Analysis of non-point source nitrogen pollution in watersheds based on SWAT model

By simulating and estimating non-point source pollution in Luoyang, the sources and spatial distribution of nitrogen pollution sources in this region were revealed, which provided a decision-making basis for further promoting non-point source pollution control and governance. Based on the SWAT model and different scenarios, the non-point nitrogen pollution sources in Luoyang from 2009 to 2018 were quantitatively identified, and the reasons for their changes under different pollution sources and different land uses were analyzed. The results show: From the analysis of different pollution source types, the main sources of non-point source pollution total nitrogen (TN) are nitrogen fertilizer application, atmospheric deposition and soil nitrogen reservoirs, and the pollution brought by livestock and poultry breeding and rural life is relatively low; From the analysis of different land use types, the entry coefficient of each non-point source TN pollution in Luoyang region is ranked as follows: atmospheric deposition (18.1%) > nitrogen fertilizer application (14.7%) > rural life (12.5%) > livestock manure (2.9%) > soil nitrogen pool (0.2%); Different pollution sources have different critical control periods, the key period for controlling natural sources (soil nitrogen pools and atmospheric deposition) is the rainy season, while the focus for controlling anthropogenic sources (rural living, livestock and poultry farming and fertilizer application) is the period of pollution cast emissions. In terms of time, the key period for controlling natural sources (soil nitrogen pool and atmospheric deposition) is the rainy season, while the key period for controlling anthropogenic sources (rural life, livestock and poultry breeding and application of chemical fertilizers) is the period of pollution input and emission; The key pollution sources of different land uses are also different. The key pollution sources of non-point source pollution of garden land and human settlements are nitrogen fertilizer application and domestic sewage, while the three major pollution sources of paddy field and dry land are nitrogen fertilizer application, atmospheric deposition and soil nitrogen pool.