Heavy metals in Dutch field soils: an experimental and theoretical study on equilibrium partitioning

The prediction of the effects of metals on biotic species, communities and ecosystems is at present seriously hampered by a lack of (quantitative) understanding of the factors that modulate metal bioavailability. Bioavailability needs to be dealt with as a dynamic process, comprising a physico-chemically driven desorption process, and a physiologically driven uptake process. In this report the physico-chemical aspects of bioavailability in a typical Dutch field situation are studied. 49 Dutch soils, selected with the aim of covering a wide range of soil types occurring in the Netherlands, were sampled and the partitioning of 6 metals (Cd, Cr, Cu, Ni, Pb, Zn) and the metalloid As over the soil solid matrix and the pore water was studied. The main soil characteristics determining metal partitioning were quantified and statistical models were derived to describe the partitioning process on the basis of a limited number of easily determinable soil properties. As there is evidence for predominant pore water uptake of metals by organisms living in the soil, the models thus derived provide the first step in predicting the availability for uptake, and hence prediction of toxic effects, of the metals studied