基于地球化学调查的丹江口库区土壤氮磷流失风险评估OA

[Objective]This study aims to reveal the spatial distribution characteristics and loss patterns of soil nitrogen(N)and phosphorus(P)in the Danjiangkou Reservoir area,identify high-risk zones of N and P loss,and evaluate the mitigation effect of the Grain for Green Program on N and P loss.[Methods]Based on the 1꞉250 000-scale soil geochemical survey comprising 5 251 topsoil sampling points in the reservoir area,Kriging interpolation and ArcGIS spatial mapping were employed to characterize the spatial distribution patterns of soil N and P.A comprehensive risk assessment method for N and P loss was developed using the Soil and Water Assessment Tool(SWAT)model by integrating source intensity,transport risk,and receptor sensitivity,and the spatiotemporal characteristics of N and P loss loads were simulated.Three Grain for Green scenarios,with afforestation proportions of 10%,30%,and 50%,were established to evaluate their mitigation effects on N and P loss.[Results]The distribution of soil N and P showed a"high in the south and low in the north"pattern,with high-value areas located in the southern mountainous forest regions and low-value areas concentrated in the northern and central agricultural hilly and valley areas.High N/P loss-load zones were mainly located in the northern and central agricultural areas,whereas high-sensitivity zones showed the opposite spatial pattern.The loss loads exhibited significant seasonal variation,with losses during the flood season(May-October)accounting for 80.4%and 82.8%of the annual N and P losses,respectively.The Grain for Green Program significantly reduced N and P loss;when the afforestation proportion reached 50%,the loss loads of total nitrogen(TN)and total phosphorus(TP)decreased by 70.32%and 71.87%,respectively.[Conclusions]Rainfall is the primary driving force of soil N and P loss,whereas land use and agricultural fertilization are the key anthropogenic factors.The Grain for Green Program can reduce the risk of N and P loss by decreasing surface runoff and soil erosion,and these findings provide a scientific basis for nonpoint-source pollution control and ecological management in the reservoir area.