长江(公安段)不同地貌成因类型冲积土中Cd的分布特征

Distribution Characters of Element Cd in Different Physiognomy Type Alluvial Soils of Yangtze River(Gong'an Segment)

长江流域多目标地球化学调查成果显示，长江沿岸冲积带土壤中存在着重金属元素Cd的高值分布。以位于湖北省境内的长江公安段冲积带土壤为研究对象，分析了Cd在不同地貌成因类型浅层（0～20cm）土壤中的横向分布特征，重点研究了Cd横向、垂向分布特征与Corg含量、pH值和黏粒含量（用硅铝率反映）分布特征的关系。结果表明：①研究区浅层土壤中w（Cd）的分布特征为，湖积低平原区、冲-湖积低平原区及冲洪积低洼平原区地貌成因类型土壤中的含量明显高于冲洪积高漫滩平原区、冲洪积高亢平原区地貌成因类型土壤，其质量分数差异达1．4～1．8倍；②研究区不同地貌成因类型土壤中，w（Cd）的横向分布特征主要受黏粒含量分布的控制，其次是w（Corg）；垂向分布特征的主要控制因素是w（Corg）。

The results of multi-purpose geochemical survey show that there exist high value distribution of heavy metal Cd in alluvial soil along the Yangtze River. This paper chooses the alluvial soil of Gong＇an segment of the Yangtze River, located in Hubei Province, as the research object. It discussed the distribution character of element Cd in different physiognomy type topsoils（0-20 cm）, and also mainly researched the relationships between distribution character of vertical and horizontal of Cd and content fluctuation of OrgC, pH and clay（silica-alumina ratio）. The study results show that： ①The distribution of CA in shallow surface soils is characterized as： The content of Cd in lacustrine deposit, alluvial lacustrine and alluvial-diluvial low-lying plain is 1.4 to 1.8 times as high as in alluvial-diluvial high valley flat and alluvial-diluvial high bank physiognomy areas. ②The content variation of CA in horizontal distribution was controlled by clay primarily and OrgC secondly. The variation of OrgC was major factor that affected the content variation of Cd in vertical distribution.