TRACE-ELEMENT DISTRIBUTION IN SOILS FORMED IN THE INDIANA DUNES, USA

The distribution of trace elements with respect to mineralogy, particle size, and soil depth were determined by X-ray fluorescence analysis and neutron activation analysis in a chronosequence of soils in the Indiana Dunes. Mineral composition, clay mineral content, and aerosol contamination are the key parameters determining the trace element concentrations in these soils. Scandium, Co, As, the light and intermediate lanthanides (La, Ce, Nd, Sm, Eu, Tb), and Th are associated with Fe-rich chlorite and have generally been leached from the E and B horizons. Leaching of the transition elements is in the order Co > Sc > Cr > Mn. Titanium, Hf, Se, and the heavy lanthanides (Yb and Lu), and to a lesser degree Sc, Cr, Mn, Co, and the light and intermediate lanthanides, are associated with heavy minerals (particularly iron oxides) in the very fine sand fraction (0.05-0.1 mm). Leaching of the light lanthanides (particularly Ce) from the E and B horizons and enrichment of the heavy ones is evident. Zinc, P, As, and Sb are concentrated in the clay fraction. Arsenic and Se appear to have been leached although the extent is concealed by atmospheric input. In contrast to Zn, increasing concentrations of Sb in the fine fraction toward the surface appear to be primarily a result of aerosol contamination. Relative adsorption of the alkali elements and Ba to clay minerals are in the order Cs >> Rb > Ba > K. Leaching of K from the upper soil horizons has resulted in increased Rb/K, Cs/K, and Ba/K ratios toward the soil surface.