淀山湖沉积物PAHs季节分布与风险度指数评价

Season distribution characteristics and the risk index assessment of PAHs in surface sediments of Dianshan Lake

对淀山湖湖体6个站位表层沉积物中多环芳烃(PAHs)进行了季节测定,结果表明,16种美国EPA优先控制的PAHs均有检出,PAHs总含量(干重)波动范围54.6~1331.2ng/g,均值373.4ng/g.与国内外大多数湖泊相比,淀山湖沉积物中PAHs含量水平属中等偏下.总含量季节变化大体为冬季>春季>秋季>夏季.另对出入湖口河流6个站位表层沉积物中PAHs含量测定,表现为入湖口>出湖口>湖体,季节变化特征与湖体相一致.PAHs环数所占比重为4环>5~6环>2~3环,采用特征比值法进行源解析,其主要来源是煤炭和生物质的不完全燃烧,主因子分析显示贡献率为80.22%.基于沉积物质量基准法(SQGs),提出一种PAHs风险量化评价新方法——风险度指数法(RIM),用此方法风险评价表明,部分单体(Acy、Ace、Ant和BaA)风险度指数RI为3.09~3.29,属中等风险水平,大多数PAHs单体风险度指数RI为0.79~2.73,相对处于中低风险水平,总体PAHs风险度指数TRI为2.64,污染状况处于中低风险水平.淀山湖作为上海市一个重要水源地,PAHs污染的潜在风险仍不可忽视.

PAHs contents of surface sediments were tested with seasons from 6 sampling sites of the Dianshan Lake body, The results showed that: 16 kinds of PAHs, which are listed as priority pollutants by EPA, were found in all the samples. The total PAHs concentration(dry weight) reached 54.6~1331.2 ng/g, and the average amount was 373.4 ng/g. Compared with other most areas, the total PAHs concentration of surface sediments of Dianshan Lake, were below the middle level. Seasonal fluctuation of the total PAHs concentration on the average and at the minimum and the maximum was essentially that: winter >spring>autumn>summer. In addition, PAHs contents of surface sediments were tested from other 6 sampling sites of the lake out-inlet, the results were shown as: inlet>outlet>the lake body, and the seasonal characteristics were consistent with the lake body. Ring contents of PAHs share quantity: tetracyclic>pentacyclic to hexacyclic>bicyclo to tricyclic, by characteristic ratio method, source analysis showed that most of PAHs were originated from incomplete combustion of coal and biomass, which contributed 80.22% by Princical factor analysis. Based on Sediment Quality Guidelines(SQGs), this paper proposes a new method of PAHs risk quantitative evaluation——the Risk Index Method(RIM), the assessment result by it showed that the monomers of PAHs(Acy?Ace?Ant and BaA)were at medium level of ecological risk(RI reached 3.09~3.29), While most of the rest monomers of PAHs were at a relatively low to middle risk level(RI reached 0.79~2.73), Pollution status of the total PAHs was at low to middle risk level(TRI was 2.64). Dianshan Lake serves as the mein water source of Shanghai city, the potential risk of PAHs pollution of which should not be ignored.