Mobility of potentially harmful metals in latosols impacted by the municipal solid waste deposit of Londrina, Brazil

Raquel Souza Teixeira,Regina Davison Dias,Philippe Cambier,Anne Jaulin-Soubelet,José Paulo Peccinini Pinese

doi:10.1016/j.apgeochem.2009.09.022

Abstract

The contamination of soils by metals issuing from municipal solid waste (MSW) disposal in tropical environments has hardly been studied with regard to the particular problems associated with them, i.e., generally a high permeability of soils despite the abundance of clay, and the role of reactive Fe compounds. From a previous geotechnical and chemical survey, three latosol profiles differently affected by MSW leachates in the region of Londrina (Paraná, Brazil) were selected. The aims were to evaluate the extent of their contamination, to better understand the fate of potentially harmful metals in tropical soils and rank the determining factors. Samples between 0.5 and 7 m depth were analyzed for their physical, mineralogical and chemical properties, and their micro-morphology was described by optical and transmission electron microscopy. Two steps of a sequential extraction procedure helped to assess the mobility of elements and to better discriminate between metals originating from pedogenesis and issued from MSW. These combined approaches showed that exposed soil profiles have been impacted at various depths, down to 7 m, through increased metal content, especially enhanced mobility of Zn, Co, Mn, Cu and Fe, and through increased salinity and organic matter. The mobility of potentially harmful metals should decrease with pH, which significantly increased in some impacted horizons, but other factors can reverse this trend.

Highlights

The diagnosis of soil contamination by potentially harmful metals has been the subject of public interest since the 1970s and of countless studies reported by many researchers, among them: Yong et al (1996), Alloway and Ayres (1997), Sígolo (1998) and Jucá et al (1999)
municipal solid waste (MSW) leachates caused by the degradation of residues since their deposition are essential for environmental control because they are usually close to areas with agricultural activities and human settlements (Heitzmann, 1999; Mwiganga and Kansiime, 2005; Baba et al, 2004)
Without dispersing agent, all soil samples would be classified as sandy silt, except for P11-0.5 and P11-2 which appeared as clay silt

Summary

Introduction

The diagnosis of soil contamination by potentially harmful metals has been the subject of public interest since the 1970s and of countless studies reported by many researchers, among them: Yong et al (1996), Alloway and Ayres (1997), Sígolo (1998) and Jucá et al (1999). This is due to the environmental and health problems caused by high metal contents in soils which can affect microorganisms, plants, animals and human beings through contamination of water and crops. Among the most common contaminants are organic matter and metals like Cd, Cr, Cu, Mn, Pb, Hg, Zn and Fe (Barazani et al, 2004; Roy et al, 2004)

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Discussion

Conclusion