长江水下三角洲沉积物柱状样重金属垂向分布特征

Heavy metal characteristics in the sediment cores from the Changjiang subaqueous delta

对长江水下三角洲3个沉积物柱状样进行粒度分析、^(210)Pb测年,并测定其中Cr、Cu、Pb、Zn等重金属元素和Al等常量元素的含量,得到了沉积物粒度、粘土含量、重金属含量的垂向分布曲线和沉积物测年数据。通过相关分析来研究沉积物中的Cr、Cu、Pb、Zn等重金属、粒度、Al相互之间的关系;以Al为参照元素对这4种重金属进行归一化处理,分析其归一化前后的垂向分布特征。结果表明,Cr、Cu、Pb、Zn 4种重金属元素在此区域的地球化学行为相似,其分布受细颗粒沉积物的吸附和胶体的絮凝作用共同控制;近一二十年来,该区域的Cr、Cu、Pb含量并没有显著增加,Zn有轻微污染。此外,CJ19柱中Cu存在异常峰值,可能是特大风暴潮事件对研究区浅水区底质沉积物中重金属的分布造成的影响。

During April 2009, three sediment cores were collected from the Changjiang subaqueous delta. Grain-size analysis, 210Pb dating and element analysis were carried out to date the cores and obtain the vertical distribution patterns of grain-size, clay materials and heavy metal elements. Based on correlation analysis, relationships among four heavy metal elements （i.e., Cr, Cu, Pb and Zn）, common elements （i.e., A1 and Fe） and grain-size were derived. Using A1 as a reference element, four heavy metal elements （i.e., Cr, Cu, Pb and Zn） were normalized to analyze their vertical distribution characteristics. These elements were found to have a similar geochemical behavior; and their distributions were controlled by both absorption of fine-grained sediment and colloid flocculation. For the last one or two decades, Cr, Cu and Pb contents in the study area did not show significant increases, whilst the Zn content patterns were indicative of some light pollution in the area near the Changjiang River mouth. In addition, storm events may have influenced the distribution of heavy metal elements in shallow water areas of the study area.