Accounting for water levels and black carbon-inclusive sediment-water partitioning of organochlorines in Lesser Himalaya, Pakistan using two-carbon model.

This study was designed to monitor organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in riverine water of Lesser Himalaya along the altitude. Further, the sediment-water partitioning employing organic carbon and black carbon models were assessed. Results revealed higher water levels of organochlorine pesticides (0.07-41.4 ng L-1) and polychlorinated biphenyls (0.671-84.5 ng L-1) in Lesser Himalayan Region (LHR) of Pakistan. Spatially, elevated levels were observed in the altitudinal zone (737-975 masl) which is influenced by anthropogenic and industrial activities. Sediment-water partitioning of OCPs and PCBs were deduced using field data by employing one-carbon (fOCKOC) and two-carbon Freundlich models (fOCKOC + fBCKBCCWnF-1). Results suggested improved measured vs predicted model concentrations when black carbon was induced in the model and suggested adsorption to be the dominant mechanism in phase partitioning of organochlorines in LHR.