武汉市汤逊湖沉积物重金属垂向变化的磁响应特征及环境意义

对武汉汤逊湖湖泊沉积物T06-1样芯进行了磁性测量、重金属分析和粒度分析,探讨了利用磁参数追踪、指示城市湖泊重金属污染的可行性。结果表明,低矫顽力的亚铁磁矿物主导了沉积物的磁性特征。磁参数,SIRM和ARM与重金属Cr,Zn,Cu和Pb呈现较为一致的垂向变化特征:55cm之下,磁参数值和重金属的含量均较低且稳定;在50~10cm之间,两者基本呈现随深度的减小而增加的趋势,其中在20~10cm区间,出现小范围内波动;而10cm至表层,元素含量和磁参数值随深度减小而急剧增加。选取粘土(（4μm）对沉积物中Cr,Zn,Cu和Pb进行粒度校正的结果显示:校正后元素的变化趋向于平稳,但在表层的10cm处Cr,Pb,Zn和Cu的含量仍然较高,表明了表层沉积物中金属元素的含量主要受人类活动的影响。相关分析也表明了磁参数X1,SIRM和ARM与重金属Cr,Pb,Zn和Cu之间均呈显著相关关系（0.62≤R≤0.86）,表明磁参数可以用于追踪和指示汤逊湖湖泊沉积物重金属污染。

VERTICAL VARIATION OF HEAVY METALS AND IT'S MAGNETIC REPONSE PROPERTY AND ENVIRONMENTAL SIGNIFICANCE IN CORE SEDIMENT FROM LAKE TANGXUN, WUHAN, CHINA

Core T06-1 of 80cm length was collected from the Lake Tangxun, Wuhan, China. Element contents, particle sizes, and magnetic parameters were measured. Whether the magnetic parameters could serve as a proxy for heavy metal contents of lake sediments was discussed. The results showed that low-coercivity mineral magnetite was the dominant remanent magnetic mineral in sediment samples. Magnetic parameters(X1, ARM, and SIRM)showed similar trends as heavy metals(Cr, Zn, Cu, and Pb)along with the core: Both values of magnetic parameters and heavy metal contents were very low and stable below 55cm. Theyn increased gradually between 50～10cm and fluctuated obviously in the upper 20～10cm. At the top 10cm layer, they rapidly increased. The results of Cr, Zn, Cu, and Pb normalized by clay content(4μm)displayed that heavy metal contents showed consistent variation along the sediment core after normalized by clay content, but the heavy metal contents were still higher in the upper 10cm layer. This suggested that the higher heavy metal contents in this layer were influenced mainly by anthropogenic activity. Moreover, correlation analysis also showed that there was a significant correlation between magnetic parameters and contents of element. Based on the results, it indicated that magnetic parameters(X1, ARM, and SIRM )could serve as a proxy to estimate and trace anthropogenically enhanced Cr, Zn, Cu, and Pb in lake sediment.