Speciation, bioavailability and toxicity of trace metals in the aquatic environment

自20世纪初以来，工业活动极大地提高了金属在我们环境中的流通速度。由此产生的“有毒金属”对我们的空气、水和土壤的污染被认为是社会面临的主要环境问题之一。然而，合格的分析化学家发现，环境中仅仅存在一种污染物并不一定意味着该污染物对环境质量有害--对金属尤其如此，因为金属天然存在于环境中，而且同一金属可能以各种不同的形式或“物种”(“形态”=金属在这些形式中的分布)存在。一些金属物种相对无害，而同一金属的其他物种可能具有高度毒性。在过去的20多年里，人们在实验室和合成介质中广泛研究了金属的“形态形成”与其对各种水生生物的毒性之间的联系，并出现了一些有用的共性。然而，对于开始接近自然水域复杂性的系统，人们所做的工作很少。因此，尚不清楚到目前为止获得的实验室成果可以在多大程度上适用于自然系统--目前的研究方案旨在帮助弥合这一差距。整个实验方法是跨学科的，因为它涉及分析化学、地球化学和水生毒理学的各个方面。目前感兴趣的金属既包括必需的微量营养素(例如，铜、锌)，也包括没有已知生物功能的有毒金属(例如，银)。生物“目标”包括淡水藻类和水生无脊椎动物。金属摄取(吸附、积累、亚细胞分配)和生物体反应(生理、生长、死亡)作为暴露介质的(地质)化学的功能被监测。预计这一方案得出的实验结果将有助于环境管理人员不断努力，完善现行的金属水质标准，并开发适用于金属排放的可行的“环境影响监测”技术。

Since the beginning of the 20th century, industrial activities have greatly increased the rates at which metals circulate through our environment. The resulting contamination of our air, water and soil by "toxic metals" is recognized as one the major environmental problems faced by society. However, the mere presence of a contaminant in the environment, as detected by a competent analytical chemist, does not necessarily mean that the contaminant is detrimental to environmental quality - this is especially true for metals, since metals are naturally present in the environment, and since the same metal may be present in various different forms or «species» («speciation» = metal distribution among these forms). Some metal species are relatively innocuous, whereas other species of the same metal may be highly toxic. The link between the «speciation» of a metal and its toxicity to various aquatic organisms has been studied extensively over the last 20+ years in the laboratory, in synthetic media, and some useful generalities have emerged. However, very little work has been done on systems that begin to approach the complexity of natural waters. As a result, it is unclear to what extent the laboratory results obtained to date can be transposed to natural systems - the present research programme is designed to help bridge this gap. The overall experimental approach is interdisciplinary, as it involves aspects of analytical chemistry, geochemistry and aquatic toxicology. Metals of current interest include both essential micronutrients (e.g., Cu, Zn) and toxic metals with no known biological function (e.g., Ag). The biological "targets" include freshwater algae and aquatic invertebrates. Metal uptake (adsorption, accumulation, subcellular partitioning) and organism response (physiology, growth, mortality) are monitored as functions of the (geo)chemistry of the exposure media. It is anticipated that the experimental results derived from this programme will be of use to environmental managers in their ongoing efforts to refine current water quality criteria for metals, and to develop viable techniques for "environmental effects monitoring" (EEM) as applied to metal emissions.