Synergistic impacts of anthropogenic and climatic drivers on total phosphorus dynamics in a mega river basin

Abstract

Total phosphorus (TP) pollution in the Yangtze River basin (YRB) severely threatens ecosystems. Previous studies have examined individual factors affecting TP, but the combined impacts of anthropogenic activities and climate factor remain unclear. This study analyzed TP data from 636 sites in the YRB during 2016–2020 using partial least squares structural equation modeling to assess these combined effects on TP pollution. Results showed government regulation significantly reduced TP concentration from 2016 to 2020. Anthropogenic activities, including changes in landscape, GDP, and population growth, significantly influenced TP concentrations. Cropland and impervious surfaces were major TP sources, while forests acted as effective TP sinks. Landscape fragmentation weakened the ability of source landscapes to export TP to water bodies and the purification capacity of sink landscapes, while aggregation enhanced sink capacity. GDP and population growth were positively correlated with TP, but their impacts were partially mitigated by landscape adjustments and policy interventions. Climate factor also significantly affected TP concentrations. Precipitation influenced surface runoff and pollutant generation, playing a key role in non-point source pollution and amplifying the positive impact of landscape sources on TP. Air temperature promoted the release of internal phosphorus by affecting water temperature, water body stratification, and dissolved oxygen concentrations. Wind speed could weaken the release of TP from landscape sources to water bodies. Future efforts should focus on optimizing landscape patterns, enhancing sink landscape aggregation, and strengthening environmental governance, while considering climate impacts in water quality management to ensure the sustainable development of the YRB.