HEAVY-METAL LINKAGES WITH MINERAL, ORGANIC AND LIVING SOIL COMPARTMENTS

For soil ecotoxicological assessment, we can observe lethal effects (o n organism as presence or absence) or sublethal effects due to bioconc entrations of contaminants in organisms. This paper deals with the ana lysis of seven heavy metals (Cd, Cu, Fe, Mn, Ni, Pb and Zn) and Ca: (i ) in soils, by three chemical extraction techniques; (ii) in earthworm tissues; (iii) the relationships between earthworm bioconcentrations and soil heavy metal contents; and (iv) the linkage of these metals wi th different soil components. Sixty soil sites were examined. Soil sam ples were analyzed by three metal extraction techniques: total, acetic acid and dethylene triamine pentacetic acid. The results of soil meta l extractions have been reported in relation to total soil or to vario us soil fractions (organic matter, clay, silt, sand). Data were interp reted using a principal component analysis (PCA) to observe a relation ship depending on soil and earthworm heavy metal contents and soil pro perties. The correlations between earthworm metal body burdens and soi l total contents were positively significant for all metals except Fe and Ni. These correlations varied with the other soil extraction metho ds. The observed correlations could not be interpreted in term of simp le mechanisms due, to the complexity of systems, and could not be used as a tool to predict soil biohazard. The relationships between earthw orm metal bioconcentrations and the various soil metal estimations dep end on many mechanisms which are discussed. The direct measurement of heavy metal concentrations in earthworm tissues is safer for ecologica l assessments. (C) 1997 Elsevier Science Ltd.