Assessing Sustainable Management of a Plateau Lake: Adsorption and Integrated Risk of Sediment Pollutants

As one of the nine largest plateau lakes in Yunnan Province, China, Qilu Lake is considered significantly affected by extensive anthropogenic pollution. However, the pollution status and integrated risks posed by organochlorine pesticides and heavy metals in the lake’s sediments remain poorly understood. This study analyzed the concentrations of organochlorine pesticides and heavy metals in 22 surface sediment samples from the Qilu Lake, and assessed their combined ecological and health risks. Results showed that the mean concentrations of five target organochlorine pesticides (α-hexachlorocyclohexane, β-hexachlorocyclohexane, γ-hexachlorocyclohexane, p,p′-dichlorodiphenyltrichloroethane, and o,p′-dichlorodiphenyltrichloroethane) were consistently low, whereas most heavy metals, except for arsenic, significantly exceeded Yunnan Province background values, with mercury and cadmium exhibiting the most pronounced enrichment. Source analysis indicated that the heavy metals mainly derived from a mixed agricultural-industrial-traffic source, a natural geogenic source, and industrial-traffic emissions, while the organochlorine pesticides originated from both historical residues and ongoing agricultural applications. A linear model was identified as optimal function for characterizing the adsorption-accumulation relationship between organochlorine pesticides and heavy metals. Ecological risks were dominated by heavy metals, especially cadmium, and the evaluated results showed that the health risks were higher for children than adults. Although non-carcinogenic risks were negligible, carcinogenic risks, particularly from chromium, warrant special attention, especially for children. This study enhances the understanding of combined pollution in rural plateau lakes and provides a scientific basis for achieving sustainable water environment management by (1) establishing an integrated risk assessment framework for pollutants, (2) identifying a priority control pollutant list, and (3) laying a theoretical foundation for targeted ecological restoration strategies, directly supporting the implementation of Sustainable Development Goal (SDG) 6 (clean water and sanitation).