Identification of Heavy Metals in Crystals of Sand and Silt Fractions of Soils by Scanning Electron Microscopy (SEM EDS/WD-EPMA)

Araina Hulmnn Batista, Vander Freitas Melo, Robert Gilkes, Malcolm Roberts

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Abstract

Studies of heavy metals are concentrate on clay fractions, but coarser fractions of the soil can constitute significant sources of structural forms of heavy metals. The aim of this study was to evaluate the occurrence of heavy metals in the structure of minerals of the sand and silt fractions of soils from three different parent materials (metamorphic rocks and granite) in southern Brazil using SEM/EDS - Scanning Electron Microscopy with Energy Dispersive Spectroscopy and with WD-EPMA - with Wavelength Dispersive-Electron Probe Microanalysis. We sampled soils from two areas naturally rich in heavy metals, with high mineral deposits (galena - PbS) hosted in carbonate rocks and phyllite/mica schist. The main form of Ba in the sand and silt fractions was as barite (BaSO4). The precipitation of Ba and S from the soil solution occurred on the surface of silicate mineral particles. Due to the proximity of ionic radius of Ba-Pb, there was isomorphic substitution of Ba for Pb in the barite structure. The only primary mineral source of Pb in the coarse soil fractions was trioctahedral mica. Several secondary minerals in the silt and sand are sources of structural Pb: plumbogummite, plumboferrite, magnetoplumbite, and cerussite. There was a strong geochemical association of Pb-Fe-Mn. Zinc was also associated with Fe. The SEM/EDS/WD-EPMA techniques are important analyses to complement standard procedures, such as X-ray diffraction and total chemical digestion, in geochemical studies.

Original languageEnglish
Article number0170174
Number of pages16
JournalRevista Brasileira de Ciencia do Solo
Volume42
DOIs
Publication statusPublished - 2018

Cite this

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title = "Identification of Heavy Metals in Crystals of Sand and Silt Fractions of Soils by Scanning Electron Microscopy (SEM EDS/WD-EPMA)",
abstract = "Studies of heavy metals are concentrate on clay fractions, but coarser fractions of the soil can constitute significant sources of structural forms of heavy metals. The aim of this study was to evaluate the occurrence of heavy metals in the structure of minerals of the sand and silt fractions of soils from three different parent materials (metamorphic rocks and granite) in southern Brazil using SEM/EDS - Scanning Electron Microscopy with Energy Dispersive Spectroscopy and with WD-EPMA - with Wavelength Dispersive-Electron Probe Microanalysis. We sampled soils from two areas naturally rich in heavy metals, with high mineral deposits (galena - PbS) hosted in carbonate rocks and phyllite/mica schist. The main form of Ba in the sand and silt fractions was as barite (BaSO4). The precipitation of Ba and S from the soil solution occurred on the surface of silicate mineral particles. Due to the proximity of ionic radius of Ba-Pb, there was isomorphic substitution of Ba for Pb in the barite structure. The only primary mineral source of Pb in the coarse soil fractions was trioctahedral mica. Several secondary minerals in the silt and sand are sources of structural Pb: plumbogummite, plumboferrite, magnetoplumbite, and cerussite. There was a strong geochemical association of Pb-Fe-Mn. Zinc was also associated with Fe. The SEM/EDS/WD-EPMA techniques are important analyses to complement standard procedures, such as X-ray diffraction and total chemical digestion, in geochemical studies.",
keywords = "plumbogummite, barite, isomorphic substitution, polished sample, TRACE-ELEMENTS, MINERALS, SPAIN, LEAD, FORMS, ZINC",
author = "Batista, {Araina Hulmnn} and Melo, {Vander Freitas} and Robert Gilkes and Malcolm Roberts",
year = "2018",
doi = "10.1590/18069657rbcs20170174",
language = "English",
volume = "42",
journal = "Revista Brasileira de Ciencia do Solo",
issn = "0100-0683",
publisher = "SOC BRASILEIRA DE CIENCIA DO SOLO",

}

TY - JOUR

T1 - Identification of Heavy Metals in Crystals of Sand and Silt Fractions of Soils by Scanning Electron Microscopy (SEM EDS/WD-EPMA)

AU - Batista, Araina Hulmnn

AU - Melo, Vander Freitas

AU - Gilkes, Robert

AU - Roberts, Malcolm

PY - 2018

Y1 - 2018

N2 - Studies of heavy metals are concentrate on clay fractions, but coarser fractions of the soil can constitute significant sources of structural forms of heavy metals. The aim of this study was to evaluate the occurrence of heavy metals in the structure of minerals of the sand and silt fractions of soils from three different parent materials (metamorphic rocks and granite) in southern Brazil using SEM/EDS - Scanning Electron Microscopy with Energy Dispersive Spectroscopy and with WD-EPMA - with Wavelength Dispersive-Electron Probe Microanalysis. We sampled soils from two areas naturally rich in heavy metals, with high mineral deposits (galena - PbS) hosted in carbonate rocks and phyllite/mica schist. The main form of Ba in the sand and silt fractions was as barite (BaSO4). The precipitation of Ba and S from the soil solution occurred on the surface of silicate mineral particles. Due to the proximity of ionic radius of Ba-Pb, there was isomorphic substitution of Ba for Pb in the barite structure. The only primary mineral source of Pb in the coarse soil fractions was trioctahedral mica. Several secondary minerals in the silt and sand are sources of structural Pb: plumbogummite, plumboferrite, magnetoplumbite, and cerussite. There was a strong geochemical association of Pb-Fe-Mn. Zinc was also associated with Fe. The SEM/EDS/WD-EPMA techniques are important analyses to complement standard procedures, such as X-ray diffraction and total chemical digestion, in geochemical studies.

AB - Studies of heavy metals are concentrate on clay fractions, but coarser fractions of the soil can constitute significant sources of structural forms of heavy metals. The aim of this study was to evaluate the occurrence of heavy metals in the structure of minerals of the sand and silt fractions of soils from three different parent materials (metamorphic rocks and granite) in southern Brazil using SEM/EDS - Scanning Electron Microscopy with Energy Dispersive Spectroscopy and with WD-EPMA - with Wavelength Dispersive-Electron Probe Microanalysis. We sampled soils from two areas naturally rich in heavy metals, with high mineral deposits (galena - PbS) hosted in carbonate rocks and phyllite/mica schist. The main form of Ba in the sand and silt fractions was as barite (BaSO4). The precipitation of Ba and S from the soil solution occurred on the surface of silicate mineral particles. Due to the proximity of ionic radius of Ba-Pb, there was isomorphic substitution of Ba for Pb in the barite structure. The only primary mineral source of Pb in the coarse soil fractions was trioctahedral mica. Several secondary minerals in the silt and sand are sources of structural Pb: plumbogummite, plumboferrite, magnetoplumbite, and cerussite. There was a strong geochemical association of Pb-Fe-Mn. Zinc was also associated with Fe. The SEM/EDS/WD-EPMA techniques are important analyses to complement standard procedures, such as X-ray diffraction and total chemical digestion, in geochemical studies.

KW - plumbogummite

KW - barite

KW - isomorphic substitution

KW - polished sample

KW - TRACE-ELEMENTS

KW - MINERALS

KW - SPAIN

KW - LEAD

KW - FORMS

KW - ZINC

U2 - 10.1590/18069657rbcs20170174

DO - 10.1590/18069657rbcs20170174

M3 - Article

VL - 42

JO - Revista Brasileira de Ciencia do Solo

JF - Revista Brasileira de Ciencia do Solo

SN - 0100-0683

M1 - 0170174

ER -