Environ. Sci. Technol. 1997, 31, 2092-2097
Spatial Distribution of Hexachlorocyclohexane Isomers in the Bering and Chukchi Sea Shelf Ecosystem C L I F F O R D P . R I C E * ,† A N D VICTOR V. SHIGAEV‡ U.S. Department of Agriculture, Agricultural Research Service, Environmental Chemistry Laboratory, Building 007, Room 213, Beltsville, Maryland 20705, and Wildlife International, Ltd., 8598 Commerce Drive, Easton, Maryland 21601
The spatial distribution of fields for R and γ hexachlorocyclohexanes are described for the Bering/Chukchi Shelf ecosystem. Fields for the surface concentration of these isomers are defined that closely match the water mass structure of this region. The relative abundances for the R and γ isomers were also excellent markers for the prevailing currents here. Water type groupings based on the percentage differences from respective mean values for the R and γ concentrations represented water zones that accurately depicted the Anadyr Current and a Siberian Coastal Front, which originates along the upper Chukchi Peninsula. Values for the R/γ ratios ranged from a low of 2.52 for the Pacific Water inputs for this region to a high of 9.36 for the Siberian coastal current water. This study demonstrates the importance of using marker chemicals like HCHs to identify ocean currents.
Introduction Chlorinated hydrocarbons (CHCs) have long served as useful tracers for global dispersion processes especially in the atmosphere. Even though movement of CHCs in ocean currents seem likely, documentation however is sparse. Harvey and Steinhauer (1) explained polychlorinated biphenyl (PCB) movement in the North Atlantic water on current patterns. They suggest that considerable PCBs enters North Atlantic water through atmospheric deposition from the northeastern United States, and this material eventually advects northward up into the Denmark Strait and the Norwegian Sea. In these regions, the PCBs are eventually entrained with the sinking water masses that form the southward-flowing North Atlantic Deep Water (NADW) originating in this region. Harvey and Steinhauer supported their hypothesis by showing a deep water maximum, 2.4 ng/L at 2600 m, for PCBs at a North Atlantic site downstream from the divergence zone located along the track of this NADW current. Fischer and associates (2) provided additional evidence supporting the role of ocean currents in the transport of CHCs in the North Atlantic Ocean. They measured HCH isomers at various depths in the ocean and found that near Bermuda, where there is a known convergence of several water masses, that the R-HCH/γ-HCH ratios were distinctly different * Corresponding author telephone: (301)-504-6398; fax: (301)504-5048; e-mail:
[email protected]. † U.S. Department of Agriculture. ‡ Wildlife International, Ltd.
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depending on which horizon of the water column was sampled. In fact, the HCH ratio profiles closely matched the major water mass zonation pattern at this station. The authors proposed that the R/γ ratios of 7.2 and 2.0, respectively, at 20 and 250 m in the upper layers are within the Sargasso Sea water mass and represent direct North Atlantic atmospheric loading and water originating from the north equatorial current and the Gulf Stream. The middle zone had low values for the R/γ ratios of 0.2 and 0.14 for the 400 and 900 m depths, respectively, which they propose represents the North Atlantic Central Water mass, which originated in the Southern Hemisphere. The deepest layer was represented by one measurement, 3.3, at 1200 m; they ascribed this to the NADW referred to earlier that is transported southward from Greenland and Labrador along the floor of the western North Atlantic. They also showed that the relative amounts of each isomer in each of the zones agree with the existing data on the levels that reside in the air at the respective source locations for each of these zones. The justification for this statement arises from the fact that the ratio of the two isomers that occurs in the surface water at any one location should reflect the ratio of R- and γ-HCHs that predominates in the air at that location due to gas exchange processes (3). Fischer and associates (2) explained how the HCH class of compounds is ideal as tracers of water masses: (1) They are chemically and biological stable; (2) Their equilibrium distribution in water shows a significant preference for the water phase (4); (3) Their adsorption to organic matter and associated lipids is moderate and therefore precludes significant loss by this route; (4) They have distinctive global source loadings. For example, the Northern Hemisphere, especially the Far East, is the major user of the BHCs (5) (the technical HCH insecticide product that has a high R/γ ratio in its makeup), while the Southern Hemisphere primarily uses lindane (the γ isomer) (2). Direct observations that HCHs behave unusually in the water column were first reported by Tanabe and Tatsukawa (6). They showed that at a deep water ocean sampling site in the western North Pacific Ocean that HCHs were not evenly distributed with depth but tended to be highest in the surface layers; while the other common OC residues, e.g., PCBs, DDT residues, and chlordanes, were relatively evenly distributed with depth. A similar observation was reported at a deepprofile station in the Bering Sea (7). This characteristic is largely due to the relatively high water solubility of HCHs relative to other OC residues. Other OCs like DDTs, PCBs, and hexachlorobenzene (HCB) have greater affinity for particulates and are more likely stripped out of the water column with sedimenting particles and thus distribute more evenly from surface to bottom at deep ocean sites. HCHs therefore tend to reside for long periods of time in the dissolved phase in the water column and therefore have the potential to track very well with ocean currents. This should be especially true in particulate sparse systems such as exist in open ocean waters. In this paper, we attempt to correlate the water mass distribution in the Bering/Chukchi Seas with the distribution of the R and γ isomers of hexachlorocyclohexanes (HCHs). Fischer and associates (2) successfully proved the usefulness of using HCH ratios as a technique to identify water masses with a small data set. It is our goal to show this relationship using a larger data set and in a shallow water shelf system. The distribution patterns of the hexachlorocyclohexane group of compounds are described for the Bering and Chukchi Sea areas. A method to identify the R and γ concentration distribution over the Bering and Chukchi Seas for August 1993 is employed. Resulting distribution patterns are com-
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1997 American Chemical Society
TABLE 1. Hexachlorocyclohexane Distribution in Surface Water of Bering/Chukchi Seas Russian Dataa (ng/L) station no.
FIGURE 1. Spatial distribution of shelf waters and current patterns in the shelf area of the Bering/Chukchi Seas in August 1988. Zones: (I) Anadyr Current Water; (II) Bering Shelf Water; (III) Alaskan Shelf Water; (IV) Gulf of Anadyr Water; and (V) Siberian Coastal Water. (Distribution of water masses according to ref 8. Current patterns in Bering Shelf zone according to ref 12, and current patterns in Chukchi Sea according to ref 13.) pared to the water types that were determined (8) using traditional oceanographic techniques, temperature, salinity, and biological markers.
Experimental Methods Water Sampling and Chemical Analysis. The data used in this study come from 35 stations, which were occupied over the Bering/Chukchi Sea Shelf area during an August 1988 joint US/USSR expedition. Several physical, chemical, and biological parameters were measured simultaneously at each station. This provided an opportunity to describe the distribution of persistent chlorinated hydrocarbons relative to the biological and physical oceanography of the region. These physical oceanography features involved use of twodimensional temperature and salinity data, which were compiled using the TS-curve method of Mamaev (9) to describe the distribution of water masses in this region (Figure 1) (8). The station numbers and their locations are indicated in Table 1 and Figure 2. A more complete discussion of the methods and presentation of the entire findings for the expedition are covered in ref 10. Briefly, the Russian samples were collected by Niskin casts, which were processed for extraction using XAD-2 preconcentration methods. The cleaned extracts were analyzed by fused silica electron capture gas chromatography (7). The U.S. water samples were collected directly in empty nanograde solvent bottles that were then extracted using methylene chloride. Spikes and duplicates were performed continuously during the sampling and analyses by the U.S. scientists. Recoveries averaged 98% for R-HCH and 86% for γ-HCH, and the replicates were all less than 20% relative percent difference for the duplicate pairs. These QA samples were run at the rate of 5%. As with the Russian samples, the U.S. samples were analyzed using high-resolution fused silica electron capture gas chromatography (5). Oceanographic Data. Conductivity-temperature-depth (CTD) casts were made surface-to-bottom using a Sea-Bird Electronics Model SBE-9 system with a General Oceanic
3 7 9 13 15 18 22 24 26 27 32 36 41 45 47 49 50 53 55 57 59 61 64 67 69 72 74 82 86 89 96 100 104 106 a
collection date Jul 30 Aug 02 Aug 02 Aug 03 Aug 04 Aug 04 Aug 05 Aug 05 Aug 06 Aug 06 Aug 07 Aug 08 Aug 8 Aug 09 Aug 10 Aug 10 Aug 10 Aug 11 Aug 2 Aug 12 Aug 12 Aug 13 Aug 13 Aug 14 Aug 14 Aug 15 Aug 15 Aug 19 Aug 20 Aug 20 Aug 21 Aug 22 Aug 23 Aug 24
r
γ
2.33 2.45 2.15 1.64 1.20 1.40 1.40 1.76 1.58 1.67 1.80 1.91 1.64 1.40 1.26 2.02 2.38 2.50 2.78 2.54 2.50 3.02 2.18 1.80 1.40 1.01 3.34 2.65 2.12 2.12 1.98 1.89 1.64 1.58
0.99 1.32 1.58 0.75 0.62 0.44 0.59 0.36 1.25 0.99 1.12 1.25 1.02 1.12 0.75 1.02 1.30 1.12 1.17 1.12 1.59 1.87 0.59 0.31 0.28 0.13 0.67 1.17 0.95 1.02 0.86 0.71 0.25 0.48
Chernyak et al. (7).
b
U.S. Datab (ng/L) r
γ
2.56 2.68 2.55
0.72 0.62 0.74
1.95
0.79
1.91
0.54
2.33
0.62
2.31
0.63
2.59 2.72 2.18 2.19 1.85 1.91 1.78
r
γ
1.68 1.23 1.44 1.44
0.45 0.37 0.27 0.36
1.62 1.71 1.85
0.75 0.60 0.68
1.68
0.62
1.29 2.07
0.45 0.62
2.57
0.68
2.61 2.57
0.68 0.96
2.24 1.85 1.44 1.04
0.36 0.19 0.17 0.08
1.62
0.29
0.50
2.10
2.75
bias-corrected Russian Data
0.64
0.59 0.71 0.57 0.62 0.72 0.51 0.39
Hinckley et al. (5).
RMS12 rosette water sampler (11). The water samples were periodically analyzed to allow verification of the CTD values. Figure 1 shows the classification of the waters of the Northern Bering/Chukchi Sea ecosystem on the basis of an analysis of the spatial distribution of the temperature/salinity fields. The method of T,S-curves was used in separating the structural types of the water masses (9). Also reflected in this figure are the averaged general structural dynamics of the seawaters of this system as shown by the local water circulations. HCH Data. Table 1 presents the results published by Hinckley et al. (5) and Chernyak et al. (7) for the HCH concentrations in the surface water (0-10) m of the Bering/ Chukchi Seas. The U.S. and Russian concentration values were consistently different at each station. The goal of this study was to get a complete and accurate coverage of the study area, so a correction was applied to compensate for this discrepancy. Such biases are not uncommon when comparing results from two different laboratories using different methods of sampling and extraction. Because the U.S. data had better quality control during the analyses, the U.S. data were used as the standard and the Russian data were adjusted. Since no reference samples were employed, it is unclear which data are most accurate. All of the 14 duplicate U.S. and Russian matched stations were compared in a pairwise fashion for each common analyte. The average sample-weighted factor difference was 0.397 times less for γ-HCH in each U.S. sample than in the Russian samples; this difference factor was 0.026 higher for R-HCH in the U.S. samples versus the Russian samples. The data published by Chernyak et al. (7) for a deep water site in the Bering Sea was
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FIGURE 2. Geographical distribution of common data groups (identified as water types) generated by pairing the characteristics for the positive and negative differences in concentrations (anomaly percentage grouping) for r and γ HCH over the Bering/Chukchi Sea ecosystem. Numbers correspond to stations identified in Table 1.
TABLE 2. Vertical Distribution of Hexachlorocyclohexane Isomers in Southern Bering Sea, 53°95′00′′ N, 176°01′17′′ E hexachlorocyclohexane concn (ng/L)a depth (m)
r
γ
r/γ ratio
0 10 100 200 1000 3850
2.35 2.31 1.18 1.24 0.97 0.41
0.67 0.63 0.33 0.29 0.24 0.16
3.51 3.65 3.56 4.29 4.04 2.52
a These concentrations are the Russian data (7), which are shown here in their bias-corrected form.
also bias-corrected using this method (Table 2). Applying these corrections to all of the non-U.S.-matched Russian values resulted in the bias-corrected Russian data column (Table 1). The combined data, i.e., the bias-corrected Russian data (Table 1, 5th column) and uncorrected U.S. data (Table 1, 4th column) were used in a classification method that permitted identification of common groupings of the R- and γ-HCH concentrations (Table 3). The technique involved determining the percentage differences (anomaly percent) of each respective value (R, γ, and R/γ ratio) from their individual means for the entire sampled area. Analysis of the resulting data allowed grouping them into commonly occurring patterns. The patterns were spatially plotted over the geographic region corresponding to where the samples were collected (Figure 2). The principle of the method is that it showed how the data are grouped by the common characters
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of R- and γ-HCH isomer concentrations in two-dimensional space. Contour plots of the R-HCH/γ-HCH (R/γ) ratio values (from Table 3) for each of the stations were constructed over the sampled region by connecting the points of equal values into isopleths (Figure 3). The average R/γ ratio values for each of the zones that were identified in Table 3 are plotted as bar graphs in Figure 4. Also added to Figure 4 is the R/γ ratio value for Pacific Water (3850 m depth from Table 2 and inset of Figure 3), which is considered to be a primary source of water advecting by current action into this region.
Results The groupings of surface sampling data for R- and γ-HCH over the Bering and Chukchi Seas (Table 3 and Figure 2) were generated by pairing characteristics for positive and negative differences in concentrations (anomaly percentage grouping) for R- and γ-HCH (Table 1) at each station over the sampled area. The anomalies were paired for each analyte at each of the sample locations and then segregated into four grouping categories as follows: (1) both the R- and γ-HCH concentration was higher than their respective means, i.e., both positive; (2) both were negative relative to the mean, i.e., both negative; (3) negative R and positive γ; (4) positive R and negative γ. Using these criteria plus the fact that some similarly biased groups were not physically connected and/or they could be identified as statistically unique by testing other grouped parameters (i.e., the means for individual R or γ concentration, R/γ ratio values, average group salinities or temperatures), seven HCH-segregated water types were identified over the
TABLE 3. Water Types As Defined by Analysis of Combined Anomaly Grouping of r- and γ-HCH over Bering/Chukchi Seasa γ- HCH
r-HCH data groupings Bering Water (a)
station 7 9 36
average Anadyr Shelf Water (b)
13 15 18 22 24
average Anadyr Current (c)
26 27 32 41 96
average St. Lawrence Uwelling (d)
100 104 106
average North Shoal Water (e)
86 89 74
average Siberian Front (f)
64 67 69 72
average Chuckchi Shelf Water (g)
49 50 53 55 57 59 61
average undefined water
45 47
concn (ng/mL)
anomaly (%)
2.68 34.51 2.55 27.98 2.10 5.40 2.44 22.63 (b, c, d, f)b 1.68 -15.68 1.23 -38.27 1.44 -27.73 1.44 -27.73 1.95 -2.13 1.55 -22.31 (e, g) 1.62 -18.69 1.71 -14.17 1.85 -7.15 1.68 -15.68 1.85 -7.15 1.74 -12.57 (a, e, g) 1.91 -4.14 1.78 -10.66 1.62 -18.69 1.77 -11.16 (a, e, g) 2.18 9.41 2.19 9.92 2.59 29.99 2.32 16.44 (b, c, d, f) 2.24 12.43 1.85 -7.15 1.44 -27.73 1.04 -47.80 1.64 -17.56 (a, e, g) 2.07 3.89 2.33 16.94 2.57 28.99 2.31 15.94 2.61 31.00 2.57 28.99 2.75 38.02 2.46 23.40 (b, c, d, f) 1.91 -4.14 1.29 -35.25
concn (ng/mL)
anomaly (%)
0.62 15.14 0.74 37.42 0.79 46.71 0.72 33.09 (b, d, e, f) 0.45 -16.43 0.37 -31.29 0.27 -49.86 0.36 -33.15 0.50 -7.15 0.39 -27.57 (a, c, e, f, g) 0.75 39.28 0.60 11.42 0.68 26.28 0.62 15.14 0.72 33.71 0.67 25.17 (a, b, d, e, f) 0.51 -5.29 0.39 -27.57 0.29 -46.15 0.40 -26.34 (a, c, e, f, g) 0.57 5.85 0.62 15.14 0.59 9.57 0.59 10.19 (a, c, d, f) 0.36 -33.15 0.19 -64.72 0.17 -68.43 0.08 -85.14 0.20 -62.86 (a, b, c, d, e, g) 0.62 15.14 0.62 15.14 0.68 26.28 0.63 16.99 0.68 26.28 0.96 78.28 0.64 18.85 0.69 28.14 (b, d, f) 0.54 0.28 0.45 -16.43
combined anomaly grouping 1(+ +) 1(+ +) 1(+ +) 3(- -) 3(- -) 3(- -) 3(- -) 3(- -) 2(- +) 2(- +) 2(- +) 2(- +) 2(- +) 3(- -) 3(- -) 3(- -) 1(+ +) 1(+ +) 1(+ +) 4(+ -) 3(- -) 3(- -) 3(- -) 1(+ +) 1(+ +) 1(+ +) 1(+ +) 1(+ +) 1(+ +) 1(+ +) 2(- +) 3(- -)
r/γ ratio 4.32 3.45 2.66 3.48
anomaly (%)
0.18 -20.14 -38.39 -19.45 (c, f) 3.73 -13.48 3.32 -22.96 5.33 23.61 4.00 -7.30 3.90 -9.61 4.06 -5.95 (c, f) 2.16 -49.94 2.85 -33.95 2.72 -36.95 2.71 -37.20 2.57 -40.45 2.60 -39.70 (a, b, d, e, f, g) 3.75 -13.20 4.56 5.78 5.59 29.47 4.63 7.35 (c, f, g) 3.82 -11.36 3.53 -18.14 4.39 1.74 3.92 -9.25 (c, e) 6.22 44.21 9.74 125.66 8.47 96.31 13.00 201.29 116.87 (a, b, c, d, e, g) 3.34 -22.62 3.76 -12.90 3.78 -12.41 3.67 -15.02 3.84 -11.05 2.68 -37.96 4.30 -0.42 3.62 -16.05 (c, d) 3.54 -18.03 2.87 -33.56
temp (°C)
salinity (ppt)
7.24 6.76 7.31 7.10 (b, d, e, f) 6.83 6.57 7.29 6.53 5.57 6.56 (a, e, f) 9.11 6.26 7.13 7.12 2.06 6.34 (f) 6.29 5.65 6.14 6.03 (a, f) 3.23 6.12 2.51 3.95 (a, b) 3.88 4.94 2.17 2.51 3.37 (a, b, c, d, g) 4.78 6.10 4.41 4.05 5.51 5.28 9.54 5.67 (f) 2.28 4.95
32.60 31.70 31.59 31.96 (b) 31.87 31.57 31.16 31.46 31.99 31.61 (a, f) 30.95 32.77 31.68 31.66 32.69 31.95 (-) 31.78 32.08 31.89 31.91 (f) 31.05 31.69 32.22 31.65 (-) 32.24 31.95 32.25 32.22 32.17 (b, d) 32.13 31.66 32.09 32.24 31.76 25.67 29.41 30.71 (-) 24.04 32.52
a Data summaries for R, γ, and R/γ ratios, temperature, and salinity. Anomaly percentage calculated as percent difference of observed R, γ, or R/γ ratio from respective mean value for each of these over entire region b Letters designate those areas whose mean values are significantly different (σ < 0.05) than the means for this area.
sampled region. The specific criteria for selecting each zone and their regional identifications are as follows: region a, Bering Water where R- and γ-HCH are both positive biased; region b, Anadyr Self Water where both are negative biased; region c, Anadyr Current where R is negative and γ is positive biased; region d, St. Lawrence Upwelling where both are negative biased similar to the Anadyr Shelf Water but geographically separated from this zone; region e, North Shoal Water where both are positive biased but the region is geographically separate from the Bering Water mass; region f, Siberian Front where both are negative biased but the region is geographically separated from the St. Lawrence Upwelling and Anadyr Shelf Water as well as being uniquely isolated in concentration for γ-HCH (based on test results, Table 3); and region g, Chukchi Shelf Water where both are positive biased but the region is geographically isolated from the other positive biased groupings, Bering Water and North Shoal Water. There was no separate group of data that had positive R- and negative γ-HCH except for station 64, which appears to belong with the Siberian Front samples based on its high
γ-HCH bias and geographic proximity with the other stations belonging to this group (Figure 3). These groupings were assembled into distinctive boundary areas that are plotted previously as water mass zones in Figure 2. The exact boundaries of each of the regions defined in the figure are obviously rather speculative based on the limited data available to precisely define limits for these groupings; however, the similarity of these patterns to published data on water mass structure for this region lends support to the overall water mass structures that are proposed. There was one area of undefined water (northwestern Chukchi Sea) that did not appear common to any neighboring data groups. Another method for presenting the R- and γ-HCH distribution over this region involved sketching the most probable surface contour lines for R/γ ratios over the region (Figure 3). These results can be compared to Figures 1 and 2 in order to look for similarities in distribution patterns. The data in Figure 4 display the different R/γ ratios as bar chart data for each of the different water groupings described in Table 3. This presentation shows the relative differences
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IV (Gulf of Anadyr Water) is very similar to the Anadyr Shelf Water (region b) of the central part of the Anadyr Gulf, and Zone V (Siberian Coastal Water) coincides with the location where the R/γ ratio anomaly percentages were all very high (>44%), i.e., identified here as Siberian Frontal waters. Figure 1 also identifies a Zone II water type that typifies Bering Shelf water that is believed to work its way upward by current patterns into the Chukchi Sea (12). A similarity in groupings of positive bias for both R and γ concentrations was present at these same locations in Figure 2, i.e., the Bering Water, North Shoal water, and Chukchi Shelf water all had positive bias for both R and γ at these locations, suggesting that these all had similar source waters. Statistical analyses suggested that these were similar water types except for γ-HCH, which was significantly different in concentration between the Bering Water and the North Shoal water. One zone, the St. Lawrence Upwelling region, was exclusively identified by the R and γ anomaly method performed here. It is possible that this was not a distinct body of water but linked to the Anadyr Shelf Water, which also had a double negative for percent difference for the two HCH concentrations. Statistical analysis also supports the possibility that these two regions of water were not different (Table 3).
FIGURE 3. Isopleths for the r/γ ratio distributions over the Bering/ Chukchi Sea Shelf, August 1988. Inset shows the location of the deep water station (Station 3) in the Bering Sea. in these values that range from the highest value of 9.36 for the Siberian Frontal Water to a low of 2.52 for the Pacific Water. The six water types between these two extremes correspond to the regions depicted in Figure 2 and Table 3.
Discussion Several similarities in structure are apparent when comparing the general distribution of water masses as described using temperature and salinity data for the month of August 1988 (8), Figure 1 with the water masses and currents defined by the R- and γ-HCH concentrations displayed in Figures 2 and 3). The Anadyr Current (region c) defines a region very similar to that of Zone I (Anadyr Current Water) in Figure 1. Zone
From the above discussion, it is clear that the physical structure of marine ecosystems matches the chemical properties for HCH distribution. The surface contour plots for the R/γ ratios in Figure 3 depict the same patterns, and additionally, this method of presentation appears to match the circulation patterns over this region. These results, which were constructed on surface data only, show a similar pattern to the currents shown in Figure 1. For example the coastal Anadyr Current, which transects the Chirikov Basin and inputs into the Chukchi Sea, is quite apparent. Also shown is the narrow Siberian Coastal Current, which agrees well with similar data from other sources (observation from Russian Expeditions in 1932 and 1933 from the Dalnevostochnik and Krasnoarmeetc), where the existence of two sets of currents were demonstrated (13), one running along the Chukchi shores from westward to eastward and the other running from the Bering Strait. Other evidence for the existence of this current also comes from data obtained during our 1988 expedition especially the salinity, temperature (8), nutrients (14), and O18 (15) measurements that were taken in this area. The data (Figure 3) show a very narrow current band extending along the coast that veers inward into the Chukchi basin upon
FIGURE 4. Distribution of r/γ ratios over different water types in Bering/Chukchi Sea ecosystem.
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contacting the current flowing upward through the Bering Strait. Another region clearly defined by the R/γ contours is the region of cyclonic flow of water in the Gulf of Anadyr. Finally, in order to consider the change in R/γ ratio as water cycles through this system, a plot of the average values for the respective groupings is shown in Figure 4. The value of 9.36 for the R/γ ratio of this Siberian Coastal Current Water is much higher than all of the other ratios. This may be related to the unique origin of the water contained in this current zone. The Siberian Coastal Water has a major source input from several rivers that discharge into the coastal Siberian waters, i.e., the Ob, Yenisey, Lena, and Kolyma Rivers. Other factors would be polynya waters and melt ice as the northern ice retreats each summer. Deep older ice records show that the R-HCH to γ-HCH ratio increases with depth (16). If older ice is melting and adding to the HCH that was measured in this Siberian Coastal Current Water, then the higher R-HCH amounts could be coming from this melt ice. The deepest sample of water from the central Bering site is likely linked to the Abyssal Water mass of the Central Pacific (17) and should have HCH ratios typical of this water. Current patterns suggest that this is the area that supplies the bottom colder waters to the Bering Shelf. Data on HCHs in this area for 1981 (6) show that the deepest water samples had the lowest total HCH concentrations in their water profile, HCH sums (R + γ) ) 0.31 and 0.23 ng/L, respectively, for two stations off the coast of Japan in the Pacific. These samples also had R/γ ratios of 0.83 and 2.28, respectively, at depths of 5000 and 4500 m (6), which compares roughly to the low value (2.52) measured in the deepest sample from the deep profile station (Table 2). Others have shown that R/γ ratios are good indicators of source loading for HCH isomers in aquatic environments (18) and the atmosphere (19). The remaining R/γ ratio values plotted in Figure 4 were not significantly different from each other, except for the Anadyr Current, which had the lowest average value, and the Siberian Front value, which had the highest. One could speculate that a major source of the Anadyr Current waters are from the deep Bering and there are data to support these speculations (20). Recent data are available for the 1993 HCH distribution over the Bering/Chukchi Sea region (21). Their 29 separate surface water samples were processed using the percent anomaly method described here to discern R- and γ-HCH concentration groupings over the area. Some of the same grouping patterns that were observed with our data were identified using their data, i.e., the Anadyr Current grouping and a general similarity in the data for the Chukchi Sea was apparent. Also their data showed a clear grouping of values for the samples collected from their most northern sites near the ice edge. However, the remainder of their data was too scattered to provide dense enough coverage to account for more detailed water patterns. Furthermore, their data for the Gulf of Anadyr and the Bering shelf was very scattered as to HCH anomaly types that were identified. This suggests that different current regimes were present when they were sampling versus those present during the 1988 collections. Furthermore, the net direction of exchange of HCHs at the water surface was not totally from the air as it was in 1988 (5). In some regions of this system, it was determined that the sea surface was actually outgassing HCHs at that time (21). This fact might account for greater variability in the results for 1993 than was observed in 1988 (5). Iwata et al. (22) reported concentration data for R- and γ-HCH from the Chukchi and Bering Seas for 1989. Their results were lower than reported here, i.e., especially for γ-HCHs, which were more than two times lower. Their average R/γ ratios were 9.6 for the Chukchi and 8.3 for the Eastern Bering Sea. Jantunen and Bidleman (21) found average R/γ ratios of 4.9 for the Bering and 3.7 for the Chukchi Sea in 1993, which are comparable to those found here. The average concentrations reported by Jantunen and Bidleman (21) were 18% lower for
R-HCH and 24% lower for γ-HCH than the Hinckley et al. (5) data, which were used in this paper. The data in Figure 2 were compared to similar analyses that were performed on the distributions of DDT and other organochlorines reported by Chernyak et al. (7) over many of these same stations. These other contaminants did not exhibit any pattern that resembled the water mass distributions as defined by HCHs for this region. Some groupings appeared with DDT, which indicated possible surface water runoff contributions near the major rivers that supply this system. This tendency for higher river runoff for DDT suggests that there is a greater tendency for DDT to adsorb to particulate matter than HCHs. River runoff generally results in high particulate loading.
Literature Cited (1) Harvey, G. R.; Steinhauer, W. G. J. Mar. Res. 1976, 34, 561. (2) Fischer, R. C.; Kra¨mer, W.; Ballschmiter, K. Chemosphere 1991, 23, 889. (3) McConnell, L. L.; Cotham, W. E.; Bidleman, T. F. Environ. Sci. Technol. 1993, 27, 1304. (4) Mackay D.; Shiu W. Y. J. Phys. Chem. Ref. Data 1981, 10, 1175. (5) Hinckley, D. A.; Bidleman, T. F.; Rice, C. P. J. Geophysical Res. 1991, 96, 7201. (6) Tanaba, S.; Tatsukawa, R. J. Oceanogr. Soc. of Jpn. 1983, 39, 53. (7) Chernyak, S. M.; Vronskaya, V. M.; Kolobova, T. P. In Results of the third joint US-USSR Bering & Chukchi Seas Expedition (BERPAC), Summer 1988; Nagel, P. A., Ed.; U.S. Fish and Wildlife Service: Washington, DC, 1992; Chapter 8.1.2. (8) Coachman, L. K.; Shigaev, V. V. In Results of the third joint USUSSR Bering & Chukchi Seas Expedition (BERPAC), Summer 1988; Nagel, P. A., Ed.; U.S. Fish and Wildlife Service: Washington, DC, 1992; Chapter 2.1. (9) Mamaev, O. I. Temperature-Salinity analysis of World Ocean Waters; Elsevier Scientific Publishing Co.: Amsterdam-OxfordNew York, 1975; p 139. (10) Nagel, P. A., Ed. Results of the third joint US-USSR Bering & Chukchi Seas Expedition (BERPAC), Summer 1988; U.S. Fish and Wildlife Service: Washington, DC, 1992; p 415. (11) Amos, A. F.; Coachman, L. K. In Results of the third joint USUSSR Bering & Chukchi Seas Expedition (BERPAC), Summer 1988; Nagel, P. A., Ed.; U.S. Fish and Wildlife Service: Washington, DC, 1992; Chapter 2.2. (12) Coachman, L. K.; Aagard, K.; Tripp, R. B. Bering Strait: The Regional Physical Oceanography; University of Washington Press: Seattle, 1975; p 53. (13) Gakkel, Y. Y.; Hmiznikov, P. K. Scientific Results of Expedition on RV Cheluskan and Camp Schmidt; Moscow, 1938; Vol. II, p 120. (14) Whitledge, T. F.; Gorelkin, M. I.; Chernyak, S. M. In Results of the third joint US-USSR Bering & Chukchi Seas Expedition (BERPAC), Summer 1988; Nagel, P. A., Ed.; U.S. Fish and Wildlife Service: Washington, DC, 1992; Chapter 3.1. (15) Grebmeier, J. M. In Results of the third joint US-USSR Bering & Chukchi Seas Expedition (BERPAC), Summer 1988; Nagel, P. A., Ed.; U.S. Fish and Wildlife Service: Washington, DC, 1992; Chapter 7.1. (16) Gregor, D. J. In Long Range Transport of Pesticides; Kurtz, D. A., Ed.; Lewis: Chelsea, MI, 1990; p 373. (17) Couper, A., Ed. The Times Atlas of the Oceans; London, 1983; p 172. (18) Kurtz, D. A.; Atlas, E. L. In Long Range Transport of Pesticides; Kurtz, D. A., Ed.; Lewis: Chelsea, MI, 1990; p 143. (19) Pacyna, J. M.; Oehme, M. Atmos. Environ. 1988, 22, 243. (20) Hughes, F. W.; Coachman, L. K.; Aagaard, K. In Oceanography of the Bering Sea; Hood, D. W., Kelley, E. J., Eds; Occasional Publication 2; Institute of Marine Science, University of Alaska: Fairbanks, AK, 1974; p 59-103. (21) Jantunen, L. M.; Bidleman, T. F. Environ. Sci. Technol. 1995, 29, 1081. (22) Iwata, H.; Tanabe, S.; Sakai, N.; Tatuskawa, R. Environ. Sci. Technol. 1993, 27, 1080.
Received for review October 31, 1996. Revised manuscript received February 27, 1997. Accepted March 3, 1997.X ES9609258 X
Abstract published in Advance ACS Abstracts, May 1, 1997.
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