Organochlorine pesticides in water and sediment at a typical karst wetland in Southwest China

The Huixian karst wetland, situated in southwest China, is the largest karst wetland. Historically, organochlorine pesticides (OCPs) have negatively affected the aquatic environment and the health of surrounding residents. In this study, the pollution status and environmental fate of OCPs in multiple environmental media in the Huixian wetland were investigated. The 15 OCPs' total concentration ranges in lake water, ditch water, groundwater, and lake sediment were 46.8–306 ng·L⁻¹, 77.8–251 ng·L⁻¹, 26.0–233 ng·L⁻¹, and 44.8–345 ng·g⁻¹, respectively. The concentrations and proportions of the different OCPs demonstrated significant seasonality. Historical residues are the main source of OCPs in the region, as evidenced by the typical ratios of DDTs and HCHs. Karst regions are extremely vulnerable to environmental changes, as evidenced by the highly dynamic character of the karst wetland system and the rapid migration of multimodal OCPs in different media without considerable damage. According to the risk assessment, both the possible carcinogenic risk to sediments in the Huixian wetland and the ecological risk to water bodies were acceptable. In contrast, the consumption of lake water may put the local population at health risk, which is a cause of concern.