Abstract
This study assessed the effect of common ions on the sorption behavior of copper (Cu) in 10 calcareous top soils from western Iran. Six 10-mM electrolyte background solutions were employed in the study [KCl, KNO3, KH2PO4, Ca(NO3)2, NaNO3 and NH4NO3]. The use of NH4NO3 increased Cu retention in soils, whereas the use of Ca(NO3)2 decreased Cu retention in all soils. Both Na+ and K+ affected Cu sorption equally. Copper sorption was decreased by H2PO, as opposed to NO
or Cl–. The Freundlich distribution coefficient (K
F) decreased in the order Cl– > H2PO
> NO
. Saturation indices indicated that at low and high concentrations, Cu solubility is controlled by adsorption and mineral precipitation reactions, and common minerals in all background solutions (except KH2PO4) are azurite, brochanite, malachite and tenorite. In the KH2PO4 background, the solutions in all soils were saturated with respect to Cu3(PO4)2. Clay content, cation-exchange capacity and Cu-DTPA appeared to be the most important soil properties influencing K
F. The results suggested that the risk of Cu leaching to groundwater is greater in the presence of NO
and Ca2+ than in the presence of other studied cations and anions.