云南属都湖沉积物金属元素地球化学

Metals geochemistry of the sediments of Lake Shudu, Yunnan Province

通过对属都湖短岩芯Esdr1重金属元素的分析,结合沉积物粒度、流域降水和人类活动资料,讨论属都湖沉积物金属元素地球化学变化特征.结果表明,沉积物中Al、Mg、Co、Zn、Cr、Ti、V、Cu、Ni等元素含量变化与粘土含量、夏季降水量显著相关,降水导致的流域侵蚀强弱变化是影响元素含量变化的主要因素.元素Pb含量从岩芯底部到顶部总体呈上升趋势,25-17.5cm沉积物中Pb含量较稳定主要为自然侵蚀过程控制;17.5-10.5cm沉积物中Pb含量迅速增加后逐渐降低推测为20世纪50年代湖区附近矿山开采产生的粉尘沉降的影响;10.5-0cmPb含量逐渐增加,80年代以后大气中Pb含量上升,Pb在流域的干湿沉降应是岩芯上部Pb含量升高的原因.在氧化还原作用下沉积物中Fe、Mn易在沉积物-水界面发生再迁移,25-7.5cm沉积物中的Fe、Mn含量变化特征为沉积后再迁移作用的结果;7.5-0cmFe和Mn含量明显上升,夏季降水量增加导致流域侵蚀增强和土壤的潜育化可能是岩芯上部Fe、Mn含量显著上升的原因.

Metal profiles of short sediment cores were drilled from Lake Shudu located in Xianggelila County, northwestern Yunnan Province. Core samples were dated by measuring anthropogenic 137Cs. Cluster analysis showed that metals in the core sediments were divided into two groups. The first group of metals （AI, Mg, Co, Zn, Cr, Ti, V, Cu, Ni） has similar concentration profiles to that of clay concentration. Metal concentrations are low at 25-10.25cm and increase towards the surface. The first group metal concentrations are mainly influenced by summer precipitation. The second group metal has different features： at the bottom of the core Pb concentration is low and increase upwards. Pb concentration at 17.5-10cm quickly increased and gradually reduced due to mining activities nearby the lake in the 1950s. High Pb concentration at 10-0cm can be interpreted as air pollution produced by coal and oil combustion after 1986. Concentrations of Fe and Mn at 25-7.5cm are likely caused by remobilization at the sediment-water interface after sedimentation. Fe and Mn concentration at 7.5-0cm significantly increased. Increasing precipitation between 1986 and 2005 resulted in strong erosion and soil gleying within the catchment which maybe the reason of high concentrations of Mn and Fe at the top of the core.