Impact of Land Use on Phosphorus Forms and Pollution Characteristics in the Headwaters of Dongjiang River

The Headwaters of Dongjiang River, as a major water source for the Guangdong-Hong Kong-Macao Greater Bay Area, is facing increasing phosphorus (P) pollution issues due to rapid economic development. This study utilized the ArcGIS Software to analyze the spatial distribution of P forms in the Headwaters of Dongjiang River and their main sources, as well as to investigate the impact of land use patterns and landscape structure on phosphorus forms. The results indicate that P pollution in the Xunwu tributary on the eastern side is significantly higher than in the Dingnan tributary on the western side, primarily originating from artificial surfaces, citrus orchards, and livestock farming as non-point source pollution. Land use structure and landscape patterns significantly influence water quality, explaining over 43.1% of the variance in P concentration changes, with a contribution rate of 63.2% for total P (TP) and particulate P (PP). Among land use types, artificial surfaces show a positive correlation with TP, PP, and dissolved inorganic P (DIP) concentrations. Grassland and shrubland exhibit a negative correlation with DIP concentration, while cropland shows a positive correlation, indicating the significant roles of urbanization and agricultural activities in P pollution. In terms of landscape patterns, patch density (PD) and aggregation index (AI) significantly explain TP and PP concentrations, with an average contribution rate of 18.8%. Moderately fragmented landscape structures can reduce particulate P transport, while regions with high AI values may exacerbate P pollution through pollutant generation and transport mechanisms. This study provides scientific evidence for land use planning and water resource management in the Dongjiang River Basin.