Publication date: April 2014
Source:Geoderma, Volumes 217–218
Author(s): Wojciech Szymański , Michał Skiba , Artur Błachowski
Fe–Mn nodules are common components occurring in various soils and especially in soils exhibiting imperfect drainage. The formation, distribution, chemical composition, size, and shape of Fe–Mn nodules are the subject of many studies and the research literature contains a lot of information concerning these issues. On the other hand, data regarding the mineral composition of Fe–Mn nodules in the soil environment are limited to only a few studies. The main aim of the present study was to determine the mineral composition of the Fe–Mn nodules found in Albeluvisols in the Carpathian Foothills in Poland using quantitative X-ray diffraction (QXRD), Fourier transform infrared spectroscopy (FTIR) and Mössbauer spectroscopy (MS). The obtained results show that Fe–Mn nodules from Albeluvisols in the Carpathian Foothills in Poland are composed mainly of silicates (quartz, K-feldspars, plagioclases) and phyllosilicates (dioctahedral mica, smectite, chlorite, and kaolinite), which are impregnated with iron and manganese oxides. Iron minerals are represented by goethite and probably lepidocrocite. Both iron minerals are characterized by very small particles and poor crystallinity. Goethite occurring in all of the studied Fe–Mn nodules clearly prevails over lepidocrocite, which exhibits a higher concentration only in nodules from the lower part (fragipan) of the soil profile located on a footslope and showing the strongest stagnic color pattern. Manganite and todorokite represent manganese minerals; however, todorokite was observed only in nodules obtained from illuvial horizons (Btx, Btg) of the studied Albeluvisols. The Fe–Mn nodules obtained from eluvial horizons (Eg) show higher amounts of silicates (quartz, K-feldspars, plagioclases) than the nodules obtained from illuvial horizons. On the other hand, Fe–Mn nodules obtained from illuvial horizons (fragipan and argillic) exhibit higher amounts of phyllosilicates (i.e. clay minerals) in comparison with the eluvial horizon. The differences in the quantitative mineral composition of the Fe–Mn nodules between eluvial and illuvial horizons are related to the translocation of clay minerals from upper soil horizons into the lower part of the soil profiles. This indicates that the nodules from E horizons were formed after translocation of major portion of clay fraction down the soil profile. The similar mineral composition of the Fe–Mn nodules and bulk soil material indicates that the nodules were formed in situ because of cyclic reduction and oxidation of Fe- and Mn-oxides.
Source:Geoderma, Volumes 217–218
Author(s): Wojciech Szymański , Michał Skiba , Artur Błachowski