Abstract:

Economic development and population explosion are two major driving forces that alter local land use and increase nonpoint source pollution.To overcome the threat of severe pollution and protect limited water resource,it is necessary to develop an integrated evaluation approach to understand the risk of the nitrogen and phosphorous leached from soils in complex land use systems.Based on analysis of factors influencing P and N runoff from fields,a comprehensive index assessment model was designed.To simplify the complex land use,runoff curve number (〖WTBX〗CN〖WTBZ〗) of Soil Conservation Service (SCS) of America was employed to express the differences in surface runoff resulted from different land use,and the equivalent standard pollution index method was taken to calculate the intensity of various type of pollution sources.A case study of Huajiachi Campus,Zhejiang University was taken to evaluate its reliability.The model was modified according to the real situation,to ensure its good performance.The results indicated that the high pollution sources plus high pollutant transportation potential can result in high risk of nitrogen and phosphorous leaching.The residential area,stock farm and heavy fertilized farm were high risk areas,while areas with well vegetation covered had low risk.The assessment model established in the paper can be applied to evaluate runoff potentials of N and P leached from complex land systems.

Key words: soil nitrogen and phosphorous runoff, complex land use system, critical area, comprehensive index method