Heavy metals in some French forest soils: Distribution, origin and controlling factors

Abstract

The lowest heavy metal contents are observed in acid soils while the highest contents are in the mollic andosol and in the calcaric cambisol. Cr and Ni concentrations increase with depth in all soils, except the podzol. Co, Cu, Zn behaviour depends on the soil. Cu and Zn decreases with depth in some acid soils. Pb and Cd accumulate in all surface horizons. In the dystric planosol and stagnic luvisol, heavy metals accumulate in deep soil horizons (important clay content). The abundance order of heavy metal contents in soil profiles is: Cr>Zn>Pb>Ni>Cu>Co>>Cd. Almost all heavy metals are mainly correlated to soil pH, iron and aluminum oxides (mainly Cu and Zn), but also to clay content, organic matter and CEC depending on the metal. Ni and Cr are the only heavy metals related to CEC. Pb is related to clay content in acid soils. The highest Pb content concerns a soil located in the N-NE part of France. Pb presents a significant enrichment in surface horizons from various soils in this area which receives significant acid atmospheric pollution. Lead isotopes corroborate the anthropogenic inputs and particularly the influence of leaded gasoline compared to industrial emissions or airborne particles.