Assessment of long-term fate of metals in soils: Inferences from analogues

Abstract

The assessment of the health and environmental impacts of metal contamination in soils is complicated, and in different ways than is the assessment of many other contaminants. One of the foremost problems is that the metals are often relatively immobile, so that it is necessary to verify predictions of mobility and impact far into the future. One approach is to seek analogue information: information from studies that may not have set out to measure attributes related to metal behaviour, but that none the less provide useful insights. One example would be the information on the mobility of natural clays and pedogenic metals such as iron and aluminum in soils. It is well accepted that clay particles will move downward in soils; what is less commonly inferred is that any contaminants associated with the clays will also move downward. For mobility of some metals, this may be a dominant process. Similarly, bioturbation has proven to markedly outpace leaching for many metals. This paper considers analogues related to cesium from bomb-fallout and Chernobyl, other natural radionuclide inputs to the soil, soil pedogenesis, pollen and non-metal industrialage inputs, ancient metal works, and soil fertility management. Related to biological transfers and toxicity, it considers analogy among elements an d among biota, and analogy to ecotoxicology of metals to freshwater biota. Where possible, limiting values for parameters of assessment models have been derived. Key words: Terrestrial, leaching, mobility, ecotoxicity, assessment