Residues of organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) in waters of the Ili-Balkhash Basin, arid Central Asia: Concentrations and risk assessment.

Release and transport of contaminants in watersheds can have adverse effects on aquatic organisms and human health. Little attention, however, has been paid to chemical contamination of aquatic environments in arid regions by persistent organic pollutants. We analyzed the concentrations and distributions of organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) in waters of the Ili-Balkhash Basin, in arid central Asia. ΣOCP concentrations ranged from 4.02 to 122.80 ng L and ΣPAH concentrations were between 7.58 and 70.98 ng L. On a global scale, OCP and PAH concentrations in waters of the Ili-Balkhash system were relatively low, with only a few exceptions, i.e., highest concentrations near cities and relatively high values in some headwater areas. Source identification revealed that the dichlorodiphenyltrichloroethanes (DDTs) may come from recent use, whereas endosulfans stem from historic applications. Lindane, a common insecticide, may be responsible for hexachlorocyclohexanes (HCHs). Low-molecular-weight PAHs, primarily originating from wood and coal combustion and petroleum-derived sources, were the primary components of PAHs in waters. Furthermore, the primary sources of PAHs at different sites were identified using a Positive Matrix Factorization model: 1) oil leakage (33.9%), 2) biomass burning (29.5%), 3) coal combustion (22.6%), and 4) petroleum-powered vehicles (14.1%). Agricultural, industrial and domestic activities are all potential pollution sources. Besides, contaminated headwater areas indicate that long-range transport has probably become a non-negligible mechanism for pollutant distribution. Risk assessment showed low to moderate toxicity for aquatic organisms, but no marked carcinogenic or non-carcinogenic risks for human health.