Nitrogen Non-point Field Pollution in China:II Establishment of Index System for Evaluation of Pollution Degree

Based on the previous study, the index system for evaluation of nitrogen fertilizer pollution and the preference usage order of the system was set up, which was consisted of establishment of index to evaluate the regional nitrogen non-point pollution with statistic data and grading of pollution, set up different methods to evaluate the nitrogen non-point pollution of microcosmic or micro regional, the priority of evaluation criterion was established, the aim of which was to comparation the different study results with the relatively uniform index system.Index of regional nitrogen non-point pollution has five pollution grades.Index for microcosmic or micro regional were consisted of:four types based on nitrate contents of groundwater, four types based on absolute losses of soil nitrate, four types based on relative concentration losses of soil nitrate, four types based on determination of soil nitrate.