太湖五里湖底泥污染特性研究

五里湖是太湖污染最严重的水域。为对其治理提供依据，在该湖区设置了4个采样点，对底泥的表层样、柱状样、间隙水样和上覆水体作了重金属和营养盐分布测试，并作了数据统计分析。结果表明：以地积累指数评价，五里湖底泥的重金属污染程度为轻度，总体可达到《土壤环境质量标准》（GB15618-1995）三级标准，根据超出背景值的倍数分析，五里湖重金属含量顺序为Cu>Cd>Pb>Hg>As>Cr。重金属含量表层（0～5 cm）相对较低，第二层（5～10 cm）和第三层（10～20 cm）是主要的污染沉积层，这与底泥沉积特征是相对应的。表层底泥总氮、总磷和有机质含量较高并具有明显的相关性，相关系数介于0.757 6～0.862 2之间，显示了污染物质的同源性。表层底泥和间隙水中营养盐含量明显高于湖水，相对于湖水呈可释放状态，是湖体内源污染之一。

CHARACTERISTICS OF CONTAMINATED SEDIMENTS IN WULI LAKE OF TAI LAKE

Wuli Lake is one of the most seriously polluted areas of Tai Lake. For the remediation purpose, upper layer sediments, column sediments, interstitial water and lake water from 4 different locations in Wuli Lake were sampled, and the concentrations of heavy metals and nutrients in the samples were tested. The results indicated that heavy metals pollution level was slight compared with the Environmental Quality Standard for Soils（GB15618-1995）, when calculated with Igeo method. The heavy metals ranked in descending order of concentration was Cu>Cd>Pb>Hg>As>Cr. The concentrations of heavy metals in upper layer（0～5 cm） were lower than those in the second（5～10 cm） and third（10～20 cm） layer, which demonstrated as dominant contaminated deposit layers. The phenomenon was correspondent with the deposit characteristics of sediments. The concentrations of TN, TP and OM in upper sediments were high and an obvious correlation between these parameters could be found with the correlation coefficients were between 0.757 6 and 0.862 2. The concentrations of nutrients in sediments and interstitial water were much higher than those in water lake, which highlighted eutrophication as the most important endogenetic water pollution sources in Wuli Lake.