三峡工程截流后洞庭湖水体污染及风险分析

通过对2003-2009年的监测数据进行分析,得出:洞庭湖TN、TP污染较严重,TN在东洞庭湖污染最严重,西洞庭湖较轻,南洞庭湖最轻;TP在东洞庭湖污染较严重,南洞庭湖和西洞庭湖较轻。2009年Cu、Zn、Pb、Cd、As、Cr各重金属都达到了国家地面水环境质量Ⅰ类标准。三峡工程截流前后污染物浓度值变化情况显示,应增加城镇污水处理厂脱氮除磷的工艺,降低TN和TP给湖区带来的富营养化风险,同时还必须加强污染严重河段的底泥清淤。通过污染风险分析可知,TP仍是对洞庭湖污染风险贡献率最大的污染物,其次是Cu,其他各污染物的风险值均比较小。各监测点都属于轻微的生态危害。西洞庭湖污染风险最大,东洞庭湖、南洞庭湖相对较小。

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.