卷 49, 编号 6 (2016)

The method of chemodestructive fractionation is suggested to assess the composition of soil organic matter. This method is based on determination of the resilience of soil organic matter components and/or different parts of organic compounds to the impact of oxidizing agents. For this purpose, a series of solutions with similar concentration of the oxidant (K₂Cr₂O₇), but with linearly increasing oxidative capacity was prepared. Chemodestructive fractionation showed that the portion of easily oxidizable (labile) organic matter in humus horizons of different soil types depends on the conditions of soil formation. It was maximal in hydromorphic soils of the taiga zone and minimal in automorphic soils of the dry steppe zone. The portion of easily oxidizable organic matter in arable soils increased with an increase in the rate of organic fertilizers application. The long-lasting agricultural use of soils and burying of the humus horizons within the upper one-meter layer resulted in the decreasing content of easily oxidizable organic matter. It was found that the portion of easily oxidizable organic matter decreases by the mid-summer or fall in comparison with the spring or early summer period.

The behavior of some chemical elements was studied in soils and their liquid phase. Two reference soil profiles on glaciolacustrine clays (soddy-eluvial-metamorphic soil) and sands (soddy podzol) were investigated on the Russian Plain. A colloidal fraction (particles <1 μm) was isolated with deionized hot water from a soil sample of 30 g at the soil: water ratio of 1: 10. The suspension was mixed for 6 h, settled for 24 h, and filtrated using a membrane filter (<1 μm). The soil sample and its water-soluble fraction (WSF) were analyzed by mass spectrometry with inductively coupled plasma. The chemical characteristics of the extracted liquid phase of the soil reflect its water-soluble component properties. The comparison of the data obtained with the results of the analysis for the whole soil allows assessment of a share of easily mobile and difficultly mobile forms of chemical compounds. This is the necessary basis for the development of a model describing the transport of metals in soil.

Monitoring of soil dispersivity and humus state has been performed in the stationary profile of ordinary chernozem in the Botanic Garden of the Southern Federal University in 2009–2014. The contents of physical clay and sand are almost stable in time, which indicates a quasi-static (climax) equilibrium in the soil. Another (reversible dynamic) process occurs simultaneously: seasonal and annual variation in the mass fractions of clay and silt in physical clay. Variations of humus content in the whole soil and in its physical clay are also observed on the background of seasonal changes in precipitation and temperature. A procedure has been developed for the analysis of the polydisperse soil system with consideration for the quasi-static and dynamic equilibriums. A two-vector coordinate system has been introduced, which consists of scales for changes in the contents of physical clay and physical sand in 100 g of soil and changes in the fractions of clay and silt in 100 g of physical clay. Co-measurements of two dispersivity series of soil samples—actual dynamic and calculated under quasi-static equilibrium (ideal)—have been performed. Dynamic equilibrium coefficients, which cumulatively reflect the varying proportions of physical clay and physical sand in the soil and the mass fractions of clay and silt in physical clay, have been calculated.

The article provides an overview of studies about the preferential flow phenomenon. This phenomenon is one of the types of the transportation of water solution through the soil profile by preferential channels (pathways) with a relatively high speed and with a slight change in the chemical composition of the solution. Interest in this phenomenon has risen sharply in the last two decades due to the observed fast transportation of contaminants from soil surface into groundwater level. On the basis of the literature data, the authors give the definition of this phenomenon, consider its types, degree, features, mechanisms, methods and models and research perspectives, in particular the interaction between preferential flow and soil matrix flow. The article considers the aspects of the movement of soil water carrying heavy metals and pesticides; hence, it concerns the protection of environment and people’s health. It provides the thorough review of the studies on the preferential flow, and describes the research directions and their development.

The goal of this study was to determine the relationships between the structure of the soil microbiome and the agroecological state of soils by the example of natural undisturbed (steppe areas) and anthropogenically disturbed (pastures, croplands, fallows) areas in the territory of northwestern Kazakhstan. The highest abundance of proteobacteria was found in the anthropogenically disturbed of fallows and in undisturbed soils; in other cases, actinobacteria and representatives of the Firmicutes phylum predominated. Different kinds of anthropogenic impacts resulted in the decrease in the portions of bacteria from the Acidobacteria, Gemmatimonadetes, and Firmicutes phyla. In the disturbed soils, the portions of bacteria from the Erysipelothrix, Mycobacterium, Methylibium, Skermanella, Ralstonia, Lactococcus, Bdellovibrio, Candidatus nitrososphaera, Catellatospora, Cellulomonas, Stenotrophomonas, and Steroidobacter genera increased. Bacteria of the Erysipelothrix and Methylibium genera occurred only in the undisturbed soils. The anthropogenically disturbed and undisturbed soils differed significantly in the taxonomic structure of their microbiomes forming two separate clusters, which confirms the efficiency of using the data on the structure of soil microbiomes when assessing the agroecological status of soils.

The area of cultivated lands in western and eastern Georgia comprises 28–40 and 29–33% of the total catchment areas, respectively. Eroded arable soils in Georgia occupy 205700 ha, i.e. 30.5% of the total plowland area, including 110500 ha (16.4%) of slightly eroded soils, 74400 ha (11%) of moderately eroded soils, and 20800 ha (3.1%) of strongly eroded soils. The maximum denudation rate in catchments of western Georgia reaches 1.0 mm/yr. The minimum denudation (0.01 mm/yr.) is typical of river catchments in southern Georgia. The mean annual soil loss from plowed fields in western Georgia reaches 17.4 t/ha and exceeds the soil loss tolerance by nearly four times. In eastern Georgia, it is equal to 10.46 t/ha and exceeds the soil loss tolerance by 2.5 times. In southern Georgia, the mean annual soil loss from plowed fields is as low as 3.08 t per ha, i.e., much lower than the soil loss tolerance.

Soils and waters are affected by oil spills in the course of oil production and hydrocarbon leakages because of the corrosion of underground reservoirs, as well as the filtration of hydrocarbons from the tailing ponds formed during the extraction of oil from oil sands. The conventional technology for the withdrawal of contaminated water and its purification on the surface is low-efficient and expensive. New approaches are proposed for the in situ purification of soils and groundwater. To accelerate the oxidation, active substances atypical for the supergenesis zone are used: peroxides of metals and hydrogen. The efficiency of hydrogen peroxide significantly increases when the oxidation is catalyzed by Fe²⁺ or Fe³⁺ (Fenton reaction). The effects of Fe(III), sulfates, and carbon dioxide as electron acceptors are studied under anaerobic conditions (with oxygen deficit).

A comparative assessment of pedogenetic processes in solonetzes (Calcic Gypsic Salic Solonetzes (Siltic, Albic, Cutanic, Differentic)) developing on terraces of lake depressions within the Volga–Ural interfluve of the Caspian Lowland has been performed on the basis of data on their macro- and micromorphological features and chemical, physicochemical, and physical properties. The studied soils have number of common characteristics shaped by the humus-accumulative, solonetzic, eluvial–illuvial, calcification, and gypsification processes. However, it is shown that macro- and micromorphological indicators of solonetzic processes (the development of clay–humus coatings and the character of structural units in the solonetzic (B) horizon) do not always agree with the modern physicochemical conditions of the development of this process. This is explained by differences in the degree and chemistry of the soil salinization and the depth and salinity of the groundwater. Solonetzes developing on the second terrace of Playa Khaki are distinguished by the highest water content and maximum thickness of the horizons depleted of soluble salts. They are characterized by the well-pronounced humus-accumulative process leading to the development of the light-humus (AJ) horizon. In other solonetzes, the accumulation of humus is weaker, and their topsoil part can be diagnosed as the solonetzic-eluvial (SEL) horizon. Active solodic process and illuviation of organomineral substances with the development of thick coatings and infillings in the B horizon are also typical of solonetzes on the second terrace of Playa Khaki. Micromorphological data indicate that, at present, layered clayey coatings in these soils are subjected to destruction and in situ humification owing to the active penetration of plant roots into the coatings with their further biogenic processing by the soil microfauna. The process of gleyzation (as judged from the number of Fe–Mn concentrations) is most active in solonetzes developing on the first terrace of Playa Khaki. These soils are also characterized by the highest degree of salinization with participation of toxic salts. The maximum accumulation of gypsum is typical of the heavy-textured horizons.