淀山湖沉积物PAHs季节分布与风险度指数评价

PAHs contents of surface sediments were tested with seasons from 6sampling sites of the Dianshan Lake body, The results showed that: 16kinds of PAHs, which are listed as priority pollutants by EPA, were found in all the samples. The total PAHs concentration (dry weight) reached 54.6~1331.2ng/g, and the average amount was 373.4ng/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 6sampling 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.