为研究湘江大源渡枢纽底泥中Cd、Pb的污染特征及其生态风险,采集6个断面的18个底泥样品,测定了沉积物中Cd、Pb的总量、化学形态及其生物有效性,并利用地积累指数法和单因子指数法评价其污染程度与等级.结果表明,湘江大源渡枢纽底泥中Cd、Pb存在很强的积累现象,尤其是Cd污染特别严重.各采样点底泥中Cd主要以碳酸盐结合态、无定型铁锰氧化物结合态存在于底泥中,而Pb主要以无定型铁锰氧化物结合态和残渣态存在.湘江大源渡枢纽各采样点底泥中Cd的生物可利用性均达到了一定水平,各采样点底泥中Pb的生物可利用性均极显著低于Cd的生物可利用性(P＜0.01).与《国家土壤环境质量标准》二级标准比较,各采样点Pb尚未超标,但Cd超标33.5 ～ 77.8倍.各采样点底泥的Cd的Igeo值均为6级,已达到了极强的污染程度；各采样点底泥的Pb的Igeo值为2～3级,属于中-强的污染程度.%In order to study the pollution characteristics and ecological risk of Cd, Pb in the sediments of Da yuan du hydropower station of Xiangjiang River, 18 sediments specimens were sampled from 6 sites. Total contents and chemical speciation and bioavailability of Cd, Pb were determined. The index of geoaccumulation and single factor were then employed to evaluated the pollution degree and classification of Cd, Pb in the sediments. The results indicated that there were very high contents of Cd, Pb accumulated in the sediments, especially for Cd. The main chemical speciation of Cd in the sediments were carbonate combined and Fe-Mn oxides combined, most of Pb in the sediments exited as Fe-Mn oxides combined and residual form. Bioavailability of Cd in the sediments of Da yuan du hydropower station was up to a high level, which was very significant higher than that of Pb (P <0. 01). Pb contents in the sediments were not over standard, Cd contents were 33.8 ~ 77. 8 times overran the contents for heavy metal of China Environmental Quality Standard for soils (GB 15618-1995, Grade Ⅱ ). Igeo of Cd in the sediments were up to 6 grade, which indicated Cd pollution degree was very strong; Igeo of Pb in the sediments were between 2 and 3 grade, which indicated Cd pollution degree was moderate to strong.
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