Background:The study of clay fractions is usually focused on water-dispersible clay (WDC), which is a good indicator of many soil processes involving water (water erosion, transfer and removal of nutrients and contaminants). Aggregated clay (AC) that remains after WDC extraction is also important, as it controls the formation of aggregates and their mechanical and water resistance. The aim of this study was a gradual extraction of WDC and AC fractions from periodically overmoistening meadow podbel (mollic planosol) and the study of the content and composition of humic substances and clay minerals in these fractions as well as their effect on the hydrosorption capacity.
Results:The complete extraction of clay fractions showed that AC prevails over WDC along the entire profile and most evidently in the Ag horizon. Most of the organic matter is concentrated in AC. X-ray diffractometry and SEM analysis revealed a similar set of minerals in both fractions, but in different proportions. In the Ag and Elcg horizons, WDC is enriched with clastic components (fine-dispersed quartz, feldspars, amphiboles) and clay minerals with rigid structures (illite, kaolinite, chlorite), compared to AC. In the Btg1 horizon smectite prevails in both fractions. The specific surface, which characterizes the hydrosorption capacity of clays, of WDC is 28-95 m 2 /g less than that of AC. Maximal difference in specific surface of clays is found in the horizon Elcg, where AC has the highest content of free iron.
Conclusions:The present study allowed defining the heterogeneity of the total clay in the periodically overmoistened meadow soil, which is manifested in differences in composition and properties of WDC and AC fractions. AC largely determines hydrosorption properties of soil due to a high content of organic matter and the predominance of swelling minerals in its composition, compared with WDC. The obtained data highlight the importance of studying clay fractions WDC and AC for the characteristics of differentiation and aggregation of the clay in soils.
The created soil map of Birobidzhan city (scale 1:25 000) reflects the diversity of soils and nonsoil formationsinthecity.Itpresentsfour large ecological soil groups: natural undisturbed, natural disturbed, anthropogenic soils and surface technogenic formations. A schematic map of soil-ecological zoning reflects the summarized state of ecological functions of urban soils, which makes it valuable for the analysis of the overall ecological situation in Birobidzhan. Zonesofsoilswithfullypreservedecologicalfunctions, partiallypreserved functions, completely lost ecological functions and with risk of potentially formation of local geochemical anomalies were shown.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.