[Occurrence Characteristics, Pollution Sources, and Risk Assessment of PPCPs in Tongtian River System in the Source Area of the Yangtze River].

As a key ecological function area of water conservation, the water environment quality in the source area of the Yangtze River plays an important role in maintaining the stability of the aquatic ecosystem and protecting the health and safety of coastal people. To clarify the occurrence characteristics, pollution sources, and ecological risks of pharmaceuticals and personal care products （PPCPs） in the Tongtian River, water samples were collected from 14 sampling sites along its mainstream, traversing regions including Zhiduo County and Yushu City. A combination of solid-phase extraction and ultra-high-performance liquid chromatography-tandem mass spectrometry （UHPLC-MS/MS） was employed to determine 52 types of PPCPs belonging to six categories in the water samples. The concentration levels and occurrence characteristics of these PPCPs were analyzed, and their correlations with physicochemical factors in the water, as well as land use structure, were explored. Furthermore, the potential ecological and human health risks posed by PPCPs in the water were assessed using the risk quotient （RQ_E and RQ_H） method. The results revealed that a total of 39 types of PPCPs were detected in the typical river segments of the Tongtian River, with concentrations ranging from non-detectable （ND） to 58.57 ng·L^-1. The total concentrations of the six PPCPs categories varied between 0.92 and 166.39 ng·L^-1, with the average concentration following the order： quinolones （11.89 ng·L^-1） > estrogens （3.61 ng·L^-1） > macrolides （1.58 ng·L^-1） > sulfonamides （0.64 ng·L^-1） > tetracyclines （0.22 ng·L^-1） > chloramphenicols （0.07 ng·L^-1）. Notably, six PPCPs, including ofloxacin, norfloxacin, and ciprofloxacin from the quinolone group and diethylstilbestrol, hexestrol, and dienestrol from the estrogen group, were detected at all 14 sampling sites, with a detection rate of 100%. Mantel test analysis showed that sulfonamides, quinolones, tetracyclines, and macrolides were positively correlated with TOC concentration, while chloramphenicols were positively correlated with ammonia nitrogen concentration. Based on the analysis results of the APCS-MLR model, it was inferred that the first pollution source affecting the differences in PPCPs occurrence was the built-up area, the second pollution source was the pasture, and the unknown pollution sources were bare land and upstream water. CTC, CAM, and EE2 in the collected water samples presented low risk； OFL, NOR, ETM, RXM, and E1 showed medium risk； CIP and E2b had high risk. The RQ_E values of the remaining 29 types of PPCPs were all below 0.01, indicating no ecological risk. The RQ_H values of 39 types of PPCPs for human health risk were all below 0.01, and the risk to human health could be ignored.