Baseline 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 Flanders (Belgium) were assessed as a function of clay and organic carbon contents. Outliers in the data were identified and rejected according to statistical criteria. Median trace element concentrations in mg/kg dry weight were As 7, Cd 0.18, Co 0.05, Cr 24.6, Cu 9.6, Hg 0.17, Ni 3.5, Pb 21.5, Zn 34.5. Clay and organic carbon contents were found significant 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 concentrations that have a known probability of being exceeded can be assessed as a function of clay and organic carbon content and used as soil quality reference values.