Calcium carbonate accumulations in Technosols of Moscow city

Prokof’eva, T.; Shishkov, V.; Kiriushin, A.

Авторы: Prokof’eva T., Shishkov V., Kiriushin A.
Журнал: Journal of Soils and Sediments
Том: 21
Номер: 5
Год издания: 2020
Издательство: Ecomed Verlagsgesellschaft AG & Co.
Местоположение издательства: Germany
Первая страница: 2049
Последняя страница: 2058
DOI: 10.1007/s11368-020-02696-y
Аннотация: Purpose: Complex phenomena of the precipitation and accumulation of calcium carbonate in urban soils and sediments have been studied. They are linked to the interactions between the lithosphere, the biosphere, and the atmosphere. Calcium and its compounds are among the main elements determining soil’s morphological, physical, and chemical characteristics. This study was aimed at summarizing information about calcium carbonate concentrations in soils and finding evidence for the formation of carbonate micronodules by pedogenetic processes in Urbic Technosols under automorphic conditions. Materials and methods: Moscow is located within the southern taiga belt, with a humid temperate climate and a percolative water regime. The city’s technogenic deposits contain significant amounts of carbonates due to inclusions of construction waste and additions of airborne dust. Contemporary humus-accumulative horizons of Urbic Technosols were found to contain carbonate accumulations (rounded or isomorphic nodules). Samples from such horizons were studied using a polarizing microscope (analysis of thin sections) and a scanning electron microscope with an energy-dispersive X-ray analyzer (element mapping to detect carbonate accumulations). Laboratory analyses of main chemical and physical soil properties were performed. Results and discussion: The analyzed samples contained both primary (i.e., inherited from parent materials) and secondary (i.e., newly formed in soils) calcium carbonates in various forms. Inclusions of solidified mortar (carbonate building solutions) contained dolomite. Although the studied carbonates underwent recrystallization processes, they remained in soils for a long time. Fibrous Mg silicate films deposited at the surface of recrystallization areas were observed. The formation of carbonate micronodules at depths of 15–40 cm in slightly and moderately calcareous humus horizons was investigated. Newly formed calcite was distinguished by a homogeneous composition, a microsparitic size of crystals, and a compact packing within the groundmass. Newly formed calcite was observed within microzones that were free from carbonate inclusions with dissolution features. Conclusions: The dissolution of primary carbonates in soils under humid climate conditions triggers pedogenetic processes of the carbonate heritage redistribution and the mineral matrix transformation. Recrystallized carbonates are the main forms of secondary carbonate accumulations in automorphic Technosols. The presence of compact carbonate nodules composed of microsparitic calcite within the bulk of silicate material may be indicative of carbonate neoformation as a result of interactions between the dissolved CO2 from root respiration and the soil absorbing complex saturated by Ca from soil solution. This is confirmed by a number of studies on the carbonate isotopic composition in urban soils. Keyword:s Soil morphology . SUITMAs . Calcite micronodules . Electron microscopy . Urbic Technosols
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Calcium carbonate accumulations in Technosols of Moscow cityстатья

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