Organo-halogenated contaminants (OHCs) in the sediments from the Soan River, Pakistan: OHCs(adsorbed TOC) burial flux, status and risk assessment

Abstract

In this study, regression analysis revealed that TOC is the principal factor in controlling the fate of organo-halogenated contaminants (OHCs: PCBs, PBDEs, OCPs) in Soan River, Pakistan. The OHCs(adsorbed TOC) burial flux (OHCs(adsorbed TOC)Bf; mg/cm2·yr) was calculated in the following ranges: ∑PCBs (0.07–0.31), ∑PBDEs (0.005–0.029), ∑HCHs (0.015–0.046) and ∑DDTs (0.007–0.039). Apart from OHCs(adsorbed TOC)Bf, the levels of OHCs were in the following order: PCBs>DDTs>PBDEs>HCH>Chlordane>HCB. PBDEs and PCB congener patterns showed following order respectively: BDE-149>-153>-18>-138>-44 and PCB-149>-153>-18>-138>-44. DDT isomers and metabolites' pattern were p,p′-DDT>p,p′-DDD>p,p′-DDE>o,p′-DDT>o,p′-DDD>o,p′-DDE and HCHs were β-HCH>α-HCH>γ-HCH>δ-HCH. PBDE composition had similarities to penta-BDE and DE-71 mixtures and PCBs with commercial products Aroclor-1254 and -1260. (DDE+DDD)/∑DDTs and p,p′-DDT/p,p′-DDE suggested the recent input of DDTs in sediments while α/γ-HCH indicated past usage of lindane and technical mixtures. Risk assessment suggested that Soan River and its tributaries are potentially at risk against most of the OHCs.