INFLUENCE OF AGING ON COPPER FRACTIONATION IN AN ACID SOIL

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Abstract

Anthropogenic inputs can raise the content in copper of soil to toxic levels. Copper binds to various soil components in a way that dictates its activity and stability in biologically inactive forms. In this work, we determined the distribution of copper bound to different components of an acid agricultural soil as a function of the concentration of Cu(NO3)2 added (viz. 10, 50, 100, 250, 500, and 1000 mg Cu kg−1 soil) and contact time (1, 7, 14, 35, and 500 days) in soil samples that were incubated under field capacity moisture conditions. Based on the results, the distribution of copper fractions is a function of the Cu concentration added to the soil and the incubation time. Thus, the proportions of the most labile Cu fractions (viz. exchangeable Cu and organically bound Cu) decreased with increasing incubation time, whereas those of Cu bound to crystalline and amorphous materials (and residual Cu) exhibited the opposite trend. After 500 days of incubation, the soil pH and the proportion of exchangeable Cu regained values close to their initial levels in the soil samples supplied, with a metal concentration lower than 250 mg Cu kg−1. However, such an incubation time was inadequate to offset the alterations in the copper fractions because of added Cu concentrations more than 500 mg kg−1.

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