Physical distribution of Ni, Pb and Zn in reclaimed mine soils observed by FE-SEM with an EDS detector
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The aim of this study was to physically demonstrate the associations between Ni, Pb and Zn and the different soil components. To achieve this, several soil samples were observed by field emission-scanning electron microscope (FE-SEM) equipped with an energy dispersive spectrometer (EDS) detector. The samples came from mine sites vegetated and/or amended with wastes (sewage sludges and paper mill residues). The concentrations of metals in the different soil fractions were quantified by a chemical sequential extraction in a previous study. The sorption capacity of the soils was evaluated with sorption experiments using the batch method. We corroborated the results obtained by the sequential extraction of metals as well as the sorption experiments with the observations from the FE-SEM with the EDS. We physically observed the associations between Ni, Pb and Zn and oxides, organic matter and clays. We also observed PbCaCO3 crystals in one of the soils, presumably formed during the sorption experiment. As it is not possible to know with complete certainty how Pb was retained by calcium in this soil by only using chemical methods, the use of microscopic techniques is crucial to ascertain how metals are associated with the different soil fractions.
KeywordsMetals Mine soil FE-SEM Waste amendments
This study was supported by the Spanish Ministry of Education and Science through project number CGL2009-07843. The authors are especially grateful to Eugenio Solla for his valuable help with the FE-SEM and EDS analyses. We also thank the anonymous reviewers for their comments which triggered some new thoughts and thus helped to improve the quality of this paper.
Compliance with Ethical Standards
The present study was supported by the Spanish Ministry of Education and Science through project number CGL2009-07843; it does not have conflicts of interest and it did not involve human or animal participants.
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