Heavy metals release from ash pond to soil water environment: A simulated technique

Abstract

A column experiment was set up to provide an environment in which certain heavy metals leach from impounded ash, then enter ground water by percolation through soils, a condition that is prevailing in an ash pond. Percolation of 1 L and 2 L ash effluent per d. up to a period of 40 d., through 60 cm depth of the alluvial soil resulted in an increased pH, electrical conductivity (E.C.), and levels of heavy metals like Cr, Mn, Ni, and Pb in leachates as well as in layers of soils. The heavy metals content in leachates was found increased with increased percolation of ash effluents. The pH of the soil was found to increase from 7.4 to 8.1. The pH of the soil was regulating the available and total metals content. It had lower available and higher total metals concentrations in alkaline soil at the top while higher available and lower total metals concentrations in acidic soil at the middle of the treated soil columns. The sorption and retention of heavy metals in the soil layers were also found to be dependent on the following in order of importance, based on soil texture: level of organic matter, cation exchange capacity, sorption/precipitation, and mobility of these metals in soil.