Mobility and bioavailability of trace metals in temperate and tropical soils
The main aim of our research in this field is to collate and generate relevant datasets, to seek a better understanding of the behaviour of trace metals in tropical soils. The mobility of trace metals such as Cd, Cu, Pb and Zn, and their bioavailability to sensitive receptors in terrestrial and freshwater environments, is strongly influenced by the partitioning of the metal between the solid and dissolved fractions of the soil (often referred to as the K d). Traditional measures of ‘total’ metal concentration are not always, or even usually, appropriate for considerations of metal mobility and bioavailability. Of more relevance are critical concentrations, or critical limits, based on the more readily available metal fractions. Critical concentrations of trace metals in soils, whether measured or predicted from models, are useful in risk assessment, for example, to assess plant exposure to soil metals via root uptake or transport into surface or ground waters. Research on critical concentrations has progressed in recent years, not least to feed into initiatives on critical loads of metals. These models have been based on data from temperate soils and, considering the fundamentally different soil chemistry of the major tropical soil types, it is unlikely that such models could be applied successfully in the tropics. In particular, the major tropical soil types, particularly oxisols and ultisols, are distinguished from most temperate soils by low activity clays, low organic matter contents, low pH values and high levels of Fe oxides. Therefore, we are now conducting research on the behaviour of trace metals, such as Pb, Cd and Cu, in tropical soils which have been contaminated by aerial deposition.
Publications
Hassanien, M.A., Rieuwerts, J., Shakour, A.A. and Bitto, A. (2001). Seasonal and annual variations in air concentrations of Pb, Cd and PAHs in Cairo, Egypt. International Journal of Environmental Health Research 11,13-27.
Lofts, S. et al. (including Rieuwerts, J.S.). (2007). Critical loads of metals and other trace elements to terrestrial environments. Environmental Science and Technology 41, 6326-6331.
Rieuwerts, J.S. (2007). The mobility and bioavailability of trace metals in tropical soils: a review. Chemical Speciation and Bioavailability 19, 75-85.
Rieuwerts, J.S., Ashmore, M.R., Farago, M.E. and Thornton, I. (2006). The influence of soil characteristics on the extractability of Cd, Pb and Zn in upland and moorland soils. The Science of the Total Environment 366, 864-875.Rieuwerts, J.S., Austin, S. and Harris, E.A. (2008). Contamination from historic metal mines and the need for non-invasive remediation techniques: A case study from southwest England. Environmental Monitoring and Assessment (in press).
Tipping, E., Rieuwerts, J., Pan, G., Ashmore, M., Lofts, S., Farago, M. and Thornton, I. (2003). The solid-solution partitioning of heavy metals (Cu, Zn, Cd, Pb) in upland soils of England and Wales. Environmental Pollution 125, 213-225.