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Distribution of organochlorine pesticides in sediments from Kyeonggi Bay and nearby areas, Korea
Environmental Pollution 114 (2001) 207±213
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Distribution of organochlorine pesticides in sediments from Kyeonggi Bay and nearby areas, Korea K.T. Lee a, S. Tanabe b, C.H. Koh a,* a
School of Earth and Environmental Sciences (Oceanography program), College of Natural Sciences, Seoul National University, Seoul 151-742, South Korea b Department of Environment Conservation, Ehime University, Tarumi 3-5-7, Matsuyama 790, Japan Received 7 June 2000; accepted 13 October 2000
``Capsule'': The geographic distribution of organochlorine pesticides in sediments in Kyeonggi Bay, Korea was determined. Abstract The residues of oragnochlorine pesticides (OCPs) in 62 sediments from Kyeonggi Bay and nearby areas in the west coast of Korea were determined. The concentrations of chlordanes (CHLs) and DDTs showed a distinctive gradient of contamination between inner and outer sites of Incheon North Harbor (INH), whereas hexachlorocyclohexanes (HCHs) were uniformly distributed at most sites studied. The distribution of CHLs and DDTs was strongly correlated with total organic carbon contents in sediments while HCH residue levels were independent. Relationship between contaminant's concentration and environmental factors was analyzed by principal component analysis. Distribution patterns of T-CHLs, T-DDTs, and TOC were similar while those of T-HCHs, mud content, and grain size were similar. The notable contamination by CHLs and DDTs was found in INH where these levels were one or two orders of magnitude higher than other sites. The dominant OCPs in sediments were b-HCH among HCH compounds, trans-chlordane among CHL compounds, and p,p0 -DDD among DDT compounds. The higher concentrations and compositional pattern of OCPs in INH sediments indicate that INH is in the vicinity of the source. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: Organochlorine pesticides (OCPs); Korean sediments; Principal Component Analysis; Isomer or metabolite ratio
1. Introduction Organochlorine pesticides (OCPs) such as hexachlorocyclohexanes (HCHs), chlordanes (CHLs), and DDTs were known to have bioaccumulative nature because of their high lipophilicity and persistency (Tanabe and Tatsukawa, 1992). In the aquatic environment, organochlorine compounds are removed from the water column and adsorbed on the particulate matters due to their high anity for organic matter, and ®nally accumulated in sediments, which may play a role as a secondary contamination source. These contaminants also accumulate in the sediment-dwelling organisms which may be transferred to higher trophic levels through the food chain. Organochlorine residues from
* Corresponding author. Tel.: +82-2-880-6750; fax: +82-2-8720311. E-mail address: [email protected] (C.H. Koh).
the various regions have been well reported (Tanabe et al., 1983; DouAbul et al., 1988; Sericano et al., 1990; Thao et al., 1993; Iwata et al., 1994a; Morrison et al., 1996; Tate and Heiny, 1996), however, information on the occurrence of OCPs in Korea is scarce. As a component of integrated assessment of environmental health on the west coast of Korea, this work was designed to determine the geographic distribution of selected OCP contaminants on the west coast of Korea. 2. Materials and methods 2.1. Sample collection The sediment samples were collected from Kyeonggi Bay, Namyang Bay and Lake Shihwa on the west coast of Korea (Fig. 1). Kyeonggi Bay with tide dierence as high as 8 m is located on the west coast of Korea. Incheon Harbor in Kyeonggi Bay is highly polluted as
0269-7491/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S0269-7491(00)00217-7
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K.T. Lee et al. / Environmental Pollution 114 (2001) 207±213
Fig. 1. A map of study areas and sampling sites.
there are many factories located in the vicinity. In addition, intensive shipping activities are common in the region. Since a dike construction at Shihwa area was completed in 1994, sewage from Shihwa and Banweol industrial complexes has been accumulated in the manmade Lake Shihwa. In contrast, Namyang Bay is relatively less contaminated due to the much smaller scale of industrial complexes and less amounts of river run-o.
Sampling was limited to muddy areas to reduce the eects of grain size and/or organic carbon content to the residue levels of hydrophobic contaminants. Using a van Veen grab (0.1 m2), 62 surface sediment samples were collected from Kyeonggi Bay (n=54) in December 1995, Namyang Bay (n=5) in February 1996, and Lake Shihwa (n=3) in February 1996. For organochlorine analysis, 100 g sediments were collected from the top 3
K.T. Lee et al. / Environmental Pollution 114 (2001) 207±213
cm with a metal spoon and frozen under 20 C until analysis. Separate (100 g) samples were taken for grain size analysis and total organic carbon determination. 2.2. Chemical analysis Organochlorine pesticides in sediment samples were analyzed following a method of Ramesh et al. (1991). About 20±40 g of sediments were extracted for 1 h with 200 ml acetone. Sediment extracts were concentrated with KD (Kunderna Danish) concentrator. Concentrated extracts were treated with sulfuric acid for the clean-up. Copper granules (20±40 mesh) were used for the removal of elemental sulfur. Separation of organochlorine compounds was conducted by 12 g ¯orisil column. 120 ml of n-hexane was eluted as the ®rst fraction for the analysis of non-polar compounds like, HCB (hexachlorobenzene), trans-nonachlor, and p,p0 -DDE, and then 160 ml of mixed solution of n-hexane: dichloromethane (4:1) as the second fraction for the analysis of HCHs (hexachlorocyclohexane isomers), trans- and cis-chlordane, p,p0 -DDD, p,p0 -DDT. Quantitative analyses of OCPs in sediments were accomplished by gas chromatography equipped with a 63 Ni electron capture detector (Hewlett Packard 5890 Series II) using a DB-1 silica capillary column (J & W Scienti®c Co. Ltd., Folsom, California, USA: 30 m length0.25 mm inner diameter0.25 mm ®lm thickness). Helium was used as a carrier gas and nitrogen as a make-up gas. Recovery test was conducted by spiking a standard solution of organochlorines (50 mg in absolute quantity). T-HCHs were expressed as a sum of aHCH, b-HCH, and g-HCH. T-CHLs were de®ned as a sum of trans-chlordane, cis-chlordane, trans-nonachlor and cis-nonachlor. T-DDTs were considered as a sum of p,p0 -DDT, p,p0 -DDD and p,p0 -DDE. The triplicate recovery tests of T-HCHs, T-CHLs and T-DDTs yielded 9911%, 1004% and 90 7%, respectively. Detection limits of T-HCHs, T-CHLs and T-DDTs were determined to 0.150.13, 0.0650.08 and 0.0460.08 ng/ g dry weight, respectively. All data presented here were corrected for each blank.
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Grain size distribution was determined by dry- and wet-sieving method (Galehouse, 1971; Ingram, 1971). Gravel, sand, and mud (i.e. silt and clay) were fractionated by sieving 20 g of dry sediment. Mud fractions were subsequently separated by wet pipetting method. Total organic carbon (TOC) contents were determined by the method of Wong et al. (1993). One gram of freeze-dried sediment samples were acid-treated with 10% HCl for removal of carbonate carbon. After termination of acid reaction, samples were dried at 60 C. TOC were determined with CHNS analyzer (CHNS962, LECO). 3. Results and discussion 3.1. Contamination level of OCPs in sediments The levels of sediment contamination by OCPs in this study were shown in Table 1. The status of OCPs contamination in other countries from literatures was compared with this study (Table 2). The concentrations of T-HCHs in sediments from Kyeonggi Bay, Namyang Bay, and Lake Shihwa ranged <0.15±1.2, <0.15±0.67, and 0.53±2.4 ng/g, respectively. The highest concentration was found in Lake Siwha (S10; 2.4 ng/g). T-HCHs concentration showed overall similar level in most sites. Contamination levels of HCHs in the present study were close to those in Osaka Bay and were higher than those in coastal regions such as Casco Bay and Manukau Harbor as well as those in open sea such as Chukchi Sea, Bering Sea and Gulf of Alaska (Iwata et al., 1994a). The concentrations of T-CHLs in sediments from Kyeonggi Bay, Namyang Bay, and Shihwa were in the range of <0.065±130, <0.065±0.40, and 0.10±0.92 ng/g, respectively. The highest concentration of T-CHLs was measured in Kyeonggi Bay (K18; 130 ng/g). The Incheon North Harbor (INH) sites between K18 and K22 showed gradient of chlordane contamination. TCHLs residues as much as 130 ng/g at K18 decreased to 0.56 ng/g at K22 via 66 ng/g at K19 and 4.1 ng/g at
Table 1 Concentration range of OCPs in sediments from Kyeonggi Bay, Lake Shihwa, and Namyang Bay (ng/g dry weight) Kyeonggi Bay
Sample No. a
T-HCHs T-CHLsb T-DDTsc a b c
Lake Shihwa
Namyang Bay
INH
Out of INH
7
47
3
5
0.38±0.69 (0.58) 0.53±130 (29) 1.7±32 (9.4)
0.15±1.2 (0.44) 0.065±1.8 (1.6) 0.046±4.2 (0.70)
0.53±2.4 (1.3) 0.10±0.92 (0.45) 0.62±2.3 (1.4)
0.15±0.67 (0.46) <0.065±0.40 (0.3) <0.088±0.38 (0.28)
T-HCH (ng/g)=a-HCH+b-HCH+g-HCH. T-CHLs (ng/g dry wt)=trans-Chlordane+cis-Chlordane+trans-Nonachlor+cis-Nonachlor. T-DDTs (ng/g dry wt)=p,p0 -DDE+p,p0 -DDD+p,p0 -DDT.
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Table 2 Comparison of OCPs contamination in surface sediments collected from various region (ng/g dry weight) Location (year)
T-HCHs
T-CHLs
T-DDTs
Reference
Kyeonggi Bay (Dec. 1995) Namyang Bay (Feb. 1996) Lake Shiwha (Feb. 1996) San Francisco Bay, USA (Jan. 1992) Casco Bay, USA (Aug. 1991) Manukau Harbor, New Zealand (May 1990) Osaka Bay, Japan (May 1990) Lake Baikal, Russia (May 1992)
<0.19 1.2a <0.19 0.67a 0.59 2.4a NA <0.25 0.48a 0.03 0.5b 0.073 6.2a 0.019 0.12a
<0.065 130c <0.065 0.40c 0.10 0.92c <0.1 1.5c <0.25 4.9d <0.02 0.41d 0.66 2.1d <0.001 0.003e
<0.046 32f 0.088 0.38f 0.62 2.3f <0.1 9g <0.25 20f 0.07 22h 0.16 12I 0.014 2.7i
This study This study This study Pereira et al. (1994) Kennicutt et al. (1994) Holland et al. (1993) Tanabe et al. (1991); Iwata et al. (1994b) Iwata et al. (1995)
a
Sum of a-, b- and g-HCH. g-isomer only. c Sum of trans-chlordane, cis-chlordane, trans-nonachlor and cis-nonachlor. d Sum of trans-chlordane and cis-chlordane. e Sum of trans-chlordane, cis-chlordane and trans-nonachlor. f Sum of o,p0 -, p,p0 -DDE, o,p0 -, p,p0 -DDD, and o,p0 -, p,p0 -DDT. g Sum of p,p0 -DDE, p,p0 -DDD, and o,p0 -, p,p0 -DDT. h Sum of p,p0 -DDE, o,p0 -, p,p0 -DDD, and o,p0 -, p,p0 -DDT. i Sum of p,p0 -DDE, p,p0 -DDD, and p,p0 -DDT. b
K20. T-CHLs concentrations inside INH showed one to two orders of magnitude higher than those of other sites even after normalization with total organic carbon content, This implies that the contamination source is near shore in INH. About 21% of the sites were over 0.5 ng/g which was suggested by Long et al. (1995) as a ERL (eect range low; the lower 10th percentile of the eects data for each chemical). The concentrations of 130 ng/g at K18 and 66 ng/g at K19 were higher than sediment safety levels of 4.9 ng/g derived from FDA action level (regulatory limit for contaminant residue in edible ®sh for use in interstate commerce; 300 ng/g) by Chapman (1987), and 6 ng/g as a value of ERM (eect range median; the 50th percentile of the eects data for each chemical) suggested by Long et al. (1995). Highest concentrations of other contaminants such as PCBs and methyl mercury in Kyeonggi Bay were reported at the same K18 and K19 samples (Lee et al., 1998, 2001). The results of chemical analyses implied that K18 and K19 were the most contaminated sites in Kyeonggi Bay. The concentrations of T-DDTs in sediments from Kyeonggi Bay, Namyang Bay, and Lake Shihwa ranged <0.048±32, 0.088±0.38 and 0.62±2.3, respectively. The highest concentration was observed in Kyeonggi Bay (K19; 32 ng/g). T-DDTs residues showed the similar declining trend by recording the concentration gradient of 32 and 19 ng/g at K19 and K18, respectively, 5.1±1.9 ng/g between K20 and K22 in mid-part and <1 ng/g at most outer part from INH. The concentrations of TDDTs at K18 and K19 showed one order of magnitude higher than other sites even after normalization with total organic carbon contents. The level of T-DDTs residues in the present study showed a comparable contamination with Casco Bay, but much lower than the heavily polluted Palos Verdes, California which
was measured up to 100 mg/g. The concentration of K19 (32 ng/g) and K18 (19 ng/g) were close to ERM. About 21% of the sites studied were between ERL (1.58 ng/g) and ERM (46.1 ng/g) and others were less than ERL. 3.2. Spatial distribution of OCPs The kinetic behavior of hydrophobic organic contaminants such as HCHs, CHLs, DDTs and PCBs have been shown to be related by total organic carbon contents in sediments and by lipid contents in organisms (Karickho, 1981; JaeÂ, 1991). The concentrations of T-CHLs and T-DDTs in the sediments of Kyeonggi Bay and nearby areas were strongly correlated with TOC content (r2=0.60 and 0.57, P<0.05, respectively), while no correlation was found with mud content and grain size. However, distribution of T-HCHs didn't show any correlation with TOC contents possibly due to less lipophilic and more volatile nature of HCHs relative to the other compounds. In addition, distribution pattern of T-HCHs was dierent from T-CHLs and T-DDTs residues, while T-CHLs levels were signi®cantly correlated with T-DDTs residues. In our case, relationship between environmental factors and OCPs concentrations is well expressed by multivariate statistics such as principal component analysis (PCA). Fig. 2 shows the plot of PCA. Principal components 1 (PC1) and 2 (PC2) account for 59 and 26% of the total variability, respectively. PC1 is related with mud content and mean grain size distribution while PC2 is related with T-CHLs, T-DDTs, and TOC. Contaminants were separated according to the dierent contribution of PC1 and PC2. T-CHLs and T-DDTs were grouped together while T-HCH was separated from other contaminants.
K.T. Lee et al. / Environmental Pollution 114 (2001) 207±213
Spatial distribution of T-HCHs showed a uniform pattern of contamination below ng/g level in overall sediment samples. This fact indicates no signi®cant contamination by HCHs compounds in study area or no accumulative property of HCHs in sediments due to the dispersible nature of HCHs. This lack of contamination may be partially explained by the shorter half life than other organochlorine compounds (Sammuel and Pillai, 1991; Singh, 1993).
Fig. 2. Principal component analysis (PCA). TOC means total organic carbon. Mud expresses the sum of silt and clay contents. Mz represents mean grain size.
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b-HCH was present in most of the sediments. Concentration of b-HCH in technical HCHs range from 5 to 12%. However, b-HCH was found in much larger amounts relative to total HCHs in sediments (45% in Lake Shihwa, 26% in Namyang Bay, and 33% in Kyeonggi Bay). a-HCH can be easily dissipated from sediments due to the highest Henry's Law constant value though it has the most quantity in technical HCHs. g-HCH has higher water solubility and Henry's Law constant value than b-isomer. b-isomer has lower water solubility and Henry's Law constant value compared to a- and g-isomer. Relatively higher percentage of b-isomer in sediments even though lower percentage of b-isomer composition in technical HCH implied that b-HCH was the most persistent isomer among the HCH compounds. The distribution patterns of organochlorine pesticides were investigated by using isomer or metabolite ratio. The similar spatial distribution of T-HCHs residues, the similar a/g ratios, and the b-isomer dominance in sediments imply that HCH isomers are dissipated very fast in the environment during transportation and sedimentation. This suggests that the behavior of HCH compounds in the environment may be explained by volatility and water solubility rather than adsorption to organic matter. Other transport processes such as hydrologic transport by river discharge and input through ground water might also aect the ®nal composition of HCH compounds in sediments. The distribution of T-CHLs showed a distinctive gradient from the likely source of chlordane, Site K18, to o-shore sites (Fig. 3). In addition to the highest concentration at K18, the composition of transchlordane/cis-chlordane/trans-nonachlor/cis-nonachlor
Fig. 3. Changes in T-CHLs concentrations and t/c ratios with distance from INH.
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in sediments at K18 (1.0:0.89:0.67:0.18) were similar to those in technical chlordane (1.0:0.99:0.64:0.31), suggesting a recent input of chlordane into this area. Chlordane compounds in sediments far o the source showed relative dierences in compositions and in concentrations. Trans/cis-chlordane ratios (t/c ratio) increased with distance from K18, while the concentrations of T-CHLs decreased with distance. The t/c ratios in all the sediments were found to be over 1.0 which corresponds to the t/c ratio in technical mixture, indicating trans-chlordane might be slightly more persistent compound in sediments when compared to cis-chlordane. A similar predominance of trans-chlordane in surface sediments was observed (Kelly and Campbell, 1995). Higher concentrations of T-DDTs were found in coastal sediments from the INH and Han River estuary than in other sites. Such a gradient suggests that the major input of DDT pollution is from these areas. The DDT contamination source can be traced by the relative residues of p,p0 -DDT to its metabolites. Technical grade DDT, typically 80±85% p,p0 -DDT 15±20% o,p0 -DDT. p,p0 -DDT degrad to p,p0 -DDE and p,p0 -DDD in the aerobic and anaerobic condition, respectively (Metcalf, 1973). High compositional percentage of p,p0 -DDT can be maintained by continuous input of technical DDTs. If there is no more input of technical DDTs, the compositional percentage of p,p0 -DDT will be gradually reduced and those of DDT metabolites will be gradually increased. Therefore, the ratio of p,p0 -DDT to T-DDTs can be used as an indicator to identify a recent input of technical DDT. High ratio indicates a recent input of technical DDT while low ratio means no recent input. p,p0 -DDT residue in sediments was highest at K19, occupying 55% of total residues, 32 ng/g. The highest TDDTs concentration and the highest p,p0 -DDT/T-DDTs ratio also supports that INH is in the vicinity of the source. The T-DDTs concentrations and p,p0 -DDT/TDDTs ratios decreased with distance from Site K19 to o-shore areas. p,p0 -DDE and p,p0 -DDD were dominant isomers in o shore sediments (very low p,p0 -DDT/TDDTs ratio), and residues of p,p0 -DDD were slightly higher than those of p,p0 -DDE, suggesting the aging of p,p0 -DDT to other DDT metabolites such as p,p0 -DDD and p,p0 -DDE in the sediments. Acknowledgements This work was ®nancially supported from National Institute of Environmental Research (NIER), Ministry of Environment, Korea, SORGBIOS 98-2000 (Sediment Organic Compound Bioassay Study). This research was also funded partly by AIEJ (Association of International Eduction, Japan) short-term Student Exchange Promotion Program Scholarship awarded to Kyu-Tae Lee.
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Distribution of organochlorine pesticides in sediments from Kyeonggi Bay and nearby areas, Korea K.T. Lee a, S. Tanabe b, C.H. Koh a,* a
School of Earth and Environmental Sciences (Oceanography program), College of Natural Sciences, Seoul National University, Seoul 151-742, South Korea b Department of Environment Conservation, Ehime University, Tarumi 3-5-7, Matsuyama 790, Japan Received 7 June 2000; accepted 13 October 2000
``Capsule'': The geographic distribution of organochlorine pesticides in sediments in Kyeonggi Bay, Korea was determined. Abstract The residues of oragnochlorine pesticides (OCPs) in 62 sediments from Kyeonggi Bay and nearby areas in the west coast of Korea were determined. The concentrations of chlordanes (CHLs) and DDTs showed a distinctive gradient of contamination between inner and outer sites of Incheon North Harbor (INH), whereas hexachlorocyclohexanes (HCHs) were uniformly distributed at most sites studied. The distribution of CHLs and DDTs was strongly correlated with total organic carbon contents in sediments while HCH residue levels were independent. Relationship between contaminant's concentration and environmental factors was analyzed by principal component analysis. Distribution patterns of T-CHLs, T-DDTs, and TOC were similar while those of T-HCHs, mud content, and grain size were similar. The notable contamination by CHLs and DDTs was found in INH where these levels were one or two orders of magnitude higher than other sites. The dominant OCPs in sediments were b-HCH among HCH compounds, trans-chlordane among CHL compounds, and p,p0 -DDD among DDT compounds. The higher concentrations and compositional pattern of OCPs in INH sediments indicate that INH is in the vicinity of the source. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: Organochlorine pesticides (OCPs); Korean sediments; Principal Component Analysis; Isomer or metabolite ratio
1. Introduction Organochlorine pesticides (OCPs) such as hexachlorocyclohexanes (HCHs), chlordanes (CHLs), and DDTs were known to have bioaccumulative nature because of their high lipophilicity and persistency (Tanabe and Tatsukawa, 1992). In the aquatic environment, organochlorine compounds are removed from the water column and adsorbed on the particulate matters due to their high anity for organic matter, and ®nally accumulated in sediments, which may play a role as a secondary contamination source. These contaminants also accumulate in the sediment-dwelling organisms which may be transferred to higher trophic levels through the food chain. Organochlorine residues from
* Corresponding author. Tel.: +82-2-880-6750; fax: +82-2-8720311. E-mail address: [email protected] (C.H. Koh).
the various regions have been well reported (Tanabe et al., 1983; DouAbul et al., 1988; Sericano et al., 1990; Thao et al., 1993; Iwata et al., 1994a; Morrison et al., 1996; Tate and Heiny, 1996), however, information on the occurrence of OCPs in Korea is scarce. As a component of integrated assessment of environmental health on the west coast of Korea, this work was designed to determine the geographic distribution of selected OCP contaminants on the west coast of Korea. 2. Materials and methods 2.1. Sample collection The sediment samples were collected from Kyeonggi Bay, Namyang Bay and Lake Shihwa on the west coast of Korea (Fig. 1). Kyeonggi Bay with tide dierence as high as 8 m is located on the west coast of Korea. Incheon Harbor in Kyeonggi Bay is highly polluted as
0269-7491/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S0269-7491(00)00217-7
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Fig. 1. A map of study areas and sampling sites.
there are many factories located in the vicinity. In addition, intensive shipping activities are common in the region. Since a dike construction at Shihwa area was completed in 1994, sewage from Shihwa and Banweol industrial complexes has been accumulated in the manmade Lake Shihwa. In contrast, Namyang Bay is relatively less contaminated due to the much smaller scale of industrial complexes and less amounts of river run-o.
Sampling was limited to muddy areas to reduce the eects of grain size and/or organic carbon content to the residue levels of hydrophobic contaminants. Using a van Veen grab (0.1 m2), 62 surface sediment samples were collected from Kyeonggi Bay (n=54) in December 1995, Namyang Bay (n=5) in February 1996, and Lake Shihwa (n=3) in February 1996. For organochlorine analysis, 100 g sediments were collected from the top 3
K.T. Lee et al. / Environmental Pollution 114 (2001) 207±213
cm with a metal spoon and frozen under 20 C until analysis. Separate (100 g) samples were taken for grain size analysis and total organic carbon determination. 2.2. Chemical analysis Organochlorine pesticides in sediment samples were analyzed following a method of Ramesh et al. (1991). About 20±40 g of sediments were extracted for 1 h with 200 ml acetone. Sediment extracts were concentrated with KD (Kunderna Danish) concentrator. Concentrated extracts were treated with sulfuric acid for the clean-up. Copper granules (20±40 mesh) were used for the removal of elemental sulfur. Separation of organochlorine compounds was conducted by 12 g ¯orisil column. 120 ml of n-hexane was eluted as the ®rst fraction for the analysis of non-polar compounds like, HCB (hexachlorobenzene), trans-nonachlor, and p,p0 -DDE, and then 160 ml of mixed solution of n-hexane: dichloromethane (4:1) as the second fraction for the analysis of HCHs (hexachlorocyclohexane isomers), trans- and cis-chlordane, p,p0 -DDD, p,p0 -DDT. Quantitative analyses of OCPs in sediments were accomplished by gas chromatography equipped with a 63 Ni electron capture detector (Hewlett Packard 5890 Series II) using a DB-1 silica capillary column (J & W Scienti®c Co. Ltd., Folsom, California, USA: 30 m length0.25 mm inner diameter0.25 mm ®lm thickness). Helium was used as a carrier gas and nitrogen as a make-up gas. Recovery test was conducted by spiking a standard solution of organochlorines (50 mg in absolute quantity). T-HCHs were expressed as a sum of aHCH, b-HCH, and g-HCH. T-CHLs were de®ned as a sum of trans-chlordane, cis-chlordane, trans-nonachlor and cis-nonachlor. T-DDTs were considered as a sum of p,p0 -DDT, p,p0 -DDD and p,p0 -DDE. The triplicate recovery tests of T-HCHs, T-CHLs and T-DDTs yielded 9911%, 1004% and 90 7%, respectively. Detection limits of T-HCHs, T-CHLs and T-DDTs were determined to 0.150.13, 0.0650.08 and 0.0460.08 ng/ g dry weight, respectively. All data presented here were corrected for each blank.
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Grain size distribution was determined by dry- and wet-sieving method (Galehouse, 1971; Ingram, 1971). Gravel, sand, and mud (i.e. silt and clay) were fractionated by sieving 20 g of dry sediment. Mud fractions were subsequently separated by wet pipetting method. Total organic carbon (TOC) contents were determined by the method of Wong et al. (1993). One gram of freeze-dried sediment samples were acid-treated with 10% HCl for removal of carbonate carbon. After termination of acid reaction, samples were dried at 60 C. TOC were determined with CHNS analyzer (CHNS962, LECO). 3. Results and discussion 3.1. Contamination level of OCPs in sediments The levels of sediment contamination by OCPs in this study were shown in Table 1. The status of OCPs contamination in other countries from literatures was compared with this study (Table 2). The concentrations of T-HCHs in sediments from Kyeonggi Bay, Namyang Bay, and Lake Shihwa ranged <0.15±1.2, <0.15±0.67, and 0.53±2.4 ng/g, respectively. The highest concentration was found in Lake Siwha (S10; 2.4 ng/g). T-HCHs concentration showed overall similar level in most sites. Contamination levels of HCHs in the present study were close to those in Osaka Bay and were higher than those in coastal regions such as Casco Bay and Manukau Harbor as well as those in open sea such as Chukchi Sea, Bering Sea and Gulf of Alaska (Iwata et al., 1994a). The concentrations of T-CHLs in sediments from Kyeonggi Bay, Namyang Bay, and Shihwa were in the range of <0.065±130, <0.065±0.40, and 0.10±0.92 ng/g, respectively. The highest concentration of T-CHLs was measured in Kyeonggi Bay (K18; 130 ng/g). The Incheon North Harbor (INH) sites between K18 and K22 showed gradient of chlordane contamination. TCHLs residues as much as 130 ng/g at K18 decreased to 0.56 ng/g at K22 via 66 ng/g at K19 and 4.1 ng/g at
Table 1 Concentration range of OCPs in sediments from Kyeonggi Bay, Lake Shihwa, and Namyang Bay (ng/g dry weight) Kyeonggi Bay
Sample No. a
T-HCHs T-CHLsb T-DDTsc a b c
Lake Shihwa
Namyang Bay
INH
Out of INH
7
47
3
5
0.38±0.69 (0.58) 0.53±130 (29) 1.7±32 (9.4)
0.15±1.2 (0.44) 0.065±1.8 (1.6) 0.046±4.2 (0.70)
0.53±2.4 (1.3) 0.10±0.92 (0.45) 0.62±2.3 (1.4)
0.15±0.67 (0.46) <0.065±0.40 (0.3) <0.088±0.38 (0.28)
T-HCH (ng/g)=a-HCH+b-HCH+g-HCH. T-CHLs (ng/g dry wt)=trans-Chlordane+cis-Chlordane+trans-Nonachlor+cis-Nonachlor. T-DDTs (ng/g dry wt)=p,p0 -DDE+p,p0 -DDD+p,p0 -DDT.
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Table 2 Comparison of OCPs contamination in surface sediments collected from various region (ng/g dry weight) Location (year)
T-HCHs
T-CHLs
T-DDTs
Reference
Kyeonggi Bay (Dec. 1995) Namyang Bay (Feb. 1996) Lake Shiwha (Feb. 1996) San Francisco Bay, USA (Jan. 1992) Casco Bay, USA (Aug. 1991) Manukau Harbor, New Zealand (May 1990) Osaka Bay, Japan (May 1990) Lake Baikal, Russia (May 1992)
<0.19 1.2a <0.19 0.67a 0.59 2.4a NA <0.25 0.48a 0.03 0.5b 0.073 6.2a 0.019 0.12a
<0.065 130c <0.065 0.40c 0.10 0.92c <0.1 1.5c <0.25 4.9d <0.02 0.41d 0.66 2.1d <0.001 0.003e
<0.046 32f 0.088 0.38f 0.62 2.3f <0.1 9g <0.25 20f 0.07 22h 0.16 12I 0.014 2.7i
This study This study This study Pereira et al. (1994) Kennicutt et al. (1994) Holland et al. (1993) Tanabe et al. (1991); Iwata et al. (1994b) Iwata et al. (1995)
a
Sum of a-, b- and g-HCH. g-isomer only. c Sum of trans-chlordane, cis-chlordane, trans-nonachlor and cis-nonachlor. d Sum of trans-chlordane and cis-chlordane. e Sum of trans-chlordane, cis-chlordane and trans-nonachlor. f Sum of o,p0 -, p,p0 -DDE, o,p0 -, p,p0 -DDD, and o,p0 -, p,p0 -DDT. g Sum of p,p0 -DDE, p,p0 -DDD, and o,p0 -, p,p0 -DDT. h Sum of p,p0 -DDE, o,p0 -, p,p0 -DDD, and o,p0 -, p,p0 -DDT. i Sum of p,p0 -DDE, p,p0 -DDD, and p,p0 -DDT. b
K20. T-CHLs concentrations inside INH showed one to two orders of magnitude higher than those of other sites even after normalization with total organic carbon content, This implies that the contamination source is near shore in INH. About 21% of the sites were over 0.5 ng/g which was suggested by Long et al. (1995) as a ERL (eect range low; the lower 10th percentile of the eects data for each chemical). The concentrations of 130 ng/g at K18 and 66 ng/g at K19 were higher than sediment safety levels of 4.9 ng/g derived from FDA action level (regulatory limit for contaminant residue in edible ®sh for use in interstate commerce; 300 ng/g) by Chapman (1987), and 6 ng/g as a value of ERM (eect range median; the 50th percentile of the eects data for each chemical) suggested by Long et al. (1995). Highest concentrations of other contaminants such as PCBs and methyl mercury in Kyeonggi Bay were reported at the same K18 and K19 samples (Lee et al., 1998, 2001). The results of chemical analyses implied that K18 and K19 were the most contaminated sites in Kyeonggi Bay. The concentrations of T-DDTs in sediments from Kyeonggi Bay, Namyang Bay, and Lake Shihwa ranged <0.048±32, 0.088±0.38 and 0.62±2.3, respectively. The highest concentration was observed in Kyeonggi Bay (K19; 32 ng/g). T-DDTs residues showed the similar declining trend by recording the concentration gradient of 32 and 19 ng/g at K19 and K18, respectively, 5.1±1.9 ng/g between K20 and K22 in mid-part and <1 ng/g at most outer part from INH. The concentrations of TDDTs at K18 and K19 showed one order of magnitude higher than other sites even after normalization with total organic carbon contents. The level of T-DDTs residues in the present study showed a comparable contamination with Casco Bay, but much lower than the heavily polluted Palos Verdes, California which
was measured up to 100 mg/g. The concentration of K19 (32 ng/g) and K18 (19 ng/g) were close to ERM. About 21% of the sites studied were between ERL (1.58 ng/g) and ERM (46.1 ng/g) and others were less than ERL. 3.2. Spatial distribution of OCPs The kinetic behavior of hydrophobic organic contaminants such as HCHs, CHLs, DDTs and PCBs have been shown to be related by total organic carbon contents in sediments and by lipid contents in organisms (Karickho, 1981; JaeÂ, 1991). The concentrations of T-CHLs and T-DDTs in the sediments of Kyeonggi Bay and nearby areas were strongly correlated with TOC content (r2=0.60 and 0.57, P<0.05, respectively), while no correlation was found with mud content and grain size. However, distribution of T-HCHs didn't show any correlation with TOC contents possibly due to less lipophilic and more volatile nature of HCHs relative to the other compounds. In addition, distribution pattern of T-HCHs was dierent from T-CHLs and T-DDTs residues, while T-CHLs levels were signi®cantly correlated with T-DDTs residues. In our case, relationship between environmental factors and OCPs concentrations is well expressed by multivariate statistics such as principal component analysis (PCA). Fig. 2 shows the plot of PCA. Principal components 1 (PC1) and 2 (PC2) account for 59 and 26% of the total variability, respectively. PC1 is related with mud content and mean grain size distribution while PC2 is related with T-CHLs, T-DDTs, and TOC. Contaminants were separated according to the dierent contribution of PC1 and PC2. T-CHLs and T-DDTs were grouped together while T-HCH was separated from other contaminants.
K.T. Lee et al. / Environmental Pollution 114 (2001) 207±213
Spatial distribution of T-HCHs showed a uniform pattern of contamination below ng/g level in overall sediment samples. This fact indicates no signi®cant contamination by HCHs compounds in study area or no accumulative property of HCHs in sediments due to the dispersible nature of HCHs. This lack of contamination may be partially explained by the shorter half life than other organochlorine compounds (Sammuel and Pillai, 1991; Singh, 1993).
Fig. 2. Principal component analysis (PCA). TOC means total organic carbon. Mud expresses the sum of silt and clay contents. Mz represents mean grain size.
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b-HCH was present in most of the sediments. Concentration of b-HCH in technical HCHs range from 5 to 12%. However, b-HCH was found in much larger amounts relative to total HCHs in sediments (45% in Lake Shihwa, 26% in Namyang Bay, and 33% in Kyeonggi Bay). a-HCH can be easily dissipated from sediments due to the highest Henry's Law constant value though it has the most quantity in technical HCHs. g-HCH has higher water solubility and Henry's Law constant value than b-isomer. b-isomer has lower water solubility and Henry's Law constant value compared to a- and g-isomer. Relatively higher percentage of b-isomer in sediments even though lower percentage of b-isomer composition in technical HCH implied that b-HCH was the most persistent isomer among the HCH compounds. The distribution patterns of organochlorine pesticides were investigated by using isomer or metabolite ratio. The similar spatial distribution of T-HCHs residues, the similar a/g ratios, and the b-isomer dominance in sediments imply that HCH isomers are dissipated very fast in the environment during transportation and sedimentation. This suggests that the behavior of HCH compounds in the environment may be explained by volatility and water solubility rather than adsorption to organic matter. Other transport processes such as hydrologic transport by river discharge and input through ground water might also aect the ®nal composition of HCH compounds in sediments. The distribution of T-CHLs showed a distinctive gradient from the likely source of chlordane, Site K18, to o-shore sites (Fig. 3). In addition to the highest concentration at K18, the composition of transchlordane/cis-chlordane/trans-nonachlor/cis-nonachlor
Fig. 3. Changes in T-CHLs concentrations and t/c ratios with distance from INH.
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in sediments at K18 (1.0:0.89:0.67:0.18) were similar to those in technical chlordane (1.0:0.99:0.64:0.31), suggesting a recent input of chlordane into this area. Chlordane compounds in sediments far o the source showed relative dierences in compositions and in concentrations. Trans/cis-chlordane ratios (t/c ratio) increased with distance from K18, while the concentrations of T-CHLs decreased with distance. The t/c ratios in all the sediments were found to be over 1.0 which corresponds to the t/c ratio in technical mixture, indicating trans-chlordane might be slightly more persistent compound in sediments when compared to cis-chlordane. A similar predominance of trans-chlordane in surface sediments was observed (Kelly and Campbell, 1995). Higher concentrations of T-DDTs were found in coastal sediments from the INH and Han River estuary than in other sites. Such a gradient suggests that the major input of DDT pollution is from these areas. The DDT contamination source can be traced by the relative residues of p,p0 -DDT to its metabolites. Technical grade DDT, typically 80±85% p,p0 -DDT 15±20% o,p0 -DDT. p,p0 -DDT degrad to p,p0 -DDE and p,p0 -DDD in the aerobic and anaerobic condition, respectively (Metcalf, 1973). High compositional percentage of p,p0 -DDT can be maintained by continuous input of technical DDTs. If there is no more input of technical DDTs, the compositional percentage of p,p0 -DDT will be gradually reduced and those of DDT metabolites will be gradually increased. Therefore, the ratio of p,p0 -DDT to T-DDTs can be used as an indicator to identify a recent input of technical DDT. High ratio indicates a recent input of technical DDT while low ratio means no recent input. p,p0 -DDT residue in sediments was highest at K19, occupying 55% of total residues, 32 ng/g. The highest TDDTs concentration and the highest p,p0 -DDT/T-DDTs ratio also supports that INH is in the vicinity of the source. The T-DDTs concentrations and p,p0 -DDT/TDDTs ratios decreased with distance from Site K19 to o-shore areas. p,p0 -DDE and p,p0 -DDD were dominant isomers in o shore sediments (very low p,p0 -DDT/TDDTs ratio), and residues of p,p0 -DDD were slightly higher than those of p,p0 -DDE, suggesting the aging of p,p0 -DDT to other DDT metabolites such as p,p0 -DDD and p,p0 -DDE in the sediments. Acknowledgements This work was ®nancially supported from National Institute of Environmental Research (NIER), Ministry of Environment, Korea, SORGBIOS 98-2000 (Sediment Organic Compound Bioassay Study). This research was also funded partly by AIEJ (Association of International Eduction, Japan) short-term Student Exchange Promotion Program Scholarship awarded to Kyu-Tae Lee.
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