洞庭湖流域水体污染物变化趋势及风险分析

通过对洞庭湖流域1989,1997,1999年水质监测数据进行分析,结果表明:(1)洞庭湖流域磷污染十分严重而重金属浓度较低,除Cu外,其它重金属多年最高浓度均低于国家II类水质标准;(2)水体污染情况有逐年上升趋势,除TN外,其它各污染物数量的增长速度都非常大;(3)点源污染对洞庭湖流域水污染贡献较大,枯水期各污染物浓度均较丰、平水期高。结合国外研究得到的重金属毒性系数,引入外推法得到TN,TP的毒性危害系数,将之应用到洞庭湖流域水体污染物的风险分析中,得出TP风险仍是对洞庭湖流域的污染风险贡献率最大的污染物,而TN,Zn的污染风险相对较小;君山处的污染风险较大,已对其周边生态系统产生了潜在的生态风险,而流域内其它各监测点的风险值偏低。

Changing Tendency and Risk of Water Contamination in Dongting Lake Watershed

By the analysis of water quality monitoring data of Dongting Lake watershed in 1989, 1997 and 1999, it indicated that phosphorus pollution was particularly heavy, but the highest concentration of the heavy metals except Cu in each year was all lower than state water quality standard grade II; water pollution levels increase year after year at a high rate, except contamination TN; point sources make a greater contribution to the pollution of Dongting Lake watershed and concentrations of the contaminates are higher in low water season than in high water season and tap water season. Due to the shortage of research on toxicity harmfulness coefficients of TN and TP, their values are obtained through an extrapolation approach using toxicity coefficients of heavy metals determined abroad. The coefficients are applied furthermore to risk analysis of pollution in Dongting Lake watershed. The research results show that TP contributes most to the pollution risk in Dongting Lake watershed, while TN and Zn contribute relatively less. Additionally, the risk coefficient value at Junshan monitoring site is relatively high, which poses potential ecological risk for its circumference ecosystem. The risk values at other monitoring sites are lower and the potential ecological harm is minimal.