中文摘要：

对沅江入湖沉积物进行钻探取样,利用等离子质谱仪（ICP-MS）对沉积物重金属进行分析。结果表明：重金属Ba、Sc、V、Th、U、Cu、Co、Ni、Cr等在沉积物中含量变化相对稳定,分布相对均匀;而Mn、Zn、Pb、Mo、Cd、Tl、Bi等重金属的含量变化大,分布不均匀。重金属含量柱状剖面变化特征及富集系数（EF值）的计算结果显示：沉积物中Cd达显著富集,而Sc、V、Mn、Pb、Bi等为中等富集程度。沉积物中存在3个重金属富集层,即中下部Pb、Tl、Bi富集层;中上部Pb、Cr、Ni、Cu富集层;浅表部V、Cr、Mn、Ni、Cu、Zn、Pb、Cd、Tl、Bi等多种重金属富集层。地累积指数（Igeo）和综合富集指数（EI）评价结果显示：沅江入湖沉积物重金属污染程度自河床深部向浅部,污染程度趋于增强,污染元素组合趋于由Pb-Bi的单一元素组合向由V-Cr-Mn-Ni-Cu-ZnPb-Cd-Bi组成的复合元素组合变化。且自上游向下游,沉积物重金属污染程度趋于降低。这种重金属污染空间变化特征与区域人为活动有关,值得进一步研究。

英文摘要：

The river inlet sediments were collected from three sediment cores sampled by drilling in the inlet area of the lowermost Yuanjiang River （China） in this study, and concentrations of heavy metals in the sediments were analyzed using the ICP-MS techniques. The results show that concentrations of heavy metals Ba, So, V, Th, U, Cu, Co, Ni and Cr in sediments are less variable, and they are relatively homogeneously distributed in all the sediments. However, concentrations of metals Mn, Zn, Pb, Mo, Cd, T1 and Bi are significantly variable, and they are distributed heterogeneously in the sediments. The depth variations of concentrations of the heavy metals in sediments of the three sediment cores suggest that there are three layers of sediments that are relatively enriched in different heavy metals. They are the middle-lower layer of sediments that are relatively enriched in heavy metals Pb, T1 and Bi; the middle-upper layer of sediments that are relatively enriched in heavy metals Pb, Cr, Ni and Cu; and the upper surface layer of sediments relatively enriched in heavy metals V, Cr, Mn, Ni, Cu, Zn, Pb, Cd, T1 and Bi. The principal analysis results show that most samples from the upper surface layer of sediments, and some from the middle-upper and middle-lower layers of sediments are enriched in different heavy metals. The degree of heavy-metal contamination is assessed using the geo-accumulation index （Igoo） and synthetic enrichment index （El）, and the results show that the degree of heavy metal contamination in the bed sediments of the lowermost river is increased from the middle lower to the upper surface layer of sediments, and along with such depth variation the contamination is changed from the single Pb-Bi assemblage to the complex V-Cr-Mn-Ni-Cu-Zn-Pb-Cd-Bi assemblage. Also the degree of the heavy metal contamination decreases from the upper river to the lower river sediments. Such spatial variation of heavy metal contamination in the bed river sediments of the lowermost Yuanjiang River is believed to