Location of Trace Elements in Unpolluted Soils by a Combined Method

Abstract

A sequential extraction procedure was combined with physical fractionation and mineralogy to determine the distribution of trace elements (TE) among the different phases of a poorly weathered sample. It was first fractionated into five particle‐size fractions. Two of these were selected for sequential extractions on the basis of their contrasting mineralogical compositions. A five‐step sequential extraction scheme was employed. The studied sample is mostly composed of hornblende, quartz, and feldspars. Early weathering has already occurred, resulting in the formation of smectite and oxides. Sequential extractions show that the studied elements are mostly associated with the residual phases. Hornblende was the main TE bearer of the primary minerals, whereas TEs released through weathering precipitated in both smectite and oxides. Oxides were found to scavenge copper (Cu) and cobalt (Co) more efficiently than smectite. Copper and nickel (Ni) were more concentrated in smectite than in hornblende.

Keywords:

• Distribution among phases
• location
• natural soils
• physical fractionation
• sequential extractions
• trace elements

Acknowledgments

The authors particularly thank O. Josière for X‐ray diffraction analysis and particle‐size fractionation and J. Cattle for English improvements.