Environ. Sci. Technol. 1989,23, 1253-1258
Murphy, T. J.; Mullin, M. D.; Meyer, J. A. Environ. Sci. Technol. 1987, 21, 155. Westcott, J. W.; Simon, C. G.; Bidleman, T. F. Environ. Sci. Technol. 1981, 15, 1375. Bidleman, T. F. Anal. Chem. 1984, 56, 2490. Burkhard, L.P.;Andren, A. W.; Armstrong, D. E. Environ. Sei. Technol. 1985, 19, 500. Atlas, E.; Foster, R.; Giam, C. S. Environ. Sei. Technol. 1982, 16, 283. Miller, M. M.; Ghodbane, S.;Wasik, S. P.; Tewari, Y. B.; Martire, D. E. J . Chem. Eng. Data 1984,29, 184. Burkhard, L.P.;Armstrong, D. E.; Andren, A. W. J. Chem. Eng. Data 1985,29, 248. Dobbs, A. J.; Cull, M. R. Environ. Pollut., Ser. B 1982,3, 289. Dickhut, R.M.; Andren, A. W.; Armstrong, D. E. Environ. Sci. Technol. 1986, 20, 807. Opperhuizen,A.; Gobas, F. A. P. C.; Van der Steen, J. M. D.; Hutzinger, 0. Environ. Sei. Technol. 1988, 22, 638. Valsaraj, K.T. Chemosphere 1988, 17, 875. McKinney, J. D.; Singh, P. Chem.-Biol. Interact. 1981,33, 271.
118 and 2.8 Pa m3 mol-’. Increasing ortho chlorine substitution results in larger values of both PLand H, so that non-ortho chlorine substituted isomers have the lowest values for a given chlorine number. Such PL and H data should enable congener-specific environmental behavior for PCBs to be more accurately determined.
Literature Cited Shiu, W. Y.; Doucette, W.; Gobas, F. A. P. C.; Andren, A.; Mackay, D. Environ. Sci. Technol. 1988, 22, 651. Shiu, W. Y.;Mackay, D. J. Phys. Chem. Ref. Data 1986, 15, 911. Hawker, D. W.; Connell, D. W. Environ. Sei. Technol. 1988, 22, 382. Doucette, W. J.;Andren, A. W. Environ. Sci. Technol. 1987, 21, 82. Kamlet, M. J.; Doherty, R. M.; Carr, P. W.; Mackay, D.; Abraham, M. H.; Taft, R. W. Environ. Sci. Technol. 1988, 22, 503. Burkhard, L.P.;Armstrong, D. E.; Andren, A. W. Environ. Sei. Technol. 1985, 19, 590. Dunnivant, F. M.; Elzerman, A. W. Chemosphere 1988,17, 525. Doskey, P.V.; Andren, A. W. Environ. Sci. Technol. 1981, 15, 705.
Received for review October 3,1988. Revised manuscript received April 7, 1989. Accepted May 22, 1989.
Long-Term Measurements of Atmospheric Polychlorinated Biphenyls in the Vicinity of Superfund Dumps Mark H. Hermanson+ and Ronald A. Hites”
School of Public and Environmental Affairs and Department of Chemistry, Indiana University, Bloomington, Indiana 47405 The concentrations of polychlorinated biphenyls (PCBs) in the atmosphere of Bloomington, IN, were analyzed over a period of 22 months. The sampling sites were within 14 km of three landfills contaminated with PCBs. The atmospheric PCB concentrations varied with the atmospheric temperature; thus, there was a large seasonal component to the data. The vapor-phase PCB concentrations averaged 1.7-3.8 ng m-3 in the summer and 0.27-0.58 ng m-3 in the winter. Particulate-phase PCBs did not exhibit consistent chan es with season; the concentrations averaged 0.04 ng m- The logarithm of the ratio of the PCB concentration in the vapor phase to that in the particulate phase was a linear function of reciprocal absolute temperature. Atmospheric PCB concentrations in Bloomington differed only by a factor of 2-3 compared to other areas in the Great Lakes region, indicating that the atmosphere may effectively disperse PCBs within short distances from sources.
f.
Introduction Polychlorinated biphenyls (PCBs) are ubiquitous contaminants in the Earth’s atmosphere (1-16). Previous studies have given us some information on typical atmospheric concentrations, geographical variability, and vapor-particulate partitioning. However, there are two problems with these data. First, because data reporting schemes have evolved over time, there is a considerable variation in the published data. For example, some studies have identified the commercial PCB mixture (6-8,10,12); some studies have quantitated “total PCB” as the sum of ‘Present address: Center for Great Lakes Studies, University of Wisconsin-Milwaukee, Milwaukee, WI 53204. 0013-936X/89/0923-1253$01.50/0
two (9,13,12)or three ( 6 , I O ) commercial mixtures; and some studies have identified representative PCB congeners (I,3,II). Other studies have reported PCB concentrations in both vapor and particulate phases (I, IO, I3), while others have reported only a “PCB” value (2-5, 7-9). The second problem relates to seasonal variability. In our earlier studies on Isle Royale in Lake Superior ( I ) , we observed a large seasonal variation in atmospheric PCB levels. For example, the PCB concentrations in the summer were 5 times higher than the concentrations in the winter. If there is a large seasonal variation, this further complicates the comparison of the data cited above. We, therefore, thought it was important to determine the seasonal variability of PCB concentrations at one location. If it were possible to understand the functional relationship between atmospheric concentration and temperature, it would then be possible to correct future atmospheric measurements to a common temperature in order to achieve comparability. Our study used long-term sampling at multiple sites within a local area, employed quantitation of a large number of PCB congeners in both vapor and particulate phases, and included temperature observations. Specifically, we sampled airborne vapor and particulate-adsorbed PCBs at three sites in the Bloomington, IN, area from October 1986 to August 1988. Long-term sampling enabled us to observe seasonal changes in individual congener and total vapor and particulate PCB concentrations, changes in vapor-to-particulate partitioning, and variability of PCB concentrations among the three sites. In addition, this study provides base-line atmospheric PCB concentrations for the Bloomington area, where a trash-fueled incinerator is proposed for thermal destruction of 650000 m3 of
0 1989 American Chemical Society
Environ. Sci. Technol., Vol. 23, No. 10, 1989 1253
Figure 1. Bloomington, IN, area air sampling locations, Superfund dump sites, proposed incinerator site, and interim storage facility site.
PCB-contaminated materials from three Superfund dump sites and from an interim PCB storage facility (see Figure 1). Experimental Section
Sampling Sites. We located three samplers on rooftops in the Bloomington area to correspond to locations where the atmosphere is expected to be affected most and least by stack emissions from the proposed incinerator. These areas were identified in a risk assessment model (17). A site in downtown Bloomington, on the Monroe County Courthouse (see Figure l),was closest to the Superfund dumps, but it was in the area expected to be affected least by the stack emission. The other sites, on the Batchelor Middle School and on the former Sanders School, were in areas of less urban development but nearer the proposed incinerator and in areas of greater estimated effect of the stack emissions. The Batchelor site was also 1km from the interim storage facility, which was being filled with PCB-contaminated material during part of our sampling period (April to October 1987). All Superfund sites, the interim storage facility, the proposed incinerator site, and our three sampling locations were located within an area of 123 km2 (48 mi2). Sample Collection. We collected samples with Hi-Vol air samplers (Sierra-Misco, Berkeley, CA, Model 650) modified for simultaneous particulate and vapor collection using a system evaluated by Lewis et al. (18). Particles larger than 0.1 pm in diameter were collected on a 2043cm X 25.4 cm glass fiber filter (GFF) (Gelman Science, Ann Arbor, MI), the first trap in the sampler airstream. The filters were heated at 450 "C before sampling to clean them. Particulate sampling included gravimetric mea-
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surement of total suspended particulate loadings (TSP). Vapors were adsorbed into a 9.5 cm X 10.0 cm polyurethane foam plug (PUF) cartridge behind the GFF in the sampler air stream (12). Before sampling, the PUF cartridges were cleaned by Soxhlet extraction in acetone, dichloromethane, and petroleum ether (each for 24 h). Samplers were calibrated with a venturi calibrator (Sierra-Misco; Model 1080) every 3 months or whenever samplers were moved or repaired. Flow was set to a known amount, approximately 0.5 m3 min-', before the collection of each sample. Our sample volumes ranged from 700 m3 in summer to 1500 m3in wiater. We selected these volumes because they provided sufficient sample for the observation of many congeners at a signal to blank ratio of at least 5. Breakthrough of di- through tetrachloro congeners was a potential problem because these homologues together make up 94% of Aroclor 1242 (19), which was present in the Bloomington dumps. Some dichloro congeners in particular would be prone to breakthrough, as observed by Burdick and Bidleman (20),because of their higher vapor pressures (21). We tested for breakthrough four times during the project by collecting PCBs on a PUF plug cut into upper and lower halves. These halves were separated after sampling and analyzed for PCBs. The upstream half should contain most or all of the PCBs if breakthrough has not occurred. Thus, an upper to lower ratio would be high if no breakthrough has occurred. A ratio equal to or less than 1 indicates breakthrough. Results of our experiments show measurable quantities of only a few di- and trichloro congeners in the lower PUF plug. Upper to lower ratios of less than 3 were found only for a few dichloro congeners.
Table I. Total Vapor and Particulate PCB Concentrations and Air Temperatures for Three Bloomington Sites
year 86 86 86 87 87 87 87 87 87 87 87 87 87 87 87 87 87 87 87 88 88 88 88 88 88 88 88 88
Julian day
vapor, ng/mS Courthouse Batchelor
300 316 338 15 28 29 48 70 72 83 103 138 166 194 236 264 287 320 348 25 53 75 110
0.47 0.40 nm 0.81 nm nm 0.24 0.70 nm nm 1.3 5.6 6.3 6.9 4.6 6.3 2.9 0.67 2.0 0.30 0.86 0.51
111
1.4 2.6' 3.4' 9.3 20
144 168 193 215
1.1
nmb nm 0.68 nm 0.33 nm nm nm nm 1.1 0.55 2.1 1.9 1.7 2.0 2.4 2.4 0.56 0.24 0.036 0.21 0.12 nm 0.60
Sanders nm nm nm nm nm 0.83 nm nm 0.48 nm 2.8 1.8 3.0 2.3 nm 0.83 0.80' 3.6 0.32 0.18 0.23 0.06 nm 0.26
1.1
1.1
2.3 1.7 4.8
3.5 1.6 8.0
Courthouse partic, partic: ng/m3 fig/€!
Batchelor partic, partic: ng/ms rglg
Sanders partic, partic: crg/g ng/m3
0.079 0.053 nm 0.066 nm nm 0.032 0.15 nm nm 0.078 0.087 0.18 0.0048 0.048 0.0075 0.11 0.032 0.063 0.081 0.071 0.036 0.054 0.052 0.029' 0.O7gc 0.075 0.11
nm nm 0.043 nm 0.018 nm nm nm nm 0.097 0.0018 0.0047 0.030 0.0071 0.013 0.012 0.21 0.039 0.025 0.015 0.039 0.0069 nm 0.054 0.010 0.029 0.097 0.085
nm nm nm nm nm 0.0046 nm nm 0.041 nm 0.012 0.057 0.11 0.41 nm 0.042 0.033' 0.069 0.015 0.027 0.0034 0.036 nm 0.069 0.027 0.41 0.055 0.088
nm nm nm nm nm nm 0.26 2.1 nm nm 1.6 0.98 1.6 nm 0.91 0.21 0.98 0.55 nm 2.4 0.79 0.96 1.0 0.72 0.63 1.6 1.3 0.82
nm nm nm nm 0.43 nm nm nm nm 2.5 0.06 0.08 0.16 nm 0.40 0.35 2.4 1.0 0.98 0.42 0.15 0.36 nm 0.85 0.30 0.74 0.49 0.88
av temp, OC
nm nm nm nm nm 0.13 nm nm 0.72 nm 0.43 1.4 0.57 nm nm 0.59 0.59 2.0 0.45 0.21 nm 1.3 nm 2.2 0.80 9.6 0.47 0.75
16.1 -6.0 4.2 5.3 6.1 3.7 5.3 5.0 14.2 13.3 16.0 27.5 32.4 26.6 24.2 20.3 18.4 19.6 4.2 -7.9 12.8 1.6 11.7 17.3 19.8 21.8 24.4 35.3
"PCB concentrations per gram of total suspended particles (TSP). brim, not measured because no sample was taken. 'Duplicate measurements.
Sample Analyses. After being weighed for TSP, the glass fiber filters were extracted with benzene in a Soxhlet apparatus for 24 h. PUF was extracted in petroleum ether for 24 h in a Soxhlet apparatus built especially to accommodate the large cartridge. A known amount of 2,2',3,4,4',5,6,6'-octachlorobiphenyl [IUPAC no. 204 (22); Ultra Scientific, Hope, RI] was added to each GFF and PUF before sample extraction to serve as a quantitation standard. Following extraction, both the PUF and GFF extracts were reduced in volume; they were then cleaned with a 10-cm column of 3% deactivated silica gel (100-200 mesh). The sample was eluted with hexane, 10% dichloromethane in hexane, and dichloromethane. The hexane and 10% dichloromethane fractions were combined and used for the analysis of PCBs. The required volumes of these fractions were determined experimentally a t the beginning of the project when we spiked PUF with the internal standard and with an Aroclor 1242 standard. Quantitation. We analyzed all samples with a Hewlett-Packard 5890A gas chromatograph equipped with an 63Ni electron capture detector (ECD), a 30-m DB-5 capillary column (J&W Scientific, Folsom, CA), and an H P 7671A autosampler. Each vapor sample was analyzed in triplicate. Particulate samples were analyzed only once because they were much less concentrated than vapor samples. The GC temperature program used a 1-min hold a t 70 "C,then a ramp to 160 OC at 30 OC min-', then a t 1.5 "C m i d to 260 OC, and at 10 "C min-' to 280 OC. We used splitless injection at 225 "C; the ECD was held at 325 "C. Helium carrier gas flow was 1.9 mL min-' at 70 OC. A 95% argon and 5% methane mixture was used for the makeup gas. Total flow was 21 mL min-'. The instrument was calibrated relative to the quantitation standard (PCB 204) for congener specific mea-
surements with a mixture of Aroclors 1232,1248,and 1262 in a 251818 ratio. The wide range of this mixture includes most environmentally important PCB congeners. The concentrations of the individual congeners in these three Aroclors has been previously determined (23). The calibration mixture was analyzed after each group of samples to verify that the instrument could reproduce the calibration. Our samples consistently showed 61 of the calibrated GC peaks (78 congeners). Field blanks were collected and analyzed with each set of samples and the amount of the blank was subtracted from the sample on a congener-by-congenerbasis. The size of this correction was small, usually -5% of the sample. Occasionally, for particulate samples taken in the winter, the correction was as large as 40%. The linear range of the instrument response started a t 0.1 ng, which was at least 10 times the instrumental limit of direction. At a level of 0.1 ng, the relative standard deviation was -5%. Results and Discussion
The PCB concentrations in the vapor phase and in the particulate phase (relative to both the air volume and to the particulate weight) are given in Table I along with the average atmospheric temperature during the sampling period. This table has been subdivided by the three sampling sites. Samples were taken 28 times during the period October 1986 to August 1988. Overall Distribution. Concentrations of the vapor and particulate samples were averaged over all locations and temperatures on a congener-specific basis. If airborne PCBs in Bloomington were derived only from the Aroclor 1242 present in the Superfund dumps, these averages should correlate well with the composition of this Aroclor mixture. On a congener by congener basis, we calculated a correlation coefficient (r) of 0.579 for the vapor phase and 0.672 for the particulate phase (see Figure 2). For Environ. Sci. Technol., Vol. 23, No. 10, 1989
1255
c99
a
Y
Y
A*
8
0 1
3 2
!Lrocl01 E t 2
IOIIC.
,
!/I
-
---
I!
0i
1 0
Batchelor
+
a
I l l
110)
0
10
20
30
40
Alerage temperature. deg C Figure 3. Regression of the logarithm of the total (vapor plus particulate) PCB concentratlon versus the average air temperature for the three Bloomlngton area sampling sites. The correlation coefficients are as follows: Batchelor 0.890, Courthouse 0.852, and Sanders 0.803.
25 degrees of freedom, the significance level is 0.487 at the 99% level of confidence. Our values are, thus, highly correlated. Although there is more scatter than we would like, it is clear that the atmospheric PCB composition is similar to that of Aroclor 1242, the major PCB mixture present in the dumps. Note that the particulate concentrations (right axis of Figure 2) are a factor of 100 less than the vapor-phase concentrations (left axis). Thus, the PCBs in Bloomington’s atmosphere are primarily in the vapor phase. Seasonal and Site Comparisons. The effects of changing seasons or, in effect, changing air temperature, are apparent in total vapor PCB concentrations at all three sites, where higher concentrations occur in warmer months and lower in the winter. In fact, the most concentrated vapor sample observed during the project was collected on the warmest day at the Courthouse site. The sample taken on the coldest day from the Batchelor site showed the lowest vapor concentration in this study. A regression on a congener-by-congener basis indicated that 56 out of 61 congeners were significantly correlated (5% level) with the average atmospheric temperature. On the other hand, the particulate concentrations did not exhibit a seasonal trend; only 18 congeners were significantly correlated with atmospheric temperature. To simply show this effect, we combined the vapor and particulate concentrations of each sample into a total PCB value and regressed the logarithm of these values versus the average air temperature. This analysis showed that the PCB concentrations increase with increasing air temperature at all three sites (see Figure 3). It is apparent that the Courthouse site is more concentrated by a factor of -3 than either of the other two sites. Closer proximity of the Courthouse site to the Superfund sites may be a source of this difference. There may also be other, as yet unrecognized, sources near the Courthouse site. It is also 1256
3 4
3 5
36
37
3A
3’)
1000 / ( a l e t e m p )
i%)
Figure 2. Regression of the atmospheric concentrations of 27 PCB congeners In the vapor phase (left axis) and in the partlculate phase (right axis) versus the concentration of those congeners In Aroclor 1242.
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Environ. Sci. Technoi., Vol. 23, No. 10, 1989
Flgue 4. Regregskn of the kga”of the vapor-to-partlculate ratios for PCB congeners 99, 149, and 180 versus the inverse of the average absolute air temperature for ail of the Bloomlngton sites. There are five, six, and seven chlorine atoms in these three congeners, respecthrely. The correlation coefficlents are 0.779, 0.674, and 0.782, respectively.
possible that this site is simply exhibiting an elevated level due to its relatively more urban characteristics. The Batchelor site showed the lowest total vapor PCB concentrations despite the presence of the interim storage facility -1 km away (see Figure 1). Particulate PCB concentrations are very low and are not as site specific as vapors. Sanders and Courthouse values were usually the highest, as observed with the vapor values, but the differences between the three sites were sometimes small. We present particulate concentrations in Table I in two forms (in ng m-3 and in pg g-’ TSP). While temporal differences in the former concentrations vary over 2 orders of magnitude in the extreme cases, the TSP-based numbers are more consistent. This indicates that changes in total atmospheric particulate concentrations contribute to the scatter observed in the volume-based concentrations. Vapor-to-ParticulateRatios. The observation of low particulate PCB concentrations compared with cosampled vapors in atmospheric samples made here and by others (I,2 , I I ) suggests that the vapor-to-particulate (V/P)ratios in our samples would be high. In fact, we observed widely scattered, but high (>loo), VIP ratios especially for the lower chlorinated congeners. The functional relationship between the VIP ratio and atmospheric temperature has been reviewed by Bidleman (24);he tells us that the logarithm of the V I P ratio is a linear function of the reciprocal of the atmospheric temperature (in degrees Kelvin). In most cases, the particulate concentrations in this relationship are expressed relative to the TSP. In our case, however, we saw only a slight improvement in the regressions if TSP was included; thus, for simplicity, we regressed the logarithm of the VIP ratio versus the reciprocal of the average temperature. The correlation coefficients between these two parameters were significant (at the 5% level) for 54 congeners out of 61. As examples, Figure 4 shows plots of log (VIP)versus 1/T for congeners with IUPAC no. 99,149, and 180, one each from the penta-, hexa-, and heptachlor0 homologue classes. All three congeners showed similar trends with temperature. Congener 180 exhibited VIP ratios 6 times less than the others, some of them falling below 1. Note that our regression analysis revealed no differences between the three sampling sites, suggesting that the VIP ratio is consistent at a given time. Comparison to Other Sites. The atmospheric PCB concentrations from this study and from several others, including contaminated and remote sites, are given in Table 11. Given the large effect that temperature seems to have on the atmospheric concentrations and given the (largely unknown) differences in sampling temperatures represented by the data in Table 11, it is difficult to com-
Table 11. Comparison of Atmospheric PCB Concentrations (in ng m-a) location
vapor
particulate
ref
Bloomington, IN" Monroe County Courthouse summer 3.8 0.049 g winter 0.58 0.06 Batchelor Middle School 1.7 summer 0.021 winter 0.27 0.027 Sanders School 1.9 summer 0.074 winter 0.38 0.018 Neal's Landfill (a PCB dump)b upwind 85 8 hotspot 8650 downwind 1300 after cleanup upwind 225 hots p ot 3900 925 downwind Ontario, Canada PCB dump during cleanup worksite 123 117 13 5 m from source 92 51 17 23 5-99 m from source 4 >lo0 m from source 8 Milwaukee, WIc winter 2.25 0.37 10 Madison, WIc summer 0.2 7.49 10 Minneapolis, MN 9 7.5d Chicago, IL 5 5.5e Lake Michigan' summer 10 0.87 0.13 Lake Superior 1.2d 3-year mean summer 9 Isle Royale, MIa summer 2.8 0.06 1 winter 0.59 0.025 Gulf of Mexico 0.21d mean of five off-shore sites 2 0.72d mean of three on-shore sites Antarctica mean of four off-shore sites 0.1If 4 Indian Ocean 50-70' south latitude 0.085f 4 " Reported as geometric mean of several observations. bReported as Aroclor 1242. cSum of three Aroclors. dCombined vapor and particulate concentrations. e Vapor-to-particulate partitioning not reported. f Vapor concentrations only. #This study.
pare these values. Nevertheless, it is interesting to note that the atmospheric PCB values in Bloomington are lower than in some other cities around the Midwest. This is true despite the widespread PCB contamination in Bloomington. The highest mean Bloomington vapor value is similar to those from Madison, Minneapolis, Chicago, and the relatively remote Isle Royale. This suggests that there is little difference in atmospheric PCB concentrations as a function of location. In fact, the Batchelor and Sanders sites in Bloomington show lower vapor concentrations than at Isle Royale, but these sites show comparable values to another observation on Lake Superior. Lake Michigan and shoreline areas around the Gulf of Mexico show vapor PCB concentrations somewhat lower than the Batchelor and Sanders sites, but this may not be significant. Bloomington particulate values, although widely scattered, are similar to Isle Royale, but much less than summer values reported for Lake Michigan and Milwaukee and Madison, WI. The concentrations in the vicinity of Neal's Landfill are much higher than the concentration at the Courthouse, 15 km to the east. This may suggest that the atmosphere
is effectively diluting vapor-phase PCBs emitted from this and other Superfund sites. Major differences also appear in Table 11. Winter concentrations for Milwaukee are a factor of 5-10 higher than winter concentrations in Bloomington. The vapor concentrations from the Ontario cleanup site and its surroundings are less than observed at Neal's Landfill. The particulate values at this Ontario site, however, are unusually high in comparison with vapor concentrations. High concentrations of airborne particulates during cleanup of contaminated soil may have influenced this result. Other major differences are the concentrations reported for the most remote sites in Table 11: Antarctica and the Indian Ocean. These concentrations are an order of magnitude lower than the sites in Bloomington. This may be an indication of PCB stratification between the Northern and Southern hemispheres. Acknowledgments
We are grateful to I. Basu for technical assistance throughout the project. We are indebted to Monroe County, IN, the Monroe County Community School Corp., and Mr. Jerry Chasteen for allowing us to locate and operate our air samplers on their properties. Registry No. Arochlor 1242, 53469-21-9. Literature Cited Swackhamer, D. L.; McVeety, B. D.; Hites, R. A. Environ. Sci. Technol. 1988, 22, 664-672. Giam, C. S.; Atlas, E.; Chan, H. S.; Neff, G. S. Atmos. Enuiron. 1980, 14, 65-69. Jan, J.; Tratnik, M. Chemosphere 1988, 17, 809-813. Tanabe, S.; Hidaka, H.; Tatsukawa, R. Chemosphere 1983, 12, 277-288. Murphy, T. J.; Formanski, L. J.; Brownawell, B.; Meyer, J. A. Enuiron. Sci. Technol. 1985, 19, 942-946. Hollod, G. J. Thesis, University of Minnesota, Minneapolis, MN, 1979. Lewis, R. G.; Martin, B. E.; Sgontz, D. L.; Howes, J. E. Environ. Sci. Technol. 1985, 19, 986-991. Sgontz, D. L.; Howes, J. E. Ambient Monitoring for PCB After Remedial Cleanup of Two Landfills in the Bloomington, Indiana Area. U.S. Environmental Protection Agency Report, EPA/600/4-86/018 (NTIS No. PB86177532); 1986. Eisenreich, S. J.; Looney, B. B.; Hollod, G. J. In Physical Behavior of PCB in the Great Lakes; Mackay, D., Patterson, S., Eisenreich, S. J., Simmons, M. S., Eds.; Ann Arbor Science: Ann Arbor, MI, 1983; Chapter 7. Doskey, P. V.; Andren, A. W. J. Great Lakes Res. 1981, 7, 15-20. Wittlinger, R.; Ballschmitter, K. Chemosphere 1987, 16, 2497-2513. Bidleman, T. F.; Olney, C. E. Bull. Environ. Contam. Toxicol. 1974, 11, 442-450. Hosein, H. R.; Gray, L.; McGuire, J. J. Air Pollut. Control ASSOC.1987, 37, 176-178. Locating and Estimating Air Emissions from Sources of Polychlorinated Biphenyls (PCB). U.S. Environmental Protection Agency Report, EPA-450/4-84-007n (NTIS No. PB87-209540); 1987. Murphy, T. J.; Rzeszutko, C. P. J. Great Lakes Res. 1977, 3,305-312. Stachan, W. M. J.; Huneault, H. J . Great Lakes Res. 1979, 5, 61-68. Application for an Air Quality Permit to Construct a Proposed Bloomington Incinerator Facility. Westinghouse Electric Corp., 1986. Lewis, R. G.; Brown, A. R.; Jackson, M. D. Anal. Chem. 1977,49, 1668-1672. Albro, P. W.; Parker, C. E. J. Chromatog. 1979, 169, 161-166. Environ. Sci. Technol., Vol. 23,No. 10, 1989
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(20) Burdick, N. F.; Bidleman, T. F. Anal. Chem. 1981, 53, 1926-1929. (21) Foreman, W.T.;Bidleman, T. F. J. Chromatog. 1985,330, 203-216. (22) Ballschmitter, K.;Zell, M. Fresenius 2.Anal. Chem. 1980, 302,20-31.
(23) Mullin, M. D. PCB Workshop, Grosse Ile, MI, 1985. (24) Bidleman, T.F. Environ. Sci. Technol. 1988,22,361-367.
Received for review November 15,1988. Accepted April 25,1989. This work was supported by the Environmental Technology Division of the Westinghouse Electric Corp.
Biogeochemical Processes Affecting Arsenic Species Distribution in a Permanently Stratified Lake Patrick Seyier' and Jean-Marie Martin Institut de BiogQochlmie Marine, Unit6 Associ6e au CNRS 386, Ecoie Normale Superieure, 1 Rue Maurice Arnoux,
92 120 Montrouge, France
Arsenic species, iron, and manganese distributions were studied in the oxidizing and reducing waters of Lake Pavin, a small and well-stratified crater lake situated in the Maasif Central range (France). Arsenate and arsenite concentrations versus depth do not reflect the expected thermodynamic equilibria, indicating a slow and incomplete response to the redox conditions. The occurrence of arsenic in the anoxic zone results from transport on a particulate phase, due to adsorption onto iron and manganese oxides and probably to incorporation in phytoplanktonic organisms. Introduction
In recent years attention has been paid to those elements that exhibit multiple oxidation states in water. Arsenic (1, 2 ) , iodine and chromium (3), antimony (4, 5 ) , and selenium (6,7) are of particular interest to evironmentalists because certain of them may be more toxic than others. It has been shown that arsenic can be found in natural systems as arsenite [As(III)],arsenate [As(V)],and organic arsenic species (1,8-10). Thermodynamic calculations lead to the prediction that, at equilibrium, As(V), should be the only stable oxidation state in oxic water, whereas in anoxic systems As(II1) should be the stable dissolved form (11). Indeed, in waters containing dissolved oxygen, arsenate is the dominant species but arsenite is present in significant amounts (10% of total As). In anoxic basins or in the pore water of sediments, arsenite is found at concentrations exceeding those of arsenate, but arsenate is still present (3,12,13). Therefore the redox couple of arsenic does not appear to be in thermodynamic equilibrium, either in oxic or in anoxic systems. Several biotransformations, which could explain this disequilibrium, have been found to occur in laboratory cultures: redox transformation between As(II1) and As(V) by bacteria, fungi, and planktonic algae; biosynthesis of complex organoarsenic compounds by organisms and subsequent degradation giving stable methylated species (14-1 7). The aim of this paper is to determine which biological or chemical processes are controlling the redox state and the chemical cycle of this element across an oxic-anoxic interface. Due to its permanent anoxic deep layer, Lake Pavin, a deep crater lake in the volcanic range in the center of France (Figure 11, appeared to be most suitable for such a purpose. It is located at 45O55' N, 2'54' E, far from important industrial zones at an altitude of 1200 m. The main characteristics of the lake have been described by Martin (18). Owing to its restricted and forested watershed-a factor limiting mechanical erosion-and to the complete dominance of diatoms in the lake flora, the 1258
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Sci. Technol., Vol. 23,No.
10, 1989
bottom sediments are almost pure diatomaceous deposits with negligable detrital material. Chemical conditions within the water column vary from a well-oxygenated upper layer, through a transition zone between 50 and 65 m where oxygen concentrations decrease to zero and hydrogen sulfide appears, to a permanently anoxic bottom layer. According to limnological classification, the Pavin lake can be considered as strictly meromictic. As suggested by previous studies (19-22) the lake water budget must be balanced by an additional input from sublacustrine freshwater springs. Using mathematical modeling based on tritium data, Meybeck et al. (19) and Martin (18)have shown that such sublacustrian inputs would occur in the anoxic compartment. In addition to the determination of As(II1) and As(V) in the water column and in the surface layer of sediments, we determined the concentrations of dissolved oxygen, hydrogen sulfide, iron, and manganese and the pH. We measured all these parameters simultaneously and at close enough intervals near the oxic-anoxic interface to determine the detailed structure of the oxidized and reduced species profiles. Materials and Methods
Sampling. Samples were collected in December 1984. Owing to the small area and circular shape of Lake Pavin, sampling was performed at the middle and deepest part of the lake. In order to collect appropriate samples at the oxic-anoxic boundary, preliminary measurements of dissolved oxygen, temperature, and transmissivity were performed prior to sampling. Temperature and dissolved O2were determined with an Orbisphere Model 2609 apparatus, and transmissivity was obtained with a Montedoro-Whitney transmissometer. The water samples were collected in a precleaned Niskin bottle hung on a nylon hydrowire. To prevent oxidation of reduced species, water was immediately filtered on board through a syringe filtering assembly (Millipore, Swinnex) attached at the outlet of the Niskin bottle. Any contamination by air is thus avoided during the collection of the sample. The Nuclepore filters (0.4pm) were soaked before use in diluted hydrochloric acid. Two filtered subsamples were sealed in precleaned bottles; one for determination of arsenic species was stored in the dark at 4 OC,and another was acidified with 1%HNOB(Suprapur, Merck Inc.) to determine dissolved iron and manganese. All samples were analyzed for As less than 72 h after sampling. The effects of storage on the determination of As(II1) have been previously discussed (23). This study showed that no change in the As speciation was detectable for 240 h under
0013-936X/89/0923-1258$01.50/0
0 1989 American Chemical Society
