Abstract
Fly ash (FA) and sewage sludge (SS) are usually used in agriculture as soil amendments, creating a risk of heavy-metal pollution. However, simultaneous application of these wastes may reduce the mobility of heavy metals in soils. This study investigates the influence of fly ash application on copper (Cu) and zinc (Zn) sorption by an acidic soil amended with SS. An adsorption experiment of Cu and Zn was carried out in a Typic Haploxeralf from Greece amended with various doses of fly ash [0.25% (FA1) and 0.5% (FA2)]; sewage sludge [0.28% (SS1) and 0.56% (SS2)]; and fly ash plus sewage sludge [(FA1 + SS1) and (FA1 + SS2)] and incubated for 1 month under field capacity conditions. Furthermore, a sample without any amendment was incubated as a control for comparison. The Freundlich equation was used to describe adsorption of Cu and Zn. Distribution coefficient (K d), which represents sorption affinity of metals for the solid phase, was obtained for all the treatments applied. Data showed that Cu K d values were obviously higher than Zn values in all the treatments applied. Distribution coefficients values for FA2 treatment were about 10 and 7 times greater than the control for Zn and Cu, respectively. Simultaneous application of FA and SS caused K d increases of 4.2 and 3.5 times more than treatment that received only SS for Zn and Cu, respectively. Distribution coefficient values of Zn and Cu were significantly correlated with soil pH. These results confirm that alkaline FA can be used as an effective amendment for remediation of Cu- and Zn-polluted acidic and SS-amended soils.