沉积物中重金属的归一化问题——以Al为例

Normalization of heavy metals to aluminum in marine sediments

沉积物的来源、粒度和矿物组成是影响重金属在动力沉积过程中的行为的最显著的因素，用某些参考元素（如Ａｌ、Ｌｉ等）归一化的目的是为了减小沉积物中重金属含量的波动，以揭示人文活动（例如污染）的影响。通过对国内一些河流沉积物中重金属的Ａｌ归一化结果的分析，认为在岩石的风化和变质过程中元素与Ａｌ的相对迁移能力的差异和各种生物过程均可使重金属的Ａｌ归一化值产生显著的变化，在某些情况下Ｍ／Ａｌ值并不一定能准确地描述人类活动对沉积物中重金属的影响。Ａｌ归一化仅能部分地校正粒度分布引起的重金属含量的变化，但不能消除矿物组成的影响。

Origin, grainsize and mineral composition of solids are the most significant parameters controlling the sedimentary variabilities of heavy metals. Normalization to some references materials (e.g. Al, Sc, Li, etc.) is an attempt to minimize the natural variability of heavy metals in sediments, and to identify anthropogenic contributions. Aluminum has been widely used as an index to normalize heavy metals in marine suspended matter and bottom sediments. However, by discussing normalization of heavy metals to Al from five river/estuary sediments, we found that relative mobility of elements to Al (M/Al) in weathering and erosion and biological processes may significantly change the Al normalization values, and M/Al values may not be necessarily reflect the contributions from anthropogenic activities.