Enviroment Quality Assessment Of Shallow Groundwater In The Area Of Dongting Lake

The shallow groundwater is the main drinking water source in the countryside, and the quality of that affects people's health directly. Therefore, to comprehensively evaluate groundwater in Dongting Lake area and understand the status of groundwater quality has an important significance for exploitation, prevention and control of water pollution, the economic development and environment protection.Through a great deal of field investigation, collecting 1,720 shallow groundwater samples, laboratory and analysis of its elements in 34 kinds. The exceptional data are removed by Grubbs statistical method and PauTa statistical method, the probability distribution of the data and the environment background values of different groundwater are obtained by applying mathematical statistics and SPSS statistical software, finally fuzzy complex method and BP neural network method are used in groundwater quality evaluation of Dongting Lake area, some conclusions were obtained as the following:1. According to hydrogeochemical theory, it analyzed 34 elements geochemical background values in the area of shallow groundwater, for the next groundwater pollution mechanism and solute transport research laid a foundation.2. The various types of groundwater of each element geochemistry characteristic was analyzed and compared, and draw each element environment quality classification figure.3. Fuzzy comprehensive evaluation method and the BP neural network method are used to evaluate environmental quality of the shallow groundwater of Dongting Lake. According to the results of the evaluation, and groundwater quality evaluation sketch have been drawn. According to fuzzy comprehensive evaluation method from class I to V the water distribution area ratio is 2.3%, 14.53%, 45.75%, 20.56%, 16.86%; BP neural network method from class I to V the water distribution area ratio is 3.1%, 16.89%, 47.66%, 22.21%, 11.63%.4. After compae the results of the evaluation, most of them are nearly the same, the results are objective and accurate. But big differences on monitoring points polluted by single element is due to excessive fuzzy comprehensive evaluation weights which make other factors lose their effect. BP artificial neural network method can overcome some man-made factors of the traditional methods which exist in the process of selecting weight and constructing subjection function, and its own good fault-tolerant ability and non-linear approach mapping ability can make the results of evaluation more objective and accurate. Therefore, BP neural network evaluation method is more suitable for shallow groundwater environmental quality assessment of Dongting Lake.