苏州古城区域河道底泥的重金属污染分布及生态风险评价

本文分析了苏州古城区域20个代表性断面中8种重金属（Cd、Cu、Cr、As、Mn、Ni、Pb和Zn）的含量，评价了重金属的污染程度和潜在生态风险并甄别了污染来源.结果表明，苏州古城区域河道底泥中Cd、Cu、Cr、As、Mn、Ni、Pb和Zn的平均含量分别为1.1、142.6、90.2、17.2、800.1、63.3、199.1和384.2 mg·kg^-1，超过江苏省土壤背景值的采样点比例分别为100%、100%、65%、95%、70%、100%、95%和100%.利用地累积指数评价发现，8种重金属元素污染程度依次为Pb > Cd > Cu > Zn > Cr > Ni > As > Mn，总体上Pb处于强度污染水平，Cd、Cu、Zn和Cr处于中强度污染水平，Ni和As处于轻度污染水平，Mn处于无污染水平.潜在生态风险指数评价显示，8种重元素的潜在生态风险依次为Cd > Pb > Cu > As > Ni > Zn > Cr > Mn，总体上Cd、Pb和Cu处于中风险水平，其余5种重金属处于低风险水平.古城区域内北部河道和南部河道底泥重金属的平均含量、地累积指数值和潜在生态风险指数值均大于干将河和环城河，水环境重金属治理应重点关注古城区域内部.相关性分析和主成分分析表明，Cd、Cu、Cr、As、Ni、Pb和Zn元素可能源于化肥、路面老化、轮胎磨损和尾气排放等人为因素，Mn则主要源于自然因素.

Pollution Distribution and Ecological Risk Assessment of Heavy Metals in River Sediments from the Ancient Town of Suzhou

The contents of heavy metals (Cd, Cu, Cr, As, Mn, Ni, Pb, and Zn) in sediments from 20 representative sections of the ancient town of Suzhou were analyzed to determine the pollution degree and potential ecological risk, and pollution sources were identified. The results showed that the average concentrations of Cd, Cu, Cr, As, Mn, Ni, Pb, and Zn in river sediments from the ancient town of Suzhou were 1.1, 142.6, 90.2, 17.2, 800.1, 63.3, 199.1, and 384.2 mg·kg^-1, respectively, and the proportions of sampling points that exceeded the soil background value of Jiangsu Province were 100%, 100%, 65%, 95%, 70%, 100%, 95%, and 100%, respectively. The geo-accumulation index indicated that the pollution degree of heavy metals followed the order of Pb > Cd > Cu > Zn > Cr > Ni > As > Mn. In general, high Pb pollution, moderate Cd, Cu, Zn, and Cr pollution, slight Ni and As pollution, and no Mn pollution were observed. The potential ecological risk index for heavy metals was determined to follow the order of Cd > Pb > Cu > As > Ni > Zn > Cr > Mn. Generally, Cd, Pb, and Cu presented moderate potential ecological risk, and the others presented low potential ecological risk. The average concentration of heavy metals, geo-accumulation index, and potential ecological risk index of river sediments in the northern and southern of ancient town were all higher than that of Ganjiang River and Huancheng River, indicating that the control of heavy metals should focus on the inner part of the ancient town. According to correlation analysis and principal component analysis, Cd, Cu, Cr, As, Ni, Pb, and Zn might be derived from man-made factors such as fertilizer, road aging, tire wear, exhaust emissions and so on, which Mn was mainly derived from natural factors.