Environmental monitoring of organo-halogenated contaminants (OHCs) in surface soils from Pakistan.

Extensive monitoring of organo-halogenated contaminants (OHCs) from surface soils of different land-use types from Pakistan was carried out during 2010. The concentrations (ng g(-1); dry weight) and profiles clearly indicated the dominance of ∑DDT contaminants followed by the ∑HCHs, ∑30PCBs, chlordanes, and ∑10PBDEs in descending order. Concerning the spatial patterns of occurrence, industrial soils exhibited relatively higher concentration of DDTs, heavy PCBs, and PBDEs (noticeably BDE-47 and -99 congeners), while the urban soils were characterized by high total PCBs (with relatively higher levels of light PCBs), following the agricultural soils. Compared to available criterion guidelines, the current results suggested that 10% of soil samples from industrial sites exhibited slightly higher levels (>50 ng g(-1)) of DDTs. The ∑TEQ levels for mono-ortho DL-PCBs ranged from 0.7 to 5.65 (1.9) pgTEQg(-1) dw in all the studied samples and PCB-118 contributed significantly towards the total calculated TEQs. The results of this study will contribute to the environmental management of OHCs contaminated areas of Pakistan.