BASE-LINE CONCENTRATION LEVELS OF TRACE-ELEMENTS AS A FUNCTION OF CLAY AND ORGANIC-CARBON CONTENTS IN SOILS IN FLANDERS (BELGIUM)

Baseline concentration levels of trace elements in the soils of Flande rs (Belgium) were assessed as a function of clay and organic carbon co ntents. Outliers in the data were identified and rejected according to statistical criteria. Median trace element concentrations in mg/kg dr y wt. were As 7, Cd 0.18, Co 0.05, Cr 24.6, Cu 9.6, Hg 0.17, Ni 3.5, P b 21.5, Zn 34.5. Clay and organic carbon contents were found to be sig nificant in predicting soil trace element contents in unpolluted soils . The coefficients of determination ranged from 0.07 (Hg) to 0.69 (Ni) . Based on confidence intervals of the observations, trace element con centrations that have a known probability of being exceeded can be ass essed as a function of clay and organic carbon content and used as soi l quality reference values. (C) 1997 Elsevier Science B.V.