Organochlorine pesticides (OCPs) in soils near and around Lake Son-Kul in the western Tian Shan Mountains, Central Asia

Abstract

Summer pasture development and tourism near and around Lake Son-Kul in the western Tian Shan Mountains has resulted in a local source of organochlorine pesticides (OCPs) that lack monitoring and evaluation. Twenty-eight soil samples were collected from the Lake Son-Kul Basin (SKB) and Naryn River Valley (NRV) to measure OCP concentrations and evaluate their composition, transport processes, and ecological risks. Except for the high OCP concentration measured at one location, site 7 (145.32 ng/g dw), total OCP concentrations in the SKB ranged from 2.36 to 24.13 ng/g dw, slightly higher than concentrations in the NRV (1.69–7.45 ng/g dw) and similar to values in polar regions. Among the OCPs, HCHs and methoxychlor were the predominant compounds that accumulated in soils, followed by DDTs and Aldrins, whereas Chlors and Endos displayed lowest concentrations, indicating that animal husbandry is the main agricultural activity in the study area. Most of the less volatile pesticides, including β-HCH, p,p-DDT, and Chlors, represent past use from local sources, for instance the pesticides warehouse at site 7. More volatile compounds such as α-HCH, γ-HCH, and p’p-DDE represent exogenous atmospheric transport to the study area, as demonstrated by their isomeric ratios. Ecological risk assessment showed that the surface environment of the study area remains in good condition. Findings from this study provided a snapshot of the current status of OCP contamination in soils of the Lake Son-Kul region. Although historical OCP contamination has impacted the lake’s ecology, catchment soils display low levels of OCP contamination.