[Pollution Characteristics and Ecological Risk Assessment of Psychoactive Substances in the Beiyun River Basin]

As a class of emerging contaminants， psychoactive substances have been widely studied regarding their occurrence and removal efficiency in wastewater. However， their pollution characteristics and ecological risks in urban rivers heavily influenced by human activities have attracted increasing attention in recent years. The Beiyun River Basin in the Beijing-Tianjin-Hebei Region was selected as the study area， where 53 surface water samples and 20 sediment samples were collected. A comprehensive analytical approach was employed， combining solid-phase extraction （SPE） and Quick， Easy， Cheap， Effective， Rugged， and Safe （QuEChERS） methods with ultra-performance liquid chromatography-tandem mass spectrometry （UPLC-MS/MS） for the quantification of 12 target psychoactive substances. The spatial distribution patterns and potential pollution sources were analyzed using self-organizing maps （SOM） and k-means clustering algorithms， while the partitioning behavior and ecological risks of the target drugs were assessed based on the partition coefficient and risk quotient （RQ）. The results indicate that all target psychoactive substances were detected in surface water of the Beiyun River Basin， with ephedrine exhibiting the highest concentration （198.36 ng·L^-1） and a detection frequency of 100%. In sediments， nine drugs were detected， with methamphetamine and methadone showing the highest detection frequency （100%）. Spatial clustering analysis revealed that psychoactive substance pollution in the study area primarily originated from wastewater treatment plant effluents， hospital discharges， and agricultural activities. Amphetamine and cocaine exhibited strong adsorption to sediments， whereas ephedrine and codeine demonstrated higher mobility. The distribution of psychoactive substances in the sediment-water system was influenced by multiple interacting factors， with different compounds governed by distinct dominant factors. Ecological risk assessment results showed that the RQ values for all target drugs were below 0.1， suggesting a low risk to aquatic ecosystems at the current contamination levels. However， the present study relied on grab sampling， which only reflected instantaneous concentrations at the time of sampling and failed to capture seasonal variations or peak exposure risks from episodic discharge events. Given the high polarity and biological activity of psychoactive substances， continuous monitoring is warranted to assess their long-term ecological implications.