PB86-239910
Toxic Chemicals in the Environment
A Program of ?ield Measurements
SRI International, Kenlo Park, CA
Prepared for
Environmental Protection Ajsncy
Research Triangle Park, KC
Aug 86
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PB86-239910
EPA/600/3-86/047
August 1986
TOXIC CHEMICALS IN THE ENVIRONMENT:
A PROGRAM OF FIELD MEASUREMENTS
by
H. B. Singh, R. J. Ferek, L. J. Sal&s, end K. C. NUz
Atmospheric Science Center
SRI International
Menlo Park, California 94025
EPA COOPERATIVE AGREEMENT CR8092BZ
Project Officer
Larry Cupltt
Atmospheric Sciences Research Laboratory
Research Triangle Park, North Carolina 277U
ATMOSPHERIC SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
I'.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
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NOTICE
The Information 1n this document has been funded by the United
States Environmental Protection Agency under Cooperative
Agreement CR809282 to SRI International. It has been subject
to the Agency's peer and administrative review, and 1t has been
approved for publication as an EPA document. Mention of trade
names or commercial products does not constitute endorsement
or recommendation for use.
11
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ABSTRACT
An environmental mobile laboratory was instrumented and employed to
perform a series of eight field studies of 1-to-3 week3 duration during which
around-the-clock measurements of a large number of organic chemicals were
performed in six United States cities under a variety of meteorological condi-
tions. Field studies involved on-site analysis of 29 organic chemicals, many
of which are mutagens or suspect carcinogens. Chemicals measured Included
chlorofluorocarbons, halomethanes, haloethanes, halopropanes, chlorinated
alkenes, aromatic hydrocarbons, organic nitrogen compounds and aldehydes. The
measured data are reported as mixing ratios and interpreted In the context of
their mean diurnal behavior and chemical removal rates. Data tapes have been
provided to the U. S. Environmental Protection Agency. Except for aromatic
hydrocarbons and aldehydes, average concentrations of measured species were In
the 0-to-5 ppb range. The average concentration range for aromatics and
aldehydes was in the 0-25 ppb range. Maximum measured concentrations were
typically 5 to 10 times the mean values. Typical diurnal profiles showed
highest concentrations in the night and early morning hours. Minimum values
observed In the afternoon were probably due to deep vertical mixing. San Jose
studies clearly showed the effect of meteorology with mean concentrations
rising 1 to 7 times normal values under stagnant conditions. Ambient data
suggests that aldehydes are significantly less abundant in winter. Interpre-
tation of aromatic hydrocarbon data frcm Southern California showed that the
prevailing hydroxyl radical concentrations of 2.6 x 10^ molec.cm"^ in February
are not significantly different from values determined for summer. Analysis
of historic data further suggests that the concentrations of benzene (the
domi<.?nt toxic chemical in ambient air) have declined by a factor of about 10
in the acbient air of Southern California over the last two decades.
111
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CONTENTS
ABSTRACT Hi
ILLUSTRATIONS v1
TABLES vi i 1
ACKNOWLEDGMENT . ix
1 INTRODUCTION 1
2 OVERALL OBJECTIVES 2
3 ANALYTICAL METHODOLOGY 3
Field Instrumentation 3
Experimental Procedures . 3
Calibrations 10
Quality Control and Assurance Ii>
4 FIELD MEASUREMENTS 19
5 ANALYSIS AND INTERPRETATION OF FIELD DATA 22
Interpretation of Field Data by Chemical Category 32
6 TRENGS AND SEASONAL CYCLES 78
7 SUMMARY AND CONCLUSIONS 31
REFERENCES 83
v
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ILLUSTRATIONS
Number Page
1 Assembly fop a 2-h integrated air sample collection
in 6-liter stainless steel canisters
2 Chlorosthane concentrations at the Philadelphia
site as measured by SRI and NSI........ 16
3 Toluene concentrations at the Philadelphia site as
measured by SRI and NSI 16
4 Toluene concentrations at the San Jose site as measured
by SRI and NSI 17
5 Benzene concentrations at the San Jose site as measured
by SRI and NSI 17
6 Tetrachloroethylene concentrations at the Philadelphia
site as measured by SRI and NSI 18
7 Tetrachloroethylene concentrations at the San Jose site
as measured by SRI and NSI 18
8 Diurnal behavior of fluorocarbon-113 at the San Jose site
during April, August and December, 1985..., . 34
9 Diurnal behavior of fluorocarbons 12 and 11 4 at
Downey , CA, s ite 35
10 Diurnal behavior of fluorocarbon 12 at San Jose
site during April, August and December 1985 36
11 Methyl chloride distribution and its diurnal
behavior at Houston and Denver sites jf8
12 Methyl bromide distribution and its diurnal
behavior at Downey, CA site 40
13 Diurnal behavior of methyl iodide at Downey, CA
3ite 42
14 Diurnal behavior of methylene chloride at San Jose site
during April, August and December 1985 43
I
15 Diurnal behavior of methylene chloride at
Philadelphia ana Downey sites 44
v1
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16 Diurnal behavior of chloroform at San Jose site
during April, August and December, 1985 46
17 Diurnal behavior of chloroform at the Downey site............ 17
18 Diurnal behavior of carbon tetrachloride at
Downey and San Jose sites 19
19 Diurnal behavior of ethylene dichloride at
Downey, CA site . 51
20 Diurnal behavior of ethylene difcromide at
Downey (CA) and Denver sites 52
21 Diurnal behavior of 1,1,1 trlchloroethane at San Jose site
during April, August, and December t985 54
22 Diurnal behavior of 1,1,1 trichloroethane at Downey
(CA) and Philadelphia sites 55
23 Diurnal behavior of trichloroethylene at San Jose site
during April, August, and December 1985 57
24 Diurnal behavior of tetrachloroethylene at San Jose site
during April, August, and December 1985 59
25 Diurnal behavior of tetracnioroethylene at
Philadelphia, Staten Island, and Downey sites 60
26 Diurnal behavior of aromatic hydrocarbons at
Southern California site (Downey site)........ 62
27 Mean diurnal concentration of aromatic hydrocarbons
relative to benzene (ppb/ppb) at Southern
California site (Downey site) 63
28 Diurnal behavior of benzene at San Jose site
during April, August, and December 1985 66
29 Benzene and toluene trend in the atmosphere of
the South Coast Air Basin of California 67
30 Diurnal behavior of PAN at Philadelphia,
Downey, Houston, and Denver Sites 70
31 Diurnal behavior of PPN at Downey, Houston, and
Denver sites 71
32 Duirnal behavior of formeldehyde and acetaldehyde concen-
trations in Southern California (Downey site).. 76
v11
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TABLES
Number Page
1 List of chemicals measured in this study 1
2 Environmental mobile laboratory Instrumentation 5
3 Analytical conditions for the analysis of
selected toxic chemicals 9
4 Permeation rate data for generating primary standards 12
5 PPM level primary standards in air 13
6 Field sites and measurement schedule 20
7 Production, emission and usages of selected chemicals 23
8 Atmospheric concentrations of measured chemicals for
Philadelphia and Staten Island 24
9 Atmospheric concentrations of measured chemicals for
Downey, Houston, and Denver 25
10 Atmospheric concentrations of measured chemicals for
San Jose 27
11 Estimated average background concentration of
trace species at 40°N for year 1985 30
12 Estimated daily loss rates (%) of
selected trace chemicals 31
13 Midlatitude background concentrations of some aromatic
hydrocarbons in remote marine and continental atmospheres.... 68
14 Ambient formaldehyde levels from selected locations 73
15 Ambient acetaldehyde levels from selected locations 74
16 Mean ambient concentrations of selected chemicals at the
San Jose site during April, August and December 1985 79
17 Mean ambient concentrations of select chemicals based
on revisits in different seasons and years 80
v111
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ACKNOWLEDGMENT
Research for this project was funded by the U. S. Environmental Protec-
tion Agency (EPA) under Cooperative Agreement CR 809282. He thank Dr. Larry
Cupitt, the EPA Project Officer, for his participation and encouragement in
this errcrt. Ms. Robin Redmond, Mr. William Viezae, and Dr. Bruce Cantrell of
SRI International and Mr. Enrique Agorio of Manpower provided invaluable
support during the conduct of these field studies. We are thankful to many
individuals for the use of special facilities during these experiments. The
help provided by Ms. M. Gibson of the San Jose Historical Museum is gratefully
acknowledged.
1 x
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SECTION 1
INIRODUCTION
Over the last three decades large amounts of a growing number of syn-
thetic organic chemicals have been released into the ambient environment. In
many cases, virtually all of the synthetic organic chemicals produced are
released into the environment as a necessary result of U3e. Urban atmospheres
contain 3 complex mixture of a large number cf chemicals, many of which are
known to be toxic at concentrations significantly higher t^o. those encoun-
tered in typical ambient atmospheres. The degree to which the general ambient
environment contributes to human cancer is a matter of both active research
and debate. A report from the Office of the U.S, Svrgeon General concluded
that "toxic chemicals are adding to the disease burden of the United States in
a significant, although as yet not precisely defined way" (U.S.S.G, 1980).
The process of understanding the risks associated with expo3urr to potentially
hazardous chemicals requires a determination of the ranges of concentrations
that can be found in the ambient air.
This study was initiated primarily to measure the atmospheric concentra-
o
tions of a variety of potentially hazardous gaseous organic chemicals at
selected urban locations unde" varying meteorological and source-3trength
conditions. This study complements and extends a similar study previously
completed (Singh et al, I983e). These chemicals were sampled and analyzed on-
site, using a suitably outfitted mobile laboratory. The overall program of
analytical methods development, field measurements, data collection, and data
analysis is expected to provide information that will permit a better
assessment of the atmospheric abundance and chemistry of this potentially
harmful group of chemicals.
The term "hazardous chemicals" as used here is not intended to imply that a
proven human health hazard exists. In most oases, toxicity studies are
incomplete or Inconclusive, and Involve extrapolation of animal data to
humans.
1
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TECHNICAL REPORT DATA
(Please reed /nuruclwni on the reiene before completing)
1 Ht'OdT NO
EPA/600/3-86/047
2
3 RECIPIENT S,ACCESSIOiyNO .
P33 6 % 3 y t) 1 0 /as
4 Tl"..E AND SUBTITLE
TOXIC CHEMICALS IN THE ENVIRONMENT:
S REPORT DATE
August 1986
A PROGRAM OF FI ELD MEASUREMENTS
6 PERFORMING ORGANIZATION COOE
7 AUtHOniS)
H. B. Singh, R„ J. Ferek, L. J. Salas
and K. C. Nitz
3. PERFORMING ORGANIZATION REPORT NO
O PERFORMING ORGANIZATION NAME AND ADDRESS
SRI International
333 Ravenswood Avenue
Menlo Park, California 94025-3493
10 PROORAM ELEMENT NO
C9TA1B/01 - 1537 (FY-86)
11. contmact/ohamt i\id.
CR 809282
12 SPONSORING AOPNCV NAME AMD ADDRESS
Atnospheric Sciences Research Laboratory-RTP, NC
13. TYPS OP REPORT 4NDP8RIOO COVERED
Final (4/82-6/86)
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
14. SPONSORING AGENCY CODE
EPA/600/09
10 ftWP^ttMSNTARV NOTES
10 ABSTRACT
A series of field measurements was carried out In six U.S. cities to assess
the magnitude and variability of the concentration of twenty-nine potentially toxic
air pollutants. The measurements wore conducted on a 24-hour-per-day basis for
periods of 1 to 3 weeks in each the following cities: Philadelphia, PA; Staten
Island, NY; Downey (Los Angeles), CA; Houston, TX; Denver, CO; and San Jose, CA.
Three separate periods of sampling were conducted in San Jose during different
seasons of the same year. The chemicals which were measured included chlorofluoro-
carbons, halomethanes, haloethanes, halopropanes, chlorinated alkenes, aromatic
hydrocarbons, organic nitrogen compounds, and aldehydes. For most species
average concentrations were less than 5 parts per billion (v/v). Aldehydes and
aromatlcs were more plentiful, but they still averaged less than 25 ppb. Maximum
measured concentrations were typically 5 to 10 times the mear; values. The data
were analyzed and compared with historic data in order to examine for trends.
Variations associated with meteorological Influences were so great as to mask
any potential seasonal or longer trends which may have been present 1n the
limited data set available 1n this and a previous study. Diurnal patterns 1n
the distribution of aromatic hydrocarbons 1n southern California suggest that,
even 1n February, hydroxyl radical concentrations 1n the lower troposphere may
re.JCh 2.6 x 10° molecules cm"3.
17.
KEY WORDS AND DOCUMENT ANALYSIS
1 DESCRIPTORS
b.IDENTIFIER*'OPEN ENOPO TERMS
c COSATi Field/Group
IB D ITRlBUTlON * 'ATEMENT
f'.ELEASE TO PUBLIC
10 SECURITY CLASS (T.Ut fitpon)
UNCLASSIFIED
21. NO OF PAGES
103
30 SECURITY CLASS
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SECTION 2
OVERALL OBJECTIVES
The major objective of thi3 study was to perform a series of ambient
field experiments in which atmospheric concentrations of a variety of selected
hazardous organic chemicals ,were to be measured on around-the-clock basis, at
a variety of urban locations, under varying meteorological conditions, and in
different seasons.
To accomplish the above objective, analytical procedures were developed
and a mobile environmental laboratory was equipped to perform onsite analysis
of selected trace chemicals. Eight field experiments were performed in six
cities to develop a reliable data base which could be used to better under-
stand the atmospheric concentrations diurnal and seasonal behavior of these
chemicals. These data are processed and interpreted ir. the context of
sources, 3inks, and the chemistry of the molecules. The effect of season and
meteorological conditions was investigated.
2
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SECTION 3
ANALYTICAL METHODOLOGf
Many of the procedures used hero have already been described In Sing?* et
al (I983e), and are therefor© described only briefly. Table 1 lists
chemicals that were treasured during thla study. Aa has been reported
et al, 1983s Singh et al, 19&2), cost of these chemicals ar® rautneenlC;^
carcinogenic, or can for-a products in tho air that havo these projiartlca,
FIELD INSTRUMENTATION
Because of problems associated with surface reactions, it is widely
recognized that the integrity of an air sample Is boat maintained whori only
nominal aaounts of air samples are collected, and the time becweon collection
and analysis is kept to an absolute minimum. Our on-site field analysis
program was devised to meet these rcqulrements. Table 2 summarizes the? equip*
ment that was available in our mobile laboratory for the conduct of this
study. This laboratory was air-condltloned for temperature control* snfl
operated on a 220-V, 80-A circuit. Provision was also made for operating
110-V input. A 200-m electrical cord was always used to station the labc*TA»
tory away from the electrical aourco or power cole. The sampling manifold vaa
all stainless steel witn a variable inlot height. (It all cases, tho sampling
manifold was adjusted to be higher than nearby structures: A typical annl^W
inlet heig't was 5 m above ground.) For pumping and pressuring air samples, «
special stainless-steel metal bellov3 compression pump (Model MB l?>3)
always used. For the analysis of aldehydes, surface air wa3 sampled in aw
all-glass apparatus.
EXPERIMENTAL PROCEDURES
For all of the halogenated speclos and organic nitrogen confs.'Hinos showh
In Table 1, electron-capture detector (ECD) gas clu-omatography (GC) wns tho
primary means of analysis. The arcaatlc hydrocarbons were measurod uaiii<
flame-ionization detector (FID) gas chromatography (Slr.gh et al,
3
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TABLE 1. LIST OF CHEMICALS MEASURED
IN THIS STUDY
Measured Cheraical9
CHLOROFLUOROCARBONS:
Trichlorofluoromethane (F—11)
Dichlorodifluoromethane (F-12)
Trichlorotrlfluopoethana (F-113)
Dichlorotetrafluoroethane (F-1i*1)
HALOMETHANES:
Kethyl chloride
Methyl bromide
Kethyl iodide
Methylene chloride (Dlchloromethane)
Chloroforta (Trlchloromethane)
Carbon tetrachloride
HALOETHANES AND HALOPROPANES:
Ethyl chloride
1,2-Dichloroethane
1,2-Dibroinoethane
1,1,1-Trlchloroethane
1 ,2-uichloropropane
CHLOROALKEKES:
Triehloroethylene
Tetrachloroethylene
AROMATIC HYDRXARBONS:
Benzene
Toluene
Ethyl benzene
m/p-Xylene
o-Xylene
3/^-Ethyl toluene
1,3.5-Trimethyl benzene
1,2,^-Trioet.hyl benzene
OXYGENATED SPECIES:
Peroxyaceiylnltrate (PAN)
Peroxypropionylnitrate (PPN)
Formaltiihyde
Acetaldehydc
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TABLE 2. EIJVIROMENTAL MOB I Li. LABORATORY INSTRUMENTATION*
Instrument
Featuras
/¦nolyolo
Pork.In Elsar 3920 CC1
2 ECDt, 1 duel FID?
Trace constituents
Porkln Clear 3920 CC2
7 ECO. 1 dual FID
Trace constituents
Pert.In Elner 3920 CC3
(capillary coluso CC)
2 ECD, 1 dual FID
Trace constituents
Coulooetrlc t~«l EC-Cc
Coulaaetric ECD
Halocarbons, PAN, PPN.
COCI]; calibration
Spectraphyslcs HPLC 8700
(variable wavelength
SP3400 detector)
HPLC0
Aldehyde*
Beckoan 6800
FID
CO-CH4-THC
llorlba A1A-24
mdir"
CO, C02
Bendlx 8101-B
Ched luminescent
HO, NOj
Mo ill tor Lcba Model 8i 0E
Ch cai1ualnescent
KO and UOj
Daslbl Modal 1003 AH
Ptiotoaetric principle
°3
AID Model 560
Cbealluol nascent
°3
Bend Ik 8002
Cbeol1ualnoeceat
°3
Epploy pyranceeter
Solar flua
Eppley UV radlooeter
Ultraviolet radiative flux
Miscellaneous ceteorologlcal
equlpoent
Wind speed, wind direction,
tes?, pressure, dew point,
relative hualdlcy
Auto Lob IV Data Systen (No. 1)
CC data
SP-&000 Multichannel Data Systeo
(No. 2)
CC data
HP-3390 printer plotter
Dlglteo Data Systea (Ho. 3)
All continuous air quality
and oeteorologlcal data
*Uote: Soapllng of all trace organlcs Is performed trim a stainless-steel
oanlfold. A Teflon® oanlfold Is used for lnorgaivlcs (e.g., 0], NO, NO*).
Flnnlgan 3200 CC/MS available to this project at SRI.
telectron capture detector.
^Flaoe Ionization detector.
®H1 (*ti performance liquid clirooatogroph.
Nondicpcrslve inirared.
5
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Formaldehyde and acetaldehyde were measured by analyzing the 2,1 dlnitro-
phenylhydrazine derivatives formed by reaction of 2,1 dinltrophenylhydrazlne
(DNPH) with aldehydes, using high-performance liquid chromatographic (HPLC)
methods (Kuwata et al, 1979; Kuntz et al. 1980; Fung and Grosjean, 1981; Salas
and Singh, 1985).
All six GC channels were equipped with stainlsas-ateel sampling valves,
and could be opsratod either with a direct sampling loop or with a preconcen-
tration trap. In no ln3tanoe was a sample size of greater than 1 liter
used: In most cases, sample volumes of 500 ml or less were satisfactory.
Sample preconcentration was conducted on a 1-lnch-long bed of 100/120 mesh
glass beads packed in 1/16-inch diameter stainless-steel tubing maintained at
liquid oxygen temperature. The glas3 beads could be replaced with an equiva-
lent length of SE-30 packing (3 percent SE-30 on 100/120 mesh acid-washed
chromosorb W) or glass wool, with completely satisfactory results. Descrption
of chemicals from the preconcnntratlon traps was accomplished by holding the
trap at boiling-water temperature and purging with carrier gas. Additional
details have been earlier provided by Singh, et al (1979a, l983e).
Two types of sampling procedures were employed. During the first five
field programs, an on line 2-lltor SUMMAR polished stainless steel canister
was pressurized to 32 psi during a 3 to 5 minute period, and this air was used
for GC analysis.
During the last 3 field programs (at San Jose, CA), a different sampling
arrangement was used in order to provide 2-hourly Integrated samples (Figure
1). A 6-llter SUMMAR polished stainless steel canister was slowly pressurized
to approximately 27 psi, using a metal bellows pump followed by a pressure
relief valve (set at 28 psig), and a mass flow controller PFD Model 911 set at
150 cc/rain. Prior to sampling, the canister was evacuated by a vacuum puap to
less than 0.08 atm. It was thon slowly filled (at 150 cc/min) to approxi-
mately 27 psig. In this manner, about 18 liters (ST?) of air were pumped into
the 6-liter canister over a 2-hour period. Because the canister was evacuated
to 0.08 atm, less than 3 percent of a previous saraple was carried over Into
the next sample Introduced Into that canister. The sampling system was
configured with three canisters and switching between them and between vacuum
6
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TO
OC TRAPS
FROM
SAMPLE
MANIFOLD
DIRECTIONAL
VALVES
BHUTOFF
~ VALVES
ISO ee/ndn
FLOW
CONTROLLER
VALVE
4-WAY
VALVE
VENT
TO
VACUUM
PUM?
79-p«f|>
PRESSURB
RELIC
METAL
BELLOWS
PUW
B-LfTES CAK?*'!STER8
Figure 1. Assembly for * 2-h Integrated air sample collection In 6-liter itainless stosl canisters.
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or pressure pumps was accomplished by means of stainless steel directional
valves. The pressure relief vai"» allowed most of the flow (approx.
10 t /mln) to be vented upstream of the flow controller. In this way, the
metal bellows pump was kept continuously flushed and cool, preventing degra-
dation or contamination of the sample. Two tests were conducted to check for
contamination from this pumping arrangement. One used pure Ng from a cylinder
instead of sample air. Analyses cr. all GC channels showed no halocarbon or
aromatic contamination added by the metal bellows pump, flow controller, or
other components in the sampling line. A second test was conducted using a
35-liter canister pressurized to 35 psig with ambient air. Analyses of the
air sample on all GC channels before and after passage through the sampling
train showed no change in any of the chemicals of Interest.
The preconcentratlon and analysis procedure was identical In both cases.
Tests were performed to ensure that no contamination occurred during this
sampling procedure. The volume preconcentrated (dry basis) was measured by
noting the pressure change in a vessel of known volume connected to the trap
exit. A high precision pressure gauge (±0.05 psl) was used to monitor this
pressure. It was determined that for sample volumes of 200 ml or more, an
accuracy of ± 2 percent could be easily obtained.
Table 3 summarizes the routine methods used for the analysis of trace
species. The GC and the HPLC conditions used are both stated. Because of the
dominant water response of the ECD, a pre-column NaflonR drier was Inserted to
remove water for halocarbon analysis. No drier was used for the analysis of
aromatic hydrocarbons, FAN and PPN. The latter two do not require any precon-
centratlon step, and were measured with a direct 5-ml air injection. For the
aldehyde DNPH-HPLC analysis, the technique described by Kuntz et al (1980) was
employed. The sampling reagent was prepared by dissolving 0.25 g of purified
DNPH in 1.0 liter of HPLC-grade acetonitrile, anc adding 0.2 ml of concentra-
ted sulfuric acid to this solution. DNPH was purified by repeated recrystalll-
zation (at least three times) from HPLC-grade ocetonitrile. A 7-ml aliquot of
this reagent solution was transferred into a bubbler and cooled with the help
of an icewater Dewar flask. During ambient sampling (60 liters), an air-flow
rate of 0.5 llter/min was maintained for a typical sampling period of two
8
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TABLE J. ANALYTICAL COMDITIOBS FOB THE ANALYSIS (F SELECTED TOXIC CHEMICALS
CC or KPLC Coluon
Detector
Typical
Carrier
Typical
Stksple
Ko,
Description
Teop.
CC)
Species Measured
Type
Teap.
CC)
Flow Rate
(ol/nln)
Size
(q1)
Resarka
I
6 ft * 1/8 in. SS.« 201
SP2100, O.H DC 1500 on
100/120 cash Supelcoport
»5
CHCKi CH,CC),i CC1,(
cls-CXlCflCl| C,HC1,|
CHjClCHClji CH,BrCHjBrj
C2C1D1 CHjCICClit
CHCljCHClCH^ClCHClCHj
Electron
capture
275
*0
500
Precoluan NaflonOD
water trap
2
33 ft I 1/8 in. Nl, 20}
DC 200 on 80/100 msh
Supelcoport
*5
CH,C1| CHjBrj C^CClji
ch,ii cci,ri cci/,1
CClFjCClyFt CCIPjCCIFji
CjHcCli CH,C1,|
CfljClCHjCl; c9,cci3i
ccr„i c^ciji r2ci,
electron
capture
275
25
500
Precoluxn Haf lonOD
water trap
3
6 ft x 1/8 In, SS, 101 N,
N, -bto (2-cjranoatnjrl)
Fornaalde on Chrooosorb
P (acid washed)
65
C6H6i C4»5CHj, a/p/o-
c6H,ichj)2i
1.3.5 CjH,(CH}),i
l.2.» C6«J(CHJ)j
Place
Ionization
275
<5
500
Ho water trap
4
10 In i 1/1 In, Teflon,
51 C5 100, on 60/80 uesh
Chrooosorb U (acid
waslicd
30
Pi*. PPB
Electron
capture
30
60
5
No water trap;
direct injection
5
• rt K 1/4 In SS,
sphorsorb 003-10
30
HCKO, CHjCKO
Variable wave-
length detector
sat at 360 rb
30
1.5
O.OJ
Isooratlc mode, 3&1 H^O,
611 acetonltrlle SP nods
8700, SP 3'QO detector
"Stainless Steel
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hours. The sampling reagent was added to compensate for any evaporative
losses. After sampling, a 2.0-ml aliquot of the reagent solution was
transferred into a heavy-walled Teflon-capped reaction flask, warmed at 7"i°
for 20 minutes, and then cooled to rooa temperature. The DNP-hydrazore
derivatives were analyzed with a Spectra Physics HPLC (Model 8700) equipptd
with a 1 ft x 1/4 inch SS Spherosorb 0DS-10 column, and a variable-wa velengtli-
detector (Model 3400) set at 360-nm wavelength. The HPLC was used in en
lsocratic mode with a solvent flow rate of 1.5 ml/oin. A 36 percent H20, tU
percent acetonitrile, solvent gave the best resolution of the two hydrozones
of interest. A 10-ui sampling loop was used for HPLC analysis. Typical
analysis tine was less than 10 minutes.
The Identity of trace constituents was established by using the following
criteria:
0 Retention times on multiple GC columns (minimum of two columns)
• EC thermal response
9 EC ionization efficiency
Details of these compar1sons for halocarbon species, organic nitrogen com-
pounds, and aromatic hydrocarbons have already been published (Singh et al
1979a; 19S3e).
CALIBRATIONS
Primary Standards
Calibrations for all species were performed using three basic methods:
• Permeation tubes
e Multiple dilutions
• Gas-phase coulometry.
As reported earlier (Singh et al, 1979a; 1983e), permeation tubes provide (
reliable means to generate low-pp^ primary standards for a jl^nificant number
\
of chemicals listed in Table l. Permeation tubes (8- to 1')-cm long) con-
structed from standard FEP or'TFE Teflon*1 tubing of varying thicknesses, were
obtained commercially for many trace constituents of interest. Each permea-
tion tube was contained in a specialized glass holder. Based on our previous
10
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experience, we conduced that some permeation tubes could operate satisfac-
torily only at high temperatures. Therefore, two temperature baths maintained
at 30.0°C t 0.05°C and 70.0°C ± 0.1°C were installed. The 30°C bath was a
water bath, and the 70°C bath was an oil bath (later replaced by a solid
aluminum block machined to hold glass chamber inserts). All permeation tubes
were contained in specialized holders and were purged continuously with a
prepurified gas (helium, air, or nitrogen) flowing at 50 to 80 ml/rain. Per-
meation tubes were weighed approximately once a week on a semi-micro (10~^g)
balance. These weighings were done before, during, and after the field
experiments. The constancy of the permeation rate over a period of many
months could be established. A large-volume mixing chamber was Installed at
the permeation tube exit to allow for complete mixing. Samples were withdrawn
from the mixing chamber using all-glass syringes. Our previous results (Singh
et al, 1983e) showed that the permeation tubes demonstrated excellent
linearity of permeation rates, and proved to be a reliable means to generate
primary standards. Table 4 shows permeation rate data for a variety of
chemicals of Interest. Host of these permeation tubes can be used to prepare
standards directly at parts per billion (ppb) concentration levels. Batch
dilutions were carried out to reduce these concentrations by a factor of 10^
to 10^. These were ^rformed by injecting a known volume (typically 10.0 ml)
of the high concentration mixture into an evacuated precleaned electropolished
stainless steel container of 1- to 5-liter size, followed by pressurlzatlon
with dilute ga3 to 40 psi. Over a wide range of concentration levels of low
ppb's and low ppt's (parts per trillion), the frequency-modulated ECOs that we
used were linear. The linearity of the FID over a much larger concentration
range is well known.
In addition to permeation tubes, standards were obtained from Scott-
Marrin (Riverside, California). These were obtained at higher concentrations
(5 to 10 pprr,) for long-term stability. Table 5 lists the chemicals, the
standard concentrations, and the cylinder materials. All of the chemicals
were stored in aluminum cylinders except those containing CH^CI, which were
contained In 3tainless-steel cylinders. Extreme care was required in select-
ing cylinder materials; some of the chemicals (e.g., methyl chloride) form
unknown chemical complexes that might react explosively with aluminum (Private
11
-------
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-------
TABLE 5. PPM LEVEL PRIMARY STANDARDS IN AIR*
Concentration
(ppm)
Long-term
Stabillcyf
(2-year period)
Cylinder
Standard and Coapoundf
Type
Size
(ft3)
SI
1,1,1 Trichloresthane
Carbon tetrachloride
1,2 Oibrcsoechans
HexAchloroethane
5.0
5.2
5.0
0.8
E
E
E
U
Aluiaitsus
30
S2
Monochlorobenzene
o-Dich1orobenzene
5.0
5.0
P
P
Alualnua
150
S3
Benzene
Toluene
5.0
5.0
E
E
Aluslnus
150
S4
Methyl chloride
Methylene chloride
1,2 Dichlorosthane
10.0
10.0
10.0
E
E
E
Stainless
steel
30 )
S5.
Trlchloroethylene
Tetrachloroethylene
Chi or of oris
10.0
10.0
10.0
E
E
E
Alualnua
I
30
S6
Etldne
Propane
n-Butane
4.07
5.03
4.95
E
E
E
Aluminum
i
150
S7
Methyl chloride
Methyl brialde
Methyl Iodide
10.0
10.C
5.0
E/S
E/S
E/S
Stainless
steci.
30
•Obtained on order froa Scott-Marrin, Inc., Riverside, California.
^For all of these chenlcals (except C^H^ and C^HjCHj) satisfactory peraeatlon
tubes were also operational. Therefore, a nojorlty of these standards
were used aore as secondary standards than as primary ones. For arcsnatlc
hydrocarbons, the Scott-Karrln standards were used as primary standards.
^E: Excellent; P: poor; U: unknown; E/S: Excellent over the short term;
long-term tests have not been made.
13
-------
Communication—Scott-Marrin Inc.). Chlorobenzenes deteriorated rapidly in
these cylinders, other halocarbons and hydrocarbons were found to be
extremely stable. The toluene response deteriorated at a slow rate of
3 percent per year. Benzene was much more stable and did not show any
perceptible loss.
All of the eoEoarclally-obtained standards were rechecked with our per-
meation-tube standards when this was possible. The comparisons ware found to
yield excellent results (t10 percent). The aromatic hydrocarbon standards
were checked for carbon response against those available from the National
Bureau of Standards (KBS) and found to agree within ±5 percent. For other
aromatic hydrocarbons, carbon response derived from benzene response was used.
PAH and PPN were measured with the help of a dual ECO gas phase eoulo-
oeter according to the procedures described by Singh et al (1983d). It is
estimated that this analysis is accurate to ±20 percent.
Secondary Standards
Except for the aromatic hydrocarbons, it was not possible to use primary
standards during field operation. Therefore, an optimal scheme that depended
on the use of secondary standards was devised.
A 35-liter and several 5-liter (as backups) SUMMAR polished stainleos-
steel samplers were filled with urban air samples to a pressure of 35 to ^0
psi. These vere allowed to stabilize for one to two days and then analyzed by
comparing them against the primary standards. The 35-liter pressurized sec-
ondary standard was then used for field operation: Each X channel was cali-
brated one to two times a day with this secondary standard. The stability of
nearly all species over a period of several days was found to be excellent
(Singh et al, 1983e). Sone species, such as PAN, PPN, and occasionally CCl^,
could not be stored for any reasonable length of time. This was not a serious
hindrance since other chemicals could be used to ascertain the constancy of
the ECD and the FID responses during field operations. All of the Scott-
Karrln standards were also carried on board afi^r these had heen diluted to
low-ppt> levels. They were also usea as secondary standards (in addition to
1 U
-------
the collected air samples). The stability of the diluted Scott-Marrin cylin-
ders (in polished 1- to 5-liter stainless-steel vesrels) was found to be
excellent. Analysis of these before field experimentation, during field
studies, and after the completion of field studies did not show a change from
the measurement precision under field conditions. In the case of aldehydes,
all calibrations had to be performed in the field.
QUALITY CONTROL AND ASSURANCE
Two major factors were critical in establishing the quality of the
acquired data: the accuracy of primary standards, and the precision and
repeatability of measurements. As stated earlier in this section, the primary
standards commercially obtained were compared with our permeation tubes, which
can be routinely used to obtain reliable standards within errors of 10 per-
cent. The aromatic hydrocarbon standards w?re compared with NBS propane
standards and found to be accurate to within ±5 percent. The cross-
calibrations between SRI-generated standards and Scott-Marrin standards typic-
ally resulted in differences cf about ±10 percent or less. The use of second-
ary standards, at least on a dally basis, clearly demonstrated the excellent
precision that was obtainable during field studies: The precision of reported
field measurements is estimated to be better than ±15 percent. Because of the
unavailability of standards at low concentrations, the overall accuracy of
individual measurements cannot be ascertained. We estimate that in most cases
the overall accuracy of data are within ±30 percent. This is established
based on a number of audits performed by Northrop Services Inc. (NSI) under
contract to EPA arid utilizing somewhat different sampling and analysis
techniques (Shepson and Kleindienst, 1986; Shepson et al, 1986). Figures 2-7
show a comparison of SRI ano NSI data for chlorcat :ane, benzene, toluene and
tetrachloroethylene at the Philadelphia ard San Jose sites. Comparisons with
other chemicals could not be performed as these data were not available from
NSI. Nevertheless, data for the four chemicals clearly show that the two
methods track the concentration variability reliably, and the measured values
agree within + 30J over a wide concentration range.
15
-------
600-|
500-
-------
fi
-i—i—i—i—r—1—r—I—i—i—i—i—i—i—i—i—i i ¦ i r'l-^—r-1
& 2 4 • S 10 II 14 16 13 10 12 24 2 4 6 0 10 12 14 18 18 20 71 24
th
12/18 11/19
Figure 4. Toluene concentrations at the San Jo £3 si to et
measured by SRI and NSI.
»-
25-
20-
15-
10-
5-
OHH
© SRI
So?
§
o
o
CD
o
'T T I I i I I I I I i i i I I i i ' I i i i i
0 2 4 6 B 10 12 14 16 IS 20 22 24 2 4 6 B 10 12 14 16 ID 20 2? J4
12/18
12/19
Figure 5. Benzene concentrations at the Philadelphia site as
"leasured by SRI and NSI.
17
-------
o
O MSI
O SRI
$
o
} °
J.
® a
kwtotesad
4 0 12 16 20 24 4
12 16 20 24 4 6 12 16 20 24
th
an 4/3
Figure 6. Tetreehloroathylene concentrations at the Philadelphia sits
os measured by SRI ond NSI.
Q
5
OWI
© SRI
O
©
•*
$
^ ©
0)
A ^
9
O
^ Q© ®
®o
2 4 6 B 10. 12 14 16 IS 20 22 24 2 4 6 8 10 12 14 1t> 16 20
17/19 12/19
Figure 7. Tetrochloroethylene concentrations at the San Jose site as
measured by SRI and NSI.
18
-------
SECTION U
FIELD MEASUREMENTS
Eight field studies were performed In six select urban environments in
the continental United States. The sites vere chosen In consultation with the
project officer and were located in the following cities:
o Philadelphia, Pennsylvania
© Staten Island, Hew York
o Downey, California
9 Houston, Texas
• Denver, Colorado
• San Jose, California
Wltnin the above cities, specific sites were chosen that represented an open
urban area. Large point sources or topographical features that could affect
the representativeness of the measurements were avoided. Every attempt was
oade to select sites that could be expected to be indicative of general pollu-
tion levels prevalent in the area. Practical constraints such as power and
shelter availability also played a role in the selections of sites. It oust
be emphasized that only one site within each of the selected cities was moni-
tored. The data collected here, while perhaps typical of general ambient
environment, are truly representative only of the specific site monitored.
The site locations, and the periods of field measurements, are shown in
Table 6. On the average each field study was of roughly two weeks duration,
with a range of 1 to 3 weeks. Based on our past experience (Singh et al.
1982; 1983e), we believed that significant night and daytime differences were
likely in the abundance of organic chemicals. Thus we conducted that despite
the logistical difficulty, a 2t-hour measurement schedule offered the most
efficient means tc collect the maximum amount of data needed to characterize
the burden of toxic organic chemicals In the ambient air. In addition, night
abundances of trace chemicals were llkPly to provide important information
about the sources and sinks of measured species. Therefore, a 24-hour-per-
day, seven-days-a-wcek measurement schedule was followed during all field
programs.
19
-------
TABLE 6. FIELD SITES AND.MEASUREMENT SCHEDULE
Experiment
No.
City
Esperlntent
Period
Site Address
1
Philadelphia, PA
1-22 April 1983
Lycoming end Castor St.
2
Staten Island, NY
25 April - 1 Hay 1984
Wild Ave. and Victory
Blvd.
3
Downey, CA
18-27 February 1981
7601 East Ispcrlal Rancho
Los Amigos Hospital
1
Houston, TX
9-17 March 1981
Mae St. and 1-10 Frontage
Road
5
Denver, CO
21 March - 1 April 1981
Marlon and E. 51 St.
6
San Jcse, CA
1-16 April 1985
Aloa and Sentcr Road
(San Jose Historic Kuseura)
7
San Jose, CA
12-21 August 1985
kla& and 3&ntcr Road
(San Joss Historic Kuseua)
8
San Jose, CA
1 3"21 Decco&w 1935
Aloa arjS Scaler IJ&ad
(San Jcos Misiorie ttus&ir:)
-------
The Philadelphia site wa3 selected by the U.S. Environmental Protection
Agency (EPA), This Is among the few sites that were chosen in a preliminary
Attempt, to establish a national tox'.c chemical monitoring network. The da*:a
presented here thus complements, and can be compared against, routine measure-
ments that oontlnuo to be conducted at this site by the EPA. The next 1 sitas
(Stoten. la land, Downoy, Houston, and Denver) represented altos that had te'in
previously sataplcd In spring/suaaer months. (Dotmoy was substituted for Los
Angelea olnco tha Los Angeloa site was no longer available.) Tho purpose here
was to rovlolt these sites in different seasons and years.
The San Joso alt* was selected because of great ooncern in the "Sillocn
Vftlloy" aroa about exposure to chemicals used by the electronics industry.
Many of tho chemicals of concern were being measured in this study. Additior-
ally it woa folt that these data could prove to be of great value to the EPA
Integrated Environmental Management Program (Hinman et al, 1985) that is being
conducted In thin area with a focus on water contamination. Prior to our
studies there was a virtual absence of asbient air data from the Silicor
Volley areo.
Additionally, the three studies at the San Jose site offered an opportu-
nity to look at seasonal differences In an area which is strong.1 y Influence'
by provnlllng synoptic conditions. The winter study in San Jose (Expt. No. 8]
took plftco during an unusually strong high pressure weather system in which i
largo stagnant air mass" covered moat of the Western U.S. A low-level lnver
alon trapped pollutants In the entire Santa Clara Valley, and drove carbo^
monoxide conoontrat ana to the third highest levels on record (Bay Area Al:
Pollution Control District).
A3 w.ta anticipated, these field studies encountered a wide range o
woathor and cllmatlo conditions (stagnation, snow, rain, clear skies, etc.
and thcroforo should bo extremely useful In establishing the ranges of concen-
trations encountered In tho ambient air of a variety of urban atmospheres.
21
-------
SECTION 5
ANALYSIS AND INTERPRETATION OF FIELD DATA
The data collected during these studies have been compiled, validated,
and statistically treated. A computer-compatible master data file has been
created. In addition to computer processing of field data, ye have alao
analyzed data to study the diurnal variations that are typically obssrvsd.
The data generated in this study, however, when further analyzed in the con-
text of prevailing meteorology and source inventories, have the potential to
add significantly to our knowledge of urban atmospheric chemistry.
Table 7 is presented to give a general idea of the yearly U.S. produc-
tion, average emissions, and typical use patterns of important chemicals. A
major source term for each of the chemicals has also been asal&ied, based on
available Information. Table 7 provides a preliminary basis for comparing the
relative abundance of chemicals in the ambient atmospheres.
Statistical Luamaries of all field data are presented in Tables 6, 9, and
10. All concentrations are expressed in units of parts per trillion by volume
•1 ?
(pptv *10 v/v). Quantities tabulated are the means and standard deviations
(one slgaa), maximum and minimum conconcentratlons, and the number of positive
(nonzero) measurements as well as the total number of measurements performed.
These statistics Include all measured data. When the concentration was below
our detectable limit, it was assigned a value of zero. In most cases values
were below detection only infrequently (Tables 8-10). Additionally, plots of
concentrations vs time and mean diurnal profiles have been constructed for all
species, and some of these will be presented In the following sections.
Average diurnal patterns were calculated by stratifying the data according tc
the sample collection time. Except for San Jose, all of the data from the
complete sampling period were grouped according to the 3-hour interval
(midnight to 3 a.m., 3 a.m. to 6 a.m., etc.) in which the sample was
collected. Arithmetic means and standard deviations were calculated for each
time Interval and are plotted at the midpoint of the Interval (at 1.5 hours,
U.5 hours, etc.) In the plot3, the means are represented by a symbol, while
the plus and minus one-algma standard deviation values are shown as connected
22
-------
TABU 7. PtODUCTLON, DKS5I0M AM0 USACCS OF SfLCCTCD CHEMICALS
Coepovnd
Sogftt4
u
for
(¦11
5* Production
Indicated Ictfi
Ion oatrtc cona >
taio»loo*t
(perctnt)
Ja«ft« aod Looarfco
Hathyl chlorUi
At MO)
0.20 U976)
k - io
1) |^r(«ot of production uMd For uouUriur*
of •lllcooM sod lotraaattiyl land lnt«r«adl-
tco^i l«c|« natural aovrta (•) tilllM
CMt/]lf) IdmtUlid lo the oca no
Hattafl bra»lda
Al H(0)
0.02 (197*1
Sot] (ualtMti ocorale oowrc* il(olflcMllr
Larcot thn mi aatfa «MobIcm lo
Nttkyl lodld»
1(0)
».o
•
A Mural 99M9H ecem of 20*3 allllo*
tCOft/fT ll CStlcOlttd
ftetbpltlM cMerldo
A
0.30 (1979)
CO - w
33 poiCMt cf protocilw um4 fot piUt
teofctoa ao4 aqItcm doertsalcs
CMoroforo
A
0.16 (t«7S)
J - 10
Raoilfiecar* of llnrocirte««U
Car boo totracfelorldo
A
0.J4 (1979)
J - 10
n»Mf*ct«r« ot HaorMfirtoM.il ond -t2
Cclryl chlorldo
A
0.) (It7l)
23
6) porcoM <0M(t«4 !• fto of
letroittyl laod
1,2 DltKlerMtlMM
A
4.0 (1976)
*2
87 porcont noad for vinyl cMortd^ op no oar
ajratb««lai lUo «m4 (or tte pro4»ctt»o of
ttilortrhrlaMft sod chleiosthieaa; ibowi 0>4
aftlltoo coos p«r jro«f" «a«4 (tr totd irmni*
Ins In cateoofellao
1,2 0Uro««thaM
A
O.t (1976)
5- Ji
Ho)er (»mUm oMltm for laod eeovt«|if|i
llM uMd oo • fmtlgaai
l.l.l TrtcMorMilMM
A
0.J (1970)
:m
70 p«reaet of pro^BiiUa it»d (or mii!
cl««al*8t ewt octaf ap^ltlUftu *Uo M«uU
lo direst rala«M
Vifc'i chlorldo
A
3.2 (t?78>
2 - J
Wood (or polyctr arotewala
Vinrlidttx eblorldo
A
0.2 (1974)
2-3
Oatd for poiy«ar tpncteale
tr UtkUmtCtyUM
A
0.14 (1971)
990
70 to 60 porcoot ««od for aaial cla«t«|
TotrocMoroothylena
A
0.3] (1971)
>90
60 ptfCMC wood for dry cloeal&a ood tostllo
ptM««aiatt teatHt 13 ^at«ati «m4 tot mil
(Ua«lnt
A
1.1 (1970)
>so
30 p«rc«M wood in Mlwat oppllcdtlona.
faeaiiHtat la the pradvtlioo of ottroN«m»,
DOT* (ipteoyl ocld*
^tcHteroMMiAt
A
0.Q4 (19741
»owt 23 percent •( prod« I c h 1 o r 06 e ft * o a*
A
0.0) (1974)
>90
90 p«rc«.it of production wood (or »>*<• d«o*
dorlims mod oo.n awirci
1,2.4 Tr lchloroW
-------
TAflLE 3. ir>*)SPKMIC CUSCOTTHAT VMS uf ffASU&CO OOMICALS TO fKIUOELTHU AtZO STftTtB 1SURD
K)
Cnraical Croup and Speclea
Philadelphia
-22 April 198)
5til.cn Island
25 April - 1 Ray 198]
PPT*
PPT»
Mean*
3 0."
Railnuo
fflnlctfl
n/ar
Mean
S.O.
Kaslnua
Klnlsvas
n/B
CHLOROrLlWOORBCHS i
Trlchlorofluorocethane (P-11)
369
132
1667
?ll
88/88
28*
110
61«
•37
33/3)
Dlchlorodlfluorooethane (P-12)
595
279
2*7*
)«0
83/88
566
269
1550
296
J2/32
Trlchlorotrlfljoro*thane (P-ll))
• -
--
--
--
--
Olchlorototrariuoroethane (F-ll*)
«l
83
616
10
76/76
2*
13
eo
10
)1/)1
halohcthabesi
rtethyl chloride
769
299
288)
}»a
91/91
65*
280
1}6T
J28
33/33
Hrtnyl broolde
*7
30
12*
23
)»/)«
80
96
a«7
25
23/2)
tv-inyi Indldv
J
I
9
O.fl
8/8
5
2
9
3
21/21
Methylene chloride (Dlchloroeethane)
6;?
559
3098
121
91/91
1109
161*
0868
2*3
3*/3*
Chioroforo (Trlchlorooethane)
60
19
272
12
1*6/1*6
68
53
279
27
5»/5*
Car&cn tetrachloride
280
220
2015
126
171/171
J87
310
1*75
131
66/66
HALOCTHANES ANO HALOPROPANCSl
Ethyl chloride
66
125
555
<10
19/19
*7
28
107
21
11/11
1,2-Dlchloroethane
--
--
--
--
--
--
--
«
--
—
1,2-DH>ro»oethane
2)
«9
* J6
<5
1**/l*7
19
8
At
8
50/>8
1, 1.1-Trlchloroethane
*91
25
2679
16*
172/172
*03
257
11J5
120
66/66
1.>-01chloropropunc
72
91
560
18
1*0/1*0
«t
17
60
<10
5«/5*
CHIOROALKENE5:
Trlcnloroethylene
1*9
I7J
100}
12
166/166
16*
188
1021
12
6J/6)
Totracnloroetnylens
570
529
«)J7
76
28*/28*
792
901
#793
127
1I7/H7
AROMATIC HIDROCARQOnSi
Benxono
*91T
1721
1107*
269
293/293
*367
6620
JJ960
117
99/99
Toluene
•260
*111
30576
JfU
287/297
7**6
93*0
•0572
*62
100/100
Ethyl Ss->iene
T60
778
7256
85
26*/297
2678
*186
166*8
<50
76/109
a/p-Xylene
1598
1*89
1*050
19*
28J/29T
2635
3286
I95W
0>1
83/100
o-Xylene
8*7
6*7
5852
<50
232/297
2596
35*9
IT353
<50
56/100
)/l-Ethyl toluene
71*
6)6
3891
<50
192/297
1603
1597
66««
<50
*6/100
1,3.5-Trlnethyl beniene
526
m
1)7*
<50
31/297
1565
181*
7226
<50
2«/l00
l,2,'-Trlnethyl benzene
9*1
757
536)
<50
222/297
2858
*8*1
25636
<50
5*/!00
OXTGENJTED SPECIESi
Peroiyacetylnltrate (PAN)
1063
678
JM1
<50
281/309
1578
mi
5*75
386
116/116
Peroiyproplonylnltrate (PPK)
139
91
501
<50
280/309
213
150
902
<50
116/118
Forealdehydo
—
--
--
--
--
--
--
—
--
--
Acetaldenj-de
••
--
--
--
*Arlitootlc Mean,
**0ne standard deviation.
«> i» in® nu«b*r of posit I ** (i>nn-MPo) MA3ur*««ntni
.1 la the toui nuaber of Mild oenairtMnta.
-------
TABLE 9. ATMOSPHERIC CUtJCEMTRATtOflS Of HEASURhD CHEMICALS FUR DOWHET. HUUSTUH, AND DOVER
Cnenlcal Croup and Species
Downejr
18-27 Felfuary 1984
Houston
9-17 Karcfl I9S4
PPTV
PPTV
Mean*
S.O."
Kailoin
Minima
n/Kf
Mean
S.O.
ttaXoto
ftinlQua
n/u
CHLORPFLUOROCA RBONS i
Trlcnlorofluoroeethane (F-ll)
68$
356
1718
168
45/47
488
142
1041
251
48/48
Dlcilorodlfluorooethane (F-12)
118)
779
3601
314
48/48
512
156
941
332
48/48
Trlcnlorotrlfluoroelhane (F-113)
118
53
313
68
47/47
58
16
114
36
4a/48
DlcnlorotetraHuoroethane (F-11*)
3«
20
89
12
47-S?
IS
3
30
12
47/47
KAIOHE THAMES:
Methyl chloride
79C
237
1655
470
48/48
961
361
2278
520
47/47
Metn/1 tronlde
225
815
18
44/44
23
8
48
11
45/45
Hethyl Iodide
3
2
¦ 0
6
CMorofora (Trlchlorcoetltane)
135
8i
385
26
64/64
249
2«3
1588
47
110/110
Carton tetrachloride
199
71
331
103
48/48
291
175
1154
158
48/48
HAlOETHmS AND HALOPROPAHESi
Ethyl chloride
23
17
106
11
43/43
448
871
2981
II
40/44
1 ,2-DlcMoroethane
102
13'
630
20
45/45
«50
673
2456
<5
47/48
1,2-DlBroooethane
102
83
<20
<5
52/61
293
550
3181
<5
104/106
• ¦ •. l-Trlchloroothane
1161
609
2727
161
64/64
375
208
1*35
121
110/110
1,2-Dlehloropropane
35
3«
157
<2
4 J/64
158
108
724
<2
100/106
CHlOROALKENESi
Trlcnloroethylene
189
155
738
?2
64/64
61
106
880
<2
104/110
TetrachloroeUiylene
1471
69*
3711
3«1
64/64
169
245
1604
:o
109/109
AROMATIC HTDROCARBOKSl
Benzene
8720
5940
28790
970
107/107
6130
5838
40320
1030
102/102
Toluene
16890
12251
63970
1640
106/104
7270
9479
78160
270
100/102
Ethyl bemeno
1580
3712
16090
280
104/104
1540
1589
8200
<50
99/102
o/p-Xjrlene
10210
7785
37*80
920
104/104
3340
3066
17910
<50
101/102
o-Xjlene
#180
3?I9
15960
<50
10)')03
1330
1339
7200 ,
<50
89/102
3/4-Ethyl toluene
i?20
2512
12270
<50
102/103
770
890
5920
<50
84/102
1,3.5-Trls»thyl benzene
850
923
4040
<50
63/104
170
714
6760
<50
20/102
1,2.4-Trloethyl benzene
4020
332*
15590
<50
100/104
990
1005
7180
<50
76/102
OXYGENATED SPECIESi
Peroiyacetgrlnltrate (PAN)
1*31
1112
6671
67
207/207
751
787
7925
<50
188/193
Peroiyproplonylnltrate (PPN)
60
67
403
<50
145/206
45
78
538
<50
89/'89
FornaIdehyde
15500
5900
41000
2000
48/48
3800
8300
22500
<400
11/11
Acetaldehyde
8500
6JOO
28400
1000
48/48
2200
1700
6700
.... .
<200
--
11/11
-------
TABLE 9 (contlrued).
K)
as
Chenlcal Grouo and Species
Denver
2* March - 1 April 198*
PPTV
Moan*
S.D."
Hailoun
Mlnloua
n/Ht
CKL0R0FLU0RQCAR8GNS i
Trlchlorofluoroeethane (F-ll)
555
89
770
#12
*2/*2
Dlchlorodiriuoruaettune (F-12)
648
5»6
2811
33*
*2/«2
Trlcnlorotrlfluoroethane (F-113)
*1
*1
282
22
*2/*2
Dtchlorotetrariuoroethane (P-IH)
26
8
6*
17
«l/«1
HALOMETHANES t
Methyl chloride
780
227
1602
573
*1 /* 1
Methyl broelde
22
11
60
13
*l/*l
Methyl Iodide
2
1
8
1
*2/*2
Methylene chloride (Dlchloroaethana)
569
*56
2699
10*
*2/*2
CnloroToro (Trlcniorooethane)
123
*0
259
38
98/98
Carbon tetrachloride
26*
26
363
225
*2/«2
HALOETHA.1CS A.1D HALOPROPAXESl
Ethyl chloride
23
21
123
9
*l/*l
1,2-Dlchloroethano
23
29
12*
<5
31/3«
1,2-01 woooe than*
122
8*
601
<5
98/99
1,1,1 -Trlchlc-oethane
6*7
320
1850
?56
98/98
1.2 - 01 ch 1 oropropar.t
163
62
312
<2
96/97
CHlOROALKEMESi
Trlcnloroethylene
53
*9
2*1
5
99/99
Tetraehloroothylene
»)<
*19
2*99
51
99/99
AROMATIC HIDflOCARBONSi
Bonzene
22} 0
2081
13*80
380
85/85
Toluene
33*0
3971
25780
390
85/85
Ethyl benzene
1100
3*5*
31*80
<50
70/85
i'p-Xyl*>*.*
1900
2322
1*770
<50
82/85
c-Kylers
63u
j: *2
*630
<50
50/85
3/*-Ethyl toluene
**0
707
*220
<50
*0/85
1.3.5-Trloethyl benzene
80
221
1300
<50
1 */85
1,2,*-TrlseUiyl benzene
650
972
5650
<50
53/85
OirCEHATEt- SPEClESi
Peroiyacetylnltrate (PAH)
614
3*8
2C39
191
209/209
Peroiyproplonylnltrate (PPN)
22
29
85
<50
82/209
Foruldehyde
2300
1S00
5500
<*00
21/21
Acetildehyde
iooo
500
2100
<200
21/21
*Arltrus«tlc Hean.
• t
One standard I at Ion.
'n la th- mjabcr of poalttw (non-iero) BO&aureaenlaj
v Is the total Rvttto' of valid ¦easircsonta.
-------
TABLE 10. ATHUSPHEKIC CONCOTftATIOXS OF MEASURED CHEMICALS fUH 54* JJSl
Chemical Croup and Species
4-16 April
1935
l?-24 ftufloat T9S*
PPTV
PPTV
Mean*
S.D."
Hailnja
Minimum
n/Nt
Hoon
S.D.
toalBua
ttlMeua
-..'I
CttLOROFlUOKOCASBOHS i
TrlcH'orofluoronetJiane (F-ll)
529
217
161J
252
119/119
•50
IT9
•330
244
127/127
DIcMorodlfluoroBelhane (F-12)
1020
'77
2751
458
117/117
881
345
2058
427
129/129
Trlcnio-otririooroelhine tF-llJ)
1256
755
*605
395
117/1tj
616
407
24)0
166
(26/l2«
Dlrfilorotetrariuororllane (F-II4)
59
39
239
19
t15/115
72
143
ws
12
•23/123
HALOtfCTHANES:
Methyl chloride
1060
274
2506
67]
116/116
--
—
..
..
Me tn ir 1 ftroolde
too
5«9
4661
44
MO/MI
121
146
1067
<5
117/114
Hethyl iodide
5
6
51
1
104/104
J
2
<10
t
123/128
Methylene chloride (Dlchlorooethano)
1530
906
*311
40J
M7/117
1119
1056
8257
142
128/128
Chboroforo (TrlcMoroaethane)
6*
27
138
*3
119/119
58
35
ISO
11
139/139
Carbon tetrachloride
193
51
39a
55
119/119
144
20
*»3
85
M2/I42
IIALOETHANSS AND HALOPROPANES:
Ethyl chlorlda
--
—
--
—
—
—
--
—
--
—
J ,2-Olrhloroethane
—
--
—
—
—
—
—
--
—
--
1,2-Dlbrcaoethane
21
7
41
9
40/40
—
—
--
—
«
1,1. 1-Trlchlocoethane
360
114
90S
120
118/1(3
283
68
518
133
• 42/142
112-Di cli J oropropand
31
1*
70
9
87/87
25
9
.1
9
136/136
CHLOROALKEK£Sl
Trlcnloroethylene
63
<9
266
a
• •J/113
68
54
266
10
141/141
TetracMcoethylene
427
259
1530
58
115/115
264
169
767
36
139/1 39
AROMATIC HIMOCARBMSi
Uentene
3296
2239
11747
379
Wi/123
2C60
1258
7816
441
145/145
Tolirane
5667
4206
22155
637
¦>2/122
3904
2J«2
19612
709
145/145
Ethyl benzene
UI3
1108
6355
tjl
<22/122
859
736
0089
•73
144/144
d/r-lylene
3619
2701
14641
649
*22/122
1981
l»3l
83SO
5»5
140/140
o-Xylane
1361
950
5085
121
119/119
913
659
5125
216
141/141
3/3-Ethyl toluene
102)
756
10SS
12S
•25/120
649
«33
2927
107
142/142
I,3.5-Trlnethyl bcmene
220
203
1609
69
121/121
16B
124
T73
3'
141/141
1,2,4-Trlaetnyl bemene
1272
832
051®
*3J
116/116
715
521
3591
112
135/135
OXYGENATED SPECIES:
Peroiyacetylnltrste (PAN)
—
—
—
«
—
«
—
—
—
--
Peroiyproplonylnftrate (PPN)
--
--
—
-»
—
••
--
--
--
--
formaldehyde
—
—
--
--
--
--
--
—
--
Icttaldehyde
" *
*¦*
"* *
"" ""
"
mm
-------
TAHLE 10. (CONTINUED)
N)
CD
Cricnlcal Croup «na Species
lj-21 December 1985
PPTV
Mean'
S.D."
HaxlDLQ
1 HlnlDiB
n/Nt
CHLOROFLUOROCARDONS:
Trlcniororiuorcmetlwns (F-ll)
595
170
971
239
80/60
Dlcllorodlfluorooiethane (F-12)
1 "35
376
2'50
670
91/91
TrlcnlorotrtfUioroelhane {F-llJ)
1211
J5t
2321
476
92/92
Olchlorotetrafluoroelhane (F-1U)
227
2<"5
967
3»
9«/9(
HULOMETWUHESt
Methyl chloride
IMS
581
«fl70
19*
Hethyl broriiJit
2869
309B
15»2»
239
92/92
Methyl Iodide
9
ft
2J
3
80/80
Methylene cnlortde (Dlchlocooethane)
HI 81
1795
10)10
103*
91/91
Ciloroforo (Trlcnlorooethane)
10?
38
203
33
93/93
Carbon tetrachloride
155
«3
266
90
93/93
KALOETHANES AND HALOPROPANES;
Elhjl cniorlOe
—
—
«
--
--
1,2-Dlchloroeth3ne
--
--
-¦
--
1,J-Dltroooethane
7
]
IS
2
61/61
1,J,1-TrIch loroelt»irt«
1219
721
3W«
3*5
93/93
1. 2-D 1 ch loropropane
r»
5
35
9
85/85
CHLORO«LKENES-
Trlehloroetnylene
19*
907
T1
93>93
Tetrachloroethjrlene
1859
1202
6639
ill
93/93
AROMATIC HIOflOCARBONS:
Heniene
12372
1501
23*25
3921
95/95
Toluene
21155
8801
'59*7
66T6
95/95
Ethyl bentene
6176
30«6
m53
155}
95/95
o/p-Tylene
>jm
5809
25330
3672
95/95
o-Xylen»
57l«
2IT0
11001
2024
95/95
3/<-Ethyl toluene
«22«
I57S
8285
1
-------
bars. Jn San Jose, 2-hour integrated samples were collected. The diurnal
patterns for San Jose were calculated identically to the other cities, except
that 2-hour intervals (midnight to 2 a.m., 2 a.m. to 1 a.m., etc.) were used.
Because many of the chemicals measured here are also ubiquitous compo-
nents of the glc-bal troposphere, Table 11 ha3 been prepared to define this
background at midlatitudes in the Northern Hemisphere. The concentrations are
estimated tor the year 1985 and are derived from published values and our
measurements at Point Arena, California (Singh et al, 1983b-e, 1986; Prlnn et
al, 1983; Simmond et al, 1983; Singh, 198").
Interpretation of field data is greatly facilitated wher, some knowledge
of the chemical loss rate exists. In a given day, the diurnal behavior of
chemicals is controlled both by the ml King process a3 well as chemical loss.
It is well known that the hydroxyl radical (HO) plays a central role in
depleting atmospheric organlcs, both In the polluted and the clean atmos
pheres. For the halogenated (except methyl iodide) and aromatic hydrocarbons
of interest here, we have concluded that no significant error in less rates is
Incurred when reactions with species other than HO, such as 0(^P), 0^, HO2,
are neglected. In the case of the aldehydes and of methyl iodide, both
reaction with HO and photolysis are important.
The residence times of PAN and PPN are largely controlled by their ther-
mal decomposition, and are estimated from mechanisms suggested by Hendry and
Kenley (1979). For the purposes of these calculations, an average daytime HO
radical abundance of 2 x 10^ molecule/cm^ is assumed. These HO levels are
well supported by HO estimates from available field data (Calvert, 1976; Singh
et al, 198la; Roberta et al, 1981), and are probably typical of tne boundary
layer of polluted urban environments In summer month3. The only wintertime
estimate available is from Southern California (Singh et al, 1985b) and sug-
gests, at least at this site, that OH levels are comparable to their summer
values. The kinetic and photolytlc data utilized in Table 1? are taken from
Atkinson et al (1979), Hampson (1980), Hudson and Reed (1980), and estimated
from Hendry and Kenley (1979), and Hendry et al (19B0).
Table 12 provides these data, and estimates the percentage loss due to
chemical reaction In one day U2 sunlit hours). For virtually all species of
29
-------
TABLE 11. ESTIMATED AVERAGE BACKGROUND CONCENTRATION
OF TRACE SPECIES AT *40°N FOR YEAR 1985
Chemical Group and Specie3
Concentration
(ppt)
CHLOROFLUOROCARBONS:
Trichiorofluoromethane (F-11)
2140
Dichlorodifluoroinethane (F-12)
300
Trichlorotrifluoroethane (F-113)
35
Dichlorotetrafluoroethane (F-111))
16
HALOMETHANES:
Methyl chloride
650
Methyl bromide
15-30
Methyl iodide
2
Methylene chloride (Dichloromethane)
50
Chloroform (Trichloromethane)
20
Carbon tetrachloride
1W
HALOETHANES AND HALOPROPANES:
Ethyl chloride
10
1,1 Dichloroethane
-*
1,2-Dichloroethane
no
1,2-Dibromoethane
, 2
1 ,1,1-Trichloroethane
200
1,2-Dichloropropane
-
CHLOROALiCENES:
Trichlo-oethylene
15
Tetrachloroethylene
50
AROMATIC HYDROCARBONS:
Benzene
230
Toluene
¦>30
Ethyl benzene
-
m/p-Xylene
30
o-Xylene
10
3/^-Ethyl toluene
-
1,3,5-Trimethyl benzene
-
1,2,^-Trimethyl benzene
-
| OXYGENATED SPECIES:
Peroxyacetylnitrate (PAN)
50
Peroxyproplonylnitrate (PPN)
3
Formaldehyde
too
Acetaldehyde
200
ft
Daahes indicate absence of available data.
30
-------
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5
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Table 15, nighttime loss ratc3 are negligibly small. This percentage loss la
defined as?
percent I033 - [1 - exp (-4.32 x lO^K)] x 100,
vhcra K - fe^KO) ~ khv ~ kthenMl.
It Id clear froa Table 12 that dally cheaical less rates ranging froa
neor-aoro to 100 percent per day, consistently occur in tho atmosphere.
Chlorcwetlwses and chloroethanes, collectively a dominant group, ore rela-
tively xmreactive, and a daily loss rate of 0 to 3 percent per day Is -
stanr.lally reduce Its loss rate (Hendry and Ketiley, 1977; Cox and Rof'ey,
1977).
INTERPRETATION OF FIELD DATA 9Y CHEMICAL CATEGORY
Cnloronuorcva"'x>n3 (CFCs)
Four fluorocarbona {Fluorocarbons 11, 12, HI, and 111) were routirely
censured, These chcnicala are not considered or expected to be toxic but can
t* useful indicators of urban air masses. Their involvement in atratosphtrlc
oione titavructlon is w«Vl known (Molina and ftovland, 197^>. It is clear 1-oa
Tables 3-10 tht F12 ia the most dominant species, both in urban and reajte
Atsosprteres. The f1C/Fl1 ratio in urban centers varied from 1.1 to »nd
had a nwan value of 1.7. This coopareJ favorably with a ratio of 1.6 found in
the fro© troposphere (Table 11). It i3 noted that background concentrations
of those fiuurocarbons nave*1 been increasing at a rate of 5 to 7 percent i«r
year !oin^r\ ol ai., 19 630). F113 is a conroonly u3ed solvent In
-------
San Jose field studies was far In excess of what Is encountered in other
locations. Figure 8 shows the mean diurnal behavior of F113 as mea3ired at
the San Jose site during April, August, and December of 1985 (see section 5
for the exact computational procedure used to obtaining these dita-nal
profiles). Indeed the abundance of F113 was comparable to that of F12 in San
Jose during all seasons, while it was nearly an order of tsagnltude lower at
virtually all other sites Including the remote troposphere. A maximum mixing
ratio for FT 13 of 4.6 ppb was oaasurod at San Jose (Table 10) coaparod to e
maximum F12 value of 3*6 ppb measured at the Doynay Site (Table 8) in Southern
California. Very little urban data on the distribution of fluorocarbon9 are
available. Comparison of averifle concentrations with those earlier reported
by Singh et al (1983e) and Brodzlnsky and Singh (1983) suggest that the
relative abundance is showing a pattern, with Ft 13 exhibiting the most
relative change in its abundance. Typical average concentrations at these
site are 1.5 to 5 times the global background concentiations (Table 11). In
the case of F113, however, this ratio was as high as 35 in San Jo3e (Table
10). Figures 9 and 10 show the diurnal behavior of fluorocarbon 12 and 114 at
selected sites and in different seasons. The highest F12 values In San Jose
were encountered during the winter experiment [Figure 10(c)3» a period of high
stagnation.
Haloreethanes
Six halomethanes—methyl chloride, methyl bromide, methyl Iodide,
methylene chloride, chloroform, and carbon tetrachloride—were aeasired. All
six of these are bacterial mutagens or suspected carcinogens (Singh et al,
1982; Helmes, et al, 1983). Three methyl halides have dominant natural
(oceanic) sources (Lovelouk, 1975: Singh et al, 1983b,c; Singh, 193U),
Methyl Chloride--
The dominant natural halocarbon in the atmosphere is methyl chloride. A
nearly uniform background concentration of 0.6 to 0.7 ppb has teen measured
around the globe (Table 11), and no temporal trend In its background
concentration is evident (Singh et al, 1979b; 1983c). Urban levels of methyl
chloride have not been frequently reported in the literature, although Watson
33
-------
s
ices
cco
b) ATOIl 1*63
M i
I M
i
i
r» 10
IC90
caoo
I
•- I MO
111
•1
(k) AUQUST IMS
1111 i n 11
ui oscntssR ie»
Ill'l
• II
TIME OP DAY
Figure 8 Diurnal behavior of fiuoroc&rbon-113 ej tho San Jose *ite during
April, August and December, 1985.
34
-------
WOU
acvoo
8M>0
ttoort
laaa
1000
MHJ
e
CO
AO
TO
«0
60
40
30
ao
»&
0
Pi^jt« 9. Diutnol behavior of fiuorocarbonj 12 and 114 at Downoy. CA ute.
i 1" v '
111 huomstoA 1}
I
is
Tints of D#y
— , 1
fe} tfet&os&fesa III -j-
I I
IB
31
ill1:
I '
12
Tlmo of Day
ta
2'
35>
-------
*SM>
i
I
I 1090
M
taoo
aooo
to) April 1 GS&
.. i i1111
I
l
i
M
1099
89M
(b) Aueun 1B8S
111111 i i
¦I
r
(t) DKwnbtr 1ES0
Hill
Time of Dty
Figure 10. Diurnal behavior of fluorocarbon 12 at San Jose site
during April, August, and December 1985.
36
-------
et al, (1979) did report methyl chloride levels of over 2 ppb In Kenya. Based
on our measurements (Tables 8 through 10), It appears that although typical
methyl chloride levels In urban areas are close to, or only slightly elevated
abovo, background levels, concentrations about five times higher than the
background nay be encountered. The average mothyl chloride levels of 0.60 to
1.1 ppb measured here are only slightly olovated above the geochemical
background. The direct man-made sources of methyl chloride are negligibly
small coapared to the oceanic source of nearly 3 Tg/year. Nevertheless
anthropogenic sources, possibly related to combustion activity, are clearly
present in urban centers. Figure 11 shows the concentrations of methyl
chloride and Its mean diurnal behavior at the Denver and Houston sites. In
both instances there is evidence of anthropogenic Influences, but the effect
Is much larger in Houston compared to Denver. Methyl chloride Is slowly
decomposed In the atmosphere (dally loss rate <0.5 percent), and Its global
residence time is estimated to be between 1 and 2 years (Singh et al, 1983c;
Table 10).
Methyl Bromide—
Average methyl bromide concentrations of 0.02 to 0.3 ppb were measured
during the first five studies. In San Jose, moan concentrations of 0.4 ppb,
0.1 ppb, and 2.9 ppb were measured in April, August, and December, respec-
tively. A maximum concentration of 15.4 ppb wa3 also measured during the
winter experiment. These very high values 3re contrary to our previous mea-
surements at other sites. The possibility that this site Is impacted by
unknown loial sources of methyl bromide cannot be ruled out. A background
concentration of 15-20 ppt is known to be present, with oceans as the major
source. Methyl bromide is used as an agricultural fumlgant and its concentra-
tions In urban areas are clearly elevated. It has been suggested that the
gasoline Additive 1,2-dibroaomethane could breakdown to produce methyl bromide
CMS, J378), This additive Is normally used in leaded gasoline and may be a
source in urban areas. Although measurements of methyl bromide in the marine
atmospheres are extensive (Singh et al, 1983c; Singh et al, 1984; Berg et al,
1981; Pcnkett et al, 1935) virtually no data ore available from urban loca-
tions. The present measurements (except at San Jose) are similar to our
37
-------
u>
00
CHjO vtTIME AT
HOUSTON. TEXAS
i.
i
i
1000 -
>4
¦» t
• * 4 64*0
4 * 0 -
600
I . I .1.1.1.1.1.1.
—i—1—i—'—i—¦—i—1—i—¦—i—1—i—'—r
CHjO n TIKE AT OEMVEft. COLORADO
- A
* *
I
%
A
M u < Aa4 a
oft '
A . .»
I ¦ I ¦ I ¦ I ' I . t
2400
1340
&
9.
5
TOXIC DATA FOR UABCS IBS*
Tone data na fcaa-AKsi. icm
DIURNAL VARIATION OF CHtCI AT HOUSTON, TEXAS
diurnal variation of cmjci at oscroaR. Colorado
I1!!
I
Tl«0 of 009
600 ~
19
Tle»« o# Dej
:tsure 11. taetnyl cnlortde distribution end diurnal behsvior at the Houston end Oonvsr sites.
-------
earlier ones where we reported typical methyl bromide concentrations of less
than 0.1 ppb with highest values in the 1 ppb range (Singh et al, 1982;
1983e). At Staten Island, mean concentrations of 81 ppt and 80 ppt were
measured In 1981 (Singh et al, 1983e) and 1983 (Table 8) respectively. In
both Houston and Denver, the measured concentrations wero nearly fourfold
lower compared to the previously measured spring/8urasar values. This Is
primarily due to the unstable weather conditions that prevailed dicing these
experiments. The San Jose concentrations are among the highest issasired to
date. It is evident that significant methyl bromide sources in urban areas
exist. Their nature and strength, however, is not known. Figure 12 shows the
variability of methyl bromide and its diurnal behavior at the Downey, CA
site. Methyl bromide is chemically removed from the atmosphere at a rate
similar to that of methyl chloride (Table 12). There is some speculation
that methyl bromide levels may increase over the years, causing it to be a
major depletor of stratospheric ozone (Per.:
-------
600
7O0
600
500
400
300
ZOO
too
o
IB CO 21 22 23 24 29 24 27 28
TOXIC DATA TOR FEBRUARY 1664
OOO
BOO
TOO
eoo
ftoo
400
300
200
100
O
Figure 12. Methyl bromide distribution and its diurnal behavior at Downey, CA
site.
t>
1
-------
while th<5 winter San Jose experiment was performed under stagnant conditions.
The possibility of localized sources or unknown interferences cannot be ruled
out. Tho global budgets of methyl halides have been reviewed by Singh (193^).
Figure 13 shows the diurnal behavior of methyl iodide at the Downey site.
Methylene- Chloride—
Methylene chloride is a large volume chemical (Table 7) of anthropogenic
origin and is a commonly used solvent. To the best of our knowledge, no
natural sources are known to exist. World-wide man-made emissions are estima-
ted to be O.H Tg/yr. The global distribution of methylene chloride in the
background atmosphere shows Northern Hemispheric (NH) concentrations to be
about twice the Southern Hemispheric (SH) values (Singh
-------
B -
0
i
t
o 1 1 1 I L
0 « 12 18
Time of Day
Fi{pre1l Diumal behavior of methyl iodide at Downey, CA site.
42
-------
g
I
I
£
I £39
1000
600
0
4Mb
(•) April 1985
Hi!
i
J
I MO
IOCO
too
lb) A upset 1835 -
i
If
D
f
(c) December 1636
II
• ie
Time of Day
Figure 14. Diurnal behavior of methylene chloride at San Jose site
during April, August, and December 1985.
43
-------
2500
2000
£ <500
a.
i
l
IN
o
g* 1000
500
"I
I
'
I
i ¦
It) Philadelphia
—
- ~
_
•
>
¦
i
>
~
i
<
.
~
*
~
'
-
1
1
1
1
—• ~
16
Time of Day
7000
eooo
ftOOO
a.
4000
u
CM 3O0O
zooo
1000
24
1
1
l
1
—i
1
1
(b) Downey
-
-
• <
1
—
—
_
_
—
1
1
1
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- I
1
1
-
1
1 .
1
' 1
1
-
-
1
1
1
1
'
-
12
Time of Dt;
IS
24
Figure 15. Dii/rnal behavior of methylene chloride at Philadelphia and Downey (CA)
sites.
44
-------
Chloroform—
Chloroform, a mutagt>i\ ami a suspect ca'Vln^en (Nelxca, *1, h*?
received a great deal of Auction In recent y\?ars because of U*
tr&tions in drinking waie^ (S^swns et al, Its NH baeVKrvv^vS
tion 1 s in the 20 to 30 p£t range with a NH/SN gradient of 1 .§ IS £. VUSv
production rate ha3 re«al«£\l etore or leas coolant at 0.15 to 0.5 Tj^r *Uh
nearly 90 percent of the {StN^uctlon going towards tho taanufae*,vr$ Of ?i.*£XNv
cairbon 22. It is estinat^S that world-wltte emissions aro eboyt 0,02
(Singh, 198ft) while the atassspherlc reservoir squires a source Q.S
Clearly then, a majority e>f chloroform su\nvea are not Industrial «nd
probably ill defined (BatJ^ et al, 1980). There is tentatlw evidence
oceans nay be the largest »uv£le source of eJUorofortn (Singh, WS*)* Tafr-iw 4
through 10 show that In K*k^h areas cnloroJVre concentrations wll aN>v*
its geochemical background Average concentrations in the of O.CV^
0.:'5 ppb and maximum conc*4\trations in the range of 0.2 to 1 *****
sured. In our previous staves, we have encountered coss.centratl. The reactivity of chloroform la (sv&ivcal-JU VOs
methylene chloride, and its dlurraJ behavUv Is principally' «\vntrs>.HS fcy
meteorological processes. again, the urK#n as well as ths sow««»
of chloroform ere not well vteflned. Figure shows the dlur«« «jhAvi fsswney (Figure Vf) aro higher than San Jw#
when the latter encount^sM highly stagnant sacteorologlcal ^N">4lti\5f\3i
December.
Carbon Tetrachloride—
Carbon tetrachloride, a suj*^ct carcioo^n, Is nearly uniformly 21^101"
buted in the global atmosjW^ at a sirable Nic-Vsro and concentration cf aN'Wt
1U0 ppt (Helmes et al, Singh, 1981). Although larg« naiv^al st^vuv<>s
carbon tetrachloride have Jwn speculated, jnv\c haw been foi»v1. Anal*-*
sis of available data et al, 1976; Altshuller et al, WTM cs
et al, 1933) would suggest that It Is pr In.* i pal ly a man-ra»d«*
ave-a?e Reocherr.lcal bacV«;is\L.r\.l cvn cent rat lev* cf O.^tt ppb oi>n Ns *¦,
an average concentration 0.1 * to O.ft ppb »*9ureCS during th*vn«? stuJlr-j
45
-------
I
\
i
i
I
«9
to
e
i«o
IM
1*4
tn
IM
C*
U) Apr.t IBS*
mil:
(b) Auqum 1833
I
lilllt
(c) Docomtw 1985
§
I 0
IM
1 IM -
f :_i 1
Tof Osy
Figure 16. Diurnal behavior of chloroform at San Jote site during
April, Ausutt, and December 1985.
Ub
-------
«uu
1
1
-
¦ 1 "
300
—
—
300
~
230
—
—
800
* "
<
1
-
<
>
.
l&O
<
~
<
~ ~1
<
~
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<
~
.
IOO
— _
T
.
<
f
ao
—
_L
—
0
.
I
I
•
Time of Day
Figure 17. Diurnal behavior of chloroform et thg Downey site.
47
-------
(Tables 8 through 10). Sporadic concentrations as high as J ppb wore also
encountered (Table 8). A maximum concentration of 1.2 ppb measured at the
Houston Site In March 199U can be compared to a maximum 3 ppb concentration
measured In May 1930 at this same site (Singh et al, 1983q). Figure 18 shows
the diurnal behavior of carbon tetrachloride as moaaurod at the Downoy an! San
Joais (winter) sites,
Haloethanes and Haloprcpanes
Five Important chonlcals in this category wore ooaswrod. Four of thsso
(Including ethyl chloride) are either bacterial tsutagens or suspect carcino-
gens (Helmes et al, 19?3• Singh et al, 1932).
Etnyl Chloride—
Ethyl chloride is a commonly used chealcal Intermedlato (Tablo 7). It is
estimated that about 0.01 million tons or ethyl chlorldo aro roleased into tho
atmosphere every year in the United States. A dally chemical loss rate of
about 3 percent la G3tloated (Table 12). Avorape ethyl chlorldo concentra-
tions at all sites were In the 0.02 to 0.07 ppb range, oxccpt at the Houston
site where they wore significantly higher. Tho avorago concentration «t
Houston (Table 9) was 0.45 ppb and a maxlo-.ua concentration of 3.0 ppb was also
encountered here. This Is consistent witn our previous measurements (Singh ot
al, 19&3e) at this site where average and maximum l«vcla of 0.2j ppb and 1.3
ppb, respectively, were measured. The average or all urban data are reported
to be less than 0.1 ppb by Brodzlnky and Slngn, (I98j). Background concentra-
tion of ethyl chlorldo (at
-------
MO
500
Ht80
1100
too
60
0
MO
300
mo
800
I BO
too
60
0
Downey
J . L
San Josa
oeccesaan >ess
' 1 .
® to
Time o1 0#v
Figure 18. Diurnal behavior of carbon tetrschloride ot Downey and
San Jote sites.
49
-------
*40 ppt at 10°N (Table 11). It is obvious from Tables 8 through 10 that urban
levels are significantly elevated.
The chemical was most abundant at the Houston site where average and
maximum concentrations of 0.45 ppb and 2.5 ppb, respectively, were measured.
This 0. *»5 ppb concentration measured in March is significantly lower than the
1.5 ppb average concentration at this site in May i960 (Singh et al 1983c).
In Douney, CA the average concentration was only 0.1 ppb (aaxlraua 0.6 ppb).
This 13 also ouch lower than the 0.5 ppb average measia-ed In Los Angeles in
April 1979. Inquiries at the California Air Resources Board confirmed that
several major emitters of 1,2-dichloroethane had closed down during this
time. Brodzinsky and Singh (1983) report an average concentration ol 0.37 ppb
based on available data from cities in the United States. Figure 19 shows the
mean diurnal behavior of 1,2-dlchloroethane at the Downey, CA site.
Ethylene Dlbromlde—
1,2-dibroooethane (also commonly known as ethylene dlbromlde) is a sus-
pected carcinogen (Helmes et al, 1983; Singh et al, 1982). The estlcated risk
associated with exposure to 1,2-dlbromoethane Is nearly 50 times the risk from
1,2-dichloroethane for equal exposure (Albert, 1980). About 0.1 million tons
of thl3 chemical .ire manufactured In the United States every year (Table 7).
It is primarily u:ted as a gasoline additive and a fumigant. Its atmospheric
reactivity Is comparable to that of 1,2-dichloroethane (Table T2). Controls
have been placed on the use of this chemical in many areas, and It is not an
additive used in unleaded gasoline. Its future market, therefore, can be
expected to decline. Its average concentration was the highest at the Houston
site (0.3 ppb), lr part because the site is located close to Interstate
Highway 10. Average concentrations were about 0.1 ppb at the Downey and
Denver sites, and less than 0.02 ppb at all other locations. Maximum measured
concentrations ranj^S from 0.02 ppb to 3.2 ppb (Tables 8 through 10). If one
excludes the Houston site, the maximum concentration is a significantly lower
number of 0.6 ppb. These measurements are comparable to the 0.06 ppb average
of all urban data reported by Brodzinsky and Singh (1983). Figure 20 shows
the measured diirnal distribution of 1,2-dibromoethane at the Downey and
Denver sites.
50
-------
o.
a.
600
600
400
u
n
5 300
G
M
5
eoo
100
, —
1 1 '
«
•m
•
<
~
—
<
t
—
J
Y
<
nr ""
T 1
1
, i i,i i•
-- 1 1
1
i.i.
12
Time of Day
18
84
Figure 19. Di rnal behavior of ethylene dichloride at Downey, CA
51
-------
400
360
300
250
(*) Oewnav
& 800
S* 160
100
fiO
400
350
l -
12
Tim# of Day
i 1
ia
(bl Denver
24
300
260
200
i
I
l
A
a
160
too
60
I. " T II
I 1 1 I
12
Time of Day
IB
.J
ZA
Figure 20. Diurnal behavior of ethylene dibromide at Downey (CA) and
Denver sites.
52
-------
1,1,1-Trichloroethane—
1,1,1-trichloroethane is another large-volume chemical that Is released
In significant quantities to the atmosphere (Table 7). The chemical has a
long atmospheric lifetime and is globally distributed (Singh et al, 1979a,b).
Its atmospheric residence time Is estimated to be about eight years (Singh,
1979b; Singh et al, 1983b, Prinn et al, 1983); thus about 15 percent of all
1,1,1-trichloroethane released at ground level enters the stratosphere, where
it can interact with ozone in a way similar to fluorocarbons. 1,1,1-
trichloroethane is suspected to be weakly mutagenic (Helmes et al, 1983),
although considerable disagreement on lt3 mutagenic and carcinogenic potential
persists (Farber, 1979; Lapo et al, 1979). The background birden of this
chemical is constantly increasing; background concentration is now reported to
be about 0.2 ppb (Table 11).
Average concentrations at all sites ranged from 0.3 to 1.2 ppb while
maximum concentrations ranged from 0.5 to 3.2 ppb. The Impact of local
meteorology 13 best demonstrated for the San Jose site. The lowest and the
highest average levels were measured at this site during August and December
experiments. Stagnant conditions during the winter experiment trapped
chemicals to cause a fourfold increase in the abundance of 1,1,1-
trlchloroethane. It is reasonable to suggest that similar meteorological
events at oth^r sites would also result in much elevated concentrations.
Brodzlnsky antl Singh (1S83) reported an average from all urban data of 0.85
ppb from measurements available prior to 1981. The present data are well
within this range and that of out* earlier measurements (Singh et el, 1983e).
1,1,1-trichloroethane acts like an inert chemical for all practical
purposes. Its urban distribution is therefore controlled primarily by its
emissions and the prevailing meteorological conditions. Figure 21 shows the
diurnal behavior of this chemical at San Jose during three different seasons.
Figure 22 shows similar behavior at the Philadelphia and Downey sites.
1,2-Di chloropropane—
1,2-dicnloropropane, a bacterial mutagen (Helmes et al, 1983) was the
only chlorinated propane measured. Its average measured concentration was in
the range of 0.02 ppb to 0.16 ppb at all sites. A concentration as high as
53
-------
g
I
I
e
(al A©ni iraS
ii11
ft «09 -
M Ausuit (889
i w
I
I
r> 400
O
u
n 300
;i1111111!!! E
ICI Dccemb?f 10SS
Time of Day
Figure 21. Diurnal behavior of 1,1,1 tnchldroethane at San Jose
site during April, August, and December 1985.
54
-------
2500
(a) Downey site
2000
toOO
rt 10OO
Time of Day
(b) Philsdaliihit iito
2000
c 1000
I
Time of Day
Figure 22. Diurnal benavior of 1,1,1 trichloroethane at Downey {CA) and
Philadelphia sites.
55
-------
0.7 ppb was also measured at Houston. In the San Jose experiments, virtually
the lowest average concentrations (0.02 to 0.03 ppb) were encountered.
Despite extreme stagnation during the San Jose winter experiment, the
abundance of 1,2-dichloropropane registered vi.ry little change, suggesting ths
virtual absence of local sources here. This extremely lw abundance Is In
accord with the data reported by Brodzinsky and Slngn (1983). He expect 1,2-
dichloropropane to be quite reactive, ana estimate that a dally loss rate of
about 10 percent occurs (Table 12).
Chloroethylenes
Two chloroethylenes were measured. These were trichloroethylene and
tetrachloroethylene, both of which are high volume solvents with annual emis-
sions of 0.15 Tg and 0.37 Tg, respectively, in the United States. Both of
these chemicals are mutagens and suspect carcinogens although disagreements on
carcinogencity still persists (Albert, 1980; Oenopoulos et al, 1980, Grcenberg
and Parker, 1979, Helmes et al, 1983).
Trichloroethylene—
Trichloroethylene wa3 measured at an average concentration of 0.05 to
0.27 ppb. Maximum concentrations were in the range of 0.25 to 1.0 ppb. The
highest average concentration of 0.27 ppb was measured In San Jose during
winter under highly stagnant meteorological conditions. Trichloroethylene has
been measured by a number of investigators, and Brodzinsky and Singh (1933)
report a concentration of 0.5 ppb based on the average of all available urban
data. It is a highly reactive chemical, and a daily loss rate of 17 percent
is estimated (Table 12). In part, because of its reactivity, a strong diurnal
profile is observed. Figure 23 shows the diurnal behavior of this chemical in
different seasons at the San Jose site. Tiie background concentration or
trichloroethylene Is 10-15 ppt, and no natural sources are known to exist.
The production of trichloroethylene has declined steadily in the last decade.
In part because its emissions are governmentally controlled due to Its par-
ticipation in smog formation.
56
-------
(a) April 1BSS
II
-------
Tetrachloroethylene—
Unlike trichloroethylene, the reactivity of tetrachloroethylene is
modest, and It is unlikely to participate in smog formation (Dimitriades et
al, 1983; Singh et al, 1983a). We estimate that less than 2 percent is
depleted daily by photochemical reactions. Average concentrations in the
range of 0.2-1.9 ppb and naximum concentrations in the range of 0.8-6.6 ppi
were measursd. The average atmospheric abundance of tetrachloroethylene was
5.6 times that of trichloroethylene although thij "atio varied from 2.8 to 8
from site to site. This ratio can be compared to a ratio of 2-1 measured
earlier by Singh et al, (1983e). The average concertration meas'jred here
(0.2-1.9 ppb) can be compared to a concentration o» 0.8 ppb reported by
Brodzinsky and Singh (1983) as an average of all available urban data. The
three San Jose experiments clearly show the effect of season and meteorology.
Tho average tetrachloroethylene concentration ay measured in December during
highly stagnant meteorological conditions was seven times that measured in the
summer. Figure 21 shows this behavior of tetrachloroethylene at San Jose.
For purposes of comparison the mean diurnal behavior of tetrachloroethylene at
the Philadelphia, Staten Island, and Downey sites is also shown in Figure
2b. It is an exclusively man-made chemical, <.-*4 no natural sources are known
to exist. The urban levels everywhere are significantly above its background
concentration of about 50 ppt.
Aromatic Hydrocarbons (AMCs)
Eignt Important aromatic hydrocarbons were sought. Benzene is a sus-
pected human carcinogen (Helmes et al, 1983; Singh et al, 1982). Carcinogeni-
city as well as mutagenicity information on toluene is disputed (Albert,
1980), although the compound has b eia classified as a potential mutagen
(U.S.S.C., 1980). In moat other cases, toxicity data are currently highly
uncertain. In addition, these hydrocarbons are photochemlcally reactive and
contribute to smog as well as to a number of intermediate products that tray be
additionally toxic. Although aromatic hydrocarbons are manufactured in large
quantities, direct releases constitute a small part of the atmospheric
emissions.
58
-------
§
<•) Aa«* «&» T
1
a
a
l
i
G
CM
O 4
(b)
T I
Lm
i
11
i
t
j.
_u
I
I
Tf
O
CcJ £>«K»i6e> Vfsfi
r i
¦*«m» ot D«v
Figure 24¦ Paj«\s5 NfNj\K>f of WtracWoro«tfc\4e*xj st\ StK» »V$s?
ttif &m«>j AjvA August. and Derotn^
*3
-------
IOOO
ttOO
K00
O00
a
i
^ 1000
MO
0
tOOO
{too
MOO
<500
COO
I
I
I
U) Phiicdrfpftta
1111 :
T
(tJ Suton liiand
i I i
Id Ocwwa»
I
Tim« o< Day
Figure 25. Diurnal behavior of tetrachloroethylene at Philadelphia,
Staten Island and Downey (CA) sites.
60
-------
The doninant ambient source appears to be automobile exhaust. Average
concentrations (Tables 3 through 10) in the range of 1.9-12.4 ppb benzene,
3.3-21.2 ppb toluene. 0.6-6.2 ppb ethyl benzene, 1.6-13.1 ppb m/p-xylene,
0.8-5.7 ppb o-xylene. O.^-^.Z ppb 3/1-ethyl toluene, 0.1-1.3 ppb 1,3,5-
trlmethyl benzene, and 0.7-5.# ppb 1,2,4-trlrofthyl benzene were measured.
Maximum concentrations at each site are typically an order of magnitude
higher. The two doninant members are toluene and benzene, with toluene naarly
. twice as abundant as benzene. Together these two species account for core
than 50 percent of the abundance of this group. Although variabilities exist
in these measurements, the average distribution of aromatic hydrocarbons in
urban air as measured frca uhc3e and our previous data, is benzene 21 percent,
toluene 36 percent, ethyl benzene 9 percent, m/p-xylene 15 percent, o-xylene 7
percent, 3/^-ethyl toluene $ percent, 1,2,1-trloothyl benzene 6 percent, and
1,3,5-trimethyl benzene 2 percent (Singh, et al, 1985b).
One of the primary means of atmospheric removal of AHCs is their reaction
with the OH radical. Removal by reaction with ozone, or due to photolysis,
can be estimated to be much less than 1 percent cf the OH removal ra«.e. The
OH reaction rates fea^ nsolee"' s~' at 298°K) have been mea3ired to b«
1.2 x 10"12 for benzene (Atkinson et al, 1979: Tully et al, 1981). The rela-
tive rate constants compared to benzene (at 29S°K) are toluene-4.8, ethyl
benzene-6.7, p-xylene-9.2, o-xylene-17.5, o-xylene-10.0, ethyl toluene-71.0,
1,2,1-trlaethyl benzene-33-O, arid 1,3,5-trimethyl bcsnzenft-52.0 (Atkinson et
al, 1979). Figure 26 show3 a clear example of the diurnal behavior of these
AHCs as observed at the Downey site. This site la chosen both for demonstra-
tion purposes, and because fair weather prevailed during the entire period of
the experiment so that normal urban activities were not interrupted. Figure
26 clearly shows dramatic diurnal variation with minimum late morning and
early afternoon concentrations.
The afternoon minimum cojld be due to a number of reasons Including (1)
chemical removal, (2) dilution due to the afternoon Increase in mixing depth,
and (3) reduced emissions. To eliminate the role of dilution. Figure 27 stows
the relative rean diurnal behavior of AHCs a3 norr-alized against benzene.
These relative afternoon mlnlmums show the faster removal of AHCs, as
61
-------
JO
28
i-
HI
5 ,6
tst
2 10
r T'
MH
I • t k
1 1
' * 1 > ¦ 1
T1—T
m*
t
1 .1
ili
* '
] i I
lX I* I »
I1
1 I '
II
o «3 it te
T1M6 OP DAV
21
\ '• r r » i "f
. j .1 1/
i 1 if • *i *¦
o -
¦ M.t
1
-
-
-
1
1
I
I,
I. •
L
6 -
o
TO -
I1
9 12 IS 10 ft M
TIMt OP DAV
Figure 26. Diumal b«h«vior of aromatic hvtirocartx>nt In southern California
(Dowrw>v
62
-------
xo
10
on
04
u
(U
ffTMVL cz*ri<*e -
CL»
O*
OJ
I J.4-TRIMrTHYL
UNtiKI
as
1 JJS-mi»CFTH>L
MNZ1NC
T1UI O# BAY
*MCAM OK CONCIHTRATIOM IN UKITt OF MOltCULfl fm~>
coMn/Tto roa tmi nmoo or mm to i»o hours.
Figure 27. Mean diurnal concentration of oromatic
hydrocarbons relative to benzene (ppb/ppb)
et Sourhern California Downey site.
63
-------
suggested V>y their greater relative reactivity towards the OH radical. It la
further possible to estimate a lower Unit of the mean OH radical concentra-
tion. This computation is possible IT one assunes that the decline in the
AHC/benzene ratio between 0600-0900 hrs and 1200-1500 hrs Is due strictly to
cnemlcal removal. If there were r.o emissions after the 0600-0900 period, the
1200-1500 hr concentration ratio would probably be somewhat lower. That is
why only a lower Halt Is computed as follows:
0HM*
AHC
T)
In
CAHC]o/[B]o
tAHCL/[B].
Ir W
(1)
KAhc and Kb are the rate constants for AHC and benzene, respectively. The
initial time (t * 0) is taken to be 0730, while the final tine (t • 6 hrs) is
1330. The minimum OH concentrations required to acooopllsh the decline in
non-benzene AHC concentration are 3.1 x 10® (molec cnT^), 3,11 x 10®, 2.0 x
10®, 2.3 * '0®, 2.8 * 10®, 2.8 x 10® and 1.9 * 10® for toluene, ethyl benzene,
m/p-xylene, o-xylene, 3/1-ethyl toluene, 1,2,1-trimethyl benzene and 1,3,5-
trlmethyl benzene, respectively. (in the case of m/p-xylene the oeta isomer
is assumed to be twice as abundant as the para isomer based on data of
Mayrsohn et al, 1976.J Thus, a morning average OH concentration of at least
2.6 (t 0.6) x 10® molec cm~3 was present at Downey, even during the month of
February. This is not significantly lower than the summertime OH concentra-
tion estimates of 2.5 (± 2.0) x 10® oolec cm~3 (Calvert, 7976J and 2.9 (± 1.9)
x 10® molec cm~^ (Singh et al, 1981b) for thlr region. Assuming a mean day-
time OH abundance of 2.5 x 10® molec cm"^ (nighttime OH is expected to be
negligible In comparison) and the rate constant data provided above, the life
time (e-fold) of AHC3 In the boundary layer of a typical urban atmosphere can
bi computed (in units of sunlit hours) to be benzene-93 hrs, toluene-19 hrs,
ethyl benzene-11* hrs, p-xyl«ne-10 hrs, ra-xylene-5 hrs, o-xylene-9 hrs, ethyl
toluene-8 hrs, 1,2,^-trimethyl benzene-3 hra and 1,3,5-trir>ethyl benzene-2
hrs. In 10 sunlit hears, 10 percent of benzene, 10 percent of toluvne and
64
-------
nearly 99 percent of 1,3»5-trimethyl ben^ono could ba depleted via reaction
with the OH radical alone.
A nearly sixfold difference in the ambient bunzene concentrations was
observed at the San Jose site during different soasons. Figure 28 shows the
diurnal behavior of benzene at this site during April, August, and Docomber.
As 1st typical of many pollutants the highest values for benzene were aoaaurod
during the night and early morning hours.
The increased demand for high outane rating In unleaded fuels has lod to
an Increase in the aromatic content. In tho exhaust, however, the catalytic
converter can preferentially roduce the aroaatio fraction. Typical results
(EPA, 1978) suggest that the AHC fraction Is 1? percont In the exhaust of cars
with catalyst, and 2« percent in cars without catalyst. Figure 29 shows over-
age benzene and toluene concentrations measured at several sites in Southern
California. Because of the possibility of seasonal trends (Shlkiya et al,
1981), data taken during winter months Is excluded from FIgire 21. Further,
it should be noted that each data point in Figuro 29 represents an nvorngo of
a large number of samples. The pre-1970 data nre takon from Altshuller and
Beliar (1961), Lonneman et al, (1968), and Leonard ot al, (1976). Subsequent
data are taken from this study, the results summarized in Brodzlnsky and Singh
(1983), and from Shlkiya et al, (^fll). The Brodzlnsky and Singh (1933) study
is & comprehensive review of all available volatllo organic chemical data for
the period of 1970 to 1930. It is clear from Figuro 29 that benzono and
toluene concentrations have declined dramatically during the last two
decades. Since the mid-1970's, however, tho rato of decline In benzene
concentrations appears to have slowod considerably. It is reasonable to
assume that the concentrations of other AHCs have declined similarly ovor the
last two decades.
In recent years, attempts also have boon modo to measure concentrations
of AhC in clean remote atmospheres. Tablo 13 summarly.es some of theso data.
It is clear from Table 13 that benzene and tolueno ara the dominant spoole3.
Unlike the urban atmosphere, the moan tpluene/ben2ono ratio at mid-latitudes
is only 0.3 to ;.0. Assuming an OH radical concentration of 6 x 10^ moloc
cm"3 in the clean source, it Is possible to computo the residence timo of an
65
-------
U) April less
S 10
lb) Anoint less
-
Ill
1
Time of Dey
Figure 28. Diurnal behavior of benzene at San Jose site during
April, August, and December i985.
66
-------
100
90
00
TO
GO
60
40
y i | v | t'| i |
- ®
I
30 -
29 -
X
o
P 10
K 9
5 6
a i
6 -
6 -
4 -
2 -
i 1 I " I ' I ' I
A
A A
A
e a
© BSMZEME
A TOLUENE
A
O
© o
® A
• -
I I I » i I I I I I I I I « I « I I I I I » I
60 62 64 65
I860
70 73 74 76 78 80 82 84
VEAR >984
Figure 29. Benzene and toluene trend in the atmosphere of the South Coast
Air B»in of California.
67
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TABLE 13- MIDLATITUDE BACKGROUND CONCENTRATIONS OF SOME
AROMATIC HYDROCARBONS IN REMOTE MARINE AND CONTINENTAL ATMOSPHERES
Chemical
Location
Averago Concentration
(ppb)
Source
benzene
Atlantic air (35°N)
0.07 ± 0.03
(1)
Pacific air (15°N)
0.23 ± 0.01)
(2)
Hiwot Rldg9° (10°N)
0.21
(3)
NifcfOt Ridge (10°N)
0.16 ± 0.08
(«)
Pacific air (17°N)
0.23 ± 0.11
(5)
Northern hemisphere
0.05
(5)
Southern hemisphere
0.01
(5)
toluene
Atlantic air (35°N)
0.02 ± 0.01
(1)
Pacific Air (15°N)
0.22 t 0.01
(2)
Niwot Ridge (10°N)
0.11
(3)
Niwot Ridge (10°N)
0.13 i 0.17
(1)
Pacific air (17#N)
0.13 t 0.08
(5)
Northern hemisphere
0.02
(5)
Southern hemisphere
0.006
(5)
o/m/p-xylenes
Atlantic air (188N)
0.01 - 0.02
(6)
Pacific air (10°-0°N)
0.C1 - 0.02
(5)
Indian Ocean (11°S)
0.003 - 0.005
(6)
Source: (1) Penkett (1982); (2) Rasmussen and Khalll (1983);
(3) Creenberg and Zimmerman (1981); (1) Roberts et al. (1984/;
(5) Nutroagul and Cronn (1981); (5) Eichmann et al. (I960).
#Nlwot Ridge is located in the Colorado Rockies.
68
-------
air mass noeded to change toluene/benzene ratio from 1.7 to 0.3-1.0. From
Equation (1) it is estimated that such an air mass would be only 2 to 7 days
away from ita source. To date it is not known if significant nonanthropogenlc
sourcos of Ai'Ca exist.
Oxygentod Spocles
The v/ygonated species, peroxyacetylnitrate (PAN), peroxypropionylnitrate
(PPN), formaldehyde, and acetaldehyde rfere measured. Although these are
dominant constituents of the polluted urban atmosphere, they are also an
important part of the natural atmosphere and play a key role in the
photochemistry of the troposphere (Singh and Hanst, 1981; Low et al, 1981,
Singh et nl, 1986).
Peroxyacetylnitrate and Peroxypropionylnitrate—
It is bvldent from Tables 8 through 10 that average PAN concentrations in
the range of 0.6 to 1.6 ppb were measured at all sites. Maximum concentra-
tions, typically encountered during daytime, were in the range of 2 to 8
ppb. Figure 30 shows the Jiurnal behavior of PAN at the Philadelphia, Downey,
I
Houston, and Denver sites. During the field experiment in Denver, PAN
concentrations in the O.b to 1 ppb were measured during periods of snowfall.
Although PPN could be detected, it was present at much lower concentrations.
Average concentrations of PPN were in the 0.02 to 0.2 ppb range. Frequently
its concentrations were below the detection limit and they never exceeded 1
ppb (Tables 8 and 9). PAN and PPN were not measured during the San Jose
experiments. Average PAN/PPN ratio varied between 7 to 30. Figure 31 shows
the dlirnal bohavior of PPN at the Downey, Houston, and Denver sites.
Formaldehyde and Acetaldehyae—
Measurements cf aldehydes in polluted atmospheres have received much
attention In recent year3 because of their key involvement in photochemical
smog proceaoos as well a3 their potential toxicity (Lloyd, 1979; Albert,
1980). In the past, ambient measurements of formaldehyde have been performed
using the chronotropic acid procedure (Altshuller and. McPherson, 1963; U.S.
Public Health Service, 1965; Fushlmi and Miyaki, 1980) and to a limited extent
69
-------
1 r
(el Pfiileddphb
o.
Q- 1003
I
I
2 god
<
a.
<90
T
(b) Osangy
S
I
I
Z
<
I I I i 1
Tr-
ie) Houston
s
z
<
1111
Id) Denver
ii
a
a.
I
l
Z
<
a.
I
Time of Day
Figure 30. Diurnal behavior of PAN at Philadelphia, Downey
(CA), Houston, and Denver sites.
70
-------
*60
COO
160
100
60
0
K50
*00
IM
100
00
0
s&o
200
150
100
60
0
(i) Oownoy, CA
i
(b) Houoton
1
(e) Denver
1
T
i
1 -L-
Tim® of Day
ure 31. Diurnal behavior of PPN at Downey, Houston, and
Denver sites.
71
-------
by Fourier-transform inf ed spectroscopy (Piatt et al, 1979; Tuazon et al,
1980). In more recent years aldehydes have been measured by reacting them
with 2,4-Dlnitrophenylhydrazine (DNPH), followed by the analysis of the
resultant-hydrozones by high performance liquid chromotography (Kuwata et al,
1979; Kuntz et al, 1980; Funt* and Grosjean, 1981). Ambient aldehyde data
collected by the chromotropic acid procedure are of unsure quality (fJAS,
19S1). To date, the bulk of ambient aldehyde data are available from a few
locations such as Southern California (Grosjean 1982); selected northeastern
sites (Cleveland al, 1977; Tanner and Meng, 193U; Sohalam et al, 1985) and
from Osaka, Japan (Kuwata et al, 1979; 1983). In the present study, we
provide additional formaldehyde and acetaldehyde data in summer and winter
based on a series of nine short term field experiments conducted in eight
cities.
Table 1^ provides a summary of ambient formaldehyde measurements at nine
sites in the United StoLes. Field studies at the first four sites exclusively
employed the chromotropic acid procedure, while at the last five sites the
DNPH-HPLC technique was used. Table 11 shows that during the spring-su.nme'*
period significant levels of formaldehyde (10 to 20 ppb) are present. The
last three studies were performed during the winter-spring period. Com-
parisons at the Denver 3ite clearly show that formaldehyde levels were much
lower in early April as compared to June. In the fir-t week of April the
weather in Denver was very cold, and was associated with periods of snowfall.
Considerable rain was encountered at the Houston site. The weather in
Southern California (Downey) was fair prior to and during our experiment, and
significant formaldehyde concentrations were indeed measured. However, it
does appear that these levels may also be lower than those encountered in the
summertime (Grosjean, 1982). Ambient formaldehyde levels were frequently
below our detection limit (Z 0.^ ppb) during the March Houston and Denver
measurements.
Table 15 summarizes the acetaldehyde concentrations as measured by the
DNPH-HPLC method. Average acetaldehyde concentrations of 8.5 ppb at the
Downey, CA site are significantly higher than the 1-to-2 ppb levels
encountered ^Isevhere. The highest acetaldehyde concentration of 28 ppb was
72
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TABLE 14. AMBIENT FORMALDEHYDE LEVELS THOU SELECTED LOCATIONS
Plelfl 3He Caacrtptlon
Hooaurcmcnt
ttuabcr
or Dau
CcnM^t^allon,
(ppbi
Cltr
Site Address
Period
Points
Hailotcs
Average ia
St. Vwts, tV)
3*00 Pemhjl) M.
5-7 19%
It
19.7
n-3 t *.5 t
CO
Ktriw tt. ma g, *j\gl.
7J-Z* J7f>
16
12.3 i 5.9 C
Htffiralit, I'A
Qlg 5i>rin$ f'4,, and
P«rteflt*r f:4.
8-10 J-jljr i?ao
id
41,0
19.0 t 7.6 c
SUtin tnlarvl, ttl
Wl14 A>o. and Victor/ Blvd.
3-4 April 1981
IT
45.9
14.3 i 9.1 «
Pittsburgh, PA
Carnegie Hoi Ion Campus
15-16 April 19^1
e
28.5
>8.5 1 6.7 ~
Chicago, IL
79th St. and Lavsndela
27-28 April 1961
5
15.6
11.3 t 3.8 ~
Dovncjr. CA
Fane ho Los AiElgoi Hospital
28 Po&ruarjr - 1 March 1981
18
67.7
15.5 t 11.9
Houston, TX
Hjo St. and I - to
Fro/itags fid.
18-19 March 1981
It
22.5
3.8 i 6.3 **
Den/er, CO
Harl
ytirn'/r*virA% * 7-tr/tr », allva
in !Ss*>a/, f,k J.ttrn f-ft rs/aat&r*ilcitta »wa
eC*rwjtro>lc •' netftv]
*««-w) ( t ' £-0«: Tfl fsfiqt'/s) It&i ft &|A
-------
TABLE 15. AMBIENT ACETALDEHYDE LEVELS
FROM SELECTED LOCATIONS
Si:«j Description
Hwi»sr
of Data
Points
Concentration (p ib)
Measurement
Period
Maximum
Average ±o
PA
15-»6 April 1961
8
2.6
I.KiOB
2?-£3 April 1981
5
3-1
2.1 ± 0.9
28 February - 1 March I98t
48
28.4
8.5 t 6.3
1Q-19 March 198«J
11
6.7
2.2 ± 1.7
!>env»r'x Q\>
?-«> April 1986
21
2.1
1.0 ± 0.5
74
-------
also measured at this site. Another Important feature of the Downey sice is
the small formaldehyde to acetaldehyde concentration of 2 compared to a ratio
of 5-to-10 at other sites. At Downey nearly 65 percent of HCHO data lie in
the 5-to-15 ppb rango, while 71 percent of CH^CHO data fall in the 1-to-10 ppb
range. Figure 32 shows the diurnal behavior of these two aldehydes, with
highest concentrations encountered at night. This diurnal pattern is contrary
to the summertime aldehyde behavior where the maximum concentrations during
periods of photochemical smog occurred in the afternoon (Grosjean, 1982).
In remote background environments, HCHO ha3 been measured in the 0.1-to-1
ppb range (Lowe et al, 1981). Methane oxidation reactions suggest a surface
background of about 0.4 ppb. No background concentrations of CH^CHO have been
reported. Analysis of PAN and precursor data by Singh et al, (1985a) suggest
that under clean conditions ambient CH^CHO levels of 0.15-to-0.3 PPb may be
present. The summertime 10-to-20 ppb HCHO levels measured here are not atypi-
cal of other polluted atmospheres (Altshuller and McPherson, 1963; Cleveland
et al, 1977; Joshi, 1979; Kuwata et al, 1979, 1983; Grosjean, 1982; Tanner and
Heng, 198JJ; Schulam et al, 1985). Although acetaldehyde measurements are
relatively sparse, studies from Japan (Hoshika, 1977; Kuwata et al, 1979,
1983) report average acetaldehyde levels of 1.5-to-10 ppb. Srhulam et al,
(1985) find that in Schenectady, N.Y., the bulk of CH^CHO data were in the 0-
to-1 ppb range, and its concentrations never exceeded 5 ppb. High acetalde-
hyde concentrations in the 2-to-')0 ppb range have also been reported from
sites in Southern California (Grosjean, 1982).
In the past it has been reported that in the automobile exhaust 65 to 75
percent (by volume) of all aldehydes Is HCHO while 7 to 10 percent is CH^CHO
(NAS, 1976). It now appears that this ratio may be strongly altered in favor
of CH^CHO in cars equipped with catalyst converters (NAS, 1981). In addition,
significant stationary source emissions car. also exist. In the south coast
air basin of California, HCHO and CH^CHO total emissions of 20 metric tons/day
and 17 metric tons/day have been estimated. Assuming comparable removal
rates, an HCHO/CH^CHO concentration ratio of 1.7 to 1 would result. Needless
tn say, the sources of these aldehydes are varied, and their emissions in many
urban centers are significantly different from the south coast air basin.
75
-------
CH.CMO
> WAftCH ^65*
6 It Ift
29 FEBRUARY \«A
LOCAL Ttue
Figure 32. Diurnal t»Kav*or of fonnaWiahydo and ecotaldehyie concen'rstiom
in Southern California (Dowttay. CA. Site J.
76
-------
fcTUle yeiswry scissions contribute to the atmospheric burden of these
N>Vh eh&oieals are also formed as secondary pollutants by the
a*3N>?il
-------
SECTION 6
TRENDS AND SEASONAL CYCLES
Because of the source complexity and wide variations in meteorological
parameters, short terra experiments such as those performed here are not
suitable for establishing long term trends. Table 16 shows the mean
concentrations of selected anthropogenic species as measured at the San Jsse
site during April, August, and December. During the December experiment, a
high pressure system blanketed the area pushing carbon monoxide levels to 1*4
ppm (the highest in five years). A mixing depth less than 20 meters was
frequently encountered. Although emissions of these chemicals probably vary
seasonally, there Is every indication that thi3 is a small change compared to
the effect of the meteorological parameters observed during the December
experiment. This four—to-slx fold increase implies local sources and a
shallow mixed layer. For chemicals like carbon tetrachloride, where little or
no local sources may exist, the atmospheric levels are nearly invariant.
Further analysis is needed to establish the relationship between ambient
levels and meteorological conditions. It is not possible frcsn this data to
conclude that winter levels in San Jose are typically higher than summer
levels. To the extent that the boundary layer is deeper during summer, it Is
reasonable to assume that reduced summer levels (Table 16) may prevail.
Superimposed on the meteorological conditions are variations in emissions
(which are also not known for any given city) and chemical removal processes.
Table 17 also shows data from four cities which were revisited after a
number of years. One can conclude that the levels of methylene chloride and
trichloroethylene have perhaps declined over the last four to five years.
Once again, no definitive seasonal or long-term trends can be established
without a clear knowledge of the emissions and meteorological conditions.
While detailed meteorological analysis is beyond the scope of this 3tudy, it
may be possible to analyze these data in the futire in the context of
prevailing meteorology. Any attempt to estimate human exposure from these
measurements must also employ meteorological analysis for temporal
extrapolation.
78
-------
TABLE 16. MEAN AMD1ENT CONCENTRATIONS OF SELECTED
CHEMICALS AT TME SAN JOSE SITE DURING
APRIL, AUGUST, AND DECEMBER 1985
Concentration (PPTV)
Chemical
April 1955
August 1985
December 1935
Florocarbors 1 2
1020
861
1435
Methylene Chloride
153^
1119
1101
Carbon Tetrachloride
193
' iJii
155
1,1,1 Trlchloroethane
360
283
1219
Trietiloroethylene
63
68
271
Tetrachloroetnylene
HZ7
2f>H
1058
Benzene
3296
2060
12372
Toluene
5667
390 U
21155 .
79
-------
Tabic 17: MEAN AMBIENT CONCENTRATIONS (pptv) OF SELECT CHEMICALS
BASED ON REVISITS IN DIFFERENT SEASONS AND TEARS
Chemical
Staten Island
Los Angeles/Downey
Houston
Denver
March/April
1981
April/May
1983
April
1979
February
1984
May
1980
March
1984
June
1980
March/April
1984
Fluoroctrbon
512*
566
.
1183
897
512
1005
648
Methylene Chloride
1505
1109
3751
2399
574
324
967
569
Carbon'Tetrachloride
309
387
215
199
404
291
174
264
1,1,1 Trichloroethane
468
403
1028
1161
353
375
713
647
Trlchloroethylene
167
164
399
184
144
6t
198
53
Tetrachloroethylene
292
792
1480
1471
401
169
394
4j4
Benzene
1201
4367
6040
8720
5780
6130
*390
2230
Toluene
8075
7436
11720
16890
10330
7270
6240
3340
"concentrations in PPTV <10*12V/V)
-------
SECTIpN 7
SUMMARY AND CONCLUSIONS
Eight field studies In six United States cities were completed during
this program. Twenty nine chemicals, many of which are bacterial mutagens and
suspect carcinogens, were measured on a round the clock schedule with the help
of an instrumented mobile laboratory. All chemical analyses were perforated
on-site and In real time. The chemical categories targeted for field
measurements included chlorofluoromethanes, halomethanes, haloethanes,
chloropropane, chloroethylenes, aromatic hydrocarbons, organic nitrates, and
aldehydes.
The ambient analysis of these species was possible with the help of
electron capture gas chromatography for the h<*logenated and nitrogenated
species, flame ionization gas chromatography for hydrocarbons, and high-
performance liquid chromatography t aldehydes. Eight field experiments were
performed in the following six cities:
o Philadelphia, Pennsylvania (one experiment; 1-20 April 1983)
• Staten Island, New York (one experiment; 25 April-1 May 1983)
0 Downey, California (one experiment; 18-27 February 198U>
e Houston, Texas (one experiment; 9-17 March 1981)
0 Denver, Colorado (one experiment, 21 March-1 April 1981)
o San Jose, California (three experiments; 1-16 April 1985; 12-21 August
1985; 13-21 December 1985)
Although these studies were of short-term duration, our practice of
around-the-clock opsration allowed for extensive data collection. The degree
of temporal and spatial variability in the atmospheric abundance of toxic
chemicals is clear from data presented. Typical concentrations of most chemi-
cals measured were in the sub-ppb range, with the exception of aromatic hydro-
carbons and formaldehyde (where average concentrations in the 1-to-25 ppb
range were encountered). For most predominantly man-made chemicals, average
concentrations in urban atmospheres were one-to-two orders of magnitude higher
than in clean remote atmospheres.
81
-------
Meteorology appeared to play a strorg role in the average abundance as
well as In the diurnal behavior of these chemicals. Typical diurnal profiles
showed highest concentrations in the night and early morning hours and minimum
values in the afternoon, probably due to deep vertical mixing at this time.
The diurnal patterns in San Jose were somewhat different but they also cleanly
showed the effect of meteorology on the abundance of chemicals. Mean concen-
trations under sevre stagnant conditions encountered at San Jose rose to
to-7 times normal values. Ambient data suggest that aldehydes are signifi-
cantly less abundant in winter compared to summer months. Interpretation of
aromatic hydrocarbon data in Southern California showed that the prevailing
hydroxyl radical concentrations of 2.6 x 10^ molec. cm-^ in February are not
significantly different from values computed for summer. This is in apparent
contradiction to a commonly made assumption that winter hydroxyl levels are
much lower. Analysis of historic data further suggests that the
concentrations of benzene (the dominant toxic chemical in ambient air) and
other aromatic hydrocarbons have declined by a factor of about 10 in the
ambient air of Southern California over the last two decades.
Many organic chemicals il,at. are also mutagens are sufficiently long-lived
to have distributed themselves globally. Carbon tetrachloride, methylene
chloride and tetrachloroethylene are some of the examples. Methyl halides
appear to be a group of naturally occurring mutagens U'at are also globally
distributed.
On the whole, we conclude that typical urban atmospheres contain chemi-
cals that are known to be toxic at much higher concentrations. The risks
associated with exposure to ambient levels of these species are highly uncer-
tain. The task of characterizing the atmosphere, with which this study is
most concerned, is itself, at best, highly ir.oomplete. Much more atmospheric
and toxicity data will be needed to determine the risks associated with long-
term exposures to low levels of toxic species.
82
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