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Abstract: There are numerous results on the characteristics of metal sorption by total soil samples or soil clay fractions separately. However, not many have focused on the comparison of these characteristics of total soil and clay fraction samples from the same soil. In this study Cu and Pb batch sorption experiments were carried out on samples from the genetic horizons of two Luvisol profiles characterized by vermiculite and montmorillonite as dominant clay minerals, respectively. Freundlich KF and n parameters for Cu and Pb sorption on the total soil samples unanimously show the primary role of the soil organic matter, as well as the preference of vermiculite over montmorillonite in the retention of both metals. These results were effectively completed by those from the experiments performed on soil clay fractions. It was shown that the generally higher affinity of Pb than Cu to the studied soils is primarily due its very strong affinity to the soil organic components. Additionally, in the studied acidic-slightly acidic Luvisol samples sorption of Pb on clay surfaces seems to be much more inhibited when compared to Cu. Consequently, combined study of sorption properties of total soil samples and soil clay fractions helps us in better understanding the sorption process of potentially toxic metals in soils.

Keyword: potentially toxic metals, vermiculite, montmorillonite, Freundlich curve, Luvisol