Influence of Fly Ash and Other Amendments on Leaching of Soil Nutrients and Metals from a Calcareous Soil

Abstract

The influences on the leaching of soil nutrients and heavy metals by separate application to a calcareous soil of fly ash, biosolids, N-viro soil, co-compost, and yard waste compost in comparison to a control without an amendment were determined in a pot experiment. The results showed that the concentration of NO3-N in leachate from biosolids was significantly higher than in leachate from other treatments. The levels of heavy metals found in the leachates from all amended soils were so low as to suggest these amendments may be used without risk of leaching significant amounts of these elements. Nevertheless the level of heavy metals in leachate from fly ash amended soil was substantially greater than in leachates from the other treatments. The results suggest that at heavy loading rates of biosolids, leaching of NO3 − can be an important concern. Leaching of inorganic P can be increased significantly by application of both co-compost and biosolids, but significantly decreased by applying fly ash and N-viro soil. Biosolids, N-viro soil and fly ash applications significantly increased Ca and Mg concentrations in leachates. Copper concentration in leachate was increased by application of biosolids, while Fe concentration in leachates was increased by biosolids, fly ash and co-compost applications. The concentrations of Zn, Mo and Co in leachates were increased by application of fly ash. The concentrations of heavy metals in leachates were very low and unlikely to be harmful, although they were increased significantly by fly ash application.