Chemical-Mineralogical Characterization of Magnetic Materials from Magnetic Soils of the Southern Espinhaço Mountain Chain and of the Upper Jequitinhonha Valley, State of Minas Gerais, Brazil

Abstract

In the Southern Espinhaço Mountain Chain and in the Upper JequitinhonhaValley, magnetic soils, in different pedogenetic stages, are found to be forming over intrusions of basic lithology. The essential chemical and mineralogical properties of samples from magnetic soil profiles from those two physiographic environments in the state of Minas Gerais, Brazil, are reported. Three of the pedons (Rhodic Kandiustox -RKox, Rhodic Haplustox -RHox, and Typic Argiustoll -TAoll) were identified as being indeed developed over basic rocks; the fourth pedon (Typic Haplustox -THox) is currently forming on an acidic rock. Particle size and routine chemical analyses were performed on samples from all horizons of the four selected soil profiles. For a deeper insight into the dominant mineralogy of each diagnostic soil horizon, the elemental contents, expressed in terms of the corresponding metal cation oxides, namely Fe 2 O 3 , Al 2 O 3 , and MnO 2 , were obtained from digesting the whole soil samples with sulfuric acid. A similar chemical analytical procedure was performed for the residual solid extracts obtained from attacking the whole soil materials with mixtures of (i) dithionite -citrate -bicarbonate and (ii) oxalate -oxalic acid. The soil samples were also analyzed by Mössbauer spectroscopy at room temperature (~298 °K) in an attempt to better identify the main magnetic iron oxides. Maghemite (δFe 2 O 3 ) was found in all samples and magnetite (Fe 3 O 4 ) was identified only for the sample from the Typic Argiustoll. The pedogenetic loss of silica and consequent accumulation of iron and aluminum oxides along the profile are found to be somehow correlated to the weathering sequence in the soils forming on basic rocks: TAoll < RKox < RHox.

Soil mesofauna in consolidated land use systems: how management affects soil and litter invertebrates

“…In the forest soils, where no herbicide and no fertilization are applied, Al levels were higher compared to the other agricultural systems (Table 2), since Al is one of the most persistent elements in highly weathered tropical soils without fertilization (Silva et al, 2017). Due to its high potential acidity, NF also presented a higher potential CEC than the other land use systems evaluated (Table 2).…”

Mineralogical Evolution of Magnetic Rhodic Oxisols under Different Lithological Influences in Brazil

“…In contrast, the Mössbauer spectra indicated that Mh is the only ferrimagnetic Fe oxide in the sand fraction of most soils, with the exception of LV 7 and LV 11 , where highly oxidized Mt traces, {Fe}/[Fe] lower than 1.88 (Vandenberghe et al, 2000), were identified. Silva et al (2017) also observed only Mh in Oxisols with spontaneous magnetism investigated by the Mössbauer spectroscopy.…”

“…Rhodic Oxisols exhibit strong magnetic attraction due to high contents of ferrimagnetic Fe oxides (maghemite and magnetite) (Costa et al, 1999(Costa et al, , 2014Camêlo et al, 2018;Poggere et al, 2018). These minerals have often been used in studies on pedogenesis (Silva et al, 2017;Camêlo et al, 2018) for stratification of environments (Ramos et al, 2017) and soil fertility (Costa et al, 2018) in Brazil and elsewhere in the world.…”

“…Therefore, several authors have reported on magnetite predominance in the coarse fractions (sand and silt) and maghemite in the clay fraction (Costa et al, 1999;Carvalho Filho et al, 2015;Camêlo et al, 2018;Poggere et al, 2018) of Fe-rich Rhodic Oxisols in Brazil. However, it is known that both minerals can display distinct soil size fractions or occur in all of them (Causevic et al, 2004;Maxbauer et al, 2016;Silva et al, 2017;Costa et al, 2018).…”

Individual and Competitive Adsorption of Copper, Zinc and Lead in Soils with Contrasting Texture

“…The low silt/clay ratio in Oxisols is related to its advanced stage of weathering [12]. Silva et al [13] also found low ratio when studied soils originated from metabasalt in another region of Brazil.…”