracts were analyzed
individually for chloride and fluoride by IC. Using this procedure,
97% of the extracted fluoride and 98% of the extracted chloride are
removed in the first extraction. Similar results were achieved with
waste crankcase and virgin motor oils. Therefore, it is recommended
that the extracts be combined and the total extract volume measured so
that the sample can be analyzed by a single injection into the IC.
To ensure that no organic halogen is extracted into the aqueous
phase, four aliquots of a virgin motor oil sample spiked with organic
halogen were extracted according to the proposed procedure. The spiking
levels were 10,474-|jg/g chlorine and 1,088-yg/g fluorine. The aqueous
phase from the first extraction of each aliquot was analyzed for total
organic halogen on a Xertex-Dohrmann Total Organic Halogen Analyzer.
Analyses of the extracts indicate that less than 0.1" of the volatile
halogen species partitioned into the aqueous phase.
An attempt a]so was made to analyze the extracted toluene-oil
phase for remaining halogen species. This effort proved unsuccessful
because the toluene was found to contain either chlorinated organics or
other substances that interfered with the IC determination.
The entire procedure requires approximately 2 to 3 hr. The steps
of weighing, adding toluene and water, and mixing require 15 min.
Centrifuging and removing the aqueous phase requires 15 to 30 min.
Evaporation of toluene requires 1 hr. Combining extracts and measuring
the final extract volume requires 10 min.
The precision 8r.d accuracy of the extraction/IC method for deter-
minations of inorganic halogens were evaluated by testing spiked virgin
and waste oils. The results (Table III) indicate that recoveries greater
than 90Z and precisions around 10% RSD are achievable at chlorine and
fluorine levels between 1,000 and 5,000 Ug/g.
The method detection limit has not been evaluated, but inorganic
chlorine and fluorine levels of around 50 Ug/g in the original oil can
be determined. If 0.2 g of oil containing 50-yg/g inorganic chlorine
are extracted and the resulting combined extract volume is 30 ml, the
extract concentration should be 33 ug/L chloride.
4. Conclusion
An analytical approach hap been developed and tested on virgin and
waste oils to allow determination of total and inorganic chlorine and
other halogens by direct measurement and organic chlorine and other
halogens by difference. This approach is shown in Figure 2.
It is not clear whether inorganic chlorine will present a problem
either in classifying a used oil as a hazardous waste fuel or as an
off-specification fuel. The methods presented here offer a workable
707
-------
approach to addressing the issue ana should be considered. The findings
presented here do not necessarily reflect EPA policy.
5. Acknowledgments
The authors acknowledge A. Turner of RTI for carrying out the IC
analyses. N. Rothman of ENSECO, R. Tarrer of Auburn University, and M.
Branscome of RTI are thanked for providing the waste oil samples. We
acknowledge E. Williams for preparing the manuscript.
6. References
1. Franklin Associates Ltd. 198&. "Composition and management of used
oil generated in the United States." Prepared for the U.S. EPA/OSW,
under Contracts 68-02-3173 and 68-01-6467.
2. U. S. Environmental Protection Agency, Federal Register, 50(8):
1684-1724 (January 11, 1985).
3. U. S. Environmental Protection Agency, Federal Register, 50
49164-49211 (November 29, 1985).
4. Gsskill, A. RTI to D. Friecman, EPA/OSW, personal communication,
(January 29, 1986).
5. Gaskill, A, Jr., D. L. Hardison, and E. D. Estes. 1985.
"Development and validation procedures for determination of
halogen species in waste oils." EPA Contract No. 68-01-7075.
(i. Beachey, J. E. and W. L. Bider, 1986. "Trends in used oil
composition and management." In: Proceedings of the National
Conference on Hazardous Wastes and Hazardous Materials, Atlanta,
Georgia, March 4-6, pp. 419-423.
7. ERCO/A Division of ENSECO. 198&. "Hazardous waste identification
and listing support, waste oil analysis." EPA/OSW Contract No.
68-01-6467 Assignment No. HWLS-13.
8. Ehmann, J. L. J. Menzel, M. E. Lukey, and R. Predale. 1983.
"Waste oil characterization study." Presented at the MIdaclancic
States Section of the Air Pollution Control Association meeting in
Wilmington, Delaware, April 19, 1983.
9. Hall, R. R., R. J. Ellersick, M. Hovt, M. F. Kozik, and D. F.
McGrath. 1984. "Comparative analysis of contaminated heating
oils." EPA 600/7-85-56.
10. Pei, P., R. Fleming, and S. M. Hsu. 1984. "Test methods for total
chlorine in lubricating oils." KBS Special Publication 674. In:
Proceedings of the Conference on Measurements and Standards for
Recycled Oil-IV. Gaithersburg, Maryland.
11. Tarrer, A. K. and A. Gaskijl, Jr. 1985. "Development of a field
test for monitoring organic halides in waste fuels", (EPA/OSW
Contract No. 68-01-7075, Work Assignment No. 22.
708
-------
12. ASTM. 1981. Annual Book of Standards. Volume 05.01. D808-81,
Standard Test Method for Chlorine in New and Used Petroleum
Products.
13. ASTM. 1981. Annual Book of Standards Volume 05.01 D878-65, Test
Method for Inorganic Chlorides and Sulfates in Insulating Oils.
TABLE I. USED OIL FUEL SPECIFICATIONS FOR OIL THAT MAY BE EURNED IN
NONINDUSTRIAL BOILERS
Allowable level for burning
Constituent/Property without regulation
Arsenic <5 ppm
Cadmium <2 ppm
Chromium <10 ppm
Lead <100 ppm
Total Chlorine <1,000 ppmf
<4,000 ppm
Flash Point >100°F
^Level presuming mixing with hazardous waste.
Level above which burning is not permitted if presumption can be
rebutted.
709
-------
TABLE II. ANALYSES OF OIL SAVPLES FOR TOTAL CHLORINE AND FLUORINE (uB/g)
Ch lorIne F I uor 1 n»
* X
Measured RSD % Measured RSD X
Sample Expected* *_ a.d. (RFD) Recovery Expected* ~ s.d. (RPO) Recovery
VIrpln Oil*
Automoblle erankcase
Spiked w/inorganlc 6,663 6,623 — 99 1,091 820 — 76
haI Ides
Spiked w/26* 9,246 7,093 _~ 200 (4) 89 4,367 3,917 + 93 (3) 90
water end TFE
Spiked */26X water, 13,610 13,797 * 120 (1) 101 6,408 4,868 _~ 22 (1) 90
Inorganic halldea, ~
end TFE
Spiked w/26* water 10,474 9,922 * 210 2 85 1,088 899 ~ 24 3 83
and OM
Spiked w/inorganic 16,832 14,078 * 109 1 93 2,199 1,693 +19 1 78
ha I Ides and OM
Transmission fluid
Spiked w/6* 19,926 14,664 ~ 283 (3) 88 8,849 7,240 * 263 (6) 82
water and TFE
Waate 01 la
Automobile erankcase
Unsplked -- 2,372 * 360 IE -- — 101 ~ 10 10
Spiked w/inorganic 18,101 19,271 ~ 617 (4) 90 2,299 1,666_+ 61 (4) 73
halldea and OM
HydrauIi c oil
Unapiked — 4,487 + 321 7 -- — 61 ~ J 4
Spiked w/tnorganic 20,216 17,403 ~ 670 (6) 66 2,219 1,803 * 4S (4) 81
Kali del and OM
Grinding and cutting oil
Unapiked — 10,802 ~ 1,462 14 — — 98 ~ 3 3
Automoblle erankcase
Umplked — 271 ~ 26 (13) — — 116 ~ 8 (10)
Unknown source
Unapiked A -- 1,372 ~ 10 (1) — -- 44+4 (14)
Unapiked B -- 827 26 (4) -- — 41 V 2 (9)
'Expected value la the chlorine or fluorine content baaed on tplke level*.
a.d. = standard deviation.
TFE = trIchlorotr1fluoroethane.
OM a Organic mixture: 1,1,1-tr I eh I oroethene, trich I oroethjr lane, tetrach I or oethjr I ene, and TFE.
-------
TABLE III. RESULTS OF SEQUENTIAL EXTRACTIONS OF OIL SAMPLES FOR
INORGANIC HALOGENS wg/g
Measured
jh
%
SampleC Expected3
s.d.
RSD
Recovery
1. Virgin crankcase oil
Chlorine 5,449
5,482
+
47
1
101
Fluorine 1,090
865
3
1
79
2. Waste hydraulic oil
Chlorine 5,620
5,405
143
4
96
Fluorine 1,115
1,054
26
4
95
3. Waste crankcase oil
Chlorine 5,627
4,315
±
90
3
77
Fluorine 1,242
312
27
12
25
aExpected value is the inorganic chlorine or fluorine based on spike
levels.
Measured value is the inorganic chlorine or fluorine based on analyses
of aqueous extracts.
c
All spiked with inorganic and organic halogen mixture
s.d. » standard deviation
711
-------
No
i.e. >4,ooo
Yes
Yes
/ Any
T001. FOOZ
or similar
compound
> 100 ppm
^L«8B
than
1.000 ppm
Do not burn in
nonindustriaJ boiler,
oil is nazaroom
wade fuei
Used oil to be sold
for burning m
noomdustrial boilers
Determine totaJ
chk>nne content
Do ?*~<* num m
nocwndusinaJ
toiler, oil is off
specification
used oil fuel
Sum n ncntnoiistnaj
boiler as specification
used oil
Figure 1. Decision flow chart for regulation of burning of used oil and
waste oil fuel in nonindustrial boilers-total chlorine specification.
Tola! halogen determination
1. Bomo combustion
2. C analysts tor CI. Br, F
Characlonze s&mpie
source, type, °A> O, H20.
haiogen spika levels
Homogeniz»tton
aftquoting
"RxaJ inofgarHc halogen
determination
1. DluotuUon in totuene
2. Sep went i*J aqueous
extraciiorw
Oil Sample
TbtaJ organic halogen
determination
Obtain by difference *rom
determinations of total and
9xtractaD(e halogens .n
anginal sample
Aoueoua phase
Orge^tc phase
CI". Br". F"
by IC
!
Discard 1
i
Figure 2. Approach for halogen speciatlon in waste oils.
712
-------
EVALUATING TOE FIELD PERFORMANCE OF HIGH EFFICIENY AND CATALYTIC WOOD STOVES
S. Morgan, Technical Development Corporation, Boston, MA, and P. Burnet and
P. Tiegs, OMNI Environmental Services, Inc., Beaverton, OR.
I ¦ XiA t ^
The superior laboratory performance of catalytic and so-called "high
efficiency" wood stoves in reducing air emissions and improving combustion
efficiency had little impact in market penetration of these appliances
through the winter of 196^-5. Despite an Oregon certification standard ar.a
a Colorado statute, fewer than 10? of sale.*; in the Northeast induced these
high performance stoves. Convinced that both retailers and consumers
required credible information about the field performance of these
appliances, the Coalition of Northeast Governors (CONEG) and the New York
State Energy Research and Development Authority (NYSERDA) planned a field
performance study to examine emissions, efficiency and stove safety of high
performance stoves versus conventional air tight stoves. The Environmental
Protection Agency's (EPA) interest in the durability of catalysts over "ime
prompted their commitment to co-funding the two-year study. EFA's decision
to develop a New Source Performance Standard (NSPS) for wood stoves
coincided with CONEG and NYSERDA's decision to conduct the study.
In June, 1985, CONEG, serving as project coordinator, issued a $300,000
Request for Proposal (RFP) with the following objectives:
713
-------
(1) to measure the fuel savings of catalytic stoves, add-on catalysts and
high efficiency stoves against conventional air-tight stoves in Vermont and
New York State homes under actual operating conditions over a period of two
heating sessions;
(2) to measure the creosote build-up in the stovepipe chimneys of both
conventional air-tight stoves and the three categories of high performance
stoves listed in (1);
(3) to measure the durability of catalytic stoves via laboratory tests of
combustion efficiency of the combusters after one season, and after two
seasons, and in comparison to earlier laboratory tests of new cotnbusters
paid for by participating mar.ufacturers;
(4) to measure the total suspended particulates (TSP) emissions of
catalytic high efficiency and conventional air-tight stoves over the
duration of two heating seasons—1985-6 and 1986-7;
(5) to measure the POMs emmissions in a selected subsample cf the stoves
listed above tested for TSP emissions;
(6) to report these findings in comparison to measurements taken of control
wood stoves without catalytics and with high efficiency design
characteristics; and
(7) to discover possible stove or catalytic design changes cr operator
characteristics which improve the perforoance cf catalytic stoves.
714
-------
In August, 1985, CONEG's Technical Review Committee recommended OMNI
Environmental Services, Inc. as the strongest bidder of the five qualifying
proposals. Since September 1, 1985, OMNI has been under contract to CONEG.
II. Research Tasks and Methodology
To meet the objectives of the study, OMNI selected a total of 66 volunteer
households—half from Washington County, Vermont and half from the
Warrensburg, New York area. Over 1^0 households volunteered for the study.
The Vermont Agency for Environmental Protection and the New York State
Department of Environmental Protection utilized direct mail and media
outreach to recruit volunteers for the study. Each applicant mailed in a
completed questionnaire providing demographic, structural and wood appliance
information. OMNI utilized several criteria—previous wood stove operation
experience, safe chimneys, stove and instrumentation installation ease,
participant eagerness, geographical proximity and building structure
representativeness—to narrow the list. OMNI staff visited each applicant
household before making its final selections.
Each of the participants were placed in one of three categories—Group one
(32) were catalytic, high efficiency (characterized by extensive baffles,
secondary combustion chambers, secondary draft controls, insulated firebox
and/or other features to increase efficiency above 60% In accredited
laboratory tests) or conventional stoves instrumented for two years to
measure accurately fuel usage, stack, Indoor and outdoor temperatures, and
TSP emissions. Group Two (24) are homeowners who switch over from catalysts
715
-------
or high efficiency stoves tc conventional stoves from the first year to the
second or vice-versa. Group Three (6) are homeowners with catalysts which
have experienced at least one year of usage before the 85-86 heating season
and which will be tested throughout the next two heating seasons as their
performance permits. Six homes are available as back-ups in the event cf
drop-outs or methodological problems associated with the other 60 stoves.
All the participant homes have had their chimneys cleaned at the beginning
of the study and will receive cleanings twice during each heating season.
The creosote collected from the clearings will be weighed; a sample will be
sent to the Solar Energy Research Institute where a chromatography analysis
will determine the chemical composition. Hood piles cf every participant
ara seasursc and moisture content is determined at the beginning, during the
middle and at the end of each heating season. Each participant will also
receive a free energy audit of their homes during the study's first year.
Each participant agrees to keep a daily log for recording unusual events
which may affect fuel usage (e.g. grandmother comes for a visit, chimney
fire).
Group One homes have programmable microprocessing/data logging assemblies
and ir. site emissions samplers installed. The former compiles loaded fuel
weights ar.d stack, indoor and outdoor temperatures; the latter collects TS?
emissions. Of the thirty-two stoves in this category, twelve sre catalytic
stoves; twelve are catalytic add-on and retrofit units; four are high
efficiency stoves; and four are conventional air-tight stoves. (Table 1).
Group One homes will provide the most accurate fuel usage data and the only
emissions Gata for all stove types. Group One households will also provide
716
-------
two years of efficiency data for the catalysts.
Group Two homes are the so-called cross-overs: one year each participant
has a high performance stove; another year the household uses its own
conventional air-tight stove. The high performance 3toves include ten
catalytic stoves; ten catalytic add-ons or retrofit units; and four high
efficiency stoves. The major research objectives served by Croup Two
households are the creosote build-up and fuel usage comparisons between high
performance and conventional air-tight stoves. Most of the wide-ranging
variation in usage explained by structural and operator characteristics are
controlled for in this group. Special effort has been made to assure that
the conventional and high performance stoves are similarly sized in each
household.
Group Three households have catalyst stoves or add-ons with one or more
previous years of operatic experience. These catalysts are tested for
efficiency and emissions in the laboratory at the beginning and end of the
85-86 heating season and the following one, as performance permits. This
group is important for its contribution to data or. the durability of
catalysts. Estimates of the previous wood fuel usage experienced by each
catalyst are gauged by operator interviews.
Beginning in July 1985, the Technical Development Corporation—the program
manager for CONEG, NYSERDA and EPA—solicited manufacturer interest in
participating in the study. By late August, a dozen manufacturers,
including at least four catalyst stove, four catalyst retrofit, and four
high efficiency non-catalyst firms, had volunteered to donate up to twelve
717
-------
stoves or catalysts each. By the time OMNI made the final manufacturer
selection in October, another five manufacturers hac! volunteered. Several
of the selected models had passed Oregon's certification teat, incuding
high efficiency, non catalytic stoves. Twelve were chosen in all,
representative of models found in New York and Vermont and representative
of the stove designs and emissions performances available nationwide. A
listing of the participating manufacturers is included in Appendix A.
III. Data LOG'r and Emissions Sampler Description and Operation
Two pieces of specialized equipment are being used for this project. One is
a computerized data acquisition system/controller, used for recording
temperature, wood weight, coal bed status and flue gas oxygen concentration
data. This unit, dubbed the Data LOG'r TM, also controls the sampling
intervals of the emission sampling system described below. Ar. electronic
scale, mounted beneath a woodbasket, weighs the amount of wood used in each
wooc'stove. This data, with the condition of the coal bed at tie time cf
fuel loading, are recorded in a solid state memory device. Four weeks of
continuous data can be recorded at 5-cir.ute intervals without downloading.
The Automated Woodstove Emissions Sampler (AWES) is controlled by the Data
LOG'r. At preprogrammed tines, the AVES pulls flue gas througr. a heated
filter and an XAD-2 sorbent resin cartridge to obtain a particular sample.
The AWES is designed to operate unattended for one week, resulting in ar.
integrated sample for that period. The sampling rate is controlled by a
critical orifice, which maintains constant flow. The total sample volume is
determined by the time the AWES pump has operated. An oxygen sensor
718
-------
measures flue 02 concentrations, which are recorded by the Data LOG'r.
IV. Testing Methodology
The total sampler particulate catch and gas volume sampled allow calculation
of particulate concentration in the flue (grarns/m3). Wood use data,
temperatures and flue oxygen concentrations are used to calculate flue gas
flow rates. Particulate emissions per heat output (grans/10 6 joule) can be
calculated using wood moisture and stove efficiency values. Emission rates
and factors (grams/hour and grans/kilogram fuel) can also be calculated.
Samplers are placed in various locations in the stove/chimney system. Most
homes are equipped with 2 AWES systems during sampling periods (one week per
month, H months per heating season). Sampler probes are placed belcw a
catalytic combustor, at the stove flue collar, above an in-flue catalytic
add-on or at the chimney exit. This arrangement allows determination of
catalytic combustor efficiency, measures disposition of material in the
chimney system (as creosote) and actual emissions to the ataosphere. Flue
collar measurements allow comparison of stove performance between homes
while minimizing flue deposition effects.
POM analysis will be conducted on extracts from the XAD-2 resin. GC/MS
analysis for eight POMs will be conducted. These FOMs will be reported in
the same units used for particulates.
The AWES sampler is currently undergoing comparative testing with a modified
EPA Method 5 train to determine comparability. Preliminary results indicate
719
-------
good correlation.
V. Problems Encountered
The logistics of conducting in-home monitoring and testing in 66 hones in
two regions simultaneously under mid-winter conditions are complex. Poor
weather and widely distributed study homes slew all activities. Homeowner
cooperation has been good, in part due to careful pre-study screening.
Several equipment problems delayed the start cf data acquisition. Data
LOG'r systems were found to have several defective integrated circuits which
require software corrections and chip replacement. Additionally, some units
were found to generate low intensity radio frequency (RF) signals, which in
rescte areas with poor signal strength interfered with TV and radio
reception during data acquisition periods.
AWES samplers experienced few problems when located inside the home, but
rooftop samplers required some modifications to withstand winter conditions.
Sample line heaters and lower compartment heaters were added to prevent
freezing. In one case a large ham radio antenna created signal interference
for the AWES pump relay and 02 sensor. Rooftop installations have been
difficult to service due to heavy snow.
Some homeowners have reported difficulties with study stoves. Several
catalysts have disintegrated after 3 months of use, requiring replacement.
Condensation of water in seme flues has resulted in ice buildup in lower
chimney sections near the ash clean-out doors. In one case a
water/creosote mixture leached through chimney masonry into the living area.
720
-------
Some complaints of inadequate beat output have also been received. Overall,
however, most homeowners appear to be quite pleased with their high
efficiency stoves.
VI. Preliminary Teat Results
Over three months of wood use, temperature and emission data have been
collected in the 32 primary homes. Wood piles measurements and user log
books are being compiled for 2U additional homes. Emissions data have been
obtained for 6 existing catalytic stoves. Data processing ar.d analysis is
beginning as computer software is developed to compile the field data. Some
preliminary findings include:
• Wood loading in stove appears to be lighter than previously thought.
Values of 30 to 60 kilograms per cubic meter (5 to S kilograms per cubic
foot) appear to be typical.
• Creosote accumulation is highly variable and appears to be a function of
stove operation.
• Catalyst operating temperatures indicate that some combustors may not be
operating for a significant fraction of stove operating time.
Data review and analysis will proceed rapidly through the spring and summer.
An interim report will be presented to CONEG in mid-summer and will contain
data from the first year of data gathering and analysis.
721
-------
Table I. COUEG Study Stove Types
Group I (32
homes + 4
homes as
back-ups--
mixed stoves)
Group II£
(24 homes)
Integrated
Catalyst
12
Catalytic
Add-on/
Ret rof it
12
High
Efficiency
Co-nv£niLi- s nil!
Existing (Low
Efficiency
canvsnfclanajU
10
10
(one year
only)
Group III
(6 homes)
Totals
2 8
22
Stove switched frc>r» conventional
between heating seasons
to high-effjciem
dev ice
722
-------
Appendix 1
Msnurscturfirs Participating in CstsivtlG Field Study
American Eagle
Brugger Exports
Catalytic Damper, Inc.
C ( D Distributors
CESCO Industries
Hearthstone
Nu-Tec
Pacific Energy
The Earth Store, Inc.
Vermont Castings
Vermont Iron, Inc.
Woodcutters Manufacturing, Inc.
Catalytic
Low Emissions
Add-on
Add-on
Low Emission
Catalytic
Add-on
Low Emission
Add-cn
Add-on
Catalytic
Ca taly ti c
723
-------
A SYSTEM TO OBTAIN TIME INTEGRATED WOODSTOVE
EMISSION SAMPLES
James E. Houck,
Carl A. Simons, Paul G. Burnet
OMNI Environmental Services
Beaverton, Oregon
Raymond G. Merrill
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina
A novel system especially designed to obtain time integrated emission
samples from wooastoves during normal in-nome operation has been developed.
The system is comprised of a programmable data logger, a particulate
sampler, a wood-use scaie, a coal bed status recorder, and temperature
sensors. A continuous record of time and woodstove operational parameters
is stored in a nonvolatile solid state memory cartridge. Particulate
sampling frequency and duration are controlled by the data logger.
Relatively infrequent, short-duration samples can be collected over a long
time period to provide a representative integrated sample of woodstove
emissions which are inherently highly variable. In addition to particulate
emissions, woodstove use patterns, reliance on other heat sources, catalyst
operation, and typical fuel load densities can be studied with the data
base.
Preliminary data collected from homes in Vermont and Oregon during the
1985/1986 heating season are presented here. Mass of particles emitted
per mass dry wood burned (emission factors), mass of particles emitted
per unit heat output, and mass of particles emitted per hour of stove
operation have been calculated for the woodstoves in these homes.
Illustrative records of woodstove use and catalyst operation patterns
are also presented.
724
-------
Introduction
Residential wood combustion (RWC) is a significant source of parti-
culate and carbon monoxide emissions.^ Not only can RWC be considered as a
major source of particles and carbon monoxide when compared with other major
nationwide pollutant categories such as motor vehicles and industrial point
sources (Table I), but locally the impact of RWC can be very high due to its
seasonal and regional nature. Exceptionally high atmospheric concentrations
of RWC pollutants are often reached during the heating season in communities
with poor dispersion caused by valley terrain and wintertime inversions.~<
Due to the roof-level, residential source of RWC emissions, human exposure
is at a near maximum. Particles originating from RWC contain polycyciic
organic material (POM) 14 which has well-demonstrated carcinogenic and
mutagenic properties. J
Unlike more traditional point sources, the combustion emissions from
RWC are difficult to quantify. A wide variety of woodstove appliances are
commercially available, a wide variety of wood fuel (wood species and
moisture content) are utilized, and operating practices, of course, vary
widely from home to home. This large number of possible parameters make
laboratory testing of woodstoves of limited utility in assessing overall
RWC emission levels characteristic of a community. In addition to the
variability which is characteristic of RWC, woodstove emissions are
pragmatically difficult to sample. Slow stack gas velocities, a high
concertsible organic content, and a relatively high water vapor content
require special modifications of traditional stack sampling techniques to
obtain accurate, reproducible results.7
Attempts to quantity RWC impacts by emission inventories, ambient
sampling, tracers, and modelling have all met with only moderate success.
The difficulty in quantifying wood use and emission factors for an area-
wide, individualistic source such as RWC makes the results of emission
inventory and dispersion modelling approaches, in nost cases, illustrative
rather than definitive. The ubiquitous chemical and physical character-
istics of woodstove emissions limit the accurate application of ambient
sampling, tracer, and receptor modelling approaches to specialized
situations and, in most cases, results of such approaches can also be
considered rr.ore illustrative than quantitative.
In an effort to measure woodstove emissions in a "real-world" setting
and to provide data that will improve RWC impact assessment, a relatively
low-cost, programmable data logger (trademark Data LOG'r)/automated wood-
stoves emission sampler (AWES) system was developed. The system was
designed specifically for the in-home, long-term integrated measurement of
RWC emissions. Ancillary data, such as indoor, outdoor, flue, and catalyst
temperatures, real-time wood usage, coal bed status, and auxiliary heater
operation are also automatically recorded with the system. The design
and operation of the system, as weil as preliminary data obtained at
several homes during the 1985/1986 heating season, are presented here.
Instrument Design and Experimental Methods
A schematic illustration of the Data LOG'r/AWES configuration is shown
in Figure 1. The AWES configuration shown in Figure 1 is primarily for the
collection of particulate (including semi-volatile organic compounds)
samples for subsequent mass determination and POM analysis. The sampling
frequency, sampling duration, and sampling period are controlled by the
Data LOG'r which is programmed prior to sampling. The sampling frequency
used to generate the preliminary data presented here was once every 30
725
-------
minutes. The sampling duration was one minute and the sampling period was
one week. Consequently, a one week sample (10,080 minutes) represents 336
one minute samples collected at 30 minute intervals. Any combination of
sampling frequency, pericd and duration could have been programmed.
A stainless steel inlet prcbe was attached to the woodstove or flue.
Several points of attachment have been used depending on the stove type
(i.e., conventional, integrated catalytic, or retrofit catalytic). The
points of attachment generally used were: (1) the stove firebox, (2) the
flue collar, (3) the flue above the retrofit device, or (4) the chimney
exit. Teflon (trademark) tubing was used to connect the sampling probe to
the AWES system. The Teflon tube was sloped such that any condensed water
would drain into the heated filter chamber. The filter chamber was operated
at 93 ± 25°C. A 100 rci binderless glass fiber filter was used in a glass
EPA method 5 filter holder. After the filter, the sample flow was passed
through a Teflon cartridge (3 err1. I.D. X 9 cm length) containing approxi-
mately 30 grams of XAD-2 resin. The temperature of the XAD-2 resin was not
controlled. Experimentation revealed that the XAD resin temperature was
generally about 6°C above ambient temperature due to the heating effect of
the filter chamber and the air pump motor adjacent to the XAD-2 column.
After the XAD-2 column, the sample flow passed through approximately 300
grams of 6-16 mesh indicating silica gel to remove water. The sample flow
then passed through a Millipore Corporation one liter per minute (nominal)
critical orifice. The flow through each critical orifice was calibrated
with a wet flow meter prior to installation into the AWHS system. The
sample flow was then passed through the pump. On the exhaust side of the
pump, the oxygen content of the gas stream was measured with a Catalyst
Research Corporation model 472062 oxygen sensor cell. The millivolt output
(5-15 mv at 20% O2) was recorded with the Data LCG'r. Flue gas oxygen
content is a key parameter in the calculation of total flue gas flow
(volume) during the sampling period. After passing through the oxygen cell,
the sample stream was exhausted back into the woodstove flue to prevent any
indoor air quality impact. A leak check of the sampling system was con-
ducted upon installation at each home.
In addition to controlling the AWES sampler and recording the flue gas
oxygen content, the Data LOG'r recorded: (I) time, (2) various temperatures
measured with thermocouples and solid state temperature ser.sors, and (3)
was interfaced with a scale and key pad which permitted wood used and coal
bed status to be recorded. Table IT is a summary of the data which were
recorded with the Data LOG'r.
Room temperatures, the internal temperature of the Data LCG'r, the
outdoor temperature, and the temperature at a point in or adjacent to any
auxiliary heater were measured with National Semiconductor LM334 solid state
temperature sensors. The sensor in or adjacent to the auxiliary heat source
was used to determine the total time the auxiliary heater was in use. A
threshold temperature of 3S°C was generally used for this purpose. Type K
thermocouples were used to measure flue and catalyst temperatures.
Catalyst temperatures in excess of approximately 316°C were used as an
indication that the catalyst was ignited.
The Data LOG'r was interfaced with a commercially available electronic
scale and a key pad. Wood was weighed each time it was added to the wood-
stove, and the homeowner entered a description of the coal bed status via
the key pad at the time of wood addition. Four coal bed status categories
were available for entry. These were: (1) empty or out, (2) even loading
of glowing coals, (3) large pieces of burning wood, or (4) large pieces
of unburned wood. The scale was calibrated upon installation at each home
726
-------
with a 4.54 kg weight.
Each Data LOG'r contained an auxiliary battery pack for operation
during power failures. The length of any power failure was recorded. An
audible system failure alarm was also a component of each Data LOG'r.
Data storage was accomplished with a Dallas Semiconductor nonvolatile
32K, solid state memory cartridge. The cartridge was removed from the Data
LCG'r on completion of the week-long sampling period. The data from the
memory cartridge was down-loaded via a specially designed data cartridge
reader to a floppy disk in a compressed hexadecimal data format. Subsequent-
data manipulation was performed with IBM PC compatible software.
At the time of sampler installation, miscellaneous information such as
stove use, stove make, model and age, wood species and age, and other house-
hold characteristics were obtained from the homeowner. Wood moisture
content was also measured with a Delmhorst Instrument Company wood moisture
detector.
The calculated mass of particles collected with the AWES system was the
sum of: (1) the mass of particles collected with the heated filter, (2) the
mass of material extracted from the XAD-2 resin, and (3) the mass of
material removed from the probe, inlet line and interconnecting glassware
with methanol and methylene chloride rinses. The XAD-2 resin underwent
Soxhlet extraction with methylene chloride for 24 hours. The solution from
the Soxhlet extraction, as well as the methanol and methylene chloride
rinses, were evaporated at room temperature. The mass of the remaining
residue was determined with an analytical balance using pre-weighed beakers.
The mass of the filters before and after sample collection was also deter-
mined with an analytical balance. Beakers and filters (clear, and with
sample) were desiccated for 24 hours at 29 to 38% relative humidity. They
were then weighed every six hours thereafter until a constant weight was
achieved. Blanks were prepared for all aspects of the gravimetric/
extraction/rinsing procedures.
Samples selected from POM analysis were spiked with surrogate stan-
dards. Three milliliters of a methylene chloride solution containing 6.00
mg/ml 9-phenylanthracene and 6.11 mg/ml 9-methylant'nracene was added to the
XAD-2 cartridges and allowed to stand for two hours prior to the Soxhlet
extraction. Blank XAD-2 cartridges were also spiked and extracted. One
half of the Soxhlet extract solutions were used for gravimetric deter-
minations and one half were concentrated with a Kuderna-Danish flask.
Analysis was conducted on the concentrate for eight lower molecular weight
POM compounds by GC/MS. The eight compounds were: (1) napthalene, (2)
acenapthene, (3) acenaphthylene, (4) flucrene, (5) phenar.threne, (6)
anthracene, (7) fluoranthene, and (8) pyrene.
Throe methods for normalizing and presenting particulate (and POM) data
have been incorporated into the data reduction programs. These are: (1)
mass of particles per mass of dry wood burned (emission factors), (2) mass
of particles per unit of heat output, and (3) mass of particles per unit of
time of stove operation. While it is outside the scope of this discussion
to present the complete derivation of the equations used to calculate these
three parameters, the formulas used are as follows:
Mass of Particulate Emissions/Mass Dry Wood Burned = (1)
(MP) (SV)/(FR) (SD) (1-(% O2/20.9%)) ,
727
-------
Mass of Particulate Emissions/Heat Output -- (2)
(MP) (SV)/(FR) (SD) (HO) (EF) (1 + WDB) (1 - (% 02/2Q.9%)) , ar.d
Mass of Particulate Emissions/Time Stove Operation = (3)
(MP) (SV) (MWW) / (FR) (SD) (SP) (HWDB) (1 - (% 02/20.9%)) ,
where,
MP is the mass of particles collected with the AWES system;
SV is the stoichiometric volume of dry gas produced from the complete
combustion of wood with a correction for the carbon monoxide
content typicaL of the various woodstove types (e.g., 2% by weight
for traditional stove models), The stoichiometric volume can be
calculated from the elemental carbon, oxygen, hydrogen, and
nitrogen content characteristic of each species of wcod;^
FR is the AWES flow rate as controlled by the critical orifice
(approximately 1 1pm);
SD is the total sampling duration (sampling duration X number of
sampling events!;
% O2 is the mean oxygen content of the flue gas during sampling;
HO is the heat output characteristic of each species of wood;8
EF is the efficiency factor characteristic of each stove model, burn
rate, and wood moisture content. The EF value is the overall
efficiency which is the product cf the combustion and heat trans-
fer efficiencies. Semi-quantitative estimates of combustion and
heat transfer efficiencies can be made from woodstove operation
- • ^ ¦ 9
conditions ; J
WEB is the moisture content of the wood fuel on a dry basis;
MWW is the total amount of fuel burned curing the sampling period on
a wet basis; and
SP is the sampling period.
While the AWES/Data LOG'r system was located at each home for one week
(10,080 minutes), during which 336 one rainute sampling events occurred
(30 minutes apart), the sampling period (SP) and the total sampling
duration (SD) used for calculational purposes were generally less than
10,080 minutes and 336 minutes, respectively. Only data which was collected
when the flue temperature was greater than 38°C as recorded by the Data
LOG'r were used. The 38°C threshold was used as an indication that the
stove was in operation. As with the SP and SD values, the mean oxygen
content (% Op) for the time period when the flue temperature was greater
than 38°C only was used for the calculation of particulate emission levels.
Results
Preliminary particulate data for one week, of sampling during the 1985/
1986 heating season at each of six homes in Vermont ar.d Oregon are presented
in Table III. While this preliminary data set is very limited, the parti-
culate emission levels calculated for the woodstoves are reasonable ir.
comparison with the U.S. EPA AP-42 emission factor for woodstoves1'"' and the
state of Oregon standards.11 The emission factors for the six hones ranged
from 8.2 grams/kg dry wood for a catalytic retrofit stove, to 20.4 grams/kg
dry wood for a traditional stove. The U.S. EPA AP-42 value is 21 grams/kg
dry wood. The calculated mass of particles emitted per hour of stove
operation ranged from 11.4 grams/hour to 23.2 grams/hour among the six
stoves. The state of Oregon 1986 weather weighted standards are 6 grams/
hour for catalytic stoves and 15 grams/hour for non-catalytic stoves.
Interestingly, while there was a relatively small difference for the
728
-------
emission factors (mass particles/mass dry wood) and for the mass of parti-
cles per heat output values between the two traditional stoves studied in
Oregon, their mass of particles per hour of stove operation values were
dramatically different (Table III). Upon review of the Data LOG'r records,
it was observed that the mean burn rate was significantly higher for the
stove with the higher mass of particles per hour value than for the other
stove (1.86 kg wood/hr vs. 1.06 kg wood/hr). This simply implies that more
wood burned per unit tine was responsible for more particles being emitted
per unit time. When the particulate emissions were divided by the mass of
wood burned or the total heat output, the values were in effect normalized,
albeit many other parameters besides burning have been shown to affect par-
ticulate emission levels.
The ability of the Data LOG'r system to track and record woodstove use
characteristics is shown in Figures 2 ana 3. Mean hourly flue temperatures
calculated from measurements made every five minutes and mean hourly flue
oxyaen concentrations from measurements made every thirty minutes are
illustrated fcr a traditional stove over a twenty-four hour period (Figure
2). Mean hourly catalyst temperatures calculated from measurements made
every ten minutes ar.d mean hourly flue oxygen concentrations from measure-
ments made every thirty minutes are also illustrated for a retrofit catalyst
stove over a twenty-four hcur period (Figure 3). The hourly periods when
wood was added to the stoves is shown in both Figures 2 and 3. As can be
seen in Figure 2, wood was added to the stove in the morning and in the
evening, ostensibly when the occupants arose in the morning and returned
home in the evening. Corresponding to the addition of wood, flue tempera-
ture rase and flue oxygen concentrations fell. Similarly, the dramatic
increase in catalyst temperature and drop in oxygen concentration can be
seen for a retrofit catalytic stove when wood was first added in the morning
(Figure 3). While it is useful to monitor and record wood stove operating
parameters as illustrated in Figures 2 and 3, to evaluate such factors as
wood stave use patterns, diurnal changes in atmospheric pollutant levels,
burn rates, fuel load densities and catalyst performance, an equally
important use of the data is to control sampling equipment on a real-time
interactive basis via the programmable Data LOG'r or to assist in subsequent
data reduction. For example, emission samples could be collected only when
the catalyst was ignited or during the time immediately following wood
addition. The particulate emission data presented in Table III was, as
discussed, only calculated for the time period when the stove flue tempera-
tures were above 38°C.
It must be emphasized that the data presented here is preliminary and
represents a very small fraction of the total information that will be
collected during the 1985/1986 and 1986/1997 heating seasons under current
programs. Approximately one hundred and ten integrated (week-long) parti-
culate samples will be collected at forty-three homes in Oregon, Vermont,
and New York during the 1985/1966 heating season alone. Woodstove opera-
tion parameters (Data LOG'r and sensors only) are also being continuously
recorded in an additional twenty homes in Oregon during the 1985/1966
heating season. The analysis of particulate samples for FOM was in process
at the time of this writing. It is anticipated that the extensive data base
generated by the AWES/Data LOG'r system will provide significant insight
into the engineering and environmental issues that currently surround wood-
stove use and design.
Conclusions
The AWES/Data LOG'r system which has been especially developed for the
in-home collection of long-term integrated woodstove emission samples has
729
-------
been deployed during the 1985/1986 heating season at some forty-three homes
in Oregon and New England. Preliminary particulate samples and wooastove
use data from homes located in Vermont and Oregon have revealed the quality
and extensiveness of the data base which can be provided by the system.
Future applications of the programmable Data LOG'r would include the inter-
active operation of samplers for the collection of samples for various types
of subsequent chemical and biological analyses, as well as the continuous
collection of particulate samples with the existing AWES system to further
define the emission factors and particulate impacts characteristic of
woodscoves.
Acknowledgments
The work presented here was funded in part by the Coalition of North-
eastern Governors, Bonneville Power Administration, U.S. Environmental
Protection Agency, Wood Heating Alliance, New York State Energy Research
and Development Authority, and Missoula City and County Health Department.
The authors wish to thank Mr. Stephen J. Morgan of Technical Development
Corporation, and Mr. Patrick J. Fox and Mr. Garry C. Insley of the
Bonneville Power Administration for their cooperation and assistar.ee.
References
1. Nero and Associates, Inc., "A national assessment of residential wood
combustion air quality impacts," final report submitted to Putnam
Hayes and Barlett, Inc. and U.S. Environmental Protection Agency, PH6B
work assignment no. 147 and EPA contract no. 6B-01-6543, (1984) .
2. J.H. Carlson, "Residential wood combustion in Missoula, Montana: An
overview of its air pollution contributions, health effects, and
proposed regulatory solutions," p. 539-550, in. Residential Solid Fuels:
Environmental Impacts and Solutions. J.A. Cooper and D. Maiek, eds,
Oregon Graduate Center, Beaverton, Oregon, 1982.
3. T. Chappie, "Characterization and control of residential wood smoke
pollution in Juneau, Alaska," p. 349-362, in, proceedings of the 19S5
CPNS and PNIS joint annual meeting, Calgary, Alberta, (Nov. 1985).
4. D.G. DeAngelis, D.S. Ruffin, R.B. Reznik, "Preliminary characterization
of emissions from wood-fired residential combustion equipment," U.S.
Environmental Protection Agency, Washington, D.C., EPA-600/7-30-040,
(1980) .
5. J. Lewtas, "Comparison of the mutagenic and potentially carcinogenic
activity of particle bound organics from woodstoves, residential oil
furnaces, and other combustion sources," p. 606-619, in. Residential
Solid Fuels: Environmental Impacts and Solutions. J.A. Cooper and
D. Malek, eds, Oregon Graduate Center, Beaverton, Oregon, 1982.
6. S. Hytonen, I. Alfheim, M. Sorca, "Effects of emissions from residential
wood stoves on SCE induction in CHO cells," Mut. Res. 118:69 (19B3).
7. Oregon Department of Environmental Quality, Standard Method for
Measuring the Eraissions and Efficiencies of Residential Wood Stoves,
Portland, Oregon, June, 1984.
8. Solar Energy Research Institute, "A survey of biomass gasification,
volume II - principles of gasification," U.S. Department of Energy
contract no. EG*77*C,0114042, (July 1979).
730
-------
9. S.G. Barnett, Handbook for Measuring Woodstove Emissions and Efficiency
Using the Condar Sampling System, Condar Company, Hiram, Ohio, August
1985.
10. United States Environmental Protection Agency, "Emission factor document
for AP-42: Section 1.10, residential wood stoves, EPA-450/14-82-003,
(Jan. 1984).
11. Oregon Administrative Rules 340-21-120, (1984).
731
-------
TABLE I. NATIONAL EMISSION INVENTORY
DATA FOR PARTICLES AND CARBON
MONOXIDE3
Source Particles
Category (Metric tons X 10^)
Carbon Monoxide
(Metric tons X 10')
Residential Wood
Combustion
830
5,119
All Point Sources
Motor Vehicles
4,397
1,112
/ , 574
63,670
Data from reference 1
TABLE II. PARAMETERS RECORDED AND/OR
CONTROLLED 3Y THE DATA LOG'R
1. Sampling frequency
2. Sampling duration
3. Sampling period
4. Time
5. Flue O2 content
6. Room temperature
7. Data LOG'r internal temperature
8. Outdoor temperature
9. Auxiliary heat temperature (time heat source is in operation)
10. Flue temperature
11. Catalyst temperature
12. Real-time wood weight
13. Coal bed status at time of wood addition
14. Time and length of power outages
732
-------
TABLE TTI. PARTICUTATE EMISSION LEVELS FROM REPRESENTATIVE WOOD STOVES
Wood Fuel
Particulate Emissions*5
Stove Type/Location
Species
Mois ture°
(%)
gram particles/
kg dry wood
(emission factor)
gram particles/
106 joules
(heat output)
gram particles/
hour
{stove operation)
Catalytic Retrofit,
Vermont
Bench
3 2
8.2
0.47
11 .4
Catalytic Retrofit,
Vermont-
15%
85%
Beech,
Mapl e
30
18.5
1.10
28.2
High Efficiency
Conventional, Vermont
Maple
21
11.9
0.76
12.7
Integrated Catalytic,
Vermont
50%
S0%
Beech,
Map 1 e
16
10.8
0.66
18.7
Traditional,
Oregon
Maple
27
19.0
1.36
27.8
Traditional,
Oregon
Alder
20
20. 4
1.64
17 .B
a.
dry basis
particulate emissions wen; calculated for only the time during the week-long sampling periods when the stove
was in operation, i.e., when the flue temperaturo was greater than 38°C
-------
SS3
OUT
DOORS
SS2 _
ROOM
SS1
1 MEMORY
CARTRIDGE
2 PROGRAMABLE
SOFTWARE
3. AUX. BATTERY
PACK
4. FAJLURE ALARM
EXHAUST RETURN
THERMO-
COUPLE 2
TO STOVE
CATALYST
[THERMOSTAT]
AND HEATER
THERMOCOUPLE 1
INLET
iFlLTERj
HEATED
CHAMBER
XAD
PUMP CONTROL
Data LOG'r
TM
HEAT
SOURCE
PUMP
WOOD SCALE
KEY
PAD
SILICA
GEL
ORIRCE
J
t
t
T
WOOD STOVE
AWES
FIGURE I. SCHEMATIC AWES/DATA LOGGER SYSTEM
-------
600
Degraas
Fahrenheit
200-
0-
20-
Percant
Oxygen
15-
wood wood
wood
wood
NOON
MIDNIGHT
MIDNIGHT
Tims of Day
FIGURE 2. MEAN HOURLY FLUE OXYGEN CONTENT AND
FLUE TEMPERATURE, TRADITIONAL STOVE
15001
1000-
Degrees 750
Fahrenheit
500
20-
15"
Percent
Oxygen
10-
wood wood
l—I I—i
wood
wood.
wood
NOON
MIDNIGHT
MIDNIGHT
Time o( Day
MEAN HOURLY FLUE OXYGEN CONTENT AND
CATALYST TEMPERATURE, RETROFIT STOVE
735
-------
RESIDENTIAL WOOD COMBUSTION IMPACTS
ON INDOOR CARBON MONOXIDE AND
SUSPENDED PARTICULATES
Hallory P. Humphreys,1 HHflHS
Charles V. Knight,* John C. Pinnix1
lEnergy Use Test Facility, Tennessee Valley Authority
Chattanooga, Tennessee
•University of Tennessee at Chattanooga, Under Contract to TVA
Chattanooga, Tennessee
During the past two decades much effort has been expended in evaluation
and abatement of pollutant sources associated with ambient air quality.
Only within the past few years has similar attention been given to indoor
air quality.
Recent studies conducted by Tennessee Valley Authority during the winters
of 1983, 1984, and 1985 have evaluated the impacts of both airtight
(catalytic and conventional) and non-airtight wood heaters on indoor air
quality in a weatherized home. Carbon monoxide and suspended particulate
results for the three studies will be presented in this paper. Depending
upon the operating conditions, the wood heaters were found to represent a
major source of indoor carbon monoxide and suspended particulates.
Several other pollutants (nitrogen oxide and polynuclear aromatic
hydrocarbons) were also found to be associated with residential wood
combustion.
736
-------
RESIDENTIAL WOOD COMBUSTION IMPACTS ON
INDOOR CARBON MONOXIDE AND SUSPENDED PARTICULATES
Introduction
Indoor air quality associated with use of residential wood heaters has
become a matter of importance within the past decade because of increased
use of wood heaters for space heating. The use of wood heaters for such
purposes has also contributed to ambient air quality problems, especially
in some densely populated urban areas. The data base for indoor air
quality associated with the use of wood heaters in older homes is very
limited, while that for newer, weatherized homes has only recently been
Investigated by Moschandreas (1-2), Traynor (3-4), Knight (5-6), and
others.
The present study was conducted during the winter months of 1983,
1984, and 1985 and was developed to determine the impacts on indoor air
quality (IAQ) associated with operating both airtight (conventional and
catalytic) and non-airtight wood heaters in a weatherized home. The
Tennessee Valley Authority (TVA) and Bonneville Power Administration (BPA)
jointly funded the first and third years, while the Consumer Products
Safety Commission (CPSC) funded the second year. The test program was
conducted by the TVA Energy Use Test Facility staff at Chattanooga,
Tennessee.
Experimental Methods
Test System
The test home was a relatively tight (ACH = 0.4), unoccupied
residential home with an interior volume of 337 cubic meters. The wood
heater to be tested was located in the living room and was placed on
electronic weight scales for fuel burn rate determination.
The wood heaters tested during this study included three conventional
airtight (AT) units, six catalytic AT units, and three non-airtight (NAT)
wood heaters. Each of the wood heaters was tested over a broad range of
burn rates associated with damper control in an attempt to determine a
relationship between indoor pollutant generation and the wood heater
operating mode.
Red oak. cordwood (approximately 25-percent moisture, wet basis) was
used as a test fuel throughout the three-year test program. In addition,
pine cordwood fuel was used during testing in 1985. Limited testing
associated with the use of very high and very low moisture fuels (both oak.
and pine) was also completed during 1985.
Continuous Sampling Methods
Indoor and ambient air samples were monitored using electronic
analyzers with CO, NO, NO2, N0X> 03, C02, 02, HC, and S02
concentrations recorded and stored on magnetic tape at the end of each
737
-------
4-minute sampling period. Particulate matter for both indoor and outdoor
locations wa3 continuously monitored with an HRI integrating nephelometer
with output recorded for each 8-minute interval.
Integrated Sampling Methods
Total suspended particulates (ISP) (< 15 ym) and respir&ble
suspended particulates (RSP) (<2.5 ym) were collected from two indoor
and three outdoor locations using stacked filter unit (SFU) dichotomous
particulate samplers provided by the Crocker Nuclear Laboratory at the
University of California at Davis. The Crocker Nuclear Laboratory
performed gravimetric as well as particle-induced X-ray emission (PIXE)
analysis for each integrated sample. Polynuclear aromatic hydrocarbons
(PAH) were collected by use of sorbent XAD-2 resin traps. The PAH results
were reported in 1985 at the Tenth International Symposium on Polynuclear
Aromatic Hydrocarbons (5).
Air Infiltration
Sulfur hezafluoride (SF$) tracer gas (as described in the ASTH
Standard E741-80) was injected into each area of the test home and allowed
to decay through natural infiltration. A linear regression using the
natural logarithm of the concentrations was used to determine the air
exchange rate (ACH) for the test home. This technique enabled variable
ACH values which existed during each test period to be evaluated.
Results
General
Detailed TVA test reports (7, 8, and 9) have been prepared for each of
the 1983, 1984, and 1985 winter test programs. The final report for the
1985 winter study (9) also contains extensive comparisons with results
from the previous two studies. The airtight (AT) and non-airtight (NAT)
wood heaters tested during each of the three studies will be referenced in
this paper by the year in which they were tested and the heater number
assigned to them during that winter test sequence.
A comparison of the indoor carbon monoxide (CO) and total suspended
particulate (TSP) results found for airtight (AT) and non-airtight (NAT)
wood heaters tested is presented in Table I. The CO and TSP source
strengths and indoor-to-outdoor ratios observed during testing of the NAT
wood heaters were generally higher than those for the AT wood heaters. CO
and TSP source strengths for the NAT units varied from 210 to 530 mg/hr
and from 11.9 to 20.6 mg/hr, respectively, while those for the AT units
(excluding the 1983 wood heater 4) ranged from 55 to 182 mg/hr and from
4.1 to 7.5 mg/hr, respectively. The results for catalytic wood heater 4
in the 1983 study were not considered to be typical of AT wood heaters,
because the unit had severe leakage around the door. This problem has
since been corrected by the manufacturer. Wood heater 3 in the 1985 study
represented that manufacturer's latest model. The results presented in
Table I show that the newer model had the lowest average CO source
strength for any wood heater tested.
738
-------
Test-averaged CO source strength and concentration operating ranges
for each of the wood heaters tested are presented in Figure 1. The NAT
wood heaters operated with CO source strengths similar to those of the AT
units when operated under optimum (fully open or intermediate damper
setting) firing conditions. However, when operated under "worst case"
conditions (stack damper(s) closed), the NAT units produced much higher CO
source strengths. NAT wood heater 4 (Franklin-type, freestanding
fireplace) generated a 12-hr averaged CO source strength of 3500 mg/hr
during its "worst case" firing mode. All three of the NAT units operated
with CO source strengths exceeding the high range of 500 mg/hr established
by Moschandreas (1) using similar modeling for indoor CO concentrations
generated by ga3 heating and cooking appliances. It is important to note
that the NAT units operated with CO source strengths comparable to AT wood
heaters when operated under more favorable firing conditions using less
damper control. All of the AT units operated with "worst case" CO source
strengths less than the high range of 500 mg/hr established by
Moschandreas, and all catalytic AT units (except 1983 wood heater 4) had
source strengths below the medium range (300 mg/hr) as established by
Moschandreas.
As with source strengths, the NAT wood heaters operated with indoor CO
concentrations similar to those of the AT units when operated under
optimum firing conditions. However, their "worst case" firing mode
produced indoor CO concentrations much higher than for AT units. Table I
shows a maximum hourly indoor concentration of 29.6 ppm associated with
the "worst case" use of NAT wood heater 4 (a Franklin, freestanding
fireplace heater). During the same test a 12-hr indoor CO level of 18.6
ppm was generated, which exceeds the 8-hr National Ambient Air Quality
Standard (NAAQS) for CO (9 ppm) by a factor of two. Peak indoor CO
concentrations were found generally to be episodic with wood heater fuel
reloadings.
Test-averaged TSP source strength and concentration operating ranges
for each wood heater are presented in Figure 2. TSP source strengths for
the AT wood heaters (except the 1983 wood heater 4) were all less than 15
mg/hr, while that for the Franklin-type NAT wood heater was as high as 65
mg/hr during its "worst case" mode of operation. Only 1983 AT wood
heater 4 generated an indoor TSP source strength similar to those of the
NAT wood heaters. However, the results shown in Figure 2 indicate that
the newer model of this same wood heater (1985 wood heater 3) operated
with less overall impact on TSP than any other heater tested in 1985.
The box-type NAT units, during "worst case" operation, generated
indoor TSP levels which exceeded the 24-hr secondary NAAQS for TSP (150
pg/ra3), while the Franklin-type NAT wood heater exceeded the 24-hr
primary NAAQS (260 yg/m3). The AT wood heaters (with the exception of
1983 wood heater 4) operated with indoor TSP levels less than 100
yg/m3.
Moschandreas (2) reported finding a 24-hr indoor TSP concentration of
160 ug/m3 in a residence heated by a fireplace, and 24 hr indoor TSP
levels of 281 and 230 ug/m^ for wood stove space heating. During the
1984 TVA study, NAT wood heater 5 (a Franklin-type, freestanding
fireplace) was operated with its front doors open, in a fashion similar to
that of a traditional fireplace. The maximum indoor TSP level found
during those tests was 132 ug/m3 (very similar to that found by
Moschandreas). However, the maximum levels of indoor TSP generated by the
AT wood heaters during the 1983 (except wood heater 4) and 1985 TVA
studies (88 and 93 mg/ra3, respectively) were much lower than those
739
-------
reported by Moachandreas (281 and 230 pg/m^). The findings of
Hoschandreas for AT wood heaters are more similar to indoor TSP levels
found for the 1983 AT wood heater 4 (maximum 24-hr average of
174 pg/ra^) which had a severe leakage problem around the door sealing
area.
Influence of Wood Burn Rate on IAQ
Linear regression analyses of the test data were performed to
determine the relationships between wood burn rate and indoor CO source
strength, flue gas CO concentration, and indoor TSP source strength for
the AT and NAT wood heaters tested using medium moisture (25-percent wet)
oak cordwood fuel. The results of these analyses are presented in
Table II. Flue gas CO concentration data was not available for the 1983
study, and results from catalytic wood heater 2, tested during the 1985
study, are not included since that unit was tested only at low burn rates.
The indoor CO source strength versus wood burn rate relationships for
each of the wood heaters tested during the winters of 1983, 1984, and 1985
are presented in Figure 3. The catalytic AT wood heaters operated with a
definite trend of increasing indoor CO source strengths with increasing
wood burn rates (with the exception of the 1983 study wood heater 2, which
had a poor correlation coefficient of 0.20). This is important in view of
the fact that catalytic wood heaters are designed to operate with reduced
stack, emissions at low burn rates, with less consideration given to
operation at high burn rates. However, both the conventional AT and the
NAT wood heaters operated with the reverse trend of decreasing indoor CO
source strengths with increasing wood burn rates. The AT wood heaters
were found to be more closely related to burn rate alone than the NAT wood
heaters, since the correlation coefficients were generally higher for the
AT units.
A graphical representation of the flue gas CO concentration versus
wood burn rate for the 1984 and 1985 studies is presented in Figure 4.
The same trends for flue gas CO appear as were found for indoor CO source
strengths. These same trends of increasing flue gas CO concentrations
with increasing wood burn rate for catalytic AT wood heaters, and
decreasing flue gas CO concentrations with increasing wood burn rate for
conventional AT wood heaters were also found during the 1982 TVA study
(10) of flue gas emissions from AT wood heaters.
The fact that indoor CO source strength and flue gas CO concentrations
show the same relationship to wood burn rate for each type of wood heater
tested shows that indoor CO source strength is directly influenced by the
concentration of CO in the stack, gases. However, the magnitude of
influence of flue gas CO concentration on indoor CO source strength can be
seen to have differed greatly for AT and NAT wood heaters. The NAT wood
heaters can be seen to have operated with similarly low flue gas CO
concentrations as the AT heaters, but NAT heaters 3 and 4 generated much
higher indoor CO source strengths than did the AT heaters.
A greater insight into the relationship between flue gas gas CO
concentration and indoor CO source strength can be gained from Figure 5.
Flue gas CO concentration versus indoor CO source strength results for box
type and Franklin-type NAT and for AT wood heaters are presented. The NAT
740
-------
wood heaters were found to operate with much higher indoor CO source
strengths while having much lower concentrations of flue gas CO than did
the AT wood heaters. The Franklin-type, freestanding fireplace NAT unit
operated with the lowest flue gas CO concentrations and yet highest indoor
CO source strengths of all the wood heaters tested. The two box-type NAT
wood heaters operated with lower indoor CO source strengths, while having
higher stack CO concentrations than were found for the Franklin-type NAT
unit. The AT wood heaters (both catalytic and conventional) operated with
much higher concentrations of stack gas CO, while representing a smaller
source of indoor CO than either the Franklin- or box-type NAT units. This
paradoxical relationship between stack gas CO concentration and indoor CO
source strength is attributed to both continuous and intermittent
"back-puffing" of stack gases Into the home from the NAT wood heaters.
The indoor TSP source strength versus wood burn rate relationships for the
AT and NAT wood heaters tested during the three T7A studies are presented
in Figure 6. As with CO, NAT wood heaters were found to generate much
higher indoor TSP source strengths than did AT heaters. However, indoor
TSP source strengths generated by the AT and NAT wood heaters did not show
a consistent dependence on wood burn rate. This implies that some other
mechanism was responsible for the liberation of particulate matter into
the indoor environment than that responsible for the liberation of indoor
gaseous pollutants, such as CO. This is also shown by the low correlation
coefficients of the regressed TSP versus burn rate relationships presented
in Table II.
Influence of Wood Moisture Content on IAQ
Specific testing was conducted using catalytic wood heater A (1985) to
determine the effects of the use of variable moisture content red oak and
yellow pine cordwood fuels on indoor air quality. The catalytic wood
heater CO and TSP 3ource strengths were found to be similar for different
wood moisture contents for both low and high burn rate testing. A more
detailed discussion of the wood moisture influences on Indoor air quality
is presented in Reference 10.
References
1. Moschandreas, D. J., J. Zabransky, Jr., and D. J. Pelton, "Comparison
of Indoor-Outdoor Air Quality," Electric Power Research Institute,
EPRI EA-1733 (March 1981).
2. Moschandreas, D. J., D. J. Pelton, and D. R. Berg, "The Effects of
Woodburning on Indoor Pollutant Concentration," Proc, of APCA Annual
Meeting. Philadelphia, Pennsylvania (June 1981).
3. Traynor, G. W., J. R. Allen, and J. F. Koonce, Jr., "Indoor Air
Pollution from Portable Kerosene-Fired Space Heaters, Wood-Burning
Stoves, and Wood-Burning Furnaces," Proc. of APCA Specialty Meeting
on Residential Wood and Coal Combustion. Louisville, Kentucky (March
1982).
A. Traynor, G. W., M. G. Apte, A. R. Carruthers, J. F. Dillworth, D. T.
Grimsrud, and L. A. Gundel, "Indoor Air Pollution Due to Emissions
from Wood-Burning Stoves," Proc. of APCA 77th Annual Meeting. San
Francisco, California (June 198A).
741
-------
5. Knight, C. V. and M. P. Humphreys, "Impacts of Airtight and
Non-airtight Wood Heaters on Indoor Levels of Polynuclear Aromatic
Hydrocarbons in a Weatherized Residential Home," Proc. of Tenth Int.
Sym. on PAH. Battelle Columbus Labs (October 1985).
6. Knight, C. V., M. P. Humphreys, and D. W. Kuberg, "Summary of Three
Tear Study Related to Wood Heater Impacts on Indoor Air Quality,"
Proc. of Int. Conf. on Residential Wood Energy. Reno, Nevada (March
1986).
7. TVA Test Report, "TVA/BPA Indoor Air Quality Study - Phase I,"
Tennessee Valley Authority, Division of Conservation and Energy
Management, Chattanooga, Tennessee (August 1984).
8. TVA Test Report, "TVA/CPSC Indoor Air Quality Study," Tennessee
Valley Authority, Division of Conservation and Energy Management,
Chattanooga, Tennessee, In Press.
9. "Tennessee Valley Authority/Bonneville Power Administration Indoor
Air Quality Study - Phase II," Tennessee Valley Authority, Division
of Conservation and Energy Management, Chattanooga, Tennessee (draft,
1985).
10. TVA Test Report, "Residential Wood Heater Testing, Phase II."
Tennessee Valley Authority, Solar Applications Branch, Chattanooga,
Tennessee (August 1983).
742
-------
TABLE I. COMPARISON OF CARBON MONOXIDE AND TOTAL
SUSPENDED PARTICULATE RESULTS FOR EACH WOOD HEATER
CO TSP
In/ In/ 0
Wood Htr Indoor® Outdoor™ Out SSn Indoor10 Outdoor0 Out SSn ACH
1985 TVA/BPA AIRTIGHT WOOD HEATERS - All 12-hr teats
la Av. 0.9 0.5 1.8 126 58.9 49.4 1.2 7.5 0.6
Max Cone. 1.8 (all 1-hr averages)
2b Av. 1.0 0.4 2.5 99 64.5 54.6 1.2 6.4 0.4
Max Cone. 2.4
3C Av. 0.9 0.6 1.5 55 51.S 44.3 1.2 5.4 0.4
Max Cone. 1.4
4d Av. 1.6 0.4 4.0 182 57.0 42.4 1.3 4.1 0.4
Max Cone. 2.8
5e Av. 0.9 0.4 2.3 69 54.5 43.1 1.3 4.3 0.3
Wax Cone. 1.3
1984 CPSC NON-AIRTIGHT WOOD HEATERS - All 12-hr test3
3f Av. 3.0 0.4 7.5 416 118.7 34.3 3.5 11.9 0.4
Max Cone. 9.6
48 Av. 3.6 0.4 9.0 530 166.0 58.0 2.9 20.6 0.5
Max Cone. 29.6
5h Av. 2.0 0.5 4.0 210 140.7 102.9 1.4 12.7 0.4
Wax Cone, 5.6
1983 TVA/BPA AIRTIGHT WOOD HEATERS - All 24-hr test3
l1 Av. 1.9 0.8 2.4 162 49.9 36.2 1.4 5.0 0.4
Has Cone. 8.0
2J Av. 1.6 1.3 1.2 70 37.1 31.4 1.2 4.2 0.4
Max Cone. 3.3
3k Av. 1.5 0.9 1.7 95 45.8 26.9 1.7 5.7 0.4
Max Cone. 3.9
4J Av. 3.6 0.6 6.0 375 101.0 25.4 4.0 42.9 0.4
Max Cone. 9.1
a,b,c,d,j,l - All catalytic, radiant heaters
e,k - Conventional, radiant heaters
f,h - Box-type, radiant heaters
6 - Franklin-type, freestanding fireplace heater
i - Conventional, circulator heater
in - Indoor/outdoor concentration CO (ppm), TSP (yg/ra3)
n - Source strength (rag/hr)
o - Air changes per hour
743
-------
TABLE II. LINEAR REGRESSION ANALYSIS OF
CO AND TSP SOURCE STRENGTHS AND FLUE GAS
CO CONCENTRATIONS VERSUS WOOD BURN RATE
Wood CO Source Strength Flue Gas CO TSP Source Strength
Heater (mg/hr) (X) (mg/hr)
Number Factor Bias Corr. Factor Bias Corr. Factor Bias Corr.
1983 Study - Catalytic and Conventional Airtight Wood Heaters
1 (Conventional) -65 549 -0.77 - -1.3 13.0 -0.75
2 (Catalytic) -7 97 -0.20 - -
3 (Conventional) -7 153 -0.64 - - - 0.3 2.4 0.64
4 (Catalytic) 17 378 0.33 - - - 1.7 7.5 0.31
1984 Study - Non-Airtight Wood Heaters
3 (Box-type)
4 (Franklin-type)
5 (Box-type)
-116 1478 -0.56
-39 149 -0.14
-29 352 -0.29
0.03 0.78 -0.27
0.004 0.07 0.17
-0.01 0.46 -0.06
-2.0 52.6 -0.20
0.6 54.7 0.05
-0.3 38.9 -0.05
1985 Study - Catalytic and Conventional Airtight Wood Heaters
1 (Catalytic)
3 (Catalytic)
4 (Catalytic)
5 (Conventional)
16 51 0.75
5 41 0.67
18 11? 0.67
-8 102 -0.94
0.06 0.47 0.33
0.04 0.24 0.42
0.28 0.36 0.50
-0.40 2.88 -0.73
-0.01
7.7
-0.51
-0.5
7.1
-0.76
-0.4
5.3
-0.59
1.0
oo
o
0.44
CO Source Strength - (Wood Burn Rate * Factor) * Bias
Corr - Correlation Coefficient
744
-------
4000
9
E
O
z
Ul
(A
tu
o
tc
3
o
<0
o
a
3000-
2000
1000
1983 TVA/BPA
AIRTIGHT WOOD HEATERS
_l
<
<
z
z
O
o
o
o
P
p
K
K
z
>
z
>•
UJ
•1
UJ
_l
>
<
>
<
z
K
z
H
o
<
o
<
o
o
o
O
m—
1084 CPSC
— NON-AIRTIGHT —
WOOD HEATERS
UJ
a.
>-
K
X
O
m gs
_ig
UJ
a
>-
o
a
1066 TVA/BPA
AIRTIGHT WOOD HEATERS
TESTS REPRESENTING
HIGHEST AND LOWEST
INDOOR SOURCE STRENGTHS
GEOMET CO SOURCE
STRENGTHS FOR GAS AND
COOKING APPLIANCES
LOW
160
MEDIUM
300
HIGH
600
>-
_i
<
<
a
>
<
K
<
<
z
o
Ui
>
z
O
u
Figure
2343461 234
WOOD HEATER NUMBER
1. Comparison of Carbon Monoxide (CO) Source Strength Ranges for
Airtight and Non-Airtight Wood Heaters
60-
E
z
K
O
z
UJ
cc
ui
o
s
a
o
0>
&
<0
H
40-
20
k
1983 TVA/BPA
IRTIQHT WOOD HEATERS
if
<
z
O
UJ
>
O
o
<
z
O
>
z
o
u
•I
<
<
o
1884 CPSC
- NON-AIRTIGHT
WOOD HEATERS
<9
Z
o
z
<
K
uj «
w i
cr i
1085 TVA/BPA
AIRTIGHT WOOD HEATERS
UJ
a.
>
O
03
UJ
a.
>
K
x
o
s
TESTS REPRESENTING
HIGHEST AND LOWEST
INDOOR SOURCE STRENGTHS
FOR TSP (mg/hr)
•1
<
z
u
O
o
o
O
h
P
p
>¦
>
>•
>
z
-J
_i
•i
-i
UJ
<
<
<
<
>
H
K
z
<
<
<
<
0
O
O
O
o
o
H
3 4 S 1
WOOD HEATER NUMBER
Figure
2. Comparison of Total Suspended Particulate (TSP) Source Strength Ranges
(mg/hr) for Airtight and Non-Airtight Wood Heaters
745
-------
as
m
6
x
>-
a
z
ui
e
t-
ui
lU
o
ac
3
o
If)
o
o
900
7 60"
aoo
450
300
1 50
NON-AIRTIGHT WH
CATALYTIC AIRTIGHT WH
M CONVENTIONAL AIRTIGHT WH
WH WOOD HEATER
^ — •
1663 WH3
teas «H3
• 1983 WH2
10
WOOD BURN RATE (tb/hr)
Figure 3. Indoor CO Source Strength (mg/hr) versus
Wood Burn Rate (Ib/hr) for Airtight and
Non-Airtight Wood Heaters
NON-AIRTIGHT WH
CATALYTIC AIRTIGHT WH
CONVENTIONAL AIRTIGHT WH
WH WOOD HEATER
WOOD BURN RATE (Ib/hr)
Figure 4. Flue Gas CO Concentration {%) versus
Wood Burn Rate (Ib/hr) for Airtight and
Non-Airtight Wood Heaters
-------
4000i
3000-
O BOX TYPE NON-AIRTIGHT WOOO HEATERS
~ FRANKLIN FREESTANDING NON-AIRTIQHT
WOOD HEATERS
a AIRTIGHT WOOD HEATERS
2000
1000-
0
4
2
3
1
PERCENT FLUE OAS CO
Figure 5. Flue Gas CO (%) versus Indoor CO Source Strength
(mg/hr) for Airtight and Non-Airtight Wood Heaters
NON- AIRTIGHT WH
CATALYTIC AIRTIGHT WH
CONVENTIONAL AIRTIGHT WH
WH WOOO HEATER
60 -t
45
30
T
WOOD BURN RATE (Ib/hr)
Figure 6. Indoor TSP Source Strength (mg/hr)
versus Wood Burn Rate (Ib/hr) for Airtight
and Non-Airtight Wood Heaters
-------
A REFINEMENT OF THE POTASSIUM TRACER
METHOD FOR RESIDENTIAL WOOD SMOKE
James VI. Buchanan,
Shutian Li, and Clifton Calloway, Department of Chemistry
Appalachian State University, Boone, North Carolina
A
The USEPA currently uses potassium as a tracer for the mass of wood smoke
collected on ambient fine particle filters. Total potassium is measured
by XRF analysis, and soil potassium is estimated by assuming a value for
the K/Fe ratio in soil, multiplying by the Fe present and subtracting from
total K analyzed. We suggest a cheaper and more reliable technique
wherein water-soluble K is analyzed by ion chromatography. The assurttption
is that all fine particle smoke potassium (but very little soil potassium)
is water-soluble. Preliminary results indicate this may be the case.
748
-------
A REFINEMENT OF THE POTASSIUM TRACER METHOD
FOR RESIDENTIAL WOOD SMOKE
Introduction
The recent vastly increased use of wood as a residential fuel has
caused concern over the environmental impact of wood smoke, both as a
local pollutant and as a factor in global atmospheric chemistry and energy
balances. Forest fires, as well as controlled burning of large areas for
agricultural use, also deposit very large amounts of fine particles (< 2.5
urn aerodynamic diameter) in the atmosphere. One of the more obvious
effects of large scale wood combustion is visibility degradation (1), In
addition, there is concern about carcinogenic materials volatilized from
so-called air-tight (oxygen deficient) wood-burning stoves (2).
The need exists for development of sampling and analytical methods
related to the characterization of source and ambient wood smoke. In
particular, methods related to determining the contribution of wood
burning to fine particle mass concentrations in the troposphere are
assuming importance in current studies. Such source apportionment methods
include emission inventory, source-dispersion models and receptor models
(3). Emission inventories require detailed knowledge of what emerges from
all sources of pollution in the area studied; source-dispersion models
integrate emission estimates with meteorological and mass transport data
to predict levels of ambient fine particles; and receptor models use
ambient particle loadings and composition along with meteorological data
to estimate the number and types of emitters contributing to local air
shed fine particle concentrations.
Receptor models are considered of great potential value because they
are not dependent on a detailed knowledge of all local sources. As a
result, much recent work has concerned the development of realistic
approaches to receptor-oriented modeling, using chemical and physical
properties of airborne fine particles (A). Stevens (5) has outlined the
currently available sampling and analysis methods for use in
receptor-modeled source apportion- ment studies of the impact of wood
burning on fine particle mass. These methods include use of potassium as
a reasonably unique tracer for the mass of wood smoke in the fine
particles, although the percentage can vary considerably depending on the
type of wood being burned, burn temperature and other factors. For this
reason it is desirable to obtain "source signatures" in the area under
study.
Because potassium on sample filters can also originate from sources
other than wood burning, a correction for this must be made. The
predominant non-wood smoke potassium source is wind-blown soil particles.
In this instance, iron is used as a quantitative indicator of the amount
of crustal material present, and a constant ratio of potassium-to-iron
mass in the soil is assumed. The total potassium found by X-ray
fluorescence is then reduced by the soil-potassium mass.
The problem with this type of correction is that it either makes an
assumption regarding the iron-potassium ratio, or requires analysis of
local soil samples (6).
749
-------
We propose that potassium can indeed be a reliable mass tracer for
wood smoke, but present techniques are not taking advantage of a natural
correction for non-wood origin potassium; namely, its relative water
insolubility.
Wood smoke, being the product of a high-temperature combustion
process, will have its potassium associated with simple anions - chloride,
sulfate, nitrate, and carbonate. All these are highly water-soluble.
Soil potassium will be tied up in complex mineral form - silicates and the
like. These sources are not water-soluble to any appreciable degree.
Thus, a separation technique involving treatment of the filter sample in
aqueous solution should naturally segregate the two forms.
Analysis for wood-smoke potassium is simplified by this separation
technique, since ion chromatography can be used for water-extractable
potassium.
Experimental Methods
All local sampling was done with a cyclone inlet and pneumatic flow
controller. The cyclone inlet, if operated between 22 and 30 liters/min
flow rate (at sea level pressure), will separate aerosol particles into
fine and coarse fractions. The fine fraction cut point is2.5|jm in diameter are deposited
in a "cup" and are not analyzed. Cyclone inlets are described by John and
Reischl (7). Analysis of fine particles only is justified by the fact
that most wood burning emissions are found in the fine fraction, in the
form of nonvolatile organics and elemental (soot) carbon (5).
Teflon filters (1-2 ym pore size) were used, since these are
suitable for both X-ray fluorescence elemental composition analysis and
aqueous extraction. Filters were massed before and after sampling, with a
Fisher Grara-Atic microbalance. Before massing, filters were desiccated
for twenty-four hours over calcium chloride.
Sampled filters were also obtained from the Inorganic Pollutants
Analysis Branch (IPAB) of EPA, Research Triangle Park, N. C. These
filters were obtained from an EPA study done in Missoula, Montana in May
of 1979. Both coarse and fine particle filters from dichotomous samplers
were provided. Filters from other sites will be provided as this study
continues.
Filters were sent to IPAB for X-ray fluorescence (XRF) analysis of
elemental composition, and were then returned to our lab for ion
chromatographic (IC) analysis. As preparation for IC analysis filters
were placed in 30-ml nalgene bottles containing solvent solution (normally
0.0025 Molar HCl), and agitated for twenty minutes in an ultrasonic bath.
This procedure is described in detail by Stevens, et. al. (8).
750
-------
Ion chromatographic analysis of aqueous extractable potassium was done
on a student-constructed instrument, using a Dionex CS-1 analytical cation
column and CSC 2 packed bed suppressor column. A Shimatzu Model C-R3A
integrator-recorder was used to quantitate the analytical data.
Concentration standards were injected before and after a run of filter
sample solutions. A preliminary analysis was made to indicate the
appropriate dilution standards. Potassium concentrations as low as 0.01
ppm were measurable, but the precision and accuracy were limited by large
ratios of ammonium to potassium, when the K+ peak sometimes appeared
only as a shoulder on the large NH^+ peak. The suppressor column was
regenerated with 0.5M NaOH.
Chimney Sampling
The cyclone was clamped on a ring stand base and set on the chimney
rim. All sampled chimneys had concrete slabs on top so smoke was directed
sideways into the cyclone. Flow rate was maintained at 23 ±2
liters/minute and sampling times were from 5 to 15 minutes. Mass of
collected smoke was usually several milligrams.
Soil Sampling
A soil agitator was constructed as shown in Figure 1. A large
sintered filter funnel formed the soil container, and air was pumped up
through the sintered filter to form a fluidized bed of soil particles.
The funnel was attached by a clamp to the pump assembly, so that the
funnel was shaken mechanically while the sampling was taking place. The
cyclone was held in place 3-5 cm above the soil surface.
All soil samples were screened with a wire sieve having rectangular
openings of about 1 ram, before being placed in the agitator.
When available, oiled teflon filters were used for soil sampling and
sample masses were typically 1-2 mg.
Ambient Sampling
The cyclone was suspended 1-2 meters above the ground. Sampling times
were either twelve or twenty-four hours at 23 ±2 liters/minute. Sample
masses were normally a few milligrams.
Results and Discussion
Figure 2 is a plot of EPA XRF potassium, corrected for windblown soil,
versus our extracted potassium by IC- These data were obtained from a
tray of fine-particle filters provided by EPA-IPAB, from a study in 1979
in Missoula, Montana.
The correction for windblown soil was made by using a K/Fe mass ratio
of .53 + 0.24, obtained as the mean of this ratio for 20 coarse particle
filters, also provided by EPA from the same study. The Fe mass on each
filter was multiplied by this ratio, and the result was subtracted from
total filter K. This is the correction suggested by Lewis & Einfeld (6).
751
-------
The slope of the best-fit straight line is 1,05 ± 0.D9 and the
intercept is -255 ng ± 100 ng. Total number of filters analyzed was 20.
The independent variable was the 1C value, and a +10% uncertainty was
assigned to the XRF data. A similar plot of IC versus XRF data, with
uncertainties of ±10-20% on the IC data, yields a slope of 0.92 t 0.09 and
an intercept of 174 ng + 142 ng.
Conclusion
Our data are limited and should be considered preliminary. We are
continuing to process filters from other EPA studies and from the Boone,
North Carolina, area. In addition, we are submitting both soil and smoke
fine particle filters to EPA for XRF analysis. Results should indicate
solubility of soil K and the efficiency of water extraction of all K. from
smoke fine particles. This data will be presented at the Minneapolis
meeting in June.
Acknowledgments
The idea for this project came from R. K. Stevens, Chief of IPAB,
ESRL, USEPA, Research Triangle Park, North Carolina. Thanks also to Tom
Dzubay and Charles Lewis of IPAB for their advice, and to Tom Dzubay for
the XRF work.
References
1. EPA-450/5-79-008 (1979), "Protecting Visibility: An EPA Report to
Congress," I!. S. Environmental Protection Agency Report.
2. Cooper, J. A. and Malek, D., editors (1981), Residential Solid Fuels:
Environmental Impacts and Solutions, proceedings of an international
conference sponsored by the Oregon Graduate Center, Beaverton, Oregon.
3. Cooper, J. A. (1981), "Chemical and Physical Methods of Apportioning
the Contributions of Emissions from Residential Solid Fuels to
Reductions in Air Quality," in Residential Solid Fuels: Environmental
Impacts and Solutions, edited by Cooper, J. A. and Malek, D., 349.
4. Dattner, S. L. and Hopke, P. K., editors (1981), Receptor Models
Applied to Contemporary Pollution Problems, proceedings of an Air
Pollution Control Association Specialty Conference, Danvers,
Massachusetts.
5. Stevens, R. K. (1985), "Sampling and Analysis Methods for Use in
Source Apportionment Studies to Determine Impact of Wood Burning on
Fine Particle Mass," Environment International (in press).
6. Lewis, C. VI. and Einfeld, W. (1985), "Origins of Carbonaceous Aerosol
in Denver and Albuquerq-e During Winter," Environment International
(in press).
7. John, W. and Reischl, Georg (1980), "A Cyclone for Size-Selective
Sampling of Ambient Air," J. Air Poll. Cont. Assoc. 30, 872.
8. Stevens, R. K. , Dzubay, T. G., Russwurm, G. M. and Rickel, D. (1978),
"Sampling and Analysis of Atmospheric Sulfate and Related Species,"
Atmospheric Environment 12, 55.
752
-------
Suction Pump
Cyclonic Sampling
Head —— .
Soil Sample
•///>> >JJJ?/;y/yS?J7J7755?
Funnel
Clamp
(to p u rn p
for a g i K a t i o n)
Compressed Air
Glass W o o J
Filter
Figure 1- Schematic for soil aerosolizer
753
-------
8000-
7000
s>o o o
e 3000
2 0 0 0
1000 2000
n g K ' , 1 C
Corrected xnr potassium versus extracted 00) polassium
4 0 0 0
sooo
6000
Figure
754
-------
TOXIC AIK POLL UIAN 1 EMISSION MEASUREMENT
TECHNIQUES FOR NON-STEA0Y-STATE PROCESSES:
A CASE STUDY WITH ETHYLENE OXIDE
Pankaj R. D e s a i , P.E.
Anthony J. Buonicore, P.E.
Chemrox, Inc.
Bridgeport, Connecticut
Measurement techniques are well-established for mo
air pollutant emissions from sources operating und
steady-state conditions. However, such is not the
non-steady-state processes, as frequently encounte
toxic air pollutant emission situations. This pap
the measurement technique developed for one such s
i.e., ethylene oxide emissions from gas sterilizer
the medical device industry.
Either pure ethylene oxide or an admixture with an
diluent is typically used in gas sterilizers to treat medical
products which cannot withstand heat sterilization. At the
end of sterilization, ethylene oxide is exhausted to the
atmosphere in a series of intermittent sterilizer
evacuations. The operating conditions used during this
exhaust cycle result in a highly dynamic condition in the
stack. All critical process parameters affecting stack
emission measurements vary instantaneously and simultaneously
during the entire exhaust cycle. To accurately determine the
total weight of ethylene oxide discharged to the atmosphere,
it is necessary to monitor all relevant parameters
continuously throughout the cycle. Also, all measurements
must be made without exposing operators to toxic ethylene
oxide.
An accurate measurement of air pollutant emissions from
sources operating under non-steady-state conditions requires
the use of properly designed orifice meters for gas flow
measurements, thermometers with remote sensors for
temperature measurements and on-line gas chromatographs for
determining exhaust gas composition. This paper discusses a
step-by-step measurement technique, including calcuiational
procedures, developed to determine ethylene oxide emissions
from sterilizers.
st types of
e r
case with
red in many
er reviews
ituation,
s used in
inert
755
-------
TOXIC AIR POLLUTANT EMISSION MEASUREMENT TECHNIQUES
FOR NON-STEADY-STATE PROCESSES: A CASE
STUDY WITH ETHYLENE OXI DE
Introduction
E i C h e r
pur
a
ethylene oxide (EtO) or an admixture with
a n
inert gas i
s
u s
e
d in sterilization chambers to treat medica
1
products wh
L
c h
c
annot withstand heat sterilization. Figur
e
I
presents a
t
ypi
c
al sterilization cycle using pure EtO. At
t
h e
end of star
i
1 i z
a
tion, EtO is exhausted to the atmosphere.
Typically a
see
r
ilLzer exhaust cycle includes a series of
pressure pu
1
ses
.
Each pressure pulse consists of chamber
evacuat ion
*¦
o a
predetermined vacuum followed by introduce
ion
of air into
t h e
chamber to bring the chamber up to
atmospheric
pre
s
sure. A water-ring vacuum pump is general 1
y
usid to eva
c
u a c
e
the chamber and each evacuation represent
s
an intermit
b
X.
ent
EtO discharge to the atmosphere.
A w a t e
r
- r i
n
g vacuum pump is a positive di solacement
pump. The
P
res
s
ure on the inlet side of the pur,ip decrease
s
cont inuousl
y
a s
the chamber is evacuated. However, the
pressure on
the
discharge side of Che pump remains virtual
y
constant (a
c
ne
a
rly one acmosphere). The total gas flowra
l
e
(3CKM) on the discharge side of Che pump, Che re tore,
decreases as Che chamber pressure is reduced. Furthermore,
the sterilizer gas containing EtO is thoroughly mixed with
the seal uater in the pump. Due to Che relatively high
soiub
i
I i t y of E
CO
in wa t
e
r j soTne
o f
the EtO
evacuated
from
t h e c
h
amber is
a b s
orbed
i
n the s e
a I
water.
The e x t e n
t of
EtO
absor
P
tion vari
e s
depend
i
ng upon
s e
a
1 water
temperatu
re an
d
total
gas flowr
ate
. Thus
i
all c t i
t i
c
a I proce
s s p a r a nwi
t e r s
at fee
t-
i.
ing emiss
ion
me a s u
r
iitnenc s -
t
~
c a 1 e x h a
u s c gas f
lowra
te ,
EcO concentration in the exhaust gas and overall gas
composition - change continuously throughout a given
evacuation. This creates a highly dynamic condition in the
exhaust stack.
Measurer:
len
t Te
c h
r. i q u e
A n
a c
cura
t e
measu
rement of
toe
a 1 weight
0
£
EtO
emissions
£ r oin a <
> t e
rili
z e
r requ
ires mon i
tori
ng of the
£
o 1
lOWL
ng
process
pa
r am e
C e
r s con
cinuously
o v e
r the e n t i
. r
e
e xh a
u s t
cycle :
• Gas temperature
• Gas static pressure
756
-------
• Total volume trie gas flowrate
• Ethylene oxide concentration
• Inert gas concentration (if applicable)
The se measurements must be made without exposing operators to
toxic ethylene oxide.
Gas temperature and pressure are required to make
appropriate corrections to measured volumetric gas flowrates.
Gas temperature is measured by a thermometer with a remote
sensor located in the stack. Thermocouple wires can
conveniently be used for this purpose. A pressure gage,
located far from the sampling point, is used for static
pressure measurements. Plastic tubing connected to a
permanent fitting in the stack can be used for pressure
transmission. Temperature and pressure readings should be
taken approximately once every minute.
Since the total gas flowrate changes continuously, it is
necessary to have the means to monitor flowrate on a
continuous basis throughout each evacuation. To accomplish
this safely, accurately and inexpensively, it is necessary
to install a calibrated orifice meter in the exhaust gas
line. Gas pressure drop across the orifice plate should be
recorded once every minute. Due to the extremely wide range
of stack gas flowrate encountered over the exhaust cycle, it
is often necessary to use multiple orifice plates to cover
the entire flow range.
EtO concentration is measured using an on-line gas
chromatograph (GC). The GC must be standardized prior to and
following each test series. Heated gas sampling lines must be
used to prevent condensation of water vapor and EtO, Extreme
care should be exercised in selecting a proper GC column and
a proper detector. For example, Chromosorb lul or Porapak R
can be used for satisfactory EtO separation. Also, a flame
ionization detector should be used for low EtO concentrations
(less than 5% by volume), while a thermal conductivity
detector for high concentrations (5X by volume or higher).
Again, measurements should be made as frequently as the GC
a 1 lows.
In order to calculate the instantaneous volumetric gas
flowrate (of the gas stream being sampled) from the orifice
pressure drop data and the orifice equations, it is necessary
to know the instantaneous gas molecular weight. Therefore,
if an inert gas is used in the process, its concentration
must also be monitored continuously by an on-line GC.
757
-------
Data Evaluation
As discussed previously, the exhaust cycle includes
multiple chamber evacuations. To determine overall EtO
emissions for tlie entire cycle, the total weight of ethylene
oxide exhausted during each evacuation must be determined.
This is accomplished as follows:
1. Determine ethylene oxide concentration at each
measured point from GC data. This is done by
comparing the peak height of each sample with that
of a known, certified (NBS traceable) EtO standard.
2. Determine inert gas concentration at each measured
point based on GC data as in i.
3. Plot a graph of EtO concentration vs. elapsed time
and a graph of inert gas concentration vs. elapsed
time.
4. Determine average molecular weight o£ the gas at
points along the evacuation from the graphs plotted
in 3. and assuming that the exhaust gas is saturated
with water.
5. Calculate total volumetric gas flowrate (SCFM) at
each measured point - based on orifice pressure
drop, average gas molecular weight, gas temperature
and gas pressure - using orifice equations (refer to
T a b I e I ) .
6. Plot a graph of total volumetric gas flowrate vs.
elapsed time.
7. Select a number of points at equal time intervals
along the evacuation for further calculations.
8 .
At each point selected
in 7 .
, calc
u lace E t
0 nass
flowrate by combining
total
volume
trie gas
flowrate
and EtO concentration
at t h a
t p o i n
C using
Che
following equation:
Q Cy/106) (?)
whe re
m —
mass
m
r—'
o
w
rate o
C
E t:
0 , Lb /
min
Q =
t o t a
I vo
L
ijrae t r i
C
ga
s f I o w r
s te
y x
EtO
cone
,>
ntrati
o n
*
p pmv
e =
dens
i t y
0
f £ t 0
=
0.11
6 I b
/
c u . f t .
a
c
standar
d
c o n d
i t i o
n
s ( 60 0
^ >
I
a t in . )
758
-------
9 . Generate a curve of EtO mass flowrate vs. time.
10. Integrate the c
total we i gh t of
over the evacua
urve generated in
EtO exhausted to
t ion.
9. to determine the
the a tmo sphere
The total weight of EtO Emissions over the entire
exhaust cycle is calculated by adding the weights determined
for individual evacuations.
Example
Simplified ca Icu1 ationa I procedures for an example
evacuation are presented in this section. Consider an
evacuation with a total duration of 10 minutes. Steps 1.
through 6. described in the previous section are relatively
straight forward and will produce the graphs of total
volumetric gas flowrate vs. elapsed time and StO
concentration vs. elapsed time. Table II presents the. values
of gas flowrate and EtO concentration from these graphs, for
ten different points over the evacuation. Each point
represents the midpoint of a specific time interval and the
valves of gas flowrate and EtO concentration at each point
are assumed to be the average valves for the corresponding
time interval. Table III presents in — depth calculations.
759
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TABLE 1
ORIFICE EQUATIONS TO CALCULATE VOLUMETRIC GAS FLOWRATES
Q - c' \f (hw) (pf)
where Q = volumetric gas flowrate, SCFM (60°F, 1 atm.)
/
C = flow coefficient multiplier
h ^ = pressure drop across orifice, in. WC
p^ = flow pressure, psia
The flow coefficient multiplier is given by
C = K d2 F ( \/ 520/T) ( \7 2 9/MW)
o *
where K = flow coefficient
o
d = orifice diameter
F " gas compressibility factor ratio
T = gas temperature, °R
MW = gas molecular weight
The values of K and d are constant for a given orifice plate
and are obtained from the orifice plate manutacturer. The
value of F depends upon gas composition. The F value for a
gas mixture can be calculated f £ o ra F values of individual
components. For example, at 60 F and 1 atmosphere, F equals
1.0 for air and 1.5 for an inert gas often used in the
sterilization process. Then, for a mixture of 50% by volume
of air and 50% by volume of this inert gas,
F = (0.5) (1.0) + (0.5) (1.5)
= 1.25
760
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TABLE II
TEST DATA AT SELECTED POINTS
Total Evacuation Time * 10 Minutes
~ ic fr
Total Gas EtO
Point Elapsed Time Flowrate, Concen,
No. mi n, SCFM E£S!^
1 0.5 350 165,500
2 1.5 350 163,000
3 2.5 300 160,200
4 3.5 260 160,100
5 4.5 220 157,700
6 5 . 5 180 157 , 500
7 6.5 140 1 56 , 100
8 7.5 100 155,600
9 8.5 70 155,200
10 9.5 50 155,100
*
From the graph of total gas flowrate vs. elapsed time
VC ,
From the graph ot t to concentration vs. elapsed time
761
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TABLE III
CALCULATIONS TO DETERMINE TOTAL EtO EXHAUST
T iit E c 0
InCccvil , Elapsed Time, FlctfraCe, Cancan.,
Ac. pin. nin. SCFM ppmv
0-1 0.5 350 165,500
1-2 1.5 350 163,000
2-3 2.5 300 160,200
3-4 J.5 260 160,100
4-5 4.5 220 157,700
5-6 5.5 180 157,500
6-7 6.5 140 156,100
7-8 7.5 100 155,600
8-9 8.5 70 155,200
9-10 9.5 50 155,100
Total
EcO discharged during cime interval
- (Q) (y /106) CO. 116 Ib/SCf EtO) < Ac
where Q ¦ g«s f\ curate, SCFM
y " EcO concentracion, ppav
At ¦ length a f tine interval, «m.
EtO
Di scharged
During At,
l_b_
6. 72
6.62
5 .58
U . 83
k . 03
3.29
2 .
1.01
1 - 26
0_^90
37 . 58
762
-------
FIGURE 1
TYPICAL ETHYLENE OXIDE STERILIZATION CYCLE
30
Initial Evacuation
Chamber
Evacuation
Gas Inject ion
Exhaus t
Cycle
Hunvidif ication
and Hold
Time
763
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A UNIVERSAL SAMPLE INTRODUCTION SYSTEM
SUITABLE FOR VOC ANALYSIS IN AMBIENT
AIR, VOST, WATER, AND SOLID SAMPLES
Thomas J. Wagner,
Timothy I. Sander
PEI Associates, Inc.
Cincinnati, Ohio
Both ambient air and stationary source emission methods use Tenax and/or
carbon to determine volatile organic compounds (VOC). Two distinct sample
introduction systems are used: cryogenic trapping for ambient air methods
and a purgc-and-trap apparatus with the volatile organic sampling train
(VOST) protocol. The VOST is the principal stationary source method. This
paper will discuss the application of a single thermal desorption/purge-
and-trap apparatus to the analysis of ambient air, VOST, water, and soil
samples. This sample introduction system eliminates the necessity of major
equipment alterations and the accompanying instrument downtime incurred when
VOC analysis is performed on samples from these various media.
In our work, identical traps containing Tenax or Tenax and charcoal have
been used for both ambient air sampling and VOST sampling. Sorbent trap
preparation, conditioning, and blank checking procedures are identical.
Procedures developed for testing the applicability of both the solid sorbent
and the analytical system to the sampling and analysis of individual com-
pounds are described.
The sample introduction system has been used for a wide variety of projects,
including the validation study of the VOST protocol and an ambient toxic air
monitoring program around a chemical plant. An automated version of this
system has been developed that permits unattended sequential analysis of 10
samples.
764
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A UNIVERSAL SAMPLE INTRODUCTION SYSTEM SUITABLE FOR VOC ANALYSIS IN AMBIENT
AIR, VOST, WATER, AND SOLID SAMPLES
Introduction
Analytical service laboratories have a need to efficiently maximize the use
of expensive, sophisticated instrumentation and highly trained personnel.
Toward this end, we have developed a way of using a common sample introduc-
tion system for gas chromatography/mass spectrometry (GC/MS) analysis of
volatile organic compounds (VOC) in a wide variety of sample matrices. This
approach is a versatile compromise in methodology that was developed over a
period of several years.
The use of solid sorbents to collect VOC's from ambient air or workplace air
is a well established technique. Most of the original applications gere f°r
one or a very limited number of components. Since 1976,''4 Tenax-GC has
been used to collect and analyze multiple compounds from ambient air. The
analytical procedure consists of thermal desorption of sampling traps fol-
lowed by cryogenic trapping of the VOC's and then capillary GC/MS analysis.
This technique has been applied to monitoring ambient air in many situations
such as in national parks, at hazardous waste sites, and even basements of
hemes in the Love Canal area. Current interest in toxic VOC monitoring in
ambient air and at Superfund sites ensures that a substantial amount of work
will continue in this area.
For analysis of ambient air samples, cryogenic trapping after thermal de-
sorption was found to be susceptible to problems during analyses of samples
containing high-moisture levels. When desorbed, moisture could freeze as a
solid ice plug at the head of the subambient-cooled capillary column, stop-
ping carrier flow. A sufficient volume of water also triggers a vacuum
system shutdown in the mass spectrometer. Both of these occurrences result
in instrument problems and the loss of irreplaceable samples.
In July 1982, U.S. EPA received a draft report5 on a volatile organic samp-
ling train (VOST) utilizing Tenax-GC and charcoal solid sorbents. VOST is
one of the most common methods used for sampling and analysis to determine
destruction and removal efficiency during trial burns at hazardous waste
incinerators. The procedure includes thermal desorption of the sample
followed by purge-and-trap/thermal desorption introduction to the GC/MS.
The problem of very high moisture levels in the stationary source gas was
overcome through the use of the water in the purge vessel of the purge and
trap concentrator used in EPA Method 62^6 as a means of condensing out
excess moisture from the desorbed sample prior to trapping. Because the
remaining moisture would still freeze in a subambient capillary column, the
analysis was performed on packed columns.
Since that time, the ambient air Tenax Method T01,7 the carbon molecular
sieve Method T02,7 and a method for field validation of ambient air sampling
using solid sorbents8 have been published. The VOST protocol has been
validated in laboratory and field studies" These methods have much in
common, yet enough differences that a laboratory performing analyses for VOC
in ambient air, stack gas, water, soil, and sludge samples experiences
significant and costly downtime when altering its instrument configuration
from one method to another, even though the analysis is for the same type of
compounds. The Hazardous Substance List (HSL) contains 35 VOC's that can be
determined in water and soil. Method 624 lists 31 VOC's, of which A are not
on the HSL. The common chlorinated and aromatic solvents on these lists are
765
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also of interest in trial burns at hazardous waste incinerators for RCRA
permitting and in ambient air.
The five VOC methods listed in Table I have been validated for use in deter-
mining the indicated compounds. Method 5030/8240,^ as applied in the
Contract Laboratory Program of the U.S. EPA, is applicable without addi-
tional validation to 35 of the 49 compounds listed. This is more than any
of the other methods. VOST has been formally validated for 5 of the com-
pounds. Many of the compounds listed in Table I are also listed in Appendix
VIII of 40 CFR Part 61, and are therefore candidate compounds for VOST
application during trial burns at hazardous waste incinerators. All five
methods may be applicable to additional compounds, but this applicability
must be demonstrated. Acceptable laboratory validation procedures for the
application of these methods to additional compounds are not contained in
the methods.
Over the past 8 years we have performed VOC analyses on thousands of water
samples, hundreds of soil samples, approximately 1500 Tenax samples using
cryogenic trapping, and another 1000 Tenax samples using a purge and trap
apparatus. The majority (90 percent or more) of the Tenax work required the
quantitative determination of 10 or fewer VOC's. The compounds varied for
each project, but generally only a limited number were detected in any
sample at levels greater than 50 ng. In this analytical situation, the
additional resolving power of capillary column chromatography is not needed.
The packed column technology combined with mass spectrometry is powerful
enough for unequivocal results.
The methods used for analysis of Tenax or other solid sorbent samples,
whether obtained from ambient air or stationary sources, have many common
characteristics. The design and assembly of the sampling traps for ambient7
and stationary sources*2 are compatible. Both require similar thermal
conditioning and blank checking prior to sampling; both are applied to
similar compounds; both are subject to similar sampling problems, various
moisture levels, and breakthrough; and both require validation procedures to
demonstrate applicability to specific circumstances.
Table II shows the similarities in the methods of sample introduction and
analysis for the four sample types under discussion. A unified sample
introduction system is highly desirable considering the similar methods and
equipment and boiling point ranges of Cheir target compounds relative to VOC
sampling in ambient air, stationary sources, water, and soil. Such a system
would permit the introduction of ambient air and stationary source solid-
sorbent samples by thermal desorption, and water and soil samples by purge
and trap into a GC/MS without major hardware changes. This would minimize
instrument downtime and improve a laboratory's cost-effectiveness to its
clients.
The methods used for the last three sample types in Table II have much in
common. In the interest of laboratory efficiency and versatility, we have
applied the general form of these methods to the analysis of ambient air
samples, utilizing the same instrument hardware configuration as the VOST
method.12
Analytical Equipment and Experimental Procedures
Sorbent Trap Preparation
Tenax-TA (or Tenax-TA and petroleum-based charcoal) is packed into clean
glass traps (Figure 1) and thermally desorbed with a purge flow of approxi-
mately 40 ml/min purified nitrogen at a temperature of 240°C for 20 hours.
766
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This conditioning is performed using a specially designed manifold/oven with
a capacity for 38 individual traps. Extreme care must be used in the appli-
cation of complex and detailed handling procedures12 in order to produce
traps containing less than 5 ng of any individual VOC.
Blank Check Procedures
Every sorbent trap or trap pair is blank checked prior to use for sampling.
The apparatus used to perform blank checking (Figure 2) consists of a ther-
mal desorption unit ("clamshell oven" - Supelco #2-3800) operated at 190°C
with nitrogen-purge gas flowing at AO ml/min to a Tekmar Model LSC-2 sample
concentrator, bypassing the water-purge vessel. This system is interfaced
to a temperature-programmable gas chromatograph with flame ionization detec-
tor. The sample introduction system, the GC column, and temperature program
are identical to that employed for GC/MS analysis. External standards
prepared from neat liquids in static gas bottles and loaded onto sorbent
traps by use of the flash vaporization apparatus shown in Figure 3 are used
for quantitation. Conditioned traps have been routinely produced with no
greater than 5 ng of any volatile compound present.
GC/MS Analysis
The analytical procedures followed are generally those described in Methods
624 or 5030/82406 '11 plus additional steps for desorption of Tenax and
Tenax/charcoal sorbent traps. A schematic diagram of the sorbent trap
desorption and purge and trap apparatus is shown in Figure 2. Internal
standards are added to traps with a purge flow in the same direction as the
sampling flow direction. Traps are thermally desorbed with a gas flow in
the reverse direction from the sampling flow. Sorbent traps are spiked with
an internal standard by use of a flash vaporization device (Figure 3) and
thermally desorbed for 10 minutes at 180° to 200°C with 40 ml/min organic-
free helium gas. For moisture-laden samples, the effluent is passed through
5 ml of organic-free water in the purge vessel; for dry samples, it bypasses
the water purger and VOC's are collected on an analytical sorbent trap.
After the 10-minute desorption, the analytical sorbent trap is rapidly
heated to 180° to 200DC (dependent on target compound volatilities) with the
gas flow reversed so that the effluent flow from the analytical trap is
directed into the GC/MS. The VOC's are separated by packed-column tempera-
ture-programmed gas chromatography and detected by electron-impact low-reso-
lution mass spectrometry. The mass of each VOC is calculated by the in-
ternal standard method.
The thermal desorption unit is a modified Supelco high-capacity gas purifier
oven ("clamshell oven"). An Omega solid-state digital-temperature control-
ler (Model 300) with thermocouple monitors and controls the desorber oven
temperature. This unit can accept trap configurations from l/16-in.-0D to
5/8-in.-OD and up to 10-in. long.
The purge and trap unit is a Tekmar Model LSC-2, on which all Teflon trans-
fer lines are replaced with l/16-in.-0D stainless-steel tubing to avoid
contamination and/or losses. The transfer lines are wrapped with heat tape
to avoid losses. The internal volume of the glass purge vessel is approxi-
mately 15 ml, and it contains 5 ml of organic-free water (if appropriate).
This vessel is bypassed for dry ambient air samples. For water samples, the
thermal desorption unit is bypassed, and the sample is added directly to the
purge vessel. For soil samples, a differently designed, larger purge vessel
is substituted and the soil and blank water are added to this vessel.
Again, the thermal desorption unit is bypassed.
767
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The internal analytical trap consists of a 15-cm Bection of Tenax, a 3.7-cm
section of charcoal, and a 3.7-cm section of silica gel (Tekmar part L4-
0124-003). The LSC-2 unit is a commercially available device designed to
meet the requirements of Method 624.6
The GC/MS consists of a temperature-programmable packed-column gas chromato-
graph Interfaced with an all-glass jet separator to a quadrupole mass spec-
trometer. All system controls and data acquisition are performed through a
minicomputer-based data system. Samples are transferred from the introduc-
tion apparatus to the GC via heated 1/16-in. tubing connected to the stand-
ard injection port gas supply line. The septum-plugged injection port is
used to perform on-column injections by syringe for recovery and tune checks.
The apparatus shown in Figure 3 is used to load standard solutions onto
sorbent traps. It consists of a glass evaporation chamber with a septum-
plugged side arm for standard injection. The chamber is heated to about
150°C with heat tape and is connected to the sorbent traps with a 1/4-in.
stainless-steel union and Supeltex M-l ferrules. Carrier flow is set at 100
ml/min so that the chamber volume (about 25 ml) is well swept in a 1-minute
loading interval.
Autosampler
We collaborated with the Tekmar Company to redesign the Tekmar Model 4200
Automated Dynamic Headspace Concentrator to configure it to function as an
automated version of the "clamshell oven" purge and trap sample introduction
system. The new instrument, Model 4210 Automatic Desorber, is capable of
sequentially desorbing 10 solid sorbent traps or trap pairs with the design
shown in Figure L. Each sample is thermally desorbed with an individually
controlled heater and the effluent gas passes through a water-purge vessel
(for VOST or moist ambient samples) unique to that sample. There is thus no
possibility of carryover of sample components in the water purge vessel from
sample to sample. A schematic of this instrument is shown in Figure 4.
This unit will accept the same range of trap configurations as the "clam-
shell oven."
System Modifications for Various Media
The sample introduction system described can easily, with the following few
minor modifications, be used for the analysis of VOC's in stationary source
(VOST), ambient air, water, and soil samples. The water-purge vessel is
removed fTom the flow stream for analysis of ambient air samples of low-
moisture content. When water or soil samples are analyzed, a tubing union
replaces the sorbent traps in the purge gas flow line. Soil samples require
the use of a purge vessel with a different design (as per Method 5030) than
is employed for other analyses.
Results
General Applicability
The sample introduction system described here has been applied in this
laboratory to the analysis of ambient air samples collected on a variety of
Tenax traps for the entire Hazardous Substance List (HSL) of volatile or-
ganic compounds. We have performed a limited recovery test for a methanolic
standard of the entire HSL volatiles loaded onto a Tenax and Tenax/charcoal
trap pair and thermally desorbed through a water purge vessel compared with
an on-column injection of the same standard. Because the response of the
three earliest eluting target compounds in the on-column injection was badly
768
-------
suppressed by coelution with the solvent, their results were discarded.
Table 111 presents recovery values for the remaining 32 targets, 3 sur-
rogates, and 3 internal standards (38 compounds).
The four compounds that fell into the 25 to 50 percent recovery range were
all water-soluble ketones which almost certainly would be recovered quanti-
tatively if the water-purge vessel were removed from the flow path from the
desorber. That leaves only one compound that fell outside the 70 to 130
percent recovery range. This demonstrates the broad range of applicability
of this sample introduction technique.
Method Validation
Because of the wide variety of VOC's, the various procedures must be vali-
dated for a specific application. As shown in Table I, each method has been
validated and is recommended for different compounds and many additional
compounds have been requested for specific applications. The VOST has been
validated for trichlorofluoromethane, chloroform, carbon tetrachloride,
benzene, and perchloroethylene.1" Method i>2k has been validated for 31
compounds. The U.S. EPA's Contract Laboratory Program has compiled a huge
database for the application of Methods 5030/8240 to water, soils, and
sludges for the analysis of the 35 HSL VOC's. The range of compounds deter-
mined by the VOST can probably be extended closer to the high boiling point
limit of Method T01, considering that the first trap in the VOST is almost
identical to the Tenax trap of T01. If a second Tenax/charcoal trap (as in
VOST) is added in series with the present Tenax trap of Method TOl, the
range of compounds to which Method TOl could be applied would probably match
the low boiling point limit of the VOST. No appreciable cost increase would
occur if these traps were analyzed as a pair. Application of modified
methods such as we describe here or use of existing methods to determine
compounds for which the method has not been validated demands that a cost-
effective approach be developed for laboratory method validation.
A method of validating solid sorbent analysis using the sample introduction
system described here was developed during the VOST validation studies. To
test the sample introduction system, a standard is prepared containing the
compounds of interest. This may be a static bottle gas standard or a meth-
anolic solution. For early eluting compounds, a gas standard is preferred
because a large quantity of methanol in the analytical system suppresses the
response of compounds with which it coelutes. The standard is injected
on-column as a 100 percent recovery calibration point. This standard is
then loaded onto a sorbent trap or trap pair using a flash vaporization
device.13 The sorbent trap(s) is then analyzed to determine recovery
through the sample introduction apparatus. For water or soil samples, the
standard is added directly to the purge vessel. The absolute area response
and the internal standard (I.S.) corrected response are both compared.
During the VOST validation of five compounds, this laboratory obtained
absolute area recoveries of between 78 and 109 percent and 1.S.-corrected
recoveries between 89 and 110 percent on nine separate weekly system checks.
This on-column recovery test demonstrates that the sample introduction
system is leak free and capable of delivering the sample to the analytical
system without loss and that suitable calibration standards can be prepared
on sorbent traps.
For ambient air and VOST samples, the effectiveness of a given sorbent(s)
and trap design in collecting and thermally desorbing desired compounds must
also be validated. Distributed air volume sampling can be employed for
field validation of ambient samples, but is impractical for VOST and may be
expensive for ambient air if it invalidates a series of samples from a dis-
769
-------
tant site, forcing replication of the test. The following procedure is
proposed for preliminary laboratory validation of the sampling and analysis
approach prior to field application.
After the sample introduction system has been checked for recovery by use of
the above procedure, a series of five trap samples are prepared. These may
be single-sorbent traps or paired-sorbent traps in series (e.g., VOST). The
standard used for the on-column check is loaded on the trap(s) and either 0,
5, 10, 15, or 20 liters (or other volumes suitable to the proposed sampling
situation) of air or nitrogen is passed through each trap or trap pair. The
entire amount of standard is loaded before any of the measured gas volume
passes through the test sample. The measured volume may be dry gas or
saturated with moisture depending on whether the application being tested is
ambient air or stack gas. The temperature should be constant and known. A
flow rate of 0.5 liter/min is convenient for preparing test samples during a
concurrent GC/MS run. This constitutes a "worst-case" evaluation since the
entire amount of the desired compounds is subjected to the total gas volume
rather than as in a real sample where compounds are loaded continuously over
the entire sampling volume. The internal standard is added as it would be
to a real sample.
The test samples are analyzed and the internal standard corrected recovery
for each component is calculated based on the zero gas volume trap being
assigned 100 percent recovery. The average recovery for each 5-liter inter-
val is determined (0-5, 5-10, 10-15, and 15-20). The mean of these four
values is used to approximate the average recovery for a 20-liter sample.
Table IV shows the results of applying a procedure, similar to the one
proposed, to four compounds of interest at an actual industrial site.
Compounds C and D gave excellent recovery on all samples. This was antici-
pated because compound C has been determined on Tenax traps previously and
compound D is similar to C and within the recommended ranges of Method T01
(80° to 200°C). Compounds A and B have boiling points less than 80°C but
are within the recommended VOST range of 25" to 125°C. The recoveries show
that neither compound A nor B is retained on Tenax for any appreciable
sample volume at a flow of 0.5 liter/min; however, the recoveries on the
Tenax-Tenax/charcoal trap pairs is significantly improved. Considering that
this pair of traps represents only a 60 percent increase in the amount of
Tenax used for collection, the majority of the improvement in recovery is
attributed to the presence of the charcoal. The recoveries for compounds A
and B are presented graphically in Figure 5. Compound A shows slightly
poorer recovery on Tenax than B, but significantly better recovery on Tenax-
Tenax/charcoal pairs.
Compounds A and B are chemically dissimilar with B being somewhat polar and
A having the lower boiling point. The recoveries for compound B on the
Tenax-Tenax/charcoal pair for each increasing 5-liter interval were 96, 79,
66, and 56 percent (see Figure 5). For a 20-liter sample, the estimated
average recovery is 1U percent. For the application in question, it was
decided to keep the sample volume at 15 liters with an estimated average
recovery of 80 percent.
During the actual field sampling, distributed air volume samples were col-
lected. Concurrent samples were collected at 1, 1.5, and 2 times the nomi-
nal flow rate for sample volumes of 14, 21, and 28 liters. No differences
were found in the calculated concentrations for compounds A, B, C, or D.
For compounds A and B, this was attributed to the fact that actual field
sampling rates were less than 50 ml/min and the laboratory study used 500
ml/min. This indicates that the laboratory validation method is a "worst-
770
-------
case" approach. This application involved four compounds that, according to
listed references, would have required at least two (T01 and T02) if not
three separate sampling and analysis methods.
Autosampler Validation
We have performed a preliminary evaluation study to compare the Tekmar 4210
autosampler performance with the "clamshell oven" using six compounds which
cover a boiling point range from 24°C to 152°C. One water—soluble compound,
2-butanone, was included even though its recovery from the unheated water-
purge vessel was not expected to be acceptable. The standards were loaded
from gas bottles onto Tenax and Tenax/charcoal tube pairs using a flash
vaporization device at three levels (nominally 50 ng, 250 ng, and 1000 ng).
Traps were loaded in triplicate at each level for analysis by both "clam-
shell" and autosampler. Recoveries from trap desorption were determined
versus on-column injections of the same standards used to load the traps at
all three levels. Results are summarized in Table V. These data indicate
that the Tekmar Model 4210 autosampler performs equivalently to the "clam-
shell oven" for thermal desorption of solid-sorbent trap pairs.
Conclusions
The versatility of the described sample introduction system permits much
greater cost-effective use of expensive laboratory instrumentation and
personnel by minimizing instrument downtime and the need for an operator to
master many different complex methods of analysis.
The described on-column recovery test demonstrates that the sample introduc-
tion system is leak free and capable of delivering the sample to the ana-
lytical system without loss and that suitable calibration standards can be
prepared on sorbent traps.
The use of packed-column GC methods for ambient-air analyses usually does
not adversely affect the quality of the data because the columns currently
in use have sufficient resolving power to handle all but the most complex
samples. In addition, packed columns have a greater sample capacity than
capillary columns, which is very important in the thermal desorption of a
sorbent trap because the sample cannot be reanalyzed using a smaller aliquot
as can solid or water.
A laboratory validation procedure has been developed for the application of
solid-sorbent sampling and analysis methods to specific VOC's. We were able
to simplify ambient air monitoring for four diverse toxic volatile compounds
by employing Tenax-Tenax/charcoal trap pairs. A synergistic effect is
apparently created when the two sorbents, Tenax and charcoal, are combined.
High-boiling components not amenable to Method T02 never reach the charcoal
and are trapped on the Tenax, while lower boiling components not amenable to
Method T01 are trapped in the charcoal and can be thermally desorbed at the
lower desorption temperature required by Tenax.
The autosampler described here was shown to be equivalent in performance to
the simple "clamshell" desorber. This type of instrument automation should
make laboratory operations much more efficient and lower the cost of VOST
and ambient air analyses performed according to the methods described here.
771
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Acknowledgements
Special thanks are extended to Alan D. Zsffiro who performed the majority of
the analytical work, to John W. Prohaska who managed the entire VOST valida-
tion effort and contributed many helpful suggestions, and to Anthony S.
Wisbith for his assistance in evaluating the ambient air data.
The United States Environmental Protection Agency sponsored the VOST valida-
tion project, during which a portion of the development work reported in
this article was completed.
References
1. E. D. Pellizzari, et al, "Collection and analysis of trace organic
vapor pollutants in ambient atmospheres. Thermal desorption of organic
vapors from sorbent media." Environ. Sci., Technol., 9(6):556-560,
1975.
2. E. D. Pellizzari, et al, "Collection and analysis of trace organic
vapor pollutants in ambient atmospheres. Technique for evaluating
concentration of vapors by sorbent media." Environ. Sci., Technol.,
9(6):552-555, 1975.
3. E. D. Pellizzari, et al, "Collection and analysis of trace organic
vapor pollutants in ambient atmospheres. The performance of a Tenax GC
cartridge sampler for hazardous vapors." Analytical Letters,
9(0:45-63, 1976.
4. E. D. Pellizzari, et al, "Collection and analysis of trace organic
vapor pollutants in ambient atmospheres by gas chromatography/mass
spectrometry/computer." Anal. Chem., 48(6):803-807, 1976.
5. P. Gorman et al, Evaluation of a Volatile Organic Sampling Train
(VOST), a draft report prepared by Midwest Research Institute, Kansas
City, Missouri under EPA contract No. 68-01-5915, draft dated July 2,
1982.
6. Federal Register, 44, 69464 (December 3, 1979); see also "Method 624
for the analysis of purgeable organics from wastewater," U.S. EPA,
Environmental Monitoring and Support Laboratory, Cincinnati, Ohio, July
1982.
7. R. M. Riggi n, Compendium of Methods for the Determination of Toxic
Organic Compounds in Ambient Air, EPA-600/4-84-041, April 1984.
8. J. F. Walling, "The utility of distributed air volume sets when sampl-
ing ambient air using solid sorbents," Atmos. Environ., 18(4)-.855-859,
1984.
9. J. W. Prohaska, Validation of the Volatile Organic Sampling Train
(VOST) Protocol, Laboratory Validation Phase, final report by PEI
Associates, Cincinnati, Ohio, under EPA Contract No. 68-02-3767,
October 1985.
10. J. W. Prohaska, Validation of the Volatile Organic Sampling Train
(VOST) Protocol, Field Validation Phase, final report by PEI Asso-
ciates, Cincinnati, Ohio, under EPA Contract No. 68-02-3890, October
1985.
772
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11. Test Methods for Evaluating Solid Waste, Physical/Chemical Methods,
U.S. EPA SW846, 2nd. Ed., July 1982.
12. Determination of Volatile Principal Organic Hazardous Constituents
Using the Volatile Organic Sampling Train, draft protocol prepared by
PEI Associates, Cincinnati, Ohio, under EPA Contract No. 68-02-4125,
work assignment No. 62, November 1985.
13. Evaluation of Systems for Loading Organic Compounds on Solid Sorbents,
report prepared by PEI Associates (formerly PEDCo Environmental),
Cincinnati, Ohio, under EPA Contract No. 68-02-3431, work assignment
No. 58, June 1982.
773
-------
TABLE I. VALIDATED VOC'S FOR 5 METHODS (6,7,10,11)
. 1,1 Mtchcxls
Balling
point, 5030 .
Compound 'C 624 8240® T016 T02C V0ST°
Chlorooethane
-24
X
X
Vinyl chloride
-14
X
X
X
Bromomethsne
4
X
X
Chloroethane
12
X
X
Tr ichlorofluoromethane
24
X
1 • 1-Dlchloroethene
32
X
X
X
Methylene chloride
40
X
X
X
3-Chloropropene
45
X
Carbon disulfide
46
X
trana-1,2-dlchloroethene
48
X
X
Acetone
56
X
1,1-Dlchloroethsne
57
X
X
Chloroform
61
X
X
X
Vinyl acetate
72
X
1~1,1-Trlchloroethane
74
X
X
X
Carbon tetrachloride
77
X
X
X
Aerylonltrlle
7B
X
Benzene
80
X
X
X
X
2-Butanone
80
X
1,2-Dlchioroethane
84
X
X
X
Trlchloroethcne
87
X
X
X
X
Bromodlchlorone thane
90
X
X
1-H«ptenc
94
X
1,2-Dichloroprop*ne
97
X
X
X
Heptane
9B
X
2-Chloroethylvinyl ether
108
X
X
Toluene
111
X
X
X
X
cis-1,3-Dichloropropene
112
X
X
trans-1, 3-Dichloropropene
112
X
X
1ti,2-Trlchloroethsne
114
X
X
4-Methyl-2-pentanone
119
X
Dlbromochloromethane
120
X
X
Tetrachloroethene
121
X
X
X
1a 3-Dlchloropropane
125
X
2-Hexanone
127
X
Chlorobenzene
132
X
X
X
1,2-Dlbrosoethare
132
X
Ethylbensene
136
X
X
X
Xylenes
136
X
X
Styrene
146
X
1,1,2# 2-Tetrachloroethane
146
X
X
Bromof orn
150
X
X
X
Cumene
152
X
BTomobensane
155
X
1,3-Dlchlorobentene
17 2
X
1f 4—Dlchlorobenzene
173
X
X
Benzyl chloride
179
X
L a 2-Dlchlorobenzene
180
X
Nitrobenzene
211
X
* These compounds arc reported for water and soils according to the Contract
laboratory Protocol as revised September 1984.
The tentative compounds listed for this method are nonpolar ones with boil-
ing pointe between BO and 2D0'C,
C The tentative compounds listed for this method are nonpolar ones with boll"
log points between -15 and 120*C.
d The tentative compounds listed for this method are ones with boiling points
batween 25 and 125*C.
774
-------
TABLE II. COMPARISON OF METHODS FOR VOC ANALYSIS
Method No.
Matrix Means of sample Introduction GC column type
T01
T02
VOST
624
5030/8240
Ambient Thermal desorption
air Cryogenic trapping
Ambient Thermal desorption
air Cryogenic trapping
Stack Thermal desorption
gas Purge-trap-desorption
Water Purge-trap-desorption
Solids Purge-trap-desorption
Subambient
Capillary
Subambient
Capillary
Packed
Packed
Packed
TABLE III. RECOVERY OF HSL VOLATILE COMPOUNDS
Percent
recovery range
Number (%)
of compounds
70 to 130
25 to 50
130 to 150
33 (86.8)
4 (10.5)
1 (2.6)
TABLE IV. VALIDATION RESULTS FOR SORBENT MEDIA AND SAMPLE VOLUME
Trap type
Compound
5.0 L
Recovery, X
7.5 L 15 L
20 L
Tenax
A
B
C
D
49
58
101
105
17
39
98
118
1
3
99
113
NA
NA
NA
NA
Tenax and
Tenax/Charcoal
A
B
C
D
90
91
98
98
85
79
99
101
82
60
96
110
74
53
95
100
NA = Not analyzed.
775
-------
TABLE V. AUTOSAMPLER VALIDATION RESULTS
Boiling Percent recovery
Compound point, °C Clamshell Autosampler
Trichlorofluoromethane
24
96.2
~
7.5
96.9
~
5.6
Trichloromethane
61
96.1
~
9.7
98.2
~
14.9
2-Butanone
80
17.2
+
7.1
13.6
3.4
Methylbenzene
111
113.6
~
8.4
116.4
+
8.0
Tetrachloroethene
121
119.1
~
10.6
107.3
jh
6.0
(1-Methylethyl)benzene
152
123.0
~
28.7
111.1
+
6.4
776
-------
10 cm
u cm
1.0 g TENAX
1.0 J charcoal
GLASS WOOL
1/4 in. SHAGELOK 316-55
NUT AND CAP
(SUPEITEX N-J FERRULES)
m
NUMBER
1.6 g OF TEKAX
GLASS WOOL
v« in. SHAGtLOK 316-SS
NUT AND CAP
(SUPELTEK M-l FEPRL'LES)
Figure 1. Sorbent trap configurations.
TENAX AND
TWX/CHARCQAL
TRAPS
OPTIONAL
PURGE VESSEL
BY-PASS
LINE
\
"CLAMSHELL"
HEATER
H« FLCN
CD
THERMAL OESORPTION
CHAFER
PLOW T
GC
i o-s:
D-?
I?
FLOW DURING
DESOBPHON
l"LOW DURING
ADSORPTION
©0©
cEtgsCD-
ANAirTlCAL TRAP
WITH KEATING COIL
(0.3 cm DIAMETER
BY 25 cm LONG)
Ht
:hd
:hd
VENT
PURGE
COLUMN
HEATED
5S LINE
TEDWR LSC-2
PURGE-TRAP
DESORPTION l«IT
©
©
©
TENAX (15 an)
SILICA GEL (3.7 cm)
CHARCOAL (3.7 en)
Figure 2. Schematic of sorbent trap desorptlon
and purge and trap apparatus.
777
-------
MEAT TAPE
» -1S0-C
METAL
FITTINGS
TRAPS
¦^TOO inl/min
1/2 in, O.D.
4 in. LONG
SYRINGE GLASS CHAMBER
PLUG SEPTUi
_$ n2 SUPPLY
FLOW CONTROL
VALVE
Figure 3. Flash vaporization apparatus for
loading standards onto sorbent traps.
FRONT V1EM
SIDE VIEM
PURGE
VESSEL
COKTROL PANEL
Figure A. Autosampler for thermal desorption
of sorbent traps or trap pairs.
778
-------
125
100
25
I
T
1
1
¦
A
TENAX
TRAP
~
6
TENAX
TRAP
©
A
TENAX
+ TENAX/CHARCOAL
A
B
TENAX
+ TENAX/CHARCOAL
©
/~V
©
"""*
©
0
^7A
~
i
•
I
9
i
0 5 10 15 20 25
LITERS
Figure 5, Tenax trap and Tenax + Tenax/charcoal trap
pair recoveries for compounds A and B.
779
-------
EVALUATION OF METHOD 25 NONMETHANE ORGANIC
ANALYZER DESIGN
Maurice Jackson,
Gary B. Howe, and R.K.M. Jayanty
Research Triangle Institute
C.E. Riley and G.D. McAlister
U.S. Environmental Protection Agency
Under contract to the United States Environment Protection Agency,
Research Triangle Institute has been conducting research to improve the
precision, accuracy and limit of detection attainable with the EPA Method 25
nonmethane organic (NMO) analyzer. In Method 25, volatile organic carbon
(VOC) samples are collected by drawing gas from an emitting source through a
dry ice cooled sample trap and iato an evacuated collection tank. The hy-
drocarbon concentration emitted from the source is determined on a per-car-
bon basis by catalytically converting the trap and tank sample fractions to
CO2 and quantitating the amount of CO2 produced using the NMO analyzer.
A reduction catalyst evaluation led to the selection of an NMO analyzer
reduction catalyst which operates at a moderate temperature and displays no
appreciable effect on peak shape.
A gas chromatographic column system which provides better permanent gas
separation and hydrocarbon quantitation was also selected for use in the NMO
analyzer.
780
-------
Introduc tion
Method 25 was developed in the mid 1970's as a means of determining the
amount of volatile organic carbon (VOC) emissions from stationary sources.
After stack sampling and sample trap recovery, the quantitative measurements
of the method are performed on a unit known as the nonmethane organic (NMO)
analyzer. This unit is an oxidation/reduction gas chromatograph which se-
parates permanent gases (methane, carbon monoxide, and carbon dioxide) from
hydrocarbons so that a total hydrocarbon concentration may be determined.
Since the analyzer does not speciate between hydrocarbons, the instrument
must respond equivalently to all hydrocarbons to generate valid NMOC data.
The equivalency of response is achieved by catalytically oxidizing the hy-
drocarbons to CC>2 and reducing the CO2 to methane which is measured by a
flame ionization detector (FID). Though the operating principles are sim-
ple, there are numerous configurations possible for the NMO analyzer. In
the years since the method's inception, each contractor performing Method 25
measurements has attempted to develop this own analyzer configuration with
varying degrees of success. The purpose of this evaluation to standardize
the configuration of the NMO analyzer and the associated materials necessary
for Method 25 analyses.
The main concerns with the present analyzer design as recommended in
the Federal Register are 1) overly complex plumbing arrangement; 2) inade-
quate GC column temperature control; 3) poor separation of nonmethane or-
ganics from high concentration carbon dioxide; 4) poor recovery of oxygen-
ated compounds; and 5) unspecified reduction catalyst. The three specific
objectives of the investigation were 1) selection of a reduction catalyst
and optimization of its operating conditions in relation to analyzer per-
formance; 2) development of a GC column system for the separation of the
permanent gases from nonmethane organics; and 3) evaluation of instrument
performance with the modifications described above.
Experimental Methods
Reduction Catalyst Evaluation
The NMO analyzer reduction catalyst and its associated operating con-
ditions have a direct effect on the instrument's sensitivity, linearity, and
analytical precision. Prior to the reduction catalyst evaluation, three
candidates were selected from the catalysts available commercially. Each
material was applicable to the hydrogenation of carbon oxides, was readily
available and relatively inexpensive. These materials were:
- Low carbon nickel powder, 100 mesh, 99.999% pure, sold by Johnson
Matthey Inc.
- 60 to 65Z nickel on alumina powder, reduced and stabilized, sold
by Alfa Chemical Company.
- 50% nickel on a 1/16-inch extruded support, sold by Harshaw Chemical
Company.
Tests of the first two materials allowed comparison of pure nickel with
a percent-loading of nickel on an inert support. The powder forms were
selected to reduce the unpacked volume of the reactor tube and produce the
optimum peak shape. The final material allowed evaluation of the effect of
an extruded substrate on peak shape and reduction catalyst efficiency.
Each catalyst was evaluated for both reduction catalyst efficiency and
peak shape versus temperature. Three inches of a 1/4-inch OD Inconel® tube
were packed with catalyst and installed in a vertical tube furnace. The FID
response was calibrated with a one percent methane in air mixture. Reduc-
tion catalyst efficiency was evaluated by injecting one cubic centimeter
(cc) samples of a one percent carbon dioxide in air mixture through the
heated catalyst beds and by measuring the effluent methane concentration by
FID. The initial catalyst temperature was 250°C and was increased in 50°C
increments up to 400°C. The reduction efficiency of each catalyst was de-
termined by comparing the response factors (area counts/ppmC) produced after
CO? reduction to methane with the response factor produced by the methane
standard. The response factors would be equal in the case of 100 percent
catalyst efficiency.
781
-------
In addition to the reduction efficiency measurements, determinations of
peak shape were performed at each temperature. These measurements involved
the analysis of a 55.6 parts-per-million (ppra) CO2 in air standard in ad-
dition to the one percent COj standard. The lower concentration standard
was used to assess the effect of concentration on the catalyst peak shape
produced. A high chart recorder speed was used during peak elution to allow
assignment of peak asymmetry factors (see Figure 1). The goal for the peak
asymmetry factor was 1.2 or less. This degree of peak asymmetry is consi-
dered normal in gas chromatographic analysis.^ The peak width at one-half
height also was used as a quantitative measure of peak broadening.
GC Column Evaluation
Three materials initially were tested as possible chromatographic col-
umn materials for use in the NMO analyzer. The analyzer GC column performs
the separation of permanent gases (methane, CO, and CO2) from nonmethane
organics. The GC columns used to date have either provided poor separation
between the permanent gases and hydrocarbons, or presented difficulty in
quantitatively releasing the hydrocarbons upon backflush and heating. The
three materials tested were 60/80 mesh Carbopack® B, 60/80 Porasil® B, and
60/80 mesh Unibeads® IS. The main advantages of the Carbopack® were 1) its
nonselective adsorbence which of all organics strongly independently of
their structure; 2) was relatively chemically inert; 3) its thermal stabi-
lity which allowed heat desorption up to high temperatures; and 4) minimal
adsorption of water and light gases such as methane.
Tne Unibeads® IS and Porasil® B materials were selected because they
are able to separate components based on molecular size rather than chemical
characteristics, a useful quality in separating permanent: gases from non-
¦ueLiimit: or^auics.
Each material was packed into a 2-fc. length of 1/8-in. 0D stainless
steel tubing and installed in Che column oven of a Perkin Elmer 3920-B gas
chromatograph. A 10-port stainless steel rotary valve was used to inject
one cc aliquot3 of test gas. An oxidation catalyst consisting of 19 percent
chromia on 1/8-in. alumina pellets and operated at 650°C was used to convert
the organics to carbon dioxide. The reduction catalyst consisted of a 3-in.
long, 1/4-in. 0D tube packed with 100 mesh nickel powder which was mounted
vertically within a tube furnace. The catalyst was maintained at 400°C
using on Onega Model 802M temperature controller equipped with a Type K
thermocouple.
A mixture of 20 ppm ethane, 20 ppra propane, 50 ppm carbon monoxide, 50
ppm methane, and two percent carbon dioxide in air was analyzed with the
2-ft. columns of each proposed material. These tests provided data regard-
ing separation of the permanent gases from NMO, total analysis time, accur-
acy of MM0 analysis, and peak shape. Optimal analytical conditions for each
column during analysis included column temperature, carrier gas flow rate,
and valve switch timing for column backflush.
After selection of a GC column, compound response tests were conducted
to ensure that no compounds would interact with the coluain system and pre-
vent analysis. Samples of carbon dioxide in air, methanol in air, acetone
in air, toluene in air, and hexane in air were analyzed at concentrations of
100 ppmC and 10000 ppraC.
Instrument Performance Evaluation
The NMO analyzer, equipped with the selected reduction catalyst and GC
column, was tested to determine the linearity, precision, and limit of de-
tection of the new system. Standards consisting of 20 ppm, 200 ppm, and
3000 ppm propane in air, and 50 ppm, 500 ppm, and 10000 ppm carbon dioxide
in air were analyzed in triplicate. The relative standard deviation for
each set of injections was determined as well as the overall mean response
factors. The goals for these parameters were two percent relative standard
deviation or less and agreement between the individual response factors and
the mean response factor of + 2.5 percent.
The detection limit for both carbon dioxide and propane also were
measured. Test gases consisting of 20 ppra propane in air and 55.6 ppra CO2
in air were analyzed in replicate. For each analysis, the peak height,
782
-------
where:
attenuator setting, concentration, and peak width at one-half height were
recorded. Following each analysis, the attenuator was set to a value which
prominently displayed the baseline noise on the chart. An injection of zero
air then was performed and the height of the largest noise peak within a
period of 10 times the sample peak width was recorded and the limit of
detection then calculated by Equation I.
Clod = 1-9718 hn An C3 / hs As (1)
hn = peak height of noise, ma
An " attenuation during noise measurement
Cg = sample concentration, ppm
hg * peak height of sample, mm
Ag = attenuation during sample measurement
This detection limit is equivalent to three times the standard
deviation of the noise as recommended by the American Chemical Society
Committee on Environmental Analytical Chemistry.^
Results and Discussion
Reduction Catalyst Selection
The 50 percent nickel on 1/16-in. extruded support and the 100 mesh
nickel powder were tested for reduction efficiency and peak distortion in a
temperature range from 250-400°C. The 60-65 percent nickel powder was
eliminated from consideration because it presented too high a restriction to
carrier gas flow due to its small mesh size. The reduction catalyst
efficiency versus temperature data presented in Table I showed the reduction
efficiency of each catalyst to increase up to 350°C, after which a slight
drop in efficiency was observed. The 100 mesh nickel powder provided better
reduction efficiency at all but the lowest temperature. The decrease in
reduction efficiency between 350 and 400°C was also less pronounced with the
nickel powder.
The peak shape versus temperature data reported in Table II showed each
catalyse to produce very broad tailing peaks at low temperature. This
result is revealed by the large asymmetry factors and peak width numbers.
The peak shape and peak width produced by each catalyst improved as the
temperature was increased. The 100 mesh nickel powder ultimately produced
the narrowest peaks with the smallest asymmetry factors. At 400 C the peak
shape and width observed after CO2 reduction by the nickel powder was
essentially identical to the methane peak shape observed with no reduction
catalyst. This result meant that the nickel powder would be essentially
"invisible" in the analyzer 9ystem with regard to peak distortion effects
when used at 400°C,
Development of GC Column System
An initial screening of the proposed column packings served to identify
the most promising materials and provided valuable information as to the
column dimensions and heating procedures necessary for successful nonmethane
organic analysis. In the initial tests, a 2-ft. long, 1/8-in. diameter
column of each material was packed and installed in the analyzer system. A
test gas mixture consisting of 49.2 ppm of carbon monoxide, 48.9 ppm of
methane, 19200 ppm of CO2, and 19.50 ppm propane was analyzed to determine
each material's ability to separate these components. Some secondary tests
used a mixture of 50020 ppm COj, 24.86 ppm propane, and 10.95 ppm toluene
and the mixture used to determine the extent to which relatively heavy
compounds were retained. The results obtained are shown in Table III.
The 2-ft. Carbopack® column was unable to separate CO2 from the other
permanent gases or completely separate CO2 from propane. In subsequent
tests using a 6-ft. Carbopack® column, the permanent gases were still un-
separated. Injections performed with the gas containing toluene showed the
Carbopack® to interact strongly with this compound thereby causing an ex-
tremely poor backflush peak. The Porasil® B also was unable to separate the
permanent gases and provided only partial separation between CO2 and pro-
pane.
The Unibeads® IS material proved to be the most promising for use in
763
-------
the NMO analyzer at the end of the initial screening. A 2-£t. Unibeads®
column provided better separation of the permanent gases than had an equiva-
lent length of Carbopack® B. Tests in which hydrocarbon and permanent gases
were included showed the hydrocarbons to be separated from CO2 and to elute
as a single peak upon backflushing and heating the column. Due to the su-
perior separation provided by the Unibeads® material, the Carbopack® was
eliminated from further consideration.
Though the 2-ft. Unibeads® column provided excellent separation between
the permanent gases and hydrocarbons larger than propane, ethane and ethy-
lene were small enough in size that they eluted among the permanent gases.
A 6-ft. Unibeads® column operated at 80°C successfully separated the smaller
hydrocarbons from the permanent gases but led to unacceptably long CO2
retention times. This result led to the selection of Carbosieve® G for use
as a secondary column material to use in conjunction with the Unibeads® IS.
In the new column system the Unibeads® material was to perform the separa-
tion of the permanent gases and larger hydrocarbons while the carbosieve re-
tained the smaller hydrocarbons as the permanent gases eluted. Testing of
this column arrangement showed it to be capable of separating the small hy-
drocarbons from CO2 while improving the CO2 retention time. A summary
of these tests is presented in Table IV.
It was found that very polar compounds became strongly adsorbed onto
Carbosieve®. Methanol samples remained adsorbed onto Carbosieve® even after
backflush and heating. This development required a modification of the col-
umn system. A 1-ft. section of the Unibeads® IS was placed in front of the
Carbosieve® G to trap methanol and all organics larger than propane. A
2-ft. Carbosieve® section was used to retain the smaller hydrocarbons and
separate the permanent gases. A summary of the tests performed with this
new column system is shown in Table V.
Single Component Equivalent Response Test Results
The tests of equivalent analyzer response to various hydrocarbons were
performed with mixtures of carbon dioxide in air, methanol in air, acetone
in air, toluene in air, and hexane in air. The responses of these mixtures
at concentrations of approximately 100 ppmC and 10000 ppmC were recorded and
compared to the response produced by a methane standard gas. The data gen-
erated are presented in Table VI.
In general, the responses produced by the high level gas mixtures
agreed better with the methane response factors than did the low level mix-
tures. Part of the disagreement at low level was due to the fact that the
lower concentration organic mixtures were produced by diluting the high
level mixtures. Errors of approximately one percent in the dilution process
could account for the discrepancies seen at low level considering the fact
that the starting concentrations were approximately 10000 ppmC. Even with
these dilution errors, the response factor discrepancies observed at low
level were no more than a few percent, with the exception of acetone. This
compound produced relatively broad peaks at low level, which probably lead
to integration errors.
Linearity and Precision Tests
The complete analyzer was tested for linearity and precision by the
analysis of propane and carbon dioxide in air. Standards consisting of ap-
proximately 20 ppra, 200 ppra, and 3000 ppm propane in air and 50 ppm, 500
ppm, and 10000 ppm carbon dioxide in air were analyzed in triplicate. The
relative standard deviation for each set of injections as well as the over-
all mean response factors then were determined. The goals for these param-
eters were two percent relative standard deviation or less and agreement
between the individual response factors and the overall mean response factor
of + 2.5 percent. The data obtained are shown in Table VII.
Excellent precision was observed between the individual injections of
propane and CO2 at each concentration as is demonstrated by the low re-
lative standard deviation numbers. Exceptional agreement also was noted
between the mean response factors produced at each propane and CO2 con-
centration, thereby demonstrating the instrument's linearity over a wide
concentration range. The close agreement between the overall propane and
C02 response factors confirms the quantitative processing and catalytic
784
-------
conversion of organics within the analyzer system.
Determination of the Detection Limit
The final test performed on the analyzer was a determination of the
detection limit. The detection limits for both carbon dioxide in air and
propane in air were established by the analysis of low level concentrations
of each of these gas mixtures, and use of Equation 1. The limits of detec-
tion for propane and CO2 are listed below.
Propane Detection Limit " 0.10 ppm
CO2 Detection Limit = 0.16 ppm
It should be noted that the detection limit is not the limit at which a
compound may be quantitatively analyzed. The limit of quantitation is ap-
proximately three times higher in most cases.^
Conclusions and Recommendations
Reduction Catalyst
The results of both the CO2 Reduction Efficiency and the Catalyst
Peak Distortion Tests led to the selection of the 100 mesh nickel powder as
the recommended Method 25 reduction catalyst. This catalyst provided the
most efficient reduction of CO2 to methane at the temperature required to
produce acceptable peak shape. At 400*C the methane peak shape produced
following COj reduction was almost identical to the methane standard peak
shape observed with no catalyst in the system. This indicated that the re-
duction reaction had no effect on peak shape when the catalyst was operated
at this temperature.
Recommended Chromatographic Column System
A chromatographic column system consisting of a 1-ft. long, 1/8-in.
diameter column of 60/80 mesh Unibeads® IS followed by a 2-ft. long, 1/8-in,
diameter column packed with 60/80 mesh Carbosieve® G was selected for the
NMO analyzer. In this column system the Unibeads® material is used to trap
very small polar compounds such as methanol and all hydrocarbons larger than
propane. The Carbosieve® G performs the separation of the permanent gases
and retains the smaller hydrocarbons. The column system is heated to 195*C
and backflushed to desorb the hydrocarbons for NMO analysis. The advantages
of these two materials derive from the fact that each is an uncoated adsor-
bent material rather than a coated column packing. Being uncoated adsor-
bents, they are much less likely to irreversibly adsorb hydrocarbons during
Method 25 analyses thereby altering the analysis results. A chromatogram of
a typical analysis is presented in Figure 2.
Injection onto the column is performed at 85°C. At this temperature
there is partial separation of CO and CH^, Complete separation of these
two components may be achieved by performing the injection at a lower tem-
perature. However, the CO2 elution time will be lengthened slightly in
this case. After injection, all compounds through CO2 should be allowed
to elute at S5°C. The column should be backflushed and immediately heated
to 195*C after CO2 elution to desorb the trapped hydrocarbons for NMO
analysis. The entire cycle should be approximately six minutes long.
Column Materials Preparation
A cleanup of the column materials is required prior to installation of
the column system in the NMO analyzer. Initially the Unibeads® material
should be packed in a 1-ft. long section of 1/8-in. OD stainless steel tub-
ing. The Carbosieve® G should be packed into a 2-ft. long section of the
same diameter tubing. Each of the column sections should be heated sepa-
rately with helium flow at 195*C for at least one day, before the column
sections are joined. This heating serves to cleanup the materials consider-
ably and greatly reduces the baseline rise seen when the column system is
backflushed and heated during NMO analysis. Failure to perform this cleanup
step will result in an unusable system.
Nonraethane Organic Analyzer Design
A diagram of the suggested NMO analyzer configuration is presented in
785
-------
Figure 3. The GC column system is the same as described previously. The
oxidation catalyst consists of a 14-in. length of 3/8-in. OD Inconel® tubing
which is mounted vertically within a tube furnace. The center 2-inches of
the tube are packed with 1/8-in. pellets of 19 percent chromia on alumina
catalyst. The remainder of the tube is packed with quartz wool to reduce
dead volume and hold the catalyst in place. The oxidation catalyst tempera-
ture should be maintained at 650*C. Helium at approximately 30 cc per min-
ute should be used as carrier gas. Oxygen at a flow rate of approximately
2.2 cc per minute should be added to the carrier stream just before the
oxidation cataLyst.
The reduction catalyst is composed of a 3-in. length of 1/4-in. OD
Inconel® tubing, packed with pure 100 mesh nickel powder (Aesar® catalog
number 12966). The catalyst tube should be mounted vertically and heated to
400*C within a tube furnace. Hydrogen at a flow rate of approximately 40 cc
per minute should be added to the carrier stream immediately before the re-
duction catalyst. The hydrogen flow rate should be adjusted to provide op-
timum FID response and prevent flame blowout during valve actuation. The
hydrogen in the reduction catalyst effluent is used for the FID flame;
therefore the addition of hydrogen at the FID is unnecessary and will only
reduce instrument response.
References
1. L. R. Snyder and J. J. Kirkland, Introduction to Modern Chromatography,
John Wiley and Sons, Inc., 1979 (pp. 222-225).
2. Joseph E. Knoll, "Estimation of the Limit of Detection in Chromato-
graphy," Journal of Chromatographic Science, 23, 422-425 (1985).
3. ACS Committee on Environmental Improvement, Daniel Mac Doughal, Chair-
man, "Guidelines for Data Acquisition and Data Quality Evaluation in
Environmental Chemistry," Analytical Chemistry _52_ 2242-2249, 1980.
Table I. Reduction Catalyst Efficiency Versus Temperature.
Nickel Powder
Catalyst Reduction Extruded Catalyst
Temp., "C Sample Cone, (ppra C) Efficiency Reduction Efficiency
250 C02 10093 73.75 88.13
300 C02 10093 100.25 97.73
350 C02 10093 103.04 101.33
400 CO2 10093 101.97 96.80
Table II. Peak Shape Versus Temperature Test Results.
Catalyst Nickel Powder Extruded Catalyst Hick«l ?ovd«r Extruded Catilyat
Te-flp. , C Sawple Cone. (ppmC) Asvwrretry Kactor AayraneCry Factjr ?»ak 'Jiith (sec) Peak Kidtn
9850.0
0.f><*3
1.00
1. 9
1.55
250
CO j
10091. 0
*
9.21
*
li .90
250
CO?
55. b
*
*
*
-
100
C07
10093.0
7.16
2.71
12.19
2. si
300
CO 2
35. 6
6.^8
*.43
10.37
3.45
350
co2
M093.C
1.53
I. to
1 ¦ 77
1.83
350
Co 2
55.6
1.51
:.uo
1.7*
1.84
400
co2
10093.0
O.bW
0.99
1.6 J
1.6?
400
co2
0.6M
1.25
t.SZ
1. 7H
<4 00
CKi.
9850.0
0. 573
1.00
I.*3
:. ft?
*Pfak too distorted tor «fteasMr*«*or of riineniiom
786
-------
Table III. Column Material Screening Results,
Colunn
Coition Length
Material (Uset)
Injection Backflueh
Teap. , *C Teiap. , *C Tes c ^ii
Comment
Carbopack* 3 2
Carbooack* 3 6
75 150 ca^, CO, co2,
Propane
75
Mo separation of penunsne g&aes, Fro--
sane not completely separated from C^2*
15a coj, co,
Propane
No separation of permanent gaaea.
pane .separated £ron C02.
Pro-
Carbopack* 3 6
PorasiL* 9
Unibeads® -IS
T5
75
75
1)0 CO2, Propane
Toluene
150 CHt, CO, CO,
Propane
120
CHfc, CO, C02
Propane
Propane and C0^ separated. Toluene
calls -remendouBIy on iackf Lush and it
strongly retained by caiman,
No separation of permanent ^aaes. Pro-
pane partially separated from COj*
Partial separation of methane and CO
froa C&2, Partial separation of propane
from CD^.
Unibeada-* IS
50
120 CH4, C0» CQ2>
Propane
Complete jeparatLon of CO/CH^ p«ak from
CO?- CamplRca saparatioQ of propane
from CO? 3ut Lt eiutea too quickly Co
baekflush. Analysis time extended great-
ly because o£ lover injection ienper*-
ture.
Unibeada* IS
?5
L50 CHut CO, CO^,
Propane
Complete separation of C0/CH4 peak from
C02- Enough separation between COj and
propane for propane to be backflushed.
Analysis time faster.
Unibeads* 15
T5
150 COj* Propane,
To luene
CO2 peak completely separated. On back—
flush, propane and toluene are separated
partially.
UnLtcatls'* IS
80
150 CC>2> Propane
To Luene
C0^ peak completely separated. Propane
and toluene are aCill separted aora*vnac
on baekflush.
Ilnibeids4 IS
50
l50 CO, CO2 CO2 coo-pletely separated. Propane and
toluene elute ae a dingle oeak an back-
flush.
Unibe-ade® IS
150 CO, CWi, CQZ
Ethane
Ethane separated from CO/CH^ ?eak aod
froa CO* seak.
Table IV. NMO Analyzer Column Evaluation Test Results.
Column Material Injection Backflush
and Length Temp. , "C Temp. , "C
3 feet SJnibeads* IS SO
3 feet Unibeada* 15 ~ 110
6 inches Carbosieva®
3 feet Unibeadi* IS * 90
& inches Carbosieve*
HA
160
C0i~ Ethylene
CO2, Ethylene
CO2» Propane,
Toluene
Coopiete separation of ethylene and CO2
but long CO2 elution :iae,
AlBOst ic«plec« separation of ethylene
and CO2. CQn retention cine reduced.
Propane and toluene elute as a single
peak on baekflush uhich tails somewhat.
3 feet Umbeada* LS *
6 inches Carbosieve*
75 160 CO, CH*, CO2, Separation of CO/CHfc peak fro« CO2.
Propane Propane elates on beekfluah and tai La.
(continued)
787
-------
Table IV. NMO Analyzer Column Evaluation Test Results (continued).
Co«uan Material Injection
and Length Tanp., #C
Backfluah
Tewp. , *C
Teat Saa
Cooaenc
3 feet Unibeads* IS *
6 inches Carboaieve*
ao
160
CO, CH4, CO?,
Propane
Separation of C0/CH^ peak froa CO2-
Propane elutea on backfluah and tails.
Analyaia tin is faster.
3 feet Unibeada* IS *
6 inches Carboaieve*
90
1BG
CO, ca^( CO^,
Propane
Propane tails leaa. Analyais tioc is
faacer.
3 feet Ifnibeada* IS *
6 Inches Carboaieve*
90
iao
CO2» Propane,
Toluene
Propane and toluene elute aa a single
peak on backfluah.
3 1/2 feet Unibeada* IS
* 6 inches Carbosieve*
ao
1B0
CO, CHfc, COj,
Propane
Partial separation of CO and CH4 at»d
beccer separacion of these coaponenca
from CO2. Propane ia still sharp on
backfluah.
3 1/2 feec 'Jnibeada* 15
* 6 inches Carboaieve*
ao
100
CO, CH4, CO2,
Ethane, Pto-
pane
Parcial separation of CO aod CH^.
Ethane and propane elute aa a single
peak on backfluah.
3 1/2 feec Unibeada* IS
* S inches Carboaieve*
80
NA
CO, CHa, C02(
Ethane, Pro-
pane
All components were allowed to eLute in
forefluah aode to confirm echane sepa-
ration from CO2,
3 1/2 feec Unibeads* IS
* 6 inches Carboaieve*
ao
NA
CCj, EthyLene
The ethylene peak waa completely re-
solved from the CO2 and showed approxi-
mately Che saad retention cime aa ethane,
3 i/2 feet Unibeada* IS
*• * inches Carboaieve*
75
ISO
CO, CH^, CO?,
Ethane, Pro-
pane
laproved separation between CO and CH4
altnough they ire still partialLy unre-
solved. Ethane and propane stiLl elute
as a single peak on backfluah. Total
analysis time ls approxioateiy 370
seconds.
Table V.
Final
Column Analyzer Configuration Test Results.
Column Material Injection
and Length Temp., "C
3ackf luflh
Temp. , "C
Test Gas
Comment
2 feet Carboaieve* C
95
105
CO, CUU, COn
Ethane, Propane
Almost complete separation of CO & CH<^.
Ethane i Propane eLute together on back-*
f lush.
2 feec Carboaieve* G
95
185
Methanol
So peak elutes .
3-1/2 feet Unibeads* IS
no
NA
Methanol
Methanol did not eLute on forefluah.
3-1/2 feet Unibeada* IS
110
190
rtethanoI
.Methanol eLutes as a broad peak on
backflush.
2 feet Carboaieve* G+
3 feet Unibeads* IS
95
185
CO, CH4, CO2,
Ethane, Propane
ALreost compLete separation of CO ft CH^.
CO? retention tine is very long (app.
4 win.). Ethane h Propane eLute to-
gether on backfluah.
2 feet Carboaieve* C+
1 foot Unibeada* 13
B5
185
CO, CH^, C02,
Ethane, Propane
Almost complete separation of CO & CH^.
CO2 retention time is much shorter.
Ethane & Propane elute together on back-
f Lash.
2 feet Carboaieve* C +
1 foot Unibeada* IS
B5
195
Methanol
BTond nethanoi peak elutea on backfluah.
2 feet Carboaieve* C*
I foot Unibeada* 13
B5
195
CO, CH^, C02,
Ethane, Propane
Almost complete reparation of CO & CH^.
ethane & Propane eluce cogether on back-
flush.
788
-------
Table VI. Equivalent Hydrocarbon Response Te9t Results.
Concentration Response Factor Percentage at Methane
Compound (ppoC) (Area Counts/ppsC) Response Factor
Acetone
8003.a
45.43
100.46
Acetone
99.4
49.61
109.71
To Luene
9973.7
46.95
103.82
To Luene
126.2
47.62
105.30
Hexane
1017L.S
44,62
98,67
Hexane
101.3
46.87
103.64
CO 2
L0093.0
45.41
100.42
COz
55.5
44.95
99.40
MethanoI
10010.2
45.04
99.60
Methanol.
97.2
45.S9
0
¦e-
CD
Methane
9B50.0
45.22
100.00
Table VII. NMO Analyzer Linearity and Precision Te9t Results.
Coispound
Concentration
(ppra)
Percent Relative
Standard deviation
Mean
Response Factor
(Area Counts/ppmC)
Propane
19.9
1.42
44.59
Propane
201.0
0.50
44. 47
Propane
2419.0
0.31
44,40
C02
55.6
0.41
44.95
ca2
509.0
0.26
45. 0B
CO2
10093.0
0.13
45.41
aean propane response factor ¦ 44.52 SRSD ¦ Q.J40
aean C02 response factor ¦ 45.15 SRSD ¦ 0.525
mean overall response factor - 44.81 tRSD * 0.362
Valve Oven
Ice Sample Loop
FID
Helium C*rri9r Gas
fo
Figure 1. Reduction Catalyst Test Schematic.
789
-------
MY'WWirY factor
Figure 2. Peak Asymmetry Factor Measurement.
50 pom .
L
2O0QQ ppffi CO?
WopmCO -
-*20 CP^n d«jpan«
'niecoon aS aC
V
V
i
aackilusn and
.-»•* {195 «C)
Figure 3. Typical NMO Analyzer Chromatogram.
790
-------
Column Oven
[~ GC Column
I rnmnrrirrn
Valve Oven (110 °C)
Helium 1
Carrier Gas |
1 cc [
^ Sample I
L oj Loop j
Air
Vent
Sample Inlet
L
FID
Oxidation
Catalyst
Figure 4. Recommended Nonraethane Analyser Design.
791
-------
DEVELOPMENT AND VALIDATION OF SOURCE PM1Q
MEASUREMENT METHODS
Ashley D. Williamson,
William E. Farthing,
Southern Research Institute, Birmingham, AL
Thomas E. Ward
Environmental Monitoring Systems Lab, U.S. EPA, Research Triangle Park, NC
The introduction of particle size into the Ambient Air Particulate Standards
sucgests the need for size-specific (PM,„) particulate measurements at
1 U
stationary sources as well. Development of PM, ^ sampling methods requires
resolution of several potential technical difficulties. First, an
aerodynamic sizing device must be selected which can be operated with a lOym
size cut, and which is free of artifacts due to misclassification of
particles or anomalous weight changes. The most obvious potential
inaccuracy in PM.Q sampling is due to a "built in" anisokinetic sampling
bias caused by the requirement that an inertial particle sampler must run at
a fixed flowrate to achieve a predetermined size cut, thus making isokinetic
sampling in the manner of Method 5 impossible.
Two promising source PM, Q measurement techniques have been developed which
minimize these potential errors. The first involves a new sampling train
design which incorporates emission gas recycle (EGR). In this train, the
isokinetically sampled stack gas is augmented by the appropriate amount of
filtered recycle gas to maintain the total gas flowrate entering the
inertial sizing device at the level required for a lOym size cut. Hie
second potential method, termed a simulated Method 5 (SIM-5) approach, uses
existing sampling hardware with an altered traversing protocol designed to
maintain anisokinetic sampling errors for the PM. Q particle fraction within
predetermined limits. Both techniques have been documented as potential
sampling methods, including descriptions of equipment, sampling methodology,
data reduction and sampling setup computations, QA/QC, and technical
references. In addition one first generation prototype and two second
generation EGR sampling trains have been constructed and field tested. Four
field trials of each PMj~ method have been conducted, in which the precision
of each method (using colocated dual train techniques) and the comparability
~f each method to the other and to reference isokinetic total particulate
samplers (Method 17) were investigated.
792
-------
DEVELOPMENT AND VALIDATION OF SOURCE PMjQ MEASUREMENT METHODS
Introduction
A revised ambient air standard that regulates particulate matter
smaller than 10 micrometers (PM10) "as been proposed and promulgation is
expected. Although the proposed PMjQ standard regulates ambient air
concentrations, attainment strategies for the new standard will require
information on PM,Q emissions from stationary sources. Furthermore, PM.a
emissions regulations under New Source Performance Standards are possible in
the future. For these reasons, the EPA Environmental Monitoring Systems
Laboratory (Quality Assurance Division) has initiated a research program to
develop and validate source PM,Q measurement methods.
Developing a useful PM,Q sampling technique involves solving several
technical challenges. First, a sampler must be found or developed which can
aerodynamically separate particles with aerodynamic diameters less then
10um. The sampler must be free from artifacts which would misclassify
particles (such as particle bounce or sampler cut shifts) or otherwise give
inaccurate collected mass determinations (such as wall losses or substrate
mass changes). The sampler operating conditions for this particle size cut
must be determined in enough detail to allow the operator to calculate, set
and maintain the PMjQ operating conditions in the field. The PM^ sizing
device also complicates particulate sampling by the introduction of a "built
in" anisokinetic sampling bias. In order to maintain a 10um cut, the gas
flowrate through the sizing device must be held at a predetermined value.
Without a sampling nozzle of continuously variable cross-sectional area,
this fixed flowrate requirement makes isokinetic sampling in the manner of
Method 5 impossible. Since anisokinetic sampling bias can be significant
for particles near 10um, this effect cannot be ignored.
Previous work on this problem at Southern Research Institute has led to
the development of two potential sampling methods - the Emission Gas Recycle
(EGR) sampling train, and the Simulated Method 5 (SIM-5) traversing
protocol. The Emission Gas Recycle (EGR) train in principle eliminates the
problem of anisokinetic sampling bias by simultaneously allowing isokinetic
sampling at the nozzle and fixed flow operation at the inertial sizing
device(s)1 ,2. The train design allows the isokinetic flow of gas into the
sampling nozzle to be augmented by an adjustable amount of filtered,
recycled stack gas upstream of the inertial sizing device. The SIM-5
protocol^ is an alternate candidate method which uses existing
sampling equipment (cyclones or cascade impactors without special gas
recycle adaptations). Hie protocol involves synthesizing a duct traverse
with fixed flowrate runs, using different sampling nozzles if necessary so
that the nozzle velocity at each sample point does not fall outside a
specified range relative to the isokinetic velocity at that point. In this
manuscript we will describe both potential source PM,^ methods, including
the operating principles, hardware, development, and validation studies for
each.
Description of PM,. Methods
i u
PM1q Sizing Device
The two classes of inertial particle sizing devices commonly used for
instack measurements are cascade impactors and small sampling cyclones.
Devices of either type can in principle be used for source PM,3 sampling,
both devices have been used in the course of our methods development program.
Of the two classes, cascade impactors are more familiar, more widely
793
-------
accessible, and have a longer history of field use. Impactor stage D50
values can be predicted with some confidence over the typical range of stack
gas conditions and sampler flowrate. Because of particle bounce and
reentrainment, impactors have limited capacity and must generally be
operated as multistage devices rather than single-cut classifiers.
Multistage cascade impactors provide moderately high resolution particle
size distribution data from which concentrations may be inferred by
interpolation. Hiese data are obtained at the expense of more complicated
preparation, sample recovery and data reduction procedures, thus placing
greater demands on the training, experience and insight of the operating
team. Likewise, more complicated procedures and greater demands on the
sampling crew are required to recognize, prevent, or correct for other
non-ideal effects such as gas/substrate interactions. In summary, cascade
impactors can be useful for PMjQ sizing, especially when detailed particle
size information is also necessary, at the expense of added time and
material costs as well as greater skill and trainng requirements for the
sampling team.
Cyclones, on the other hand, are essentially free from problems of
bounce, reentrainment, and overloading. TTiey have no substrates and are
simple in operation and sample recovery. Cyclones are therefore suitable
for single-stage sizing devices. The principal disadvantages of cyclones
are not operational, but consist of the more limited understanding of
cyclone behavior. Unlike impactors, the of a cyclone cannot be
adequately predicted from geometric considerations. The variation of the
D 's of typical sampling cyclones with stack gas density, viscosity and
flowrate does follow a similar functional form, but laboratory calibrations
of each cyclone type must be performed to develop predictive equations for
the Dg0 of that cyclone over a range of gas conditions. These equations,
moreover, cannot easily be extrapolated to other cyclones or to conditions
beyond the range of the calibration data. Therefore, much more extensive
calibration data must be obtained for the development and validation of a
PMj g cyclone than for a PMjq impactor sampler.
As mentioned above, both cascade impactors and cyclones were used in
this program. A well characterized, commercially available impactor
(University of Washington Mark V) and right-angle impactor precollector
(SoRI/Flow Sensor design- marketed by Andersen) combination was used for
detailed sizing information, especially at sources with low particulate
concentrations. Cyclone I of the SoRI/EPA five-stage series cyclone train
was used as a cyclone sampler, both as a single stage device or in
series with one or more cyclones from the complete train. Previous
calibrations of this cyclone have been extended to determine flowrates to
produce 10um D5Q at each of several gas conditions.
Simulated Method 5 (SIM-5) Technique
The Simulated Method 5 (SIM-5) technique was developed using the
principle of minimizing PM measurement errors within the operating
1 0
constraints of available sampling hardware, ltius commercially available
particle sizing devices (cyclones or impactors) and EPA Method 5 gas
metering equipment were used without significant hardware modifications.
Several sources of measurement error were considered in the development
of the SIM5 protocol. Most of these - such as spatial and temporal
variation of emissions, anisokinetic sampling bias, and random measurement
errors are common to other emissions sampling methods, especially total
particulate sampling. One source of error - inisclassification of particles
- is unique to size specific particle sampling measurements. While some
794
-------
degree of misclassification i3 inevitable due to the imperfect collection
characteristics of inertial sizing devices, misclassification generally
occurs when the sizing device is not operated at the correct flowrate for a
10ym cut. The magnitude of errors from this effect will depend on the
concentration of particles near 1aerodynamic diameter, and are therefore
not predictable in advance for a general source and particulate control
device. Therefore, in order to obtain meaningful PMjg concentrations, both
PMjq methods specify that the flowrate of the inertial sizing device be held
constant at the value calculated for a PM1(, size cut.
Once the decision is made to operate the sampling train at a fixed
flowrate, other sources of error which are common to total particulate
sampling become more problematic. An isokinetic traverse in the manner of
Method 5 is no longer possible. In fact, due to the finite selection of
available nozzles, isokinetic sampling is not generally possible at any
preselected duct location. In SIM-5 fixed-flowrate (i.e., anisokineticJ
sampling is performed within point-by-point restrictions which limit the
worst-case anisokinetic error in PM13 to a specified limit, in this case
±20%. The development of these restrictions is described in the following
paragraphs.
The effect of anisokinetic sampling has been characterized by Belyaev
and Levin5 in terms of an aspiration coefficient, A, defined as measured
concentration/actual concentration:
A = 1 + (R-1 ) B B 1 (1 )
where R = velocity ratio v/u,
v = duct gas velocity at sampling point (cm/sec),
u = gas velocity entering the sampling nozzle (cm/sec),
B = (2 + 0.617/R)K, K = particle Stokes number with respect to the
nozzle, Tv/d,
t = particle relaxation time CD2/I 8u(sec),
C = Cunningham slip factor,
D = particle aerodynamic diameter (cm),
M = gas viscosity (poise), and
d = nozzle diameter (cm).
From the form of equation (1) and the observation that B is
proportional to D2, the general behavior of A can be deduced. A approaches
1 (no sampling bias) as R approaches 1 (isokinetic sampling) or as B
approaches zero (small particle diameter). For a given anisokinetic
velocity ratio, as the particle size increases (B becomes large), the
anisokinetic sampling error (A-1) increases in magnitude until in the limit
of large diameter the deviation approaches the fractional deviation from
isokinetic. (Note that R = 100/1, where I is the familiar percent
isokinetic ratio.) In more familiar terms, for typical source sampling
conditions (17 liters/min sampling rate, 16 m/sec nozzle velocity) and 10um
particles:
A-1 = 0.89 (R-1)
that is, a sample taken at 20% under isokinetic will be biased high by
17.8*.
This same approach can be used to determine anisokinetic sampling
limits to remain within a predetermined sampling error. In the current
SIM-5 protocol, the limits are chosen to give a maximum sampling error of
20% for 10um particles. Corresponding limits on R can be obtained by
substituting d=(4QR/vtt )1/2 and D=1Ogm into equation 1 and solving for stream
velocity
795
-------
36(A-1)uQ1/2(R*)3/z
v 3/2 (2)
tt1/2 (R'-A) (2R'+0.617) (10urn)2
The appropriate value of uQ*/2 depends upon the sampler and the
temperature and composition of the gas. If a single stage PM1Q sampler is
used then Q should be the flow rate which provides a 10ym size cut. With a
cascade impactor the flow rate is somewhat adjustable, but should be
selected to produce at least one size cut above or very near 10ura.
Values for R", where R' is R„- and R . were calculated from Equation
nq.n9 iiicix
2 for various assumed values of uQ * which are in the expected range for
stationary sources and available sampling equipment. The results are shown
graphically in Figure 1 with the upper and lower curves representing R
versus v obtained by setting A=1.2 and 0.8 in Equation 2. The function
R=v/u, with u a constant, is represented in Figure 1 as the curve designated
R(v,u) and running as a nearly vertical line. This function has exactly the
same shape and slope no matter where it is centered on the "R=1" line. It
is needed in reading the appropriate limits, and RmaXf or the
corresponding v •„ and v„,„, determined by the value of u. This vertical
c 3 nun max '
curve is shifted left or right so that its center (at R-1) matches the
nozzle velocity. The limits, Rmj>n and R^,^ or vm^n and vmax, are the values
where the vertical curve intersects the limit curves appropriate for the
yQi/2 value. Typically jjQ1 /2 is in the range of 750 to 1310 for combustion
sources and commercial samplers.
The limits depicted in Figure 1 are broad enough so that the velocities
in a point-by-point traverse at most sources will fall within the specified
limits. However, in some ducts, velocities at some traverse points will be
outside of these limits for one nozzle. In that circumstance, additional
nozzles, having limits which include the other velocities, should be used,
and the traverse divided into two or more subtraverses with different nozzle
diameters.
Another important difference between the SIM-5 protocol and Methods 5
and 17 is the dwell time. In these EPA methods the dwell time is the same
for all traverse points. The measured concentration is a velocity weighted
average for all points, as it should be for determination of emission rate,
because the sampling rate is varied at each point proportional to point
velocity. Since flow rate cannot be adjusted from point to point with a
PM Q sampler, the dwell time at each point must be proportional to the point
velocity to obtain a velocity weighted sample.
Emission Gas Recycle Train
Use of the SIM-5 method should allow PM, . measurements in which
... . 10
isokinetic error is limited to acceptable levels. The Emission Gas Recycle
concept uses modified sampling hardware to eliminate anisokinetic sampling
bias. In principle, the EGR train will provide measurements of both PM^
and total particulate concentrations with accuracy comparable to Methods 5
or 17.
As indicated above, the EGR train uses two separately-controlled gas
flow paths to maintain the required flowrate for the initial sizing device
while varying the amount of gas extracted from the stack. These paths
converge in the EGR mixing nozzle, shown schematically in Figure 2. Stack
gas is extracted at the isokinetic at flowrate Qs through the sample portion
of the EGR mixing nozzle into the inertial sizing component of the sample
train. At this point the sample gas is mixed with an adjustable amount, Qr,
of filtered, dry recycle gas to bring the total flowrate in the sizing
796
-------
device to the amount calculated for PM, 0 operations. The nozzle has several
critical requirements. Since the nozzle must be compact enough to allow
entry through available sampling parts, the nozzle design must allow the two
gas streams to mix in the short distance between the nozzle tip and the
cyclone body. The mixing must not cause excessive particle deposition in
the nozzle, and the nozzle must not perturb the natural of the cyclone.
The nozzle design judged to best meet these requirements uses annular mixing
as shown in Figure 2. This nozzle allows entry through common four-inch
sampling ports. All tests to date indicate that particle deposition in the
EGR nozzle are lower than in nozzles of conventional design.
A block diagram of the EGR train is shown in Figure 3. After passing
the mixing nozzle, inertial sizing device, and instack sample filter, the
sample gas passes through the probe and condenser or impinger train and
into the EGR flow control module. As in conventional Method 5 control
modules, the gaa flowrate entering the control module is controlled by
coarse and fine control values (Vj and V,, , respectively) at the entrance of
the sealed pump. At the exit of the pump and absolute filter, the total
flow is measured using a laminar flow element (LFE). 'Hie gas stream is then
split into the recycle and sample flow lines. The sample flow is monitored
in the normal manner using a dry gas meter and a calibrated orifice. By
mass balance, in leak-free system this flowrate must (on a dry mass flow
basis) exactly equal the initial sample flow Qg extracted from the stack.
The recycle gas flowrate is measured using a second laminar flow element.
While it is not strictly necessary to measure Qr, it serves as a useful
quality control check on the overall gas metering system. The partitioning
between sample and recycle gas is controlled by valves and located
downstream of the total flow LFE. Valve V. was added to the system to
extend the range of control to higher recycle percentages by adding back
pressure to the sample flow line. The recycle gas line, along with the
sample and pitot lines, passes through the heated probe in which the
recirculated gas is reheated to the duct temperature. Power to the heater
is regulated by a proportional temperature controller using a thermocouple
reference sensor located on the surface of the recycle tube.
Operation of the EGR train is similar to standard Method 5 sampling.
The total dry gas flow Qr"H3s(1 ~BWS) i-s monitored by using the total flow
LFE and controlled using values Vj and V., . The sampling flow (defined as
the gas flowrate entering the nozzle) is monitored using the sample orifice
and dry gas meter in the normal manner of Method 5 sampling, and controlled
using the recycle valves (V^ and ) and the back pressure valve (V,. ).
Selection of traverse points and sample flowrate are done using standard
techniques. In practice, the total flow would first be set to its operating
value for the desired size cut, then the sample flowrate adjusted to be
isokinetic at the first traverse point. Changes in the recycle flow setting
alter the total flow only slightly, so that usually one or two iterations of
V3 and are needed at a new traverse point. V. needs to be adjusted only
rarely to insure that the maximum necessary recycle flow can be attained.
The only aspect that can be initially confusing to a trained Method 5
operator is that the sample flowrate is adjusted using the recycle valves
rather than the customary valves and .
Field Evaluation of PMj0 Methods
Both PM, techniques have been developed in an ordered sequence of
laboratory and field studies. Hie basic elements of the SIM-5 technique
were developed from a systematic study of sources and magnitudes of expected
errors in particulate sampling with existing equipment. The technique was
tested against isokinetic samplers and the EGR technique at three sites,
797
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after which the details o£ the protocol were refined based on field
experience. The method was documented in Federal Register format and tested
for precision using multiple train techniques at a fourth site. The EGR
concept was developed by D.B. Harris of the EPA, who constructed a research
sampling train without particle sizing equipment. This design was adapted
into a protype field sampling train which incorporated a cyclone PM^^ sizing
device. This train was evaluated in a wind tunnel source simulator and at
three field sites. Based on field experience, two upgraded EGR trains were
constructed, operating protocols were documented in Federal Register format,
operating and data reduction software was developed, and multiple-train test
conducted at a fourth site. The results of the field evaluations will be
summarized in this section.
The first tests of each technique were conducted at a 56MW coal-fired
utility boiler. The sampling location chosen was downstream of an
undersized electrostatic precipitator (ESP) which was no longer the primary
particulate control device. Particulate concentrations varied considerably
with boiler load, ranging from as low as 60 mg/dsm3 at low load (with 20
ng/dsm^ PMjQ) to 2000 mg/dsm3 at high load (with 400 mg/dsm^ PM ). In the
first test series the EGR train was compared to colocated Method 17 or
isokinetic cyclone samplers. In a later SIM-5 test at the same site, a
SIM-5 impactor train was compared with colocated Method 17 or isokinetic
impactor trains.
The second test was also conducted at a 250MW unit of a coal-fired
power plant with ESP particulate control. A duct site with considerable
velocity spread was chosen for the measurements. Simultaneous EGR and SIM-5
cyclone runs over a restricted traverse were compared with each other and
with single-point isokinetic impactors. Total and PM.. particulate
concentrations, respectively, averaged about 200 and 105 mg/dsm^.
The third tests of each technique were conducted at a 220MW coal-fired
utility boiler equipped with twin fabric filter particulate control devices.
At the baghouse inlet, simultaneous EGR and SIM-5 cyclone traverses were
compared with one another, and with SIM-5 impactor and Method "7 runs taken
during the same time period. Inlet particulate concentrations of 3600
mg/dsm^ total and 750 mg/dsm^ PM^Q were measured. At the baghouse outlet,
simultaneous SIM-5 impactors and Method 17 samplers were run. Low particu-
late concentrations (15 mg/dsm3 total, 3 mg/dsm3 were observed.
In each of these test series, an individual PMjg sampler was operated
simultaneously (and colocated when possible) with a reference sampling train
(Method 17, an isokinetic PM1^ sampler, or a sampler using the other PMjQ
method). At the fourth sitej dual PM10 samplers were colocated with duel
Method 17 samplers in order to obtain train precision data in addition to
comparison data. TTie site chosen was downstream of a gravel bed filter
particulate control device. In the first test series at this site, dual EGR
trains and dual Method 17 samplers were colocated in the sampling plane. In
the second test series, dual SIM-5 cyclone trains, dual Method 17 trains,
and a single EGR train were operated simultaneously at a single duct
location.
Comparison of Reference Measurements
The results of all field evaluations test are summarized in Table I.
For the sake of comparison, all differences and confidence intervals are
expressed as percentages of the mean value. Notation is also made in Table
I where the PMj sampler and the reference sampler were colocated or run
simultaneously.
798
-------
EGR and SIM-5 Precision Testa. At Site 4, colocated pairs of EGR and
SIM—5 measurements indicated excellent reproductability between the two
trains. In only one instance (SIM-5 PM^ concentrations) does the mean
difference in the measurements of two nominally identical trains exceed
2.5%. (This bias was found to be due to a systematic difference in cyclone
flow rate between the two trains). For both PM, Q trains, 95% confidence
intervals were on the order of ±5 percent. By this measure, the precision
of the PM. g trains was the same as that of the paired Method 17 trains
operated during these tests.
Total Mass Comparisons. Although the primary purpose of the EGR and
SIM5 techniques is to measure PM, „ concentrations, both techniques simulta-
neously provide a measure of total particulate mass as well. Method 17
reference samples were included since in many PM, 3 applications total mass
information is also desirable, and since recovery of total mass is an
overall indicator of PMj0 sampler operation. In principle, the EGR sampler
should provide total mass measurements identical to Method 17, since both
methods use isokinetic sampling and instack particulate filters. In fact,
at both Site 1 and Site 4 the EGR train measured less than Method 17 by a
small but significant amount. Mean differences ranging from 5 to 13 percent
were observed, in each case larger than the 95% confidence limits. The
reason for this small bias is not clear; however, since it does not exceed
15 percent at any site tested to date, we do not consider it an extreme
difficulty.
Unlike the EGR measurements, SIM-5 total mass measurements at Test
Sites 1, 3, and 4 were not significantly diferent from the paired total mass
measurements from Method 17 or other reference isokinetic sampling trains.
Since the SIM-5 technique is expected to be less accurate for total mass,
these results are encouraging. When total mass data using the two
techniques are compared, the results are mixed. At Site 2, the 9 percent
EGR - SIM-5 difference is marginally significant at the 95% confidence
level. At Site 3 and 4 the EGR and SIM-5 data are essentially the same.
PM10Comparisons. In order to assess the accuracy of EGR and SIM-5 for
PMj measurements, single-point, isokinetic particle sizing samplers must be
used as a reference. Barring artifacts due to the EGR mixing nozzle, EGR
PMj data should have accuracy equivalent to the reference devices. SIM-5
data should by design differ by no more than 20 percent for worst case
conditions, and by less than 10 percent for the size distributions at the
sites tested in this study. In fact, the PM, ^ values measured by the two
techniques at every site differ by over 10 percent but less than 20 percent.
At Sites 2 and 4, the EGR PM, Q value is about 15 percent less than the SIM-5
value. At Site 3, the EGR value is 11 percent greater than the SIM-5 value.
All three differences are significant at the 95 percent confidence level.
Comparisons with isokinetic impactor trains show differences on the same
order of magnitude. These differences, however, are not significant in
light of increased confidence limits for the measurements, which were not
generally simultaneous.
A significant difference in PMj^ concentrations may result from at
least two causes: A difference in sampling efficiency for sizes less than
lOum, or a difference in the actual D_, of the inertial sizing device. For
sampling trains which give comparable total mass concentrations, sampling
efficiency for the smaller size particles in the PM^Q fraction should also
be comparable. On this reasoning, the PMj difference between the paired
EGR and SIM-5 runs at Sites 2-4 may be taken primarily as a measure of any
difference in the of the two samplers. Any such differene is not
consistent in sign at the three test sites, and does not cause average PM,r
799
-------
differences to be greater than 16% at any site tested. In consideration of
the favorable precision results of each technique, we conclude that the EGR
and SIM-5 techniques may be expected to produce comparable PMjQ measurements
(within ±15 percent) at other similar emissions sources.
As mentioned above, comparisons of PM, between either of the PMj ^
techniques and isokinetic reference trains*such as cascade impactors are not
generally conclusive due to the effects of source variability on these
non-simultaneous measurements. As with the EGR/SIM-5 comparisons, the
direction of any difference in sampler cut is not consistant from site to
site, so no systematic difference can be demonstrated.
Summary and Conclusions
This paper presents the current status of two candidate PM methods
for stationary emissions sources. Both techniques have been evaluated and
ir.odifed where necessary during the course of an extensive laboratory and
field testing program. Both have been documented in the format of published
EPA methods. During the field trials described in this paper, each
technique was found to compare well with the other and with other isokinetic
reference sampling trains. While further laboratory and field development
of each technique is desirable, the underlying technical principles of both
appear to be sound, and both techniques show excellent promise for source
PMj q sampling.
References
1. A. D. Williamson, R. S. Martin, D. B. Harris, T. E. Ward, "Design and
characterization of an isokinetic sampling train for particle size
measurements using exhaust recirculation." Paper 84-56.5, 77th Annual
Meeting, Air Pollution Control Association, San Francisco, CA (1984).
2. A. D. Williamson, R. S. Martin, T. E. Ward, "Development of a source
PMj sampling train using emission gas recycle (EGR)". Paper 85-14.2,
78th Annual Meeting, Air Pollution Control Association, Detroit, MI
(1985).
3. W. E. Farthing, "Evaluation and recommendations of protocols for PMjr in
process streams: recommended methods." SoRI-EAS-83-1038, Southern
Research Institute, Birmingham, AL (1983), 72pp.
4. W. E. Farthing, "A Protocol for Size-Specific Emission Measurements"
Paper 84-14.3, 78th Annual Meeting, Air Pollution Control Association,
Detroit, MI (1985).
5. S. P. Belyaev, L. M. Levin, "Techniques for collection of representative
aerosol samples." J. Aerosol Sci. 5(4):325 (1974).
800
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Table I. Percentage Differences in Particulate Concentrations
Measured During Test Seriesa
Number of
Replications
PM
10
Total
Concentration
EGR Initial Test: Site 1
EGR Cyclone - Isokinetic Cyclone'3 4
EGR - Method 17b 8
-8.3±27%
9. 0+29%
-11.5+8.3%
SIM—5 Initial Test: Site 1
SIM-5 - Method 17b
SIM-5 - Isokinetic Impactors''
-1.8i 22%
-16+32%
-1 4. 0+65%
EGR/SIM—5 Comparison Test:
EGR Cyclone - SIM-5 Cyclone
EGR - Isokinetic Impactors
SIM-5 - Isokinetic Impactors
Site
b
5
5-6c
7-6°
-1 5. 5±6. 5%
-11+31%
3.8± 25%
-9.2±8.5%
1.3+38%
14±31%
EGR/SIM—5 Comparison Test: Site 3
EGR - SIM-5b
EGR - Impactor
SIM-5 - Impactor
SIM-5 Impactor - Method 17
Inlet
6
6-5'
6-5'
Outlet
6-71
11+9.8%
27±16%
1 6±16%
1.7+21%
-9.3+16%
-11±14%
-7.4+23%
EGR Precision Test: Site 4
EGR - Method 17b
EGR - EGR2b
-2.4=4.9%
-1 2. 9+4. 2%
-0.9±4. 3%
SIM-5 Precision Test: Site 4
SIM-5 - Method 17b
EGR - Method 17b
EGR - SIM—Sb
SIM-5, - SIM-5,b
-15.8±7. 8
6.6± 3.8
0.4±6.3%
-4.8± 1 . 7%
1.2=5.4%
a All differences and confidence intervals expressed as percentages of the
mean value. Confidence intervals represent 95% significant level,
b These comparisons were analyzed as pairs since the measurements were
simultaneous.
c Where two numbers of replications are given, the first number corresponds
to the first listed device and the second to the second device.
801
-------
1010
1650
J2430
1.5 2.0 3 4 5 6 7 8 910 20 30 40 SO BO
VELOCITY, m/sac 700^79
Figure 1. Velocity ratio, R, versus duct velocity to give aspiration coefficient of 1.2 (upper curvesJ
and 0.8 (lower curves') for JO pm panicles.
TOTAL GAS -
FLOW
— SAMPLE
INLET
RECYCLE INLET
Figure 2. Annular recycle gas mixing nozzles for EGR train using PM jq Cyclone /.
802
-------
EGR PROBE ASSEMBLY
PITOT TUBE
RECYCLE
LINE
¦T3
sampling
DEVICE
SAMPLE
INLET
RECYCLE FLOW IFE
I ABSOLUTE
I FILTEH
ICE CHEST
CONDENSER
TOTAL
FLOW LFE
EXHAUST
SAMPLE ORIFICE
SEALED PUMP
DRY GAS METER
Figure 3. Schematic of emission gas recycle (EGR) train.
-------
STUDIES OF MEASUREMENT METHODS FOR CHLORINE AND CHLORINE
DIOXIDE EMISSIONS FROM PULP BLEACH PLANT OPERATIONS
Robert P. Fisher,
Michael D. Marks, Steven W. Jett
National Council of the Paper Industry for
Air and Stream Improvement, Inc.
Southern Regional Center
Gainesville, Florida
Methods for determining chlorine and chlorine dioxide emissions from pulp
bleaching facilities are employed in control device efficiency studies and
in determining compliance with non-criteria pollutant regulations. The dual
pH potassium iodide impinger capture method was investigated in laboratory
and field studies of (1) the necessity for buffering the capture solutions
to avoid generating artificially high chlorine data, and (2) precision of
chlorine and chlorine dioxide determinations. A pH-optimized method was
developed and tested.
An instrumental method for continually measuring total oxidants or chlorine
and chlorine dioxide was developed via modification of a corrmercial electro-
chemical chlorine monitor. Comparison testing with the dual pH potassium
iodide method demonstrated the utility of the instrumental method for survey
purposes.
804
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STUDIES OF MEASUREMENT METHODS FOR CHLORINE AND CHLORINE
DIOXIDE EMISSIONS FROM PULP BLEACH PLANT OPERATIONS
Introduction
Non-criteria pollutant regulations are being established by state
regulatory agencies for the purpose of regulating ambient concentrations of
substances released to the atmosphere by industrial operations. These
substances are typically chemicals which are recognized as having adverse
health effects at higher concentrations, and are usually limited in workplace
atmospheres by regulation (Occupational Safety and Health Act Permissible
Exposure Levels - PELs) or by recommendation (American Conference of Govern-
mental Industrial Hygienists Threshold Limit Values - TLVs). The emerging
state regulations generally specify a maximum ambient concentration of a
regulated substance as a fraction of a workplace limit (e.g., 1/200 of the
TLV), and an affected facility is to employ mathematical source emission
modelling to calculate the maximum allowable quantity of that substance
which may be emitted.
,Because of their ability to produce respiratory tract and eye irrita-
tion , chlorine (Clp) and chlorine dioxide (CI0^) are assigned 8-hour TLVs
of 1 and 0.1 ppm, respectively. They are induced in many state non-criteria
pollutant regulations, and because of their use in the bleaching of pulp,
their atmospheric emissions are of concern to the pulp and paper industry.
The various pulp bleaching sequences involve several stages of bleaching
and extraction of solubilized organic material. Each stage typically
includes reaction with bleaching chemical or caustic extraction solution in
a retention tower, washing of the product pulp on a rotary vacuum drum
washer prior to subsequent operations, and removal of the filtrate via a
seal tank. The vents to the atmosphere from the towers, washer hoods, and
seal tanks, may or may not be fan driven, ducted together to common vents,
or ducted to gas-liquid scrubbers for emission control. Because chlorine
dioxide is always generated on-site, there is a C102 generator vent which
may be a source of emissions of Cl~ and C^, and wnich may or may not be
ducted to a gas-liquid scrubbing device for emission control.
The pulp and paper industry in the United States is in various stages
of reducing chlorine and chlorine dioxide atmospheric emissions. In those
circumstances where non-criteria pollutant regulations do not impose restric-
tions on Cl„ and C10„ release, emission control may be undertaken primarily
for workplace considerations, if necessary. This control may take the form
of reduction in vat residuals of aqueous C1^ and ClO^ (where this is pos-
sible), it may involve the use of tall vent stacks, or it may include
gas-liquid scrubbing. Scrubbers may utilize sodium hydroxide, cold water,^ 3
extraction-stage filtrate, weak wash, or aqueous sulfur dioxide solutions. '
NCASI is conducting a study of bleach plant emissions of Cl^ and ClO^,
in order to (a) document uncontrolled emission levels, (b) examine the
relationship of process operation variables to emission levels, and (c)
determine the effectiveness of in place control devices. This activity has
required the examination of methods for measuring chlorine and chlorine
dicxice emissions, and studies have been conducted on (a) the optimization
of a grab sampling, wet chemical method, ana (b) a continuous instrumental
monitoring method.
805
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Analysis Methods Development
Grab Sampling Method
Background. Gas phase chlorine and chlorine dioxide may be captured
in neutral potassium iodide solution in impingers in an extractive sampling
system. Because of the dependence of the reactivity of chlorine dioxide
with iodide upon solution pH, the post-sampling determination of iodine
formed at neutral and acidic pH permits the quantitative measurement of both
chlorine and chlorine dioxide:
Standard practice within the industry has been to use two impingers in
series, each containing 2 percent potassium iodide, to sample at a rate of
from 1 to 5 L/min, and to collect a sample over a period of from 5 to 30
minutes (using shorter sampling times if the color in the second impinger
turns from straw yellow to orange). After sampling, the contents of the
impingers are combined and titrated with 0.1 N sodium thiosulfate solution.
After the first endpoint, the solution is acidified with sulfuric acid
solution, and the titration is continued to the second endpoint. Algebraic
manipulation of equations (1) through (3) permits the calculation of gas
phase concentrations of C12 ana CI0^ on the basis of the neutral and total
acid titration equivalents.
Method Testing and Modification. Although reaction (2) above is for
calculation purposes regarded as the full extent of the reaction of C10~
with iodide at other than acidic pH values, there is a dependence of the
rate of reaction of chlorite with iodide on solution pH, such that at
slightly acidic pH values the reaction can proceed to an extent appreciable
enough to cause (1) deviation from the 5:1 (total acid:neutral) ratic of
equivalents of iodine expected upon titration of a capture solution obtained
from C10-, only, and (2) an erroneously high calculated concentration of
chlorine. Experiments were conducted to demonstrate this second point.
The sampling equipment described in the appendix was employed to sample
gaseous emissions from a chlorine dioxide bleaching tower vent. A manifold
was constructed from FEP and PFA Teflon which permitted the collection of
six gas samples simultaneously. Twenty mL of 2 percent unbuffered potassium
iodide (KI) solution were placed ir. each first impinger, and a gas sample
was drawn at ca. 500 mL/min through each impinger. The pH of the solutions
was measured electrometrically. Twelve samples (two sets) were taken,
representing a sampling time of from 5 seconds to 4 minutes. The solution
pK dropped from an initial value of 6.7 to 6.1, at 30 seconds, then returned
to ca. 6.6 at 4 minutes. This was taken as evidence that the pH of unbuf-
fered KI solution could drop during sampling to a level low enough to permit
the reaction of chlorite with iodide. This was confirmed in subsequent
testing.
A sample was withdrawn from a chlorine dioxide bleaching tower vent
into a 30 L Tedlar gas bag (Pollution Measurement Corporation, Oak Park,
IL). To determine that the chlorine and chlorine dioxide were stable with
time, analyses of the bee contents by the method of the appendix were
carried out. Over a period of one hour, the measured chlorine and chlorine
dioxide varied randomly with an average of 66 and 148 ppm, with standard
deviations of 12 and 40 ppm, respectively, for five measurements. Another
Neutral pH: C1 ^ + 21" ¦+ I-, + 2C1
cic2 + I" + 1/2 i2 + cio2~
Acid pH: C102" + 4H30+ + 41" 2I2 + 6H20 + CI
(1)
(2)
(3)
806
-------
sample was placed in a Tedlar bag, and using the method of the appendix with
1 minute sampling and potassium iodide solutions buffered with borate and
phosphate buffers, the data of Figure 1 were obtained. (The C1CL concentra-
tion remained constant as a function of pH, averaging 1490 ppm with a
standard deviation of 43 ppm, except for pH 4,3 and 5.3 tests, where the
CIO., concentration decreased.)
To test the hypothesis that the concentration of chlorine formed by
conversion of captured chlorite depends upon the initial concentration of
C10-, experiments were conducted in which a sampling manifold was fabricated
from FEP and PFA Teflor. which permitted collection of four samples simulta-
neously, employing trains as described in the appendix. Each impinger pair
contained two percent KI solution, buffered essentially as per the appendix
formula, but buffered at pH values of 6.4, 7.5, 8.5, and 9.5. Samples were
withdrawn from a chlorine dioxide bleaching tower vent over a period of time
such that normal variations in bleaching conditions produced variations in
chlorine and chlorine dioxide gaseous emission concentrations. The data of
Figure 2 were collected, and these data support the hypothesis.
On the basis of the information obtained in these experiments, it was
concluded that an iodide solution buffered at pH 7.5 would minimize the
formation of "phantom" chlorine due apparently to the reaction of chlorite
with iodide at low pH values, but would not cause losses in apparently valid
finite chlorine concentrations. Such losses appear at high pH values (e.g.,
greater than pH 8), and may be due to the reaction of icdine with base to
form hypoiodite.
An experiment was performed in which a Tedlar bag containing a gas
sample drawn from a chlorine dioxide bleaching tower vent was sampled via
the method of the appendix, using a manifold which permitted collection of
six simultaneous samples. The experiment was conducted with three sets of
impingers containing unbuffered 2 percent KI, and three sets containing pH
7.5 buffered 2 percent KI, and was repeated once to obtain 12 tests.
Results are indicated in Figure 3. The average concentrations of chlorine
and chlorine dioxide using the unbuffered system were 354 and 1400 ppm, with
standard deviations of 63 and 71 ppm, respectively. The average Cl„ and
ClOo concentrations employing buffered sampling were 228 and 1440 p(5m, with
standard deviations of 25 and 22 ppm, respectively.
A separate experiment was performed in which six samples were drawn
from a Tedlar bag containing a C10? bleaching tower gas sample. Using the
method of the appendix, including Buffering at pH 7.5, the average CIO2
concentration was 1110 ppm with a relative standard deviation of 1.0 percent,
and the average Cl„ concentration was 120 ppm, with a relative standard
deviation of 5.8 percent.
Instrumental Analysis Method
Background. Field testing employing the method of the appendix
indicated that several bleach plant sources were at some mills highly
variable in the concentrations of chlorine and chlorine dioxide emitted.
This prompted consideration of the use of continuous monitoring devices for
high concentrations (as opposed to workplace level concentrations) of
chlorine and chlorine dioxide. Of the several devices available corrmer-
cially, two were chosen for study. An Anacon (Anacon, Marlborough, MA)
electrochemical diffusion based workplace chlorine monitor was fitted by the
manufacturer with a Teflon barrier around the sensing electrode, which
caused the response to chlorine to be reduced such that high concentrations
of chlorine could be measured. (This was designated e 0 to 500 ppm probe by
807
-------
Anacon.) Laboratory testing of this instrument with gases analyzed by the
method of the appendix showed a linear response to chlorine from 0 to 500
ppm, but very low response to chlorine dioxide.
A Delta Model 964 (Delta/Xertex Corporation, Hauppauge, NY) diffusion
based electrochemical high concentration chlorine monitor was tested in the
laboratory for response to chlorine and chlorine dioxide. The data of
Figure 4 indicate that the response to Cl2 was linear tc ca. 400 ppm, and
the response to C1G„ was linear to ca. 250 ppm. Below 250 ppm, the response
ratio of C^iClOg was near 1:1.
The Delta Model 964 was tested for time of response to changes in
chlorine concentrations. The time response of the system to a pulse of 250
ppm chlorine of a duration of two minutes was satisfactory, as indicated in
Figure 5. However, a pulse of 750 ppm chlorine of 14 minute duration
produced an unusably long fall time, as indicated in Figure 6.
A modification was made to the Model S64, as diagrammed in Figure 7.
Teflon solenoids were configured so that source gas and potassium iodide-
scrubbed ambient air could be alternately provided to the Teflon chamber in
which the sensor was mounted. A cycle time of 2 minutes on source gas and 4
minutes on air proved satisfactory, as indicated in Figure 8.
In earlier studies of measurement methods for workplace atmosphere
chlorine and chlorine dioxide, NCASI determined that aqueous solutions of
sulfamic acid in midget impingers would trap chlorine, but would quantita-
tively pass chlorine dioxide, at concentrations in the 0.05 to 2 ppm range.
This prompted further modification of the Delta Model 964 system, as indi-
cated in Figure 9. By providing alternate pulses of source gas (CI, +
C1C„), air, source gas passed through sulfamic acid (CI0^ only), ana air,
the output indicated in general form in Figure 10 was obtained. Testing
with mixtures of gaseous Cl^ and C10~ produced the recovery results indicated
in Table I. c c
Upon testing with mixtures of chlorine and chlorine dioxide, neither of
the configurations of the modified Delta Model 964 systems yields data which
are accurate enough for ncn-criteria pollutant analysis reporting purposes.
The equipment has proven very useful, however, in continuous monitoring
during field studies of factors influencing Clg and ClO^ emission rates.
Ccnclusions
The buffered dual pK potassium iodide impinger capture method yields
good precision upon analysis of gaseous chlorine and chlorine dioxide
mixtures, and buffering at pH 7.5 appears to reduce the chance of obtaining
falsely high chlorine concentrations in the presence of high concentrations
of chlorine dioxide.
Instrumental methods for continuously measuring gaseous chlorine and
chlorine dioxide in bleach plant vents were studied, and modifications made
to one commercially available system permitted the observation of short term
concentration fluctuations in total Cl? and C10?. A further modification to
provide separate continual quantitation of CI- and CIO2 proved sufficiently
accurate for survey purposes.
808
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References
1. American Conference of Governmental Industrial Hygienists (ACGIH),
Documentation of the Threshold Limit Values, 4th ed., ACGIH, Cincinnati.
1980, pp 80-81.
Z. G. Y. Pan, J. J. Renard, and J. F. DeGraw, "Scrubbing Chlorine Dioxide
from Bleach Plant Waste Gases," Tappi Journal, 66 (7): p. 55 (1983).
3. N. Manley, "Control of Chlorine and Chlorine Dioxide Emissions,"
Proceedings of the 1985 NCASI Northeast Regional Meeting, Special
Report No. 85-01, NCASI, New York, pp 124-34 (1986).
4. "A Laboratory Investigation of Techniques for Instrumentslly Measuring
Chlorine and Chlorine Dioxide in the Pulp Bleaching Area Workplace,"
Technical Bulletin No. 412, NCASI, New York (1983).
5. "A Laboratory Evaluation of the Sulfamic Acid-Iodometric Method for
Determining Chlorine in Pulp Bleaching Area Workplace Atmospheres,"
Special Report No. 82-02, NCASI, New York (1982).
809
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Appendix - Method for Measuring Chlorine and
Chlorine Dioxide Gaseous Emissions
This method is based upon extractive sampling using midget impingers,
sampling at a low sampling rate, ca. 200 mL/min. Greater sampling rates may
be used with larger impingers.
The sampling train includes a sample probe and withdrawal line which is
an appropriate length, e.g., 3 m of 0.64 cm (0.25 in) od FEP Teflon tubing.
This is connected at one end via either Galtek (Chaska, MN) 0.64 cm unions
or short pieces of silicone tubing to a tapered stem 30 mL capacity midget
impinger with 0.64 cm od inlet and outlet tubulatures (Southern Scientific,
Micanopy, FL). Two identical impingers are connected in series behind the
first. The third impinger contains silica gel as a dessicant, and its
outlet tubulature is connected to the flow control/prime mover equipment.
Two methods may be employed for low flow rate sampling flow control.
One method utilizes a dessicant column and a critical orifice downstream of
the second impinger, followed by a vacuum pump capable of providing ca. 64
cm (25 in) of mercury vacuum. The orifice is calibrated prior to use, the
vacuum at which critical flow is achieved is noted, and in use the high
vacuum side of the orifice is always maintained at at least 13 cm (5 in) of
mercury vacuum greater than this value. The flow rate at the prcbe tip is
measured before and after sampling with a bubble tube flow meter, as impin-
gers or other restrictive devices upstream of the critical orifice will
cause the system flow rate to change from the value obtained during calibra-
tion with atmospheric pressure at the orifice inlet.
A second means of controlling flow during low flow rate sampling is to
utilize EPA Method 25 evacuated sampling tanks to draw the sample and, via
pre- and post-sampling pressure measurements, to measure its volume.
The first two impingers each contain 20 mL of potassium iodide (KI)
solution, buffered with potassium dihydrogen phosphate (KHLP0.) and sodium
hydroxide (NaOH), as follows:
Dissolve 20 g KI in ca. 900 mL deionized water
Add 50 mL of 1 M KbLPO,
Add 30 mL of 1 M NaOH
Measure pH of solution electrometrically and add 1 M NaOH to
bring pH to between 7.45 and 7.55
When sampling, measure the temperature and pressure in the vent being
sampled. Assuming critical orifice flow controls, activate the sample draw
equipment and measure the sampling flow rate at the probe tip with a bubble
tube flow meter. Insert the probe into the sample port ana start a stop-
watch. End the sampling (stop the watch) after 30 minutes, or after the
color in the second impinger turns from pale yellow to a deeper straw color.
After sampling, remove the probe from the vent, and with the probe tip
elevated above the impingers, add ca. 5 mL deionized water to the probe sc
that this drains into the first impinger. Combine the contents of the
impingers in a 100 mL beaker, and titrate with sodium thiosulfate solution
(0.100 N or less concentrated, depending upon the quantity of iodine being
titrated). Record the volume of titrant to the first endpoint (T^, mL).
Add 5 mL of 10 percent sulfuric acid solution, and continue the titration to
the second endpoint. Record the total volume of titrant required to go
through the first and to the second endpoint (T^, mL).
To calculate moles of chlorine and moles of chlorine dioxide captured
employ the formulas:
810
-------
EqI2N = (Tn)(10"3)(N)
EqI2A = (Ta)(10"3)(N)
C102 moles = 1/4 Eq^A - 1/4 EIjN
Cl2 moles = 1/8 (5 Eql^N - Eq^A),
where EqI„N and EqI?A are equivalents of iodine determined in the neutral
and (totaf) acid titrations, respectively, and N is the normality of the
sodium thiosulfate solution. Calculate gas phase concentrations of C1CL and
CIo employing standard EPA calculations. Assume gas phase water saturation
in most vents.
811
-------
TABLE I. GAS PHASE CI- AND CIO, MEASUREMENTS
LABORATORY MIXTURE ANALYSIS RESULTS
MODIFIED DELTA 964
True Concentration,
ppm
Recovery, Percent
CI 2
cio2
ci2
cio2
106
300
78
100
100
298
80
101
107
58
106
132
65
320
86
141
812
-------
0.2-
o 0-
-0.2-
~
a
~
~
1 a a
~
~
6 a
pH at BUFFERED 2% Kl
Figure 1 Effect of capture solution pH on observed chlorine
concentration.
~ 00-
X
O
e
z
200
100-
-> o
-200-
o
A
1—
6.3
~ SCT 1
XC?0j=«lOppm
+ SCT Z
xciOj¦ PPm
TS BS
pH BEFORE SAMPLING
O SET 3
XCIO^ 2974 ppn
9.5
A SET 4
XCIOj»2'42tppm
Figure 2 Effect of chlorine dioxide concentration on pH dependence
of observed chlorine concentration.
813
-------
« o.z
Kl 9UFT-£RE0 AT pH 7 5 Vi UNBUFFEBED K!
Y/A Ci02 l\\1 c'z
Figure 3 Effect of buffered vs. unbuffered capture solutions on
observed chlorine and chlorine dioxide concentrations.
RK)
pj 100
300
0
~
X
200
—I—
300
~
X
400
9O0
~Clz,ppffl XCl02,PPfT»
Figure 4 Response of Delta model 964 chlorine monitor to chlorine
and chlorine dioxide.
J 200
TEST GAS
\OELTA RESPONSE
TIMC. minutt*
Figure 5 Response of unmodified Delta 964 to a chlorine pulse
of short duration.
814
-------
300
E
ft
CJ ?fX)
too
TEST OAS
DCLTA RESPONSE
i 1 1 j-
12 16
TIME , minutit
1—«—r~
20 24
Figure 6 Response of unmodified Delta 964 to a chlorine pulse
of long duration.
10 rnrv*,n*MM£D
UWfff
GAS
TEfLON
30LEH010 (S|
TO DELTA
ELECTRONICS
A
TEFLON CHAFER WITH
OCLTA PftOtC
v*cuuy firscKvoin
V
PUMP
Figure 7 Modified Delta model 964 sample system.
o 200
"i n n rT\
kt
> I I
I I I
-J V. J v-/ \,m
I I
1 1 I »
-OCLTA RESPONSE
12 19
TfMC
24
Figure 8 Response of modified Delta model 964 to a chlorine pulse
of long duration.
815
-------
wxmci _
OAS
TO DfLTA
C lCCTnotticl
to PMoanumo)
Timer
^nurv;r afts
VACUUM RESCRVOtfl
TEFLON CHAMBER WITH
DELTA PROBE
SAKJFUTfO AOULOU9
SULFAMIC MID
Figure 9 Delta model 964 modified for chlorine and chlorine dioxide
speciation.
:,2»
:,z I
Cl2 *
ClO.
CIO.
CIO.
CIO.
Figure 10 Response of the modified Delta model 964 to a mixture of
chlorine and chlorine dioxide.
816
-------
LABORATORY AND FIELD EVALUATION OF A
MODIFIED EPA METHOD 5 TRAIN AND
ATOMIC ABSORPTION SPECTROMETRY FOR THE
MEASUREMENT OF CADMIUM IN STATIONARY
SOURCE STACK GASES
R. F. Moseman, D. B. Bath, J. R. McReynolds,
D. J. Holder, and A. L. Syk.es
Radian Corporation
T. E. Ward
U.S. Environmental Protection Agency
An initial laboratory and field evaluation study was done to
assess the usefulness of a Modified EPA Method 5 sampling train and
atomic absorption spectrometry for the measurement of cadmium in
stationary source Stack emissions. Field evaluations were performed at
a municipal solid waste incinerator. This industrial source is
currently being evaluated by EPA/QAQPS for cadmium emissions. Also,
this methodology is being developed for application, subject to
verification a at other sources of cadmium emissions at Or above the
method detection limit. A formulation of the methodology was tested
through the laboratory and field sampling validation phases to evaluate
precision and accuracy of the proposed method. Collocated,
quadruplicate flue gaa samples of 30 and 60 dscf in 1 and 2 hours
sampling time were collected to assure an adequate cadmium content, a
representative sample including volume of stack gas and duration of
sampling time, and production of data to validate the method in terms of
between-train precision. The overall accuracy and precision of the
analysis procedure were 89.2 percent and 1.7 percent, respectively. The
detection limit of the atomic absorption instrument was 0.03 ug/mL. The
method detection limit for a 30 to 60 dscf (0.85 to 1.7 dscm) stack gas
sample was found to be 0.05 to 0.025 ug Cd respectively per dscf (1.7 to
0.88 ug Cd per dscm). The percent coefficient of variation (precision)
of between-train cadmium concentrations averaged 13.52 for the six
sampling runs conducted. Separate analysis of the front half (probe and
filter) and back half (impingers) of each of the field samples revealed
that all of the cadmium was collected in the front half, based upon the
results that all the back half samples were below the detection limit.
Precision of the cadmium results was not affected by varying the sample
size from 30 to 60 dscf. Other source categories should be tested and
further laboratory work done to broaden the scope of the method.
817
-------
INTRODUCTION
The U.S. Environmental Protection Agency (EPA) ia currently
investigating cadmium emissions from stationary sources aa a
potentially hazardous air pollutant. In the event that EPA sokes a
determination to regulate cadmium emissions, appropriate methods of
sampling and analysis must be available to accurately quantify the
emission of cadmium in stack gases from stationary sources.
The Environmental Monitoring Systems Laboratory (EMSL) of EPA
located in Research Triangle Park, North Carolina is developing and
validating a methodology for sampling and analysis of cadmium emissions.
The purpose of this report is to present the results of a field and
laboratory study of cadmium emissions measurement methodology. The
objectives of the study vere as follows:
• Determine the applicability of a Modified EPA Method 5 train
and atomic absorption spectrometry for the measurement of
stationary aource stack gas cadmium.
• Evaluate the precision and accuracy of the proposed
laboratory analytical techniques. The techniques consisted
of sample preparation followed by analysis for cadmium using
atomic absorption spectrometry.
• Assure that the method has a detection limit sufficient to
measure expected cadmium in municipal solid waste
incinerator flue gas samples of 30 to 60 dry standard cubic
feet.
• Combine the results of these determinations to validate the
proposed sampling and analytical methodologies.
The method validation was conducted in several stages. The
initial effort focused on defining appropriate sampling and analytical
procedures. The procedures were then chosen and a laboratory study
was conducted to determine overall precision and accuracy of sample
preparation and analysis. The next stage of the program involved a
field evaluation conducted at a large municipal solid waste incinerator.
Other BOurce categories may be teBted and further laboratory studies
may be conducted to expand the scope of applicability of the methods to
include additional stationary sources.
EXPERIMENTAL METHODS
The sampling and analytical methods evaluated in this field and
laboratory study were proposed after a thorough literature search.
The various methods of sampling, sample preparation and analyses were
then compared according to method detection limit, sensitivity,
precision, speed, complexity, availability, cost, and overall
practicality. After considering these factors and reviewing the
literature, it was determined that sample collection using a very
Blightly modified EPA Method 5 (MM5) sampling train, followed by acid
digestion in a Parr bomb and atomic absorption spectrometry would be
used for the sampling and analysis of cadmium emissions from stationary
sources.
818
-------
The laboratory validation phaae of tbia work was designed to
assess the combined precision and accuracy of the portion of the
methodology used for sample preparation and analysis. A National Bureau
of Standards (NBS) urban particulate sample was analysed in tbia phase.
Samples were digested using a suture of nitric and hydrofluoric acids
in a Parr bomb, and analysed in quadruplicate using three different
methods (AAS, ICAP, and KAA).
A weighed amount of each particulate sample vaa digested along with
a glass fiber filter to provide a background matrix consistent with the
field samples. Following digestion, each sample was split for analysis
by atomic absorption spectroscopy (AAS) , neutron activation (NAA) and
inductively coupled argon plasma spectroscopy (ICAP). The latter two
analytical techniques were used to confirm the results obtained by AAS.
Filter blankB were prepared and analysed to demonstrate the absence of
cadmium in tbe glass fiber filter and acid reagents.
The field test was conducted at a municipal waste incinerator which
had previously been tested for cadmium emissions. Cadmium concentra-
tions reported during the previous testing ranged from 23 to
230 ug/dscm. The range of cadmium found in thiB study waG from 32 to
115 ug/dscm. The sampling method employed was a MH5 train which used
nitric acid in the first two impingers instead of water. Separate
analyses were performed on the front and back halves of the trains to
determine tbe collection efficiency of each half.
In order to assesB sampling and sample recovery precision, four
"identical" samples were collected simultaneously using a quad-probe.
Four simultaneous samples were collected twice each day over a
three-day period for a total of 24 samples. Sampling was conducted
isokinetically at 0.5 dscfm for all test runs.
Samples were collected for periods of roughly one or two hours to
yield total sample volumes ranging from 32 to 65 dry standard cubic
feet. The sample volumes were chosen to demonstrate that: 1) cadmium
emissions from a municipal incinerator could be measured in samples of
thiB size, and 2) tbe size of tbe sample volume would not affect the
analytical precision and accuracy of cadmium concentration results.
In order to recover all of tbe cadmium from the sampling train
components the front half probe rinse6 were combined with the glass
fiber filter for digestion and analysis. The impinger solutions and
back half rinses were combined and analyzed to determine if cadmium
were captured in the back half of the MH5 train.
RESULTS
Prior to any field sampling activities, the precision and accuracy
of the proposed analytical procedures were determined. The sample
preparation and AAS procedures used to analyze field sampleB for cadmium
bad an accuracy of 89.2 percent for analyzing known concentrations of
cadmium. The precision of these procedures was 1.7 percent.
The precision and accuracy are based on resultB aa determined by
Parr bomb digestion of four aliquots of a National Bureau of Standards
Standard Reference Material urban particulate sample and three
independent analysis techniques for the aliquots: AAS, ICAP spectro-
scopy, and NAA. Instrument detection limits for tbe three techniques
were 0.03, 0.03, and 0.12 ug/mL, respectively.
819
-------
The accuracy (Z recovery) anil precision (Z coefficient of
variation) for all three analytical Methods are given in Table 1.
Overall average percent recoveries for each analytical Method were as
follows: 89.21 for AAS, 99.3Z for ICAP, and 94.2Z for IAA. The mean
percent differences for the duplicates was 1.OZ for AAS, 6.2Z for 1CAP,
and 1.7Z for HAA. In terns of standard deviation, the values were 0.84,
A.49, 1.09 ug/g for AAS, ICAP, and RAA, respectively. The duplicate
means and the standard deviation are measures of precision for three
analytical methods and aerve as a basis for assessing the relative
precision of the analytical methods.
The field testing portion of this study was designed to evaluate
the precision of the sampling and sample recovery procedures, the
cadmium collection efficiency of the front and back halves of the
MH5 train, and the effect of the sample volume on cadmium measurement.
Table II presents the cadmium concentrations and precision
assessments for the quad-train field study. The between train pooled
standard deviation was 12.39 ug/dscm and represents the overall
precision for the field study. In terms of percent coefficient of
variation the pooled precision wa6 13.54Z which is a measure of the
precision of sampling and analysis.
The within—run or between-train precision shown in Table 11 is
assessed in terms of a standard deviation and percent coefficient of
variation. Contributions to these variables result from
(1) differences in the sampling trains, (2) variations between trains
in the sample preparation and recovery steps, and (3) analytical
variability. Between-test pooled variability includes all of the
above and: (1) the day-to-day variability of the cadmium concentration
in the feed, (2) effects of different plant operating conditions and
(3) the potential effect of within-run variability on the cadmium
collec tion.
A second variable which was addre66ed was the collection efficiency
of the sampling train. No cadmium was detected in the back half,
indicating that the front half (probe and filter) was very efficient
(>99.92 efficiency) in preventing breakthrough of cadmium.
A third variable evaluated in the data set of Table 11 is the
length of the sampling period for each run. Tests 2, 3, and 6 were each
conducted for roughly one hour while Runs 1, 4, and 5 were conducted for
about 2 hours. An analysis of variance confirmed that there was not a
significant difference in the variabilities of the cadmium
concentrations of the one-hour compared to the two-hour runs, at the 52
level of significance (95Z probability). Thu6, sampling times of about
one hour will yield concentration data equivalent to that for double the
sampling time.
Anomalies in the cadmium concentration data set are described here.
The average cadmium concentration level in Test No. 1 was much lower
than for Tests 2 through 6. The cadmium concentrations shown for
Te6ts 2 through 6 in Table II reflect a reasonably constant average
cadmium concentration in the stack gas. However, there is no reason to
suspect that the Teat No. 1 samples were collected any differently than
other test run samples. Therefore, these data were included in the data
analysis. The concentration difference between Run No. 1 and the other
runs is probably due to plant operating conditions.
820
-------
Also, Sample B in test number 6 shows an extremely high value in
terms of cadmium per dscm (Table 11). Table 111 shows a comparison of
cadmium in terms of gas volume sampled and the amount of cadmium per
gram of particulate. The source of high cadmium content of sample B,
test number 6 can be only conjecture and cannot be explained adequately
or factually. However the Dixon outlier test indicates that this value
is an outlier and, therefore, was not included in the statistical
analysis.
Table III shov6 a particulate value for Sample A in test number A
which is nearly seven times higher than other values of the data set. A
large amount of milky material vas noted in the two nitric acid
impingers, and the filter appeared brownish rather than white. It vac
observed during this entire field sampling exercise that on all newly
tape-wrapped probe liners a thickish fluid exuded from the probe
exterior wrapping tape upon heating the nichrome wire. Normally tbiB
fluid dripped harmlessly from the probe liner. Upon removal of the
probe for Sample A, test number 4, from the stack at the end of the
test, inapection of the glass probe liner revealed that it was broken by
having been cracked around its entire circumference. However, tbe glass
liner was still held in place by the tape which holds, also, the heating
wires in place around the glass liner. It is assumed here that the
fluid from this newly tape-wrapped probe liner was pulled into the
cracked probe and caused the milky impinger deposit, filter
discoloration, and excess particulate weight observed, while at the same
time due to it6 thickish quality sealing the probe sufficiently for an
adequate stack gas volumetric sample. Even though the particulate value
for this sample was very high, the concentration of cadmium appeared to
agree with the other three runB of tbe test and was therefore included
in the statistical analysis.
CONCLUSIONS
Several conclusions and recommendations have been made regarding
the proposed use of a slightly Modified EPA Method 5 (KM5) sampling
train and atomic absorption spectrometry for the measurement of stack
gas cadmium in stationary sources. These include:
1) An MM5 sampling train and atomic absorption spectrometry were
found to be applicable for the measurement of cadmium in
stationary stack gas samples.
2) Further field evaluations should be conducted to insure the
applicability of the HM5 train for stationary sources of
different stack gas cadmium concentrations.
3) Tbe overall accuracy and precision of the analytical steps
were 69.2 percent and 1.7 percent, respectively. The
detection limit of the analytical instrument was 0.03 ug
Cd/ml of prepared sample. A very limited cadmium concentra-
tion range was investigated. Tbe precision and accuracy
should be further investigated with different cadmium
concentrations.
4) The method detection limit for a 30 to 60 dscf (0.85 to
1.7 dscm) stack gas sample was 0.05 to 0.025 ug Cd/dscf (1.7
to 0.88 ug Cd/dscm).
821
-------
5) The percent coefficient of variation of between-train cadmium
concent rations ranged from 3.4 to 23.11 for the six sampling
runa conducted. The method biaa was not affected by total
sample volume. Stack gas samples of approximately 30 and
60 dscf vere collected, and the cadmium reaulta for the two
•ample sices did not differ significantly. Greater than
99.9 percent of the cadmium was collected in the front half of
the sampling train for each run. Future developmental testing
should include back half analysis to determine whether this
analysis is necessary.
6) If a purchased stock solution of cadmium is used for prepa-
ration of working standards, the concentration should be
verified against an independently prepared cadmium standard.
7) At least one sample from each source should be checked using
the method of additions to ascertain that the chemical
composition and physical properties of the sample do not
cause erroneous analytical results.
822
-------
Table I. ACCURACY AMD PRECISION OF CADMIUM IK MBS STANDARD
REFERENCE MATERIAL #1648, URBAN PARTICULATE*
Sample ID MS Afcurflf.y ICAP Accuracy KAA Accuracy
Number Individual Mean Individual Mean Individual Mean
X Recovery Z Recovery Z Recovery
A1
A2
97.4
97 .4
97.4
98.3
106.6
102.5
105.5
107 .4
106.5
B1
B2
84.0
85.4
84.7
107.5
101.5
104.5
92 .2
91.0
91.6
CI
C2
81.3
82.7
82.0
91.3
85.0
88.2
69.6
71.6
70.6
D1
D2
92.0
93.3
92.7
100.1
104.2
102.2
107.5
108.4
108.0
Mean Accuracy
89.2
99.3
94.2
Z Coefficient of
Variation,
Precision
1.7
7.8
17.1
Mean X:d
1.0
6.2
1.7
Std. Dev. of .
u G
Ramdom Error '
ug/g
0.84
4.49
1.09
*Based on an NBS cadmium value of 75 ug Cd per gran of particulate*
^Sample A was Parr bombed once. Samples B, C, and D were bombed tvice.
Q
AAS, Atomic Absorption Spectrophotometry; ICAP, Inductively Coupled Argon
Plasma; and NAA Neutron Activation Analysis.
**A measure of precision of duplicate determinations on four samples.
eTouden, W.J., and E.B. Steiner, "Statistical Manual of the Association of
Official Analytical Chemists, "AOAC, Arlington, Virginia 22209 (1975),
p. 18.
823
-------
Table II. CADMIUM CONCENTRATIONS AND WITHIN-BUN PRECISION ASSESSMENTS
(ug/dscm)
Percent
Coefficient
Sample Train Average Standard* of Variation,
Teat No. A B C D z Deviation Z CT
1
32.2
32.8
30.4
32.6
32.0
1.10
3.4
2
96.5
85.6
87.2
104 .1
93.4
8.63
9.2
3
105.5
115.5
73.5
74.9
92.4
21.36
23.1
4
76.2
88.0
101 .2
76.7
84.8
11.67
13.8
5
80.0
111 .5
103 .3
88.3
95-8
14.24
14.9
6
101 .4
328.0b
93.8
95.6
96.93
3.97
4.1
pooled
12.39d
13.54'
A
All sample train results reported in micrograms cadmium per dry Btandard
cubic meter, ug/dscm.
total volume of stack gas sampled (m )
^This value vai excluded from the data analysis, because when subjected
to a Dixon Outlier test for Test No. 6, it did not meet the acceptance
criterion of 126.1 ug/dscm, at the 5 percent level of significance
(i.e., 952 probability).
(J
The Dixon outlier test may be found in Dixon, Vilford J., and Frank J.
Massey, Jr., "Introduction to Statistical Analysis," McGraw-Hill Book
Company, New York (1057).
spooled ¦ /n B.^\
824
-------
Table III. CADMIUM CONCENTRATIONS, PARTICULATE CONCENTRATION,
RATIO 0? CADMIUM TO PARTICULATE CONCENTRATION,
AND ISOKINETIC RATES FOR EACH RUN*
Teat No.
1
Cadmium (mg/dscm) 0.0322 0.0328 0.0304 0.0326
Particulate (mg/dscm) b b b b
Cadmium to Particulate (mg/gram) b b b b
Isokinetic Value (Z) 102.2 104.1 102.6 107.6
Cadmium (mg/dscm) 0.0965 0.0856 0.087 2 0.1041
Particulate (mg/dscm) b b b b
Cadmium to Particulate (mg/gram) b b b b
Isokinetic Value (Z) 100.8 104.2 99.9 100.4
Cadmium (mg/dscm) 0.1055 0.1155 0.0735 0.0749
Particulate (mg/dacsO 38.769 38.782 49.482 36.050
Cadmium to Particulate (ng/gram) 2.72 2.98 1.48 2.08
Isokinetic Value (X) 102.8 100.0 103.5 101.0
Cadmium (mg/dscm)
Particulate (mg/dscm)
Cadmium to Particulate (ng/gram)
Isokinetic Value (Z)
0.0762
224.118c
c
101 .4
0.0850
34.254
2.48
101.2
0.1012
33 .767
3.00
103.1
0.0767
32.585
2.35
102.9
Cadmium (mg/dscm) 0 .0800 0.1115 0.1033 0 . 0 8 83
Particulate (mg/dscm) 40.730 44.209 37.192 34.542
Cadmium to Particulate (mg/gram) 1.96 2.52 2.78 2.56
Isokinetic Value (Z) 102.6 101.1 102.2 101.5
Cadmium (mg/dscm) 0.1014
Partculate (mg/dscm) 37 .872
Cadmium to Particulate (ing/gram) 2.68
Isokinetic Value (Z) 101.0
0.3280
38.933
8.42
100.0
0.0938
35.373
2.65
97.7
0.0956
32.424
2.95
101.2
*The particulate emission and cadmium-to-particulate ratio values
presented in this table are for information only. In any municipal
waste incineration process, significant variation might be expected
between tests for these values.
Particulate weight was not determined.
c ...
Not valid for particulate concentration or cadmium-to-particulate
ratio because of broken probe liner which resulted in excessive
particulate weight values.
^Not valid for cadmium, Dixon outler test.
825
-------
SAMPLING AND ANALYTICAL METHOD FOR MEASURIN6
METHYLENE CHLORIDE EMITTED FROM STATIONARY
SOURCES
A.L. Sykes,
M. Hart man, D. Byrd, and J.6. Homolya
Radian Corporation
Analytical Chemistry Department
Research Triangle Park, North Carolina
F.E, Butler, E.A. Coppedge
U. S, EPA
Environmental Monitoring Systems Laboratory
Research Triangle Park, North Carolina
Recent bioassays supported by the National Toxicology Program (NTP! have
demonstrated that methylene chloride is a carcinogen in laboratory animals,
and ether data indicate that it is a mutagen. Human studies have not,
however, proved to be conclusive for carcinogenicity. Therefore, EPA
initiated an investigation to determine risks to human health through
accurate measurement of the emission rates from various stationary sources.
This paper describes work performed to select an appropriate sampling and
analysis procedure for the investigation and evaluate its accuracy and
preci si on,
A laboratory evaluation of the proposed Method Has conducted followed by a
field test at a methylene chloride manufacturing facility. The analysis
technique chosen was gas chromatography with flame ionization detection.
In the laboratory evaluation Tedlar and 5-layer alusinized sampling bags
Here evaluated for methylene chloride stability. Methylene chloride Has
found to be much more stable in Tedlar than in the 5-layer aluminized bags
at part per million levels. The laboratory evaluation also determined the
method's precision to be +/-10 X, and the range to be from 1 ppm to 13 1,
In the field evaluation analytical accuracy of + /-10 X was determined by
analysis of certified standards and comparisons with independent audit
cylinders. This is also the best available estimate of overall method
accuracy since it was not possible to know the actual methylene chloride
concentration in the stack during the sampling period. Sampling precision
Has determined by sampling four ports simultaneously and comparing the
results of each run. Stability of field samples Has determined by
comparing on-site analyses to the lab analyses after 20 days.
Inter!abaratQry comparisons Here done between Radian and EPA/EMSL's
1 abor at ories.
826
-------
SAMPLING AND ANALYTICAL METHOD FOR MEASURING
METHYLENE CHLORIDE EMITTED FROM STATIONARY SOURCES
Introduct i on
Data provided in a recent National Toxicology Program (NTP) bioassay
demonstrate1 that methylene chloride is a carcinogen in two species of
laboratory animals, rats and nice, exposed at different dose levels via
inhalation. Mutagenicity data indicate that methylene chloride is a
mutagen with the potential of inducing gene nutations in exposed human
cells. EPA concluded that the available body of information on methylene
chloride provides sufficient evidence of carcinogenicity in anisals, but
the human epidemiological data are considered inconclusive. In the October
17, 19B5 Federal Register, EPA initiated regulatory investigation of
¦ethylene chloride to determine whether methylene chloride presents an
unreasonable risk to human health or the environment and to determine if
regulatory controls are needed. These findings created the need for a
sampling and analytical method to measure the amount of methylene chloride
emitted from stationary sources.
The method uses Tedlar gas sampling bags to collect the samples fron
the source and gas chromatography with flame ionization detection for the
analysis.2 Sample introduction to the gas chromatograph employs a gas
sampling valve or a gas-tight syringe. The chroeiatographic column used is
the EPA-recommended column for volatile organic analysis, Method 624.3
Certified methylene chloride standards in nitrogen were purchased in
cylinders to provide retention time and response vs concentration
calibration curves. Methylene chloride standards *ere also prepared in
Tedlar bags.
Concentrations of methylene chloride in stack gases from one part per
million to the per cent levels can be analyzed by this method. In the
laboratory Tedlar and 5-layer aluminized gas sampling bags Mere evaluated
for stability and water vapor effects at concentrations of 10 ppm to 13 per
cent methylene chloride. Field validation of the sampling and analytical
method was conducted at a methylene chloride manufacturing facility.
Experimental
The first objective of this work was to search the literature for
information on a sampling and analytical method suitable for a variety of
emission sources. The method of choice should detect low parts per million
through per cent levels of methylene chloride in emissions from
manufacturing and user facilities. The method should also be selective for
methylene chloride and allow samples to be collected easily with stability
sufficient for analysis within two weeks.
The second objective was to evaluate the selected method in the
laboratory prior to the field test. The laboratory evaluation began with
the preparation of standard curves in the ranges of interest; selection of
gas chromatographic conditions; determination of linearity; injection
precision; and the minimum detectable limit. Possible interferences from
other chlorinated hydrocarbons were also investigated.
827
-------
The third objective has to study stability in the laboratory at
various concentrations and evaluate Hater effects on the analysis. Also,
stability comparisons of Tedlar and 5-layer aluminized bags were completed,
as were bag blanking procedures.
The fourth objective Has to field test the proposed aethodology. A
pre-survey of a selected nethylene chloride manufacturing facility Has
conducted and grab saeples nere taken using Tedlar sampling bags. These
samples Here analyzed in the laboratory, compared nith expected results
obtained from engineering calculations, and used to screen for interfering
compounds. The pre-survey also established sampling locations, flow rates,
and site preparation needs for the field test.
The field test Mas designed to challenge the proposed saap1i ng and
analysis sethod. The samp 1es were taken using an aluminum manifold nith an
anemometer inserted to obtain flow data. On-site analyses Here done to
obtain immediate results. An independent assessment of analytical accuracy
Has aade by analyzing gas cylinders containing unknoHn concentrations of
¦ethylene chloride. These cylinders Mere provided by an EPA quality
assurance contractor.
The field samples Here then transported to Radian's and EPA's
laboratories fcr analysis. These results were compared nith the on-site
results. A sample Has also analyzed by gas chromatography/mass
spectrometry (GC^MS) to confirm the gas chromatography/f1ame ionization
detector (BC/FID) peak to be methylene chloride and to identify other
compounds detected.
Results and Discussion
Laboratory Evaluation
The literature search for sampling and analysis methods for methylene
chloride emissions suggested that the simplest and most appropriate
sampling technique should use gas sampling bags. The analytical technique
chosen Has gas chromatography nith flame ionization detection. EPA Method
19 uses this sampling and analysis technique for many organic compounds.
The suggested analytical column was ~V — 101, a methyl silicon liquid phase
on Chromosorb WHP. This column Has tried and found to separate methylene
chloride from methyl chloride, chloroform and carbon tetrachloride, but
required a 35*C oven temperature. This could present precision and
accuracy problems because some gas chromatographs do not maintain constant
oven temperatures at 35"C. An alternate column used in EPA Method 624, 1 X
SP — 1000 on Carbopack B, for volatile organic analysis Has tried and showed
excellent separation. Temperature programming the oven from 40"C to 200°C
at 10°/mi n reduced the analysis time to 15 min.
Both a gas sampling valve heated to 100°C and a gas-tight syringe were
used in the laboratory studies to inject samples into the GC. The
precision of injections Has comparable with each technique. Standards of
methylene chloride in nitrogen Here obtained from Scott Specialty Gases.
Precision of replicate injections averaged 1,0 1. Stability of a 102 ppm
standard over a 3-month period Has not significantly different from the 1.0
1 precision of injections. The linearity of the standard curve was very
good fro® 5 ppm to 25000 ppm (2.5 X). The per cent levels Here injected
directly nithout dilution. The minimum detection limit for this nethod is
estimated to be between 0.5 ppm and 1.0 ppm. This Has calculated by
extrapolation of the detector response from a 6 ppm audit cylinder, to an
expected response that Mould be at least 2 times the noise level.
Standards of methylene chloride with chloroform and carbon tetrachloride
828
-------
wire analyzed far possible interferences and none were found.
The proposed saapling technique Mas evaluated by studying the
stability of Methylene chloride standards in Tedlar bags. For comparison
purposes and as a possible alternative, 3-layer aluminized gas sanpling
bags nere obtained froa A11t»ch/App1itd Science, and also evaluated. The
five layers are i 1) inner layer of polyester, 2) polyaaide, 3) aluminum
foil barrier, 4) polyvinylidene chloride, 5) outer layer of polyethylene
terephthalate. The Tedlar bags were obtained from EPA. All bags were
initially purged three tines with dry nitrogen, then filled Nith nitrogen
and analyzed using the GC procedure. No detectable peaks were found, A
¦easured amount of Methylene chloride liquid Has vaporized and injected
into a stream of nitrogen flowing into each bag at a known rate. The
concentrations prepared Mere approximately 7.5 X, 10.0 7., and 13.0 X.
Dilutions of these per cent concentrations Mere made before analysis. The
ppm level bags Mere prepared by transferring the 102 ppia gas cylinder
standard into Tedlar and 5-layer aluminized bags. Each bag Mas well mixed
and analyzed throughout a 9 day period. The results shewed a per cent
decrease ranging from -1.8 X to -6.1 X for all bags studied. However, at
the ppm level there was a significant change in the 5-layer aluminized
bags. Within a 2 day period there was a 30 % decrease from 102 ppm to 72
ppm. Figure 1 illustrates that the Tedlar bags decreased only 5.5 X. The
instability of the S-layer al umi r.ized bags is thought to be due to
aethylene chloride peraeating the inner layer of polyester. The Tedlar and
5-layer aluminized bags were ther. evacuated and purged three times with
nitrogen after containing concentrations of 10000 ppm. The bags were then
immediately analyzed. The Tedlar bags produced no detectable peaks,
whereas the aluninized bags retained approximately 10 ppm after six
successive purgings. After considering these results, it was decided not
to continue evaluating the aluminized bags. A 10,5 pp o standard was
analyzed in the Tedlar bags for a period of 18 days. The results showed a
decrease of less than 1,0 X, which is not significantly different from the
analytical precision. Water effects within the bags were studied by
bubbling the cylinder standard of 102 ppm through water to produce a
humidified standard. A Tedlar bag was filled with the humidified standard
and analyzed. The results of the humidified bag was compared to the
results of the humidified standard analyzed without contacting the Tedlar.
There was not any significant difference between the two analyses, proving
that humidity does not affect the results.
FIELD EVALUATION
As discussed above, a field test was conducted to challenge the method
under real conditions. A manufacturing facility was selected that was
expected to have emissions of methylene chloride. An aluminum manifold (6
ft, x 4 in.) was placed in-line with a by-pass on a vent stream, prior to a
scrubber unit. The stream was allowed to equilibrate before the Tedlar
bags were connected to the four sanple ports. Four samples were taken
simultaneously to provide sampling precision data. EPA Method IS uses an
evacuated container sampling technique, in which the punp does not contact
the sample. The sample bag is placed in a sealed rigid container and the
sanpling line attached using quick-connect unions. "he container is
evacuated at a controlled flowrate, thus tilling the bag. Due to an
approximately 3 psig sample pressure, the evacuated container technique for
the bag sampling could not be performed, and the sample pump was not
needed. Instead, saaple flow into the bags was controlled by placing a
flow neter and needle valve between each bag and the sampling port. All
flows were adjusted to 0.5 L/#in. and aonitored every 5 ain during the 30
ain sampling period to obtain 15 liter of sample. The maximum capacity for
829
-------
each bag was 30 liter. Anemometer readings were also taken in order to
calculate the eaission rat* of the stream.
All of the samples were then analyzed on-site. Six tests Mere
conducted over a 3-day period on two different vent streams. Four tests
Mere done on one stream and two on the other. A blank and 3 points Mere
used to construct a calibration curve at the beginning and end of each day.
All samples Mere analyzed in duplicate and their averages used to calculate
precision between then. Far each test the standard deviation and per cent
coefficient of variation (X CV) were calculated. All six tests resulted in
a pooled X CV of 3.0, with a range of 2.3 to 8.3 X. The analytical
accuracy Mas determined by analyzing two unknown audit cylinders for
¦ethylene chloride. The results in Table 1 show a per cent accuracy of
-4 X.4
Nine of the 24 samples Here transported to Radian's laboratory and
randomly distributed and analyzed by Radian and EPA/EMSL. The
concentration of methylene chloride found in the field samples ranged from
7500 ppm (0.75 X) to 25000 ppm (2.5 X). The results in Table 11 show that
Radian's re-analysis varied by an average of -2.8 X from the on-site
results. EPA used the sane column and conditions as did Radian for one set
of analyses, and a second column for comparison. The first column's per
cent difference from Radian's on-site results was 0.5 X, and the second
column's results Mere -2.2 X. GC/MS results confirmed methylene chloride
in the field samples and identified the only other compounds to be
chloroform and carbon tetrachloride.
Conclusions and Recommendations
The laboratory and field evaluations have demonstrated that this proposed
method has an accuracy and precision of +/-10 per cent over the range of 1
ppm to 13 X. These evaluations show that methylene chloride emissions can
be sampled using Tedlar bags, and the analysis can be done up to 20 days
later without sample degradation. This work also shows that 5-layer
aluminized bags are not acceptable for methylene chloride sampling. It is
recommended that an additional field test be done to further challenge this
method at the low parts per million levels, and evaluate overall method
precision and accuracy.
Acknowledgments
Radian Corporation, Analytical Chemistry Dept., Research Triangle Park,
North Carolina, conducted work on this project under Contract No. 68-02-
4119 for the Duality Assurance Division, Environmental Monitoring Systems
Laboratory of the U.S. Environmental Protection Agency. Joette Steger,
Radian Corp., also contributed to the laboratory studies of this work. The
authors also would like to thank Denny E. Wagoner, Radian Corp., for his
helpful suggestions.
830
-------
References
1. Federal Register, 40 CFR Part 754; Vol. 50, No. 201;
Thursday Oct. 17,1905.
2. 40 CFR Ch.1(7-1-05 edition) Pt.60, App.A, EPA Method IS.
3. Federal Register, 40 CFR Part 136; Vol. 49, No. 209;
Friday Oct. 26 1984, EPA Method 624.
4. EPA Quality Assurance Handbook for Air Pollution Measurement Systems,
Vol 1 "Principles", EPA-600/9-76-005 Dec, 1984| and Vol III "Stationary
Source Specific Methods", EPA-600/4-77-027b, Aug. 1977.
831
-------
Table I. Percent Accuracy
% Accuracy
10.4 -4.0
6.0 - 3.5
Table II. Interlaboratory Comparisons
Test &
Percent Differences from On - Site Results
Sample Number
Radian1
EPA'
EPA1
1A
-0.6
4.6
0.6
1B
1.7
—
0.7
1D
-2.7
-6.3
-0.3
2C
—
-7.4
-2.6
4A
-2.8
1.7
-3.1
5A
-5.8
—
—
5B
—
0.9
-5.6
5C
-6.9
5.4
-3.1
5D
—
4.4
• 4.0
Column: 6 ft. X 1/8 In. 1% SP-1000 on Carbopack 9 60/80
Column: 9 ft. X1/8 In. 5% OV-101 on Chromoaorb WAP 60/100
Radian, ppm Actual, ppm
10.0
5.8
832
-------
100
• 5-LAYER ALUMINIZED
¦ TEDLAR
10
0.2
2.0
5
20
50
0.5
1.0
TlME.hr
Figure 1. Integrity of Sample Bags for Methylene Chloride.
833
-------
A SENSITIVE DIRECT MEASUREMENT N02 INSTRUMENT
H.I. Schiff,
G.I. Mackay, C. Castledine, G.W. Harris, Q. Tran
Unisearch Associates Inc.
222 Snidercroft Road
Concord, Ontario
Canada
The LUMINOX LMA-3 is a highly sensitive, lightweight, portable instrument
capable of continuously measuring nitrogen dioxide in air. It operates by
detecting the chemiluaiinescence produced when NO2 encounters a surface wetted
with a specially formulated solution containing luminol. Unlike other
chemiluminescent instruments it measures NOo directly and does not require
prior conversion of NO2 to NO. It does not respond to H2O2, NO, HNO3, NH3,
CO, C02, SO2 or organic nitro compounds at concentrations normally found in
air. The only interferences encountered to date are from PAN and O3 with the
response to O3 being less than C.2% of its response to NO2. The response
time is less than 1 sec and its sensitivity is 5 parts per tillion (pptv).
The chemiluminescent response is found to have a negative temperature
dependence of about 2% per degree which is being compensated electronically
in the instrument.
The instrument is rugged and simple to operate. It can operate continuously
on line power or at least 3 hrs on an internal, rechargeable battery. The
LMA—3 has been used successfully in field conditions to measure NO2 in both
polluted and relatively clean air. The measurements have compared
satisfactorily with measurements made with the unequivocal Tunable Diode
Laser Absorption Spectroscopic method.
834
-------
INTRODUCTION
The measurement of nitrogen dioxide, NO2 in air is of paramount
importance for a number of reasons. It is a major pollutant affecting both
indoor and outdoor air quality. Its presence in the atmosphere, whether from
natural or human sources, initiates atmospheric chemistry. NO2 is the only
gas in the troposphere which can be photodissoclated by sunlight to produce
ozone. The atmospheric chemistry resulting from its dissociation leads to
the oxidation of the reduced gases in the atmosphere including CO, CH4 and
NMHCs. For example, model calculations (1) have shown that the NO2
concentration has, by far, the most pronounced effect on the ozone budget and
its height profile in the atmosphere.
NO2 contributes directly to acid deposition by being converted to HNO3
mainly by reaction with OH radicals and by dry deposition. It also
contributes indirectly by affecting the oxidant level in the atmosphere which
converts S(IV) to S(VI).
Evaluation of models developed to attack the problems of photochemical
oxidation and acid deposition require accurate measurements of this important
species. Monitoring NO2 at the large number of sites needed for evaluation
of these models requires instrumentation which is inexpensive, sensitive,
reliable and easy to operate. This paper describes an instrument which meets
these requirements and also has sufficiently fast time response to be of
interest for dry deposition studies. In addition, its small size and
portability makes it highly suitable for indoor and outdoor air quality
monitoring.
Principle of Method
The instrument operates by detecting the chemiluminescence produced when
NO2 encounters a surface wetted with a specially formulated, alkaline,
luminol solution. Unlike other chemiluminescent instruments, it measures NO2
directly and does not require prior conversion to NO. Although many oxidizers
can produce luminescence with luminol most do so in the liquid phase and
require the presence of catalysts such as metal ions. In contrast,
chemilurainescence with NO2 appears to be a surface reaction not requiring the
presence of metal ions. Confining the reaction to a surface and using a
solution made with deionized water avoids interferences from most other
gases.
The method was first described by Maeda et al (2). The sampled air
passed over a pool of the luminol solution which was viewed with a
photomultiplier. The difficulty with this system i9 that the surface area is
not well defined and any splashing of the solution up the sides of the
reservoir results in changing sensitivity.
Stedman and coworkers (3) overcame this difficulty by flowing the
solution down a filter paper wetted with the solution, thus providing a
defined surface to be viewed by the photomultiplier.
We have made further modifications to produce a commercial instrument,
called Luminox LMA-3 and have investigated the parameters of the instrument
performance with a view of optimizing its sensitivity and freedom from
interferences. These parameters include the composition of the solution,
835
-------
its flow race over the surface and the flow rate of the sampled air. We have
also examined its temperature dependence.
Description of the Instrument
An operational block diagram of the instrument is shown in Figure L.
The sampled air is drawn through the instrument by a micro pump at a constant
flow rate of about 1.5 standard liters per min (SLM). The response of the
instrument Increases only slowly with flow rate above a rate of about 1 SUM.
The air passes along the 2 cm length of a cloth wick, wetted with the luminol
solution. The solution is continuously replenished at the top of the wick
and removed at the bottom by a small, two-stage, peristaltic pump.
The flow rate of the solution down the wick is about 0.05 ml sec""l. A
sealed bottle containing 250 ml of the solution located in the instrument
provides for 80 hrs of measurement. The used Liquid is pumped into another
250 ml bottle, also located in the instrument. If longer operation is
desired without replenishing the solution, provision is made for attaching
larger reservoirs external to the instrument.
Turning on the power to the instrument activates both the air and the
liquid pumps. The instrument operates on either 115 or 220 V AC power or for
a minimum of 3 hr from an internal 12 V 1.5 amp-hr gel cell. The battery
charges whenever the unit is plugged into the line current.
A photomultiplier views the wick and its signal provides a measure of
the NO2 mixing ratio. The signal is displayed on a LCD readout and the
analogue signal is also presented to BNC connectors at the front and the back
of the instrument for connection to either a chart recorder or to a data
acquisition system. Switches permit the LCD display to read the battery
voltage and the photomultiplier voltage. A potentiometer permits zeroing the
signal when no NO2 is presented to the instrument. This condition can be
achieved either by scrubbing the NO2 from the air stream, by using "zero" air
or simply by turning off the air pump. The instrument can be calibrated by
adding a known concentration of NO2 to the air stream (e.g. from a permeation
device). Based on this calibration the LCD readout can be made to correspond
to NO2 mixing ratios by adjusting the voltage to the photomultiplier by
another potentiometer.
The instrument is compact and lightweight, having dimensions of 38 x 20
x 22 cm and a weight of 7 kgm. It has been designed to be very rugged and to
prevent any leakage of the solution.
Composition of the Solution
The soLution contains luminol (3—aminophthalhydrazide) NaOH, Na2S03 and
alcohol, dissolved in carefully delonized water. The presence of Na2S03 in
the solution increases its response to NO2 while decreasing its response to
O3. The addition of one of a number of alcohols was found to enhance the
response to NO2 although we have recently discovered that it can also affect
the linearity of the response over an extended range of concentrations (see
below).
We have studied the effect of the concentration of each of these
conponents, on the response of the instrument to NO2 and to potential
-------
interfering gases. In general, the response towards NC>2 waa found to
increase with concentration of each component, reach a broad maximim and then
decrease. A selection was made for a formulation which appears to optimize
the sensitivity towards NO2 while minimizing its response to other gases,
particularly O3.
Interferences from Other Gases
Possible interferences were investigated when a number of gases was
added to laboratory air containing a few ppb of NO2. fto signal changes above
noise level were observed for additions of CO and CO2 at concentrations up to
1000 ppm, and for SC>2, NH3, N2O2 and RNO3 at concentrations below about
100 ppb. Addition of 80 ppb of NO reduced the signal from NO2 by about 5%.
The only positive interferences encountered were with O3 and PAN. For
the luminol solution selected the response of the instrument to O3 was 7 50
times less than to the same concentration of N02» For measurements of low
levels of NO2 in ambient air where the O3 concentration is more than 7 50
larger it may be necessary to preferentially scrub the O3 or to make the
appropriate correction to the reading.
The response of the instrument of PAN is still somewhat uncertain.
Stedman and his coworkers find similar responses to PAN which may be
dependent on the nature and concentration of the alcohol content of the
solution. The agreement with the NO2 measurements made with the instrument
and with the unequivocal tunable diode laser absorption spectroscopic (TDLAS)
method (4) under polluted conditions where the PAN concentrations were
expected to be high support the lower response to PAN. However, we intend to
do more definite work on this question.
Sensitivity and Response Time
The noise level of the signal, largely due to photomultiplier noise
corresponds to less than 5 pptv. This does not mean, however, that the
detection limit of the instrument is 5 pptv since ws have not demonstrated
that there are no interferences from other gases which can contribute to
signal corresponding to this amount of N02« The zero signal was found to
remain within this degree of variance for periods of at least one hour.
The response time of the instrument is demonstrated in Figure 2 when
22 ppbv of NO2 is suddenly added or removed from the ambient air. The
response time is less than 1 sec for a 20Z change in mixing ratio and less
than 10 sec for a 99% change in NO2 mixing ratio.
Linearity of the Instrument Response
Earlier work Indicated that the signal was proportional to the NO2
mixing ratio over the concentration range 6 to 100 ppbv. However,
simultaneous NO2 measurements made with the instrument and with the TDLAS
system during a field mission in the summer of 1985 suggested that this
linearity may not extend to concentrations below 6 ppbv. Figure 3 shows the
effect. Subsequent laboratory measurements at low concentrations confirmed
this behavior (Figure 4).
837
-------
The9e observations led us to reinvestigate the effect of the composition
of the luniinol solution. This work revealed that changing the choice and the
concentration of the alcohol removed most of this non-linearity. Figure 5
shows that the solution currently being used produces a nearly linear
response at low NO2 concentrations.
Temperature Dependence
The dependence of the NO2 response of the instrument to temperature was
studied over the range 5 to 45°C. The instrument was place in an
environmental chamber and allowed to equilibrate with the chamber temperature
for several hrs. At each temperature the response of the instrument was
measured at a number of NO? mixing ratios. Figure 6 shows the results
obtained from one such experiment.
The instrument shows a linear decrease with temperature in its response
to NO2 amounting to about 2% per deg. An electronic circuit is now being
designed to compensate for this temperature dependence. Each commercial
instrument will be compensated individually to allow for any small variations
from one instrument to another.
MEASUREMENT RESULTS
The instrument has been used to measure NO2 in urban and rural air and
in smog chamber experiments. On a number of occasions Intercornparisons wre
made of simultaneous measurements made with the instrument and the
unequivocal TDLAS system. Two examples of such comparison, one made in
Metropolitan Toronto, Ontario and the other in rural Ontario are shown in
Figures 7 and 8. They show that the Luminox instrument is capable of
following the diurnal variations of NO2 with good integrity. The agreement
is general within 10%. There is some suggestion in Figure 8 of the
non-linear response of the Luminox instrument at low concentrations,
resulting from the use of the earlier formulation of the solution. The
agreement between the two methods at higher concentrations suggest little
interference from PAN which may, of course, be due either to the lower
response of the instrument to PAN or to PAN being present in mixing ratios
ten times less than NO2.
Figure 9 shows one hour average intercornparisons between the two methods
made at Claremont, California for a one week period in September 1985. Again
the Luminox instrument appears to track the NO2 variations faithfully. It
is, however, interesting to note that just before midnight on September 12th
and 13th, very high readings were obtained by both methods, but with the
Luminox values being about 35% higher than those from the TDLAS system.
Since this discrepancy does not appear for other periods of high NO2 mixing
ratios it is possible that the Luminox instrument might have responded to
some other species, which may have been abnormally high during these two
nights.
CONCLUSIONS
Chemiluminescence with lurainol provides a direct method for measuring
NO2 in ambient air with no necessity to convert the gas to NO as in other
chemiluminescent methods. The commercial Luminox LMA-3, based on this
method, is light-weight, rugged and portable and is very simple to operate.
838
-------
It has a sensitivity of better than 5 pptv and a response time less than
1 sec. A formulation for the solution has been found which minimizes
interferences from other gases, optimizes the sensitivity and provides
near-linear response to NO2 over a considerable range.
No interferences were found from H2O2, NO) HNOj, NH3, CO, CO21 SO2 or
organic nitro compounds at concentrations normally found in air.
Interferences with O3 have been reduced to less than 0.2% of the equivalent
concentration of NO2 by suitable composition of the solution. The
interference from PAN is still under investigation.
The instrument response was found to have a negative temperature
dependence of about 2% per deg and a circuit is being designed to compensate
for this effect electronically.
The instrument appears to be well suited for indoor and outdoor
monitoring of NO2 in ambient air. Its size, weight and price makes it
attractive for network monitoring of this species.
REFERENCES
1. J. Fishman, F.M. Vukovich, E.V. Browell, "The photochemistry of
synoptic-scale ozone synthesis: Implications for the global
tropospheric ozone budget", J. Atmos. Chem. 3; 299, (1985).
2. Y. Maeda, K. Aoki, M. Munemori, "Chemi.luminescence method for the
determination of nitrogen dioxide" Anal. Chem., 52: 307, (1980).
3. G.J. Wendell, D.H. Stedman, C.A. Cantrell, "Luminol based nitrogen
dioxide detection" Anal. Chem., 55: 937 (1983).
4. D.R. Hastie, G.I. Mackay, T. Iguchi, B.A. Ridley, H.I. Schiff, "Tunable
diode laser systems for measuring trace gases in tropospheric air"
Environ. Sci & Technol., 17 352A (1983).
839
-------
Feed
Reservoir
\
Reaction
Photo
1 Bl
Cell
Multiplier
/
Electronics
and Display
Waste
Reservoir
Pump
Air in
Detart
Liquid in
Liquid out
A;r out
Figure 1 Block diagram of the instrument-
ADDITIONAL
N02 ADDED
Imin
ADDITIONAL
NO2 REMOVED
AMBIENT NO£
+ 22 ppb
"
AMBIENT N02
TIME
Figure 2 Response of the instrument as a function of time.
840
-------
eo
TOLAS /(FPBV)
Figure 3 Correlation between N0„ measurements made with the Luminox
instrument and the TDLAS system. Each point represents means of
all data acquired simultaneously during the period June 21-29,
1985 at Cold Creek, Ontario. The averages were taken: over
0.5 ppb intervals from 1 to 10 ppb; 5 ppb intervals between 10 and
50 ppb and 10 ppb intervals above 50 ppb.
60
50
4-0
20 -
0
20
4-0
60
CALCULATED N02 (ppbv)
Figure 4 Laboratory test of response of the instrument as a function of NC^
mixing ratio based on a permeation tube and a dynamic double
dilution system. Measurements made with original solution
formulation.
-------
J
5
1
J
0 1 C 20 jo +C
[NO?] ppbv
Figure 5 Similar to Figure 4 but using new solution formulation.
o
a
in
LU
ce
90
80
70
60 -
50 -
40
JO
20 -
I 0
1 0
30
TEMPERATURE C
- i—
40
Figure 6 Response of the instrument as a function of temperature for a
number of different NO- mixing ratios.
(~) 52.8 ppb (+) 41.0 ppb 20.1 ppb
(¦&) 10.1 ppb (x) 8.0 ppb 3.9 ppb
842
-------
[N02]
60 r
50 -
40 s
30 ¦
20 ¦
10 -
0
igure
7 C
i
M
ao
70 -
60 -
50 -
40 -
30 -
Q.
20 -
1 0 -
o
0 -
&
QC
1 0 -
(J
z
20 -
X
2
30 -
40 -
50 -
6: -
70 -
SO -¦
N02 Ambient Air Monitoring
Methods Intercomparison
Luminox LMA-3
Tunable Diode Laser
Absorption Spectrometer (TOLAS)
X
1
J
8 10 12 14 16
Time of Day (Hours)
Figure 8
TIME (EDT)
Comparison between 30 rain average measurements made by the Luminox
instrument (+) and the TDLAS system (~) at Cold Creek Ontario,
June 21, 1985.
843
-------
200
150
100 -
50
50 -
100
150
200
Figure 9
f
i
j •
\ LUmINOL
T" 1 • —"1 T ' 1 1
1 1
13
15
1 7
1 9
DATE
Comparison between 1 hr averages made simultaneously by the
Luminox instrument and the TDLAS system at Claremont, CA during
September 1985.
844
-------
DIRECT AMBIENT NITROGEN DIOXIDE MEASUREMENT
BY VISIBLE LIGHT ABSORPTION
John Jung
John Kowalski
California Air Resources Board
Haagen-Smit Laboratory Division
9528 Tel star Avenue
El Monte, CA 91731
A prototype photometric nitrogen dioxide (NO2) analyzer, constructed by
modifying a commercial photometric ozone analyzer, is being evaluated for
atmospheric NO2 measurement. The analyzer operates on the principle of
visible light absorption by the N02- The zero drift for 5 days and noise
for one hour are less than 3 parts per billion (ppb). Interferences from
ammonia, nitric oxide (NO), ozone (O3), peroxyacetyl nitrate (PAN), and
sulfur dioxide are negligible. The responses of the photometric analyzer
and a conmercial chemiluminescent oxides of nitrogen analyzer were compared
by devising a smog chamber experiment duplicating the NO2 reaction in the
atmosphere. During the experiment, the response of the photometric analyzer
exhibited a rapid decrease of the NO2 concentration after the NO2 formation
peaked, while the response of the chemiluminescent analyzer exhibited a
more gradual decrease probably caused by the positive interference of
nitrates such as PAN. The photometric analyzer is also being field tested
at the South Coast Air Quality Management District's air monitoring station
in Pomona. During August, 1985, the daily NO2 averages of the photometric
analyzer varied from 33 ppb to 78 ppb, while the averages of a parallel
chemi1uminescent analyzer varied from 32 ppb to 97 ppb. Generally, the
daily average of the photometric analyzer is equal to or lower than that
of the chemiluminescent analyzer. The maximum difference of 25 ppb
occurred on August 24, when the photometric analyzer read 65 ppb while the
chemi1uminescent analyzer read 90 ppb.
845
-------
INTRODUCTION
Air quality standards have been established for NO2 by the Environ-
mental Protection Agency (EPA) because health problems can occur from
breathing low concentrations of NO2 in ambient air. The present national
air quality standard for NO2 is 100 ug/m3 (53.2 ppb) averaged over one
year. The present California NO2 standard is 470 yg/m3 (250 ppb) averaged
over one hour. NO2 also plays an important role in visibility, photo-
chemical smog production, and acid deposition chemistry.
Chemi1uminescence is the most common technique of measuring ambient
levels of NO2- However, this technique measures NO2 indirectly in terms
of NO. The NO2 is reduced by a converter to NO which reacts with excess
O3 to give gas phase chemi1uminescence. In the conversion of N02-to-N0,
other nitrogenous compounds such as PAN also produce NO causing a positive
response in the chemi1uminescent NO2 analyzer. This has teen documented
by Wi ner (1).
To overcome the interference problem and to determine atmospheric 1NO2
concentrations directly and continuously, a prototype photometric NO2
analyzer was developed using a differential spectral absorption technique.
This absorption occurs during the conversion of radiant energy into other
forms, such as dissociation, fluorescence, and radiationless transitions,
while the radiant energy is passing through or being reflected from the
material. Hall and BlacetU] have plotted the NO2 absorption spectrum
in the range of 240-500 nanometers (nm).
DESCRIPTION
The prototype photometric NO2 analyzer is a modified Dasibi Model
1008-AH photometric ozone analyzer with a microcomputer. To modify the 0s
analyzer to measure N02, the lamp source, optical filter, mirrors, detector,
and absorption cell pathlength had to be changed, because the NO2 analyzer
operates at a different portion of the spectrum than the O3 analyzer:
their absorption coefficients differ. The detector area of the modified
analyzer had to be made lightproof to prevent the detector from being
exposed to stray visible light that would interfere with the NO2 measurement.
Figure 1 shows a diagram of the pneumatic, optical, and electronic sub-
systems. The sample, regulated by a valved flowmeter and drawn in by a
vaccum pump,flows into the absorption cell where the NO2 is measured before
the sample is vented.
Light passing through the absorption cell is attenuated in proportion
to the concentration of the NO2 moleucles in the sample according to Beer's
law. The light is detected, and the resultant signal is digi tal ly processed
for presentation by the readout system.
The absorption cell of the NO2 analyzer consists of a pair of Kynar-
coated aluminum tubes (1 cm diameter), a 400 nm long wave pass filter
(Schott GG-400), a quartz window, and two front-surfaced mirrors mounted in
the triangular block. Initially, the 71 cm pathlength cell was used for
the linearity and interference tests. Presently, a 1.12 meter cell which
increases the sensitivity is being used for the field testing in Pomona.
The light source is a 406 nm lamp (BHK Model 80-1025-01/406) with a 35 nm
bandwidth. This is a low pressure mercury lamp whose interior glass
envelope is phosphor-coated. This phosphor absorbs and converts the short
wave ultraviolet light (254 nm) produced by the excited mercury vapor to
848
-------
visible light which peaks at 406 nm. The 400 rim filter is used to reject
the ultraviolet light below 400 nm which may produce N02 dissociation.
The detector is a head-on vacuum type phototube (Hamamatsu R645) which
measures the amount of light passing through the absorption cell.
The ambient air sample entering the inlet passes through a 0.5 micron
porosity Teflon inlet filter which remove large particulates. The sample
flow is either 2 liters per minute with the 71 cm cell or 3 liters per
minute with the 1.12 m cell. A three-way solenoid valve directs sample
to the NO2 scrubber (Dasibi ozone scrubber) which removes NO2 from the
sample. After the cell is flushed for 4 seconds, the detector measures
in terms of current the amount of visible light passing through the cell.
The current is converted by the digital electrometer to a pulse rate
(frequency) directly proportional to the light intensity. The pulse from
the electrometer is totalized by the six-digit counter for 1.5 seconds.
The data from the counter is entered in the microcomputer as the reference
measurement.
After the reference measurement, the solenoid valve directs an
unscrubbed air sample containing the NO2 through the absorption cell for
the sample measurement.
The microcomputer is programmed to use Beer's absorption 1 aw, corrected
for temperature and pressure, to calculate the NO2 concentration. The
absorption coefficient value which is required for the calculation is
entered on the 3-digit thumbwheel switch. Since the microcomputer software
is programmed for a 71 cm pathlength, the absorption coefficient of NO2
is entered on the thumbwheel switch. When the 1.12 m pathlength is used,
the thumbwheel switch has to be readjusted to account for the longer path-
length. The actual value is empirically derived by gas phase titration
(GPT). GPT produces a known concentration of NO2 by mixing O3 and excess
NO. The values derived for the 71 cm and 1.12 m pathlengths are 138 and
240, respectively.
The microcomputer calculates the NO2 concentration, sending the results
to the digital display. The analyzer's digital-to-analog converter reads
the three least significant digits of the six digits calculation and
produces an analog output signal for the continuous recorder.
The air sample pump is placed outside of the analyzer to minimize
any noise created by the electromagnetic interference (EMI).
LINEARITY AND INTERFERENCE TESTS
The response of the photometric NO2 analyzer with a 71 cm absorption
cell was compared against the response of the cherni luminescent NO2
analyzer in a linearity test. The chemi1uminescent analyzer used in this
test was a Monitor Labs Model 8440 Oxides of Nitrogen Analyzer (ML).
The ML was calibrated according to the EPA procedure (40 CFR 50.1,
Appendix F, July 1, 1977) using GPT. After the ML calibration, the
photometric N02 analyzer was spanned with a high concentration of 1NO2
using GPT and checked against the calibrated ML. A multipoint calibration
using GPT was performed. Figure 2 shows the linearity of the photometric
analyzer: the zero offset of the photometric analyzer is probably caused
by the EMI from the solenoid valve and vacuum pump.
847
-------
The interference tests for anmonia, NO, and sulfur dioxide were per-
formed in the 1100 cu. ft. reaction chamber af the California Air Resources
Board. This chamber is made of square glass panes (2 ft. x 2 ft.) which
have aluminum supports. Ultraviolet lamps mounted within the chamber are
used to simulate the solar radiation. The chamber is flushed with the
treated ambient air from an air purification system, which removes non-
methane hydrocarbons, O3, and N02, but not NO and methane. With treated
air inside chamber and the ultraviolet lights off, a measured volume of
gaseous anmonia, NO, and sulfur dioxide was injected into the chamber using
nitrogen as carrier. Knowing the chamber and the injected gas volumes, the
concentration was calculated in ppb.
For the O3 interference test, a Monitor Lab Audit Calibrator with an
internal O3 generator was used to produce various concentrations of O3.
The photometric NO2 analyzer and a Dasibi Model 1003-AH O3 Analyzer were
connected to the calibrator. The O3 analyzer was used to verify the O3
concentration.
For the PAN interference tests, a synthetic mixture of PAN was
produced in a 20 liter Tedlar bag. The contents of the bag were verified
by gas chromatography, before the bag was connected to the photometric
analyzer to check for PAN interference.
The interference test results (Table I) indicate that at the test
concentrations the photometric analyzer does not respond to ammonia, NO,
O3, sulfur dioxide, or PAN. The maximum concentrations used in tests of
airmonia, NO, O3, and sulfur dioxide were 1000 ppb, and the maximum concen-
tration of PAN was 250 ppb.
After these tests, a photochemical smog experiment was performed using
the reaction chamber to compare the NO2 responses of the photometric and
chemi1uminescent analyzers. In addition to the two NO2 analyzers, other
analyzers used in this experiment to monitor the photochemical activity
were a Dasibi Model 1003-AH O3 Analyzer and a Byron Model 401 Hydrocarbon
Analyzer. At the start of the photochemical experiment with treated air in
the chamber, propylene and NO were injected in the chamber using nitrogen
as the carrier. The propylene was measured as non-methane hydrocarbon
(NMHC) in parts per million carbon (ppmC). The initial values of NMHC and
NO were 5 ppmC and 0.5 parts per million (ppm), respectively. Figure 3
exhibits the concentrations of the pollutants with time after the lamps
were activated. The responses of the photometric NO? analyzer and ML coin-
cided until the NO2 formation peaked. After the peaK was reached, the
response of the photometric analyzer exhibited a rapid decrease in the NO2
concentration while the response of the chemiluminescent analyzer exhibited
a more gradual decrease probably caused by the positive interferences of
nitrates such as PAN.
AMBIENT NITROGEN DIOXIDE MEASUREMENT AT POMONA AIR MONITORING STATION
After these tests, the photometric NO2 analyzer with the 1.12 m path-
length was installed at the South Coast Air Quality Management District's
(SCAQMD) air monitoring station at Pomona to obtain ambient data. The air
monitoring station has a chemiluminescent N0-N02 analyzer, Thermo Electron
Model 14B/E Oxides of Nitrogen Analyzer (TEC0). The SCAQMD calibrated the
photometric N02 analyzer and the TEC0 using GPT.
Table II lists the calibrations performed on 5 consecutive days during
the week of July 22, 1985. Tne SCAQMD calibrator at the Pomona station was
used to test for zero drift and response of the photometric analyzer. The
zero drift fluctuated ±2 ppb.
848
-------
To determine the photometric NO2 analyzer background noise, the
analyzer was configured to sample N02~free (zero) air. Twenty-five measure-
ments were taken at 2 minute intervals. Noise was determined as the
standard deviation about the mean of the zero air measurements. The calcu-
lated noise was less than 3 ppb.
Tables III and IV summarize the NO2 measurements of the chemilumini-
nescent and photometric analyzers, respectively, for August 1985. The
concentrations are in parts per hundred million (pphm) averaged over one
hour, rounded-off to the nearest pphm (one pphm = 10 ppb). The daily NO2
average is averaged over a 24 hour period, from midnight to midnight of the
following day. Figure 4 shows the differences between the chemiluminescent
and the photometric measurements. During the first half of August, the
photochemical activity was low, and the daily averages of the two were
within -0.7 pphm. During the latter half of August, the photochemical
activity was high, and the photometric NO2 daily averages had the lower
readings. The maximum difference of 25 ppb occurred on the 25th, when the
photometric analyzer read 65 ppb while the chemi1uminescent analyzer read
90 ppb.
CONCLUSION
A prototype photometric NO2 analyzer has been constructed and is being
tested. The NO2 analyzer is a modified photometric O3 analyzer with a
different optical system. The response of the NO2 analyzer is linear, and
the noise and zero drift are less than 3 ppb. Interferences from ammonia,
NO, O3, sulfur dioxide, and PAN are negligible. The photometric NO2
analyzer is performing satisfactorily in the monitoring of NO2 at Pomona.
More tests are needed to assess its freedom from interferences and
long-term stability.
ACKNOWLEDGMENT
The authors wish to acknowledge the technical assistance of Dasibi
Corp., the assistance of Battelle with the PAN interference tests, and the
cooperation of SCAQMD in using the instruments at the Pomona air monitoring
station.
REFERENCES
1. A. M. Winer, J. W. Peters, J. P. Smith and J. N. Pitts, Jr.,
"Response of the Commercial Chemi1uminescent NO-NO2 Analyzers to Other
Nitrogen-Containing Compounds," Environmental Science and Technology,
Vol. 8, pp. 1118-1121, 13 December 1974.
2. T. C. Hall, Jr. and F. E. Blacet, "Separation of the Absorption Spectra
of NO2 and N2O4 in the Range of 2400 - 5000A," Journal of Chemical
Physics, Vol. 20, pp. 1745-1749 (1954).
DISCLAIMER
This report has been reviewed by the staff of the California Air
Resources Board and approved for publication. Approval does not signify
that the contents necessarily reflect the views and policies of the ARB,
nor does mention of trade names or commercial products consitute endorse-
ment or recommendation for use.
849
-------
TABLE I. Response of the Photometric Nitrogen Dioxide Analyzer
to Various Gases
Range of No. of Response,
Compound Concentration, ppb Experiments ppb
Ammonia 1000 2 <3
Nitric Oxide 100-1000 10 <3
Ozone 100-1000 10 <3
PAN 50-250 5 <3
Sulfur Dioxide 100-1000 5 <3
TABLE II. Daily Calibration;:
Day in
July, 1985
Zero Level,
ppb
10 + £
10 + 2
10 + 2
10 + 2
N0Z Response
Ppb
376 + 2
374 2
373 + 2
8 + 1
170 +
850
-------
TRBLE III. HCkJRLV AND DAILY SUMMARY REPORT
Pollutant Observed: Nitrogen Dioxide Method af Analysis: Chemiluminescence
Samp!inq Interval ; 1 Hour Reporting Units : part per hundred million
Month: fluqust Year:1985
CI UCK T1MF (Standard Time> ! DAILY
day; oo
01
02
03
04
05
06
07
08
09
10
1 1
12
13
14
15
16
17
10
19
20
21
22
23
flUERAGE
01
5
5
5
5
5
5
6
9
9
7
b
5
4
4
4
4
4
4
5
6
6
5
5
5
5.33
o:?
ij
b
b
5
5
5
&
9
10
9
8
b
b
5
6
5
5
6
7
7
7
7
6
5
6.29
03
5
6
6
6
6
6
7
10
9
10
9
6
5
4
4
5
5
5
7
6
7
7
8
7
6.50
04
7
7
7
6
6
6
H
8
8
6
7
6
5
4
4
4
4
4
5
7
7
7
7
6
6.17
05
6
5
4
4
4
5
7
9
11
12
10
N/n
6
6
5
7
8
6
8
10
9
9
8
8
N/A
06
8
8
B
8
8
8
U
14
lb
1 1
13
B
6
b
b
6
7
8
9
8
7
6
5
6
8.38
07
5
4
4
4
4
b
9
12
1 1
7
7
6
6
5
5
5
4
4
4
5
5
4
4
4
5.50
08
4
4
4
3
4
5
5
6
0
a
7
6
5
5
4
5
4
4
5
5
5
5
4
4
4.96
09
4
4
4
5
5
5
5
6
7
8
7
b
5
5
5
5
4
5
5
5
5
5
5
4
5.17
10
4
4
4
4
4
4
4
4
5
4
4
4
4
7
3
3
5
5
4
4
4
4
4
4
4.00
11
3
4
4
4
3
2
2
2
3
3
3
2
2
2
3
3
3
3
4
4
4
4
5
5
3.21
12
4
3
3
3
4
4
4
4
4
4
5
5
4
4
4
4
5
5
5
5
4
4
4
4.08
13
4
4
4
3
4
4
4
5
4
5
6
5
5
6
b
5
5
5
6
5
5
5
4
5
4.75
14
4
4
4
4
4
4
b
6
6
6
6
5
5
5
6
5
5
6
6
7
7
6
5
4
5.25
15
b
6
5
5
5
a
11
9
9
9
6
6
6
5
5
5
5
6
b
6
6
6
6
6.33
16
6
&
5
5
5
5
5
5
5
5
5
5
4
4
4
4
4
4
5
6
5
5
5
5
4.88
17
J)
4
5
5
4
4
4
4
4
4
4
5
4
4
4
4
4
4
4
5
5
4
4
4
4.25
IP
4
4
4
4
4
4
3
3
4
3
4
4
4
4
4
4
5
4
5
5
6
6
5
5
4.25
19
5
5
5
5
5
6
7
8
7
6
7
5
6
5
5
5
5
5
7
7
7
7
&
6
5.92
20
6
6
6
6
6
6
8
10
12
10
7
4
5
4
4
4
5
6
6
6
6
6
5
5
6.21
21
5
5
5
5
5
5
5
7
9
9
7
b
b
6
6
6
7
8
9
10
11
12
0
9
7.13
22
10
9
9
8
t
8
10
13
13
11
5
6
9
10
7
b
7
7
8
y
8
8
10
10
B. 67
23
10
9
9
0
0
8
10
13
16
11
7
9
10
11
9
7
6
6
10
11
1 1
11
11
11
9.67
24
1 1
11
11
10
B
9
1 1
15
lb
12
b
9
8
6
6
5
4
4
5
7
10
10
11
11
9.00
25>
10
9
7
7
7
7
8
7
9
7
4
4
4
4
4
4
3
5
10
10
9
11
11
11
7.17
26
10
S
8
9
i
6
7
&
7
6
5
3
3
3
3
3
3
3
3
4
5
5
5
5
5.33
27
5
4
4
5
5
5
6
9
B
b
5
4
4
4
4
3
4
6
8
9
8
9
9
9
5.96
20
9
8
e
7
8
9
10
13
12
12
8
7
6
b
7
5
5
6
9
10
9
10
9
9
9.42
29
lu
10
8
a
a
8
1 1
16
16
11
7
7
b
b
b
5
5
5
5
a
10
10
10
10
8.58
30
9
9
9
9
0
e
10
17
16
11
8
7
6
b
7
b
5
6
8
10
10
12
12
12
9.21
31
12
1 1
9
7
8
8
9
10
11
7
4
5
4
3
3
3
3
3
4
6
6
6
7
7
6.50
-------
TABLE IV. HOURLY RND DRILY SIJMMRRY REPORT
Pollutant Observed: Nitrogen Dioxide Method of Rnalysis: Light Absorption
Sampling Interval : 1 Hour Reporting Units : part per hundred million
Month: Hugur.t. Year: 198?!
DAY
00
01
02
03
04
05
06
0?
CLOCK
08 09
TIME (Standard
10 11 12 13
T ime)
14 15
16
17
18
19
20
21
22
23
DRILY
fWERHGE
01
5
5
5
5
5
5
6
9
9
7
b
5
4
4
4
4
4
4
5
6
6
6
5
5
5.38
02
5
5
6
5
5
5
6
9
10
9
a
6
6
5
6
5
5
b
7
7
7
7
6
5
6.29
03
5
b
b
6
6
6
e.
S
9
9
8
b
4
3
3
3
3
4
ft
&
7
7
8
7
5.96
04
7
7
e.
b
5
5
7
Q
7
i*
6
5
3
3
3
3
3
4
5
7
7
7
G
7
5.67
05
6
5
4
4
4
5
£.
S
10
11
9
N/H
6
5
5
6
7
6
8
10
9
9
8
8
N/H
06
(
7
7
e
0
7
10
13
15
10
12
7
5
5
5
5
6
7
8
B
7
6
5
6
7.67
0?
5
5
5
5
4
~
b
a
12
10
7
6
5
5
5
5
4
4
4
5
5
5
4
4
5.54
08
4
4
4
3
4
5
5
b
7
8
7
6
5
5
4
5
4
4
5
5
5
5
4
4
4.92
09
4
4
4
5
5
cr
5
6
7
8
a
6
5
5
5
5
4
5
5
6
5
6
5
5
5.33
10
5
5
4
5
5
5
5
5
5
5
5
4
4
3
3
3
3
3
4
4
5
5
5
4
4.33
11
4
4
4
4
3
3
2
->
3
3
3
<1
2
3
3
3
3
4
4
4
4
5
5
3.29
12
4
J
3
3
4
4
4
A
A
4
a
4
N/H
N/H
N/R
N/R
N/R
N/H
N/H
N/R
H/H
N/H
N/R
N/8
13
n/n
N/R
N/n
N/fl
N/fi
N/n
N/n
5
4
5
&
4
4
5
5
4
5
5
6
5
5
5
4
4
N/R
14
4
4
4
4
4
4
t.
t.
f>
b
f,
5
4
4
5
5
5
6
6
7
7
b
5
4
5. 13
15
5
5
5
4
4
4
7
10
9
9
9
£>
6
5
4
4
4
5
5
N/H
N/fl
N/H
N/R
N/R
N/R
16.
N/H
N/H
N/H
N/H
N/H
N/H
H/H
4
4
5
5
Li
4
4
3
4
4
4
5
6
5
5
4
4
N/R
17
4
4
4
4
4
4
4
4
4
4
4
5
3
4
4
3
3
3
4
4
5
4
4
4
3.92
1 0
3
3
4
3
3
3
3
3
4
Jj
3
3
3
3
3
3
4
4
5
5
&
6
4
4
3.67
19
4
4
4
4
4
5
6
8
7
b
&
5
6
4
4
4
4
5
b
7
7
6
6
6
5.33
20
6
&
5
5
5
5
7
9
1 1
9
7
4
4
3
3
3
4
5
b
5
5
4
4
4
5.38
21
4
4
4
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FIGURE 1: BLOCK DIAGRAM
ELECTRONIC, OPITCAL, AND PNEUMATIC SUBSYSTEMS
Sample
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NO2 Scrubber
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-------
FIGURE 2
LINEARITY TEST
—i—
600
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Photometric Response, ppb
800
FIGURE 3
PHOTOCHEMICAL SMOG CHAMBER STUDY
Photometric N02
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A COMPARISON OF METHODOLOGIES FOR THE EXTRACTION
OF SULFATE ION FROM SIZE-DIFFERENTIATED PARTICLES
COLLECTED ON FILTER MEDIA
Dennis D. Lane
Associate Professor of Civil Engineering
University of Kansas
Lawrence, Kansas
Richard R. Nixon, Stephen J. Randtke
University of Kansas
Lawrence, Kansas
ABSTRACT
Four methodologies were studied to develop a simple and reproducible
sulfate extraction procedure representative of ambient conditions. Airborne
particles were collected with a high-volume sampler and a cascade impactor
system. The dry media and size-differentiated particles were subjected to
four successive processes to extract sulfate ions: undisturbed dissolution,
agitation, heating and boiling. At least 95? sulfate dissolution was
achieved in less than 24 hours by simply placing the filter media in
deionized water.
856
-------
A COMPARISON OF METHODOLOGIES FOR THE EXTRACTION OF SULFATE ION FROM SIZE-
DIFFERENTIATED PARTICLES COLLECTED ON FILTER MEDIA
INTRODUCTION
Measurement of the chemical composition of atmospheric particles is a
critical element in efforts to assess the environmental effects of dry
deposition, which has been implicated as a possible cause of damage to both
terrestrial and aquatic ecc3ystem3, to construction materials, and to human
health. Since sulfate can be a major component of dry deposition, and since
it is closely associated with acid deposition, an accurate method for the
determination of particulate sulfate is needed.
At the present time, there doe3 not appear to be a consensus on a
method for routine measurement of particulate sulfate. Harrison and Pio (1)
studied a technique where particulate sulfate was leached from filter
samples, using distilled water, first at 70°C for 30 minutes and then over-
night at ambient temperature in a mechanical shaker. Dolske and Gatz (2)
reported the determination of particulate sulfate by immersion and manual
agitation of 17 mm diameter filters in 5 ml of deionized water for three
minutes. Jenke (3) compared the performance of three different particle
extraction processes. These included an ultrasonic technique, a boiling
water method, and a sequential warm solution leach. He also gave con-
siderable attention to the influence of filter-media type on extraction
performance.
The purpose of the research presented in this paper is to compare the
effectiveness of four extraction processes for the removal of sulfate from
particles collected on dry filter media. These are: 1) dissolution in
undisturbed, deionized water, at room temperature (i.e., approximately 20°C)
for 24 hours; 2) dissolution in agitated, deionized water, at room tempera-
ture for 2U hours; 3) dissolution at 70°C in deionized water for one hour;
and 4) dissolution at 100°C in deionized water for one hour. Particle
samples were collected using a hi-volurae sampler and a hi-volume cascade
impactor. Dissolution of the particle derived sulfate ion using the four
methods was done in succession for each filter starting with undisturbed,
deionized water at room temperature.
The four methods chosen represent varying degrees of extraction
severity. The simplest and most natural process is the dissolution of
sulfate in undisturbed, deionized water at room temperature, for 24 hours.
Heating to 100°C for one hour represents a more severe case that Is expected
to produce the maximum water-soluble particle-derived sulfate ion
concentration.
EXPERIMENTAL PROCEDURE
Two high-volume samplers, located within 10 ft (3 m) of each other at
the University of Kansas, Lawrence, KS, were used to collect the particle
samples. One of the samplers is equipped with an Andersen size-selective
inlet (Model GMWA 7000) having a nominal particle-cut diameter of 15
microns. An Andersen rectangular-slotted cascade impactor is located under
the size-selectiYe inlet. This combination of particle-size differentiating
apparatl separates the particles into six distinct fractions. These are
particles with aerodynamic diameters of 15 to 7.2 ym, 7.2 to 3-0 vim, 3-0 to
1.5 |jm, 1.5 to 0.95 um, 0.95 to 0.49 uni, and less than 0.49 ym.
857
-------
The second high volume sampler (General Metal Work3, Model GMWL 2C00)
is of the standard type used to measure total suspended particles in ambient
air. Both samplers were operated simultaneously for 24-hour periods between
the dates of September, ^984 and July, 1985. Flow rates for the samplers
were fixed at 40 cfm using Kurtz flow controllers (Model 310). Filters were
placed in the samplers immediately before a test and removed within 2 hours
after termination of a sampling run. Standard U.S. EPA laboratory protocol
for filter weighing and standard U.S. EPA sampling protocol were used during
the course of the 3tudy.
The filters used in all sampling runs were Whatman 2000 EPM glass-fiber
filters. Collection filters were prepared for laboratory analysis by trim-
ming away large unexposed borders and identification markings with a
surgical scalpel. The remaining part of each filter was then cut into
approximately one-inch squares and placed in a labeled one-liter beaker.
Using a calibrated 500-ml volumetric flask, 500 mis of deionized water were
added to each beaker, which was then covered with parafilm. The deionized
water was supplied by a Milli-Q Reagent-Grade Water System (Millipore Corp.,
Bedford, Mass.) and had a specific conductance of 18 megohm-cm.
The filters were allowed to sit (undisturbed) in the deionized water
for 24 hours, at which time an 8-ml sample was withdrawn from each beaker
with a pipette that was triple rinsed with deionized water before each
sample was withdrawn. The 8-ml samples were stored in scrupulously cleaned
glass test tubes with teflon-coated screw-cap lids. The test tubes and
all other items that could make contact with the samples or the filter
solution were carefully cleaned and triple rinsed with deLonized water to
prevent contamination.
In the next extraction phase, the beakers were placed on a gyroshaker
apparatus to agitate the solution in a vigorous fashion for 24 hours. The
shaker is connected to a timing device that automatically controls the
process for a 24-hour period. After 24 hours, filter pieces and fibers were
allowed to settle, producing a clear supernatant from which 8-ml samples
were withdrawn.
The final two extraction procedures involved the heating of the filter
solutions to 70°C and 10C°C. The parafilm was removed from the beakers and
a clean watch glass was placed over each one. The beakers were then placed
in a temperature-controlled bath for one hour at 70°C. They were then
allowed to cool for approximately 30 minutes before being covered with
parafilm. After the filter solution cooled to room temperature (i.e.,
20°C), 8~ml samples were taken with the pipette. For the final extraction
procedure, the above steps were repeated at a temperature of 100°C.
In addition to the actual sample filters, blank filters were processed
to determine the contribution of the filter fibers and fiber bonding agents
to the total particle-derived sulfate ion concentration. For each field
test, a blank high-volume filter (8x10 inches) and a blank cascade irapac-
tor filter (4x5 inches) were subjected to the same extraction procedure.
Sulfate ion concentrations from these blank filters were very uniforc, as
described below. Therefore, the blank values were averaged over the entire
study period, and this average value was subtracted from the total sulfate
ion concentrations of the respective particle samples.
All of the 8-ml samples were subsequently analyzed for total sulfate
ion concentration using ion chromotography (Dionex, Corp., Model QIC). The
858
-------
analytical procedure followed recommended U.S. EPA protocol using an intei—
nal standard (fluoride). The precision of the instrument is ± 5? with an
accuracy of ±2%.
RESULTS AND DISCUSSION
Tables 1 and 2 summarize the total sulfate mass data (filter-blank
contributions are subtracted in all ca3es) for each test and each of the
four different extraction techniques. Table 1 presents the cascade-impactor
data as the total sulfate ma3s collected on all five stages plus the back-up
filter. Table 2 shows the sulfate mass associated with the total suspended
particle catch for each test.
Statistical analyses of this data are presented in Tables 3 and 1<-
Table 3 shows the ANOVA performed on the cascade impactor data. The null
hypothesis being tested is that there are significant differences between
the sulfate mass values for the four different extraction techniques.
Results of the ANOVA indicate that the null hypothesis is incorrect. In
reality, it can be stated with 95? confidence that there are no significant
statistical differences in the values produced by the four techniques. This
statistical analysis also indicates that the variation in total sulfate mas3
(which depends on the total atmospheric loading associated with a particular
sampling date) is so great as to make insignificant the relatively small
variation attributable to the extraction techniques.
Table 4 shows the same type of ANCVA for the total suspended particle
data. The same null hypothesis is tested, with similar results. Once
again, there are no statistical differences (at the 95% confidence level)
between the mass sulfate values determined using the four different extrac-
tion techniques.
Although the statistical analysis indicates no significant differences-
between the extraction techniques, at the 95? confidence level, another
approach is taken to further study possible differences among the
techniques. In this approach, the frequency of maximum and minimum sulfate
mass occurrence for each extraction procedure is examined. The results of
this analysis are presented in Tables 5 and 6. Table 5 shows the frequency
of maximum and minimum sulfate mass occurrence for the cascade impactor
data. It is obvious that the maximum sulfate mass value usually occurs
after heating for 1 hour at 1C0°C. The minimum value is achieved (in the
majority of cases) after a 2'i-hour detention in undisturbed, deionized water
at room temperature (20°C). Further analysis of the data corresponding to
fmax< tk,,e sulfate concentration corresponding to the most frequent occur-
rence of the maximum value among extraction techniques, and f , , the
rain
sulfate concentration corresponding to most frequent occurrence of the
smallest value among extraction techniques, indicates a maximum difference
between the two frequency data bases of U.6?. This snows (for the particles
collected in this study) that simple extraction of the particles with
deionized water at room temperature dissolves at least 95? of the total
water-soluble sulfate mass present in the sample.
Table 6 shows the results for the total suspended particle data. The
maximum difference between sulfate mass values corresponding to f;nax and
f . is 2.6?. This adds further credence to the statement that at least 95?
min
859
-------
TABLE 1
CASCADE IMPACTOR MASS SULFATE VALUES
FOR EACH TEST
24-Hr
Teat Det.
Designation (mg)
G 12.78
H 25.84
I 10.52
J 8.27
K 9.42
L 6.92
M 14.10
N 18.97
Avg. Value 13.35
24-Hr
Aglt. 1 Hr, 70°C
(mg) (mg)
12.87 12.27
25.57 26.89
10.44 10.34
9.54 9.20
9.72 9.87
6.99 7.16
14.21 14.36
19.19 19.28
13.57 13.67
1 Hr, 1009C
(mg)
12.59
26.87
11.17
8.77
10.02
7.23
15.06
20.17
13.99
860
-------
TABLE 2
TOTAL SUSPENDED PARTICLE HASS SULFATE VALUES
FOR EACH TEST
Teat
Designation
G
H
I
J
K
L
M
N
Avg. Value
24-Hr
Det.
(mg)
8.66
17-16
6.66
7.69
8.31
4 .24
1 2.82
1 6.40
10.24
24-Hr
Agit.
(mg)
9.23
17.06
7.92
8.17
8.77
4.73
1 3.00
17.10
10.75
1 Hr, 70°C
(mg)
8.98
15.26
8.09
8.12
8.74
4.77
13-18
17.17
10.54
1 Hr, 100°C
(mg)
9.28
15.36
6.67
8.35
9.02
4.81
13.33
17.46
10.54
TABLE 3
ANOVA FOR CASCADE IMPACTOR
Source of
Variation
Among Groups
Within Groups
df
3
28
SS
Ms
1.66 0.553
1140.14 40.719
(M /M ,
sg sw)
0.014
Total
31
1141.80
861
-------
TABLE 1
ANOVA FOR TOTAL SUSPENDED PARTICLES
Source of
Variation
Among Groups
Within Groups
df
3
28
SS
Ma
1 .0
555.8
0-333
19.85
(M /M .
sg sw)
0.017
Total
31
556.8
Type of Analysis
24-Hr Detention
24-Hr Agitation
1 Hr at 70°C
1 Hr at 100°C
TABLE 5
FREQUENCY OF MAXIMUM AND MINIMUM OCCURRENCE
FOR CASCADE IMPACTOR
f 1
max
0
2
1
5
' rain
5
1
?
0
Percent Difference Between f and f . = U.6%
max min
Type of Analysis
24-Hr Detention
24-Hr Agitation
1 Hr at 70°C
1 Hr at 100°C
TABLE 6
FREQUENCY OF MAXIMUM AND MINIMUM OCCURRENCE
FOR TOTAL SUSPENDED PARTICLES
f
max
1
0
1
6
r
" min
Percent Difference Between f and f , - 2.8*
max min
862
-------
of the total water-soluble sulfate Ion is obtained by simple dissolution in
deionized water.
Data on background levels of sulfate ion in the blank filters is of
interest to the sampling community. During the course of the study, twenty
blank filters were analyzed by all four extraction techniques. The maximum
sulfate mass contributed by any one of these samples is 0.1 mg. The average
value for all the data is 0.08 mg. A maximum variation between two samples
of 0.03 mg existed. This indicates a uniform blank level of sulfate mass
using the Whatman 2000 EPM glass-fiber filter.
It should also be noted that heating the filter suspensions virtually
destroys the adhesive properties of the filter fibers and causes them to
disaggregate. When this is done, large quantities of soluble organic matter
(presumably originating from dissolution of the filter binder) are released
into solution, as reflected by large increases in total organic carbon
(determined using a Dohrmann Model DC-80 total organic carbon analyzer).
The results of this study indicate that consistent and accurate deter-
mination of water-soluble particulate sulfate can be achieved by simply
placing the filter media in deionized water for 24 hours at room
temperature. On-going research to examine the impacts of particle-derived
sulfate on a natural ecotone r.ear Lawrence, KS, has successfully employed
this technique (simple dissolution) for over a year. However, since the
chemical composition of particles varies from region to region within the
U.S., differences among the four extraction techniques may be significant in
other regions.
CONCLUSIONS
The following conclusions are drawn Crom the results of thi3 study:
1 . At least 95? of the water-soluble sulfate in particles col-
lected on dry filter media was solubilized simply by placing
the filters in deionized water for 24 hours at room
temperature.
2. Whatman EPM 2C00 glass-fiber filters displayed background
levels of sulfate less than or equal to 0.1 mg, with a maxi-
mum variation of ± 0.03 mg.
3. Although the AN0VA indicates no significant differences at
the 95? confidence level among the four techniques examined,
the maximum water-soluble sulfate mass generally occurred
after heating to 100°C for 1 hour and the minimum water-
soluble sulfate mass generally occurred after dissolution in
deionized water for 24 hours at room temperature.
4. Heating of the filter suspensions caused disaggregation of
thefilter fibers and increased the total organic carbon
content of the solution considerably.
863
-------
REFERENCES
(1) Harrison, R.M. and Pio, C.A. (1982) Atmospheric Environment, Vol. 17,
PP. 1733-1738.
(2) Dolske, D.A. and Gatz, D.F. (1984) Deposition—Both Wet and Dry. Acid
Precipitation Series, Volume 4, Edited by Hicks, B.B., Teasley, J.I.,
Series Editor, Butterworth Publishers, Stoneham, MA, pp. 121-130.
(3) Jenke, D.R. (1983) Journal of the Air Pollution Control Association,
Vol. 33, pp. 765-767.
(4) Lee, R.L. Jr. and Wagman, J. (1966) American Industrial Hygiene
Association Journal, Vol. 27, pp. 266-271.
(5) Appel, B.R. et. al. (1984) Atmospheric Environment, Vol. 18, pp. 409~
416.
(6) Elzerman, A.W. and Overcamp, T.J. ( 1982) Solub ill zat ion Rate of
Atmospheric Particulate Matter and Impact on Water Quality, Report No.
104, Clemson University, Clemson, South Carolina.
864
-------
FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR)
AWONIUM SULFATE ANALYSIS ON TEFLON AIR FILTERS
Martin J. Pollard and Joseph M. Jaklevic
Lawrence Berkeley Laboratory
University of California
Berkeley, California
This paper reports on the improvement and automation of a method of analyz-
ing ammonium sulfate particles collected on Teflon* membrane filters. The
filters were analyzed by transmission measurements using Fourier transform
infrared spectroscopy after collection with dichotomous air samplers. The
spectra of the blank filters are subtracted from the spectra of the loaded
filters and an integration of the 1000-1135 cm~l absorbance band for sul-
fate leads to a lower limit of detection of 0.2 yg/cm2 on 37 mm 2 micron
Teflon filters. This corresponds to an ambient concentration of 0.1 pg/m^
for a 24 hr, 21.6 m3 air sample. Ammonium sulfate particulate standards
were prepared by sampling the output of a laboratory particle generator.
Concentrations were then determined by x-ray fluorescence analysis. An
automatic sample changer was constructed which accepts the filter carousel
from a Sierra/ Anderson model 245* automated dichotomous sampler. The
sample changer is controlled by the FTIR computer. The analysis is nondes-
tructive, automated, and requires no sample preparation.
865
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FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR)
AMMONIUM SULFATE ANALYSIS ON TEFLON AIR FILTERS
Introduct ion
Sulfur in atmospheric aerosols is generally present in the form of
arrenonium sulfate. Ammonium sulfate is important in visibility studies,
SOg-to-sulfate conversion processes, and nealth effects. It also com-
prises the major portion of the fine particle fraction (< 2.5 ym) of
atmospheric aerosols.
Sulfur aerosols are collected with dichotomous air samplers^ which
collect particles in two size fractions, < 2.5 urn and 2.5-15 ym particles
to reflect the bimodal distribution of inhalable particulates in the
atmosphere. There have been two approaches to automating dichotomous
samplers for unattended sampling over time periods of days, weeks, or
months. One approach is the linear slide tray sampler developed at Law-
rence Berkeley Laboratory (LBL). Another approach is a rotating sample
carousel. This second approach is incorporated in the Sierra/ Anderson
Series 245 automatic dichotomous sampler.
One means of analyzing the filters is elemental analysis with x-ray
fluorescence (XRF)2. This is a nondestructive technique that measures
the mass of the elemental sulfur on the filter. The chemical form of the
sulfur is not determined in this measurement although it is widely assumed
that it is predominantly ammonium sulfate.
Another means of analysis for ammonium sulfate is ion chromatography3.
This is a destructive technique that requires a wet chemical extraction of
the filters. It can detect as little as 0.5 ng of ammonium and sulfate
ions per sample with 10-12% error for ammonium and 5% error for sulfate.
The extraction procedure could alter the species found on the filter.
With the shortcomings of the previous two methods in mind, an alter-
nate analysis technique was sought that would be 1) non-destructive, 2)
sensitive, 3) could identify species collected on the filter, 4) was amen-
able to automation, ana 5) required no sample preparation. W. A. McClenny,
et al have shown that Fourier transform infrared spectroscopy (FTIR) is a
feasible approach**. The goal of this present research was to determine
if the sensitivity and accuracy of the technique could be improved for
ammonium sulfate analysis. In addition, the FTIR instrument was to be
configured for automated sample analysis.
Experimental Methods
The FTIR was a Nicolet mode; 5DXB* which is capable of 2 wavenumber
resolution. It is equipped with a 36 megabyte hard disk, a 1 megabyte
floppy disk, and 640 kilobytes of extra memory to provide adequate pro-
gramming and file storage space. It is also equipped with a flipper
mirror option to direct the infrared beam out of the main optical bench
and into an automatic sample changer compartment containing the loaded
Sierra sampler filter carousel. The sample compartment was not enclosed
at the time of this study so no purging of laboratory air was possible for
these experiments. An airtight enclosure is under construction.
866
-------
Additional sample focusing mirrors were mounted in the carousel compart-
ment to direct the infrared beam through the Teflon filters and into the
deuterated triglycerine sulfate (DTGS) detector. The Teflon filters are
placed in circular filter holders which are in turn placed in the circu-
lar carousel. The carousel holds 20 pairs of filters. The infrared beam
covers an approximately 15 mm diameter area on the Teflon filter to average
any nonuniformity in particle deposition. The filters are located as close
to the detector as possible to increase the collection of light that is
scattered by the filter. The carousel is mounted horizontally over the
DTGS detector. There is also sufficient space to install a mercury cadmium
telluride (MCT) detector if desired. A stepper motor rotates the carousel
to position the filters for analysis. Another stepper motor moves the car-
ousel horizontally to select either the inner or outer concentric circle
of filters.
The Nicolet 1280* computer controls data collection, data storage, and
the positioning of the correct filter in the infrared beam. It communi-
cates to a microcomputer (BASICON model 2N, Portland, OR*) through an RS232
interface. This microcomputer controls and monitors the carousel stepper
motors and microswitches and can be programmed in TINY BASIC or machine
language for control applications.
Laboratory ammonium sulfate was generated for calibration purposes and
to provide samples to study in the absence of soot and other compounds.
Air is passed through 1.4 kg of indicating Drierite* and a series of parti-
culate filters. This clean air is then used to aspirate a solution of
ammonium sulfate in water. The liquid particles are passed up through a
heater tube, a drying column, a Kr 85 particle deionizer, a final heating
tube, and then into the dichotomous air sampler inlet. The laboratory-
generated particles produce an absorption spectrum that is identical to
that seen in actual ambient samples. Scanning electron micrographs show
that the laboratory-generated ammonium sulfate particles are on the order
of 2 microns in size while ambient ammonium sulfate particles are in the
0.1-1 micron range. There is also a humidifying option which was not used
in these experiments. The apparatus was designed by Roland Otto and built
with the help of William Searles at LBL.
Two micron pore size Teflon filters (Gelman TEFLO PTFE* with poly-
methyl pentene support ring) were placed in the Sierra Sampler filter
holders and into the carousel. Reference spectra of each blank filter
were automatically taken with the number of scans varying from 10 to 1000.
Each set of spectra for each filter were then stored on disk for future
use in background subtraction. The blank filters were then removed from
the Sierra filter holders and put into the 2 by 2 in. filter slide holders
suitable for use in the linear slide tray of the LBL automated dichotomous
air sampler. A Sierra automated dicnotomous air sampler was not available
for use. The Teflon filters were then loaded with laboratory-generated
ammonium sulfate with depositions ranging from 2-50 pg/cm2. The filters
were analyzed for total sulfur using x-ray fluorescence. They were then
removed from the filter slides and returned to the Sierra filter holders
for analysis.
During actual air sampling, the Sierra automated dichotomous sampler
samples air with a total flow rate of 1 cmh with a flow rate of 0.9 cmh for
the fine particle fraction and 0.1 cmh for the coarse particles. Typical
sampling periods are 6, 12, or 24 hr which represents 5.4, 10.8, and
21.6 m3 of sampled air on the fine particle filters.
867
-------
Results
Figure 1 shows an FTIR spectrum obtained from a 2 micron Teflon fil-
ter loaded with approximately 58.7 ug/cm^ of laboratory-generated ammon-
ium sulfate. Figure 2 shows the spectra of a 1-micron (solid line) and a
2-micron (dashed line) blank Teflon filter. The vibrational bands of
importance for sulfate are from 596-640 cm-l with a peak at 620 cm_l and
from 1000-1200 cm~l with a peak at 1116 cm"l. The ammonium band of inter-
est is from 1300-1550 cm~l with peak at 1420 cm-l. Another ammonium band
from 2400-3520 cm-l was not used because it lies in an area of significantly
higher baseline noise levels. The ammonium band at 1420 cm-l does not over-
lap any other band but it does lie in a region of maximum water absorption
which would indicate that the instrument should be purged of water vapor to
achieve maximum noise reduction for this band. Both sulfate bands overlap
Teflon bands in the regions 1150-1250 cm_l and 600-675 cm-l. The Teflon
band at 1116 cm-l, below the two strongly absorbing Teflon bands, can
clearly be seen because of the relatively high loading of this sample. The
smaller sulfate band at 620 cm-l can also be seen by careful comparison to
Figure 2.
Figure 3 is a graph of the mass loading in ng/cm^ as determined by x-ray
fluorescence versus the integrated areas of the ammonium ana sulfate bands
after background subtraction using the blank filter spectra taken earlier.
A linear least squares line was fit to each set of data and a clear linear
relationship can be seen. The error in the slope and intercept for each
line was calculated and a lower limit of detection (LLD=3a) was determined
using a propagation of errors approach^. Table I shows the calculated
lower limits of detection for ammonium and sulfate on 37 inn, 2 micron
Teflon filters for each absorption band. The last column shows the equiva-
lent ammonium sulfate particulate concentration in air for a 24 hr sampling
period (21.6 m3 sampled air). The data in Figure 3 represents 100 spec-
tral scans with the FTIR spectrometer.
Di scussion
Figure 4 shows the spectra of an actual air sample taken in Portage,
Wisconsin (note the expanded scale). The ammonium sulfate peaks are
exactly the same as those found in the laboratory generated samples. This
filter spectra represents one of the higher particulate concentrations
measured in this city with the majority of the measurements being much
lower than the concentration on this filter. Similar filter samples from
Steubenvi11e, Ohio have much higher particulate concentrations the highest
having absorbances greater than 2.0. On all air filter samples soot will
be found in the fine particle fraction and will be evident as a continuous
increase in the baseline of the spectra. No nitrate was found on any of
the filters from Portage or Steubenvi11e. Ammonium nitrate particles gen-
erated on our particle generator show a prominent nitrate peak at 1340 cm-l
overlapping the amnonium peak at 1420 cm~l and a weaker nitrate peak at
828 cm-l.
This technique will not work for glass fiber filters, paper filters, or
Nylasorb* filters because these materials cause too much scattering and
aDsorption. Two micron Teflon filters (Gelman TEFL0 PTFE with polymethyl-
pentene support ring) are preferred to 1 micron filters because of their
lower absorption. The highest absorption peak for the 2 micron filters
represents approximately 10-15% transmission while those for the 1 micron
filters are totally absorbing. Teflon filters also have a remarkably
simple absorption spectrum (see Figure 2). The 2 micron filters have the
same collection efficiency as the 1 micron filters.
868
-------
Integration of the 1116 cm~l sulfate band the provides the best mea-
sure of ammonium sulfate. Analysis of the sulfate bands requires subtrac-
tion of the blank Teflon filter spectra from the spectra of the same filter
after particulate collection in the air sampler. Background subtraction is
not an entirely straightforward technique. Subtraction of absorbance bands
is extremely sensitive to slight distortions in the spectral data. The
subtraction of two spectral files with small differences in absorbance band
shapes can result in derivative-like noise far in excess of what would be
expected simply by propagation of errors in the subtraction process. This
effect can negate any signal-to-noise improvement obtained by increasing
the number of scans on the data. Figure 5 illustrates this effect clearly
by showing the result of an uneven subtraction of the two Teflon peaks at
1135-1250 cm-1. This subtraction was performed on two spectra of the
same blank filter after 1000 scans for each spectra. Spectral distortion
may be related to light scattering effects on the detector that result from
moving the filter into and out of the infrared beam between spectral scans.
The subtraction artifacts can be worse if the spectra from two different
filters are subtracted from each other because there can be significant
absorption variability between filters. As a result of these "subtraction
problems", the sulfate peak at 1116 cm~l was integrated in the region
from 1000-1135 cirri which is in a region removed from the subtraction
artifacts due to the large Teflon absorption peaks.
The baseline noise will improve with the square root of the number of
scans that are averaged. The number of scans used has to be weighed
against the 1.5 sec needed per scan. The analysis for 100 scans requires
about 3.5 min per filter while that for 1000 scans requires almost 27 min.
The scan speed can be increased by decreasing the resolution of the scan
but this would lead to greater subtraction problems. An MCT detector is
both quieter per scan and has a greater scan speed at the same resolution
but it has less dynamic range than a DT6S detector. This could lead to
subtraction problems as well. An MCT detector has not yet been thoroughly
tested for this application.
Conclusions
Fourier transform infrarec transmission spectroscopy can provide an
accurate and sensitive means of quantifying ammonium sulfate deposition on
2 micron Teflon filters. A necessary requirement, however, is that refer-
ence spectra be obtained and stored before sampling to be used in back-
ground subtraction. Further increases in sensitivity may be possible with
the use of a mercury cadmium telluride detector. If analysis time is not
a consideration, then increasing the number of scans should decrease the
lower limit of detection. The instrumentation is automated and no sample
preparation is required. Specific species can be observed by the presence
and identification of absorbance peaks in the spectrum. The analysis is
nondestruct i ve.
Further work will consist of analyzing actual air samples and compar-
ing these results with analysis by x-ray fluorescence and ion chromato-
graphy. Work will proceed toward quantifying the mass loading of soot as
wel 1.
Acknowledgments
We would like to thank Robert Giauque for performing the x-ray fluo-
rescence measurements, William Searles for the mechanical construction of
the sample changer, and Roland Otto for use of the particle generator.
869
-------
~Reference to a company or product name does not imply approval or
recommendation of the product by the University of California or the U. S.
Department of Energy to the exclusion of others that may be suitable.
Although the research described in this article has been funded wholly
or in part by the U.S. Environmental Protection Agency through an Inter-
agency Agreement No. IAG-DW89931232-01-Q with the U.S. Department of Energy
under Contract No. DE-AC03-76SF00098, it has not been subjected to Agency
review and therefore does not necessarily reflect the views of the Agency
and no official endorsement should be inferred.
REFERENCES
1. B. W. Loo, R. S. Adachi, C. P. Cork, F. S. Goulding, J. M. Jaklevic,
D. A. Landis, and W. L. Searles, "A second generation dichotomous
sampler for large-scale monitoring of airborne particulate matter,"
Lawrence Berkeley Laboratory Report LBL-8725, (1979).
2. J. M. Jaklevic, D. A. Landis, ana F. S. Goulding, "Energy dispersive
x-ray fluorescence spectrometry using pulse x-ray excitation",
Advances in X-ray Analysis, R. U. Gould, C. S. Barrett, J. B. Newkirk,
and C. 0. Rudd, eds., Kendahl/Hunt, Dubuque, IA, 1976, 19: pp Z53—
265.
3. E. Sawicki, J. D. Mulik, E. Wittgenstein, eds., Ion Chromatographic
Analysis of Environmental Pollutants, Ann Arbor Science, Ann Arbor,
MI, 1979, Volume 1.
4. W. A. McClenny, J. W. Chiltiers, R. Rohl, and R. A. Palmer, "FTIR
transmission spectrometry for the nondestructive determination of
ammonium and sulfate in ambient aerosols collected on teflon filters,"
Atmos. Environ. 19: pp 1891-1898 (1985).
5. G. L. Long, J. D. Winefordner, "Limit of detection, a closer look at
the IUPAC definition," Anal. Chem., 55(7): pp 712-724A, (1983).
870
-------
Table I
Lower Limits of Detection
Ammonium Sulfate
Filter concentration 24 hours, 21.6 m3 sample
Mg/cm2 Mg/m3
Sulfate
596 - 640 cm"1 1.70 0.86
Sulfate
1000 - 1135 cm"1 0.20 0.10
Ammonium
1300 - 1550 cm-1 0.15 0.20
871
-------
50 scans 50.65 (2.48) mass ammonium sulfate 8
2.4
2.0
-------
16
12
10
to
0)
ca
IS
a>
cl
1
I I
Calibration
-
Sulfate
_
yS 1000-1135 cm"^_
Ammonium
1300-1550 cm-1 /
/ ~
/
/»
Sulfate
596-640 cm-1 _ -
I I
gure 3.
0 10 20
XRF mass nqjcm2
Calibration of ammonium and sulfate.
A bad day in Portage, Wi #232830
30
40
X5L 8W-10410
aj 0.452
1550 1435 1320 1205 1090 975 860 745 630 515 400
Wavenumbers (cm-1)
XBL 864-1D404
gure 4. High ammonium sulfate loading for Portage, Wisconsin.
873
-------
1000 scans
0.02
<
-0.01
i r
i i r
i_ L
1450 1350 1250 1150 1050 950 850 750 650 550 450
Wavenumbers (cm 1)
XBL 854-10400
Figure 5. Subtraction artifacts clue to blank Teflon filters.
874
-------
SUBLIMATION SOURCES FOR NITROUS ACID AND
N-COMPOUNDS IN AIR
Robert S. Braman
Maria de la Cantera
Department of Chemistry
University of South Florida
Tampa, Florida 33620
A new technique has been investigated for the production of parts-per-
billion range concentrations of some NO* type compounds in air. The method
is based upon sublimation of oxalic acid in an air stream onto an appro-
priate target compound with which it reacts to produce a gaseous product.
With sodium nitrite and 30-60% relative humidity gas nitrous acid is the
predominant product in up to 90% mole percent purity. In very dry air
nitric oxide predominates, via redox reaction. Nitric acid in air is pro-
duced at low humidities by reaction of oxalic acid with potassium nitrate.
Similarly, hydrogen cyanide is produced from sodium syanide and thiocyanic
acid from potassium thiocyanate.. The amounts of the gaseous compounds
produced dynamically are small but useful for preparing low concentrations
in air, usually in the 10 to 500 ng/L range. The identity of nitrous acid
was confirmed by chemical and spectroscopic studies and used in the develop-
ment of a sequential, selective hollow tube system for reactive N0X com-
pounds. No method was found for producing nitrogen dioxide in air by
sublimation. Diffusion and permeation sources of nitrogen dioxide were
subsequently studied. Substantial problems were found in the production of
pure nitrogen dioxide in air. Large fractions of nitrogen dioxide are
converted to nitric acid and nitrous acid, especially in glass systems.
Plastic systems are recommended.
875
-------
SUBLIMATION S0URCE5 FOR NITROUS ACID AND
N-COMPOUND5 IN AIR
Introduction
Testing and development of methods for trace concentration of the
reactive nitrogen oxide type compounds, i.e. HNO,, HNO,,, NOn and NO, requires
reasonably pure source of these compounds in air at low concentrations. Since
all of these are quite reactive with each other in some circumstances and
with traces of reducing compound impurities, their preparation in high purity
in air is difficult. Permeation devices are available for NOg and NO. Nitric
acid can be diffused out of a sulfuric acid - nitric acid mixture.
Nitrous acid has been prepared by solution reactions of acids with
nitrite ion (1). Nitrous acid has also been prepared from a mixture of NO
with NO2 in the presence of water (2). Nevertheless, these are far from
pure sources, always being mixed with large amounts of NO and NO2-
The use of oxalic sublimation onto sodium nitrite was eventually tried
and found useful for preparing good purity HNOg in air. Other extensions
of this technique were eventually tried.
Experimental
The oxalic acid sublimation apparatus developed and finally used in
most work is shown in Figure 1. Filtered compressed air was humidified to
the desired level and passed at 0.8 to 1.2 L/min through the 3 mm o.d. tube
packed with approximately a 2 cm long section of oxalic add dihydrate and
a 2 cm long section of crystalline sodium nitrite. Humidities were main-
tained in the 30-60% R.H. range. Sodium nitrite is hygroscopic and so cannot
be exposed to very high humidities.
A similar arrangement was used for preparation of nitric acid, nitric
oxide hydrogen cyanide, thiocyanic acid. Nitric acid preparation used
potassium nitrate as the target compound at low humidity. Hydrogen cyanide
was produced when sodium cyanide was the target compound. Thiocyanic acid
was produced when potassium thiocyanate was the target compound. Nitric
oxide was produced when dry tank air was passed through the sublimation
device with sodium nitrite as the target compound. Use of anhydrous oxalic
acid is also recommended here.
Sequential, selective hollow tubes were used to preconcentrate effluent
gases from the sublimation sources. These were then analyzed by thermal
desorption of collected analytes using a N0X chemiluminescence analyzer (3)
(4). The selective hollow tube system provided for N0X speciation into HNO3,
HNO2, NO2 and NO with detection limits near 1 ng per sample.
Results and Discussion
The nitrous acid in air sublimation type source was used under several
conditions of humidity and produced the composition shown in Table I. Most
notable is the shift in composition from HNO2 to NO when dry air is used as
the carrier gas.
876
-------
If used to produce nitric oxide at a high purity, a sodium carbonate
clean-up tube can be used to remove the small amount of nitrous acid pre-
sent. When used in a permeation oven, it was found that increasing the
temperature above the usual 25aC controlling level increased the percentage
of nitric oxide and nitrogen dioxide is produced. A permeation oven fitted
with a sublimation source was used for several weeks with over 90% mole
fraction of nitrous acid being produced at a rate of 45-55 ng/min.
The identity of nitrous acid in air was confirmed by optical absorption
spectroscopic analysis of the nitrous acid from a warmed sublimation source.
Table II compares experimental and referenced absorption peaks. Chemical
tests were also conducted and found to be positive for HNC^.
Nitric acid was produced at rates of 50-53% ng/min depending upon temp-
erature but at low humidities (18% R.H.). In general, low concentrations
of nitric acid are produced but with almost no impurities.
Nitrogen dioxide was studied as a source from a plastic and glass sys-
tem. If glass is used and carrier gas system of moderate himidity, large
percentages of HNO-j, HNO^ and NO can be co-present with NO^. Plastic
systems and lower humidity greatly improves the purity of the nitrogen
dioxide produced.
Hydrogen cyanide and thiocyanic acid were produced at evolution rates
of 25 to 50 ng/min when sodium cyanide and potassium thiocyanate respective-
ly were used as target compounds. Humidity was maintained at 18% R.H. The
HCN and HSCN in air samples were analyzed using the same chemi1uminescence
analyzer system as for the N0X compounds but oxygen or air were used as
the carrier gas and silver was used as the preconcentration surface of the
hollow tubes.
Conclusions
A sublimination source is likely the best available technique for
producing a low concentration of comparatively pure nitrous acid in air
for testing specific analysis methods. Extensions of the technique have
been demonstrated for HNO,, NO, HCN, and HSCN' in air. It is apparent that
this same approach can also be used for HF, CO^, S0^ and H£S in air.
Sublimation sources are easy and convenient to prepare and use, but
very specific analysis schemes must be used for the N0x type compounds to
verify air mixture purity. Although the sources are reasonably constant
in output of analyte gas after equilibration, weighing losses cannot be
expected to be useful for calibration. Calibration of the source output
is likely best done by use of an appropriate specific analysis method.
Acknowledgement
This work was supported in part by the Air Resources Board, State of
California.
877
-------
References
1. R.A. Cox and R.G. Derment, "The ultraviolet absorption spectrum of
gaseous nitrous acid," J. Photochemistry, 6, 23-24 (1976/77).
2. H.S. Johnston and R. Graham, "Photochemistry of NO and HNO compounds,"
Can. J. Chem., 52, 1415-1423 (1974). x x
3. R.S. Braman, T.J. Shelley and W.A. McClenny, "Tungstic acid for pre-
concentration and determination of gaseous and particulate ammonia and
nitric acid in ambient air," Anal. Chem., 54, 358-364 (1982).
4. R.S. Braman and M.A. de la Cantera, "A sequential, selective hollow
tube system for speciation of NO compounds in air," Anal. Chem.,
1986 (in press). x
5. G.W, King and D. Moule, "The ultraviolet absorption spectrum of nitrous
acid in the vapor state," Can. J. Chem., 40, 2057-2065 (1962).
878
-------
Table I. Analysis of HNO2 Sublimation Sources
(Percentage Composition)
Room Temperature Source (23-25°C)
HN03 HN02 N02 NO R.H.{%) Comments
79.5 18.4 18.4 31%
83 0 17 24%
1.4 89.2 2.9 6.5 242
89.4 3.4 9.2 24%
Air carrier gas at 0.8 - 1.2 L/min.
Humidity measured at sample outlet.
Mole percent.
137 ng/min HN02
just prepared (N=l)
27 ng/min HNO^
after 6 weeks
91.4 0 8.6 24£ 34 ng/min HN02
after 7 weeks
37 ng/min HN02
after 9 weeks
52 5 43 0 88 ng/min HN02
just changed to
dry air
24.1 3.6 72.2 0 81 ng/min HN02
dry air 2 days
later
111 ng/min HN02
larger dia. source
(N=3)
879
-------
Table II. Absorption Spectrum Data for HNC^
a -1 -1
Observed Reference e, cm ppm (N=l)
371.6 nm
371.6 nm
2.27
X
10"6
1
364.3
368.3
3.13
X
lO"6
1
364.8
364.7
2.63
±
0.03
X
lO"6
2
357.6
357.7
3.23
+
0.56
X
10"6
3
354.3
354.3
4.43
±
0.42
X
10~6
3
351.0
350.9
1.43
+
0.26
X
10-6
3
LO
•£»
00
341.8
3.15
+
0.72
X
10-6
3
338.8 338.8
330.9 330.8
328.1 327.8
a b
Ref. (5) Experimental values
880
-------
airo:
NaNOr
glass wool
h2o
Figure 1 Apparatus Arrangement for Sublimation Sources
881
-------
William R. Betz,
UTILIZATION OF A CLASS I, NON-SPECIFIC ADSORBENT
CARBOTRAP, FOR THE PREDICTION OF SAMPLING
C.D. Wachob
Supelco, Inc., Supelco Park,
Beliefonte, PA 16823-0048
Analysts monitoring airborne contaminants not included in federal
methodologies must decide which adsorbent will provide the best
adsorption/ desorption efficiencies for the adsorbate. However, because
an adsorbate might possess one or more functional groups and can exist in
many molecular shapes and sizes, choosing the adsorbent can be difficult.
Use of a Class I, nonspecific adsorbent can eliminate concern over which
functional group(s) an adsorbate possesses. Carbotrap, a graphitized
carbon black, is a Class I, nonspecific adsorbate with the appropriate
adsorbing capacity. It allows the analyst to predict the required
sampling volume from the molecular geometry of the adsorbate.
Sampling volume predictions depend on two considerations, the surface
interactions between the adsorbate and Class I adsorbent, and the
physlcochemical characteristics of the adsorbate molecules. Knowledge of
surface interactions has been used at Supelco to predict sampling
volumes. Carbotrap has been packed in traps designed to mimic typical
adsorption tubes, and evaluated by using adsorbates with a wide range of
functional groups and molecular volumes. Adsorbate/ adsorbent
relationships have been characterized in the low coverage region (Henry's
Law region), and in higher concentrations, by using sampling
(breakthrough) volumes (V|), adsorption coefficients (Ka), and
equilibrium sorption capacities (Qg)- Information extracted from these
data enables one to predict V|.
Predictions of solvent desorption of an adsorbate from the Carbotrap
surface are based on knowledge of the miscibility of the desorbing solvent
and the adsorbate, and on Carbotrap surface saturation. Predictions of
thermal desorption are related to the quantity of thermal energy required
to dissociate the London forces between adsorbate and adsorbent.
Carbotrap effectively adsorbs a wide range of airborne contaminants,
allowing analysts to sample at predetermined volumes based on known
molecular characteristic values. This eliminates the need to decide which
adsorbent is best suited to a particular class of compounds.
882
-------
UTILIZATION OF A CLASS I NON-SPECIFIC ADSORBENT, CARBOTRAP,
FOR THE PREDICTION OF SAMPLING VOLUMES FOP ADSORBATES
ACCORDING TO MOLECULAR SIZE AND SHAPE
W.R. Betz and G.D. Wachob
Supelco, Inc., Supelco Park., Bellefonte, PA 16823-0048
Analysts monitoring airborne contaminants in various sampling modes
must decide which adsorbent will provide the best adsorption/desorption
efficiencies for the adsorbates. Because an adsorbate may possess one or
more functional groups and exist in many molecular 6izes and shapes,
choosing the adsorbent becomes difficult. Utilization of a Class I,
non-specific adsorbent (1) can eliminate concern over which functional
group(s) an adsorbate possesses. Carbotrap, a graphitized carbon black,
is classified as a Class I, non-specific adsorbent (Table I) and has the
physical properties necessary to adsorb a wide range of organic compounds
(Table II). Furthermore, the hydrophobic surface properties of this
adsorbent enable It to adsorb organic compounds in humid sampling modes.
The adsorptive properties of Carbotrap were characterized by
following procedures outlined in EPA document #600/7-78-004 (2). The
evaluation was focused on the adsorbate/adsorbent Interactions occurring
In the low coverage (I.e., Henry's Lav) region by using the established
specific retention volumes (vg), adsorption coefficients (Ka), and
equilibrium sorption capacities (Qg) (Table III). Retention volumes for
each adsorbate were determined at elevated temperature, then extrapolated
via linear regression analyses to obtain retention volume data for ambient
(20CC) temperature. From this data, the adsorption coefficient and
equilibrium sorption capacity were then determined.
To establish the adsorbate/Carbotrap relationship of several key
compounds possessing different functional groups the specific retention
volume, adsorption coefficient and equilibrium sorption capacity for eight
compounds was obtained and compared to values for the adsorbents Tenax GC
and XAD-2 (Table IV).
The data obtained indicate that Carbotrap possesses a greater
affinity for the compounds of Interest, with the exception of the
n-Pentanoic acid/Tenax relationship. The greater interaction in the
latter relationship is due to the Induced dipole interactions between the
acid functional group of n-pentanoic acid and the phenylene oxide
functional groups of the Tenax surface.
To expand the Infonaation on adsorbate interaction for organic
compounds and Carbotrap, 38 adsorbates were evaluated. Table V
illustrates, in order of increasing specific retention volumes, the data
obtained as well as the correlation coefficients, for each of these
adsorbates.
Information extracted from this characterization evaluation, as well
as the non-specific characteristics of Carbotrap, allows an analyst to
construct a predictive model for sampling volumes based on
883
-------
the physical characteristics of the adsorbates. The physical properties
of polarizability and molecular connectivity were found to provide an
excellent measure of both the electronic and structural properties of an
adsorbate molecule. Table VI illustrates the equations used to obtain
these values. Table VII shows how polarizability and connectivity values
are determined.
Linear regression data, focusing on the predictive model, for
Carbotrap and eight classes or organic compounds are listed in Table
VIII. Secondly, the linear regression data focusing on the eight specific
adsorbates, previously mentioned, for the adsorbents Carbotrap, Tenax, and
XAD-2, are illustrated in Table IX. The data Indicates that tighter
correlation is obtained when utilizing a Class I adsorbent, such as
Carbot rap.
The utilization of the predictive model is illustrated using two
adsorbates: ethylbenzene, and 2-chloroethanol. Table X compares the
predicted retention volume versus the experimentally obtained retention
volume. Both predictions were made with >98% confidence.
The predictions of solvent desorption of the adsorbate from the
Carbotrap surface are based on knowledge of miscibility of the desorbing
solvent and the adsorbate and on the surface saturation of Carbotrap.
Table XI illustrates the desorption efficiency data for eight key
adsorbates, using carbon disulfide and acetonitrile as the desorbing
solvent, and the desorption efficiency data for C4-C8 aliphatic amines
utilizing ethanol as the desorbing solvent. Predictions of thermal
desorption are a function of the thermal energy requirements necessary to
greatly decrease the London (dispersion) forces, assumed by the adsorbate
and adsorbent. Table XI also lists thermal desorption efficiency values
for the eight key adsorbates mentioned previously.
Carbotrap, a Class I non-specific adsorbent, effectively adsorbs and
subsequently desorbs a wide range of organic contaminants, allowing
analysts to sample at predetermined sampling volumes based upon known
adsorbate molecular characteristic data. This predictive mode eliminates
the need to choose specific adsorbents for specific adsorbate monitoring.
REFERENCES
1. Kiselev, A.V., and Yashin, Y.I., "Gas Adsorption Chromatography,"
Plenum Press, NY, 1969, 11-16.
2. U.S. EPA, "Characterization of Sorbent Resins for Use in Airborne
Environmental Sampling" EPA document # 600/7-78-054, 1978.
884
-------
TABLE I
Classification of Molecules and Adsorbents
by Capacity for Nonspecific and Specific Interaction (1)
Adso rbent s
Molecules
Type I
without ions
or active
groups
Type II
with
localized
positive
charges
Type III
with
localized
negative
charges
Group A:
with spherically symmetrical
shells or o-bonds
Nonspecific interactions governed
mainly by dispersion forces
Group B:
electron density locally
concentrated on bonds or
links, It -bonds
Group C:
with positive charge
localized on peripheral
links
Nonspecific
interactions
Nonspecif ic
+ specific
interactions
Group D:
with functional groups
having locally concentrated
electron density and positive
charge on adjacent links
(1) Kiselev, A.V., and Yashin, Y.I., "Gas Adsorption Chromatography,"
Plenum Press, NY, 1969, 11-16.
TABLE II
Physical Properties of Adsorbents
Carbot rap
T enax G.C.
XAD-2
Surface area (m2/g)
100.0
23. 5
364.0
Particle size (u) mesh size
20/40
35/60
20/40
Density (g/ml)
0.38
0.14
0.38
Pore volume
—
0.053
0.854
Bed weight (g)
0.4637
0.1650
0.3966
Total surface area
46.37m2
3.878
144.4
885
-------
TABLE III A
Specific Retention Volume (V|)(20) Equation (2)
Calculated volume of gas
ml of gas passing through the system
ut =
vg
grains of adsorbent weight (grains) of adsorbent
j F (t -t )
c r a
W
a
= breakthrough volume
TABLE III B
Adsorption Coefficient (Ka) Equation (2)
Tt
K =
V
g
a A* R T.
s k
Where: A°s = Surface area of
sorbent (m 2/g)
li^ - .temperature in
V| = S.R. Volume (ml/g)
R « 6,3 j 10^ml-nan/mole-°k
TABLE III C
Equilibrium Sorption Capacity (Qg) Equation (2)
Q = k A C (760mm H ) (MW sorbate)
g a s g g
_
Where: Cg ~ Gas phase concentration
of sorbate in ppm
(vol./vol/ « vl/L)
MW = Molecular weight of
adsorbate
(2) U.S. EPA, "Characterization of Sorbent Resins for Use in Airborne
Environmental Sampling" EPA document # 600/7-78-054, 1978.
886
-------
TABLE IV
Specific Retention Volumes (V£)(20)
for Carbotrap, Tenax and XAD —2
Adsorbate
n-Decane
Benzylamine
Chlorobenzene
p-Xylene
p-Cresol
n-Pentanoic Acid
Cyclohexanone
2-M et hy 1 -2-Prop ano 1
Carbotrap
Vt C20°C) (ml/g)
Tenax
XAD-2
4.79
X
109
1.56
X
107
3.36
X
2.23
X
107
3.57
X
106
1.63
X
1.58
X
106
1. 51
X
105
4.84
X
4.24
X
107
3.88
X
105
7.95
X
2.06
X
107
1.50
X
107
4. 96
X
A.21
X
105
9. 78
X
105
1. 01
X
2.04
X
106
1.06
X
106
6.27
X
6. 52
X
103
6.86
X
102
5.42
X
10'
107
105
106
106
105
105
103
887
-------
TABLE V
Specific Retention Volumes for 38 Adsorbates
COMPOUND
Ethane
n-Propane
n-Butane
Ethanol
Acetic Acid
Propionic Acid
1,2-Dichloroethane
2-Butanone
n-Pentane
2-Methyl-2-Propanol
Benzene
1,1,2-Trichloroethylene
n-Butanol
1,1,2-Trichloroethane
n-Hexane
n-Pentanoic Acid
Phenol
Toluene
Chlorobenzene
Cyclohexanone
n-Butylamine
4-Heptanone
Dichlorobenzene
n-Octane
Ethylbenzene
p-Cresol
Benzylamine
p-Xylene
Acetophenone
Isopropybenzene
n-Propylbenzene
n-Decane
n-But ylben zene
Bipheny1
n-Hexylbenzene
n-Dodecane
n-Octylbenzene
n-Tetradecane
L/g)
LIN. REG. PLOT
1.73
X
101
1.00000
5.49
X
101
0.99412
A.06
X
102
0.99875
A.93
X
102
0.99219
7.16
X
102
0.99690
1.66
X
103
0.98410
1.94
X
103
0.99848
3.76
X
103
0.99611
5.89
X
103
C. 99940
6.52
X
103
0.98650
1.17
X
10A
0.99802
1.27
X
104
0.99939
1.92
X
10^
0.99643
2. 47
X
10^
0.99986
7.99
X
104
0. 99871
4.31
X
105
0.97190
6.16
X
105
0.99941
6.50
X
105
0. 99972
1.58
X
106
C.99990
3.04
X
106
0.99581
2.08
X
106
0.99935
2.44
X
106
C.99991
1.34
X
107
0.99925
1.61
X
107
0.99989
2.03
X
107
0.99989
2,06
X
107
0.99948
2.23
X
107
0.99990
4.27
X
107
0.99963
6.40
X
107
0.99971
1.70
X
108
0.99999
1.72
X
109
0.99993
4. 79
X
109
0.99971
5.83
X
109
0.99937
3.74
X
lOl2
0.99999
7.00
X
1012
0.99989
1. 63
X
10**
0.99903
1.31
X
1015
0.99985
8.32
X
1016
0.963C9
888
-------
a = 0.396R
2
TABLE VI
Descriptor Calculations
Polarizability
°r * MW
2 + •> d
n +2
r
Where: R ¦ Molar refraction
nr ** Refractive index
MW » Molecular weight (grams/mole)
d E Density (grams/cc)
Molecular Connectivity
(1) Assign valence values to each atom (discount the hydrogen atoms)
(2) Designate each bond in the molecule.
(3) Multiply the valence numbers of each atom involved in each bond.
(A) Take the reciprocal square root of the value obtained in Step 3.
(5) Add the individual values obtained in Step 4 to obtain the
molecular connectivity value.
889
-------
d
MW
1.3575
0.6262
72.0
TABLE VII
Example of Predictive Model
n-Pentane
Polarizability (a)
Therefore: (1.3575)2 - 1.00 72.0
R
(1.3575)2 + 2.00 0.6262
a - 0.3964R
and a ¦ 10.0
Molecular Connectivity (a) (x)
abed
C —C —C —C —C Where: a, b, c, d are the bonds
b -
(1.2)1/2
1
- 0.707
(2.2)1/2
1
= 0.500
(2.2)1/2
1
0.500
- 0.707
(1.2)1/2
Total ¦ 2.414 ¦ x value for n—pentane
TABLE VIII
Carbotrap Linear Regression Data
Adsorbate Class
Aliphatic hydrocarbons
Aromatic hydrocarbons
Alcohols
Chlorinated hydrocarbons
Ketones
Organic acids
Organic amines
Correlation Coefficient
0.99604
0.98414
0.99750
0.99162
0.99210
0.99130
1.00000 (2 adsorbates)
Total
0.98362
890
-------
TABLE IX
Comparative Linear Regression Data
Adsorbent Resin
Physical Descriptor Correlation Coefficient
Carbotrap
Tenax G.C.
XAD-2
o x X
a x X
a x x
0.95016
0.67481
0.84596
TABLE X
Illustration of the Predictive Model
Ethylbenzene
1. (a x x) value "¦ 55.59
Log (V|) = (0.0878) (a x x) + 2.3211
slope (x) + y-intercept
Log (v|) - (0.0878) (55.59) + 2.3211
= 7.2019
1.59 x 107
from experimental: V|
= 2.02 x 107
2-Chloroethanol
1. (a x x) = 11.6
2. The predictive model equation is:
Log (V|) - (0.0878) (a x x) + 2.3211
- (0.0878) (11.6) + 2.3211
- 3.34
V| = 1.09 x 103
from experimental: V| ¦= 0.87 x 103
891
-------
Adsorbate
n-Decane
Chlorobenzene
n-Pentanoic Acid
Benzylamine
Toluene
2-Butat\one
1-Butanol
2-Ethoxyethylacetate
TABLE XI
De6orption Efficiency Data
% Desorption Efficiency
Solvent Thermal
Acetonitrile Carbon Disulfide
IOC
111
93
113
110
103
111
108
109
102
111
108
109
105
106
102
116
104
102
109
892
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DEVELOPMENT OF DATA QUALITY INDICATORS
FOR TOXIC AIR POLLUTION MEASUREMENTS
Gary L. Johnson and Judith S. Ford
Air and Energy Engineering Research Laboratory
U. S. Environmental Protection Agency
Research Triangle Park, N. C. 27711
Traditional approaches to assessing the quality of data produced from air
pollution measurements have utilized data quality Indicators, which are
generally quantifiable. These data quality Indicators include precision,
accuracy or bias, completeness, representativeness, and comparability.
The determination of such data quality indicators is achievable through
the use of standard reference methods and certified reference materials.
The emergence of toxic air pollutants as a potentially significant envir-
onmental issue suggests that traditional approaches to determining the
quality of such measurements may not be effective or appropriate since
standard measurement methods and materials may not always be available.
Agency researchers are confronted with new measurement problems unlike
those encountered with conventional ambient or point source air pollution
measurements. This has led to the development of new measurement methods
for individual chemical species heretofore not addressed separately in
sampling or analysis. These species include inorganic as well as organic
chemicals. Since the characterization of toxic air pollutants cannot wait
for individual methods development work to be completed, conventional
measurement technology must be adapted. In like manner, traditional data
quality indicators must be adapted to describe the unique attributes
associated with the sampling and analysis of toxic chemical species.
893
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DEVELOPMENT OF DATA QUALITY INDICATORS FOR TOXIC AIR POLLUTION MEASUREMENTS
Traditional approaches to assessing the quality of data produced from
air pollution measurements have utilized data quality Indicators, which are
generally quantifiable. These data quality indicators Include precision,
accuracy or bias, completeness, representativeness, and comparability. The
determination of auch data quality indicators is achievable through the use
of standard reference methods and certified reference materials. The emergence
of toxic air pollutants as a potentially significant environmental issue
suggests that traditional approaches to determining the quality of such
measurements may not be effective or appropriate since standard measurement
methods and materials may not always be available. In addition, the broad
nature of the toxic air pollution problem makes the application of existing
methods uncertain in the absence of documented method performance for toxic
substances, which may be gas or particulate matter and may be present due to
a routine or accidental release.
U. S. Environmental Protection Agency policy requires that each data col-
lection activity conducted by or in behalf of the Agency shall have the qual-
ity of the data documented.I The documentation Is to be based on data qual-
ity indicators. In the emerging environmental problem area of air toxics,
Agency researchers are confronted with new measurement problems unlike those
encountered with conventional ambient or point source air pollution measure-
ments. These problems have led to the initiation of research to develop new
measurement methods for Individual chemical species heretofore not addressed
separately in sampling or analysis. These species Include Inorganic as well
as organic chemicals. Since the characterization of toxic air pollutants
cannot wait for individual methods development work to be completed, con-
ventional measurement technology must be adapted. In like manner, traditional
data quality Indicators must be adapted to describe the unique attributes
associated with the sampling and analysis of toxic chemical species.
This paper will discuss general approaches for developing or adapting
data quality indicators for toxic air pollutants measurements, including
gaseous organic chemicals and airborne particles, and the quality assurance
limitations or uncertainties associated with such measurements. The focus
will be on current methods being employed In the EPA engineering R&D program
directed at toxic air pollutant control and will provide guidance on test
program design, Quality Assurance Project Plan preparation, and the selection
of appropriate data quality indicators. It will not be possible, however, to
cover such a broad scope In great detail. Instead, we shall attempt to lay
out a road map for those Involved in air toxics measurements to follow and to
raise the level of awareness Eor the difficulties In applying quality assur-
ance and quality control to such measurements. Definitive conclusions, which
may be applied to every measurement activity, will be few in number because
the air toxics problem does not yield simple solutions. There will be several
recommendations for Improving our understanding of the problem and our confi-
dence in the quality of our measurements.
Nature of the Air Toxics Problem
Toxic air pollutants have been defined generally as virtually any sub-
stance released Into air media that may pose an exposure risk to human popu-
lation. By such a definition, toxic air pollutants also Include air quality
criteria pollutants, which are currently being regulated. The sources of
toxic air pollutants are widely varied and include traditional air pollution
sources, such as chemical plants and metallurgical processes, as well as
894
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non traditional sources now being identified in indoor air environments,
such as passive tobacco smoke and radon from soil gas. The exposure pathways
for the human population are equally diverse, Including industrial process
accidents such as that which occurred in Bhopal, India, and the routine
release of chemicals into the atmosphere as part of the normal operation of
countless human activities.
The diversity and uniqueness of the sources of toxic air pollutants
make the quantitative assessment of the nature and magnitude of existing
and future air toxics problems difficult. A more systematic examination
of the problem yields the categorization of air toxics Into routine releases,
accidental releases, and indoor air quality. The9e categories are defined
formally in Table I.
The nature of each category and the public perception of each varies.
For example, each category may differ In the type (e.g., acute, chronic) of
exposure most commonly encountered. Accidental releases contribute to acute
exposures of the human population generally and Indoor air quality to chronic
exposures. Nevertheless, there are several cross-cutting factors that may
affect all three areas. These Include a lack of adequate data to completely
assess the problem and uncertainty about the adequacy of current methodology
for sampling and analysis.
The routine operation of many industrial and energy processes may
contribute to human risk due to the normal discharge of toxic materials to
the air. Such routine releases may produce both acute and chronic effects,
depending on the quantity of material released and its toxicity. The
situation Is further complicated In that some materials may not have signi-
ficant toxicity when emitted, but may react chemically with other substances
in the ambient air to produce toxic materials. Moreover, the number of
potentially toxic chemicals is extremely large. Over 65,000 industrial
chemicals have been listed as having been in commercial production since
1945, many of which may be found to be toxic in relatively small concentra-
tions.
The impact of air toxics emission from routine releases Is not under-
stood clearly. In some situations, localized exposure to relatively low
concentrations of toxic substances may have been regarded as innocuous from
the perspective of acute health effects, but buildup of the substance in
the food chain or in tissue and organs may lead to chronic effects. Occupa-
tional health data are just now emerging Indicating that many current ailments
and deaths may have been attributable to exposures to chemicals, which 25
to 30 years ago were presumed to be safe. Furthermore, an insidious aspect
of this problem is the potential transport of these substances to other
areas. While the highest exposures have been found to occur near large
industrial point sources, emissions have been shown to disperse rapidly
downwind to affect areas not in the Immediate vicinity of the problem.
Direct emission of toxic substances alone is only part of the problem.
Atmospheric transformation of toxic precursors may pose significant risk
to the public as well.
While routine releases of air toxics may originate from almost any
human activity, the growth of ambient air toxics stems principally from the
growth of this country's industrial economy. Control and mitigation strat-
egies, employed since the early 1970s for criteria pollutants, have also
reduced somewhat the air toxics problem for traditional large sources, but
smaller, more widely dispersed industrial, commercial, and private source
emissions may contribute as much as 75% of the total air toxics cancer
incidence. In fact, there are Indications that the greatest contributor to
895
-------
air toxic cancer risk may be combustion products from mobile sources (e.g.,
automobiles, light duty trucks) and small stationary sources (e.g., home
heating).2 other, less generally recognized sources of air toxics Include
wastewater treatment systems (e.g., gas stripping, aerators, flocculators)
and solid waste disposal systems (e.g., incinerators).
The accidental release of toxic chemicals Into the air Is a problem from
the perspective of both prevention and emergency preparedness. The ability
to successfully deal with this problem depends on an understanding of the
true extent of the problem, its causes, the risks it poses to human health
and the environment, and an understanding of all current measures to address
It. The memory of the accidental release of methyl isocyanate (MIC) in
Bhopal, India, and the subsequent deaths of more than 2000 people, is still
fresh. Shortly after Bhopal, a similar, but more limited, release occurred In
Institute, West Virginia, which produced no fatalities, but led to the evacua-
tion of a number of people living In the immediate vicinity of the plant.
Both incidents served to Illustrate the inadequacy of some current prevention
techniques and emergency preparedness measures.
As is the case with routine releases, few data are available on
the effects in the ambient air, both In terms of individual chemical species
and mixtures of chemicals in which complex interactions may occur to produce
other toxic species. However, data are available on the health effects
of some chemicals. In particular, chemicals, which must be registered or
have their use approved under legislated authorities Issued to government
agencies (e.g., FDCA, FIFRA), generally have some health effects data available.
Just how relevant such data may be to the ambient environment is not certain.
The emergence of indoor air quality as an environmental concern repre-
sents a departure from traditional concerns, yet even the limited data now
available suggest that Indoor air pollution may pose a greater human health
risk than toxics In the ambient air. Many of the same toxic substances found
In the ambient air may also be found Inside buildings, and sometimes at the
same or higher concentrations. Federal, State, and local health authorities
are being called upon with increasing frequency to investigate perceived
indoor air quality problems, and public awareness of Indoor air problems,
particularly in regard to radon from soil gas, Is very high.
The indoor air environment presents a unique microcosm of the ambient
environment that appears to be considerably more complex than the outdoor
environment. The exposure to toxic materials may be acute in some cases,
like radon and Its progeny (or products of radioactive decay), but it is
generally regarded as being more chronic. The critical aspect of the debate
on whether ambient toxics or indoor toxics pose the greater health risk may
be consideration of the fact that most people spend more time Inside a home
or building than they do outside In the ambient air. One study for the
Electric Power Research Institute suggests that people may spend as much as
30-90% of their time Indoors.3
The causes of indoor air quality problems are many-fold, but a clear
cause is the trend to better Insulated, "tighter" buildings and homes to
improve energy efficiency.^ It has been found that reduced ventilation la a
very effective means of reducing energy costs. In the case of homes, venti-
lation Is the means by which indoor air pollutant concentrations are
generally reduced. Most ventilation occurs naturally through open windows.
When windows are closed in the heating and cooling seasons, homes are venti-
lated only by Infiltration, or unintentional leakage of air through cracks
around windows and doors and leaks In the building frame, driven by a wind-
created partial vacuum around the house and Indoor/outdoor temperature
896
-------
differences. This enables toxic pollutants in the ambient air to enter the
home and remain for long periods due to infrequent air exchanges. This
will add to the pollutant concentrations contributed by indoor sources.
The same applies to office buildings and other non industrial buildings where
energy conservation efforts have largely reduced air exchange rates signi-
ficantly.
Thus, the scope of the air toxics problem covers all potentially haz-
ardous materials that may impact human health through airborne transmission.
The measurement of air toxics involves virtually all types of currently used
air sampling methods. In most situations, the quality assurance/quality
control (QA/QC) techniques will be unchanged, but the measurement activity in
terms of classic data quality indicators may be difficult to document. To
place the problem in the perspective of data quality, it Is necessary to
discuss the traditional data quality indicators and then place them into the
context of air toxics measurements.
Traditional Approaches to Data Quality Indicators
Traditional indications of data quality include precision, accuracy (or
bias), representativeness, completeness, and comparability, which are often
abbreviated PARCC. Consequently data quality objectives have been expres-
sed in terms of PARCC, which are defined in Table II. It is EPA policy that
all measurement related activities will have their data quality objectives
documented in a Quality Assurance Project Plan. That is, a written plan
must be developed that will set forth the objectives or criteria by which
the quality of the technical results will be judged. In this way, the QA
Project Plan may be utilized to develop a test program with the necessary
quality checks to ensure that the data generated are defensible and are
adequate for the original intended use of the data.
The Intended use of the data is the key criterion from which all data
quality criteria or objectives are derived. For most routine measurements,
the state-of-the art methodology is such that data quality indicators (e.g.,
PARCC) may be readily determined. For air toxics measurements, the applica-
bility of PARCC as data quality indicators is not so clear. Hie suscepti-
bility of these measurements to external perturbations may make the speci-
fication and determination of PARCC values difficult.
For example, some air toxics exist in the form of particulate matter.
It has been shown that precision and accuracy are often difEicult to deter-
mine for particle size measurements.^ Precision presumes that sampling or
analysis conditions be relatively well-defined. Accuracy requires that a
known "true" value be available in the form of a standard reference material
(SRM) or, more importantly, a Certified Reference Material (CRM). An SRM
is a sample of the species of Interest in which a known amount Is present.
A CRM is similar, but it has been carefully assayed and documented by a
qualified organization, such as the American Society of Testing Materials or
the National Bureau of Standards.
Traditional data quality indicators are frequently associated with
Reference Methods, such as EPA Method 5, for total particulate matter deter-
mination. Such methods have been tested thoroughly in numerous validation
and verification activities, and are well documented in terras of the expected
performance of the method (e.g., precision, comparability). The same applies
to reference methods developed for chemical analysis in which expected per-
formance data may also be well documented. Even where reference methods are
not available, the use of Standard Operating Procedures (SOPs) will frequently
yield documentable data quality performance.
897
-------
In these discussions, some of the data quality indicators (i.e., preci-
sion, accuracy, comparability) have been discussed from the perspective
of how each pertains to a "standard," either a standard method or reference
material. The two remaining indicators, representativeness and completeness,
pertain more to the adequacy of the test design. The key to success here
lies in adequate study and planning of the test procedure; for example, the
technical objectives, the intended use of the data, consideration of outside
influences that could adversely impact the data. A good understanding
of the nature of the source and the technical objectives of the measurements
vrill enable realistic objectives for representativeness and completeness to
be defined.
As noted above, data quality indicators are utilized to establish the
data quality (i.e., QC) objectives for the test activity. These objectives
establish the quality expectations of the measurement results necessary to
satisfy the Intended use of the data. That is, how "good" the data have
to be in order to have adequate confidence that the technical objectives have
been met. These QC objectives, therefore, become the measure of success for
the quality of the measurements. When the testing has been done, the quality
control results may be compared to the QC objectives to determine how success-
ful the QC techniques were. In this way, the data quality achieved may be
evaluated in the context of the original QC objectives. Since measurements
are not always performed flawlessly and since unplanned problems may occur,
the data quality indicators are helpful in assessing the value of the product
data.
Traditional data quality indicators (i.e. , FARCC) are used routinely in
criteria pollutant programs. With the exception of particle size measure-
ments, measurements for criteria pollutant programs are well-defined and
usually supported by the availability of reference methods and certified
reference materials. In the case of air toxics, the problem becomes much
broader and the applicability of traditional QA/QC techniques must be
re-examined.
Applicability of Data Quality Indicators to Air Toxics Problems
Since air toxics can include virtually any potentially hazardous
material, either gas or particle, the measurements problems, and, conse-
quently, the QA problem, becomes magnified. Considerable work, has already
been done to address the air toxics measurement problem, primarily by
adapting existing techniques. Since a large fraction of air toxics sub-
stances are organic chemicals, efforts to reliably collect, extract, and
analyze these substances have increased.^ Also, some air toxics,
particularly metals, exist as particulate matter in the ambient air. The
QA problems associated with particle size measurements have been documented.5
Since the sampling methodology is independent of the chemistry of the part-
icle, the QA concerns apply to all particulate air toxics. The most signif-
icant concerns are the lack, of a reference method for particle size measure-
ments and the inability to reliably redisperse standard aerosols to check the
accuracy of the existing measurements.
In general, it may be said that the lack of standard reference methods
and materials constitutes the biggest problem for air toxics QA. There are,
however, things that can be done to reduce the Impact of the problems. First
of all, routine releases and accidental releases are the ones most like tradi-
tional criteria pollutant measurements from the standpoints of the types of
sources, the phase (gas or particle) of the sample, etc. Clearly, added
safety measures need to be employed in Some situations, but the sampling and
analysis methodology are largely unchanged. That is, samples are collected,
898
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good sample custody procedures are followed, the samples are analyzed, and
the results are determined. The Impact of the data quality may be Increased
depending on the known certainty In the method performance and the avail-
ability of a known value to check that performance. The use of SOPs will
greatly reduce the uncertainty In the results. This recognizes that while
SRMs are not as definitive or defensible as CRMs, they are, when properly
prepared, excellent tools to document the quality of the method.
In the case of Indoor air quality, the applicability of existing measure-
ment techniques Is less clear because this Is a relatively new environmental
concern and measurement technology Is still emerging. The sources of indoor
air toxics, as noted earlier, are varied In nature and are clearly non tradi-
tional from the standpoint of the Agency's historical perspective, especially
in the cases of radon from soil gas and passive smoke from tobacco combustion.
Measurements methodology research is Increasing for both organic and Inorganic
chemical species.^ The focus, however, has been on vapor—phase organics.
At present, no reference methods are specifically approved for
Indoor air toxics measurements. While CRMs exist for a number of organic
carcinogens and pesticides, no CRMs are currently available that reflect the
mixture of compounds that may be found typically in the indoor air environ-
ment. Thus, the uncertainty associated with the quality of indoor air may be
greater than that for routine or accidental releases.
In order to quantitatively assess the applicability of the traditional
data quality indicators to air toxics measurements, It is necessary to examine
each PARCC component individually. At the same time, the limitations and
needs can be highlighted.
Precision
While there are a number of methods with potential applicability to air
toxics, most are untried or unproven for the wide range of chemical species
found In the air toxics arena. Furthermore, many methods are unproven at the
low concentrations typically found In the indoor air environment and, In some
cases, In the ambient outside air due to routine releases. Caution must be
used In applying these methods until such time as additional research can
document their performance. If the Agency pursues a strong regulatory air
toxics program, then additional reference methods may be required to ensure
compliance. In the short term, more effort Is needed to document and Improve
the precision of existing and emerging methods.
Accuracy determination depends on the availability of a "true" value.
While CRMs (and SRMs) exist for many compounds, the breadth of the potential
air toxics Inventory (more than 60,000 chemicals) underscores the need for
additional reference materials. The use of standard reference materials
should be mandatory, but the appropriate organizations can be encouraged to
expand the available Inventory of CRMs. Again, this Is very important for
enforcement considerations, should they become necessary.
Also, the difficulty associated with determining the accuracy of particle
size measurements cannot be understated. In such cases, a quantitative measure
of accuracy will not be possible, but the careful, comprehensive documentation
of the test activity, Including the QC techniques employed, will help to give
a semiquantitative or qualitative assessment of the data quality achieved.
899
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Representativeness
Representativeness may be particularly difficult to determine for air
toxics. The possibility of interferences from chemical transformations In
the air toxic "soup" is high. This may be countered somewhat by Increasing
the available knowledge about the source, but such may not be practical
during early source characterization efforts. Moreover, it may be risky to
view representativeness as having a broad application beyond that of a specific
source. That is, the complexity of the air toxics problem may allow samples
to be representative of a unique source and not of a larger population of
sources. Representativeness must be defined In terms of the intended use of
the data.
Comparability
As just described above, the uniqueness of air toxics sources may make
meaningful comparability determinations difficult. Again, It is necessary
to have a good understanding of the nature of the source and the intended
use of the data in order to define comparability requirements.
Completeness
Completeness Is the PARCC component least affected by air toxics appli-
cation. The principle Is unchanged: collect enough valid data to ensure
confidence in the quality of the results. This must be done in the planning
stage, and It must Include an awareness of the method and its limitations,
and the intended use of the data.
Traditional data quality indicators may be used in many instances to
describe air toxics measurements, but there will be situations in which a
more qualitative discussion will be needed. In every situation regarding
air toxics measurements, the intended use of Che data should be the driving
force for the data quality indicators. In the long term, additional reference
materials and reference methods will be needed to adequately document the
data quality for air toxics measurements. In the short term, the adaptation
of existing methodology to air toxics problems and the emergence of new
methodology must be examined meticulously from a data quality perspective
to ensure that adequate quality documentation is achievable. The applica-
bility of traditional data quality Indicators in this short term may be
difficult to accomplish. It may be necessary to provide expanded narrative
documentation in order to convey to the user of the data an adequate confi-
dence in the data themselves.
These principles apply equally to the full scope of air toxics emis-
sions: routine releases, accidental releases, and indoor air quality.
Methods differ and sources differ, but the measure of the data quality
adequacy remains unchanged. As our knowledge and understanding of the air
toxics problem grow, our ability to document and defend air toxics measure-
ments will grow as well.
900
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References
1. U. S. Environmental Protection Agency, EPA Order 5360.1, "Policy and
Program Requirements to Implement the Mandatory Quality Assurance
Program," (April 1984).
2. E. Haemlsegger, A. Jones, B. Steigerwald, V. Thomson, "The Air Toxics
Problem in the U. S.: An Analysis of Cancer Risks for Selected Pollutants,"
EPA-450/1-85-001, NTIS PB 85-225175/AS (May 1985).
3. Electric Power Research Institute, "The Dynamics of Indoor Air Quality,"
EPRI Journal, JU:2 (March 1986).
4. J. L. Repace, "Indoor Air Pollution," Environment International,
j»:pp 21-36 ( 1982).
5. G. L. Johnson, C. E. Tatsch, "Quality Assurance Considerations for
Particle Size Measurements," Proceedings: EPA/EPRI Symposium on the
Transfer and Utilization of Particulate Control Technology.
(in press, 1986).
6. R. G. Merrill, R. S. Steiber, R. F. Mart?., and L. H. Nelras, "Screening
Methods for the Identification of Organic Emissions from Indoor Air
Pollution Sources," Atmos. Env. (in press, 1986).
7. W. G. Tucker, "EPA Research on Indoor Air Quality," Paper No. 86-11.5,
Air Pollution Control Association National Meeting, Minneapolis, MN
(June 1986).
901
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TABLE I. Air Toxics Categories and Definitions
Routine Releases
Emissions to the ambient air that occur
as part of the normal operation of human
activities, such as the operation of an
industrial process in which an exhaust
gas is discharged to the atmosphere.
Accidental Releases
Indoor Air Quality
Emissions to the ambient air, which occur
as an unplanned discharge, such as the
rupture of a storage tank or a process
upset.
Ambient air inside a building or home
as opposed to the outside air.
Table II. Definition of Traditional Data Quality Indicators
Precision
A measure of the mutual agreement among
individual measurements of the same
property, usually under prescribed
similar conditions.
Accuracy
The degree of agreement of a measurement
(or an average of measurements) of a
parameter with an accepted reference or
true value.
Representativeness
The degree to which data accurately and
precisely represent a characteristic of
a population, parameter variations at a
sampling point, a process condition, or
an environmental condition.
Completeness
A measure of the amount of valid data
obtained from a measurement system in
terms of the amount that was expected
to be obtained.
Comparability
A measure of the confidence with which
one data set can be compared to another.
902
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INDEX
Adsorpt ion
Carbon Monoxide
71, 275, 882
736
Aerosol
Case Study
95, 287
755
Afterburners
Catalyst
230
780
Agenc ies
Certification Standards
627
724
Air Exchange Rate
Charcoal
86
71, 674, 764
Air Flow
Chemical Mass Balance
239
500
Air Toxics
Chlorinated Compounds
351, 385, 513, 893
156
Aircraft Measurements
Chlor ine
375
701, 804
Alkalinity
Collocated Sampling
615
522
Ambient Monitoring
Comparative Data
176,205,326,330,33 5,364,431,442,
419
476,522,554,594,627,764,834,845
Computer Applications
Ammonium Sulfate
275, 467, 488
865
Convers ion
Analytical Methods
304
36, 467, 522, 534, 639, 748
Cos t
Aqueous Extraction
639
615, 701, 856
Cryogenics
Art i fact
385, 431, 442
71, 615
D
Data Logger
Asbestos
724
12
Data Bases
Atomic Absorption
128
817
Denuder
Aut oraation
156, 522
275, 764, 865
Depos i tion
Back Trajectories
304, 856
304
Detect ion
Benzo(a)pyrene
651, 780
554
Detector Tube
Bias
95
627
Diesel Exhaust
Bioassay
250
1
Dioxin
Blind Samples
239, 554
62 7
Direct Measurement
Boron
834, 845
304
Dry Purge
Building Materials
674
86
E
Electron Microscopy
Cadmium
534
817
Emergency Response
Canister-Based Sampling
330
402, 431
903
-------
Emerging Technology
1
Emission Factors
128
Eat itnat ion
513
Ethylene Oxide
755
Evaluat ion
156, 217, 817
Exposure Study
458, 513
Extractive Sampling
574
p Fabric Filtration
205
Field Evaluation
146, 402, 713
Field Study
522
Flue Gas
574
Flux Chamber
662
Fog
168
Furans
554
(5 Gas Chromatography
71, 287, 314, 326, 330, 335, 385
467, 476, 674, 780, 826
Gasoline
385, 458
Germany
230
Glass Beads
71
Halogens
701
Hazardous Air Pollutants
230
Hazardous Chemicals
651
Hazardous Emissions
662
Hazardous Waste
574, 639. 662
Hazardous Waste Fuel
701
Health Effects
351, 513, 826
Hexachlorobenzene
156
Hi-Vol Filters
615
HPLC Analysis
259, 269
Hydrocarbons
335, 375, 419, 500, 780
Hydroxyl Radical
500
| In situ Sampling
724
Inc inerat ion
230, 542, 574
Indoor Air Quality
1, 36, 45, 86, 104, 116, 128, 736
893
Industrial Emissions
351
Industrial Waste
230
Information Systems
128
Information Theory
476
Instrumentat ion
239, 275, 542, 834
Integrated Air Samples
431
Intercompar ison
45, 522
Ion Chromatography
701
L Light Absorption
845
Linearity
780
M Manuf actur ing
351
Mass Spectrometry
467, 476, 594, 674, 817
Maximum Allowable Concentration
95
Measurement Methods
1, 16, 275, 755, 792
Memory Effect
71
Me t a1s
554
Method Development
792
Methylene Chloride
826
Microorganisms
36
904
-------
Mist
574
Mixtures
467
Mobile Laboratory
594
Models
304, 882
Molecular Characteristics
882
Multi-City Study
419
Multivariate Data
488
Network Design
176
Sew Jersey
351
N'itro-PAH
259, 269
Nitrogen Compounds
522, 875
Nitrogen Dioxide
61, 834, 845
Non-Steady State Processes
755
Noncriteria Pollutants
335, 804
Nonindustrial Boiler
701
Nonmethane Organic Compounds
375, 419, 431, 442, 458
Odors
351, 594
Office Environment
36
Oregon
713
Organics
86, 134, 168, 287, 431, 476, 554, 639
Orifice Meter
239
Oxalic Acid
875
Particle Distribution
168
Part iculates
250, 259, 269, 287, 522, 542, 724
736, 856
Passive Sampling
61, 275
Passive Smoking
16, 25
Pattern Recognition
476
PCBs
205, 554
PCDDs
217
PCDFs
217
Performance Testing
12, 627, 724
Pesticides
168
Petroleum Refineries
500
Phase Distribution
146
Philadelphia
335
Photochemistry
287
Phthalatea
554
PM-10
792
Polycyclic Aromatic Hydrocarbons
146, 250, 304
Polyurethane
205
Potassium
748
Precision
442, 627, 780
Products of Incomplete Combustion
674
Programmable Sampler
724
Pulp Bleaching
804
Purge and Trap
674, 764
Q Quality Assurance
364, 522, 893
Quality Control
176
Quinones
259
p Raman Scattering
651
Real-Time Measurement
542, 594
Receptor Modeling
304, 500
905
-------
Redact ion
780
Reference Methods
780, 817, 893
Res idences
104, 116, 128
Residential Heating
713, 736, 748
g Sample Degradation
431
Sample Storage
431
Saraplers
61, 156, 176, 217, 275
Sampling
134, 146, 217, 385, 402, 431, 574
Sampling and Analysis
128, 304, 364, 375, 458, 826
Sampling Protocol
36
Sampling Techniques
45
Selenium
304
Semivolatiles
134, 156, 176, 217, 724
Silica Gel
95
Smog
442
Soil
764
Solvents
500, 594, 882
Soot
314
Sorbent
71, 176, 335, 662, 764
Source Characterization
128
Source Measurement
792
Source-Receptor Relationship
513
Spect roscopy
651, 865
Stack Sampling
574, 817
State Implementation Plans
442
Stationary Source9
128, 764, 817, 826
Statistical Analysis
287
Study Design
116
Sublimation Sources
875
Submar ine
95
Sulfate
304
Sulfate Ion
856
Sulfur Compounds
522
Supercritical Fluid
250
Survey Analysis
25
Syringe Sampling
275
"J" Temperature Effects
662
Tennessee
104, 116
Thermal Desorption
71, 287, 314, 335, 351, 764, 882
Three-Dimensional Graphics
488
Threshold Limit Value
95, 594
Toxic Organic Compounds
45
Trace Elements
304
Tracers
304, 748
Transport
304
Trapping System
71
w Validation
764, 792
Variable Wavelength UV Detector
250
Vehicular Emissions
287, 500
Vinyl Chloride
326, 330
Visualization
488
Volat ile Organic Compounds
45, 86, 104, 314, 402, 594, 764,
780
906
-------
Volatilizat ion
134
yy Waste Oil
701
Water
764, 836
Wood Stoves
713, 724, 736, 748
907
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1, REPORT NO. 2.
EPA/600/9-86/013
3. RECIPIENT'S ACCESSION NO. __
PE8 7 1 827 13SAS
4. TITLE AND SUBTITLE
Proceedings of the 1986 EPA/APCA Symposium on
Measurement of Toxic Air Pollutants
5. REPORT DATE
April 1936
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
U.S. EPA1s Environmental Monitoring Systems Laboratory
and Air Pollution Control Association
B. PERFORMING ORGANIZATION REPORT NO.
9 PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Research and Development
Environmental Monitoring Systems Laboratory
Research Triangle Park, North Carolina 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
same as (9)
13. TYPE OF REPORT AND PEHIOD COVERED
14. SPONSORING AGENCY CODE
EPA/600/03
15. SUPPLEMENTARY NOTES
Published by the Air Pollution Control Association, APCA VIP-7
16. ABSTRACT
A joint conference cosponsored by the Air Pollution Control Association and the
Environmental Monitoring Systems Laboratory of the U.S. Environmental Protection
Agency, was held in Raleigh, North Carolina, April 27-30, 1986. The technical
program consisted of 95 presentations, held in ten separate technical sessions,
on recent advances in the measurement and monitoring of toxic and other contaminants
found in ambient and source atmospheres.
Presentations included: 1) Measurement of Indoor Toxic Air Contaminants; 2)
Measurement of Semi-Volatile and Volatile Organic Pollutants in Ambient Air;
3) Chemometrics and Environmental Data Analysis; 4) Acidic Deposition -- Nitrogen
Species Methods Comparison Study; 5) Measurement of Hazardous Waste Emissions; 6)
Measurement of Wood Stove Emissions; 7) Source Monitoring; and 8) General Papers
Related to Quality Assurance and Particulate Measurements.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATl Field/Group
IB. DISTRIBUTION STATEMENT
Release To Publi c
19. SECURITY CLASS {This Report)
Unciassi fi ed
21. NO. OF PAGES
20. SECURITY CLASS (This page)
Unciassi fi ed
22. PRICE
EPA Foim 2220-1 (R»». 4-77) cmvioui coition ii oiiolete
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