Identification To The Critical Source Of Area Agricultural Non-Point Source Pollution In Ash River Basin

Point source pollution has been effectively control and governance,and agricultural nonpoint source pollution contribute to the deterioration of water environment increasingly prominent. Therefore, people focus attention on the study of the mechanism and agricultural nonpoint source pollution control measures. Songhua River is a major grain production base in the Northeast and industrial concentration, but also concentrated area in Heilongjiang province’s major urban agglomerations. Ash River is the main tributary of the Songhua River.In recent years, with the rapid development of the economy, Ash River basin water environment problems have become prominent, increasingly attracted the attention of the relevant authorities. Therefore, a better solution to Ash River Basin water environment safety issues is important for the quality of the local environment and the health of local residents and other aspects.This paper selects15towns tributary of the Ash River Basin:the outskirts of Harbin, a high level of urbanization, high intensity agricultural production, livestock scale continues to expand, quality of water from upstream to downstream becoming more worse as the basic unit of study,Firstly,estimates of agricultural and rural sources COD, TN and TP emissions load, and then identify the Ash River critical source areas by means of MUSLE model, to determine the key areas of pollution prevention for Ash River basin management agencies and levels of government, as well as to provide basis for decision making in rural environmental protection and technical drawing for other areas of Harbin or Songhua River.The main conclusions are as follows:(1) The order of various sources of pollution in2011agricultural nonpoint source pollution contribution is:chemical fertilizer>live stock>rural life pollution>soil erosion>straw pollution; various pollutants on the Ash River agricultural nonpoint source pollution contribution order is: TN> TP> COD.(2) In the real emissions of the three pollutants the township of Ash River Basin, COD discharge volume maximum, TN Second, the physical TP emissions is relatively small. But after standard treatment, the standard COD load is the lowest, such as TN and TP standard loads are higher, The main pollutants in the township have also changed, but the same sort of pollutants in different towns pollution levels remain unchanged. Poplar town and solidarity township agricultural nonpoint source pollution is most serious. (3) Among the five sources of pollution of agricultural nonpoint source pollution inAsh River, caused by high chemical fertilizer high TN, TP concentrations resulted in midstream Ash River Plain relic, Yagou,Liaodian,Jiaojie, Xinhua, Xiangyang and so on most polluted fertilizer, Da Ling, Xiao Ling, poplar and Shuangfeng livestock pollution is most serious, only Xingfu township is a highest contamination.(4) Using the MUSLE model to identify critical source areas, and geometric grid computing soil erodibility, topography, drainage and crop management distributed four single risk factor to get watershed risk index.To score the frequency curve as the basis, using equal interval classification scheme, to put Ash River Basin agricultural nonpoint source pollution into four risk level:low, medium, higher, and the highest level of risk, including the risk of the proportion of the area were58.30%,33.59%,6.22%,1.90%.(5) In the risk level distribution of the township, Xiaoling,Yuquan,Jiaojie,Hongxingand Daling agricultural nonpoint source pollution is more serious risk, the highest risk and higher risk pollution area of accounting for71.09%of the entire study area,they are nonpoint source pollution critical source areas of Ash River. Watershed management should be targeted prevention focused on these areas in future.