Distribution Of HCHs Research Articles

Integrating compound-specific stable isotope and enantiomer-specific analysis to characterize the isomeric and enantiomeric signatures of hexachlorocyclohexanes (HCHs) in paddy soils

Organic pollutants in paddy fields may undergo different processes from those in dryland due to the anaerobic environment. The integrated use of compound-specific stable isotope analysis (CSIA) and enantiomer-specific analysis is a promising technique for understanding the behavior and fate of organic pollutants in soils. In this study, soil samples were collected from paddy fields in three major rice cultivation regions of China, spanning a transect of 4000 km. The mean concentrations of ƩHCHs in paddy soils from the Taihu Plain were the highest (1.44 ng/g). The ratios of α-HCH/β-HCH (all below 11.8) and α-HCH/γ-HCH (92% below 4.64), as well as the enantiomeric fractions (EFs) of chiral α-HCH (mean of 0.81), reflected that the distribution of HCHs was affected by the use of both technical HCHs and lindane. The preferential depletion of (-)-α-HCH and pronounced carbon isotope fractionation of α-HCH (δ13C of −28.22 ± 0.92‰ −23.63 ± 1.89‰) demonstrated its effective transformation. Factors such as altitude, soil temperature, soil pH, soil conductivity and soil organic matter significantly influenced the fate and transformation of HCHs. The current study highlights the integrated application of CSIA and enantiomer-specific analysis to provide multiple lines of evidence for the transformation of HCHs in soils.

Effects of benthic organism Tubifex tubifex on hexachlorocyclohexane isomers transfer and distribution into freshwater sediment

In this study, bioaccumulation and elimination of HCHs in tubifex, and the distribution of HCHs in overlying water and sediment, were studied during a 10-d experiment. A sensitive method was developed for the determination of HCHs in samples based on gas chromatograph (GC) equipped with a nickel-63 electron capture detector (μECD). The limit of detection (LOD) was 0.35µg/kg for α-HCH and 0.82µg/kg for β-HCH. Tubifex accumulated HCHs rapidly, and the curves were approximately M-type. The highest level was reached on the 7th day, with 0.34mg/kgwwt for α-HCH and 0.87mg/kgwwt for β-HCH in worms. The AFs of β-HCH in tubifex were higher than those of α-HCH. Moreover, the existence of tubifex significantly reduced β-HCH fluxes from the overlying water to sediment by uptake or degradation and decreased the concentrations of β-HCH in the sediment, but it had little influence on α-HCH fluxes. Moreover, enantioselectivity of α-HCH enantiomers was not observed in tubifex, whether in the bioaccumulation or elimination experiments. At the end of the elimination experiment, approximately 80% and 70% of α-HCH and β-HCH were eliminated, and the depuration half-lives were 4.43 and 5.39 days, respectively.

Distribution and Sources of HCHs in Surface Water from Honghu Lake, China

Surface water samples of two sections were respectively collected from one side to the other side of Honghu Lake, China, in order to detect the concentrations and distribution of HCHs in the region. The concentrations of total HCHs (the sum of α-HCH, β-HCH,γ-HCH and δ-HCH) in surface water of Honghu Lake ranged from 0.94 to 7.04 ng/L. The highest concentration of HCHs in water was near a shipping traffic path. HCHs were derived mainly from agricultural runoff around Honghu Lake and release of the sediments. Among four component compounds of HCHs, γ-HCH was major contributor in the water, which suggested that lindane may have been used recently around Honghu Lake.

Distribution of HCHs and DDTs in the soil–plant system in tea gardens in Fujian, a major tea-producing province in China

The distribution of HCHs and DDTs were investigated in tea gardens in Fujian, a major tea-producing province in China. ∑HCHs ranged from 0.56±0.32ngg−1 in soils to 4.1±2.6ngg−1 in old leaves, and ∑DDTs ranged from 1.0±0.73ngg−1 in soils to 4.1±4.3ngg−1 in old branches. γ-HCH was the major HCH isomers, with the percentages of 36–83%, and p,p′-DDT and o,p′-DDT accounted for 40–49% and 17–36% in total DDTs in plant tissues. Tea plants could accumulate HCHs and DDTs, with the highest γ-HCH bioconcentration factor in old leaves and p,p′-DDT in old branches. HCHs and DDTs concentrations between soil and plant suggested that HCHs tended to accumulate in most of the plant tissues, while DDTs mainly accumulate in the roots. Low ratios of α-/γ-HCH and β-/(α+γ)-HCH indicated new input of lindane in tea gardens. High ratios of DDT/(DDD+DDE) indicated fresh introduction of DDT, and high ratios of o,p′-DDT/p,p′-DDT suggested the input of dicofol in these gardens.

Distribution of HCHs and DDTs in Agricultural Soil of Pudong New Area, Shanghai

To study HCHs and DDTs contents and their spatial distribution in the agricultural soil of Pudong, Shanghai, the residue amounts of HCHs and DDTs in 238 surface soil samples were determined. The results showed that concentrations of HCHs ranged from 0.001 to 0.050 mg/kg and DDTs ranged from 0.001 to 0.067 mg/kg, with both occurrences of 100%. The spatial analysis indicated that there was the obvious regional differentiation in soil pollution. Compared with HCHs, soil quality was contaminated more seriously by DDTs in the study area. In addition, areas with high contents of HCHs were mainly located in Jichang, Chuansha and Sanlin, whereas areas with high concentrations of DDTs mainly lied in Sanlin, Jichang, Tang, Chuansha and Caolu.

Distribution and sources of organochlorine pesticides in water and sediments from Daliao River estuary of Liaodong Bay, Bohai Sea (China)

The levels of 19 kinds of organochlorine pesticides (OCPs) in the aqueous phase, suspended particulate matter (SPM), pore water and sediments from Daliao River estuary of Liaodong Bay (Bohai Sea) in northeast China were investigated to evaluate their potential pollution risks. The total OCPs concentrations in the aqueous phase, SPM, pore water and sediments were 3.7–30.1 ng l −1, 4.6–52.6 ng l −1, 157–830 ng l −1 and 2.1–21.3 ng g −1 dry weight, respectively. The concentrations of OCPs, in the Daliao River estuary, are in the mid-range, as compared to those reported in other estuaries worldwide. The distribution of HCHs and DDTs were different indicating different contamination sources. Lindane is the main type of HCH and continuing use in northeast China of ‘pure’ HCH (lindane) rather than technical HCH accounts for the source. The ratios of (DDE + DDD)/DDT in the samples indicate no recent inputs of these chemicals to the estuary.

Persistent organochlorine residues in estuarine and marine sediments from Ha Long Bay, Hai Phong Bay, and Ba Lat Estuary, Vietnam

To assess the organochlorine contamination in the northeast coastal environment of Vietnam, a total of 41 surface sediments were collected from Ha Long Bay, Hai Phong Bay, and Ba Lat estuary, and analyzed for their organochlorine content. Organochlorine compounds (OCs) were widely distributed in the Vietnamese coastal environment. Among the OCs measured, DDT compounds predominated with concentrations ranging from 0.31 to 274 ng g −1. The overall contamination level of DDTs in coastal sediments from northern Vietnam is comparable with those from other Asian countries. However, concentrations exceeding 100 ng g −1 are comparable with high concentrations reported from India and China, the largest DDT consumers in the world. The overall concentrations of PCBs, HCHs, and chlordanes in surface sediments were in the ranges of 0.04–18.71 ng g −1, not detected (n.d.) – 1.00 ng g −1, and n.d. – 0.75 ng g −1, respectively. Ha Long Bay and Hai Phong Bay were relatively more contaminated with DDTs and PCBs than other regions, respectively. In contrast, the distribution of HCHs was relatively homogeneous. OCs contamination in the coastal environment of Vietnam is closely related to shipping and industrial activities. The levels of DDT compounds in harbors and industrial areas exceeded their sediment quality guideline values suggested by Environment Canada [CCME (Canadian Council of Ministers of the Environment), 2002. Canadian sediment quality guidelines for the protection of aquatic life. In: Canadian Environmental Quality Guidelines. Canadian Council of Ministers of the Environment, Winnipeg, MB] and Australian and New Zealand [ANZECC and ARMCANZ, 2000. National water quality management strategy. Paper No. 4, Australian and New Zealand Guidelines for Fresh and Marine Water Quality, vol. 1, The Guidelines. Australia. Document: http://www.deh.gov.au/water/quality/nwqms/volume1.html], indicating that adverse effects may occur to marine species in that areas.

Distribution of organochlorine pesticides in surface water and sediments from Qiantang River, East China

The levels of 13 organochlorine pesticides (OCPs) in surface water and sediments from Qiantang River in East China were investigated to evaluate their potential pollution and risks. A total of 180 surface water samples at 45 sampling sites and 48 sediment samples at 19 sampling stations were collected along the river in four seasons of 2005. Soil samples and wet deposition samples were also collected to provide evidence on the source of OCPs pollution. The total OCPs concentrations in surface water and sediments were 7.68–269.4ng/L and 23.11–316.5ng/g-dry weight (dw), respectively. The concentrations of OCPs in sediments were in the range of 8.22–152.1ng/g-dw for HCHs (α-, β-, γ-, δ-HCH), 1.14–100.2ng/g-dw for DDTs (p,p′-DDD, p,p′-DDE, p,p′-DDT o,p′-DDD), 9.41–69.66ng/g-dw for other OCPs (aldrin, diedrin, endrin, heptachlor, heptachlor epoxide). The total OCPs concentrations in soils and wet deposition were 5.04–214.9ng/g-dw and 16.18–242.4ng/L, respectively. Among the OCPs, HCHs, DDTs and heptachlor were the most dominant compounds in the sediments. The dominant OCPs in water were γ-HCH among HCHs, heptachlor among other OCPs and p,p′-DDE among DDTs. Also, different contamination patterns among sampling seasons were found. The concentrations of OCPs in sediment collected in spring were higher than those in summer and autumn. In contrast, the concentrations of OCPs in surface water in summer and autumn were higher among four sampling seasons. Distribution of HCHs, DDTs and other OCPs were different indicating their different contamination sources. The notable contamination was found in Fuchun reservoir. Composition analyses in sediments indicated a recent usage or discharge of lindane into the river.