Abstract
In the present study, Cu activities in 12 calcareous soils were obtained by chelation. Thc Cu activities (pCu) ranged from 11.5 to 13.0. A positive correlation between CaC03 concentration and Cu2t activities was observed, whereas negative correlation was found with Fe203. Direct identification of solid phases controlling Cu solubility in these soils has not been achieved. From the solubility isotherms, it became evident that in most soil solutions, the concentration of Cu was much lower than that determined by the solubility of inorganic precipitates of hydroxides or carbonates. A significant positive correlation between Cu2+ and Fe3t activity does suggest some kind of mechanism which involves copper and iron but which is independent of pH. However, formation of cupric ferrite (CuFe204) is unlikely as the shape of the isotherm does not support this hypothesis.
