Environ. Sci. Technol. 1994, 28,2008-2013
Atmospheric Concentrations of Polychlorinated Biphenyls at Bloomington, Indiana Sandra Y. Panshln and Ronald A. Hites’
School of Public and Environmental Affairs and Department of Chemistry, Indiana University, Bloomington, Indiana 47405 Air samples were collected at Bloomington, IN, in 1993 and analyzed for PCBs. Bloomington has several PCB sources and is the location of three U.S. Environmental Protection Agency Superfund sites. The 1993 data were compared to 1986-1987 data for the same site after correcting for atmospheric temperature by using the Clausius-Clapeyron equation. We found that the concentrations of each congener and of total PCBs had not changed in the intervening 6 years. We calculated heats of vaporization for each congener; they had a mean of 63 f 16 kJ/mol. We also calculated atmospheric residence times for each congener. These had a mean value of 49 f 16 days. We calculated the flux of vapor-phase PCBs from Bloomington to the atmosphere using two methods. The first yielded a range of 16 to 60 pg m-2year-l; this took into account changes in atmospheric temperature. A concentration gradient model gave a flux of 53-165 pg m-2 year-1 a t 25 OC. Combining the results of the two methods gives a total flux range of 16-165 M m-2 gear-l.
Introduction
As shown in the previous paper (I),the total concentration of polychlorinated biphenyls (PCBs) in the remote, North Atlantic atmosphere has remained constant since 1973 (at least; its half-life is greater than 23 years). This atmospheric stability of PCB concentrations is in direct contrast to the trends observed in other environmental compartments. For example, PCB concentrations in Lake Ontario sediment closely track United States’ sales of PCBs, which peaked in the late 1960sand declined rapidly until 1977when production ceased (2). Fish from the Great Lakes also have exhibited decreasing concentrations of PCBs, with half-lives of about 8 years (3). Concentration decreases have also been observed in Arctic ringed seals ( 4 ) ,polar bears ( 5 ) , and herring gull eggs (6). Having observed no change in atmospheric PCB concentrations at aremote, marine site, we decided to compare these results with a contaminated, continental site. Bloomington, IN, is such a site. It is located in the middle of the United States, far from marine influences. Large amounts of PCBs were used in the manufacture of capacitors and transformers in Bloomington, and their disposal led to the severe contamination of six sites around the city. In fact, three of these sites have been placed on the U S . Environmental Protection Agency’s Superfund list. Some remediation of the sites took place in the mid1980s;the most contaminated soil was placed in an interim storage facility designed to prevent PCBs from entering the atmosphere or any other environmental compartment. A trash-fueled incinerator has been proposed to thermally destroy the PCB-contaminated material from the interim storage facility and from the three Superfund sites. In 1986-1987, Hermanson and Hites (7) measured atmo-
* E-mail address: 2008
[email protected].
Environ. Sci. Technol., Vol. 28, No. 12, 1994
spheric PCB concentrations a t three sites around Bloomington to establish baseline values prior to construction of the incinerator. The sampling sites were chosen by Hermanson and Hites to represent areas affected by the stack emissions from the proposed incinerator. One of the sampling sites was the Monroe County Courthouse, a site surrounded by residential neighborhoods. Total PCB concentrations at this site ranged from 0.3 to 20 ng/m3, depending on atmospheric temperature. The Courthouse site was not expected to be significantly affected by stack emissions according to a risk-assessment model (8), but the other two sites, Batchelor Middle School and Sanders School, were. These two locations are 10-15 km south of the center of Bloomington and had similar atmospheric PCB concentrations, ranging from 0.04 to 4.8 ng/m3 at Batchelor Middle School and from 0.06 to 8.0 ng/m3 a t Sanders School. At all three Bloomington sites, the atmospheric concentrations were higher than in Bermuda (where we measured values of 0.1-1.0 ng/m3), and they were higher than in other parts of the Great Lakes region (where concentrations typically range from 0.1 to 2 ng/m3, with occasional values as high as 3 ng/m3) (1, 9-13). Hermanson and Hites (7)found that the atmospheric PCB concentrations exhibited a strong temperature dependence, with the concentration increasing with temperature. This same effect (although smaller) has been noted by Manchester-Neesvigand Andren (10) for a site in northern Wisconsin and by Hoff et al. for a site in Ontario (11). This temperature effect is not apparent in Bermuda. The purpose of this study was to compare Bloomington’s atmospheric PCB concentrations measured in 1993 with those measured in 1986-1987, taking into account temperature effects. We were interested in knowing whether the atmospheric concentration had changed in the past 6 years for several reasons. First, PCBs have not been used in transformer production in Bloomington since 1976 (7, 8), and there should have been no new inputs since that time. We wanted to know, therefore, whether the lack of new inputs translated into decreased atmospheric concentrations. Second, much of the PCB-contaminated material was contained in an interim storage facility; we wanted to know whether this facility effectively eliminated the source of PCBs to the atmosphere. Third, the incinerator proposed to destroy the contaminated material has not yet been built. Although a study to determine baseline PCB concentrations was conducted in 1986-1987, no current values were available. By returning to one of the sites used in the previous study, we could determine whether these baseline values were still valid. Fourth, we knew that atmospheric PCB concentrations have remained constant at Bermuda, a remote site with no sources; we wanted to determine whether PCB concentrations had remained constant near a PCB source. Experimental Section
Air samples were collected at Batchelor Middle School in Bloomington, IN, from April to June 1993. Samples 0013-936X/94/0928-2008$04.50/0
0 1994 American Chemical Society
-20
-29
-30
2 fn
2 (I -31 -
c
v
G -32
-33
0.0032
0.0033
0.0034
0.0035
0.0036
0.0037
0.0038
0.0039
inverse temperature (1/T)
Flgure 1. Natural logarithm of partial pressure versus inverse absolute atmospheric temperature for total PCBs. The regression line was determined by combining the 1986-1987 and 1993 data sets; the P value is 0.708.
were collected using a high-volume air sampler (SierraMisco, Berkeley, CA) located on the roof of the school (about 10 m above ground). Sample sizes ranged from 1000 to 2000 m3, Air was drawn first through a glass fiber filter to collect particles and then through a polyurethane foam (PUF) plug to collect vapor-phase PCBs. The PUF plugs were 10 cm in diameter and 10 cm long. Split plug experiments were performed to assure that PCBs were quantitatively trapped on the PUF. The only congeners that were collected on the back half of the plug were a few trichloro PCBs, but even for these compounds, the ratio of front plug to back plug amounts was greater than 1O:l. Prior to sampling, glass fiber filters were heated at 450 OC for 8 h to remove organic contaminants. PUF plugs were rinsed thoroughly with tap water and rinsed with acetone. They were then soxhlet extracted for 24 h with acetone and then for 48 h with petroleum ether. The plugs were air-dried for 24 h and sealed in glassjars. Immediately prior to sampling, the PUF plugs were placed in glass cylinders, wrapped in aluminum foil, and placed in dichloromethane-rinsedaluminum cans, which were sealed with black plastic tape. Samples were transported by automobile to the sampling site, which was located approximately 10 km south of Indiana University. After samples were collected, they were stored in a freezer in our laboratory until they were extracted and analyzed. For analysis, the PUF plugs were brought to room temperature and injected with known amounts of PCB congeners 30 and 204 (2,4,6-tri- and 2,2',3,4,4',5,6,6'octachlorobiphenyl, respectively) as internal standards. Each plug was then placed in a soxhlet extractor and extracted for 24 h with petroleum ether. The extract was reduced in volume by rotary evaporation to about 1 mL. PCBs were separated from more polar compounds by silica gel column chromatography. The samples were loaded onto a 2 g column of 6 % water deactivated, 100-200 mesh silica gel, and they were eluted with 25 mL of hexane and 5 mL of 10% dichloromethane in hexane. These fractions were combined, solvent exchanged to hexane, and reduced in volume to approximately 1mL. Samples were analyzed in batches of eight. Each batch was accompanied by a field blank, which was generated by placing a clean PUF plug and glass fiber filter in the sampler and leaving them
for 3 days with the sampler pump turned off. The blanks typically contained 50-80 ng of total PCB, which gave a signal-to-blank ratio of between 20:l and 50:l for each congener. A few glass fiber filters were also analyzed, using the same extraction and cleanup procedure as described above. The results of our analyses showed that only 5-10% of the PCBs were adsorbed onto particles even at the lowest atmospheric temperatures. Therefore, we decided to analyze and report only the vapor-phase (PUF plug) PCB concentrations. We analyzed the samples using gas chromatography (GC) with electron capture detection. The GC temperature program was as follows: 40-140 "C at 10 OC/min, 140-230 "C at 0.8 OC/min, 230-280 OC at 10 OC/min, and a 5 min hold at 280 "C. The individual congeners were separated on a 30 m, 250 pm i.d., 0.25 pm film thickness, DB-5 capillary column (J&W Scientific, Folsom, CA) and quantified by the method of Mullin (14), in which a 25: 18:18 mixture of Aroclor 1232, Aroclor 1248, and Aroclor 1262is used to identify congeners and to calculate relative response factors for each peak. These standards were acquired from the U.S. Environmental Protection Agency in Cincinnati, OH. Our method is capable of quantifying approximately 90 peaks; some peaks contain more than one congener. Typically the air samples contained 50-60 congeners. Other experimental details, including quality assurance procedures and results, are given in the previous paper (1).
Results and Discussion ConcentrationTrends over Time. An important goal of this work was to determine whether atmospheric PCB concentrations in Bloomington, IN, had changed in the last 6 years. To achieve this goal, we compared two data sets of PCB concentrations, both measured at Batchelor Middle School in Bloomington. The first set was collected in 1986 and 1987. The second set was collected in 1993. In 1986-1987, Hermanson and Hites (7)found total PCB concentrations between 0.04 and 4.8 ng/m3 over a temperature range of -9.3 to +35 OC. In 1993, we found total PCB concentrations between 0.65 and 2.53 ng/m3 over a temperature range of 12.5 to 26.4 "C. As outlined Environ. Sci. Technoi., Voi. 28, No. 12, 1994 2009
previously, these concentrations are a strong function of atmospheric temperature: As the temperature increases, the atmospheric concentration also increases (7, 10, 11). Presumably, the concentration increase is due to an increase in the partial pressure of the PCBs at their source; this allows more PCBs to volatilize into the atmosphere. This behavior can be described by the Clausius-Clapeyron equation:
wherep is the partial pressure (atm), Tis the atmospheric temperature (K),Hvap is the heat of vaporization (J/mol), and R is the gas constant (8.314 J mol-' K-I)). A plot of In p versus 1 / Tfor each congenerand for total PCBs should be linear with slope of -Hvap/R. Figure 1 shows such a plot for total PCBs. Note that the 1993 data are interspersed with the 1986-1987 data, indicating that the total atmospheric PCB concentrations have not changed in the intervening 6 years. Statistical analysis of these data is appropriate. For a valid analysis, we must compare partial pressures at the same temperature. We selected 300 K. In order to determine the partial pressure for each congener at this temperature, we plotted In p versus 1/T for each of the congeners in each of the two data sets (1986-1987 and 1993),calculated regression lines for each congener in each data set, and calculated the 95% confidence interval for each regression. Using each regression and its 95% confidence limit, we determined, at 300 K, the 95% confidence intervals for the partial pressures of each congener in each data set. These values for both the 19861987 and 1993 data are given in Table 1. Only five congenersdid not have overlapping partial pressure ranges between the two data sets. These are mostly congeners with low concentrationsthat are often difficult to measure. All of the other congeners had partial pressures that overlapped between the 19861987 and 1993 data. Therefore, we conclude that PCB atmospheric partial pressures (and thus concentrations) have remained constant in Bloomington since 1986. The statistical sensitivity of this experiment is not as great as the one in Bermuda, primarily because of the shorter elapsed time (6-7 years instead of 20 years). Using the 1986-1987 maximum of 290 X 10-15 atm and the 1993 minimum of 64 X 10-15 atm for total PCBs (see Table l),we calculate that a rate of decrease of greater than 21% per year would have been detected at the 95% confidence level. This is compared to 3% per year for the Bermuda data. Because they did not differ, we have combined the two data sets for the remainder of this discussion. The average congener profile for air samples from the combined data set is shown in Figure 2. The percentage of each congener relative to the total PCB concentration of each sample was calculated, and these percentages were averaged for all of the samples. The trichloro PCBs are most prevalent, which is not surprising, given their higher vapor pressures relative to the more highly chlorinated PCBs. This profile is similar to that observed in Bermuda ( I ) . This similarity indicates that any change in profile between source and sink must occur close to the source. Note that the set of congeners reported in Figure 2 is not exactly the same as that shown in Figure 1 of the previous paper. These slight differences are a result of small changes in the quantitation methods used in our 2010
Envlron. Scl. Technol., Vol. 28, No. 12, 1994
laboratory between 1986-1987 and 1993. In a few cases, closely eluting congeners could be separated with one method but not with the other. In these cases, the congener concentrations were reported as the sum of the unresolved congeners. A few congeners reported in the Bermuda study were detected in Bloomington in 1993, but they were not reported in Bloomington in 1986-1987. These congeners were present at very low levels, and they were omitted from the Bloomington data set. Heat of Vaporization. From each plot of the natural logarithm of the partial pressure versus inverse temperature we calculated H v a p values. These are given in column 5 of Table 1. From Trouton's rule, we expected to find an increase in Hvap with an increasing degree of chlorination. However, we found no such trend. In fact, several of the hepta and octachloro PCBs had lower Hvapvalues than the less chlorinated PCBs. Of course, highly chlorinated PCBs were often absent from air samples collected at low temperatures, so plots of In p versus 1/T covered a smaller temperature range. This may have of our data is 63 & 16 biased our values. The mean Hvap kJ/mol. We can compare our values with those of Hoff et al. (151,who collected air samples in Egbert, Ontario, over a wide temperature range using techniques similar to ours. Although Hoff does not explicitly report Hvap,we can estimate it from his Table 11,in which he reports the slopes of plots of the common logarithm of the concentrations versus inverse temperature. We multiplied his slope values by 2.303R to get Hvap; these values are given in Table 1, column 6. The mean of his values is 74 f 10 kJ/mol. Strictly speaking, Hoff s slope does not give a true Hvap, since the plot should be of the natural logarithm of the partial pressure, not of the concentration. However, the conversion between concentration and partial pressure is a small correction, which would not significantly change the slope. We compared our Hvap data with Hoff's using a t-test of the pairwise differences between the two values. The t value was 1.36, which is not significant. This good agreement between these two sets of H v a p data demonstrates the precision of this method. We also compared our data with those of Falconer and Bidleman (161,who determined the parameters necessary to calculate the vapor pressure of each PCB congener as a function of temperature from laboratory-based GC experiments. Using these parameters, we calculated H v a p for each congener. These values are shown in column 7 of Table 1. Although many of our values are comparable to those of Falconer and Bidleman (161,especially for the less-chlorinated PCBs, most of our values are significantly lower. These differences are most likely caused by the conditions under which the two sets of values were determined. It is easier to determine the physical properties of a compound in a controlled laboratory setting than in the ambient atmosphere. Processes such as deposition between the source and the sampling site can complicate the relationship between temperature and concentration. This is especially true for compounds present at low concentrations, where removal processes can force the concentration below the detection limit. Atmospheric Residence Times. The atmospheric residence time of a PCB congener is the time it spends in the atmosphere before being either degraded or removed to another environmentalcompartment. We can calculate this residence time using a method described by Junge
Table 1. PCB Congener Number, Number of Chlorines, Atmospheric Partial Pressure Ranges at 300 K (95% Confidence Limits) for 1986-1987 and 1993, Heats of Vaporization, and Residence Times PCB congener
no. of C1
18 + 17 27 32 + 16 25 31 + 28 33 22 45 46 52 49 48 47 44 42 64 100 63O 74 70 + 76 66 95 91 56 + 60 92 + 84 101a 83 97 87 85O 110 151 135 + 144 149" 153 + 132 141 137 176" 163 138 178 175 187 + 182 183 185 174 177 171 + 202 180 170 + 190 201 203 total PCBs average std dev
3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 5 4 4 4 4 5 5 4 5 5 5 5 5 5 5 6 6 6 6 6 6 6 7 7 7 7 7 7 7 8 7 7 8 8
+
+ +
a
partial pressure (atm x 10'9 1993 1986-1987 1.4-18 0.43-1.5 3.5-16 0.36-3.8 20-62 4.3-15 2.6-11 0.10-1.2 0.13-0.67 4.7-14 3.2-7.7 1.3-3.4 2.8-8.8 1.1-3.5 1.3-4.1 0.41-1.2 0.36-0.67 1.4-3.8 3.9-12 2.6-10 1.5-4.3 0.59-1.5 2.3-11 1.1-11 0.90-5.0 0.15-0.43 0.61-1.8 0.78-3.5 0.73-3.5 0.79-6.5 0.14-0.98 0.26-2.4 1.3-4.3 1.0-3.8 0.09-0.66 0.10-0.31 0.63-3.8 0.11-0.32 0.04-0.23 0.23-1.0 0.09-0.63 0.03-0.10 0.06-0.38 0.07-0.28 0.09-0.23 0.06-0.73 0.05-0.63 0.07-0.22 0.03-0.47 110-290
3.4-16 0.23-0.98 3.8-13 0.45-1.9 11-32 4.3-13 3.9-12 0.90-2.1 0.20-1.0 2.9-7.4 1.9-5.1 1.5-5.6 3.0-7.7 1.8-5.2 1.3-4.7 0.17-4.1 0.02-0.24 0.87-2.5 2.0-6.2 1.5-4.7 1.5-4.4 0.28-0.91 1.1-4.2 0.84-5.6 6.7-15 0.04-0.20 0.23-1.1 0.68-2.4 0.17-0.57 1.4-4.2 0.20-0.44 0.17-0.36 0.31-0.90 0.38-1.5 0.04-0.16 0.01-0.02 0.27-2.0 0.03-0.13 0.04-0.13 0.03-0.34 0.03-0.12 0.02-0.05 0.04-0.18 0.02-0.09 0.02-0.09 0.05-0.19 0.01-0.78 0.04-0.14 0.04-0.16 64-163
heat of vaporization (kJ/mol) ref 16 this work ref 15 65 48 68 23 70 72 70 44 69 77 72 63 76 79 81 53 26 67 70 69 72 66 67 67 78 60 73 75 28 98 65 79 74 67 83 66 76 44 46 49 51 61 57 58 58 47 65 47 31 65* 63 16
67-93' 94
72 72 76
64
65
61 72
76
74 10
75 75 75 78 78 78 78 79 79 81 81 81 81 81 81 84 84 85,84 83 84 84 84 87,84 86 86 86 87 87 87 90 90 90 91,90 92 92,88 92 95 95 94 95 95 95 95 96,93 96 98 93 100 86 7
residence time (days) 56 67 72 42 67 73 64 64 59 60 78 59 82 71 68 64 47 52 51 44 70 58 41 39 52 48 46 35 43 33 17 29 31 36 16 33 25 40 51 32 34 48 35 44 51 33 25 49 48 756 49 16
Ranges do not overlap at 300 K. b Not included in the mean and standard deviation. Congener 28,67 kJ/mol; congener 31,93 kJ/mol.
( I 7). This method requires the mean and relative standard deviation of atmospheric concentrations for samples collected over at least 1 year. The residence time is given by 7
= 0.14(uJ1
where 7 is the atmospheric residence time (in years) and urnis the relative standard deviation of the concentration measurements. Details on the derivation and limitations of this method are given in the previous paper (1). Our calculated residence times are shown in Table 1, column 8. These values have a mean of 49 f 16 days, which is similar to the range of 45-67 days reported by Bidleman
et al. (18)and to the range of 40-75 days reported by us for atmospheric PCBs measured at Bermuda (I). Unlike our data for Bermuda, the residence times at Bloomington do not vary systematicallywith level of PCB cklorination. Atmospheric Flux. As in Bermuda (I),we can use the known atmospheric concentrations and residence times to calculate the flux of PCBs into the atmosphere. Because Bloomington contains several PCB sources, however, we must modify the calculation we performed in the previous paper (1). We cannot simply multiply the atmospheric concentration of PCBs in Bloomington by the volume of the troposphere and divide by the tropospheric residence time and surface area of the earth because the concentrations in Bloomington are higher than those found in most Environ. Sci. Technol., Vol. 28, No. 12, 1994 2011
25
4
20 C
0 .c C
15
8 r: 0 0 -m c
3 10
rc
0
s 5
0
Congener Flgure 2. Average PCB congener profile for the combined data sets.
of the troposphere. However,by knowing the atmospheric concentrations of PCBs in Bloomington and in remote regions (such as Bermuda), we can calculate the ratio of the fluxes in Bermuda and Bloomington using the ratio of the atmospheric concentrations. We have shown that the tropospheric residence times are similar in both locations; thus, we can find the PCB flux at Bloomington by taking the flux at Bermuda, multiplying by the concentration at Bloomington, and dividing by the concentration at Bermuda. If the Bermuda flux is 13 pg m-2 year-l, the Bermuda concentration is 0.38 ng/m3, and the average Bloomington concentration is 1.95 ng/m3, then the average flux of PCBs at Bloomington is 67 pg m-2 year-'. Due to the temperature effects discussed earlier, atmospheric PCB concentrations at Bloomington change seasonally, but those at Bermuda do not. Using the maximum and minimum values of Bloomington's PCB concentrations, we calculate a flux range of 16-160 pg m-2 year-l. Because Bloomington is a source of PCBs, we believe that these compounds volatilize into the atmosphere and are transported to distant sinks. There is another way to estimate the flux of PCBs from Bloomington into the atmosphere. This method depends upon the existence of a PCB concentration gradient between the boundary layer (the kilometer of the atmosphere closest to the earth's surface) and the free troposphere (the next 9 km of the atmosphere) (19). We can calculate the flux of PCBs away from Bloomington if we know the concentrations in the boundary layer and in the free troposphere above Bloomington, as well as the resistances to transport. The flux is given by
F
+ (CB - CT)/(ra+ rb + rc)
where F is the flux, CB is the PCB concentration in the 2012
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boundary layer, CT is the PCB concentration in the free troposphere, ra is the aerodynamic resistance, rb is the boundary layer resistance, and rc is the canopy resistance (20). For CB we used our measured value of 1.95 ng/m3. Because of the sources in Bloomington and because time is required to mix air from the boundary layer and free troposphere, the boundary layer concentrations are higher than the free troposphere concentrations. Therefore, we assigned CT a value of 0.8 ng/m3, a value taken as the Great Lakes background determined by ManchesterNeesvig and Andren (10) at a remote site in northern Wisconsin at 25 "C. The concentration gradient drives the flow of PCBs out of the boundary layer; resistance terms control the rate at which PCBs are transported. The aerodynamicresistance, ra,is the resistance to momentum transfer and is inversely related to wind speed (20, 21). From the average wind speed in Bloomington, we have estimated values of ra between 10 and 35 s/m. The boundary layer resistance, rb, is inversely related to the friction velocity. [Friction velocity is the square root of the product of the horizontal and vertical velocities (20)l. The values of rb range from 10 to 20 s/m. The canopy resistance, rc, is the inverse of the deposition velocity. Estimates of the deposition velocity of PCBs range from 0.16 (22) to 0.5 cm/s (23). These give rcvalues of 625 and 200 s/m, respectively. Using the range of values for each parameter, we calculate a flux of 53-165 pg m-2 year-1. We must emphasize that these are maximum values for the flux of PCBs from Bloomington. This flux was calculated using concentration values at 25 "C; at lower temperatures, the concentration gradient between the boundary layer and the free troposphere is not as large, so the flux will be reduced.
Our first method of calculating the flux gave values of 16-160 pg m-2 year-1. These values take into account the PCB concentration changes as a function of temperature, with lower fluxes occurring a t lower temperatures. Our second method of calculating the flux gave maximum values (at 25 "C) of 53-165 pg m-2 year-l. Although the total range of 16-165 pg m-2year-1 is large, it is logical that fluxes would vary seasonally and that more PCBs would volatilize a t high temperatures. This atmospheric flux is higher than those reported in several areas, probably because Bloomington is surrounded by major PCB sources. For example, in Bermuda, we found an atmospheric flux of 13 pg m-2 year-l (1);in northern Wisconsin, Swackhamer and Armstrong (24)found a flux of 1-3 pg m-2 year-l, and for Lake Michigan, Hermanson et al. (25)found a flux of 10 pg m-2 year-l. Our values are similar to the range of 4.7-470 pg m-2 year-' reported by Achman et al. (12)for the net flux from Green Bay, a contaminated area. However, our fluxes in Bloomington are lower than those reported by some researchers for other contaminated sites. For example, in Chicago, Holsen et al. (26)found a flux of 1500 pg m-2year-l (in dry deposition only); for the South Bay of the North Sea, Thome et al. (27) estimated a flux of 300 pg m-2 year-l (calculated vaporization from the water). Taken in this context, our values are reasonable for a contaminated, suburban site such as Bloomington. Acknowledgments
We thank the Monroe County Community School Corp. for allowing us to locate our air sampler on the roof of Batchelor Middle School. The National Institute for GlobalEnvironmental Change and the U.S. Environmental Protection Agency (Grant R818847) provided support. Literature Cited Panshin, S. Y.; Hites, R. A. Environ. Sci. Technol. 1994, preceding paper in this issue. Eisenreich, S. J.;Capel, P. D.; Robbins, J. A,; Bourbonniere, R. Environ. Sci. Technol. 1989,23, 1116-1126. Hesselberg, R. J.; Hickey, J. P.; Nortrup, D. A.; Willford, W. A. J. Great Lakes Res. 1990, 16, 121-129. Muir, D. C. G.; Norstrom, R. J.; Simon, M. Environ. Sci. Technol. 1988,22, 1071-1079. Norstrom, R. J.; Simon, M.; Muir, D. C. G.; Schweinsburg, R. E. Environ. Sci. Technol. 1988,22, 1063-1071. Irwin, R. J.; Lageroos, D. Toxic Air Pollution in the Great Lakes Basin: A Call for Action; Sierra Club: Madison, WI,
1988; pp 1-25. Hermanson, M. H.; Hites, R. A. Environ. Sci. Technol. 1989, 23, 1253-1258. Westinghouse Electric Corp. Application for an Air Quality Permit to Construct a Proposed Bloomington Incinerator Facility, 1986. Eisenreich, S.J.; Looney, B. B.; Thornton, J. D. Environ. Sci. Technol. 1981, 15, 30-38. Manchester-Neesvig, J. B.; Andren, A. W. Environ. Sci. Technol. 1989,23, 1138-1148. Hoff, R. M.; Muir, D. C. G.; Grift, N. P. Enuiron. Sci. Technol. 1992,26, 266-275. Achman, D. R.; Hornbuckle, K. C.; Eisenreich, S. J. Environ. Sci. Technol. 1993, 27, 75-87. Hornbuckle, K. C.; Achman, D. R.; Eisenreich, S.J. Environ. Sci. Technol. 1993, 27, 87-98. Mullin, M. D. PCB Workshop at the US.EPA Large Lakes Research Station; Environmental Protection Agency Grosse Ile, MI, 1985. Hoff, R. M.; Muir, D. C. G.; Grift, N. P. Enuiron. Sci. Technol. 1992,26,276-283. Falconer, R. L.; Bidleman, T. F. Atmos. Environ,. 1994,28, 547-554. Junge, C. E. Tellus 1974,4, 477-488. Bidleman, T. F.;Christensen, E. J.; Billings, W. N.; Leonard, R. J. Mar. Res. 1981, 39, 443-464. Ahrens, C. D. Meteorology Today: An Introduction to Weather, Climate, and the Environment; West Publishing: St. Paul, MN, 1991. Monteith, J. L.; Unsworth, M. H. Principles of Environmental Physics, 2nd ed.; Edward Arnold: New York, 1990. Oke, T. R. Boundary Layer Climates, 2nd ed.; Methuen Publishers: New York, 1987. Swackhamer, D. L.; McVeety, B. D.; Hites, R. A. Environ. Sci. Technol. 1988, 22, 664-672. Andren, A. W. In Physical Behavior of PCBs in the Great Lakes;Mackay, D., Patterson, S.,Eisenreich,S. J., Simmons, M. S., Eds.; Ann Arbor Science: Ann Arbor, MI, 1983. Swackhamer,D. L.; Armstrong, D. E. Environ. Sci. Technol. 1986,20,879-883. Hermanson, M. H.; Christensen, E. R.; Buser, D. J.; Chen, L.-M. J. Great Lakes Res. 1991, 17, 94-108. Holsen, T. M.; Noll, K. E.; Liu, S.-P.; Lee, W.-J. Environ. Sci. Technol. 1991,25, 1075-1081. Thome, J.-P.;Hugla, J.-L.; Joiris, C. Bull. SOC.R. Sci. Liege 1992, 61, 99-111.
Received for review January 6, 1994. Revised manuscript received August 3, 1994. Accepted August 5, 1994." ~~
*Abstract published in Advance ACS Abstracts,September 15, 1994.
Environ. Sci. Technol., Vol. 28, No. 12, 1994 2013
