Investigation of organochlorine pesticides from the Indus Basin, Pakistan: Sources, air-soil exchange fluxes and risk assessment

Present study aimed to evaluate the contamination status of organochlorine pesticides (OCPs) and their associated potential for air-soil exchange and health risks from ecologically important sites of the Indus Basin, Pakistan. Among different OCPs investigated, Sigma DDTs and Sigma HCHs were more prevalent compounds in the agricultural soils and ambient air samples of the study area. The average concentrations for DDTs were found higher at downstream agricultural sites, particularly at Head Panjnad (Soil: 320 ng/g; Air: 743 pg/m(3)) and acting as an ultimate sink of Sigma OCP burden in soils. Spatial distribution patterns inferred ubiquitous distribution of Sigma DDTs in soils and air of the study area. Source diagnostic ratios demonstrated that studied OCPs either are illegally being used in agricultural practices or/and they are residues of past use in the environment. Fugacity fraction model revealed wide variations (ff = 0.12-0.94) with 20% of OCPs above equilibrium range and net volatilization of alpha-endosulfan, beta-HCH and o,p'-DDD. Assessment of cancer risks for OCPs indicated a higher cancer risk (CR > 1 x 10(-6)) for the residents of the Indus Basin. According to the available soil quality guidelines, DDTs and HCHs were above the permissible limits and pose a threat to natural habitat and biodiversity of the Indus Basin. (C) 2014 Elsevier B.V. All rights reserved.