L.A. Fattakhova*, A.A. Shinkarev**, L.R. Kosareva***
Kazan Federal University, Kazan, 420008 Russia
E-mail: *L.a.fattakhova@yandex.com, **Ashinkar@mail.ru, ***Lina.kosareva@mail.ru
Abstract
The magnetic properties of virgin forest-steppe soils developed on the originally vertically uniform unconsolidated parent material have been investigated. The profile samples of virgin dark-grey forest light-clayey soil derived from a siltstone of the Kazan layer of the Upper Permian and virgin leached medium-thick fertile light-clayey chernozem derived from a Quaternary heavy deluvial loam have been considered. Both soils are characterized by the accumulative type of magnetic susceptibility and F-factor values distribution patterns with depth. In the humus part of the soil profile, magnetics are present predominantly in the < 2.5 ?m fraction. The coercivity spectra allowed to determine the contribution of dia-/paramagnetic and ferromagnetic components to magnetic susceptibility. It has been found that magnetic susceptibility enhancement in the organogenic horizons of virgin forest-steppe soils occurs due to the contribution of ferromagnetic components. The results indicate a strong positive linear correlation between the magnetic susceptibility and oxalate-extractable Fe, as well as between the magnetic susceptibility and Schwertmann's criterion values. Using the method of thermomagnetic analysis of the < 2.5 ?m fraction, it has been found that the magnetic susceptibility enhancement in the profiles of forest-steppe soils took place due to the formation of maghemite-magnetite associations. The predominantly ferromagnetic fraction consists of small single-domain grains.
Keywords: virgin dark-grey forest soil, virgin leached chernozem, magnetic susceptibility, ferromagnetic component, non-silicate compounds of Fe, profile differentiation, thermomagnetic analysis
Acknowledgments. This study was funded by the subsidy allocated to Kazan Federal University for the state assignment in the sphere of scientific activities.
Figure Captions
Fig. 1. The X-ray diffractograms of powder preparations of the parent rock materials of leached chernozem (a) and dark-grey forest soil (b). Minerals: I/S – illite-smectite, M – illite, Am – amphiboles, Cl – chlorite, K – kaolinite, Ab – albite, Mc – microcline (orthoclase), Ca – calcite, Q – quartz, Do – dolomite.
Fig. 2. Profile distributions of the magnetic parameters in dark-grey forest soil (a) and leached chernozem (b): 1 – original samples; 2 – samples after the removal of organic matter; 3 – preparations of the < 2.5 ?m fraction isolated after the removal of carbonates and organic matter.
Fig. 3. Dependence between the general magnetic susceptibility and its ferromagnetic component in the profile samples of dark-grey forest soil (?) and leached chernozem (?).
Fig. 4. Dependence between the magnetic susceptibility of the profile samples of dark-grey forest soil (a) and leached chernozem (b) and the content of non-silicate crystalized (?) and “amorphous” (?) compounds of Fe.
Fig. 5. Dependence between the magnetic susceptibility and the proportion of “amorphous” and weakly crystalized forms among all non-silicate compounds of Fe in the profile samples of dark-grey forest soil (?) and leached chernozem (?).
Fig. 6. TMA curves of the samples from the upper part and the bottom of the profile of virgin dark-grey forest soil (а) and virgin leached chernozem (b).
Fig. 7. TMA curves of the < 2.5 ?m fraction of the samples from the upper part and bottom of the profile of virgin dark-grey forest soil (а) and virgin leached chernozem (b).
Fig. 8. Characteristics of magnetic grain sizes in the bulk samples from the upper part of the profile of dark-grey forest soil (?) and leached chernozem (?) based on the hysteresis parameters of forest-steppe soils on Day's theoretical diagram: SD – single-domain; MD – multi-domain; PSD – pseudo-single-domain; SP – super-paramagnetic domains of the diagram.
References
For citation: Fattakhova L.A., Shinkarev A.A., Kosareva L.R. Magnetic soils profiles in the Volga-Kama forest-steppe region. Uchenye Zapiski Kazanskogo Universiteta. Seriya Estestvennye Nauki, 2016, vol. 158, no. 3, pp. 391–403. (In Russian)
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