(36) (37) (38) (39) (40) (41) (42) (43) (44) (45) (46) (47) (48) (49)
for the Petroleum Association for the Conservation of the Canadian Environment. Ottawa, ON, Canada, May 1988. Stroo, H., personal communication, Remediation Technologies, Inc., Seattle, WA, 1989. Shiaris, M. P.; Cooney, J. J. Appl. Enuiron. Microbiol. 1983, 45, 706-710. Liu, Z.; Edwards, D. A.; Luthy, R. G. Sorption of Nonionic Surfactants onto Soil, submitted to Water Res. Rosen, M. J. Surfactants and Interfacial Phenomena, 2nd ed.; John Wiley and Sons: New York, 1989. Vigon, B. W.; Rubin, A. J. J.-Water Pollut. Control Fed. 1989,6I, 1233-1240. Robichaux, T. J.; Myrick, H.N. J . Pet. Technol. 1972,24, 16-20. Sherrill, T. W.; Sayler, G. S. Appl. Enuiron. Microbiol. 1980, 39, 172-178. Rosenberg, M.; Rosenberg, E. J. Bacteriol. 1981,148,51-57. Wodzinski, R. S.; Coyle, J. E. Appl. Microbiol. 1974, 27, 1081-1084. Stucki, G.; Alexander, M. Appl. Environ. Microbiol. 1987, 53, 292-297. Thomas, J. M.; Yordy, J. R.; Amador, J. A.; Alexander, M. Appl. Environ. Microbiol. 1986, 52, 290-296. Asther, M.; Lesage, L.; Drapron, R.; Corrieu, G.; Odier, E. Appl. Microbiol. Biotechnol. 1988, 27, 393-398. Swisher, R. D. Surfactant Biodegradation; Surfactant Science Series 18; Marcel Dekker: New York, 1987. Larson, R. J.; Games, L. M. Environ. Sci. Technol. 1981, 15, 1488-1493.
(50) Giger, W.; Brunner, P. H.; Schaffner, C. Science 1984,225, 623-625. (51) Osburn, Q.W.; Benedict, J. H. J. Am. Chem. SOC.1966,43, 141-146. (52) Giger, W.; Stephanou, E.; Schaffner, C. Chemosphere 1981, 10, 1253-1263. (53) Stephanou, E.; Giger, W. Environ. Sci. Technol. 1982,16, 800-805. (54) Sheldon, L. S.; Hites, R. A. Enuiron. Sci. Technol. 1978, 12, 1188-1194. (55) Ventura, F.; Figueras, A.; Caixach, J.; Espadaler, I.; Romero, J.; Guardiola, J.; Rivera, J. Water Res. 1988,22,1211-1217. (56) Miller, R. M.; Bartha, R. Appl. Enuiron. Microbiol. 1989, 55, 269-274. (57) Edwards, D. A.; Liu, Z.; Luthy, R. G. Nonionic Surfactant Solubilization of Hydrophobic Organic Compounds in Soil/Aqueous Systems. Department of Civil Engineering, Carnegie Mellon University, Pittsburgh, PA, 1991. Submitted to J . Enuiron. Eng. (58) Almg-ren, M.; Grieser, F.; Thomas, J. K. J . Am. Chem. SOC. 1979, 101, 279-291. (59) Attwood, D.; Florence, A. T. Surfactant Systems: Their Chemistry, Pharmacy and Biology; Chapman and Hall: London, 1983.
Received for review January 2,1991. Revised manuscript received June 12,1991. Accepted June 26,1991. This work was sponsored by the US.EPA Office of Exploratory Research under Grant R-815235-01-1.
Methylchloroform and Tetrachloroethylene in Southern California, 1987-1 990 Mohamed W. M. Hlsham and Danlel Grosjean” DGA, Inc., 4526 Telephone Road, Suite 205, Ventura, California 93003
By use of on-site electron capture gas chromatography, ambient levels of methylchloroform and tetrachloroethylene were measured in 1987-1990 at 21 southern California locations. The highest concentrations recorded were 61 ppb for CH3CCI3and 20 ppb for C2C1,, with 24-h averages of up to 28 ppb for CH3CC13and 12 ppb for C2CI4. Concentration ratios to that of a “background” site, San Nicolas Island, were 5-31 for CH3CC13and 1.3-6.2 for C2Cl,. At coastal and central locations, ambient levels during the fall were higher than during the summer, with fall summer ratios of up to 6 for both compounds. Spatial an diurnal variations are compared to those of peroxyacetyl nitrate (PAN) and are discussed in terms of emissions and transport.
/
Introduction
In the United States alone, some 2.7 billion pounds of toxic chemicals were discharged into the air in 1987 ( I ) . These toxic chemicals include a number of chlorinated hydrocarbons, which are used extensively as solvents, synthetic feedstocks, and household products and in the production of textiles and plastics. Many of these compounds are toxic and exhibit mutagenic and/or carcinogenic properties. Recent proposals to strengthen the Montreal Protocol on substances that deplete the ozone layer include the phase-out of chlorinated hydrocarbons such as methylchloroform and carbon tetrachloride (2). Information on ambient levels of chlorinated hydrocarbons 1930 Environ. Sci. Technol., Vol. 25, No. 11, 1991
is of direct interest in the context of regulatory action concerning toxic air contaminants and global air pollution. This study focuses on two important anthropogenic chlorinated hydrocarbons, methylchloroform and tetrachloroethylene. In the Northern Hemisphere, the “background” concentration of methyl chloroform was 158 ppt in 1985 and has been increasing at a rate of 8 ppt per year (3,4). Tetrachloroethylene is more reactive and as such does not have a global background concentration, but is ubiquitous in urban and industrial atmospheres. In southern California (Los Angeles urban area), some 12OOO metric tons of tetrachloroethylene and 13000 metric tons of methylchloroform are released every year (5). With these chlorinated hydrocarbons as a “signature”, transport of the Los Angeles urban plume eastward as far as southern Nevada has been documented (6,7). We have measured ambient levels of methylchloroform (CH3CC13)and tetrachloroethylene (CC12=CC1,) at 21 locations in southern California. These measurements were made as part of five field surveys carried out in 1987-1990. In 1987, measurements were made simultaneously at up to nine locations (8)as part of the Southern California Air Quality Study (9). In 1988-1990, measurements were made as part of surveys of air quality at 10 museums in southern California (10-13). In 1989, measurements were made as part of an air quality study carried out a t two locations in the eastern end of the southern California urban area (14). Diurnal, seasonal, and spatial variations are discussed, drawing upon a set of more than 6500 observations of ambient methylchloroform and tetrachloroethylene.
0013-936X/91/0925-1930$02.50/0
0 1991 American Chemical Society
Experimental Methods Gas Chromatography Analysis with Electron Capture Detection, All measurements were carried out in situ using SRI 8610 gas chromatographs with Valco 140 BN electron capture detectors (5 mCi, 63Nifoil-operated in the constant-current, variable-frequency-pulsedmode). The GC columns used were 50-180 cm long, 1/8 in. diameter Teflon packed with 10% Carbowax 400 on 60180 mesh Chromosorb P (15). The GC oven and detector temperatures were 30 and 60 “C, respectively. The carrier gas was ultrahigh purity nitrogen. The 3-mL sampling loop was housed in the GC oven. Measurements carried out at museums included two sampling loops connected to a timer-activated, 10-port Valco sampling valve, with two sampling lines to collect indoor and outdoor air (10). Ambient air was sampled at flow rates of 190-425mL/min by using ’/, in. diameter, 4-12 m long Teflon sampling lines, The sampling line residence times were 0.19-0.88 min. We verified in the laboratory that no loss of CH3CC13 or CzC14occurred in the sampling lines. The automated EC-GC were operated round-the-clock, yielding ambient air chromatograms every 30-60 min. Under the conditions employed, compounds that elute include, in order of increasing retention time, oxygen (a large peak at the beginning of the chromatogram), carbon tetrachloride and CH3CC13,methyl nitrate (16),CzCl4, and peroxyacetyl nitrate (PAN (15)). Typical retention times were 1.56 rnin for CCl,, 1.58 rnin for CH3CC13,2.55 rnin for CH30NO2,3.68 min for trichlorethylene, 4.30 min for C2C14,and 7.70 min for PAN. While retention times varied from one EC-GC to the next as a function of column length and slight differences in operating conditions, we verified that the ratio of retention times was essentially constant from one instrument to the next. Retention time ratios relative to PAN were 0.19 f 0.02 for CCl, and CH3CC13, 0.33 for CH30N02,0.45 for trichlorethylene, and 0.54 f 0.05 for CzCl4 (8). Instrument Calibration, Precision, and Detection Limits. Calibrations were carried out by injecting precisely metered microliter amounts of high-purity CH3CC13 and CzCl4 in a known volume of purified air, using a 3.5-m3 chamber constructed from FEP Teflon film and a l.0-m3 cube-shaped Plexiglass chamber lined inside with FEP Teflon film. Calibration curves (peak height vs concentration) were constructed from at least three independently prepared dilutions of CH3CC13and CzC14in pure air (8). These calibration curves were linear for CH3CC13(up to 90 ppb), CzCl4 (up to 28 ppb), and carbon tetrachloride (CCl,, up to 8 ppb), with intercepts of 0 f 0.05 ppb, correlation coefficients of >0.998, and standard deviations on the slopes (Le., a measure of precision) of 4.1-4.5’3, (8). The calibration curves were obtained by using one “reference” EC-GC, under conditions identical with those employed for all other EC-GCs in the field. While response factors (Le., the slope of the calibration curve) varied somewhat from one instrument to the next, we verified that the ratio of these responses factors to that of PAN was the same (within experimal precision) from one instrument to the next, Le., 0.69 for CH3CC13and 0.26 for CzC14 (8). We conservatively assigned a peak height of 3 mm on attenuation setting 3 as a minimum detectable peak height. This corresponds, on the “reference” GC, to ambient air detection limits of 0.5 ppb for CH3CCI, and 0.2 ppb for C2Cl4. Detection limits for all field instruments are given by the product of the reference GC detection limits and the ratio of the corresponding response factors. These detection limits are listed in Table I. Interferences. As mentioned before, ambient air chromatogramsobtained with the GC conditions described
Table 1. Detection Limits
location
date 1987 6/19-26 7/12-15 8f 26-914 11111-12/11 6118-913 6/19-26 7f 12-913 11111-12/11 6/19-7114 7/14-15 8127-911 911-10 6/19-7116 8127-121 11 6/19-26 7/13 7/14-15 11/11-14 11114-12/12 6/19-7113 7113-914 11111-12/11 6/19-7116 8/ 26-914 7/13-16
detection limit, PPb CH3CCl3 C&14
0.7 1.7 1.0 0.6 1.8 1.3 1.1 3.6 1.5 1.1
0.57 0.06 0.17 0.33 0.36 0.60 0.42 0.36 0.51 0.54 0.18 0.18 0.54 0.23 0.63 0.27 0.63 0.36 0.27 0.75 0.50 0.42 1.35 0.51 0.42
1988 7/18-27 7126-815 8/1-15 8/9-22 8122-912
0.5 0.5 0.5 0.5 0.5
0.2 0.2 0.2 0.2 0.2
8129-917 9/7-16 9/12-19 9/ 26-101 12
0.5 0.5 0.5 0.5
0.2 0.2 0.2 0.2
Burbank (Gene Autry) Perris Palm Springs
1989 8/7-20 8/25-27 8/23-25
0.5 0.1 0.1
0.2 0.04 0.04
Burbank (Gene Autry)
1990 5/7-11
0.1
0.04
Anaheim
Azusa Burbank Claremont
Los Angeles Hawthorne
Long Beach Rubidoux San Nicolas Island downtown LA (El Pueblo) Ventura (Olivas Adobe) west LA (LACMA) Pasadena (Huntington) south-central LA (Natural History) west LA (Page) west LA (UCLA) Malibu (Getty) northeast LA (Southwest Museum)
1.5 0.15 0.45 0.9 1.0 1.5 1.1 0.9 1.4 1.3 0.5 0.4 1.4 0.6
1.7
above contained peaks corresponding to CCl, + CH,CCl,, C2C14, and PAN. These compounds were well-resolved from each other (base-line resolution) as well as from methyl nitrate (16). To investigate potential interferents, a standard mixture obtained from Dr. Rasmussen and prepared and calibrated in his laboratory was reanalyzed in our laboratory under conditions identical with those we employed for our field measurements. The mixture was contained in an internally passivated stainless steel canister and included CC14, CH3CC13,and C2C14along with 15 chlorinated, brominated, and aromatic hydrocarbons at concentrations of 0.5-1.1 ppb in air (8). To analyze this 18-component mixture, small aliquots of air from the canister were brought down to atmospheric pressure and injected directly on our reference EC-GC with a 3-mL sampling loop. While CC14, CH3CC13,and C2C4eluted at the expected retention times, none of the other 15 components of the mixture was observed in the chromatograms. These compounds may coelute with the large oxygen peak, may be retained on the column and/or elute after more than 20 min, or were not detected at the concentrations tested, i.e., 0.5-1.1 ppb. Environ. Sci. Technol., Vol. 25, No. 11, 1991 1931
Table 11. Maxima and 24-h-Averaged Concentrations methylchloroform, Dob highest range of 24-h av
location and date (monthjyear) San Nicolas Island, 6-9/87 Hawthorne 6-9/87 11-12/87 Long Beach 6-9/87 11-12/87 Anaheim 6-9/87 11-12/87 Los Angeles 6-9/87 11-12/87 Burbank 6-9/87 11-12/87 Azusa, 6-9 f 87 Claremont, 6-9/87 Rubidoux, 6-9/87 LA (El Pueblo), 7/88 Ventura (Olivas), 7-8/88 west LA (LACMA), 8/88 Pasadena (Huntington), 8-9/88 south-central LA (Natural History), 8-9/88 west LA (Page), 8-9/88 west LA (UCLA), 9/88 Malibu (Getty), 9/88 northeast LA (Southwest Museum), 9-10188 Burbank (Gene Autry), 8/89 Perris, 8/89 Palm Springs, 8/89 Burbank (Gene Autry), 5/90
1.2
0.55-0.57
17.9 36.9
0.8-7.0 0.8-18.0
61.0 22.3
tetrachloroethvlene. tmb highest range of 24-h av 1.2
0.42-0.70
2.3 112
0.8-2.3 1.2-4.0
2.2-14.7 2.2-9.9
8.3 14.6
0.3-3.3 0.5-2.7
11.0 23.8
0.5-8.5 13.2-22.2
4.8 11.9
0.1-1.3
29.8 19.2
2.7-6.3 8.3-14.0
4.0 5.5
0.5-1.5 1.2-2.6
28.0 32.0 36.6 15.0 51.3 28.5 6.5 17.5 8.5 4 >30a
1.2-6.1 7.1-28.4 3.2-17.1 0.6-7.9 3.3-15.0 1.7-6.5 0.5-2.7 1.6-2.2 2.1" 9.9
0.13-1.17
1.2-6.1
>20"
13.6
>20'
6.7 3.8
0.6-1.1 0.2-0.6 0.3-1.6 1.2-2.7 0.2-0.5 0.2-0.5 10.7->12n 0.2-0.8 0.10-0.25 0.15-0.22 0.19-0.25
1.7
5.9 8.6 2.7 1.1 >12' 2.2 0.4 0.3 0.7
'Exceeded operating range of instrument. Table IV. Ratio of Ambient Air Concentrations to Those Measured at San Nicolas Island
Table 111. Comparison with Literature Data
date
location
1985 Anaheim Azusa Burbank Lennox El Monte Long Beach Los Angeles Rubidouv Upland 1987 Claremont Cajon Summit Claremont
methylchloroform, PPb
tetrachloroethylene, PPb
2.3 f 1.4 2.6 1.7 3.3 f 1.7 2.5 1.5 7.1 f 4.7 3.0 f 3.1 2.4 2.6 1.1 f 0.7 1.8 f 1.1 1.3 3.0 1.0-4.0 1.0-4.0
3.1 f 2.4 2.0 1.8 2.7 f 1.6 2.3 f 2.3 1.6 f 0.9 1.0 f 0.6 1.2 f 0.9 0.5 f 0.3 0.7 f 0.4 0.53 f 0.99 0.25-0.75 0.25-0.75
* * * *
site/SNI" ref San Nicolas Island Hawthorne S' F Lo& Beach
Sb 17b 6' 6d
aAnnual averages. bEleven 24-h samples between 6/19 and 913. cTen - to fifteen samples per day, 6115-7/31. d7/12-7/19.
Interlaboratory Comparison Studies. We compared the results of the calibrations obtained with our own standards (dilution of a single chlorinated hydrocarbon in purified air) to those obtained with the standard mixture obtained from Dr. Rasmussen. The results provide some measure of accuracy and indicated agreement within f1.570 for tetrachloroethylene and within fl6.8Y0 for carbon tetrachloride + methylchloroform (8). Instrument Long-Term Stability. We have verified, in the course of several projects, that calibration factors of the reference instrument for PAN have not substantially changed during the 2-year period 1987-1989, e.g., 222 f 9,258 f 10,287 f 11, and 222 f 3 ppt/mm (at,tenuation setting 3) for calibrations carried out in December 1987, July 1988, November 1988, and September 1999, respectively (€9,even though this instrument had been exten1032
Environ. Sci. Technol., Vol. 25, No. 11, 1991
location'
5a
F Anaheim
Sb F Los Angeles
Sb F Burbank Sb
F Azusa Claremont Rubidoux LA (El Pueblo) Ventura (Olivis) west LA (LACMA) Pasadena (Huntington) south-central LA (Natural History) west LA (Page) Malibu (Getty) northeast LA (Southwest Museum)
methylchloroform
tetrachloroethylene
1.0 (ref)
1.0 (ref)
5.7 21.5
2.2 4.8
14.1 10.5
2.8
5.0 28.1
0.8 5.3
7.5 16.5
3.0
5.2 30.8 16.2 7.8 16.8 4.5
1.7
1.5 2.0 6.2 2.0 1.3 2.0 1.8
2.1
3.4 12.3
1.4
51.8
1.4 3.6
1.6 5.2
'S, summer, June-Sept 1987; F, fall, Nov-Dec 1987. See Table I1 for details. *Using mean of all 24-h-averaged values at each location.
Table V. Summary of Seasonal Variations
location
summer av, PPb
Hawthorne Long Beach Anaheim Los Angeles Burbank
3.4 8.5 3.0 4.5 3.1
methylchloroform fall av, fall to ppb summer ratio 12.9 6.3 16.9
9.9 18.5
tetrachloroethylene fall av, fall to PPb summer ratio
summer av, ppb
3.8 0.7 5.6 2.2 6.0
1.3 1.0 0.5 0.9 1.2
2.2 1.7 6.4 2.0 3.1
2.9 1.7 3.2 1.8 3.7
12
Ib
a
10
2 5-
8
2 0-
n
U
4
a P n
2u 2
u
d 155
6
N
u
4
IO-
2
0 5-
0
0
4
8
12
16
20
0.04 0
.
, 4
.
, 8
Tlrne,PDT
.
, 12
.
, I6
.
,
.
20
I 24
Tlme.PDT
Figure 1. Composite diurnal profiles for methylchloroform (a) and tetrachloroethylene (b), downtown Los Angeles, summer (open symbols) and fall 1987 (dark symbols).
sively used in the field and in the laboratory. For chlorinated hydrocarbons, calibrations performed 12 months apart agreed within 3% for CH3CC13and C2C14(8). Thus, the responses of the electron capture detectors employed in this study did not vary substantially with time. Sampling Locations. In 1987, measurements were carried out at up to nine locations: Anaheim, Azusa, Burbank, Claremont, Hawthorne, Long Beach, Los Angeles, Rubidoux, and San Nicolas Island. Measurements were carried out simultaneously at all nine locations in June and July, at seven locations in August and September (those listed above except Hawthorne and San Nicolas Island), and at five locations in November and December: Anaheim, Burbank, Hawthorne, Long Beach, and Los Angeles. A more detailed description of these sampling locations has been given previously (9, 15). In 1988-1990, outdoor air samples were collected as part of a survey of indoor/outdoor levels of air pollutants at 10 Southern California museums, one located in Ventura County (Olivas Adobe, Ventura) and nine located in Los Angeles County: one in downtown Los Angeles (El Pueblo Historical Park), one in south-central Los Angeles (Natural History Museum), three in west Los Angeles (Los Angeles County Museum of Art, Page Museum, University of California Research Library), one in Malibu (J. Paul Getty Museum), one near Burbank (Gene Autry Western Her-
itage Museum), one in Pasadena (Huntington), and one about midway between Los Angeles and Pasadena (Southwest Museum). A more detailed description of these sampling locations can be found elsewhere (10-13). In 1989, measurements were carried out in the eastern region of the southern California urban area, Perris and Palm Springs, 90 km east-southeast and 120 km east of Los Angeles, respectively (14). Contribution of CC14. Concentrations for each of the two coeluting compounds, carbon tetrachloride and methylchloroform, cannot be calculated from our data alone. However, there are no known sources of CCl, in southern California, and literature data indicate that ambient levels of CC14in southern California are essentially constant and correspond to the current background level of CCI, in the Thus,we have northern hemisphere,0.11 ppb (5,6,17,18). calculated methylchloroform concentrations by simply subtracting, from the height of the peak corresponding to the two coeluting compounds, a constant height equivalent to 0.11 ppb CC14.
Results and Discussion Ambient Air Concentrations. Listed in Table I1 are maxima and 24-h-averaged concentrations for methylchloroform and tetrachloroethylene according to sampling Environ. Sci. Technol., Vol. 25, No. 11, 1991
le33
a
6
b
a
5
6
4
a
D
4
n a
M
4
c
U u
M
E U
4
3
u
I U
M
X U
2
2
1 2 3 4 5 6 7 8 9 lOll121314151€
9192021222321
1 2
3 4
5 6 7 8
9 101112131415161718192021222324
T i m e, PDT
Time,PDT
Flgure 2. Composite diurnal profiles for methylchloroform, downtown Los Angeles (a) and Claremont (b), summer 1987. 6 -
b
a
C
. a
Tirne.PD1
I2
15
,23
Tirne,PDT
Flgure 3. Composite profiles for CH,CCI, C,CI, and PAN in south-central Los Angeles (Natural History, a) and at two west Los Angeles (Wilshire) locations (LACMA, b; Page, c) summer 1988. Code: (a) C,CI, open symbols, PAN dark symbols; (b) C2CI, dark diamonds, PAN open squares, CH,CCI, dark squares; (c) C,CI, dark symbols, PAN open symbols.
location-, Individual values for all days and all locations can be found elsewhere (8, 10-14). The highest concentrations recorded were 61 ppb for methylchloroform and >20 ppb for tetrachloroethylene (the operating range of our instruments was exceeded on several occasions, thus yielding “off-scale”peaks). The maxima recorded in 1987 on days selected for their forecasted poor air quality were in the range 11-61 ppb for methylchloroform and 2.3->20 ppb for tetrachloroethylene. The maxima recorded in 1988-1990, during which no attempt was made to carry 1934 Environ. Sci. Technol., Vol. 25, No. 11, 1991
out measurements only on days of poor air quality, were 0.3->30 ppb for methylchloroform and 0.3->12 ppb for tetrachloroethylene. The 24-h-averaged concentrations ranged up to 28 ppb for methylchloroform and up to >12 ppb for tetrachloroethylene. Listed in Table I11 are recent literature data for southern California locations (5, 6, 17). Our results are in general agreement with literature values, including those obtained in 1987 by other investigators as part of the same air quality study 16, 17).
a
4
E
I2
I6
20
Tirne,PDT
b
0
4
12
16
20
in the range 1.6-30.8 for methylchloroform and 1.3-6.2 for tetrachloroethylene, clearly reflecting the contribution of urban area emissions for both compounds. Spatial variations reflected prevailing meteorology. During the summer, inland (eastward) transport of the smog front resulted in elevated concentrations a t the downwind (eastern) locations, e.g., Azusa, Claremont and Rubidoux. During the fall, increased air stagnation (le? dispersion) resulted in high concentrations at the coast2 and central locations, e.g., Hawthorne, Long Beach, Burbank, downtown Los Angeles, Anaheim, and northeast Los Angeles (Southwest Museum). As is shown in Table V, fall to summer concentration ratios a t the coastal and central locations were up to 6.0 for methylchloroform and up to 6.4 for tetrachloroethylene. This is illustrated in Figure 1 for downtown Los Angeles, where summer and fall composite diurnal profiles (Le., diurnal profiles constructed from averages of all hourly observations at one location) are contrasted for CH3CC13and CpCl,. The observed concentration increase at coastal and central locations during the fall could reflect increased emissions rather than unfavorable meteorology. This is unlikely, since we have observed the same seasonal increase for PAN (15), which has no known emission sources, on the same days at, the same locations. Diurnal Variations. Diurnal variations in methylchloroform and tetrachloroethylene concentrations showed substantial variations according to location and season. In general, diurnal variations were more pronounced during the summer (reflecting eastward transport) than during the fall (reflecting more stagnant conditions), as we have shown earlier for downtown Los Angeles in Figure 1. Summertime transport is clearly evidenced in Figure 2, which compares the methylchloroform composite diurnal profiles obtained in downtown Los Angeles (maximum at noon) and in Claremont, some 40 km east of Los Angeles (midafternoon maximum). With PAN as a "reference" (PAN has no direct sources and is formed in situ by photochemical reactions during transport), it is possible to examine methylchloroform and tetrachloroethylene diurnal profiles for their source-dominated and transport components. For example, Figure 3 shows composite diurnal profiles in south-central Los Angeles (Natural History Museum) and in the Wilshire area of west Los Angeles (LACMA, Page Museum). The chlorinated hydrocarbon profiles in south-central Los Angeles exhibit several morning maxima associated with transport of different air masses containing incrsasing amounts of PAN, which peaks around noon as expected. In the same way, CH3CC13 and C2C14maxima at the two west Los Angeles locations occur several hours earlier than that for PAN. At the more downwind locations (Figure 4), the CH,CCl, and C2Cl, maxima essentially coincide with the corresponding PAN maxima, reflecting the predominance of transport over direct emissions. Thus, a t the easternmost location included in this study, Palm Springs, both PAN and CzC14 exhibited summer maxima in the late evening, e.g., between 10 p.m. and midnight (14).
T i rn e. PDT
Figure 4. Composite proflles for CH3CC13,C,CI, and PAN in northeast Los Angeles (Southwest Museum, a) and Burbank (Gene Autry Museum, b). Code: (a) CH3CCI, dark symbols, PAN open symbols; (b) PAN open symbols, C&I, dark squares, CH3CC13dark diamonds.
Spatial and Seasonal Variations. Table IV summarizes the ratios of ambient air concentrations of methylchloroform and tetrachloroethylene measured a t all locations to those measured at the "control" site, San Nicolas Island (SNI). Site/SNI ratios of 24-h-averaged values were
Acknowledgments
John Coghlan, Skip Robinson, John Twilley, Carol Verheyen, Christopher Coleman, Kathryn Sibley, Cheri Doyle, Lisbet Thoresen, and Mary Ellen HennesseyNottage facilitated the field measurements a t their institutions. Rei Rasmussen (Oregon Graduate Center) kindly provided us with a standard mixture prepared and calibrated in his laboratory. Michael Redgrove (California Air Resources Board) and Rei Rasmussen made available Environ. Sci. Technol., Vol. 25, No. 11, 1991
1935
chlorinated hydrocarbon data relevant to this study. At DGA, Edwin Williams contributed to instrument calibrations, Eric Grosjean provided support in the field operations and in data reduction, Fabrice Grosjean assisted in data reduction, and Denise Yanez prepared the draft and final versions of the manuscript. Registry No. PAN, 2278-22-0; CH3CC13, 71-55-6; CpCl,, 127-18-4.
Literature Cited National inventory of potentially toxic pollutants. Superfund Amendments and Reauthorization Act, Title 111, US. Environmental Protection Agency, Washington, DC, 1989. Zurer, P. Chem. Eng. News 1989,67(49),4-5. Rasmussen, R. A.; Khalil, M. A. K. Sci. Total Environ. 1986, 48, 169-186. Rasmussen, R. A.; Khalil, M. A. K. Science 1986, 232, 1623-1624. Shikiya, D.; Liu, C.; Nelson, E.; Rapaport, R. The magnitude of ambient air toxics impact from existing sources in the South Coast Air Basin. Revision Working Paper No. 3, Planning Division, South Coast Air Quality Management District, El Monte, CA, 1987. Barnstable, H. G.; Rogers, D. P.; Shorran, D. E. Atmos. Environ. 1990,24B, 137-151. Miller, D. F.; Shorran, D. E.; Moffer, T. E.; Rogers, D. P.; White, W. H.; Macias, E. S. J . Air Waste Manag. Assoc. 1990,40, 757-761. Hisham, M. W. M.; Grosjean, D. Southern California Air Quality Study: Toxic Air Contaminants, Task I, Final Report to the California Air Resources Board, Agreement A832-152, DGA, Inc., Ventura, CA, J a n 1990.
(9) Lawson, D. R. J. Air Waste Manag. Assoc. 1990, 40, 156-165. (10) Hisham, M. W. M.; Grosjean, D. Environ. Sci. Technol. 1991,25, 857-862. (11) Hisham, M. W. M.; Grosjean, D. Abstracts of Papers, 198th National Meeting of the American Chemical Society, Miami Beach, FL, Sept 10-15,1989 American Chemical Society: Washington, DC, 1989; ENVR 69. (12) Hisham, M. W. M.; Grosjean, D. Atmos. Environ. 1991, Z A , 1497-1505. (13) Grosjean, D.; W i l h n s , E. L., II; Hisham, M. W. M. Removal of pollutants by carbon and permanganate-alumina filtration systems in museums: a case study. Final report t o the Getty Conservation Institute, DGA, Inc., Ventura, CA, Sept 1990. (14) Williams, E. L., 11; Grosjean, D. Inland Areas Air Quality Study: A One-Yenr Survey of Ambient Levels of Aldehydes, Nitric Acid and Peroxyacetyl Nitrate (PAN) in Palm Springs and Perris, June 1989June 1990. Final report to the South Coast Air Quality Management District, DGA, Inc., Ventura, CPL,Nov 1990. (15) Williams, E. L.; Clrosjean, D. Atmos. Environ. 1990,24A, 2369-2377. (16) Grosjean, D.; Parniar, S. S.; Williams, E. L. Atmos. Enuiron. 1990,24A, 1207-1210. (17) Rasmussen, R. A. Chlorinated Hydrocarbon data during SCAQS. Dept. of Environmental Sciences, Oregon Graduate Institute, Beaverton, OR, 1987. (18) Redgrove, M., California Air Resources Board Technical Services Division, Sacramento, CA, personal communication, 1989.
Received for review January 8,1991. Revised munuscript received June 17, 1991. Accepted June 25, 1991. This work has been supported in part by the California Air Resources Board, Sacramento, CA, Agreement A832-152, The Getty Conservation Institute, Marina del Rqy, CA, and the South Coast Air Quality Management District, El Monte, CA.
COMMUNICATIONS Interaction of Quicklime with Polychlorobiphenyl-Contaminated Solids David L. Sedlak, Kirk E. Dean, David E. Armstrong, and Anders W. Andren" Water Chemistry Program, University of Wisconsin, Madison, Wisconsin 53706
Introduction A recent press release (I) from the United States Environmend Prokction Agency (u.s.EPA) stated that the application of quicklime (CaO) to soils at a polychlorobiphenyl- (PCB-) sik in significant decreases in PCB concentrations. ~~b~~~~~~experiments on the interaction of quicklime and PCBs performed by a u.s, EPA contractor(2) led to the conclusion that the observed losses were attributable to an abiotic chemical reaction. Results of the laboratory experiments did not indicate either a specific reaction mechanism or the identity of the constituents present in quicklime responsible for catalyzing the reaction. Furthermore, the experiments did not fully disprove the possibility that physical processes, such as volatilization, were responsible for the observed losses. The EPA Risk Reduction Engineering Laboratory in Cincinnati, OH, is performing fur1036 Environ. Sci. Technol., Vol. 25, No. 11, 1991
ther experiments with quicklime (3),and their preliminary results suggest that Physical Processes may be The possibility that quicklime could provide a Simple, effectivem a n s of removing PCBs from contaminated soils would have profound implications for waste treatment, and further examination of this phenomenon is merited. The hydration of quicklime (reaction 1 ) is a highly exothermic reaction, and relatively high temperatures can be reached in quicklime-amended soils. For example, CaO + HzO
-
Ca(OH)2
(1)
hydration of a sample of commercial grade quicklime with a small quantity of water results in temperatures of 80-90 "C within several minutes. Increased temperatures in quicklime-amended soils could cause PCB losses through either the effect of temperature on abiotic reaction rate constants or enhanced volatilization.
0013-936X/91/0925-1936$02.50/0
0 1991 American Chemical Society
