Effect of field aging on nickel concentration in soil solutions

The effect of field aging on nickel (Ni) concentration in soil solutions was studied on three soils, with pH 4.5, 6.1, and 7.6, that were spiked with Ni and aged outdoors for 5, 10, and 15 months. Field aging resulted in a minor decrease in total Ni content and a dramatic decrease in Ni concentration in soil solution. Nickel release isotherms in field-aged soils differ from those in freshly spiked ones. The decrease in soluble Ni in noncalcareous soils at Ni loadings from 25 to 4800mg kg(-1) followed a first-order kinetic equation. In calcareous soil the observed relationships imply that soluble Ni may be controlled by dissolution of a surface precipitate either on the surface of soil carbonates [NiCO3 or NiCO3 center dot 2Ni(OH)(2)] or on the surface of clay minerals (Ni-aluminum double-layer hydroxide).