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Data on strontium accumulation acquired by studying the floodplain soils of the Kuda River, Irkutsk Region, show that the bulk accumulation of this element and the accumulation of its water-soluble species are controlled by evaporative concentration. Floodplain areas maximally enriched in water-soluble strontium are defined. These areas are the most potentially hazardous if involved in agricultural activities because Sr can be transferred there into the surface- and soil–groundwaters in concentrations several times higher than the maximum permissible concentrations of this element in water bodies.

The morphological properties of floodplains and their morphological classification are shown from the generalization of long-term studies. A detailed description of alluvial processes is given, and stages of alluvial soil formation are characterized. Zonal-geographic, hydro-geomorphologic, evolutionary, and geomorphologic-genetic regularities in soil geography are found. The properties of alluvial soils under sharply contrasting climatic conditions, e.g., humid and arid, are considered. The high biogenic ability of soils and intensity of the soil-forming process in floodplains are proved. Data characterizing the structure and properties of floodplain soils in particular river valleys and the main micromorphological diagnostic features of alluvial soils are given.

The species composition and structure of collembolan communities in floodplain soils were analyzed; a total of 65 species were found. The highest springtail species diversity was revealed in soils of birch-aspen forests. Collembolan communities in meadow soils were the most similar to those in the aspen forests of the second and third age classes. Prevalence of edaphic and hemiedaphic species is characteristic of soils of birch-aspen forests.

Specific features of the soil cover in the lower reaches of the Ob River are analyzed. The physicochemical properties and composition of the floodplain soils in different parts of the valley and on different floodplain elements are given. A comparative geographical analysis of the accumulation of macro-and microelements in the floodplain soils as a result of alluviation processes in the middle and lower reaches of the Ob River is suggested. The evolution of the floodplain soils and the results of the development of stratified humus horizons, changes in the hydrological regime, and cessation of floods are discussed.

Small concentrations of mercury are determined by the example of the quantitative recovery of a toxicant from snow water in a segregating system with no organic solvent (water-antipyrine-sulfosalicic acid). The organic component of the system in situ forming as a result of acid-base interactions was used in microliter amounts to modify a graphite indicator electrode and register an analytical signal of mercury. The reliability of the results of voltammetric determination was checked by the independent cold vapor method. Organic components obtained by segregation were used to extract mercury from the conservative ecosystem component, solid snow particles, snow water preconcentrated with a membrane filter, river suspensions from surface water and floodplain soils, and also fish samples. The characteristic features of mercury extraction with a mixture if mineral acids and the liquid organic component of a segregating system with no organic solvent are discussed.

Gleyzation-mediated leaching of radiostrontium from floodplain soils of the Krasnoyarsk Mining and Chemical Combine (MCC) activity zone [Atamanovskii Island (front part), Oseredysh Island (front part), and Berezovyi Island (rear part)] is studied with model systems. Leaching of radiostrontium from waterlogged soils is analyzed in terms of the model of anaerobic biosolubilization of gel films. The leaching of radiostrontium is found to correlate with that of iron, confirming the cosolubilization model. Addition of glucose (0.5%) as a stimulant for growth of iron-reducing microorganisms increases the dynamic coefficient of radiostrontium leaching, particularly in soils with lower organic matter content. The model experiments showed that the radiostrontium leaching rate from floodplain soil is higher by 2–3 orders of magnitude than that of radio-cesium, suggesting the possibility of escape of radiostrontium from the floodplain of the Yenisei River with the intrasoil runoff. This conclusion is supported by the experimental data on the 90Sr/137Cs ratio in the floodplain of the Yenisei River downstream of MCC (0.01–0.1).

The distribution of earthworms in 18 types of tundra, middle-taiga, alas, and floodplain soils of Yakutia has been studied. The species Eisenia nordenskioldi is typical of Yakutian soils. The area, population density, and seasonal dynamics of earthworms in permafrost-affected soils have been determined. It is shown that earthworms are absent in excessively moist peat-muck permafrost-affected soils, excessively dry soddy soils of alases (thermokarst depressions), and soddy alluvial soils under steppe communities. The best living conditions for earthworms are associated with meadow floodplain, meadow alas, and mucky calcareous soils.