Distribution of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in surface water and sediments from Baiyangdian Lake in North China

Persistent organochlorine compounds, including hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs) and polychlorinated biphenyls (PCBs) were analyzed in surface water and sediments from Baiyangdian Lake, North China. Total concentrations of HCHs, DDTs and PCBs in surface water were in the range of 3.13-10.60, 4.05-20.59 and 19.46-131.62 ng/L, respectively, and total concentrations of HCHs, DDTs and PCBs in sediments were 1.75-5.70, 0.91-6.48 and 5.96-29.61 ng/g dry weight, respectively. Among the groups of HCHs (sum of alpha-HCH, beta-HCH, gamma-HCH and delta-HCH) and DDTs (sum of DDT, DDD and DDE), the predominance of beta-HCH, DDE and DDD in water and sediment samples was clearly observed. This observation suggested that beta-HCH was resistant to biodegradation and the DDTs had been transformed to its metabolites, DDE and DDD. For PCBs, penta-, hexa- and hepta-chlorinated congeners were the most abundant compounds in the both phases. Furthermore, the partitioning of chlorinated compounds between sediment and water was investigated to understand their transport and fates in aquatic ecosystems. The results indicated that average logs of organic carbon-normalized sediment-water partition coefficients (logK'(oc)) for OCPs varied between 3.20 and 5.53, and for PCBs, logK'(oc) values ranged from 3.19 to 5.57. The observed logK'(oc) was lower than their equilibrium logK(oc) predicted from linear model, which may be attributed to the solubility enhancement effect of colloidal matter in water phase and the disequilibrium between sediment and water.