Pollution Source Apportionment of Hengyang Section of the Xiangjiang River Main Stream Using APCS-MLR Receptor Model

To explore the pollution characteristics and sources of surface water in Hengyang section of the main stream of the Xiangjiang River, this study employed the Absolute Principal Component Score-Multiple Linear Regression (APCS-MLR) receptor model to analyze monthly water quality monitoring data of 23 water quality indicators from 10 surface water monitoring sites from 2020 to 2025. Qualitative identification of pollution sources and quantitative calculation of source contribution rates were obtained. The results show that the pollution sources in the Hengyang section of the Xiangjiang River main stream mainly include five categories: urban domestic sewage, industrial point sources, tailings ponds, agricultural non-point source pollution, and natural factors, with contribution rates of 10.3%, 19.5%, 28.8%, 14.3%, and 19.2%, respectively. Agricultural non-point source pollution is the primary source of total phosphorus (TP) and total nitrogen (TN), with contribution rates of 71.7% and 33.9%, respectively. Tailings ponds, industrial point sources, and natural factors are major contributors to heavy metal pollution in the river basin.