Carbonates in Soils of Sugar Industry Infiltration Fields in the Central Chernozem Region

The forms, composition, and transformation of carbonates in the course of soil formation in technogenic landscapes—sewage infiltration fields of the sugar industry in the Chernozem region, were studied using a range of modern instrumental methods. The soils of sludge drying checks (Calcaric Gleysols, Histic Gleysols, Eutric Cambisols) inherit the original Chernozem residue containing pedogenic carbonates; they are formed under the periodic impact of carbonate-containing waste from the sugar industry such as wastewater, defecation sludge, and conveyor-washing sludge. The carbonate-containing matter entering soils from the technogenic sources consists mainly of calcite; the composition and the share of admixtures in the defecation sludge generally correspond to their content in the original limestone. Transformation of anthropogenic carbonates under the pedogenesis results in the formation of abundant and diverse carbonate pedofeatures. The latter are represented by impregnations, scattered sparite crystals, mottles, microsegregations, pseudomycelium, and calcified plant residues. Carbonates in soils of operating untreated checks are represented not only by carbonate pedofeatures, but also by calcareous interlayers of precipitated defecation sludge and wastewater sludge. Raman spectra of carbonates point to the presence of two crystalline polymorphic modifications of CaCO3, calcite and aragonite, in the soils of infiltration fields. A tendency for aragonite transformation into calcite is observed after the infiltration checks are abandoned and soils continue to develop under natural hydrothermal regime.