Spatiotemporal Distribution and Ecological Risks of Psychoactive Substances in Wastewater Treatment Plants in Haikou City, China

This study investigated the occurrence, pollution characteristics, and ecological risks of psychoactive substances (PSs) in wastewater treatment plants (WWTPs) in Haikou City. Solid phase extraction (SPE) and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) were used to analyze the pollution levels and spatiotemporal changes of 14 types of PS. The removal rates of PSs in different WWTPs were investigated, and the ecological risks were evaluated using the risk quotient (RQ) method. The results showed that: (1) 14 psychoactive substances were detected in the influent and effluent of the WWTPs, with concentration ranges of 0.04-848.49 and 0.07-752.99 ng/L in spring and summer, respectively. The highest concentrations of PSs were ephedrine (EPH) and arecoline (ARE). The spatial and temporal distribution characteristics were significantly influenced by factors such as surrounding population mobility, dietary habits, and industrial development. (2) The removal rates of EPH and ARE could reach up 94% and 90%, respectively, while the removal rates of 3,4-methylenedioxy amphetamine (MDA), NK (Norketamine), KET (Ketamine) and MTD (Methadone) were all negative. (3) The ecological risk of PSs in the effluent of WWTPs is low, and the risks of EPH and MTD are low (0.01≤RQ<0.1). There is no ecological risk for other psychoactive substance (RQ<0.01). The research has shown that psychoactive substances are widely present in wastewater and cannot be completely removed through wastewater treatment processes. Therefore, their potential long-term ecological risks to the water environment should not be ignored.