Organochlorine pesticide (OCP) residues in mountain soils from Tajikistan†
The concentrations and spatial distribution of organochlorine pesticides (OCPs) in surface soils of different altitudes (570–4656 m) from Tajikistan were determined. OCPs were detected in all samples with concentrations in the range 52.83–247.98 ng g−1 dry weight (ng g−1 dw). Aldrins were the most predominant compounds followed by chlordanes, hexachlorocyclohexanes (HCHs) and endosulfans, while dichlorodiphenyltrichloroethanes (DDTs) and methoxychlor were detected at much lower concentrations. Composition analysis indicated that OCPs mainly came from the atmospheric transport of historically used pesticides. OCP residues in the west and northwest parts of Tajikistan were higher than the east and the southeast due to the proximity to the potential sources and anthropogenic activity intensities around. Additionally, correlation analysis between OCPs and altitudes indicated that the more volatile pollutants, such as HCH isomers, seemed to become enriched more easily in regions with higher altitudes relative to the less volatile ones, such as DDTs.