The Relationships Between Nitrogen Non-point Source Pollution In Weihe River And Human Activities In Its Watershed

The development of economy and society in Shaanxi province has been restricted seriously by the pollution in Weihe river. The nitrogen pollution which accounts for a large proportion in the polluted river mainly caused by human activities. In order to reasonably and effectively control and alleviate the water quality pollution of the Weihe river, it is necessary to make clear the factors of human activities which affect the non-point nitrogen pollution. For this purpose, combining with the practical situation and the data condition of the Weihe basin, on the basis of selecting the reasonable method that estimates the pollutant loads, analyzing the characteristics and source of nitrogen pollution, and studying the methods of pollutant load division, the author further analyzed the major human activity factors which affect non-point TN pollution to formulate some reasonable measures to alleviate the water quality pollution of the Weihe river. The main findings are as follows:(1) In order to select the reasonable method for estimating non-point pollution load, eight load estimation methods were selected, their structure characteristics were analyzed, and tested by the monitoring data of sediment.(2) The characteristics of nitrogen pollution in the mainstream of Weihe river were carried out by analyzing the annual mean concentration and load of three nitrogen components and TN, and that in wet season, normal season and dry season, and the change trend of the point and non-point source TN load at Huaxian station from 1976 to 2000. The linear correlation and the stepwise regression methods were used to analyze the cause of formation of the characteristics of the nitrogen pollution.(3) The total load of pollution is composed of point source and non-point source load. On the premise of obtaining a little monitoring data of point source TNload and the total annual TN load, the author attempted to utilize the increasing rate of GDP to estimate the point source TN annual loads for the period of no monitoring data. And the results were compared with the non-point TN loads that were calculated by the runoff division method. The result showed that this method is feasible.(4) Multi-regression method was used to analyze the relationships between the nitrogen non-point TN loads which were calculated by the simulated point TN loads and the indexes of human activities in Weihe basin. The result showed that the factors which greatly affect the change of the non-point source TN load are agriculture and farming activities in Weihe basin, and the number of big live-stock is the projecting factor. On the basis of pollution condition in Weihe, some reasonable measures that control and alleviate the nitrogen pollution in the Weihe river were proposed.