Abstract
PurposeFerrolysis is a soil-forming process, which involves destruction of clay minerals due to cyclic reduction and oxidation in acidic and periodically wet soils. The main objectives of this study were as follows: (1) to determine the influence of redox processes on clay mineral transformation in Retisols (Albeluvisols) in the Carpathian Foothills in Poland and (2) to verify the occurrence of ferrolysis in Retisols showing various degrees of bleaching.Materials and methodsTwelve representative soil profiles were selected for analysis. All were formed entirely from loess except for two profiles, in which the lowermost horizons (2C) had developed from weathered flysch rocks residuum. Soil mineral analysis was done using x-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and Mössbauer spectroscopy (MS).Results and discussionThe obtained results indicate that the qualitative and quantitative mineral compositions of the clay fraction in the E and Eg horizons obtained from Retisols in the Carpathian Foothills exhibiting marked differences in bleaching (strong, moderate, weak, and lack of bleaching) caused by periodic stagnation of water above a slowly permeable fragipan and cyclic redox processes are the same. The E and Eg horizons are characterized by the presence of 2:1 clay minerals with likely organic interlayer fillings, dioctahedral mica, kaolinite, and chlorite.ConclusionsThe results indicate that (1) redox processes occurring in the soils do not affect clay mineral transformation in Retisols of the Carpathian Foothills in Poland and (2) ferrolysis is not the main soil-forming process operating in these soils. This is most likely because iron-bearing minerals are not abundant in the Retisols and/or undergo eluviation to the lower part of the soil profiles. The lower content of the clay fraction in the E and Eg horizons versus that in the lower soil horizons of the Retisols is related to clay illuviation (lessivage), and not to clay decomposition due to ferrolysis.
Highlights
Soils with a contrasting texture are very common around the world (Kemp and McIntosh 1989; Phillips 2001, 2004, 2007; Świtoniak 2008, 2014; Świtoniak et al 2016)
The obtained results indicate that the qualitative and quantitative mineral compositions of the clay fraction in the E and Eg horizons obtained from Retisols in the Carpathian Foothills exhibiting marked differences in bleaching caused by periodic stagnation of water above a slowly permeable fragipan and cyclic redox processes are the same
The E and Eg horizons are characterized by the presence of 2:1 clay minerals with likely organic interlayer fillings, dioctahedral mica, kaolinite, and chlorite
Summary
Soils with a contrasting texture are very common around the world (Kemp and McIntosh 1989; Phillips 2001, 2004, 2007; Świtoniak 2008, 2014; Świtoniak et al 2016). Ferrolysis is a soil-forming process, which was first proposed by Brinkman (1970) It involves destruction of clay minerals due to cyclic reduction and oxidation in acidic and periodically wet soils (Brinkman 1970; Barbiero et al 2010). Ferrolysis involves biochemical reduction of Fe3+ taking place during wet seasons and leading to mobilization of Fe and substitution of exchangeable cations within clay minerals with Fe2+. The transformation of 2:1 clay minerals due to the cyclic reduction and oxidation and formation of the clays with interlayer fillings is responsible for lowering their cation exchange capacity, mineral solubility, and swelling ability (Rich 1968; Brinkman 1979; Nakao et al 2009; Szymański et al 2014)
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