Identifying the hotspots of nitrate leaching and its key driving factors in the Yellow River Delta using DNDC model

The issue of nitrate leaching poses a substantial risk to the safety of groundwater resources. A critical aspect of mitigating this risk involves the quantification of the spatial heterogeneity of nitrate leaching and the identification of its primary drivers. In the present study, we developed a county-level DNDC database for the year 2020, specifically for the Yellow River Delta. This database was utilized to simulate the spatial distribution of nitrate leaching. Furthermore, we employed GWR to analyze the principal factors driving nitrate leaching. Our findings revealed considerable spatial variations in nitrate leaching, with an average value of 40.31 kg N ha^-1. Wudi and Hekou emerged as areas of low risk for nitrate leaching, while the remaining 17 districts were identified as high-risk areas. The spatial heterogeneity of nitrate distribution was primarily attributed to the heterogeneity of the driving factors. The absolute values of the regression coefficients for these factors were ranked in the following order: clay content > pH > organic fertilizer > chemical fertilizer > rainfall > nitrogen deposition. Based on these findings, we propose an optimal management practice that involves a 20% reduction in the use of both chemical and organic fertilizers. This approach could potentially result in a 43.8% decrease in nitrate leaching, with a minimal 3% reduction in crop yield. The insights gained from our research offer a scientific foundation for the development of a management strategy that balances economic considerations with environmental protection.