Pollution in Dongting Lake and its Risk Assessment After the Closure of the Three Gorges

Through the analysis of water quality monitoring data of the Dongting Lake from 2003 to 2009,we obtain that TN、TP pollution is particularly heavy,and the pollution of TN is the most heavy in the East Dongting Lake,slighter in the West Dongting Lake,slightest in the South Dongting Lake,while the pollution of TP is heavier in the East Dongting Lake,slighter in the West Dongting Lake and in the South Dongting Lake.The concentrations of pollutions before and afer the closure of the Three Gorges points that we should increase the nitrogen and phosphorus removal process in the urban sewage treatment plant.Pollutant risk analysis shows that TP is the most contributive elements for the pollution risk of water body in the Dongting Lake Watershed,Cu is second,and other pollution risk value is very small.The total risk value at each monitoring state is slight ecological harmfulness.In the West Dongting Lake,it has a serious pollution risk,and pollution risk of the east Dongting Lake,South Dongting Lake is slighter.