Retention of Metals Leached From Municipal Solid Waste Incineration (MSWI) Bottom Ashes in Soils

Abstract

Utilization of bottom ash in road construction may lead to a release of contaminants that can affect the soil of the swales constructed along these roads. Column tests were performed to evaluate the retention behavior of Cu, Cr, Zn, and Pb, originating from municipal solid waste incineration (MSWI) bottom ash leachate, in two substrates: peat and mould (a cultural soil). A chemical sequential extraction method was used to predict the risk associated with the release of the retained elements with modifications of environmental conditions. Apart from the dissolution of organic matter (OM), ash leachate properties hindered the metal transport from peat. Mould was efficient only in removing Zn, making it a less favorable substrate for the leachate control along the roads. Readily soluble forms made up a minor fraction of the retained metals in peat, reducing the risk of metal release due to ion exchange and pH drop. Changes in redox potential might be the main cause of Zn desorption from peat as the Fe-Mn oxides were the main scavengers for this metal. Oxidation of OM would be the primary reason of Cu and Cr release, while for Pb both fractions (Fe-Mn oxides and OM) might equally contribute to the metal discharge.