LONG-TERM REACTIONS OF COPPER(II) IN A CONTAMINATED CALCAREOUS SOIL

The concentrations of total and uncomplexed Cu(II) were measured in water extracts from a soil contaminated at least a half century ago. The total Cu concentration in the topsoil was about 3150 mg/kg of soil. Estimates of uncomplexed (free) Cu based on ion-selective electrode data indicated that at least 99. 5% of the Cu in soil solution was in an organically complexed form. This percentage was decreased by adjusting the soil pH downward. The concentration of uncomplexed Cu in soil solution increased with decreasing pH, but the total soluble Cu was relatively insensitive to pH change. Extraction of the soils with DTPA, pyrophosphate, and other selected reagents, as well as analysis of these extracts by electron spin resonance, revealed that the form of Cu**2** plus adsorbed in the soil was probably largely inorganic.