&ER&
United States
Environmental Protection
Agency
Environmental Sew
Laboratory
Triangle Perk NC 27711
EPA-600/2-79-004
January 1979
Research and Development
Evaluation of
Techniques for
Measuring Biogenic
Airborne Sulfur
Compounds
Cedar Island Field
Study 1977
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development. U S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR) .
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-79-004
January 1979
EVALUATION OF TECHNIQUES FOR MEASURING
BIOGENIC AIRBORNE SULFUR COMPOUNDS
Cedar Island Field Study 1977
W.A. McClenny, R.W. Shaw, R.E. Baumgardner,
R. Paur and A. Coleman
Atmospheric Chemistry and Physics Division
Environmental Sciences Research Laboratory
Research Triangle Park, N.C. 27711
and
R.S. Braman and J.M. Ammons
Department of Chemistry
University of South Florida
Tampa, Florida 33620
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, -NORTH CAROLINA 27711
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DISCLAIMER
This report has been reviewed by the Environmenal Sciences Research
Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
ii
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ABSTRACT
Sulfur in both gaseous and particulate form has been measured near
biogenic sources using new measurement techniques. The preconcentration
of gaseous sulfur on gold-coated glass beads followed by desorption into a
flame photometric detection for sulfur is shown to have a detection limit of
0.1-0.2 ng of sulfur and to allow for speciation of ELS, CHgSH and
(CH0)0S at low parts per trillion levels. Ambient levels of NO0 and O,,
o Z ft <3
were found to alter the molecular form of sulfur on the beads unless
scrubbed from the sampled air. A collection technique using tandem filters
is extended from earlier efforts on fine and coarse aerosol to include
collection of SO0 and H0S on chemically coated filters; these filters are
Z 6 <-r-
analyzed by X-ray fluorescence for sulfur content. Measurements of gases
evolved from biogenic sources reveal HgS and (CHo)oS as primary
components with significant diurnal variations. Recommendations for
further instrument development are given.
iii
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CONTENTS
Abstract iii
Figures vi
Tables ix
Abbreviations and Symbols x
Acknowledgements xv
1. Introduction • • • 1
2. Experimental Procedures . 3
The Cedar Island facility 3
Instrumentation 6
Measurement of ambient sulfur 11
Biogenic release of sulfur in gaseous form 37
Atmospheric background measurement of nitrous
oxide, Freon 11, and Freon 12 44
Atmospheric measurement of ozone and nitrogen
oxides 47
3. Results and Discussion 50
Gaseous sulfur compounds in ambient air 50
Participate measurements in ambient air 70
Biogenic release of sulfur in gaseous form 76
Atmospheric background measurements of nitrous
oxide, Freon 11, and Freon 12 86
Atmospheric measurements of ozone and nitrogen 90
4. Conclusions and Recommendations 92
Appendices
A — Natural sulfur in the atmosphere 102
B — Operating Characteristics of the Sulfur Monitor
Used at Cedar Island 105
References , 120
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FIGURES
Number Page
!
1 Cedar Island and Surroundings 4
2 Blockhouse, Mobile Van, Radar Antenna and Sound
at the Cedar Island Wildlife Game Refuge 5
3 Apparatus for desorption of preconcentrated sulfur compounds
to cold trap 16
4 Apparatus for transfer of sulfur compounds from cold
trap 16
5 Recorder trace of sulfur compounds desorbed from liquid
nitrogen cooled, cold trap after preconcentration step 17
6 Calibration curve for H2S by Bennett (EPA) 19
7 Typical 50^ scrubber tube 21
8 Comparison of permeation tube and thioacetimide standards 25
9 Calibration data for H2S, (CH3)2S, and CH3SH 27
10 Holder and filter assembly for Tandem Filter Pack 36
11 Environmental chamber for measurement of biogenic emissions 39
12 Monitoring Site B. Marsh adjacent to Lewis Creek 39
13 Monitoring Site A. Intertidal edgewater location near
blockhouse on Cedar Island 42
14 Monitoring Site C. Intertidal flats on Outer Banks 42
15 Tower study sites near Cedar Island blockhouse 52
16 Typical chart recordings from the gold-coated glass
bead analysis 53
17 Tower 1. Vertical concentration profiles of sulfur
compounds 54
VI
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FIGURES
Number Page
18 Tower 2. Vertical concentration profiles of sulfur
compounds 55
19 Tower 3. Vertical concentration profiles of sulfur
compounds 56
20 Tower 4. Vertical concentration profiles of sulfur
compounds 57
21 Tower 5. Vertical concentration profiles of sulfur
compounds 58
22 Sulfur dioxide and H2S content of the ambient air using the TFP
and x-ray fluorescence 71
23 Gas chroipatographic analysis of an air sample taken from
the environmental chamber at Site A-l. Dimethyl
sulfide is dominant 77
24 Gas chroipatographic analysis at Site A-2. Hydrogen
sulfide is dominant 78
25 Dimethyl sulfide content of environmental chamber samples at
Site A-l (edgewater) as a function of time . 79
26 Dimethyl sulfide content of environmental chamber samples at
site near Site A-l as a function of time 80
27 Dimethyl sulfide content of environmental chamber samples
(same as Figure 24) as a function of temperature 81
28 Dimethyl sulfide content of environmental chamber samples
(same as Figure 25) as a function of temperature 82
29 Total sulfur content of environmental chamber samples as
a function of time at Site B 84
30 Total sulfur content of environmental chamber samples as
a function of time at Site C 85
31 Typical gas chromatographic analysis of Freon 11 and
Freon 12 87
32 Typical gas chromatographic analysis of N20.
vii
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M u FIGURES
Number
33 A one day data recording of ambient NO and 03 concentrations ... 91
34 Total sulfur content of environmental chamber samples as a
function of flow rate through the chamber 96
35 Chamber concentration prior to study shown in Fig. 34 96
36 Comparison of results from stirred and unstirred
environmental chambers 97
37 Dimethyl sulfide infrared spectrum (960-1070 cm"1) 99
* * •
vm
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TABLES
Number Page
1 Instrumentation Utilization 10
2 Effect of N02 on H2$ Recovery 31
3 Effect of 03 on H2$ and (CH3)2S Recovery 32
4 Effect of Outdoor Air on (CH3)2$ Recovery ... 34
5 Tower Sample Data 62
6 Tower Samples at 20 Meters 65
7 Miscellaneous Samples 66
8 Percentage Composition of Reduced Forms of Sulfur 69
9 Elemental Analysis of Fine Particulate Fraction 72
10 Elemental Analysis of Coarse Particulate Fraction for
Dichotomous Sampler and Tandem Filter Pack 73
11 Nitrous Oxide Results using Gas Chromatographic-Electron
Capture Detection 89
12 Freon 11 and Freon 12 Results Using Gas Chromatographic-
Electron Capture Detection 89
A-l Principal Elements in the Global Sulfur Budgets 115
A-2 Steady State Global Atmospheric Sulfur from Natural
Sources 116
A-3 Rates of Natural Sulfur Evolution 116
IX
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LIST OF ABBREVIATIONS AND SYMBOLS
ABBREVIATIONS
AIB — Atmospheric Instrumentation Branch
atm -- atmosphere
cc — cubic centimeter
i
GIFS — Cedar Island Field Study
cm — centimeter
CSI — Columbia Scientific Instruments
DST — daylight savings time
EPA — Environmental Protection Agency
ERC — Environmental Research Center
FPD — flame photometric detector
ft — feet
g — gram
GPT — gas phase titration
H — high tide
hr — hour
ID — inside diameter
in -- inch
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LIST OF ABBREVIATIONS AND SYMBOLS
ABBREVIATIONS (Continued)
kW
L
1
m2
m3
max
MDL
min
ml
MT
MV
ng
nm
NSF-RANN
OD
ppb
ppm
psig
RH
— kilowatt
-- low tide
— liter
— square meter
— cubic meter
— maximum
— minimum detectable level
— minute
— milliliter
—• megaton
\
— maximum measured value
— nanogram
— nanometer
~ National Science Foundation — Research Applied to
National Needs
— outside diameter
— parts-per-billion
— parts-per-million
— pounds-per-square-inch^of-gravity
— relative humidity
xi
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LIST OF ABBREVIATIONS AND SYMBOLS
ABBREVIATIONS (Continued)
RS
RTF
sec
T
TFP
TS
TSP
UV
v/v
WD
WS
-- imseparated sulfur compounds in the sample released from
cold trap into the Meloy
-- Research Triangle Park
— second
— temperature
— tandem filter pack
— total sulfur
-- total sulfur particulate
— ultraviolet
— volume-per-volume
— wind direction
— wind speed
-- year
SYMBOLS
AuCl3
CC19F9
Lt £t
CC13F
CH3CHOHCH3
CH3CSNH2
-- gold chloride
-- Freon 12
-- Freon 11
-- isopropanol
•- ttoacetamide
xii
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LIST OF ABBREVIATIONS AND SYMBOLS
SYMBOLS (Continued)
(CH3)2S2
(CH3)2S
COS
CO
C2H4
C2H5SH
Cu(N03)2
HC1
H2S
H304P
NaCO3
NaOH
N(CH2CH2OH)3
NH3
NH4C1
NO
N02
NOX
N20
- dimethyl disulfide
- dimethyl sulfide
- carbonyl sulfide
- carbon monoxide
- ethylene
- ethyl mercaptan
- copper nitrate
- hydrochloric acid
— hydrogen sulfide
•- sulfuric acid
— phosphoric acid
•- micron
— sodium carbonate
•- sodium hydroxide
- triethanolamine
— ammonia
— ammonium chloride
— nitric oxide
— nitrogen dioxide
— nitrogen oxides
•- nitrous oxide
xiii
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LIST OF ABBREVIATIONS AND SYMBOLS
SYMBOLS (Continued)
O« — ozone
S — sulfur
SO2 — sulfur dioxide
iciv
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ACKNOWLEDGEMENTS
The authors wish to acknowledge the advice and support of Mr. R.K.
Stevens, Chief, AIB, who initiated the request for the study; the help of
Mr. C.A. Bennett and Mr. J.M. Bowennaster of the AIB staff in
performing monitoring tasks during the study; the cooperation and help of
Mr. Brohawn and Mr. Lewis, the Cedar Island representatives of the Fish
and Wildlife Service and of Mr. J. Roberts, Cedar Island Refuge Manager;
the advice of Dr. V. Aneja of Northrop Services concerning environmental
chambers and for providing the experimental data shown as part of Figure
36 and of Ms. D. Hitchcock on the nature of biogenic sulfur sources; and
the work of Ms. R. Barbour in preparing the manuscript.
xv
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SECTION I
INTRODUCTION
The Cedar Island Field Study (CIFS), conducted from August 22, 1977
to September 2, 1977, was a concentrated effort to monitor selected gaseous
and particulate species at an isolated location on the North Carolina coast.
Prototype instrumentation and newly developed measurement techniques
were used. The gold-coated glass bead technique (1) for the sampling and
preconcentration of volatile sulfur compounds was of particular interest:
the CIFS provided the first chance to evaluate this technique in a field
test. The use of a tandem filter technique (2) was also of considerable
interest as it has recently been adapted (3) to measure hydrogen sulfide
(ELS) and sulfur dioxide (SO^x as well as coarse and fine particulate.
The objective of the CIFS was to establish the status of
instrumentation development with respect to the volatile sulfur compounds
which are of biogenic origin as well as those gases which influence the
composition of biogenic emissions at receptor locations, e.g., ozone (Og).
Information pertaining to the elemental.., composition of particulate matter,
meteorological parameters, and the species of sulfur compounds emitted
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from nearby marsh areas were recorded so that variations in the ambient
mix of the sulfur compounds could be related to characteristics of the
particular air mass being sampled.
Many of the activities related to the GIFS represent learning
experiences for the AIB staff. These experiences will lead to a better
appreciation of the effort needed to launch a field study and to sustain a
concentrated monitoring effort in the field. Furthermore (and most
importantly), the performance characteristics of various instruments under
field conditions have focussed attention on instrumentation needs, resulting
in a set of recommendations for future initiatives. These initiatives should
help to better define the relationship between biogenic emissions of sulfur,
nitrogen, and carbon compounds, and the atmospheric loading of sulfate,
nitrate, and carbonate particulate.
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SECTION 2
EXPERIMENTAL PROCEDURES
THE CEDAR ISLAND FACILITY
The Cedar Island National Wildlife Refuge on the coast of North
Carolina was selected as the site for the summer 1977 field test. As shown
in Figure 1, the Refuge is adjacent both to extensive marsh lands and to
the sheltered waters between the Outer Banks and the North Carolina
mainland. Initial survey trips to the island confirmed that the area was
isolated from traffic and that adequate support facilities were available.
The stationary monitoring site on Cedar Island is shown in Figure 2.
Two areas were prepared for the field test. One of these was a room in
the blockhouse shown in Figure 2. The room was cleared and an air
conditioner was installed in anticipation of the intensive staff effort to
come. An area adjacent to the blockhouse was prepared for a mobile van
which was to house several air monitoring instruments. The van was
supplied with electrical power of up to 12 kW from the blockhouse.
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PAMLICO SOUND
MAINLAND
A2
SOUND
J I
miles
ATLANTIC
OCEAN
Figure 1. Cedar Island and surroundings - Lola is at 76° 17' 13" longitude and 34° 57' 30" latitude.
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171
CHEVROLET
Figure 2. Blockhouse, Mobile Van, Radar Antenna arid Sound at the Cedar Island Wildlife
Game Refuge
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Ambient monitoring was performed from both the blockhouse and the
van. Particulate and gas collection devices and meteorological equipment
were deployed in the yard surrounding the blockhouse. The antenna
structure shown in Figure 2 was used as a platform from which to sample
ambient sulfur compounds. Environmental chamber samples were taken at
Sites A, B, and C of Figure 1 to determine the composition of sulfur
compounds being emitted from the local land areas.
INSTRUMENTATION
The following instruments were used during the study:
1. Meloy SA 285 Total Sulfur Analyzer SN 6DO63: The SA 285 provides
for thermal control of the burner block, photomultiplier, and flow
control devices to achieve a stabilized flame and a detection limit of
0.5 ppb, i.e., twice the rms noise with a time constant of 0.7
seconds. Sample air is drawn continuously through the detector at a
controlled flow rate of 200 cc/min and hydrogen for the flame is
supplied at 190 cc/min. Some additional performance characteristics
are given in Appendix B.
2. Tracor 560 Gas Chromatograph with Flame Photometric Detector: The
Tracer 560 resolves H9S, SO0, methyl mercaptan (CH0SH), ethyl
tt Lt O
mercaptan (CgHgSH), and dimethyl sulfide ((CHg^S) using a column
(36 in long, 1/8 in OD of FEP Teflon) packed with 60/80 mesh
Chromosorb T coated with polyphenyl ether and conditioned
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with phosphoric acid (H3O4P). Using a column temperature of 60°C
and a flow rate of 100 cc/min of nitrogen carrier, a 10 ml sample
provides a sensitivity of 3 ppb for HgS, SO2, and CHgSH, and of 7
ppb for the remaining compounds, based on peak height.
3. Meloy SA 185 Total Sulfur Monitor: The SA 185 is a commercial flame
photometric detector (FPD) used to monitor sulfur compounds. It is
less sensitive than SA 285 and is used with a preconcentration
technique to detect ambient sulfur. The detection limit is 2 ppb with
a 5 sec time constant.
4. Columbia Scientific Instruments (CSI) Series 1600 Oxides of Nitrogen
Analyzer: The CSI Nitrogen Analyzer is new to the commercial
market. Several features such as temperature control of critical
orifices in the sample and
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6. Bendix Ozone Analyzer, Model 8002: This commercial O0 analyzer is
O
based on the chemiluminesence of Og and excess ethylene (C«H4).
The detection limit is 2 ppb with a 3 sec time constant.
7. Dasabi Ozone Analyzer, Model 1003-AH: This commercial Og analyzer
o
is based on the absorption of mercury resonance radiation at 2537 A.
The detection limit is 2 ppb with a 1 min digital update.
8. Climet Portable Meteorological Station, Model EWS: This instrument
measures wind speed, wind direction, temperature, and relative
humidity.
9. Manual Dichotomous Sampler: This sampler is used for particulate
collection and size fractionation in two ranges with the cut point
between fine and coarse particle fractions at 3.5 pm particle diameter
and the upper cutoff at about 20 pin.
10. Tandem Filter Sets: This sequence of four filters collects fine
particulate, coarse particulate, HgS, and SO2> See detailed
explanation in text.
11. Collection Tubes and Accessory Equipment for the Gold-Coated Glass
Bead Preconcentration Technique: This method is being developed by
Dr. R. Braman and Mr. M. Ammons of the University of South Florida
under the sponsorship of the National Science
-------
Foundation — Research Applied to National Needs (NSF-RANN) — to
measure ambient sulfur compounds with existing FPD instrumentation.
See detailed explanation in text.
12. Portable Calibration System: This system provides a double dilution
stage which gives low ppb levels using standard permeation tubes.
The system uses mass flow controllers to regulate air flow over a
temperature controlled permeation tube (first dilution) and through a
dilution stream (second dilution). A glass capillary allows a fraction
of air from the first dilution stream to mix with the second dilution
stream. This unit is one-of-a-kind made by the Research Triangle
Institute, Research Triangle Park (RTP), North Carolina, for the
Environmental Protection Agency (EPA).
13. Gas Phase Titration Apparatus for Nitrogen Oxides and Ozone
Calibration: The unit assembled for this field trip used electronic
flow controllers and gas mixing chambers. As suggested by Rehme,
et al. (4), it was used with a secondary standard NO cylinder.
<• *'
14. ^Portable Bag Samplers and Constant Flow Pump System: These were
used for sample collection on the gold-coated glass bead traps.
These instruments were used according to the schedule given in Table 1.
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TABLE 1. INSTRUMENT UTILIZATION
Instrument
AeroChem
Bendix 8002
Climet
CSI
Dasihi
Parameter
Measured
N0v + NHQ + . . .
A. O
°3
WSWD, RH, T
NO
NO
AlWrt
NOx
o
AUGUST SEPTEMBER
MTWTFSSMTWTFSS
22 23 24 25 26 27 28 29 30 31 1 2 3 4
~
—
Dichotomous
Sampler
Gold Beads H2S
Preconcentrator
Meloy 285
Tandem
Filters
TS-SO,
i
Fine
Tracor
so2
H2S,
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MEASUREMENT OF AMBIENT SULFUR
Both gaseous and particulate sulfur were measured during the CIFS.
Gaseous sulfur compounds were marginally detectable by direct, real-time
measurement techniques. Preconcentration techniques were used for a
more definative measurement. Particulate sulfur samples were collected on
filters over 24 hour sampling periods.
Gaseous Sulfur Compounds by Flame Photometry
The FPD is used routinely in ambient monitoring of sulfur gases.
The FPD is based on the reactions attendant to burning gaseous sulfur
compounds in a hydrogen-rich flame (5). One reaction leads to the
formation of excited sulfur which can de-excite with the emission of a
photon (300-450 nm). Separation of sulfur compounds on a gas
chromatographic column prior to analysis in the flame allows for speciation.
In commercial instrumentation an interference filter centered for maximum
transmission at 394 nm is positioned between the flame and a
photomultiplier and defines the instrument's response characteristics.
For the CIFS, the Meloy Model SA 285 was chosen as a total sulfur
monitor (see Instrumentation). Hydrogen sulfide and SO2 were detected
separately by using chemical in-line scrubbers supplied by Meloy.
11
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The Model 560 Tracer Chromatograph with an FPD was chosen for the
study. A gas chromatographic column similar to that described by
Stevens, et al. (6), separated the sulfur compounds. The column is
described under Instrumentation. The retention times for the column were
as foUows: H0S and carbonyl sulfide (COS), 1.3 min.; CHoSH, 4.1 min;
Lt O
(CH3)2S, 6.4 min.
M
Calibration was performed using permeation tubes of the individual
gases to be measured. The tubes were weighed on a Cahn electrobalance
to determine permeation rates at set temperatures. Both preliminary and
field calibrations were performed with a prototype portable calibration
system capable of generating less than 1 ppb of the sulfur gases at flow
rates required by the FPD instrumentation.
The zero air (carbon dioxide (CCv,) in air) used in calibration was
obtained from Scott-Marrian, Inc. and contained less than 1 ppb of SO2-
Both the zero air and calibration mixtures were humidified to a relative
humidity of 60-90%. Initial calibration was performed at the Environmental
Research Center (EEC) Annex prior to the CIFS and consisted of a
multipoint calibration of the Meloy SA 285 using HpS and a multipoint
calibration of the Tracor 560 for HgS using peak height and for (CHo)2S
using peak area. Hydrogen sulfide response on the Meloy SA 285 was
linear with a nearly constant sensitivity of 1.11 + .01 ppb/chart division for
H9S and of 0.91 + .01 ppb/chart division for (CH0)0S. These sensitivity
/ O ii
checks were consistent during daily span checks at Cedar Island from
12
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August 23 until September 1, and again following a 2-day study September
23 and 24. The Tracer 560 was initially calibrated in the laboratory and
checked in the field for HgS and (CHg^S. Gas chromotographic column
performance deteriorated during the study with a significant reduction in
sensitivity. The total sulfur minus the SO2 readings on the Meloy were no
more than 20% higher than the H2S plus (CH3>2S readings on the Tracor
560 during analysis of the emission products from Cedar Island marsh
areas, indicating the presence of some low concentrations of higher
molecular weight sulfur compounds.
Gaseous Sulfur Compounds by Preconcentration of Gold-Coated Glass Beads
The concentration of H^S and organosulfur compounds in ambient air
is often too low for direct detection by an FPD. However, the sulfur
compounds in a large volume of ambient air can be collected; they can then
be released from the collection surfaces in considerably less time than it
took to collect them. This method can be used to raise the sulfur
compound concentrations above the lower detection limit of the FPD - . The
original ambient air concentrations can then be estimated if the efficiency
of collection and of release are known and prior calibration is available.
Ammons (7) studied a variety of metal surfaces for collection of
sulfur-containing molecules and selected gold. Method development related
to the use of gold-coated glass beads as, a collection medium has
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been carried out at the University of South Florida under the direction of
Dr. R.S. Braman with the sponsorship of the NSF-RANN. Technical
information exchange between the groups at the University of South
Florida and EPA led to the use of collection techniques in the GIFS. The
GIFS was the first environmental study to test of the gold-coated glass
bead technique.
The sample collection of sulfur compounds using the gold coated glass
bead technique occurs when a measured volume of ambient air is pulled
through 1 cm ID quartz tubes packed with a 3 cm length of 60/80 mesh
gold coated glass beads held in place with quartz wool. Measurements with
the technique consist of five steps: 1) blanking of the collection tubes; 2)
collection of an ambient sample; 3) desorption of collected molecules from
the beads onto a liquid nitrogen-cooled, cold trap; 4) release from the cold
trap into a FPD; and 5) reblanking of the collection tube.
Blanking establishes the signal response from a "clean" collection
tube. Blanks taken before and after the collection and analysis of sample
air are averaged to obtain the zero response. The zero response varies
depending on the batch of glass beads being used and their previous use.
A typical blank for HgS during the GIFS was 1-2 ng/sample with an
uncertainty estimated at 0.1-0.2 ng/sample. Typical sample responses for
H0S were 5-10 ng/sample. No blank response for (CH0)0S and CH0SH was
L o Z o
evident.
14
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Ambient air samples were taken by attaching a small electric air pump
to the tube through a line containing a critical orifice. Samples of up to
30 minutes were taken at a flow rate of 2 1/min. After collection, the
collection tube was connected to a nitrogen-rcooled, cold trap as shown in
Figure 3. The U-shaped cold trap was packed for over half its length
with 60/80 mesh glass beads. Hydrogen gas was passed through the tube
at a flow rate of 100 cc/min and the tube was heated to 600°C by a coil of
20 gauge nichrome wire. At the end of a 5-minute period the desorption
of sulfur compounds from the tube onto the cold trap was complete. The
liquid nitrogen was then removed from the trap and nitrogen gas was
passed through the trap for approximately 20 seconds as shown in Figure
4. The trap was then heated and the trapped sulfur compounds desorbed
in order of boiling points. The nitrogen was vented to a "T" connection
at the intake to a Meloy SA 185. The total flow into the Meloy SA 185
consisted of the nitrogen and sulfur-free air supplied at the "T". A
recorder, Linear Instruments, Model 252 A, was used with the Meloy. A
typical output recorder trace for H2S, CHLSH and (CHL^S is shown in
Figure 5. The recorder also provided for integration of area under the
individual peaks.
Typical ambient concentrations encountered at Cedar Island were: H«S
= 80 ppt; (CH3)2S = 30 ppt; and dimethyl disulfide ((CH3>2S2) = 20 ppt.
Samples collected for 30 minutes at 2 1/min resulted in a sulfur loading of
8 ng HnS, 3 ng (CHo)2S, and 4 ng (CHjJrtS,,, as compared to an
uncertainty in the collection tube blank of 0.1-0.2 ng.
15
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DESORPTION
TO VARIAC
H2
AU-BEADTUBE
VENT
LIQUID N2
Figure 3. Apparatus for desorption of preconcentrated sulfur compounds to cold
trap.
TRANSFER
CLEAN
AIR
Figure 4. Apparatus for transfer of sulfur compounds from cold trap.
16
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(CH3)2S
I
HEAT ON
1 2
TIMEdninutesj
Figure 5. Recorder trace of sulfur compounds desorbed from liquid
nitrogen-cooled, cold trap after preconcentration step.
17
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Stated mathematically, the response "R" of the Meloy, assuming that
the photomultiplier signal is linearized with respect to sulfur gas
concentration, is such that:
R -x. FIEEAT, (Eq. 1)
where F is the collection rate of ambient air during a sampling period
"AT", LA is the ambient sulfur loading, and Ep Eg, and Eg are the
efficiencies of transfer from the ambient air to the tube, from the tube to
the trap, and from the trap to the Meloy, respectively. Ordinarily the
ambient air loading is determined by comparing the response (chart
divisions) to a calibration curve which was generated under controlled
conditions using the same apparatus. For example, if E, = E« = E« = 1 and
a calibration curve for H^S such as that shown in Figure 6 has been
obtained, a response of 20 divisions would indicate a tube loading of 6.5
ng. The ambient concentrations could then be estimated as 6.5 ng/FAT in
ng/1.
Several precautions must be taken to insure quality control of the
technique. Quantities-such as the efficiencies of transfer E,, E9, and EQ
1 £t O
as well as the flow rate F in Equation 1 must be checked. Calibration
concentrations must be checked to ensure that sulfur-free carrier gases
are used and that the calibration gas standard, e.g., the permeation tube,
is accurately characterized.
18
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V0
x!
<
tt
110
100
901
80;
70
601
50
40
30
20
10
0
I I I ! I 1 I | I I I I I I I I I I I I I I I
I I
I I L I I I I I I I I I I I I I I I I I I
•i--
10 12j 141
NANOGRAMS H2S ;
161 181
20i 22:
24(
Figure 6. Calibration curve for H9S by Bennett (EPA). HP refers to a Hewlett Packard
Integrator. *
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Sulfur Dioxide Scrubbers
Sulfur dioxide has the most potential to interfere in the detection of
reduced forms of sulfur and must be removed prior to trapping. This is
done using an acid-base reaction with glass beads treated with sodium
carbonate (NaCOg). Sulfur dioxide was found to be trapped by glass
beads treated with small amounts of NaCO0 while H0S and organosulfur
O ft
compounds were not trapped.
The design of the SO2 scrubber tubes together with the rest of the
preconcentration stack is shown in Figure 7. Some 5 grams of 80/120 mesh
glass beads were cleaned by acid washing, dried, treated with 8.4 mg of
NaCOQ per gram of beads, redried, and packed into the glass tubes.
O
These tubes were then treated with H2S at approximately 10 ppb
concentration which was passed through them for 30 minutes to condition
the tubes. The conditioning process avoids losing a fraction of the H^S in
the first several analyses.
The SO2 absorbing tubes were also tested for absorption efficiency by
the addition of 10-100 ng of SO9 while analyzing for passage of SO0.
z &
Suitably prepared SO0 scrubbing tubes pass less than 1% of the SOn, do
it Z
not absorb more than 1-2% of JUS or organosulfur compounds passed
through them, and have an estimated capacity of 500 liters at 10 ppb SO0
£
levels.
20
-------
FILTER HOLDER WITH I
GLASS FIBER FILTER I
I
II I I II
ll ^
_^
111 1 11
S02 SCRUBBER
. TEFLON* CONNECTOR ;
^ nrrn J
'
i/ n 1 1 ii
It I 111
II I I ik
AIR SAMPLING TUBE
Figure 7. Typical SOg scrubber tube.
-------
Particulate Filters
Sulfate particulates are also a potential interferent if they are allowed
to collect on the beads. As shown later in the text, the average loading
of particulate sulfur at Cedar Island corresponds to approximately 14 ng
for a 30-minute sample at 2 1/min. To avoid this type of interference, a
particulate filter was placed in front of the SO0 scrubber-collection tube
Ct
combination. Gelman Type A glass fiber filters were used throughout the
tests except for Tower studies 4 and 5 (as described later) in which 0.2
pm Nuclepore filters were used. The volatile sulfur compounds SO2, HgS,
CHoSH, and (CHo)2s were found to pass the glass fiber filters.
Preconcentration Tube Preparation
Preconcentration tubes were prepared using 60/80 mesh glass beads
(Varian Instruments, Inc.) and gold chloride (AuCL) prepared from gold
foil. The beads were washed with concentrated hydrochloric acid (HC1),
dried, and treated with enough AuCL to give approximately a 10% (wt.)
coating of gold metal after hydrogen reduction. The sampling tubes were
approximately 8 in long, including connectors, and were packed with
approximately 3 cm of coated beads.
Prepared tubes were put through blanking and efficiency tests prior
to use. Blanking consists of simply heating the tube while passing
hydrogen or a hydrogen-nitrogen mixture through for 5 minutes. Any
22
-------
residual sulfur is transferred to the cold trap and to the Meloy, as in a
standard analysis. If blanks are not easily reduced to a low value, the
tube is washed with a few miULIiters of concentrated HC1, washed with
water, and then reblanked. Blank values of 1-2 ng and sometimes lower
should be attainable although sulfate sulfur is often only slowly removed
from the tubes.
Gold-coated tubes may be used repeatedly. No specific test has been
conducted to confirm this, but some gold tubes have been used over fifty
times in laboratory experiments. Acid washing reduces the useful tube life
by loosening the gold coating on the beads.
Small pieces of organic matter on the tubes turn to carbon during
analysis and can absorb sulfur compounds if used again. Tubes can be
cleaned of carbon contamination by heating the tubes to analysis
temperature in the presence of oxygen. Organic compounds in air samples
apparently do not cause this type of interference.
In later work the glass beads were found to contain small amounts of
sulfur compounds which slowly reduce and produce the small blanks
encountered. The beads were also found to contain substantial amounts of
&
iron and zinc; compounds of these elements are generally removed in the
bead cleaning process with acid or by oxidation with oxygen while heating
the tubes to 700-800°C. Iron is a particularly troublesome interferent and
should be removed from all parts of the analysis system which encounters
the sample.
23
-------
Standards and Calibration
Two types of standards have been studied for calibration of the FPD
detectors used in sulfur air analyses and for determining the operational
characteristics of the analysis system. These are the permeation tube
standards of the type developed by O'Keeffe and Ortman (8), as well as
the aqueous solutions of thioacetamide (CH0CSNHg).
O ti
Thioacetamide in aqueous solutions was found to be a good
reproducible calibration standard for E^S. Stock solutions (approximately
2000 ppm) were diluted to 4 ppm and microliter sized samples of the latter
were injected onto gold-coated bead columns. The reproducibility of
thioacetamide standards was found to be + 4.9% relative for 21 samples of 16
ng H9S on five different gold tubes. A comparison of two gold tubes
£t
indicated no significant difference at the 80% confidence interval. Similar
reproducibility was experienced using permeation tubes as standards for
H2S, (CH3)2S, CH3SH, and SOg.
Ammonium chloride (NH^Cl) and sulfuric acid (H2SO4) were also
tested as standards. The thioacetamide was the most stable calibration
standard over a period of time. This standard was compared to weighed
permeation tube standards using the Meloy SA 185 detector in work at
Cedar Island. Figure 8 shows that both give approximately the same
calibration curve.
24
-------
16
12
UJ
v>
o _
Si 8
LU
cc
I
\ \
I PERMEATION TUBE STANDARD
• THIOACETIMIDE STANDARD
10
20
30
40
50
NANOGRAMS H2S
Figure 8. Comparison of permeation tube and thioacetimide standards.
25
-------
Figure 9 shows the calibration curve data obtained for HgS,
and CHgSH using U-trapped standards and the Meloy 185 FPD. Despite
the linearizer on the detector instrumentation, some curvilinear character
is observed in these calibration curves. This is not surprising since
fluorescence self absorption effects are involved and must be a function of
sample size.
Efficiency Tests of the Sampling System
All gold tubes tested for H0S retention from air at flow rates up to at
z
least 3 liters per minute show better than 99% efficiency under a variety of
humidity conditions between 50% and 95% relative humidity. Gold tubes do
exhibit a finite capacity for sulfur compounds. This is approximately
500-1000 ng depending upon the gold tube tested but related to the amount
of gold present. Since the gold tube preconcentration is intended for use
with sample sizes well below 100 ng, the sulfur capacity is not approached.
A similar capacity effect and efficiency was observed for (CHo)2S.
Several comparisons were made of HgS adsorbed by and removed from
the gold tubes versus the H2S evolved from the permeation tube dilution
system; no difference was noted. The agreement of the thioacetamide
standards to the diffusion tube standards also supports the H0S efficiency
z
observed. No losses of H9S, (CHQ)H0S, or CHQSH were noted on either
4 O Z O
the glass fiber filters or in the SO0 scrubbing tubes.
4
26
-------
ta
o
DC
O
= 2.0
0.4
ng ANALYTE
Figure 9. Calibration data for h^S, (CH3)2S, and
27
-------
Procedure for Sampling and Analysis
Several routine procedures for sampling and analysis were adopted.
Gold sampling tubes were reblanked prior to reuse and assembled with the
filters and SO2 scrubber tubes into sampling stacks. These were sealed
with laboratory paraffin film and stored until used. Sampling was timed by
stopwatch. Sampling stacks were calibrated for flow rates while attached
to the same pump used in sampling. Sample flow rates were found to be
reproducible within ± 5% relative over the several days of field sampling.
Gold tubes were analyzed as soon as possible after sampling. Tubes were
also reblanked directly after sampling. Data were obtained using an
integrating recorder and compared to the calibration curves for analyses.
Hydrogen sulfide, CHgSH, and (CH3)2S were reported in ng/liter and in
ppb by volume. Unidentified organosulfur compounds were analyzed using
the H2S calibration curve.
Effects of Nitrogen Oxides and Ozone
A sometimes ignored aspect of trace HJ3 analysis is the effect of O«
and nitrogen oxides (NO ) on the collection system used. From the known
" X
oxidizing nature of O,, and nitrogen dioxide (NO0) one would predict that
O ^
either should oxidize HgS and perhaps also some of the other reduced
forms of sulfur. Moreover, the amounts of Og and nitrogen present in air
are generally much larger than the HgS or other reduced forms of sulfur
present. Non-urban concentrations of NO2 and Og are in the 5-20 and
28
-------
5-50 ppb concentration range according to recent reviews (9). Since H2S
may be expected to be from 0.05-1.0 ppb, it is apparent that the oxidizers
form a substantial excess.
Preliminary experiments indicated that NO2 and €>„ oxidize sulfur
compounds trapped on gold surfaces while nitrous oxide (N2O) had no
effect. Nitric oxide does not appear to be an interferent although it
oxidizes to NO2 which is an interferent.
The effect of NO0 and (X on H0S and (CHQ)0S coUected on gold
Z o it o Z
tubes was studied in laboratory apparatus designed to produce low
concentrations of these gases. Nitrogen dioxide was supplied by a
syringe-driven apparatus and diluted by air. The NO2 concentration was
analyzed by the Saltzman (10), method. Ozone was produced at low
concentrations by a Welsbach Instrument Co. O3 generator and determined
by iodometric titration. Samples of HgS and (CHg)2S were pumped onto
blanked gold tubes from a dynamic gas sampling system employing
permeation tube standards. The tubes were then exposed to various
amounts of Og or NO2 and analyzed for sulfur compounds.
This type of experiment was carried out both with and without the
use of the SO2 scrubbing tubes to determine if the latter afforded
protection against the oxidizing compounds. Tables 2 and 3 give the
results of the two studies.
29
-------
Unprotected tubes lose HgS, probably as SOn displaced from the
tubes by the oxidizing agents which were present in amounts sufficient to
entirely saturate the absorption sites on the gold. Dimethyl sulfide is
altered in form to HgS. In both cases, the use of an SO2 trap reduces
the interference effects to an acceptable extent.
Similar experiments were carried out using outside air sampling at the
University of South Florida. Ozone was 30-50 ppb during the time of the
experiments; NO2 was not determined at the time. The outside air may be
considered an urban type air as the experiment was carried out in the city
of Tampa, Florida. The results, shown in Table 4, indicate that
unprotected tubes having H0S or (CHQ)0S on them exhibit losses if air
fL. \J Lt
samples exceed 24 liters in volume. This is in accord with laboratory
experiments which showed that the exposure of tubes to more than a few
micrograms of O^ caused losses of sulfur compounds or demethylation. Use
of SO2 absorption tubes afforded protection in the GIFS.
30
-------
TABLE 2. EFFECT OF NO ON HS RECOVERY
Tubes Not Protected
H«S present
11.5 ng
11.5 ng
11.5 ng
11.5 ng
11.5 ng
11.5 ng
11.5 ng
11.5 ng
HnS recovered
11.5 ng
6.9 ng
5.6 ng
1.4 ng
With
11.6 ng
10.4 ng
12.0 ng
5.2 ng
% NO,
100%
60%
49%
12%
SO2 Scrubber
101%
90%
104%
45%
, Concentration
t
20 ppb
28 ppb
43 ppb
140 ppb
25 ppb
12 ppb
105 ppb
138 ppb
NO« Amount
120 ng
430 ng
1060 ng
1710 ng
305 ng
824 ng
2600 ng
3420 ng
*The amount column is the product of the concentration expressed as ng/1,
the collection flow rate and the time of collection.
-------
TABLE 3. EFFECT OF O0 ON H0S AND (CHQ)0S RECOVERY
o Z o &
Tubes Not Protected3
H2S Present
11.5 ng
11.5ng
11.5 ng
11.5 ng
(CH3x2S Present
28.6 ng
28.6 ng
28.6 ng
28.6 ng
HLS recovered
10.5 ng
10.0 ng
8.6 ng
4.5 ng
(CHQ)0S Recovered
-------
TABLE 4. EFFECT OF OUTDOOR AIR ON (CH3>2S RECOVERY
Tubes Not Protected
(CH3)2S Present (CH3)2S Recovered %
Air Volume
Protected Tubes
Air Time
28.5 ng
28.5 ng
28.5 ng
26.5 ng
19.0 ng
5.0 ng
93%
67%
18%
24 1
48 1
143 1
10 min.
30 min.
60 min.
28.5 ng
28.5 ng
28.5 ng
38 ng
30.0 ng
28.5 ng
28.5 ng
32.5 ng
105%
100%
100%
86%
71 1
71 I
71 1
79 1
30 min.
30 min.
30 min.
33 min.
33
-------
Sulfur Loading bjr Filter Collection Techniques
The filter collection techniques employed at Cedar Island involved the
dichotomous sampler and tandem filter packs. The dichotomous sampler
divides the sampled particles by inertial impaction so that two size
fractions are developed: a fine and a coarse particle fraction. The sampler
is described in detail by Loo, et al (11). The tandem filter technique is
used to collect size ranges (2) and can collect H«S and SOg if specially
coated filters are added. The adaptation of the technique for H^S and SO2
collection is the result of work done by Shaw (3).
The Dichotomous Sampler
A manual dichotomous sampler (12) was put into operation from
August 23 to August 29 and run for 24-hour intervals starting at noon.
The sampler was about 30 yards from the blockhouse and in a grassy area.
The flow rate was 14 1/min. The filters used for both the fine and the
coarse particle fractions were Millipore FALP (Teflon). The filters were
weighed before and after exposure to determine the total suspended
particulate. An x-ray fluorescence spectrometer (12) was used to analyze
the elemental composition of the particulate collected on the filters.
34
-------
The Tandem Filter Pack
The tandem filter pack (TFP) consists of a series of filters, each one
of which extracts a component of the air stream passing through it. An
exploded view of the TFP holder and filter assembly is shown in Figure 10.
For the GIFS the first two filters in line (12 \im and 1 Hm pore diameter
Nuclepore) removed coarse and fine particles, respectively. The next
filter removed SO2> and the fourth and last HgS. The gas collection
filters were Millipore, FALP (Teflon) which supported thin layers of
triethanolamine (N(CH2CH2OH)3), isopropanol (CH3CHOHCHg),and water,
mixed with sodium hydroxide (NaOH) for collection of SO2 and copper
nitrate (Cu(NOg)2) for HgS. The SOg and HgS filters were subsequently
analyzed for sulfur by x-ray fluorescence. The x-ray fluorescence
analysis system used by AIB has a sensitivity to sulfur such that 1
microgram can be detected at a confidence level of 90%. This corresponds
to the sulfur loading obtained by sampling 1 ppb of either SO2 or HgS at 1
1/min for 12 hours. The absolute sulfur determination efficiency (collection
efficiency times x-ray analysis efficiency) has been shown to be 60% + 10%
for both H«S and SOo at relative humidities above 50% and at 20°C. An
exploded view of the TFP holder and filter assembly is shown in Figure
10.
The sampling rate was set at 1 1/min and samples were taken over
24-hour intervals. Two sampling units were used: one remained near the
block-house about 10 yards from the dichotomous sampler, the other was
used in those areas where bag and chamber samples were taken.
35
-------
w
FILTER ALIGNMENT
AIR STREAM
FILTER
FRAME
THE FILTER IN THE FILTER FRAME
Figure 10.! Holder and filter assembly for Tandem Filter Pack. Only two filter frames are shown although four
filters were used in the CIFS experiments.
-------
BIOGENIC RELEASE OF SULFUR IN GASEOUS FORM
i
Introduction
Biogenically released sulfur near the Cedar Island site contributes to
the sulfur loading measured on the Island depending on wind direction and
emission rates. An attempt was made to measure the biogenic sulfur
released by the nearby marsh and to relate the sulfur compound mix to the
compounds measured with the preconcentration techniques.
The problem of measuring biogenic sulfur release is complicated by
the fact that local environmental conditions affect biogenic activity and
make the assignment of emission rates and mix of emitted species based on
localized measurements questionable. The investigators consider the
results presented in this report as relevant only to the area in which they
were obtained. |
Environmental Chambers
Efforts to measure biogenic release from the Cedar Island marsh were
centered on the use of an environmental chamber. The chambers used in
the GIFS were enclosures which isolated a small area of ground so that
gases released biogenically were prevented from rapid dispersion by
prevalent winds and could be channeled into sampling bags for subsequent
analysis.
37
-------
Description of Environmental Chambers
The environmental chambers were similar to those described by Aneja
(13). However, to avoid cutting the grass over certain of the monitoring
sites, the air stirrer was detached. Figure 11 shows the chamber that was
used during the studies. The chamber frame is just a modified office-type
trash can. Windows were cut in the sides and top so that radiation could
enter. Teflon sheeting was attached to the inside so that the Teflon
surface and the area of ground covered by the chamber constituted an
air-tight system. Ambient air was continuously pulled through the
chamber from a small 1/4 in inlet in the lower section, and left the chamber
from a similar connection near the chamber top. The accessory equipment
shown in Figure 11 includes a pair of 12 volt batteries in series to power
the air pump (Brailsford, Model TD4X2) which is mounted on the rim of
the chamber. Flow rates through the air pump were periodically checked
with a mass flow meter (Sierra Instruments, Model 543). Soil and ambient
temperatures were measured with a thermister made by Yellow Springs
(Model 46 TUG).
To sample the air passed through the chamber, a Teflon bag was
attached to the pump outlet with a Teflon tube. The bag was filled and
then transported to the blockhouse site where they were placed outside the
blockhouse in the sunlight to prevent condensation of H0O. During
A
analysis a Teflon line was run from the bag, through a window into the
blockhouse, to a Meloy, Model SA 285, for analysis. An SO2 scrubber
38
-------
Figure 11. Environmental chamber for measurement of biogenic emissions.
Figure 12. Monitoring site B. Marsh adj=r-ent to Lewis Creek.
39
-------
made by Meloy was usually heated and placed in the sample line so that
the readings were total sulfur minus SO,,.
Sample integrity was of primary concern in the chamber experiments.
Losses of H0S and (CHQ)0S in the Teflon bags were measured during the
Lt O £
field study at 15% per hour and 5% per hour, respectively. These loss
rates were determined by putting known amounts of the two gases in bags
and taking two readings, an initial reading and a second reading after 3
hours. Dry air was used in the tests. Bag losses as well as memory
effects were of concern. In this regard, it was found that the bags had
to be flushed three times before a zero response could be observed on the
Meloy sulfur monitor. Continual inspection of the bags for leaks was
necessary to avoid spurious results.
Placement of Chambers
Chambers were placed in several locations for limited periods of time
(typically half-day periods) and in two locations for continual analysis
during 2-day periods. Order of magnitude variations in chamber
concentrations were observed from location to location, diurnal and
tidal-related variations were observed during the long term analyses.
The primary location for chamber studies is denoted as Site A in
Figure 1. Site A is along the edge of Lewis Creek. In this area intertidal
edgewater locations were chosen. The majority of the edgewater area (Site
40
-------
A-l) was overgrown with a type of marsh grass -- Spartina alterniflora —
and interlaced with seaweeds held in place by the stem and root systems of
the marsh grass. The soil was a mixture of silt and sand, tan to dark
brown in color. Site A-2 was located near a docking area which fronted
on Lewis Creek. This area was sandy with little grass or seaweeds.
Site B, as shown in Figure 12, is in the marsh adjacent to Lewis
Creek. It was selected as being more representative of the marsh area
than Site A (see Figure 13). Site C was chosen as representative of the
intertidal flats that border the sound side of the Outer Banks. These
flats are shown in Figure 14.
Calculation of Generation Rates
The assumption of ideal mixing in the environmental chamber
establishes the following relationship: the rate of release "R" of a sulfur
compound of gram molecular weight "G" from the area "A" covered by the
chamber is related to the flow rate "F" through the chamber and
concentration at the outlet "f". The equation goes as follows:
R(gm/m2-yr) = ^1 F(l/min) G(gm/mole) %&& C(min/yr), (Eq. 2)
A (nT) K (1-atm/mole-deg) T(deg)
where C = 5.256 x 105, A = 0.085 m2 for the chamber used in the CIFS, G
= 62 for (CH0)0S and G = 34 for H0S, and K = 0.082 1-atm/mole-deg. P
O Cl tt '
41
-------
Figure 13. Monitoring site A. Intertidal edgewater location near
blockhouse on Cedar Island.
Figure 14. Monitoring site C. Interdial flats on Outer Banks.
42
-------
is the atmospheric pressure and T the ambient temperature. Note that for
a constant generation rate the value of concentration is inversely
proportional to the flow rate, i.e., f(ppb) ~ [FU/min)]"1.
Equation 2 must be interpreted with care if it is to be used to
estimate the biogenic flux which would occur in the absence of an
environmental chamber. The main questions associated with the use of
chambers concern (a) the perturbation of the environment being monitored
by the chamber, e.g., the possibility of temperature and humidity changes
within the chamber; (b) the effect of increased partial pressures of the
gases to be measured over the area enclosed by the chamber; (c) the
degree of stirring required in the chamber; and (d) the tightness of the
air seal around the chamber. In the present case, ambient air was pulled
through the chamber so that humidity changes were minimized; however,
an increase in temperature was evident from the water condensation on the
chamber walls. The questions (b) and (c) above are discussed in some
detail by Hill, et al. (14). In the CIFS, sampling was performed over
grass, so that the chamber could not be stirred. Item d is important
when the sample air is being pulled through the chamber. In this case a
check should be made to determine if the flow rate entering the chamber
and that leaving the chamber are equal. To measure the combination of
the effects mentioned in (b) (c) and (d), the chamber concentrations were
recorded as the chamber flow rate was varied. The departure of the
43
-------
results from that given in Equation 2, i.e., f ~ 1/F, was taken as an
empirical determination of the applicability of Equation 2. The result of
this determination is given in Results and Discussion.
ATMOSPHERIC BACKGROUND MEASUREMENTS OF NITROUS OXIDE,
FREON 11, AND FREON 12
As part of the CIFS, five ambient samples were taken for subsequent
analysis to determine N2O, Freon 11 and Freon 12 content. The five
samples were all taken at the same time on September 1 and at the same
place (height of 7 m); they were expected to be replicates. The
containers were returned to RTF for subsequent analysis on November 8.
Due to the significant delay in analysis any differences in the results of
the separate container samples were expected to reflect the compromise of
sample integrity attendant to storage. The results were expected to
illustrate AIB's capability to analyze samples for N^O, Freon 11 and Freon
12 with a set of optimized gas chromatographic columns, and to provide
estimates of sample integrity after storage in sampling containers.
Development of better and more convenient analysis techniques seem
especially appropriate in the case of NgO, since it has been suggested that
the N20 level is constant and could be used as a reference to check
analytical instrument performance. The concentration levels reported,
however, have ranged from 0.25 ppm in 1974 to 0.32 ppm at the present
time. It is not clear whether this increase is due to a refinement in the
44
-------
measurement technique of a constant concentration level, or whether N2O
levels are on the increase in the atmosphere.
Accurate measurement of NgO, Freon 11 and Freon 12 is extremely
important since their presence in the atmosphere contributes to the
greenhouse effect — the blanketing action which leads to an increase in
the earth surface temperature (15).
Measurement Techniques
Gas chromatography with electron capture detection was used to
determine the Freons and N^O. The analytical system was comprised of a
Barber-Coleman Series 5000 Gas Chromatograph, an Analog Technology
Corp. Model 140 Detector, and a Carle 8-Port Sampling Valve with a 6-ml
loop and a Hewlett-Packard Model 3385 A Integrator. The halocarbon and
N2O analyses were done on separate columns.
Conditions for the determination of Freon 11 and Freon 12 were:
Column: 7 ft x 1/8 in Porasil C, 80/100 mesh;
Column Temp: Ambient;
Carrier: 5% methane in argon;
Flow rate: 41 ml/min at 22 psig;
Detector temp: 190°C.
45
-------
The conditions for the determination of NgO were:
Column: 8 ft x 1/8 in Porapak Q, 80/100 mesh;
Column Temp: Ambient;
Carrier: 5% methane in argone;
Flow rate: 32 ml/min at 25 psig;
Detector temp: 190°C.
A cursory study indicated that one analytical column, packed with
Chromosil 310, can be used for the determination of the above three
components. The column unfortunately was not ready for this project.
It will be used for such analyses in the future.
Calibration of the system consisted of recording responses to
reference mixtures. These reference mixtures (one component per
container) were composed in stainless steel cylinders by a method of static
pressures.
Evacuated containers were used for sampling: four steel containers
(800 cc each) and one stainless steel cylinder (500 cc). Each container
had been outgassed by heating and pumped down to a pressure of 20 urn
prior to use.
The containers were heated to 80°C in a drying oven in the
laboratory just prior to analysis in order to increase container pressure to
46
-------
about 21% above collection pressure. This maneuver provided two samples
per container.
ATMOSPHERIC MEASUREMENTS OF OZONE AND NITROGEN OXIDES
Ozone measurements at Cedar Island were expected to show some
correlation with ambient sulfur levels due to the H0S - OQ gas phase
£ O
reaction. Also, the availability of two types of O3 measuring
instruments - one based on Og - CoH. ch^ilunutti8061106 and tne other on
ultraviolet (UV) photometry -- made possible a comparison of techniques.
Measurements of NO were used as an indication of the isolation of
A.
the Cedar Island site. In addition a new commercial monitor, the CSI
Series 1600, was tested for sensitivity and reliability under field
conditions.
Measurement Apparatus
The O, instrumentation, Dasibi, Model 1003-AH, and Bendix, Model
8002, are established commercial instrumentation. The Dasibi is based on
UV photometry and a chemical scrubber system for Og. In operation the
sample stream either bypasses or passes through an Og scrubber and is
O
subsequently analyzed by the measuring attenuation difference at 2537 A.
The Bendix instrument causes mixing of the sample stream with a pure
stream of C2H4. The reaction of Og with C2H4 occurs with an attendant
47
-------
emission of photons. Photon emission as monitored on a photomultiplier
gives a signal proportional to the concentration of O3 in the sample
stream.
Measurement of Ozone and Nitrogen Oxide
Ozone and NO were monitored from a common manifold in the mobile
A.
van. The sample inlet line of 1/4 in ID Teflon tubing contained an in-line
Nuclepore filter of 5 [im pore diameter. Both O« monitors (Dasibi and
Bendix) as well as the CSI NO monitor were operated continuously.
X.
i
Calibration of Ozone and Nitrogen Oxides
The OQ and NOV calibrations are estimated to be better than + 20% for
o X —
the two week measurement period.
The Og calibration was based on UV absorption photometry. The
Dasibi (Serial No. 123?) and Bendix (Serial No. 302070-2) monitors were
calibrated at RTF prior to the field study. During the study the Dasibi
experienced an obvious intermittent electronic malfunction which allowed
only about 70% valid data from, the instrument. During the periods when
the Dasibi was functioning properly the Bendix and the Dasibi tracked
/
each other within ± 10% except for a brief period following excessive
condensation of ambient water in the sample lines. After returning the
instruments to RTF, the Dasibi did not function. The Bendix calibration
48
-------
was checked by the gas phase titration apparatus (GPT) and was found to
be approximately 3% high. Since 3% is less than the typical difference
between GPT and UV Og calibration, the instrument drift was considered
to be negligible (i.e. <5%).
The NO calibration was based on an NO cylinder (the cylinder
A.
concentration was determined by comparison to an Standard Reference
Material (SRM) cylinder via GPT. Immediately prior to'the field trip the
NO_ instrument (CSI, Model 1600, Serial No. 8195) was returned to the
A
factory for repairs and calibration. The calibration was checked at RTF
prior to the trip and was found to be within 2% of the factory value.
Similarly the converter efficiency was found to be within 1% of the factory
value (~ 98%). After the field study the instrument was returned to RTP
and the NO calibration was found to be ~ 6% lower. The converter
efficiency was not rechecked at RTP.
During the field study several attempts were made to check the
instrument calibration via GPT. None of these efforts produced results
within 30% of the instrument's response. Upon later examination of the
GPT system it appeared that the most likely cause for the field calibration
results was improper purging of the NO tank regulator. (The regulator
was removed from the tank during transportation both to and from the
field study site.) Because of the large deviation between the field
calibration results and the instrument response, no adjustments to the
instrument spans were made in the field.
49
-------
SECTION 3
RESULTS AND DISCUSSION
GASEOUS SULFUR COMPOUNDS IN AMBIENT AIR
Direct Measurements Using Flame Photometric Detection
Direct readings of ambient gaseous sulfur with the Meloy SA 285 were
taken during the first part of the field test. Total sulfur-sulfur dioxide
levels were always below 5 ppb. Due to the difficulty in distinguishing
values below 5 ppb with precision, the direct measurements were
discontinued.
Preconcentration on Gold-Coated Glass Beads
Several types of sampling studies were planned, including: sampling
of air coming from the ocean, sampling as a function of height above the
ground (tower studies), sampling and analysis as a function of time
(diurnal variations), sampling of biogenic emissions, and sampling in
support of other investigators. Each study was performed to some
50
-------
degree; however the time variation study could not be carried out over
more than a few hours because of difficulties in maintaining the sampling
tubes in a suitably blank condition. The placement of local vegetation and
wind direction appeared to have a substantial influence on the sulfur
analyses obtained.
Tower Studies
Air samples were obtained using a 10 meter high mast which could be
raised and lowered to attach sampling tubes and fittings. Small vacuum
pumps (Neptune Dyna-Pumps, Fisher Scientific Co.) were placed at the
foot of the towers and connected at various heights to the sampling tubes
by tygon tubing. Tower samples were taken at 10, 5, 2, 1, and 0.1
meters. Also available was an abandoned radar antenna tower from which
20 meter high samples could be taken. Five 10-meter tower sample sets
were taken in the course of the field work. Figure 15 depicts the various
tower study sites on Cedar Island. Figure 16 shows typical chart
recordings from the gold bead analysis. The label "RS" refers to the
unseparated sulfur compounds in the sample released from the cold trap
into the Meloy.
The distribution of reduced forms of sulfur is given in Table 5, A-F,
and shown in Figures 17-21 as a function of height above the ground.
Towers 1 and 2 were taken at a location as close as practical to the edge
of the sound. There were no mud flats at this location. Notable are the
51
-------
to
PAMLICO SOUND
PINE GROVE
Figure 15. Tower study sites near Cedar Island blockhouse.
-------
Figure 16. Typical chart recordings from the gold-coated glass bead analysis.
53
-------
10m
5m
2m
1m
0.1m
H2S 100%
H2S 96.5% DIMS I
J H2S 99
.7% R-S 0.3%
H2S 99.5% R-S 0.5
TOWER 1
(AFTERNOON)
J H2S 88.9% QMS 11% j I 1
0.5 1.0 1.5 2.0 2.5
ng S/liter
Figure 17. Vertical concentration profiles of sulfur compounds — Tower 1
54
-------
10m
5m
H2S 99% DMS 0.2 R-S 0.7
H2S 100%
2ml |H2S95%R-S5%
1m
0.1m
H2S 100% R-S tr.
I r
TOWER 2
(NIGHT)
1 H2s ii» |I I L
4 Oi 1.« 1-5 2.0 2.5
ngS/lher
Figure 18. Vertical concentration profiles of sulfur compounds — Tower 2.
55
-------
10m
5 m
2m
1m
0.1m
II 1 1
H2S 76.7 QMS 2.5 R-S 20.7% 1
TOWERT
(NIGHT)
j
| H2S 79% MeSH 6% DMS 6 R-S 9
^j~H2S f2% QMS 36% DMDS 18% R-S 34%
H2S 58% DMS 3.4% R-S 38% 1
""""I' H2S 12% ( DMS 30% R-S 58% j J
1
1
0.5 1.0 1.5 .2.0 2.5
ng S/liter
Figure 19. Tower 3. Vertical concentration profiles of sulfur compounds.
56
-------
10m
5m
1 1 1 r
H2S 38% DMS 23% R-S 39%
H2S 50% MeSH 6% DMS 6% R-S 33%
2ml I H2S 53% DMS 13% R-S 34%
1m
0.1m
H2S 44% DMS 12% R-S 37%
TOWER 4
(AFTERNOON)
H2S 93% DMS 7% I I I
0.5 1.0 1.5 2.0 2.5
ng S/liter
Figure 20. Tower 4. Vertical concentration profiles of sulfur compounds.
57
-------
10m
5m
I
I
H2S 67% QMS 5% DM PS 23 I
R-S 6%
H2S 54% QMS 6% R-S 40%
2m
1m
0.1m
H2S 26% DMS 9% DMDS 65%
H2S 61% MeSH 7% DMS 3% DMDS 8% R-S 18%
i r
TOWERS
(NIGHT)
H2S 65% DMS 21% R-S 14%
0.5 TO
Figure 21. Tower 5. Vertical concentration profiles of sulfur compounds.
58
-------
high percentage of HgS and the low percentage of other reduced forms of
sulfur. Towers 3-5 were taken in the open field near the blockhouse with
wind directions generally from the marsh area. All of these had a
substantially higher organosulfur compound content than those taken near
the sound.
A regular pattern of sulfur concentration was noted in most of the
tower studies with a maximum at 1 meter and with total reduced sulfur
concentrations increasing with the height above ground. Since the
maximum in concentration at 1.0 meters does not appear to be consistent
with either a dry deposition or biogenic emission of the sulfur gases, the
experiment must be repeated to judge whether this maximum is an artifact
introduced by the sampling train or is due to the micrometeorology of the
surrounding area. In any case the vertical variation points out the
problem of picking a representative vertical position for ambient air
sampling. Sampling at 10 meters was more indicative of an average sulfur
value; organosulfur compounds were very low at 2 meters, the usual
height for meteorological sampling.
Samples were taken from the radar tower located near the blockhouse
at a height above ground of approximately 20 meters. Results of analyses
are given in Table 6. Hydrogen sulfide was the major reduced sulfur
component in most cases. Very little contribution was noted from
organosulfur compounds. Some of the 20-meter samples were taken at the
59
-------
same time as the 10-meter tower studies. Comparison of the 20-meter and
10-meter tower samples, where feasible, shows substantial agreement in
composition and, generally, in the concentration of the reduced sulfur
compounds found.
A number of miscellaneous samples were taken with data given in
Table 7. These data include analysis of samples taken from several sites:
Site A, Site B, and Site C, as well as samples taken in the area of a pine
grove, and two measurements taken at Cox's Landing, North Carolina.
Discussion of Results Obtained Using Gold Coated Glass Bead
Preconcentrator
A comparison of ocean air samples to on-shore samples was made (see
Table 8). Ocean air samples were defined as air samples taken near the
.<
*.
waters' edge with wind from the ocean direction. On-shore samples were
defined as samples taken further inland with wind generally from the land
direction. On-shore samples and the pine grove samples all contained much
higher amounts of organosulfur compounds. This agrees with Rasmussen's
comments (15), that a number of different organosulfur compounds are
associated with biological sources.
During the development of the analytical method, the major objective
was to provide a method principally for HgS, CKLSH, and (CHo)2S; these
were satisfactorily separated in the U-trap. However, a much more
complex mixture of sulfur compounds was found (See Figure 16) and the
60
-------
unseparated, less volatile organosulfur compounds had to be reported as a
group. An improved separation method is now under study.
A gas chromatographic type of FPD air analyzer was in use during
the sampling of ambient air. Hydrogen sulfide was detected in ambient air
at concentrations in agreement with the preconcentration method described
here. Sulfur dioxide was detected at levels less than 5 ppb.
Consequently, the SO2 capacity of the scrubber tubes was not approached
during sampling.
The method has certain limitations. The sulfur compounds carbon
disulfide (CSgN and COS are interferents, since both appear as HLS after
absorption on the gold tubes and after hydrogen reduction. Although
some of these are removed by the SO0 scrubbing traps, an improved
It
separation technique is needed. In addition, some decomposition of
mercaptans to ELS was noted during hydrogen reduction and was generally
a function of the total amount present. No decomposition of (CH3)2S was
observed.
Finally, the method does have the capability of providing analytical
information on HgS and (CH3)2S found in air at ambient concentrations in
non-polluted locations. It should substantially aid studies of the
environmental chemistry of sulfur.
61
-------
TABLE 5. TOWER SAMPLE DATA
Height
m
10
5
2
1
0.1
10
5
2
1
0.1
]
ppb
0.94
0.59
0.26
0.6
0.24
0.90
0.41
0.19
0.88
0.02
(8-24-77,
2 ng/1
1.46
0.90
0.40
0.93
0.37
(8-25-77,
1.38
0.63
0.29
1.35
0.03
A . Tower
1650-1720 hr,
ppb
0.00
0.02
0.00
0.00
0.03
B . Tower
2140-2230 hr,
0.002
0.00
0.00
0.00
0.00
1
70-90 1)
(CH^
tr.
0.06
0.00
0.00
0.08
2
90-109 1)
0.006
0.00
0.00
0.00
0.00
RS
ng/1 as H2S
0.00
0.001
0.00
0.004
0.00
0.011
0.00
0.015
0.001
0.00
(continued)
62
-------
TABLE 5. (Continued)
C. Tower 3
(8-27-77, 2000-2030 hr, 67-90 1)
10
5
2
1
0.1
10
5a
2
1
0.1
0.70
0.71
0.01
0.80
0.015
0.60
0.73
0.097
0.65
0.23
1.03
1.04
0.01
1.23
0.02
(8-28-77,
0.93
1.13
0.15
1.58
0.35
0.24
0.036
0.28
0.050
0.038
D. Tower 4
1550-1650 hr, 40
0.40
0.092
0,025
0.19
0.017
0.062
0.095
0.73
0.13
0.10
D
1.04
0.24
0.065
0.49
0.045
0.28
0.07
0.037
0.81
o.n
0.95
0.88
0.098
0.99
0.00
(continued)
63
-------
TABLE 5. (Continued)
E. Tower 5
(8-28-77, 2000-2100 hr, 40 1)
10a
5
2C
ld
0.1
aCH3SH: 0
*(CH3)2S2:
(Cn.i))nSn'
d
(CH3)2S2:
0.58 0.90 0.046 0.12,
0.69 1.06 0.084 0.22
0.058 0.09 0.021 0.055
0.86 1.33 0.038 0.10
0.11 0.16 0.036 0.095
.20 ng/1
0.15 ng/1 as HgS
0.11 ng/1 as H2S
0.09 ng/1 as H0S; CHQSH: 0.21 ng/1
Lt O
0.78
0.80
0.00
0.48
0.04
64
-------
TABLE 5. (Continued)
C. Tower 3
(8-27-77, 2000-2030 hr, 67-90 1)
10
5
2
1
0.1
10
5a
2
1
0.1
0.70
0.71
0.01
0.80
0.015
•
0.60
0.73
0.097
0.65
0.23
, , ,„, . _.._,_
1.03
1.04
0.01
1.23
0.02
(8-?8-77,
0.93
1.13
0.15
1.58
0.35
0.24
0.036
0.28
0.050
0.038
D. Tower 4
1550-1650 hr, 40
0.40
0.092
0.025
0.19
0.017
0.062
0.095
0.73
0.13
0.10
1)
1.04
0.24
0.065
0.49
0.045
0.28
0.07
0.037
0.81
0.11
0.95
0.88
0.098
0.99
0.00
(continued)
63
-------
TABLE 5. (Continued)
E. Tower 5
(8-28-77, 2000-2100 hr, 40 1)
10a
5
2C
ld
0.1
0.58
0.69
0.058
0.86
0.11
0.90
1.06
0.09
1.33
0.16
0.046
0.084
0.021
0.038
0.036
0.12
0.22
0.055
0.10
0.095
0.78
0.80
0.00
0.48
0.04
aCH3SH: 0.20 ng/1
b(CH3)2S2: 0.15 ng/1 as HgS
C(CH3)2S2: 0.11 ng/1 as HgS
d(CH3)2S2: 0.09 ng/1 as H2S; CHgSH: 0.21 ng/1
64
-------
TABLE 6. TOWER SAMPLES AT 20 METERS
Date
8-27-77
8-27-77
8-27-77
8-27-77
8-27-77a
8-28-77
8-28-77b
Time of Day
1200-1300 hr
1305-1425 hr
1425-1550 hr
1550-1715 hr
2030-2130 hr
1610-1710 hr
1715-1816 hr
H9S
ppb *
0.00
0.29
0.10
0.23
0.20
0.94
0.53
ng/1
0.00
0.45
0.16
0.36
0.30
1.45
0.81
a(CH3)2S: 0.03 ng/1 0.01 ppb; (CH3>2S2: 0.02 ng/1 as
b(CH3)2S: 0.22 ng/1 0.08 ppb CHgSH: 0.02 ng/1
65
-------
TABLE 7. MISCELLANEOUS SAMPLES
Time Location HLS 3 Others
ppb |jg/m
A. Cox's Landing, North Carolina
8-29-77 9.3 14.3 (CHQ)0S: 0.1 ppb, (CHQOS0: 0.25 ppb as H0S
Evening 3 2 3Z L *
11.4 17.6 (CH0)0S: 0.1 ppb, (CHQ)0S0: 0.08 ppb as H0S
O Z O Z Lt £*
B. Cedar Island, North Carolina
8-22-77 Seaside Edge 0.28 0.43 (CHo)9S 0.038 ng/1
1240 hr ^ z
8-22-77 Seaside Edge 1.71 2.64
1050 hr
8-23-77 Site 3, 2 ft 3.57 5.5
1130 hr
8-23-77 Site 3, 1 ft 1.69 2.6
1110 hr above ground
8-23-77 Site 2, 2 ft 0.10 0.15 (CHJS: 0.034 ng/1; RS: 0.36 ng/1 as KLS
1250 hr above water
8-23-77 Site 4, J. Day's 0.08 0.12
1200 hr Ditch
-------
TABLE 7. (Continued)
Time
Location ELS
ppb ng/1
Others
B. Cedar Island, North Carolina
8-23-77
1230 hr
8-23-77
1240 hr
8-23-77
2245 hr
8-26-77
(AM)
8-26-77
1200 hr
8-26-77
1630 hr
8-27-77
1830-1910
Bag sample 1 1.04 1.60
Bag sample 2 0.68 1.05
Blockhouse 0.24 0.37
near fence
Boat landing 0.38 0.59
Boat landing 1.25 1.93
Seaside Edge 0.15 0.23
Drum Inlet 0.88 1.36
hr
(CH3)2S: 7.6 ng/1, 2.9 ppb
(CH3)2S: 0.009 ng/1, 0.003 ppb
(CH3)2S: 0.10 gn/1, 0.038 ppb
-------
TABLE 7. (Continued)
Time Location
8-28-77 Chamber No. 2
1100 hr
8-28-77 Chamber No. 1
1700 hr
8-29-77 Pine Grove
925 hr
« 8-29-77 Pine Grove
925 hr
H2S
ppb ng/1
B . Cedar
3.4 5.24
32.0 49.3
1.57 2.42
0.96 1.48
Others
Island, North Carolina
(CH3)2S: 33 ng/1, 15
(CHq)9S: 68.4 ng/1,
O Lt
(CH«)9S: 0.40 ng/1,
6 * RS: 2.7 ng/1
.6 ppb, RS 8.3 ng/1
26.1 ppb
0.15 ppb; CH.SH: 0
as H2S *
(CH3)2S: 0.03 ng/1 0.01 pp; RS 0.71 ng/1
as H0S
&
.05 ng/1
as H0S
LA
-------
TABLE 8. PERCENTAGE COMPOSITION OF REDUCED FORMS OF SULFUR
Ocean Air Samples
Towers No. 1 HgS 96.9 + 4.7% n = 5
No. 2 H2S 98.8 + 2.2% n = 5
Seaside 1 m HgS 99.5 + 3.6% n = 5
Radar Tower 20 m HgS 96.1 + 6.2% n = 4
On-Shore Samples
Towers 17 Samples
H2S 53.2 + 23%
CH3SH 1.2%
(CH3)2S 12.1%
(CH3)2S2 7.9%
RS 25.34%
69
-------
Tandem Filter Measurements
Results for the sulfur measurements in SO2 and H2S are shown in
Figure 22. With the exception of one measurement for SO2> all values
q
were less than 1 pg/m . These results are consistent with the generally
low values determined via the gold-coated glass beads, but a close
comparison is difficult because the TFP and gold bead sampling times are
24 and 1/2 hours, respectively; and, as the previous attitude profiles
show, the concentration of sulfur gases was strongly dependent on
altitude, stressing the importance of the height of the sampler.
PARTICULATE MEASUREMENTS IN AMBIENT AIR
The Dichotomous Sampler
The ranges and mean values for individual elemental abundances as
well as the total mass for the fine and coarse particle fractions are given
in Tables 9 and 10. The values in Table 9 indicate that elements heavier
Q
than aluminum contribute about 2-3 \ig/m or 11-17% to total fine particulate
mass. The remaining mass,is likely to be adsorbed water and compounds
of light elements (optical microscopy shows seed fragments on several of
the fine particle filters). The principal element determined was sulfur
70
-------
1.0
W 9
f
0.5
'• ' i
- 1 ppb *
—
i
: *
:* +
r i i
i i i i i
SULFUR GASES-TFP
• S02
• H2S
-
f 4 * :
i , r~
1 T 1 1 1
8/22 i
8/25 [
DAY OF STUDY
8/28
Figure 22. Sulfur dioxide and H2S content of the ambient air using the TFP and x-ray fluroescence.
-------
TABLE 9. FINE PARTICLES
Tandem Filter Pack
Dichotomous
Element
Range
Mean
Range
Mean
Al
Si
S
Cl
K
Ca
Ti
Fe
Zn
Br
Pb
TSP pg,
<100-600
500-3000
<30-280
<15-90
<11-70
<12-137
3 <9-76
/m
<270 (170)
<140 (140)
1400 (800)
<160 (80)
<50 (30)
<40 (20)
<80 (40)
<17 (20)
<10 (11)
<5 (5)
<30 (20)
<10-51
700-4500
<3-190
<4-59
-------
TABLE 10. COARSE PARTICLES (ng/nT)*
Element
Si
S
Cl
K
Ca
Fe
Ni
Cn
Zn
Br
Sr
TSP jjg/H
Tandem Filter Pack
Range Mean (SD)**
<3-190 72 (56)
70-310 200 (80)
140-1400 770 (500)
<20-120 <53 (33)
28-86 58 (21)
-------
and the amount corresponds to a mean value as sulfate of 6.6 where the
distribution of sulfate values about the mean exhibited a standard deviation
o
of 3.6 pg/m . The total sulfate value measured by the National Air
Surveillance Network for non-urban sites in 1974 was 6.2 with a standard
q
deviation of 6.2 |jg/m , these measurements were made by Hi Vol samplers
which do not discriminate between coarse and fine particles.
Those elements in the coarse particle fraction which are above our
MDL account for only 0.5% of the total mass. The surprising near-absence
of the elements aluminum, silicon, calcium and iron which are usually
associated with particles from the earth's crust and which often make up a
major part of the coarse particles, indicates that the coarse particle orifice
section of the dichotomous sampler may have been plugged during these
experiments. On the other hand, the near absence of these particles in
the coarse TFP fraction as well, suggests that the air sampled was, in
fact, extraordinarily clean of coarse particles.
The Tandem Filter Pack
The elemental abundances for the TFP coarse and fine particle filters
are found in Tables 9 and 10. Roughly speaking, the trends in the TFP
and dichotomous sampler data are in agreement. The TFP is not as
selective as the dichotomous in two respects: 1) the cut point between fine
and coarse particles is not as sharply defined, 2) the upper cut point of
the coarse fraction is not defined; in fact, since the large particle TFP is
74
-------
exposed directly to the atmosphere, any particle which is entrained in the
air stream will reach the filter. The sample volume over a 24-hour period
3 3
is about 1.5 m and 20 m for the TFP and the dichotomous sampler,
respectively. Consequently, the precision of the dichotomous sampler data
is expected to be better.
The fine particle results for the TFP show fair agreement with the
dichotomous sampler results for sulfur and lead. The peculiarly high
values for aluminum in the former may be due to problems with the
least-squares spectral analysis for the very low energy aluminum x-ray.
The coarse particle results show that, in general, the TFP values are
higher than those from the dichotomous sampler. The following results are
consistent with the properties of the sampling systems: the TFP sulfur
results are high because the fine and coarse particle fractions are not
sharply separated; therefore, some of the fine particle sulfur remains on
the coarse particle filter. As there is no large particle cut off for the
TFP, the elements found in large particles will be more abundant in the
TFP coarse fraction than in the dichotomous coarse fraction. This effect
would explain the large chlorine values in the TFP data if one assumes
that the chlorine is associated with very large particles, e.g., sea salt.
75
-------
BIOGENIC RELEASE OF SULFUR IN GASEOUS FORM
One of the interesting discoveries of the study was the entirely
different nature of the sulfur gases emitted from the different sites. For
example, at Site A-l, by far the highest concentration of gaseous sulfur
was volatilized as (CHo)0S, while at Site A-2, H0S was by far the most
o £t Lt
prevalent. Figures 23 and 24 substantiate these observations by showing
chromatograms of samples taken at the two sites. The chromatograms from
Site C were similar to those from Site A-2, while the chromatograms from
Site B showed both HgS and (CH3>2S.
The concentrations of sulfur gases from the chamber varied
considerably depending on time and location. Figures 25 and 26 show two
iVday periods. During each period the chamber remained at one fixed
location, Site A-l, operating continuously. Soil temperature, ambient
temperature, and flow rate were recorded after each sampling for the data
represented in Figure 26. Ambient temperature and flow rate were
recorded less frequently for the data represented in Figure 25. The data
shows a significant diurnal variation, apparently due to temperature
changes, as well as some fine structure which appears to be correlated
with tidal variations. High and low tides are shown by H and L,
respectively. The correlation between chamber concentration and
temperature is shown more explicitly in Figures 27 and 28. As indicated
in these figures, the release of (CHQ)0S during periods of increasing and
o Z
decreasing concentration is an exponential function of the temperature from
August 31 to September 1. On these days the effect of the tide sustained
76
-------
31 AUGUST CTWICAU
TRACOR §60
CHAMBER SAMPLE
OVER GRASS, MUD
AT WATERS'EDGE,
Figure
Gas chromatographic analysis of an air sample taken from the environmental
chamber at Site A-l. Dimethyl sulfide is dominant.
-------
Figure 24.
dominant.
Gas chromatographic analysis at Site A-2 Hydrogen sulfide is
78
-------
96
Ul
cc
a
oc 86
UJ'
fi»
ui
1-1 81
76
31 AUG.-1 SEPT., 1977 I
' D '
SOIL
O
O
0 000
O
D
^ r
VD
1000
800
1600
L
1 400
200
1 1
TIDAL EFFECT?
^jj
^V^^
AJk
— Hi TIDAL DATA1 Lj *&
1
i
TEMPERATURE
*W A *?'
1 " 1 1 1 1
EFFECT?!
A A
s.
' f A ^ H j A ^ „
//
0800!
1200
1600
2000! 2400 0800
TIME,(DST)
1200
1600
2000
Figure 25. (CH3)2S content of environmental chamber samples at site A-l (edgewater)
as a ninction of time.
-------
88
73
68
I23-24 SEPT., 1977
D
AIR
O
D a Daa
n
SOIL
CD
O
soo
400
300
200
100
S *
A
A
AA*L TIDAL DATA H
L TIDAL DATA H L H
h iN I 1 ill
0800
1200!
1600
2000
24001
TIME, (DST)
0400
0800!
1200
Figure 26. (CHo)2S content of environmental chamber samples at site near Site A-l
as a function of time.
-------
1000
800
600
_ 400
300
Ul
o
z
o
o
200
100
76
O 1 SEPTEMBER
O31 AUGUST
78
80
82 84 86
SOIL TEMPERATURE, °F
88
90
92
Figure 27. (CHg)2S content of environemntal chamber samples (same as Figure 25)
as a function of temperature.
81
-------
1000
800
i—r
i—r
O 24 SEPTEMBER
O 23 SEPTEMBER
600
400
o
300
o
o
CO
200
100
72
74
76
78
80
82
84
SOIL TEMPERATURE, °F
Figure 28. (CHo)2S content of environmental chamber samples (Same as Figure
26) as a function of temperature.
82
-------
the high emission rate of (CH3)2S in the interval between high tide and
the soil temperature maximum. Since the tidal day is 50 minutes longer
than the calendar day, the interval between high tide and the occurrence
of maximum soil temperature was shorter on September 1 than on August 31
and the daily release of (CH3)2S was less. The release reached a steady
value due possibly to a limiting environmental condition such as the
availability of reactants or the accumulation of waste products, i.e.,
pollution in the bacterial environment. If bacteria are producing the
(CH3)2S, the accumulation of waste could accelerate bacterial losses until
growth and destruction balance and a steady state population is achieved.
The two days September 23 and 24 were accompanied by tidal
variations caused by local winds and variations in cloud cover, There was
again a rough exponential correspondence between (CH3)2S and soil
temperature and the maximum values achieved during the day were less
than those which occured on August 31 and September 1.
Other chamber measurements taken on the marsh (Site B) are shown
in Figure 29. Chromatograms of chamber samples indicate comparable
amounts of H2S and (CHg)2S at total sulfur concentrations about one order
of magnitude lower than those found at edgewater (Site A). Site B is on
ground seldom covered with water during high tide and seems to be
representative of the roughly 4 square miles of marsh between Cedar
Island and the mainland.
83
-------
CD
50
40
30
03,
'20
10
MONDAY, 30 AUGUST, 1977
1100
I I
SAMPLES HELD IN BAGS FOR 4 hr MAX,
THEN ANALYZED AT ONE TIME
MIDDLE OF MARSH
P-
/ ^
\
1 1
1200
13001
17001
18001
1400i 1500 1600,
TIME, (DST) i
*BAG CONTENTS LOST DURING TRANSPORT FROM SAMPLING SITE • RESIDUAL CONTENTS
1900
Figure 29. Total sulfur content of environmental chamber samples as a function
of time at site B
-------
100
75
•8
b
25
_ 1 _1
MONDAY, 29 AUG.
OVER SAND
AT OUTER BANKS
1300 1330 1400
tlMMDSff
Figure 30. Total sulfur content of environmental chamber samples as a function
of time at Site C.
85
-------
A limited number of measurements were taken over sand on the Outer
Banks. Measurements on the afternoon of August 29 are given in Figure
30. Other measurements indicated that the occurrence of a high tide
during sampling coincided with high HLS values. On one occasion a level
of 1 ppm was obtained just as the tide rose to carry water into the
chamber.
ATMOSPHERIC BACKGROUND MEASUREMENTS OF NITROUS OXIDE,
FREON 11 AND FREON 12
The results of the CIFS measurements of N«O are shown in Table 11
while those for the Freons are shown in Table 12. Typical chromatograms
for Freon 11 and Freon 12, and for N2O, are shown in Figures 31 and 32.
Save for the values found for N0O in container No. 2, the remaining
z
values are in agreement with those currently reported from other
laboratories (16). These results also agree with analytical data obtained in
our laboratory on a sample of rural air collected by the National Bureau of
Standards. The significance of the anomalous concentrations reported for
container No. 2 is not understood as of this writing.
The lone set of values for Freon 11 and Freon 12 may be compared
with data gathered by Hanst, et al. (17), on two days at Atlantic Beach,
North Carolina.
-------
PEAKS ARE LABELLED WITH
RETENTION TIMES
10
12
TIME (minutes)
Figure 31. Typical gas chromatographic analysis of Freon 11 and Freon 12.
87
-------
PEAKS ARE LABELLED WITH
RETENTION TIMES
4 6
TIME (minutes)
10
12
Figure 32. Typical gas chromatographic analysis of N2O.
88
-------
TABLE 11. NITROUS OXIDE RESULTS USING GAS CHROMATOGRAPHIC
DETECTION
Container
Steel No. 1
Steel No. 2
Steel No. 3
Steel No. 4
Stainless Steel
Area
(x)
869
921
1698
1776
809
792
Insufficient3
781
845
Cone. N0O (v/v)
(y)2
0.32 x 10-6
0.34 x 10"6
0.63 x 10-6
0.69 x 10"6
0.30 x 10"5
0.29 x 10"b
0.29 x 10-6
0.31 x 10"6
Calibration Curve: y = 3.693 (10"10) x = 4.617 (10~9)
o
One sample had been removed earlier for Freon analysis. The amount
remaining was insufficient for any second run.
TABLE 12. FREONS
Container
Steel No. 4
Freon 11 (v/v)
1.7 x 10-10
Freon
2.8 x
12 (v/v)
io-10
TABLE 13.
Date
5-3-75
5-6-75
Freon 11
1.4 x lO'10
1.4 x IO-10
Freon 12
2.9 x 10"10
1.7 x Hf10
On May 6, 1975 the sample was taken after a storm in clear, breezy weather.
89
-------
ATMOSPHERIC MEASUREMENTS OF OZONE AND NITROGEN OXIDES
Typical diurnal variations of Og and NO2 dioxide are shown in Figure
33. Similar results were obtained during several days of monitoring.
Throughout the tests O3 concentrations were less than 50 ppb and
remarkably constant except for a decrease at night. Due to the low ELS
values and the attendant necessity of sampling over an extended period to
accumulate a measurable sample, the influence of O« on HLS or (CEL^S
could not be determined.
Nitric oxide and NO2 concentrations were less than 2 ppb except
during the night; thereby confirming the isolation of the site. The
increase in NO at night has no apparent cause although the roughly
simultaneous decrease in O3 concentrations indicated that a true NO
increase is likely instead of some sampling artifact.
90
-------
Figure 33. A one day data recording of ambient NO and O3 concentrations.
-------
SECTION 4
CONCLUSIONS AND RECOMMENDATIONS
1. Real time and gas chromatographic monitoring of sulfur gases --
Direct analysis of ambient air at Cedar Island substantiated that the
concentrations of gaseous sulfur compounds were consistently less
than 5 ppb. The fact that the Meloy SA-285 Sulfur Analyzer and the
Tracer 560 Gas Chromatographic-FPD have detection limits of 0.5 ppb
and 2-7 ppb, respectively, depending on the sulfur species, makes a
precise measurement at ambient levels difficult.
Recommendations: The possibility of more sensitive detection of H2S,
(CHo)oS, CHqSH, etc. by monitoring chemiluminescence with Oo needs
additional study. In-house results with a commercial O3 monitor
adapted for study of Og chemiluminescence with H2S and CKLSH
showed that the relative responses of E^S and CHoSH are 1:22 and
that 10 ppb of HoS can be detected. A low pressure system
optimized for light collection could be more sensitive than an FPD,
especially for gas chromatographic analysis.
92
-------
2. Preconcentration techniques using gold bead traps -- Development of
a trapping technique for sulfur compounds using gold coated glass
beads is occurring at the University of South Florida under
NSF-RANN sponsorship. The efficiency of collection and release as
well as the integrity of sulfur compounds during transfer between
analysis system components have been characterized to form a basis
for the technique as documented by Ammons and Braman (7).
Intercomparison of two calibration standards, i.e., permeation tubes
and known solutions of thioacetemide in aqueous solution, gave
consistent results and established a sensitivity limit of 0.1-0.2 ng of
sulfur with an almost Linear response using FPD detection. The
calibration precision was +4.9% using 80% confidence limits over a
range of 1-50 ng sulfur.
Three features of the technique have been identified as
requiring improvement: 1) speciation of heavier molecular weight
sulfur compounds (see Figure 16 showing the unresolved group of
compounds referred to as RS); 2) blanking of the gold-coated bead
trap to establish a "zero" level or blank response; and, 3) use of
manpower intensive efforts to sample and analyze.
Recommendation: Continuation of the NSF-RANN grant to South
Florida should be encouraged to evolve solutions to the three factors
of concern. Automatic samplers should be designed for future studies
and an EPA contract or grant effort should be initiated for automation
of the analysis phase of the technique.
93
-------
The glass bead technique has been successfully employed in its initial
application. Vertical profiles show increases in sulfur compound
concentration with height and a sulfur compound mix that changes
with height and the direction of prevalent winds.
Hydrogen sulfide is increasingly responsible for sulfur content as
height is increased to 10 meters while (CH3)2S, (CH3)H2S2 and
higher molecular weight sulfur-containing compounds are detected
near the ground (see Figures 17-21). An unexplained perturbation in
the general trend of increasing concentration with height occurs at
approximately 1 meter height where an increase in sulfur is seen.
Wind masses from the marsh bring more (CHo)2S, and (CHg)2S2 while
samples taken in the local pine forest show heavier sulfur compounds.
3. Biogenic emissions — Chamber studies coupled with GC-FPD
measurements were used to identify the mix of sulfur compounds
originating from the marsh and to identify pertinent parameters
effecting the release of these compounds. The majority of
measurements were made over uncut marsh grass near edgewater
locations where water was carried into the chamber during
measurement.
Differences in the mix of biogenic emissions from sand and marsh
were observed using an environmental chamber. Dimethyl sulfide is
prevalent over the edgewater marsh areas, HS over sand
94
-------
areas; both compounds occur in the main marsh area. Edgewater
emissions are estimated to be an order of magnitude higher than
emissions in the marsh, i.e., roughly 10 g/m2/yr as compared to 1
2
g/m /yr. Diurnal variations in chamber concentrations were observed
to correlate with soil temperature. Tidal effects appear to be
supported by existing data but need additional confirmation. Both H2S
and (CH3)2S were detected in the ambient air, using the previously
described gold gead technique, when sampling of air masses from the
marsh areas was performed. However the measurement of (CH3)2S2
and higher molecular weight, S-containing compounds in the ambient
air could not be satisfactorily related to evolution from the Cedar
Island marshes.
Because stirring of the volume enclosed by the environmental
chamber was precluded by the presence of marsh grass, questions
related to channeling of the air from chamber inlet to outlet arose.
These questions were answered by examining data taken during a
period of measurement when chamber concentrations were constant so
that the outlet concentration "f" could be measured as function of
flow rate "F" to test the model presented on p. 41 of the text. The
results are shown in Figures 34 and 35 and suggest that the model
agreed with experiment to within ± 20% even though stirring of the
chamber volume was not performed. Comparison with a stirred
environmental chamber was performed at the beginning of the chamber
studies (see Figure 36). Reasonable agreement was obtained after a
tight seal has been made around the bottom edge of the chamber.
95
-------
EFFECT OF FLOW RATE ON CHAMBER CONCENTRATION
300
250
~ 200
0>
0>
B.
eo 150
H-p
100
so
0
1 1 1 1
1
— o —
\
__ \ -_
\
— \ —
\
•••w* V ^•KIMB
— •»»»
— —
1 1 1 1
0.5 1.0 1.5! 2.0
CHAMBER FLOW RATE, I/mini
CO
40
20
THURSDAY, 1 SEPT.!
I I L
I I I I I I I
1500 1600 1700 1800! 1900 2000 2100 2200
TIME, (DST)!
Figure 34. Total sulfur content of environmental
chamber samples as a function of flow
rate through the chamber
Figure 35. Chamber concnetrations prior to
study shown in Figure 34.
-------
Wo
TS, percent raj
l<0; 01 -"Ji
01; o 01
_L
SUNDAY, 28 AUG., 1977
0
AT
- °— ^, *
S
CHAMBER #1 ^^V\
CHAMBER #2 ^^ ^ <-
1
1300 1400 1500 11
1
VER BRASS
LEWIS CREEK —
SAND PACKED
IOUND CHAMBER —
ov
? °~?
500 1700 1800 1900 2000
TIME, (DST)
SIDE BY SIDE CHAMBER COMPARISONS
Figure 36.
of results from stirred and unstirred environmental
97
-------
The effect of an environmental chamber on the unperturbed flux
of sulfur compounds has recently been tested in some detail by Hill,
et al. (14).
Recommendation: Chamber measurements should be used with
consideration for the factors which can alter the unperturbed flux.
However, a simple chamber of the type used in the CIFS can establish
the mix of sulfur compounds and the factors which cause changes in
the emission rates. These results are expected to be consistent with
ambient air measuremetns made with the gold bead technique.
4. The occurrence of (CH3)2S as the major gaseous component emitted
from certain areas of the Cedar Island marsh prompted an
investigation into possible alternative measurement techniques for this
gas. Dr. W.F. Herget of EPA obtained a qualitative infrared
absorption spectrum of this gas (see Figure 37). An indication of
significant absorption in the spectral region around 10.5 microns led
to a measurement of the absorption coefficient at CO2 laser line
positions in this region. The results, obtained by Mr. Richard
Richmond, of Northrop Services are listed below:
98
-------
VD
VO
Figure 37. (CH3)2S Infrared Spectrum (60-1070 cm"1); top trace indicated zero
absorption.
-------
CO2 laser line R(14) 10.286 pm 6.2 atm^cm"1
R(16) 10.272 |jm 13.6 atm^cm"1
R(18) 10.258 pm 11.6 atnfW1'
Although these measurements are tentative, they suggest the
possibility of measuring (CHQ)0S by an optical technique, i.e., by
O ^
either an optoacoustic technique or a long path absorption technique.
The measurement of gas emissions as an integrated average over a
horizontal distance of several hundred meters at several heights would
allow emission rate measurements to be inferred. This technique
would eliminate the uncertainties associated with localized
measurements. Such measurements appear feasible for gases such as
CO2, CO, N2O, NO, NHg, and (CHg)2S, depending on the actual
levels of concentration above the emitting area.
5. Elemental analysis of x-ray fluorescence of fine and coarse particle
fractions collected by the dichotomous sampler and the tandem filter
pack showed rough agreement between these two collection devices.
The tandem filter system is not capable of reproducing the collection
properties of the dichotomous sampler, but can provide approximate
data for suspended particulates. The dichotomous sampler used in
these experiments may have had a plugged coarse particle inlet. This
sampler was an early two-stage model and more recent one-stage
designs are expected to avoid this possible difficulty.
100
-------
5. Determination of atmospheric SO2 by the FPD (short collection times)
and the tandem filters (long collection times) were consistent.
Detailed comparison is not possible because ambient SO2 levels were
often at or below the FPD's minimum detection level.
6. Determinations of atmospheric H2S by the glass bead technique (short
collection tikes) and the tandem filters (long collection times) were
consistent. Detailed comparison is not possible because of the
difference in collection times and the very sensitive dependence of
reduced sulfur gas concentration on sampling location, as shown by
the height profiles in Figures 17-21.
101
-------
APPENDIX A
NATURAL SULFUR IN THE ATMOSPHERE
What do the Sulfur Budgets Tell Us?
by
Robert W. Shaw
102
-------
SECTION A-l
INTRODUCTION
A controversy has existed for some years concerning the relative
contributions from man-associated and natural processes to the level of
sulfur compounds in the atmosphere. Not surprisingly, the bulk
contribution from man-associated activities are much better known than
those from natural processes. In an effort to understand the flux of
sulfur compounds through the atmosphere, some authors have devised
budgets of the "sulfur cycle." These budgets have the following common
characteristics: 1) they divide the earth into compartments -- generally
lands, oceans and atmosphere; 2) various theoretically and experimentally
derived values for concentration of sulfur compounds (the input values)
are used to estimate flow between compartments; and 3) a "balance"
between flows in and flows out is assumed for one particular compartment,
and this balance constraint allows one to infer any sulfur flux not
accounted for by the estimated input values. This inferred flux (the
output value) is the contribution from natural processes for the sulfur
cycle models discussed here.
The various budgets differ in their choice of input values and their
balance constraints. It is my purpose here, to summarize the various
budget input values and constraints. It will become clear that the
103
-------
natural sulfur contributions inferred by different authors are very
sensitive to the characteristics, of the models used. These comments are
not critical of the global sulfur cycle models; the uncertainties of
budget-derived sulfur fluxes are well understood by their authors. The
papers described here may also serve as evaluations and guides to the
literature of atmospheric chemistry and its characterization, and the sulfur
budgets are only part of these interesting publications. This paper is
simply intended to help judge the significance of the magnitudes of natural
sulfur fluxes derived from global sulfur budgets. In the following section,
budget inputs and constraints will be presented very briefly with no
discussion of their validity or plausibility; for these the reader is referred
to the original articles. In Section A-3 the implications of using a number
of model calculations are discussed. The models are approximate, as are
the budgets themselves; they serve as order-of-magnitude indications of
the consequences of the natural sulfur evolution rate values. In Section
A-4 the measurement of natural sulfur is discussed. The summary and
conclusions are in Section A-5.
104
-------
SECTION A-2
DESCRIPTION OF THE MODELS
Junge (19) has developed a sulfur budget based on a balance in the
atmosphere; his values are given in Table A-l. According to Junge, the
best known sulfur source is industrial (40 MT/yr, 1 MT = 106 tons), and
the best known sink is precipitation (70 MT/yr). Junge assumes that
natural evolution of sulfur from the land (70 MT/yr) is balanced by "direct
uptake." Since the amount of sulfur in precipitation over land exceeds the
industrial output by 3O MT/yr, this amount must be supplied by the
ocean. The "direct uptake" by the ocean is 70 MT/yr, the precipitation
contribution is 60 MT/yr. Therefore, the ocean must supply 160 MT/yr of
natural sulfur to balance the atmosphere.
Notice that in this budget, the natural evolution and absorption over
land are equal and form a closed system with no effect on the other
compartments of the model. A consequence of the budget is the
accumulation of sulfur in the ocean as a result of river run-off. This
budget proposes total sulfur evolution from natural sources of 230 MT/yr;
of this, 140 MT/yr is absorbed by direct uptake. Nothing is known about
105
-------
the lifetime of the uptake process; within the limit of short lifetimes for
evolution-absorption there would be no contribution to the atmospheric
sulfur burden. A possible measure of the natural contribution to sulfur in
the atmosphere over land is given by the net sea to land flux of 30
MT/yr.
Kellog, et al. (20), developed a global sulfur budget which is similar
to that of Junge. Sulfur sources to and sinks from the atmosphere are
brought into balance by including the necessary flux from natural sources.
Values from their budget are given in Table A-l. Their inferred value for
naturally evolved sulfur is 89 MT/yr; it is much lower than Junge's value
because: 1) the dry deposition for sulfur over land is much lower; 2) the
dry deposition over ocean is zero; and 3) part of the wet deposition over
the ocean is supplied by sea spray. A consequence of the budget by
Kellog, et al. is that the net sulfur flux through the atmosphere occurs
from the land to sea.
An interesting global sulfur budget has been presented by Hallberg
(21) who has estimated a pre-industrial sulfur cycle. Again, the sources
to and the sinks from the atmosphere are balanced; but, unlike the
previous budgets, another balance is included — a steady state of the
pedosphere. Inputs to the pedosphere are weathering, sea spray, and wet
and dry deposition; outputs are river run off and natural evolution. The
budget values are given in Table A-l.
106
-------
In Hallberg's budget the natural contribution of evolved sulfur
compounds is inferred by satisfying the balance requirements for the
pedosphere; it is about one sixth that estimated by Junge and one half
that estimated by Kellog, et al. The lower value for natural sulfur is due
to the values for wet and dry deposition. These wet and dry deposition
rates are themselves inferred from the balance requirement for the
atmosphere. A consequence of the budget by Hallberg is that a
pre-industrial net sulfur flux from sea to land is reversed by industrial
output to become a net flux from land to sea.
Granat (22) has presented a global atmospheric budget in a companion
paper to that by Hallberg. Granat's budget emphasizes the sources of
sulfur in submicron particles. Granat assumes a balance in the atmosphere
and, from an independent review of the literature, develops a budget
which agrees well with Hallberg's results (see Table A-l). Both Granat
and Hallberg point out that earlier sulfur budgets included sulfur
deposition rates which depended on a rather scant and uncertain data
base. These sulfur concentration data may have been high because of
influences of distant pollution sources. Only recently have workers
appreciated the influence of, for example, industrial centers in creating
pollution episodes hundreds of kilometers away; hence the early estimates
of global deposition rates and the consequent natural evolution rates may
have been too high.
107
-------
SECTION A-3
DISCUSSION
Our interest here is in the information derived from the budgets
concerning the relative contributions of sulfur compounds to the
atmosphere by man and by nature. As we have seen, the estimated
natural contributions range from 40-230 MT/yr. Can one then assume with
confidence that the real value lies somewhere between these limits? I
believe not. As we have already seen, these values are inferred from a
balance condition and depend on values for deposition rates over the entire
surface of the earth. The balance condition, i.e., that the inputs to and
the outputs from the atmosphere are equal, appears plausible. Very little
is known, however, about global deposition rates.
We next examine the implications of the budgets on sulfur burdens in
the atmosphere. As the authors of the budgets recognized and discussed
at some length, little is known concerning the lifetimes of sulfur
compounds in the atmosphere especially from natural sources. The
relation between lifetime and sulfur burden becomes visible in a rough way
when considering a system with sulfur input rate "I" (MT/yr), total sulfur
burden "S" (MT) and output rate constant "A" (yr"1). Then:
108
-------
\S = I (1 - e~Xt) ,
S = I (l - e'Xt) .
This expression shows that the sulfur burden will approach a steady state
value of IA. Since the half life "t^" is equal to ln2/A, the sulfur burden
is directly proportional to the atmospheric lifetime.
Table A-2 shows a number of steady state atmospheric sulfur burdens
that are due to the natural evolution rates taken from two of the global
sulfur budgets described above for a number of assumed atmospheric
sulfur half lives (1 day and 10 days); the simple expression derived above
was used. The burden has been expressed in ppb (v/v) by taking the
21
mass of the atmosphere to be 5 x 10 gm (23) and assuming one sulfur
atom per molecule. Table 2 gives the results for two assumptions for
mixing: 1) the sulfur compounds mix uniformly throughout the entire
atmosphere; 2) mixing occurs uniformly throughout the atmosphere below
the altitude of 1 km (approximately 11% of the atmosphere lies below 1 km.
In this calculation it is assumed that naturally evolved sulfur compounds
are spread uniformly through their mixing volume and that all have the
same half life. The wide range of values in Table A-22 shows the
sensitivity of steady state atmospheric sulfur concentrations to assumed
evolution rates and atmospheric lifetimes.
109
-------
The calculation just outlined is very crude; as mentioned above, it
assumes that the sulfur compounds are uniformly mixed throughout their
mixing volume in the atmosphere. In fact, since they are injected into the
atmosphere from the land or from a sea surface and leave the atmosphere
through these surfaces, a gradient will exist, the highest concentration
being at the surface. Since we live mostly at or near these surfaces,
these higher concentrations are most important; the calculation, however,
only roughly indicates a lower limit.
110
-------
SECTION A-4
MEASUREMENT OF NATURAL SULFUR IN THE ATMOSPHERE
The estimated ratio of the natural evolution of sulfur compounds to
man-associated (industrial) evolution in the models described above ranges
from 6/1 (19) to 1/2 (22). Although one may argue that more recent data
were available to Granat than to Junge, the budgets themselves present no
compelling evidence that the natural sulfur evolution rates may not be even
larger than those estimated by Junge or alternatively, even smaller than
those by Granat. It is clear that resolution of this question would require
at least the following: 1) measurement of natural evolution rates of sulfur,
and 2) identification of the compounds evolved.
There are two means of estimating natural sulfur evolution rates: 1)
by direct measurement, 2) indirectly, by inferrring the natural sulfur
"background" levels from measurement of atmospheric samples in areas not
affected by mean-associated activities. The best procedure may be a
judicious combination of these two methods. The indirect method is
complicated by at least two factors: 1) measurements of atmospheric samples
may be affected by long range effects of distant industrial or urban
pollution sources, 2) evolved sulfur compounds are immediately diluted by
the atmosphere in a complex and, presumably, varying manner.
Ill
-------
Direct measurement can be carried out by placing an enclosure over
the surface to be studied and sampling the sulfur compounds, if any, as
they evolve into it. A system of this sort has been described by Aneja
(13) and others; workers at the EPA are now evaluating the use of
sampling enclosures in the field (this report). The application of gas
chromatography to the collected sample provides separation and
identification of the evolved sulfur compounds. Any sampling program
which uses enclosures will have to examine the effect, if any, of the
enclosure itself on the evolution rates.
The obvious difficulty with direct measurement is the need for
sufficient local data to characterize adequately a global process. Some
investigators believe that -most natural sulfur evolution occurs from marshy
and estuarine areas. If this is so, and if the sulfur evolution from a
given marsh can be correlated with some large scale characteristics of the
marsh, e.g. soil composition, the problem reduces to one of determining
the sulfur evolution from the various types of marsh and multiplying by
the total area of these marshes.
112
-------
SECTION A-5
SUMMARY AND CONCLUSIONS
The required evolution of sulfur compounds from marsh areas may be
estimated according to the various global sulfur budgets by assuming the
following: 1) that all marshes emit uniformly; 2) that aU other natural
sulfur sources are negligible; and 3) by taking the total marsh area as 2.8
5 2
x 10 km (25). By simply dividing the evolution rates by the emitting
area, we find that the sulfur budgets of Junge and Granat demand
evolution rates of 750 and 120 g/m /yr, respectively. The sulfur evolution
Q
rate may also be calculated, if all the land surfaces of the earth (1.5 x 10
o 22
km ) emit uniformly; these rates are 1.4 g/m /yr and 0.22 g/m /yr for the
Junge and Granat budgets, respectively.
The calculation is a crude one; however it does serve to tabulate the
natural sulfur evolution rates from the sulfur budgets so that they may be
compared with the experimental measurements. In Table A-33 the results
from these calculations are compared with the measurements for sulfur
evolution made by Aneja (13) in the Long Island tidal marshes and by
McClenny, et al. (this report) in the North Carolina tidal marshes. In
these experiments, sampling enclosures were used and the sulfur
compounds were identified using gas chromatography. Aneja1 s
113
-------
measurements were made in October and November, 1974, during the day
with soil sediment temperatures ranging from 6.6-17.6°C. He remarks that
o
his highest value for HgS, 39 g/m /yr is "anomalously high." The
averages were calculated neglecting the "anomalously high" value and also
neglecting zero measurements. The averages shown for the measurements
by McClenny made in August, 1977, also neglect any zero values.
The experimental measurements may now be compared with the
expected evolution rates based on the sulfur budgets and assuming that
only marsh lands evolve sulfur. According to Table A-3, the evolution
rates of sulfur compounds from experimental sites the on Long Island and
North Carolina marshes are 100-1000 times lower than expected from the
sulfur budgets. Therefore, if marshlands are the most important sources of
natural atmospheric sulfur, and, if the sulfur budget values for natural
sulfur evolution rates are correct, somewhere there must exist very high
sulfur producing marshes.
114
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TABLE A-l. PRINCIPAL ELEMENTS IN THE GLOBAL SULFUR BUDGETS (MT/yr)
LAND
SEA
Evolution Deposition Evolution
Industrial
Junge
Kellog, et al.
HalTberg
pre- industrial:
present:
Granat
40
50
0
72
72
Natural Wet Dry Spray
70 70 70
89a 86 25 43
3 23"? 48*
1 T? 48d
6 55 40 48
Natural
160C
37
1Z
30e
Net Sulfur Flux
Deposition Through Atmosphere
Wet Dry Land -> Sea Sea -» Land
60 70 30
72 29
21h I?
39b 1
61 2 14
Underlined values are derived from balance constraints.
a) Natural evolution occurs from land and "coastal areas." b) wet + dry deposition, c) Natural evolution occurs from
"sea or coast."
d) Sea spray not included in deposition calculations, e) Natural evolution occurs from land and "coastal areas."
-------
TABLE A-2. STEADY STATE GLOBAL ATMOSPHERIC SULFUR FROM NATURAL
SOURCES
Budget
Junge
Granat
Natural Evolution
Rate (MT/yr)
230
36
Sulfur
t1/2 = 1 day
1.4*
0.15**
0.21*
0.023**
Burden (ppb)
10 days
14*
1.5**
2.1*
0.23**
*Mixing Depth: 1 km (11% of atmosphere)
**Mixing Depth: « (100% of atmosphere)
TABLE A-3. RATES OF NATURAL SULFUR EVOLUTION
A. Model Calculations
Budget From Marshes Only From All Land Surfaces
(2.8 x 10U m2) (1.5 x 1014 m2)
2
Junge 750 g/m /yr
Granat 120 g/m /yr
B.
Location
Aneja: Long Island
coastal marshes (1974)
McClenny: North Carolina —
coastal marshes (1977)
1.4 g/m /yr
0.22 g/m2/yr
Experimental Measurements
2
Sulfur Evolution Rate (g/m -yr)
H2S DMS
39 (max) 2.0 (max)
0.33 (av) 1.4 (av)
7.8 (max) 5.5 (max)
0.5 (av) 0.3 (av)
116
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APPENDIX B
OPERATING CHARACTERISTICS OF THE SULFUR
MONITOR USED AT CEDAR ISLAND
by
R.W. Shaw
117
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This section briefly describes the response of the Meloy SA 285 FPD
used at Cedar Island to CO2; Water Vapor, and In-line Scrubbers.
Bench tests run at EPA laboratories have shown that CO2 will cause
the detector response to sulfur to decrease. Over the range 0-150 ppb
SO0, the presence of 350 ppm CO0 causes a nearly linear decrease in
L* £t
response of 10%. If, however, the instrument is calibrated in the presence
of 350 ppm CO2, the reproducibility and linearity of response are
excellent. Similarly, water vapor causes decreased response in the
detector. For example, a change from 0-100% relative humidity at 22°C
causes a depression of the zero response by an amount equivalent to 3 ppb
so2.
In order to adjust the instrument response for the effects of CO0 and
M
water vapor outlined above, calibrations in the field were made using air
containing 350 ppm CO2 and at approximately 80% relative humidity. These
conditions roughly reproduced the properties of the ambient air.
During the field experiments, the sample line into the detector
contained a Teflon filter to remove sulfate aerosol particles. In addition,
an SO2 gas scrubber (Meloy Labs) could be moved in and out of the
sample line. The level of reduced sulfur gases in the ambient sample was
determined by the difference: total sulfur gases minus SO,,. Laboratory
118
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experiments at EPA laboratories indicate that, at 50% relative humidity,
SO2 scrubbers remove 100% of SOg down to less than 0.2 ppb and pass
75-90% HgS. Warming the scrubber improves the H«S pass-through, but
does not bring it up to 100%.
119
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REFERENCES
1. Braman, R.S. and Ammons, J.M. 1978 — Preconcentration and
Determination of Hydrogen Sulfide. Anal. Chem.59: 992-996, 1978.
2. Parker, R.D., G.H. Buzzard, T.G. Dzubay and J.P. Bell, A Two
Stage Respirable Aerosol Sampler Using Nucleopore Filters in
Series. Atmos. Environ., 11(7):617-621, 1977.
3. Shaw, R.W. Atmospheric Instrumentation Branch, Environmental
Sciences Research Laboratory, Research Triangle Park, N.C. 1977
(Unpublished).
4. Rehme, K.A., B.E. Martin, and J.A. Hodgeson, 1973. Tentative
Method for Calibration of Nitric Oxide, Nitrogen Dioxide, and Ozone
Analysis by Gas Phase Titration, EPA-R2-73-246, U.S.
Environmental Protection Agecy, Research Triangle Park, N.C.
1974.
5. Brody, S.S. and J.E. Chaney. Flame Photometric Detector J. Gas
Chromatogr., 4:42-46, 1966.
6. Stevens, R.K. Mulik, J.D., O'Keeffe, A.E. and Krost, K.J., Gas
Chromatography of Reactive Sulfur Gases in Air at the
Parts-per-Billion Level. Anal. Chem. 43(7):827-831, 1971.
7. Ammons, J.M. Selective Metal Surfaces for the Analysis of Ambient
Concentrations of Hydrogen Sulfide. M.S. Thesis, University of
South Florida, Tampa, Florida. 1976
8. O'Keeffe, A.E. and G.C. Ortman, Primary Standards for Trace Gas
Analysis. Anal. Chem. 38(6):760-763.
9. National Academy of Sciences, Washington, D.C. 1977. "Medical and
Biological Effects of Environmental Pollutants, Nitrogen Oxides, 56;
Ozone and Other Photochemical Oxidants, 126.
10. Saltzman, B.E., Colorimetric Microdetermination of Nitrogen Dioxide
Anal. Chem. 26(12): 1949-1954.
120
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11. Loo, B.W., J.M. Jaklevic and F.S. Goulding, 1976. Dichotomous
Virtual Impactors for Large Scale Monitoring of Airborne Particulate
Matter. In Fine Particles. B-Y. H. Liu ed. Academic Press Inc.,
New York, New York, 1976.
12 * ???*?• T'G-> and R-K- Stevens, Ambient Air Analysis with
Dichotomous Sampler and X-ray Fluorescence Spectrometer. Environ.
Sci. Technol., 9(7):663-667, 1975.
13. Aneja, V.P., Characterization of Sources of Biogenic Atmospheric
Sulfur Compounds, M.S. Thesis at N.C. State University, Raleigh,
IN . u , 1975 .
14. Hill, F.B., Aneja, V.P. and R.M. Felder, A Technique for
Measurement of Biogenic Sulfur Emission Fluxes. J. Environ. Sci.
Health, A13(3): 199-225. 1978
15. Wang, W.C. Yung, Y.L., Lacias, A. A., Mo. T., Hasen, J.E.,
Greenhouse Effects Due to Man-Made Perturbations of Trace Gases.
Science, 194(4266) :685- 690, 1976.
16. Rassmussen, R.A., 1974. Tellus, 26, 254.
17. Singh, H.B., Salas, L.J., and Cavanaugh, L.A. Distribution,
Sources, and Sinks of Atmospheric Halogenated Compounds. J. Air
PoUut. Control Assoc., 27(4): 332-336, 1977.
18. Hanst, P.L., Spiller, K.L. Watts, D.M. Spence, J.W., and Miller,
J.W., Infrared Measurement of Fluorocarbons, Carbon
Tetrachloride, Carbonyl Sulfide, and Other Atmospheric Trace
Gases. J. Air Pollut. Control Assoc. 25(12): 1220- 1226, 1975.
19. Junge,C.E. Air Chemistry and Radioactivity . Academic Press, Inc.
New York, 1963) pp 59-74.
20. Kellogg, W.W., R.D. Cadle, E.R. Allen, A.L. Lazrus and E.A.
Marten, The Sulfur Cycle. Science, 175(4022) -.587-596, 1972.
21. Hallberg, R., The Global Sulfur Cycle. Ecol. Bull. (Stockholm)
22:89-123, 1976. ,
22. Granat, L., H. Rodhe and R. Hallberg, The Global Sulfur Cycle,
Ecol. Bull (Stockholm), 22:89-134, 1976.
23. Chemical Rubber Company. Handbook of Chemistry and Physics,
Section F. Cleveland Ohio.
24. Woodwell, G.M. P.M. Rich and C.A.S. Hall, in G.M. Woodwell and
E.V. Pecan (eds.), Carbon and the Biosphere, U.S. Dept. of
Commerce AEC Symposium Series 30:221-240, 1973 .
121
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/2-79-Q04
4. TITLE AND SUBTITLE
EVALUATION OF TECHNIQUES OFR MEASURING BIOGENIC
AIRBORNE SULFUR COMPOUNDS
Cedar Island Field Study 1977
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
6. PERFORMING cQANZAf ION COol
7. AUTHOR(S)
W.A. McClenny, R.W. Shaw, R.E. Baumgardner, R. Paur
and A. rColeman
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
10. PROGRAM ELEMENT NO.
1AD712 BB-12,"16, & 17(FY-78
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
— RTF, NC
13. TYPE OF REPORT AND PERIOD COVERED
In-house
14. SPONSORING AGENCY CODE
EPA/600/09
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Sulfur in both gaseous and particulate form has been measured near biogenic
sources using new measurement techniques. The preconcentration of gaseous sulfur on
gold-coated glass beads followed by desorption into a flame photometric detection for
sulfur is shown to have a detection limit of 0.1-0.2 ng of sulfur and to allow for
speciation of H2S, CHgSH and (GEL) S at low parts per trillion levels. Ambient
levels of NO and 03 were found to alter the molecular form of sulfur on the beads
unless scrubbed from the sampled air. A collection technique using tandem filters is
extended from earlier efforts on fine and coarse aerosol to include collection of SO
and H2S on chemically coated filters; these filters are analyzed by X-ray 2
fluorescence for sulfur content. Measurements of gases evolved from biogenic sources
reveal H,S and (CH^S as primary components with significant diurnal variations.
Recommendations for further instrument development are given.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
*Air pollution *Evaluation
*Sulfur inorganic compounds
*Sulfur organic compounds
*Biological productivity
*Coasts
*Measurement
*Chemical Analysis
Cedar Island, NC
13B
07 B
07C
08A
08F
07D
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
138.
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
122
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