Persistent Toxic Pollutants in Surface Sediments of the River Soan, Pakistan: Trends, Profile, Sources and Risk Assessment

Abstract

Concentration, distributional pattern, compositional profile and risk assessment of Organochlorine Pesticides (OCPs) were investigated in surface sediment of the Soan River and its feeding tributaries, Pakistan. OCPs included 41 congeners of Polychlorinated biphenyls (PCBs), 28 congeners of Polybrominated diphenyl ethers (PBDEs), 6 isomers and metabolites of Dicholoro Dibenzo Trichloroethane (DDTs), 4 isomers of Hexa ChI oro Hexane (HCH), a - and y- Chlordanes and Hexa Chloro Benzene (HCB). The concentration for PCBs, DDTs, PBDEs, HCH, Chlordanes and HCB ranged from 37.38-186.92, 5.19-30.05,0.011-20.6, 6.9-17.16, 0.62-1.85 and nd-0.09ng/g. OCPs in sediments followed the order: PCBs >DDTs >PBDEs >HCH >Chlordane > HCB. The highest concentrations of OCs were found in Soan River as compared to its feeding tributaries. The observed congener pattern for PBDEs were -47>-99>- 100>- 153>-154 and for PCBs were -149> -153> -18> -138> -44. The isomers and metabolites pattern for DDTs were p,p'- DDT >p, p'-DDD> p,p'- DDE >0, p'-DDT> 0, p'-DDD> 0, p'-DDE and for HCHs were ~-HCH> a-HCH> y-HCH> 8-HCH. Ratios of (DDE+DDD)I I DDTs and p,p'-DDTI p,p'-DDE suggested the recent input of DDTs in sediments. a/y HCH ratio indicated its past usage of lindane and technical mixtures. PCBs concentrations suggested commercial PCBs products Arochlor 1254 and Arochlor 1260 as main source of contamination. The Total Organic Carbon in sediments ranged from 0.10% to 5.37%. Correlation analysis suggested that the Total Organic Carbon (TOC) was influencing factor in controlling the distribution of PBDEs.