Pharmaceuticals and personal care products (PPCPs) in a multi-source agricultural drainage discharging to the Yellow River, China: Occurrence, spatial distribution and risk prioritization.

The Yellow River, serves as a critical irrigation source in arid North China, yet its drainage system acts as a transport vector for diverse aquatic pollutants. This study investigated the occurrence, spatial distribution, and source-specific risks of 63 pharmaceuticals and personal care products (PPCPs) including 56 antibiotics and 7 other PPCPs in a large-scale drainage system in the river's upper and middle reaches. Predominant substances included cotinine, 1,7-dimethylxanthine, florfenicol and lincomycin with mean concentrations above 59.9 ng/L, showing unique pharmaceutical usage patterns. Total PPCP concentrations ranged from 0.19 to 1.29 μg/L among 46 sites, exhibiting distinct spatial heterogeneity. Positive matrix factorization (PMF) identified mixed rural domestic and livestock wastewater and agricultural non-point pollution as the dominant sources (74.2% totally). Spearman correlation analysis further validated the PMF source apportionment by demonstrating significant positive correlations between most characteristic PPCPs and their respective surrogate source indicators, with additional support from correlation analysis linking these emissions to the coexistence of dissolved organic matters (DOM) and PPCPs. The ecological risk assessment based on probabilistic species sensitivity distribution (PSSD) analysis indicated that freshwater organisms at lower trophic levels were more vulnerable, with predicted no-effect concentrations (PNEC) ranging from 0.05 to 6866 μg/L. While most PPCPs posed negligible risks individually, localized low-to-moderate risks associated with cotinine, ofloxacin, trimethoprim and several co-occurring PPCPs collectively drove significant mixture risks in the Yellow River drainage ditch. Notably, the toxicological priority index (ToxPi) identified clindamycin, florfenicol, and lincomycin as priority antibiotics requiring urgent control. Collectively, these findings underscore the importance of integrating chemical source apportionment with toxicity profiling to support risk-based environmental management.