Risk assessment and spatial-temporal distribution characteristics of nitrogen and phosphorus emissions from agricultural sources in the Yangtze River Economic Belt

Rapid socioeconomic development has intensified nitrogen and phosphorus pollution in the Yangtze River Economic Belt (YREB), posing severe threats to the water environment. Notably, agricultural sources have surpassed industrial sources to become the primary contributor to this pollution. To explore the spatiotemporal characteristics and impacts of agricultural nitrogen and phosphorus pollution in this region, this study constructed an improved output coefficient model. Using panel data from 11 provinces and municipalities in the YREB spanning 2005-2020, combined with Geographic Information System (GIS) spatial analysis tools, we calculated the pollution loads of agricultural nitrogen and phosphorus from three key sources: land use, rural domestic activities, and livestock and poultry breeding (LPB). The results show a consistent downward trend in total nitrogen (TN) and total phosphorus (TP) pollution loads from the three sources. Specifically, TN load decreased from 2,686.68 × 10³ tons/yr in 2005 to 2,035.67 × 10³ tons/yr in 2020, while TP load declined from 139.42 × 10³ tons/yr to 102.52 × 10³ tons/yr, with an average TN-to-TP pollution load ratio of approximately 19.40. GIS-generated spatial distribution maps confirm a widespread reduction in agricultural TN and TP pollution across the region. To effectively mitigate agricultural nitrogen and phosphorus pollution risks, we recommend strengthening research on fertilization techniques for major crops and exploring the establishment of centralized treatment stations for agricultural solid waste in regions within the YREB.