三峡库区香溪河消落区土壤重金属生态风险评价

采用原子吸收光谱法测定香溪河消落区(海拔145～≤175 m)及其上缘(海拔＞175～185 m)土壤中Pb，Cu，Cd和Cr含量. 并用单因子指数法、多因子综合评价法以及Hakanson生态风险指数法评价了土样中重金属综合污染效应. 结果表明，消落区上缘土壤各重金属含量明显高于消落区土壤，多因子综合评价结果表明，前者处于重度污染状态，而消落区土壤基本处于轻度污染状态，部分处于安全或警戒线状态；影响香溪河消落区土壤环境的主要重金属污染因子为Cd，Pb和Cr. 生态风险评价得出4种重金属的生态风险大小顺序为Cd>Pb>Cr>Cu，生态风险指数(RI)在消落区上缘土壤的平均值为219.85，在消落区土壤为34.32，上缘土壤大部分处于重金属中等或可观级生态风险. 可能是由于季节性水淹原因，消落区土壤都处于低等级生态风险. 

Ecological Risk Assessment of Heavy Metal Pollution in Soils from the Fluctuation Belt of Xiangxi River in the Three Gorges Reservoir

Soil samples were collected from the Xiangxi River hydro-fluctuation belt(altitude 145-≤175 m)and its upper margin(altitude>175-185 m) of the Three Gorges Reservoir,and the contents of heavy metals including Pb,Cu,Cd,Cr in the soil were determined using atomic absorption spectrometry.This paper evaluated the soil heavy metal comprehensive pollution effect using the single factor index method,multi-factor comprehensive evaluation method and Hakanson ecological risk index(RI) method.The results showed that the heavy metal contents in the soil of the upper margin of the hydro-fluctuation belt were obviously higher than those in the soil of the hydro-fluctuation belt.According to the multi-factor comprehensive evaluation method,the soil in the upper margin of the hydro-fluctuation belt was heavily polluted.The soil in the hydro-fluctuation belt was only slightly polluted,and a part of it was in a safe and secure state.The main heavy metal pollution factors in the Xiangxi River hydro-fluctuation belt and its upper margin were Pb,Cd and Cr.Ecological assessment determined that the order of ecological risk of the four heavy metals was Cd > Pb > Cr > Cu.The average ecological risk index in the soil of the upper margin of the hydro-fluctuation belt and the hydro-fluctuation belt were 219.85 and 34.32,respectively.Most of the soil in the upper margin of the hydro-fluctuation belt was at medium and considerable level ecological risk from heavy metals.Soil in the hydro-fluctuation belt was at low level ecological risk from heavy metals due to the seasonal flooding.