长江口南岸边滩沉积物重金属污染记录的磁诊断方法

MAGNETIC DIAGNOSIS OF HEAVY METAL POLLUTION RECORD IN COASTAL SEDIMENTS ON THE SOUTHERN BANK OF THE CHANGJIANG RIVER ESTUARY

根据长江口南岸边滩南区排污口附近采集的柱样的磁性测量和重金属含量分析 ,探讨了磁性测量方法在沉积物重金属污染记录信息提取方面的应用价值。结果表明 ,磁性参数χARM、χfd% 、χARM/χ和 χARM/SIRM与重金属Cu、Zn、Pb、Cr具有极为相似的垂向变化特征 ,反映了细晶粒亚铁磁性矿物对重金属的吸附作用 ,以及沉积物粒度组成对重金属含量的影响。根据上述相关性 ,建立了利用磁性参数推断重金属含量的线性回归模型。不同柱样基于磁性参数 χARM的层位对比表明 ,不同部位沉积物中的重金属记录可以对比 ,但其含量却存在较大的差异 ,反映了重金属空间分布的复杂性。本项研究表明 ,作为一种辅助手段 ,磁性测量可以在高分辨率的重金属污染研究中发挥重要作用。

This study was aimed to discuss the value of magnetic measurements in the reconstruction of sedimentary heavy metal pollution history. Four sediment cores, collected from sewage outlet on the tidal flat along the southern bank of the changjiang River estuary, were used. Down core profiles of magnetic parameters χ ARM , χ fd% , χ ARM /χ, χ ARM /SIRM, which are sensitive to fine grained ferrimagnetic minerals, showed similar variations with heavy metals Cu, Zn, Pb and Cr. Their similarity is possibly due to the absorption of heavy metals by fine grained ferrimagnetic minerals, and their enrichments in the clay fraction of the sediments. Linear regression models were established to semi quantitatively deduce the concentrations of heavy metals using the simple, quick and non destructive magnetic technique. Core correlation based on magnetic parameters χ ARM indicated that the heavy metal records of different cores can be compared. However, the concentrations of heavy metals varied greatly within a short distance, indicating complex spatial distribution of heavy metals.