Ecological risk assessment of organochlorine pesticides in coastal sediments: A multi-level approach in the greater bay area

Abstract

The ecological risks posed by persistent organic pollutants are currently a hot research topic in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA). As one of the four largest bay areas globally, and the most economic dynamic region in China, the GBA faces significant environmental challenges, particularly concerning pesticide contamination in coastal sediments. However, studies on the ecological risks of organochlorine pesticides(OCPs) in GBA's coastal sediments remain limited, leading to an insufficient scientific basis for risk management. This study investigate the distribution characteristics of OCPs in coastal sediments in GBA and evaluates their ecological risks employing a multi-level risk assessment approach. The results show that eight OCPs are widely present in GBA's coastal sediments, with concentrations ranging from 0.013 ng/g to 139.56 ng/g. Based on the Risk Quotient (RQ) method, the descending order of ecological risk for these OCPs is as follows: endosulfan, dichlorodiphenyltrichloroethane (DDTs), chlordane, β-hexachlorocyclohexane (HCH), α-HCH, γ-HCH, Hexachlorobenzene (HCB), and mirex. Among them, endosulfan has a high environmental risk, while γ-HCH and DDT present medium environmental risk. Chlordane, β-HCH, and α-HCH exhibit low environmental risk. The semi-probability method evaluation showed that the frequency of endosulfan exceeding predicted no-effect concentration (PNEC) was 91.6 %; while γ-HCH and DDTs had exceedance probability of of 69.4 % and 66.6 %, respectively. The optimized semi-probability method ranked the priority indices of endosulfan, γ-HCH, DDTs, chlordane and β-HCH at 8882.3, 87.2, 77.6, 15.3 and 1.9, respectively. Based on these findings, particular attention should be given to the ecological risks of endosulfan and DDTs in GBA's coastal sediments. This study provides a comprehensive scientific basis for understanding the current status and sources of OCP pollution in the GBA. Moreover, it offers critical insights into the potential ecological risks associated with these contaminants, serving as a scientific foundation for formulating targeted pollution control strategies and environmental management policies.