在黄河中下游干流采集6个表层沉积物样品，采用Han和Banin连续提取法提取并采用ICP?MS和ICP?OES测定不同化学形态的Pb、Cu、Cd、Cr、Ni、Zn、Mn含量，在计算重金属富集因子、迁移系数、次生相和原生相分布比值的基础上，对重金属赋存形态、迁移能力、生物活性、污染状况和潜在生态风险进行了研究．结果表明，黄河中下游干流表层沉积物中重金属元素含量沿河流向先增加后降低，高含量点位出现在汜水汇入黄河后，支流的输入对黄河重金属含量具有较为明显的贡献．形态分析研究表明，Pb、Cu、Cr、Zn、Ni等5种重金属残渣态在其不同形态中有绝对优势，Cd可浸取态占明显优势，Mn的残渣态与可浸取态所占比例相当．富集因子分析表明，黄河中下游表层沉积物中重金属可分为3类：Cu、Cr、Mn基本无富集，Pb、Ni、Zn轻度富集，Cd中度到极高度富集；迁移系数研究表明黄河中下游表层沉积物重金属迁移系数和生物活性顺序为Mn＞Cd＞Zn＞Ni＞Pb＞Cu＞Cr．次生相原生相比值法表明Cu、Cr、Ni、Zn无污染，Pb在3点位轻度污染，其它点位无污染，Mn在1、3、6点位轻度污染，其它点位无污染．综合各种评价方法， Cd是黄河中下游沉积物中污染程度最高的重金属，具有潜在生态风险，应引起重视．
Six sediment samples were collected from the mainstream of middle and lower reaches of the Yellow River. Han and Banin′s squential extraction procedure was used to extract five chemical fractions ( exchangeable, carbonate, Fe?Mn oxides, organic and residual) of sediment heavy metals (Cu, Cd, Cr, Ni, Zn, Mn, Pb). Heavy metal concentrations in each fraction were measured by ICP?MS and ICP?OES. The pollution characteristics, chemical fractions distribution, mobility, bioavailability and potential ecological risks of the heavy metals in sediments were evaluated based on enrichment factors ( EF) , mobility factors ( MF) and the ratio of labile and residual fraction. The results showed that heavy metals in the sediments increased from station 1 to station 3 and then declined from station 3 to station 6. Levels of heavy metals reached maximum at station 3, downstream of the input of Shishui River, which indicated the input of tributaries was an important factor for the Yellow River. Sequential extractions suggested that Pb、Cu、Cr、Zn and Ni were mainly composed of residual fractions, Cd was dominated by labile fractions, while the residual fraction of Mn was nearly equal to the labile fraction. EF of heavy metals indicated that no enrichment occurred for Cu, Cr and Mn, but Pb, Ni and Zn were enriched slightly; Cd was enriched moderately to heavily. The order of MF of heavy metals was Mn>Cd>Zn>Ni>Pb>Cu>Cr. The ratios of labile to residual fraction showed that Cu、Cr、Ni and Zn pollution was insignificant. Pb pollution was light at station 3, but not at other stations. Mn pollution was light at station 1、3、6, but not at other stations. The comprenhensive assessment showed that Cd was the primary element with the highest ecological risk.
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