title: Occurrence, enantiomeric signature and ecotoxicological risk assessment of HCH isomers and DDT metabolites in the sediments of Kabul River, Pakistan.
abstract: Hexachlorocyclohexane (HCH) isomers and dichlorodiphenyltrichloroethane (DDT) metabolites were analyzed in sediments of three different depths (0-10, 10-20 and 20-30 cm) collected from Kabul River, Pakistan, in February 2014. The occurrence levels, enantiomer fractions and potential ecological risk of these organochlorine pesticides (OCPs) were evaluated. The total concentrations of ∑HCHs and ∑DDTs in surface sediments ranged from 4.9-23.9 ng g-1and from 6.4-18.8 ng g-1(dry weight basis), respectively. The vertical contamination profile of DDTs was found in order of 20-30 cm >10-20 cm >0-10 cm, indicated that the residue levels of DDTs gradually decreased after it was banned. The ratios of β-HCH/HCHs ranged from 0.04 to 0.73 (69 % of samples below 0.5) suggesting the fresh input of HCHs, while isomeric ratios of α-HCH/γ-HCH (ranged from 0.02 to 7.94), with 76 % of samples less than 3, indicating the cocktail use of technical grade HCH and lindane in the study area. The ratio of (DDE + DDD)/DDTs (ranged from 0.42 to 0.90) indicated long-term biodegradation of parent DDT. The enantiomer of α-HCH was generally racemic or close to racemic for most of the samples, with enantiomeric fraction (EF) value <0.5 for some of the samples indicated the preferential biodegradation of (+)-α-HCH enantiomer, while for o,p'-DDT the EF values >0.5 indicated the depletion of (-)-o,p'-DDT enantiomer in most of the samples. According to sediment quality guidelines (SQGs), HCH contamination is the main concern for ecotoxicological risk in Kabul River.
authors.affiliation: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China.|Department of Environmental Sciences, University of Peshawar, Peshawar, 25120, Pakistan.|IJRC-PTS, MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Aamir
authors.affiliation: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China. sardar.khan2008@yahoo.com.|Department of Environmental Sciences, University of Peshawar, Peshawar, 25120, Pakistan. sardar.khan2008@yahoo.com.
authors.forename: Sardar
authors.initials: S
authors.lastname: Khan
authors.affiliation: IJRC-PTS, MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China.
authors.forename: Lili
authors.initials: L
authors.lastname: Niu
authors.affiliation: IJRC-PTS, MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China.
authors.forename: Siyu
authors.initials: S
authors.lastname: Zhu
authors.affiliation: Department of Environmental Sciences, University of Peshawar, Peshawar, 25120, Pakistan.
authors.forename: Anwarzeb
authors.initials: A
authors.lastname: Khan
mesh_terms: D003634:DDT / Q000032:analysis* / Q000737:chemistry; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D001556:Hexachlorocyclohexane / Q000032:analysis* / Q000737:chemistry; D007306:Insecticides / Q000032:analysis* / Q000737:chemistry; D007536:Isomerism; D010154:Pakistan; D018570:Risk Assessment; D045483:Rivers / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
chemical_list: D007306:Insecticides; D014874:Water Pollutants, Chemical; D001556:Hexachlorocyclohexane; D003634:DDT
keywords: Ecotoxicological risk; Enantiomer signature; Kabul River; Organochlorine pesticides; Sediments