Organochlorine Pesticides In Surface Sediments Research Articles

Polychlorinated biphenyls and organochlorine pesticides in surface sediments from river networks, South Korea: Spatial distribution, source identification, and ecological risks.

In this study, the nationwide monitoring of 65 polychlorinated biphenyls (PCBs) and 23 organochlorine pesticides (OCPs) in surface sediments was conducted at 77 sites in river networks in South Korea. The concentrations of ∑PCBs were relatively high in industrial sites (0.0297-138 ng/g dry weight (dw); mean 15.1 ng/g dw; median 5.44 ng/g dw), followed by industrial and agricultural (not detected (ND)-15.2 ng/g dw; mean 1.23 ng/g dw; median 0.513 ng/g dw), other sites (0.0369-0.209 ng/g dw; mean 0.116 ng/g dw; median 0.101 ng/g dw), and agricultural (0.0119-0.359 ng/g dw; mean 0.117 ng/g dw; median 0.0476 ng/g dw). The distribution and composition of PCBs in sediments are affected by past use of commercial products, atmospheric deposition, wastewater effluents, and manufacturing processes. The concentrations of ∑OCPs in industrial sites ranged from 0.0587 to 8.70 ng/g dw (mean 1.85 ng/g dw; median 0.989 ng/g dw), followed by industrial and agricultural (ND-8.54 ng/g dw; mean 0.739 ng/g dw; median 0.343 ng/g dw), other sites (0.0247-0.143 ng/g dw; mean 0.0939 ng/g dw; median 0.114 ng/g dw), and agricultural (0.00838-0.931 ng/g dw; mean 0.232 ng/g dw; median 0.0752 ng/g dw). Hexachlorobenzene and pentachlorobenzene are unintentionally generated in industries and combustion processes. Dichlorodiphenyltrichloroethanes and chlordane were dominantly distributed by historical use, whereas recent inputs (i.e., long-range transport and atmospheric deposition) were related to aldrin, heptachlor, and hexachlorocyclohexanes. The ecological risks determined by the sediment quality guidelines and mean probable effect level quotients were acceptable, except at two sites.

Baseline occurrence, distribution and sources of PAHs, TPH, and OCPs in surface sediments in Gorgan Bay, Iran

Baseline polycyclic aromatic hydrocarbons (PAHs), total petroleum hydrocarbons (TPH) and organochlorine pesticides (OCPs) in surface sediments were measured in Gorgan Bay, Iran. Total PAHs, TPH, and OCPs concentrations ranged between 13.70 and 23.68 ng g−1, 2.97 to 11.51 μg g−1 dry weight, and below detection to 1.41 ng g−1, respectively. Benzo [k] fluoranthene and anthracene had the highest (BkF; 19.77 ± 0.08 ng g−1), and lowest (Ant; 4.38 ± 1.72 ng g−1) individual PAH concentrations, respectively. The most abundant OCPs were β-Endosulfan, followed by methoxychlor and endrin. PAH isomeric ratios in sediments revealed that contamination originated from mixed sources, with a strong indication of pyrogenic sources. Ecological risk assessments based on sediment quality guidelines (SQGs) suggested that individual PAHs and OCPs posed low ecological risks in Gorgan Bay.

Distribution of organochlorine pesticides in sediment cores from the Bizerte Lagoon (Tunisia)

ABSTRACT The present study investigates the vertical distribution of organochlorine pesticides (OCPs), in two sediment cores collected from the Bizerte Lagoon. The sediment core (SC1) is located in the mouth of the channel connecting the lagoon to the Mediterranean Sea and characterized by the industrial and urban activities of zone A and B. The sediment core (SC2) is situated in the zone D known by its intensive metallurgy and naval construction activities. The OCPs concentrations ranged from 26.98 ± 0.04 ng g−1 found at 3 cm depth and 10.23 ± 0.02 ng g−1 at 6 cm depth in SC1, and varied between 11.77 ± 0.11 ng g−1 at 9 cm depth and 1.47 ± 0.02 ng g−1 at 20 cm depth in SC2. The results showed that the SC2 had lower levels of OCPs and total organic carbon (TOC) compared to SC1. Generally, OCPs and TOC % decreased with depth along the two SCs profiles. The different categories of OCPs were in the following order: DDTs> Aldrin >HCB. The principal OCPs in deeper sediment layers were aldrin, endrin, and ∑DDTs for SC1 in addition to HCB and aldrin for SC2. The predominant OCPs in surface sediments were dieldrin, endrin and ∑DDTs for SC1, and HCB, heptachlor, aldrin and ∑DDTs for SC2. Different profiles were observed making evident that the levels of these pollutants depend strongly on anthropological discharges from industrial, urban and farming sources. The temporal trends of OCPs were influenced by their different historical usages, different properties or different degradation conditions in the environment. DDTs was mainly due to historical residue and biodegradation occurred in aerobic conditions. According to the established guidelines for sediment quality, levels of OCPs at most of the SCs layers were below class criteria. However, levels of DDE in SC1 could cause biological damage and ecotoxicological risk.

Concentration, distribution and sources of perfluoroalkyl substances and organochlorine pesticides in surface sediments of the northern Bering Sea, Chukchi Sea and adjacent Arctic Ocean

Perfluoroalkyl substances (PFAS) and organochlorine pesticides (OCPs) in surface sediments were investigated from the Bering Sea, the Chukchi Sea and adjacent Arctic Ocean in 2010. Total concentrations (dry weight) of Σ14PFAS in surface sediments (0.85 ± 0.22 ng g−1) of the Bering Sea were lower than that in the Chukchi Sea and adjacent Arctic Ocean (1.27 ± 0.53 ng g−1). Perfluoro-butanoic acid (PFBS) and perfluoro-octanoic acid (PFOA) were the dominant PFAS in these areas. The concentrations of Σ15OCPs in the sediment of the Bering Sea (13.00 ± 6.17 ng g−1) was slightly higher than that in the Chukchi and Arctic Ocean (12.05 ± 2.27 ng g−1). The most abundant OCPs were hexachlorocyclohexane isomers (HCHs) and dichlorodiphenyltrichloroethane (DDT) and its metabolites. The composition patterns of HCHs and DDTs indicated that they were mainly derived from the early residues via river runoff. Increasing trends of PFAS, HCHs and DDTs in surface sediments from the Bering Sea to the Arctic Ocean were found, indicating oceanic transport. In summary, the concentrations of OCPs were orders of magnitude greater than the observed PFAS concentrations, and the concentrations of PFAS and OCPs in surface sediments from the Bering Sea to the Chukchi Sea and adjacent Arctic Ocean are at the low to moderate levels by comparing with other coastal and marine sediments worldwide.

The legacy of man-made organic compounds in surface sediments of Pina Sound and Suape Estuary, northeastern Brazil

Abstract Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) are man-made organic chemicals that have adverse effects on aquatic organisms, sometimes altering ecosystem functioning with potential consequences for the coastal carbon cycle. This study assessed PCBs and OCPs in surface sediments of two estuaries with distinct historical land use on the coast of Pernambuco, northeastern Brazil. OCPs such as HCB, aldrin, dieldrin, isodrin, mirex, methoxychlor, endosulfans (α- and β-isomers), HCHs (α-, β-, γ- and δ-isomers) and chlordane-related compounds were below their respective limits of detection in all samples. Mean levels of PCBs in Pina Sound and Suape Estuary were 4.37 and 0.94 ng g-1 dry weight (dw), respectively. Average concentrations of DDTs in those same estuaries were 5.24 and 0.42 ng g-1 dw, respectively. No significant correlations were found between mud and contaminants (either PCBs or DDTs) at Pina Sound. In contrast, PCBs were significantly associated with mud at Suape Estuary. The greater contamination found at Pina Sound is consistent with land use of the urban, densely populated city of Recife. Residues of DDTs found in sediments of both estuaries reflect past local usage. Occasional adverse biological effects may be expected due to the levels of DDTs at several sites in Pina Sound. Lower levels of chemicals such as PCBs in the newly industrialized Suape Estuary suggest that a similarly low impact of legacy pollutants may be expected for future industrial enterprises around the world.

Depth-distribution, possible sources, and toxic risk assessment of organochlorine pesticides (OCPs) in different river sediment cores affected by urbanization and reclamation in a Chinese delta

Sediment cores were collected in urban (0–50 cm), rural (0–40 cm) and reclamation-affected river (0–40 cm) environments in the Pearl River Delta. Concentrations of 16 organochlorine pesticides (OCPs) were determined in all collected samples to identify the depth-distribution, possible sources and ecotoxicological risks of OCPs in river sediments affected by urbanization and reclamation in a Chinese delta. The results showed that the top 10 cm of rural river sediments had slightly lower concentrations of the 16 OCPs compared to urban and reclamation-affected rivers, whereas the 30–40 cm sediment layers in the rural river showed higher levels of the 16 OCPs. However, higher OCPs levels were observed in the 20–30 cm sediment layers in the urban river than in the rural and reclamation-affected rivers. The principal OCPs in most deeper sediment layers were hexachlorobezene (HCB), the combination of aldrin, endrin and dieldrin (ΣDRINs) and the combination of α-HCH, β-HCH and γ-HCH (ΣHCHs). The predominant OCPs in surface sediments were HCB, ΣDRINs and the combination of p,p’-DDD, o,p’-DDT, p,p’-DDT and p,p’-DDE (ΣDDTs). Generally, OCP concentrations decreased with depth along sediment profiles at most sampling sites in the three types of rivers. The source analyses indicated that some sampling sites were still suffering from the recent use of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs) and aldrin. According to the soil quality thresholds of China, the levels of HCHs and DDTs at most sampling sites were below class Ⅰ criteria. Based on the sediment quality guideline quotient (SQGQ), the combined ecotoxicological risk of OCPs (γ-HCH, dieldrin, p,p'-DDD, p,p'-DDE and p,p'-DDT) in surface sediments (0–10 cm) was higher than deeper sediments, and the rural river sediments exhibited a higher combined ecotoxicological risk than the sediments in urban and reclamation-affected rivers.

Ecological and health risk assessment of PAHs, OCPs, and PCBs in Taihu Lake basin

With rapid economic, agricultural, and industrial development in the Taihu Lake basin, persistent organic pollutants (POPs) have become a major concern in recent years and hence a focus of research. Our study performed characteristic analysis, source analysis, and ecological and health risk assessment for three kinds of Persistent Organic Pollutants (POPs) − polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in the Taihu Lake basin. Using measured data from the centralized source of drinking water in the basin as well as historical data, we analyzed the characteristics and sources of the three POPs. Then the ecological risks of PAHs, OCPs, and PCBs were assessed according to the environmental quality standards in sediment of USEPA, and the health risks were assessed with the exposure assessment method. The results show that for centralized drinking water source of Taihu Lake basin: the sampled products were detected in 11 kinds of PAHs, which ranged from nd to 280ng/g and are at low ecological and health risks level. OCPs in surface sediments are mainly from soil and may have new benzex sources and have low ecological and health risks. PCBs are mainly from pollution from factories and are at low ecological and health risks level. Results of this study can provide a reference for drinking water management of the lake.

Distribution and enantiomeric profiles of organochlorine pesticides in surface sediments from the Bering Sea, Chukchi Sea and adjacent Arctic areas

The spatial distribution, compositional profiles, and enantiomer fractions (EFs) of organochlorine pesticides (OCPs), including hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), and chlordanes (CHLs), in the surface sediments in the Bering Sea, Chukchi Sea and adjacent areas were investigated. The total concentrations of DDTs, HCHs and CHLs varied from 0.64 to 3.17 ng/g dw, 0.19–0.65 ng/g dw, and 0.03–0.16 ng/g dw, respectively. No significant difference was observed between the Bering Sea and Chukchi Sea for most pollutants except for trans-CHL, ΣCHLs (sum of trans- and cis-chlordane) and p,p'-DDD. Concentration ratios (e.g., α-HCH/γ-HCH, o,p'-DDT/p,p'-DDT) indicated that the contamination in the studied areas may result from inputs from multiple sources (e.g., historical usage of technical HCHs as well as new input of dicofol). Chiral analysis showed great variation in the enantioselective degradation of OCPs, resulting in excess of (+)-enantiomer for α-HCH in thirty of the 32 detectable samples, preferential depletion of (−)-enantiomer for o,p'-DDT in nineteen of the 35 detectable samples, and nonracemic in most samples for trans- and cis-chlordane. The ecological risks of the individual OCPs as well as the mixture were assessed based on the calculation of toxic units (TUs), and the results showed the predominance of DDT and γ-HCH in the mixture toxicity of the sediment. Overall, the TUs of OCPs in sediments from both the Bering and Chukchi Seas are less than one, indicating low ecological risk potential.

Occurrence, sources, and risk assessment of OCPs in surface sediments from urban, rural, and reclamation-affected rivers of the Pearl River Delta, China.

Sediments were collected to a depth of 20cm from urban, rural, and reclamation-affected rivers in the Pearl River Delta of China. In total, 16 organochlorine pesticides (OCPs) were analyzed in all sediment samples, and the occurrence, possible sources, toxicity, and health risks of OCPs were evaluated to compare the contamination characteristics of OCPs in sediments among the three types of rivers. The results showed that concentrations of Σ16OCPs in sediments from the three rivers followed the order urban river > reclamation-affected river > rural river, with a mean value of 247.21, 232.91, and 114.92μg/kg, respectively, and the predominant OCPs were hexachlorobenzene (HCB), dieldrin, aldrin, endrin, and hexachlorocyclohexanes (HCHs). Source diagnostics illustrated that there might be recent input of HCHs, dichlorodiphenyltrichloroethanes (DDTs), and endosulfan in some sampling sites. Based on the soil quality thresholds of China, both HCHs and DDTs fell within the range of class II criteria except for some sediment samples in urban rivers with lower levels (below class I criteria). According to sediment quality guidelines, 92.86% of samples were predicted to be toxic. The health risk assessment showed that OCPs would not pose a threat to people via dermal contact, ingestion, and inhalation, and the followed order of incremental lifetime cancer risks for OCPs in sediment samples was reclamation-affected river > urban river > rural river.

Polychlorinated biphenyls and organochlorine pesticides in surface sediments from Shantou Bay, China: Sources, seasonal variations and inventories

Sediments from Shantou Bay, China, were analyzed for polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) for the first time. The concentrations of PCBs and OCPs were 0.54–55.5ngg−1 and 2.19–16.9ngg−1 (dry weight), respectively. Source identification showed that tri-CBs and penta-CBs were manufactured and used in the last century, while usage of antifouling paint might still serve as a significant source of sediment DDT. Concentrations of PCBs and HCHs significantly (p<0.05) increased after wet season, suggesting that atmospheric deposition and surface runoff played an important role in distribution of historical pollutants. Additionally, the adverse biological effects could occasionally occur for DDT in sediments. The mass inventories were preliminarily calculated for PCBs (90.1ngcm−2 and 0.09tons) and OCPs (61.8ngcm−2 and 0.062tons) in Shantou Bay, while as part of the “reservoir” of organochlorine compounds to the global ocean, its role cannot be neglected.

Distribution Characteristics and Ecological Risk Assessment of Organochlorine Pesticides in Surface Sediments of Zhelin Bay in Guangdong Province, China

The distribution characteristics and pollution degrees of 20 organochlorine pesticides (OCPs) were investigated in surface sediments from Zhelin Bay south of China and the ecological risk of OCPs and integrated ecological risk at the samples stations in sediments were evaluated by risk quotient (RQ) and sediment quality guideline of NOAA. The possible sources of HCHs and DDTs in sediments were preliminarily studied, and the correlation between OCPs and sediment characteristic parameters was discussed. The concentrations of DDTs in surface sediments were found to be higher than those of other OCPs, especially p,p'-DDD, and the concentrations of DDTs were higher than the limited values of Chinese Marine sediment quality criteria. The total concentration of 20 OCPs in surface sediments ranged from 14.14 to 306.88 ng·g-1, with a mean concentration of 78.37 ng·g-1, and the highest total concentration was at site 8(S8). There were inevitable adverse biological effects and high ecological risk of p,p'-DDD and p,p'-DDT, high integrated ecological risk at S8 and S10. The possible sources of HCHs in surface sediments of Zhelin Bay were mainly from the application of Lindane pesticides. At S1,S2,S10,S11 there was input of DDT into mariculture area of Zhelin Bay, and at the other sites the sources of DDT were from the early residue in sediments or the long-term weathering sediments of using pesticides. There was a very significant positive correlation between HCHs, endosulfan, chlordane and dieldrin in sediments, while there was a negative relation between the above OCPs and TOC, which indicated that the presence of TOC could promote their biodegradation. There was a significant positive correlation between p, p'-DDD and Ca, which revealed that DDT used in the early period was deposited with biological carbonate. Increasing size of sediment particles discouraged the accumulation and enrichment of OCPs in sediments.

Polychlorinated biphenyls and organochlorine pesticides in surface sediments from the sand flats of Shuangtaizi Estuary, China: levels, distribution, and possible sources.

Levels of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in sediments from the sandy flat system of Shuangtaizi Estuary, the highest-latitude estuary in China, were investigated to identify their possible sources and potential ecological risk. The concentrations of 28 PCBs and 18 OCPs ranged from 1.83 to 36.68ngg(-1) dw (mean 10.53ngg(-1) dw) and from 0.02 to 14.57ngg(-1) dw (mean 5.65ngg(-1) dw), respectively. Generally, these organic pollutants showed an obvious spatial distribution, and relatively high levels were found at the high-tidal zone near river mouths. Compositional analyses indicated that tetra-PCBs were dominant for PCBs, whereas heptachlor was identified to be prevalent for OCPs in surficial sediment in the sand flats of Shuangtaizi Estuary. Overall, Shuangtaizi Estuary had moderate PCB and OCP levels in the sand flat sediments and posed a low ecological hazard to aquatic biota. Our results indicated that the sediment PCBs came from nonpoint deposition, such as atmospheric contribution and river input, for light chlorinated congeners and point source deposition, such as the industrial sources along river flow, for highly chlorinated congeners, whereas OCPs originate mainly from old residuals and new usage of pesticides in agriculture and aquaculture.

Residues, Sources and Potential Biological Risk of Organochlorine Pesticides in Surface Sediments of Qiandao Lake, China.

Sediment samples were analyzed to comprehensively characterize the concentrations, distribution, possible sources and potential biological risk of organochlorine pesticides in Qiandao Lake, China. Concentrations of sumHCH and sumDDT in sediments ranged from 0.03 to 5.75ng/g dry weight and not detected to 14.39ng/g dry weight. The predominant β-HCH and the α-HCH/γ-HCH ratios indicated that the residues of HCHs were derived not only from historical technical HCH use but also from additional usage of lindane. Ratios of o,p'-DDT/p,p'-DDT and DDD/DDE suggested that both dicofol-type DDT and technical DDT applications may be present in most study areas. Additionally, based on two sediment quality guidelines, γ-HCH, o,p'-DDT and p,p'-DDT could be the main organochlorine pesticides species of ecotoxicological concern in Qiandao Lake.

Distribution and ecological risk assessment of organochlorine pesticides in surface sediments from the East Lake, China.

Organochlorine pesticides (OCPs) are ubiquitous pollutants, and their presence in urban lakes is a concern for human and ecological health. Surface sediments in the East Lake, China, were collected in winter 2012 and summer 2013 to investigate concentrations, distribution patterns, possible sources, and potential ecological risks of OCPs in this area. The total concentrations of 14 OCPs ranged from 6.3 to 400 ng g(-1) dry weight (dw) with an average concentration of 79 ng g(-1) dw. The mean values of hexachlorocyclohexanes (HCHs) (α-, β-, γ-, and δ-HCH) and dichlorodiphenyltrichloroethanes (DDTs) (p,p'-DDE, p,p'-DDD, and p,p'-DDT) were 36 and 7.6 ng g(-1) dw, accounting for 45 and 10 % of the total OCPs, respectively. The concentrations of OCPs in sediment samples collected in winter were significantly higher than those in summer, especially the HCHs, of which in winter were two times greater than summer. Composition analyses indicated that DDTs and endosulfan were mainly from historical contribution. Historical use of technical HCH and new input of lindane were probably the source of HCHs in the East Lake. Most sampling sites of HCHs and DDTs were found to have the potential ecological risk based on levels specified in the sediment quality standards.

Distribution, sources, and ecological risks of organochlorine pesticides in surface sediments from the Yellow River Estuary, China

Thirty-four surface sediment samples were analyzed for organochlorine pesticides (OCPs), in order to provide information on levels, distribution and sources of these compounds in the Yellow River Estuary, China. The levels of the organochlorine pesticides in samples were detected by the technique of soxhlet extraction followed by analysis by gas chromatography (GC) coupled with a mass selective detector. Total concentrations of OCPs ranged widely from 0.06 to 53.4 ng g(-1), with a mean value of 44.84 ng g(-1), at the mid level of pesticide concentrations compared to those reported in other regions worldwide. HCHs were the predominant species in the study area. The ratios of α-HCH/γ-HCH indicated that the technical HCH contamination was mainly due to a recent input of lindane in upper reach of Yellow River Estuary. The ratios of (DDD + DDE)/DDTs and DDD/DDE suggested that DDTs in sediments came mainly from the degradation of historical DDT in the environment, and DDT could be much easier to degrade into DDD under anaerobic conditions. Principal component analysis (PCA) could conclude that most of the OCPs came from early input and historical degradation products in the study area. Based on the sediment quality guidelines, γ-HCH and p'p-DDE would be of more concern for the ecotoxicological risk in this study area.

Distribution and bioaccumulation of organochlorine pesticides in surface sediments and benthic organisms from Taihu Lake, China

The spatial distribution and bioaccumulation of organochlorine pesticides (OCPs) in surface sediments and benthic organisms from Taihu Lake were studied. OCPs were detected in all sediment samples with total concentrations ranging from 4.22 to 461 ng g −1 dry weight (dw). The ratios of certain metabolites to their parent compounds indicated there are still new inputs of parent DDT (dichlorodiphenyltrichloroethane) to Taihu Lake, while the highest residues of HCHs (hexachlorocyclohexanes) mainly came from earlier usage and fresh γ-HCH (lindane). No positive correlation was found between the distribution of OCPs and organic matter contents in sediments. Concentrations of OCPs and lipids in typical large benthic organisms, Bellamya aeruginosa ( B. aeruginosa) and Corbicula fluminea ( C. fluminea) , increased with body weight. HCHs, DDTs, chlordanes and heptachlors were the dominant compounds detected in organisms and C. fluminea accumulated much more OCP than B. aeruginosa. Higher values of biota-sediment accumulation factor (BSAF) were detected in C. fluminea, which was both affected by biological characteristics of the organisms and physicochemical properties of the compounds.

Organochlorine pesticides in surface sediments and suspended particulate matters from the Yangtze estuary, China

Total HCHs' and total DDTs' levels in surface sediments (SS) ranged from 0.5 to 17.5 ng g(-1) and from 0.9 to 33.1 ng g(-1), averaged 6.0 and 8.2 ng g(-1), respectively. Total HCHs' and total DDTs' levels in suspended particulate matters (SPM) varied from 6.2 to 14.8 ng g(-1) with a mean value of 12.3 ng g(-1) and were from 3.4 to 25.7 ng g(-1) with an average of 16.4 ng g(-1), respectively. Lindane is the main HCHs' source and continuing use in the Yangtze Delta areas of 'pure' gamma-HCH (lindane) rather than technical HCH (a mix of largely alpha- and some gamma-HCH). DDTs in SS are mainly accumulated in history. However, high DDT fractions in SPM are indicators of new input of typical dicofol type DDT from 2002 to 2004. It can be seen that most samples from the Yangtze estuary were in ranges where adverse biological effects are expected, either occasionally or frequently.

Historical contamination and sources of organochlorine pesticides in sediment cores from Quanzhou Bay, Southeast China

Three sediment cores were collected from the top to the mouth of Quanzhou Bay, Southeast China, in order to establish sources and historical trends of organochlorine pesticides (OCPs) in the region. The spatial distribution of OCPs in surface sediments implies that Quanzhou Bay received the contamination inputs not only from rivers near the shore, but also from outside the bay. The variation profiles of concentrations clearly showed that OCPs were widely used between 1960s and 1980s in China. A recent increasing trend was found in all cores despite their ban in China in 1983. Different ratios of (DDD + DDE)/DDTs indicated that DDTs at the top of the bay were mainly derived from long-term weather soils, while DDTs near the mouth of the bay were mainly derived from fresh inputs from outside the bay. Higher percentage of γ-HCH in HCHs deposited after 1990 implies that lindane may have been used recently around Quanzhou Bay.