Air concentrations of organochlorine insecticides and polychlorinated biphenyls over Green Bay, WI, and the four lower Great Lakes

ENVIRONMENTAL POLLUTION

Environmental Pollution 101 (1998) 391±399

Air concentrations of organochlorine insecticides and polychlorinated biphenyls over Green Bay, WI, and the four lower Great Lakes L.L. McConnell a,*, T.F. Bidleman b, W.E. Cotham c, M.D. Walla c a

US Department of Agriculture, Agricultural Research Service, Building 007, Room 225, Beltsville, MD 20705, USA b Atmospheric Environment Service, ARQP, 4905 Du€erin Street, Downsview, Ontario M3H 5T4 Canada c Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, USA Received 10 September 1997; accepted 21 January 1998

Abstract Organochlorine pesticides and polychlorinated biphenyls were determined in high volume air samples collected in Green Bay from the University of Wisconsin (1989), and from shipboard over the four lower Great Lakes (1990). Average concentrations of chlordane, DDT, DDE, toxaphene and PCBs in Green Bay were 35, 8.7, 15, 59 and 330 pg mÿ3, respectively. Air concentrations of the pesticides were positively correlated to each other (R2=0.896±0.997), and analysis of back trajectory data from Green Bay showed that higher atmospheric concentrations of organochlorine insecticides were associated with air masses originating in southern USA. Average concentrations from the Great Lakes were: chlordane, 187 pg mÿ3; DDT, 38 pg mÿ3; pg mÿ3; DDE, 59 pg mÿ3; toxaphene, 33 pg mÿ3; and PCBs, 385 pg mÿ3. Higher air concentrations of PCBs were found in areas of industrial and urban development. There was no strong positive correlation of concentration values between any pesticides, with the exception of the chlordane isomers, or between any pesticide and PCB from the Great Lakes cruise. Results from 5-day air mass back trajectory data suggest that, at the time of the cruise, atmospheric sources of organochlorines were not long-range transport from southern USA, but local or regional volatilization. # 1998 Elsevier Science Ltd. All rights reserved. Keywords: Great Lakes; Atmosphere; Pesticides; PCBS; Green Bay

1. Introduction Organochlorine pesticides such as chlordane, DDT, toxaphene, and industrial organochlorines, such as PCBs, were heavily used during the 1950s through the 1970s and were phased out of use in USA and Canada due to toxic e€ects on wildlife. These compounds are resistant to degradation in the environment, have a tendency to bioaccumulate in animals and are moderately volatile. Continuing sources of these compounds to the Great Lakes region include volatilization from previously contaminated soils in USA and from current use in other countries followed by atmospheric transport and deposition. Previous research has shown that atmospheric inputs of organochlorines from regional and global sources have been important sources of * Corresponding author. Tel.: +1-301-504-6298; fax: +1-301-5045048; e-mail: [email protected] 0269-7491/98/$19.00 # 1998 Elsevier Science Ltd. All rights reserved. PII: S0269 -7 491(98)00030 -X

these compounds to the Great Lakes (Strachan and Eisenreich, 1988; Eisenreich and Strachan, 1992). However, several recent studies have shown that the Great Lakes are losing these compounds through volatilization (Swackhamer and Armstrong, 1986; Baker and Eisenreich, 1990; Achman et al., 1993; Hornbuckle et al., 1993, 1995; Jeremiason et al., 1994; Ho€ et al., 1996; Ridal et al., 1996, 1997). While the importance of atmospheric pollutant cycles to the Great Lakes has been known for many years, very few measurements of these compounds have been made in air directly over the lake surface. Here we report atmospheric measurements of organochlorines from a land station at Green Bay, WI, and on a cruise of the four lower Great Lakes and compare them to results from the integrated atmospheric deposition network (IADN) network and other studies. Air mass back trajectory data from some sample collection periods are also presented as a means of estimating possible source regions.

392

L.L. McConnell et al./Environmental Pollution 101 (1998) 391±399

2. Experimental 2.1. Sample collection High volume air samples were collected at a site on the campus of the University of Wisconsin, Green Bay during 24±29 February 1988, 4±8 June 1989, and from the four lower Great Lakes and Lake St. Clair during 2±17 August 1990. The Great Lakes cruise was conducted aboard the US EPAR/V Roger R. Simons, which originated from the Great Lakes Protection Oce in Milwaukee, WI, and terminated in Detroit, MI. The lakes were sampled in the following order: Michigan, Huron, Erie, Ontario, Erie. The locations of the collection sites and their designations (GL1±GL12) are shown in Fig. 1. Samples GL13±GL15 are not shown in Fig. 1. These were collected during the return trip across Lakes Ontario and Erie. GL13 overlaps the track for GL12, GL14 overlaps GL11, and GL15 overlaps GL10. The collection data for Green Bay and the Great Lakes are given in Table 1.

Green Bay air samples were collected using an aluminum ®lterhead containing a glass-®ber ®lter (GFF) (2025 cm) followed by two 7.8-cm diameter7.5-cm thick polyurethane foam (PUF) plugs. The ®lterhead was attached to a Rotron DR-313 brushless pump by a

Fig. 1. Air sample collection sites for the Green Bay and Great Lakes cruise. Numbers correspond to the Great Lakes air sample of the same number, 1=GL1, 2=GL2 etc ... as listed in Table 1.

Table 1 Air sample collection data for Green Bay and Great Lakes Air temperature ( C)

Volume (m3)

Date

Location

361 256 389 291 342 342 342 298 304

24±25 25 25±26 26 26±27 27 27±28 28 29

Univ. of WIÐGB " " " " " " " "

Green Bay, June 1989b GS1 GS2 GS3 GS4 GS5 GS6

1053 888 931 1183 799 1487

3±4 4±5 5±6 6±7 7±8 8±10

Univ. of WIÐGB " " " " "

11±26 11±26 13±26 12±26 12±26 17±23

Great Lakes, August 1990c GL1 GL2 GL3 GL4 GL5 GL6 GL7 GL8 GL9 GL10 GL11 GL12 GL13 GL14 GL15

335 422 437 331 411 229 354 345 307 347 370 390 321 414 394

2 3 3±4 5 5±6 6 6±7 7±8 8±9 9 9±10 11±12 13±14 15±16 16±17

S. Michigan C. Michigan N. Michigan N. Huron C. Huron S. Huron Lake St. Clair W. Erie C. Erie C. Erie E. Erie Ontario Ontario E. Erie C. Erie

21 19±20 18±19 17±19 17±19 17±19 19 21±22 21±22 21 20±23 20±23 19±20 22±23 22±23

Sample name Green Bay, February 1988a GW1 GW2 GW3 GW4 GW5 GW6 GW7 GW8 GW9

a b c

Collection data from Cotham and Bidleman (1995a), mean temperature. Temperature data from K.C. Hornbuckle (personal communication), temperature range. Temperature data from P. Bertram (personal communication).

ÿ12.2 ÿ8.2 ÿ7.2 2.9 ÿ1.9 ÿ1.1 ÿ4.0 1.7 ÿ3.0

L.L. McConnell et al./Environmental Pollution 101 (1998) 391±399

393

determined by GC-negative ion mass spectrometry (GC-NIMS) using a method described by Patton et al. (1989). CHB and chlordane levels in winter samples from Green Bay were below the limit of detection (LOD); therefore, extracts from samples GW1 and GW2, and extracts from samples GW6 and GW7 were combined and analyzed by GC-NIMS to increase detectability. Only results from these combined extracts are presented in this report. A further discussion of results of polycyclic aromatic hydrocarbon and PCB results from these winter samples can be found in a separate report (Cotham and Bidleman, 1995a). In the case of the Great Lakes cruise samples, all compounds were analyzed by GC-ECD with the exception of the CHBs. Extracts from each lake were combined and concentrated for analysis of CHBs by GC-NIMS. The combined extract for Lake Ontario also includes the ®nal two air samples collected over Lake Erie. Blank PUF were extracted and analyzed for target analytes. Blank concentrations and calculated limits of detection are listed in Table 2. PCB congener-speci®c blanks ranged from 0.050‹0.010 to 2.3‹0.19 ng for Congeners 180 and 8, respectively (McConnell, 1992), and the PCB blank listed in Table 2 is the sum of the congener values. Congener-speci®c blanks of CHBs were not determined. Only one total CHB blank was determined, thus a limit of detection for this compound group was not readily determined. However, the CHB blank of 2.0 pg mÿ3 corresponds to only 14% of the lowest CHB air concentration. The limit of detection was de®ned as the average blank value plus three standard deviations (x +3 SD). Samples below the limit of detection were eliminated and the remaining were corrected for average blank values. Recoveries of organochlorine pesticides from spiked, unused PUF plugs cartridges were done to check for losses during transport, storage, and work-up (Table 2). Recovery experiments for PCB and CBB congeners were not conducted, however, other recovery experiments using these methods have resulted in average recoveries of 89‹13% for PCBs (Cotham and

3-m piece of silicone rubber hose. The pump was operated at 0.5 m3 minÿ1. Air samples were collected for 9±13 h in February 1988 (volumes, 256±389 m3) and for 30±50 h in June 1989 (volumes, 888±1487 m3). The same type of GFF/PUF sample train and pump were used during the Great Lakes cruise, except that the GFF diameter was only 10 cm and the ¯ow rate was 0.4 m3 minÿ1 for 10±18 h (volumes, 229±437 m3). Flow rates were determined by measuring the pressure drop behind the vapor traps with a Magnehelic gauge. This pressure drop was related to volumetric ¯ow using an ori®ce calibrator. PUF plugs were pre-cleaned by Soxhlet extraction using methods previously described (Billings and Bidleman, 1983). PUF plugs were stored in glass jars with Te¯on-lined caps. GFFs were baked at 400 C overnight in a mu‚e furnace to remove organic material, and wrapped in aluminum foil. PUF plugs and ®lters were kept at ÿ10 C after sampling until extraction. 2.2. Analytical methods and quality control PUF plugs and GFFs were Soxhlet extracted for at least 8 h with chromatographic grade solvent (Mallinckrodt). PUF plugs were extracted with petroleum ether and GFFs were extracted with dichloromethane. Extracts were reduced to 1 ml using rotary evaporation followed by a nitrogen blow-down. Sample extracts were fractionated by silicic acid chromatography into two portions to separate the PCBs and p,p0 DDE from the other organochlorines, as described earlier (Bidleman et al., 1987). The fractions were reduced into iso-octane and treated with 0.5 ml 18 M sulfuric acid for clean-up. A survey of GFF extracts showed traces of some analytes, but all were below the limits of detection; therefore, only gas-phase concentrations are listed in this report. The PUF extracts were analyzed for 41 PCB congeners and most organochlorine pesticides using capillary GC-electron capture detection (GC-ECD) as described by Ngabe and Bidleman (1992). Chlorinated bornanes (CHBs, e.g. toxaphene) and chlordanes were Table 2 Polyurethane foam blank, limit of detection, and spike recovery results Compound

Mean blank ‹SD (ng)

No. Blank experiments

Limit of detection (ng)

Mean spike recovery ‹SD (%)

No. of spike recovery experiments

a-HCH g-HCH g-Chlordane a-Chlordane trans-Nonachlor 4,40 -DDE 4,40 -DDT CHB PCBs

0.041‹0.013 0.21‹0.16 0.43‹0.38 0.38‹0.46 0.16‹0.25 0.32‹0.37 0.57‹0.54 0.7 16‹10

4 4 25 25 23 3 25 1 4

0.070 0.69 1.6 1.8 0.91 1.4 2.2 NAa 46

81‹7 84‹11 87 88 84 67 105 NA NA

5 5 2 2 2 2 2 NA NA

a

NA=not analyzed.

394

L.L. McConnell et al./Environmental Pollution 101 (1998) 391±399

Bidleman, 1995b) and 103‹21% for CHBs (Bidleman et al., 1995). Breakthrough for the PUF sampler was checked by separately analysing front and back plugs. Very little of the organochlorine pesticides were found on the back plug samples. Five-day air mass back trajectories at the 925 mb (approximately 1000 m height) levels were obtained from the Atmospheric Environment Service (Canada) for the air sample collection dates listed in Table 1. 3. Results and discussion 3.1. Air mass back trajectory analysis Comparisons of 5-day air mass back trajectories and air concentrations led to a hypothesis that sources to the south of the Great Lakes are contributing pesticides to the airshed (Ho€ et al., 1992a). A similar approach was used in this study in an attempt to discern possible source regions for our target analytes. Fig. 2 illustrates the change in total organochlorine pesticide concentration over the period of 4±10 June 1989 in Green Bay. The dominant transport directions are designated for each air sample, and representative trajectory patterns for 4 and 8 June are shown in Fig. 3. Higher concentrations of the chlordanes, DDT, DDE and CHBs were found on the two days when the air over Green Bay arrived from the W-SW or S-SW. This supports observations and models which show that pulses of air containing elevated concentrations of organochlorines (OCs) enter the Great Lakes airshed and contribute to overall higher air concentrations during the summer months (Voldner and Schroeder, 1989; Ho€ et al., 1992a). Other evidence that air concentrations during this time period were governed by long-range transport

Fig. 2. Sample by sample comparison of total chlorinated pesticide concentration measured in Green Bay, June 1989 (pg mÿ3). The direction of origination of the 925 mb 5-day air mass back trajectory is listed for each sample.

rather than various local sources is the high degree of positive correlation (r2=0.90±0.99) between the CHBs, DDTs and chlordanes. It should be noted that the temperature range over the sampling period remained relatively constant (Table 1), therefore the positive correlation between concentrations cannot be attributed to temperature changes. Although some toxaphene was used in northern states, over 80% was applied in the southern `cotton belt' and nearby states (Voldner and Schroeder, 1989). PCB concentrations during this same time period did not correlate well with pesticide concentrations. Back trajectory analysis data of the time period during the Great Lakes cruise revealed that air masses generally originated in northern Canada and moved directly over the Great Lakes, or the air mass originated

Fig. 3. Five-day air mass back trajectory for a) 4 June and b) 8 June 1989.

L.L. McConnell et al./Environmental Pollution 101 (1998) 391±399

395

average PCB concentrations at Green Bay were 128‹62 pg mÿ3 and 330‹230 pg mÿ3 in February 1988 and June 1989, respectively. Our summer Green Bay results compare well with other measurements from the same location during the summer and fall of 1989±91 (Hornbuckle et al., 1993), where the average PCB concentration was 338‹248 pg mÿ3 (Table 4). Concentrations of PCBs over Lake Michigan during the August 1990 cruise ranged from 440 pg mÿ3 in the southern and mid region of the lake (GL1 and GL2) to 170 pg mÿ3 in the northern part of the Lake (GL3). Air concentrations of PCBs over Lake Huron were consistently lower than the other lakes and ranged from 160 to 200 pg mÿ3. Results from a single air sample collected while travelling through the St. Clair river, Lake St. Clair and the Detroit River (410 pg mÿ3) were similar to those found in southern Lake Michigan. The highest PCB concentrations were found in the easternand western-most regions of Lake Erie, with 1300 pg mÿ3 observed near Detroit and 1100 pg mÿ3 observed near Bu€alo. Levels in the center of Lake Erie ranged from 120 to 260 pg mÿ3. Total PCBs over western and central Lake Ontario were higher than Lake Huron, but lower than Lake Michigan (240±370 pg mÿ3). Results from other studies of PCB concentrations in air in the Great Lakes region are given in Table 4. The

in the north and cycled around the US Midwest before moving over the Great Lakes. Attempts to correlate pesticide compound measurements with each other also showed little or no positive relationship, with the exception of a correlation between the chlordane isomers (r2=0.44±0.48). There was only weak or no positive correlation between pesticides and PCB concentrations. However, this type of correlation is made more dicult as the location of sample collection was continually changing. With the exception of CHBs, higher concentrations of all the organochlorine pesticides were found during the summer cruise compared to winter and late spring results at Green Bay. This suggests that during the warm summer months release of these compounds from local contamination of soils, sediments or surface waters may be an important source within the Great Lakes region. Direct con®rmation of local volatilization from surface waters could not be con®rmed as only low volume water samples were collected during this study (McConnell et al., 1993). 3.2. Air concentrations 3.2.1. Polychlorinated biphenyls PCB air concentrations measured at Green Bay and during the Great Lakes cruise are listed in Table 3. The

Table 3 Air concentrations (pg mÿ3) of chlordanes, DDTs, and chlorinated bornanes and PCBs over Green Bay and over the four lower Great Lakes g Chlordane

a Chlordane

transNonachlor

cisNonachlor

4,40 DDE

4,40 DDT

Chlorinated bornanes

PCB

1.5 7.5

1.2 5.3

0.62 4.4

0.06 0.22

NDb ND

ND ND

15 26

130±210 60±111

7.8 5.0 8.3 19 23 8.2 12‹7.3

7.8 5.5 8.7 21 24 8.2 12‹7.9

5.3 3.5 7.0 15 22 6.3 10‹7.7

0.53 0.35 0.64 1.2 2.1 0.61 0.91‹0.65

50 27 45 85 109 38 59‹31

231 100 220 150 470 560 330‹230

Great Lakes, August 1991d Lake MichiganÐGL1±3 Lake HuronÐGL4±6 Lake St. ClairÐGL7 Lake ErieÐGL8±11, GL14±15

73±120 17±43 52 28±77

56±97 18±45 58 39±126

44±82 19±38 32 25±101

NAe NA NA NA

19±61 4.3 123 6.7±127

2.6±39 7.6±25 294 53±32

65 14 NA 16

Lake OntarioÐGL12±13

77±103

82±83

53±56

NA

59±106

16±45

38

440,440,170 200,160,190 410 1300,120,180, 200,1100,260 370,240

Location Green Bay, February 1988a GW1+GW2 GW6+GW7 Green Bay, June 1989c GS1 GS2 GS3 GS4 GS5 GS6 Mean‹SD

10 6.0 NA 2.3 NA 8.9 28 12 10 15 11 5.2 15‹8.8 8.7‹5.6

a Extracts from GW1 and GW2 were combined and GW6 and GW7 were combined and analyzed by GC-NIMS to observe quanti®able levels of chlordanes and chlorinated bornanes. DDT and DDE were analyzed by GC-ECD and were below the LOD in all samples. PCBs listed are the separate concentration values from the combined extracts. b ND=not detected. c Chlordanes and chlorinated bornanes were analyzed by GC-NIMS, DDT and DDE were analyzed by GC-ECD. d Chlordanes, DDT and DDE analyzed by GC-ECD. Chlorinated bornanes were determined by combining extracts from each lake followed by analysis by GC-NIMS. e NA=not analyzed.

396

L.L. McConnell et al./Environmental Pollution 101 (1998) 391±399

Table 4 Comparison of air concentration (pg/mÿ3) measurements of organochlorine pesticides and PCBs from the Great Lakes region Location

PCBs Chlordanes

DDT

DDE

CHBs

Egbert, Ontario, Canada

207‹218

40‹27

20‹16 53‹42 26‹32

Eagle Harbor, MI (Lake Superior) Sleeping Bear, MI (Lake Michigan) Sturgeon Point, NY (Lake Erie)

128‹12 160‹10 315‹20

8.0‹6.7 27‹30 40‹41

2.4‹1.8 2.8‹1.8 7.8‹14 13‹15 16‹14 28‹22

Lake Superior July 1988 August 1990 May 1992 Green Bay, Lake Michigan Southern Bay Northern Bay 3 land-based stations University of Wisconsin, Green Bay, February 1988 University of Wisconsin, Green Bay, June 1989 Lakes Michigan, Huron, Erie and Ontario, August 1991 a b

377‹88 267‹230 302‹69

NA NA NA

NAa

NA

NA

NA

670±2200 160±520 70±760 128‹62

NA

NA

NA

NA

14±17.4

NDb

ND

16±26

330‹230

35‹23

8.7‹5.6 15‹8.8 59‹31

385‹349

187‹80

38‹72 59‹45 33‹24

Project description and reference 7/88±6/89, sampling 1 day in 6, values represent average of monthly mean values (Ho€ et al., 1992b) IADN project: PCB concentrations represent 1991±95, sampling 1 day in 12 (Hillery et al., 1997), other values represent only 1/93±12/93, annual average (Sweet et al., 1996) Over-water measurements from central, eastern and western Superior (Hornbuckle et al., 1994). 1989±91, summer and fall measurements, over water and over land stations (Hornbuckle et al., 1993). (This study)

Average of 15 measurements over the four lakes (This study)

NA=not analyzed. ND=not detected.

overall average Great Lakes PCB concentration of 385 pg mÿ3 from this study is remarkably similar to overwater, spring/summer measurements from Lake Superior (averages range from 267 to 377 pg mÿ3) (Hornbuckle et al., 1994). However, our results are generally higher than annual average values from Ho€ et al. (1992b), 207 pg mÿ3, and from the three IADN stations, 128, 160 and 315 pg mÿ3 from Lakes Superior, Michigan, and Erie, respectively (Hillery et al., 1997). The stations used in the Ho€ et al. (1992b) and IADN studies (Sweet et al., 1996) are located away from urban, industrial areas, and represent concentrations from all months of the year. Fig. 4 is a comparison of the average PCB relative homolog pro®les observed over Green Bay in both February, 1988 and June, 1989 versus the overall average from the Great Lakes cruise. Results from Green Bay show the relative composition of the PCB congeners was clearly dominated by the tri- and tetra-chlorinated biphenyls with these two homologs representing approximately 70±85% of the total. This type of pattern has been observed by other researchers in air samples collected in Green Bay (Hornbuckle et al., 1993). The pattern observed from the Great Lakes samples represented a shift towards the higher molecular weight congeners with the tri-, tetra- and penta-chlorinated biphenyls contributing 25±35% each to the total concentration. This shift in congener pro®le may be more a result of increased air temperatures during the August cruise compared with the winter and spring temperatures of the Green Bay samples rather than a di€erence in sources. Results from annual monitoring of PCBs in air from Egbert, Ontario by Ho€ et al. (1992b) showed

both the highest PCB concentrations of the year in July as well as a shift in congener pro®le to the higher molecular weight PCBs. It may be that temperature conditions present during the winter and early spring do not allow the heavier PCBs to volatilize e€ectively, whereas the higher temperature conditions found in August may increase the vapor phase concentrations of these lower vapor pressure compounds. 3.2.2. Organochlorine insecticides 3.2.2.1. Chlordane. Samples in this study were analyzed for the more abundant components of the technical chlordane mixture, a- and g- chlordane as well as trans-

Fig. 4. Average PCB homolog percent composition comparison of Green Bay in February 1988 and June 1989, and from the Great Lakes, August 1990.

L.L. McConnell et al./Environmental Pollution 101 (1998) 391±399

and cis-nonachlor (Table 3). Chlordane component concentrations were lowest on the coldest days in February 1988. Results for GW1+2 (chlordane= 3.4 pg mÿ3) when the median temperature was ÿ10 C were 5 times lower than GW7+8 (chlordane= 17 pg mÿ3) collected when the median temperature was ÿ1 C (Table 4). GW1+2 is similar to chlordane levels observed in remote regions such as the Bering and Chukchi Seas, 8.6 pg mÿ3; or in the Canadian Arctic: 4.0±11 pg mÿ3 (Ho€ and Chan, 1986; Patton et al., 1989, 1991; Hinckley et al., 1991). GW7+8 is closer to those levels observed in Green Bay in June 1989. Chlordane levels in June 1989 ranged from 14 to 71 pg mÿ3 at a median temperature of 19 C. The trend is consistent with an increase in the concentration of semi-volatile compounds in ambient air at higher temperatures, although di€erences in air transport pathways also contribute to the variability (Ho€ et al., 1992a). Results from the Great Lakes cruise in August 1990 were higher than June 1989 Green Bay values with a mean over all four lakes of Chlordane=174‹77 pg mÿ3. The highest average chlordane concentration was observed over Lake Michigan at 247 pg mÿ3 followed by Ontario, 227 pg mÿ3, Erie, 161 pg mÿ3 and Huron, 109 pg mÿ3 (including Lake St. Clair, GL7). Results from this study are several times higher than annual average values observed in Egbert, ON, 40 pg mÿ3, (Ho€ et al., 1992b) and from the three IADN study sites, 8.0±40 pg mÿ3, (Sweet et al., 1996; Table 4). However, our results are closer to maximum observed values from the two studies (Ho€ et al., 1992b, maximum=94 pg mÿ3, Sweet et al., 1996, maximum values 25±157 pg mÿ3). The high levels of chlordanes on the cruise coupled with the fact that air trajectories show mainly local transport suggests a regional source for chlordanes over the Great Lakes. 3.2.2.2. DDT. Samples in this study were analyzed for two DDT group compounds, 4,40 -DDT and 4,40 -DDE. Concentrations of these were below the LOD in Green Bay in February 1988. However, measurable levels were found at Green Bay in June 1989, where the average DDT and DDE concentrations were 8.7‹5.6 pg mÿ3 and 15‹8.8 pg mÿ3 (Table 3). Our values are two to three times lower than average annual values observed at Egbert, ON, during 1989 (Ho€ et al., 1992b; Table 4), but were in the same range as annual average values from the IADN stations (Sweet et al., 1996). During August 1991 an overall average concentration of 38‹72 pg mÿ3 was observed for DDT and 59‹45 pg mÿ3 for DDE (Table 3). The lowest DDT and DDE concentrations over these Great Lakes cruise were found in Lake Huron. In two out of the three air samples collected over Lake Huron (GL5 and GL6), DDE was below the limit of detection. In one sample, from

397

central to eastern Lake Erie, GL10, DDE was also below the limit of detection. DDT was found above the limit of detection in all 15 samples. The highest concentrations of both DDT and DDE were found over the Lake St. Clair region at 294 pg mÿ3 and 123 pg mÿ3, respectively. The levels of 4,40 -DDT in this single sample were 6.5 times higher than any other sample during the cruise. The DDT:DDE ratio in the Lake St. Clair sample was 2:3. Of those samples where DDE was above LOD, only two air samples exhibited a DDT:DDE ratio >1 (Lake St. Claire and Lake Ontario). The remaining samples had a ratio value ranging from 0.14 to 0.64. This suggests that much of the DDT entering the Great Lakes atmosphere has been transformed to DDE. Since air trajectories did not implicate transport from out of the region within a 5-day period, a local source of DDT in the Lake St. Clair/Detroit River region may have caused increased air concentrations and a higher MT:DDE ratio value. 3.2.2.3. CHBs (toxaphene). Air concentrations of CHBs measured in this study in February 1988 ranged from 15 to 26 pg mÿ3. This re¯ects, essentially, a global `background' signal as similar results have been observed in remote locations. Arctic measurements of CHBs ranged from 38 pg mÿ3 in 1988 in the Bering and Chukchi Seas (Hinckley et al., 1991) to 17 pg mÿ3 in 1988 at Alert, Northwest Territories (NWT) (Patton et al., 1991), 6.9 pg mÿ3 in 1992 at Resolute Bay, NWT (Bidleman et al., 1995), and 5.2±10 pg mÿ3 in 1992 at Alert, NWT (Fellin et al., 1996). Other CHB measurements from Sable Island, Nova Scotia, are 23 pg mÿ3 in January/ February 1988 and 47 pg mÿ3 in July/August 1989 (Bidleman et al., 1992). During June 1989 CHB concentrations in Green Bay ranged from 30 to 89 pg mÿ3. This range compares well with the average concentration from 1989 measured in Egbert (26‹32 pg mÿ3; Ho€ et al., 1992b).

Fig. 5. Chlorinated bornane homolog relative concentrations in units of percent (%). Comparison of a toxaphene standard to average results from Green Bay (combined results from February 1988 and June 1989) and the Great Lakes cruise, August 1990.

398

L.L. McConnell et al./Environmental Pollution 101 (1998) 391±399

CHB analysis of the Great Lakes cruise resulted in only 4 data points from 15 air samples because sample extracts were combined to improve delectability. CHB concentrations were highest over Lake Michigan, 65 pg mÿ3. Extracts from two air samples collected over Lake Ontario were combined with the ®nal two air samples from Lake Erie for CHB analysis (G12±15). This pooled sample showed the second highest CHB concentration of 38 pg mÿ3. Results from Erie-only air samples were lower at 16 pg mÿ3 followed by Lake Huron at 14 pg mÿ3. Relative CHB homolog concentrations of the toxaphene standard are compared to the average values from Green Bay, June 1989 and an average of all the Great Lakes measurements (Fig. 5). Abundance of the 7-chlorinated congeners was higher than the standard in both the Green Bay and Great Lakes samples while the 8- and 9-chlorinated congeners were lower than the standard in both data sets. This may be a re¯ection of the di€erence in volatility of the various isomer groups and/or a re¯ection of a source that has undergone a dechlorination degradation reaction (Seiber et al., 1979; Howdeshell and Hites, 1996).

References Achman, D.R., Hornbuckle, K.C., Eisenreich, S.J., 1993. Volatilization of polychlorinated biphenyls from Green Bay, Lake Michigan. Environmental Science and Technology 27, 75±87. Baker, J.E., Eisenreich, S.J., 1990. Concentrations and ¯uxes of polycyclic aromatic hydrocarbons and polychlorinated biphenyls across the air±water interface of Lake Superior. Environmental Science and Technology 24, 342±352. Bidleman, T.F., Cotham, W.E., Addison, R.F., Zinck, M.E., 1992. Organic contaminants in the northwest Atlantic atmosphere at Sable Island, Novia Scotia, 1988±1989. Chemosphere 24, 1389±1412. Bidleman, T.F., Falconer, R.L., Walla, M.D., 1995. Toxaphene and other organochlorine compounds in air and water at Resolute Bay, N.W.T., Canada. Science of the Total Environment 60/161, 55±63. Bidleman, T.F., Wideqvist, U., Jansson, B., Soderlund, R., 1987. Organochlorine pesticides and polychlorinated biphyenls in the atmosphere of southern Sweden. Atmospheric Environment 21, 641±654. Billings, W.N., Bidleman, T.F., 1983. High volume collection of chlorinated hydrocarbons in air using three solid adsorbents. Atmospheric Environment 17, 383±391. Cotham, W.E., Bidleman, T.F., 1995a. Polycyclic aromatic hydrocarbons and polychlorinated biphenyls in air at an urban and a rural site near Lake Michigan. Environmental Science and Technology 29, 2782±2789. Cotham, W.E., Bidleman, T.F., 1995b. Estimating the atmospheric deposition of organochlorine contaminants to the Arctic. Environmental Science and Technology 29, 2782±2789. Eisenreich, S.J., Strachan, W.M.J., 1992. Estimating Atmospheric Deposition of Toxic Substances to the Great LakesÐAn Update. Report of the Gray Freshwater Biological Institute, University of Minnesota, Navarre, MN. Fellin, P., Barrie, L.A., Dougherty, D., Toom, D., Muir, D., Grift, N., Lockhart, L., Billeck, B., 1996. Air monitoring in the Arctic: results for selected persistent organic pollutants for 1992. Environmental Toxicology and Chemistry 15, 253±261.

Hinckley, D.A., Bidleman, T.F., Rice, C.P., 1991. Atmospheric organochlorine pollutants and air±sea exchange of hexachlorocyclohexane in the Bering and Chuckchi Seas. Journal of Geophysical Research 96, 7201±7213. Hillery, B.R., Basu, I., Sweet, C.W., Hites, R.A., 1997. Temporal and spatial trends in a long-term study of gas-phase PCB concentrations near the Great Lakes. Environmental Science and Technology 31, 1811±1816. Ho€, R.M., Chan, K.W., 1986. Atmospheric concentrations of chlordane at Mould Bay, N.W.T., Canada. Chemosphere 15, 449±452. Ho€, R.M., Muir, D.C.G., Grift, N.P., 1992a. Annual cycle of polychlorinated biphenyls and organohalogen pesticides in air in southern Ontario. 2. Atmospheric transport and sources. Environmental Science and Technology 26, 276±283. Ho€, R.M., Muir, D.C.G., Grift, N.P., 1992b. Annual cycle of polychlorinated biphenyls and organohalogen pesticides in air in southern Ontario. 1. Air concentration data. Environmental Science and Technology 26, 266±275. Ho€, R.M., Strachan, W.M.J., Sweet, C.H., Chan, C.H., Shackleton, M., Bidleman, T.F., Brice, K.A., Burniston, D.A., Cussion, S., Gatz, D.F., Harlin, K., Schoeder, W.H., 1996. Atmospheric deposition of toxic chemicals to the Great Lakes: a review of data through 1994. Atmospheric Environment 30, 3505±3527. Hornbuckle, K.C., Achman, D.R., Eisenreich, S.J., 1993. Over-water and over-land polychlorinated biphenyls in Green Bay, Lake Michigan. Environmental Science and Technology 27, 8798. Hornbuckle, K.C., Jeremiason, J.D. Jr., Sweet, C.W., Eisenreich, S.J., 1994. Seasonal variations in air±water exchange of polychlorinated biphenyls in Lake Superior. Environmental Science and Technology 28, 1491±1501. Hornbuckle, K.C., Sweet, C.W., Pearson, R.F., Swackhamer, D.L., Eisenreich, S.J., 1995. Assessing annual water±air ¯uxes of polychlorinated biphenyls in Lake Michigan. Environmental Science and Technology 29, 869±877. Howdeshell, M.J., Hites, R.A., 1996. Historical input and degradation of toxaphene in Lake Ontario sediment. Environmental Science and Technology 30, 220±224. Jeremiason, J.D., Hornbuckle, K.C., Eisenreich, S.J., 1994. PCBs in Lake Superior, 1978±1992: decreases in water concentrations re¯ect loss by volatilization. Environmental Science and Technology 28, 903±914. McConnell, L.L., 1992. Air±water gas exchange of chlorinated organic compounds. PhD Dissertation, University of South Carolina. McConnell, L.L., Cotham, W.E., Bidleman, T.F., 1993. Gas exchange of hexachlorocyclohexane in the Great Lakes. Environmental Science and Technology 27, 1304±1311. Ngabe, B., Bidleman, T.F., 1992. Occurrence and vapor-particle partitioning of heavy organic compounds in ambient air in Brazzaville, Congo. Environmental Pollution 76, 147±156. Patton, G.W., Hinckley, D.A., Walla, M.D., Bidleman, T.F., Hargrave, B.T., 1989. Airborne organochlorines in the Canadian high Arctic. Tellus 41B, 243±255. Patton, G.W., Walla, M.D., Bidleman, T.F., Barrie, L.A., 1991. Polycyclic aromatic and organochlorine compounds in the atmosphere of northern Ellesmeere Island. Journal of Geophysical Research 96, 10867±10877. Ridal, J.J., Kerman, B., Durham, L., Fox, M.E., 1996. Seasonality of air±water ¯uxes of hexachlorocyclohexanes in Lake Ontario. Environmental Science and Technology 30, 852±858. Ridal, J.J., Bidleman, T.F., Kerman, B.R., Fox, M.E., Strachan, W.M.J., 1997. Enantiomers of a-hexachlorocyclohexane as tracers of air±water gas exchange in Lake Ontario. Environmental Science and Technology 31, 1940±1945. Seiber, J.N., Madden, S.C., McChesney, M.M., Winterlin, W.L., 1979. Toxaphene dissipation from treated cotton ®eld environments: component residual behavior on leaves and in air, soil, and sediments determined by capillary gas chromatography. Journal of Agriculture and Food Chemistry 27, 284±291.

L.L. McConnell et al./Environmental Pollution 101 (1998) 391±399 Strachan, W.M.J., Eisenreich, S.J., 1988. Mass Balancing of Toxic Chemicals in the Great Lakes: the Role of Atmospheric Deposition. Report to the International Joint Commission, Windsor, Ontario, May 1988. Swackhamer, D.L., Armstrong, D.E., 1986. Estimation of the atmospheric and nonatmospheric contributions and losses of polychlorinated biphenyls for Lake Michigan on the basis of sediment records of remote lakes. Environmental Science and Technology 20, 879±883.

399

Sweet, C.W., Harlin, K., Gatz, D.F., Bauer, S., 1996. Great Lakes Integrated Atmospheric Deposition Network (IADN) Data Report 1993±1994, Illinois State Water Survey, Champaign, IL, March, 1996. Voldner, E.C., Schroeder, W.H., 1989. Modelling of atmospheric transport and deposition of toxaphene into the Great lakes ecosystem. Atmospheric Environment 23, 1949±1961.