Influence of Soil Aging and Stabilization with Compost on Zn and Cu Fractionation, Stability, and Mobility

Abstract

To determine the effect of soil aging (1, 12, or 24 months) and compost maturation time on metal redistribution and mobility, soil artificially contaminated with Zn and Cu was stabilized with compost for 35, 24, or 12 months. The compost was produced from municipal sewage sludge, wood chips, rape straw, and grass, matured for 3 or 12 months, then used as a soil amendment at a dosage of 20% (w/w). The total time in each series, including aging of spiked soil and its stabilization with compost, was 36 months. The results showed that soil aging reduced CaCl2 extractable Zn fraction and increased Zn stability (as reduced partition index, IR) more than compost addition, which only reduced Zn mobility in soils that had been aged for 1 and 12 months. However, after soil that had been previously aged 1 month was incubated with compost for one year, Zn mobility started to increase. Composts did not influence the changes in the IR of Zn over time. In contrast, compost addition increased Cu stability more than soil aging did, whereas soil aging and compost addition had a negligible effect on Cu mobility. The IR of Cu in all amended soils averaged 0.51, and reached a maximum of 0.57 12 months after addition of compost to soil previously aged for 12 months. Importantly, the maturation time of compost did not affect the mobility or stability of either metal.