MOBILITY AND DISTRIBUTION OF LEAD IN SOILS TREATED WITH MUNICIPAL SOLID WASTE ASH

Abstract

Lead (Pb) is an inorganic conservative pollutant poses a risk to soils and water resources. Quantifying the potential hazard impacts of Pb in soils needs further circumstances about its mobility and retention as well. The objective of this study was to evaluate the effects of municipal solid waste ash (MSWA) on mobility and distribution of Pb in two types of soil textures. The extent of Pb mobilization in soils amended with different application rates of MSWA has been quantified by soil columns experiment under steady state conditions. Transport of Pb was studied in soil columns by applying Pb solution of 150 mg/L at the rate of 0.09 cm/min for loamy sand soil and 0.035 cm/min for sandy loam soil. The mathematical model- HYDRUS-2D was used to describe this transport. The results indicated that Pb concentrations were extremely low in the leaching solutions collected from soil columns over time regardless of the application rates of MSWA. Application of MSWA increased the recovery of Pb in both soils achieving superiority in loamy sand soil. The Pb distributed in the soil columns ranged between soil leaching solutions and sorbed phase, of which the greater portion was in the sorbed phase. Lead move slowly through soils columns and the distance of movement was about 5 cm to the soil surface and then the concentrations decreased down the soil columns and later disappeared beyond a depth of to 7 cm. Mass balance calculations of Pb according to the HYDRUS-2D mathematical model resulted in values that were similar to those of the experimental data (error ≤ 5%). A soil quality indicator is considered as a key element of sustainable agriculture and hence soil quality plays an important role in deciding the MSWA methods.