Fundamental aspects of metal speciation and transport in metal-contaminated soils and aquifers (FAMEST). Second Annual Report.

Abstract

The aims of the FAMEST project are to apply the latest geochemical methods and models to practical problems of metal toxicity and pollution at metal-contaminated sites. Studies are taking place at sites in the UK, France, Switzerland and the Netherlands. The study areas include polluted sites near old metal smelters, an agricultural field heavily contaminated by sewage sludge some 20 years ago, and an experimental site where different amounts of copper had been added in a controlled way some years ago. One aim is to be able to predict from a minimum number of basic measurements of the affected soils or aquifer materials the present-day pore water concentrations and the speciation of the metals within this pore water. This gives a good idea of the potential toxicity of the water. Once this and the rate of water movement are known, it should also be possible to determine the transport of metals through the affected soils and hence estimate the persistence of the metals in the soils and their potential impact on local water bodies. Key targets being addressed in the F AMEST project are: • to derive a generic set of proton and metal ion interaction parameters for the binding of metal ions to natural organic matter, specifically to fulvic and humic acids and to use these data for the modelling the binding of metals to the organic component of soils and soil solutions (UK); • to develop a set of procedures to characterize metal-contaminated soils using chemical extraction and spectroscopic techniques (EXAFS, EPR) and to use this information to predict the metal concentrations in pore water (soil solution) and its variation with depth (France); • to develop methods for measuring and characterising the transport of metals through soils. In particular, testing various multicomponent transport models for predicting the results of transport experiments with contaminated and control soils (Switzerland); • to develop a method for measuring 'free' (i.e. not complexed by organic matter) metal ion concentrations in soils and solutions using a novel Donnan membrane technique (the Netherlands). The project is designed to cover field, laboratory and modelling studies in about equal measure. In particular, it is hoped that the considerable accumulated experience of the project team in modelling chemical speciation in laboratory systems can be applied to the 'real world'. We hope that the results of this work will be transferred to the wider world in terms of revised working procedures and improved computer models. These can then be incorporated by others into future risk assessments