From source to stream: CEC source identification and quantification in the Changle River Watershed.

Contaminants of emerging concern (CECs), including pharmaceuticals and personal care products (PPCPs) and endocrine-disrupting chemicals (EDCs), have raised increasing concerns due to their persistence and potential ecological risks in freshwater systems. However, the spatial characteristics and source contributions of CECs in river networks remain insufficiently understood. In this study, we developed an integrated source apportionment framework by coupling spatial statistics, multivariate statistical analyses, and receptor model to unravel the dynamic and origins of CECs in the Changle River watershed. Widespread of CEC contamination was observed, with average total concentrations ranging from 66.2-191 ng L-1 and 51.4-498 ng L-1 in the main channel, and 105-477 ng L-1 and 39.3-1970 ng L-1 in tributaries across wet and dry seasons, respectively. Integrated spatial and multivariate analyses identified anthropogenic hotspots, with untreated sewage (37.6 %) and swine wastewater (39.5 %) as primary sources, while WWTP effluents contributed minimally (9.77 %). Network analysis further revealed pollutant correlations, implying shared geochemical behaviors or common origins. The results highlighted a complex interplay of point and non-point sources, underscoring the need for tailored source control and integrated watershed management strategies to reduce ecological and health risks posed by CECs.