Том 52, № 4 (2019)

Climatic conditions are an important factor affecting mineralogical and chemical compositions of soils and paleosols with the formation of paleosol archives that reflect major stages of the evolution of biogeosphere systems in the Quaternary period. In the steppe zone of the south of the East European Plain, two types of the “time capsules” storing information on paleoecosystems and paleoclimate of the Quaternary period are found. First, these are loess/paleosol complexes in coastal zone of the Sea of Azov and in the North Caucasus; their environmental records extend back into the Pleistocene for about 800 ka. Second, these are Holocene paleosols of archeological sites; they are buried under kurgans constructed in different periods of the Middle and Late Holocene. The completeness and reliability of paleoenvironmental reconstructions depend on the chosen study objects. For quantitative reconstruction of the environmental parameters in the past, independent methods based on the assessment and interpretation of soil solid-phase properties—magnetic. mineralogical, geochemical, isotopic, etc.—are to be applied. Detailed mineralogical study of paleosols coupled with the analysis of their organomineral complexes and variations in the concentrations of biophile and lithophile elements significantly increase the reliability of soil indicators of the paleoclimatic conditions. The sets of soil indicators obtained from the study of Holocene paleosols and loess/paleosol sequences in the Sea of Azov region allow us to estimate parameters of the paleoenvironment: paleotemperature, paleoprecipitation, and aridity of the climate.

The content of lithium in soil-forming rocks, soils, and plants of forest-steppe, steppe, and dry-steppe landscapes of Transbaikalia has been studied. The mean Li content is 1.1 times higher in soil-forming rocks than the natural abundance (clarke) of this element in the Earth crust and is 1.1–1.3 times higher in the studied soils as compared to the clarke of this element in soils of the world. The Li content in soils is closely related to its amount in soil-forming rocks, while its correlation with the soil humus and Li concentration in plants is absent. Spatial and vertical distribution patterns of Li in soils of the studied landscapes are described. According to the coefficients of the biological uptake of Li by steppe, meadow, and agrogenic cenoses from soils (1.2–2.4), this element is assigned to the group of moderate accumulation. The mean Li content in steppe and meadow plants and crops is 1.3–2.3 times higher than its average content in terrestrial vegetation. Lithium concentrations reach toxic values (5–15 mg/kg) in plants of eight test plots in meadow cenoses. The accumulation of Li per unit area in the meadow vegetation is 10.5 times higher than that in the dry-steppe vegetation.

Background concentrations of heavy metals (Cu, Zn, Ni, Co, Fe, Mn, Cr, Pb, Hg, Cd, Ba, Sr, and Sc) in soils and bottom sediments were determined for the background and anthropogenically disturbed (oil and gas extraction) areas in the north of Western Siberia on the basis of long-term studies (1993–2017). It was found that the soils are characterized by relatively low concentrations of heavy metals. The major factors affecting the variability of the chemical composition of the environmental components are the lithological and chemical composition of the parent materials and the zonal–azonal geochemical differentiation related to peat accumulation. The statistical analysis and the method of ranked geochemical spectra suggested that background element concentrations should be separately determined for organic soil horizons, for mineral (illuvial) horizons in coarse-textured and heavy-textured soils, and for peatlands. Minimum concentrations of most of the studied heavy metals were determined in peatlands: they were 2–8 times lower than the concentrations of these metals in the clayey and loamy illuvial horizons. Mercury and cadmium were the exceptions: their concentrations in the peatlands were 3–4 times higher than those in the illuvial mineral horizons. Background metal concentrations in bottom sediments were separately calculated for three categories: clay and peaty clay sediments, silts, and fine-grained sands. Metals concentrations in clay sediments were significantly higher than those in sandy sediments: by 11 times for Fe and Mn; by 8.5 times for Ni; by 6.5 times for Co; and by 5 times for Zn, Cu, Cr, and V. The concentrations of metals were determined by the ICP MS method. The obtained data on the background concentrations of heavy metals can be recommended for the assessment of technogenic impact on local soils and bottom sediments in the course of the environmental monitoring.

Data on the contents of particulate organic matter (POM) in the humus horizons of different soil types were obtained. The influence of the land use system and fertilizers on the carbon of particulate organic matter (C_POM) in gray forest soil and typical chernozem was shown. The mineralization rate of POM under constant conditions of temperature and moisture was estimated, and the ratios between the pools of POM and biologically active organic matter in the soils were calculated. In the soils of natural cenoses, the percentage of POM together with the sand particle-size fraction varied within 12–36% of the soil mass, and the C_POM content varied from 1.66 to 8.03% of the fraction mass. The portion of C_POM in the total C_org ranged from 20 to 48%. Cultivated gray forest soil and typical chernozem were depleted of C_POM by 3.0–3.2 and 2.0–2.8 times, respectively, in comparison with the samples of noncultivated soils. The mineralization rate of POM in the gray forest soil and typical chernozem was about the same (7.9–12.1 and 7.2–8.2% of C_POM, respectively), which was about 1.2–2.4 times higher than the mineralization rate of the total soil organic matter. It was noted that POM could be a sensitive indicator of the C_org dynamics in the soil, a good predictor of changes in the content and quality of soil organic matter, and a significant source of potentially mineralizable organic matter in the soil.

The development of sandy soils under pine forests and the influence of forest fires on the soil properties have been studied in the Baikal region, The profile of background soils consists of a litter layer and a thin humus-accumulative horizon with features of grain bleaching in the lower part. In the WRB system, such soils are classified as Eutric Arenosols (Ochric). They have an acid reaction, fulvate humus, and slightly developed features of the Al–Fe-humus process. Post-pyrogenic soil successions depend on the type of fire. In fifteen years after the ground fire, a soil with specific pyrogenic horizons in the upper part of the profile was formed. It had a high content of carbonaceous matter and humus, a slightly acid reaction, and a relatively high content of exchangeable and total calcium. The soil humus was of the fulvate–humate type, and the humus pool considerably increased. These changes were related to the presence of charcoal microparticles adsorbing dispersed substances on their surface and detected in thin sections. After the crown fire with the destruction of the tree stand and activation of wind erosion, the features of pyrogenesis were poorly expressed in the soils. In this case, post-pyrogenic soils had a weakly developed immature profile, acid reaction, and a low content of humus of the humate–fulvate type. The properties of the background soils allow us to classify them as podzolized humic psammozems (Eutric Arenosols (Ochric)); the soils of post-pyrogenic successions after the ground fire can be classified as post-pyrogenic humic psammozems; after the crown fire, as humic psammozems.

Irrigated, withdrawn from irrigation, and nonirrigated areas with southern chernozems (Calcic Chernozems) and dark chestnut soils (Haplic Kastanozems) of different degrees of natural and irrigation-induced salinity and solonetzicity were examined within the Ingulets irrigation system in Kherson and Nikolaev oblasts with the aim to assess provisioning ecosystem services of salt-affected soils in Ukraine. The suggested system is based on the results of the eco-agromeliorative assessment of land for pilot areas and takes into account susceptibility of the ecosystem services of salt-affected and solonetzic soils to different kinds of reclamation. In most cases, the soils of nonirrigated areas were characterized by the satisfactory eco-agromeliorative status, and the soils irrigated by sprinkling and withdrawn from irrigation had the good or satisfactory status depending on the depth and salinity of the groundwater. The soils subjected to drip irrigation were in the unfavorable state because of noncompliance with recommended irrigation technologies. Irrigation with slightly saline water caused changes in the structure of soil microbial cenoses and disturbance of the optimal ratios between different groups of microorganisms. In these soils and in the soils withdrawn from irrigation because of the development of secondary salinization and alkalization, the numbers of major trophic groups of microorganisms (eutrophic and oligotrophic bacteria and actinomycetes) and the total soil enzymatic activity decreased. The assessment of susceptibility of the ecosystem services of salt-affected soils to reclamation impacts (chemical amelioration and deep meliorative plowing) demonstrated certain positive changes in the efficiency of soil ecosystem services, such as the productive capacity, the habitat of species, the storage pool for carbon, and the nitrogen fixation capacity. An expert ten-grade scale to assess the productive ecosystem services of salt-affected soils in Ukraine has been developed. It is based on eight characteristics. According to this scale, the areas with the good state of the soils are virtually absent in the examined territory; the satisfactory state has been assigned to 14 surveyed areas; and the unsatisfactory state, to one area with a shallow depth of saline groundwater. This approach provides for a more efficient use of the provisioning functions of salt-affected soils owing to differentiation of reclamation impacts on them and their adaptation to the functioning of biological systems.

The application of reclamation measures to improve the state and increase the fertility of irrigated secondary saline and solonetzic meadow-brown soils (Anthrosols) of the Ararat Plain is substantiated. The indices of soil fertility determining the yield of the main crops were studied. According to monitoring studies, the economic efficiency of different crops was estimated. It is shown that the income from the yield of winter wheat, alfalfa, vegetables, and melons on the soils without salinization and alkalization increases by 2, 2.7, 4.2, and 13.7 times, respectively. The following reclamation measures to improve the ameliorative state of the studied soils are proposed: cultivation of alfalfa, application of gypsum in doses of 12–64 t/ha, and washing of the soil with irrigation water; the amount of water in this case has to be increased by 1.5 times in comparison with the norm. The economic assessment of the proposed reclamation measures is given. The obtained results can be implemented in the farms of Armavir and Ararat regions of Armenia.

We compared the advantages of eluate and direct soil bioassay methods to reveal the overall toxicity of contaminated soils in a case study with (i) Eutric Fluvisols contaminated with heavy metals; (ii) cultivated Albic Retisols (Loamic, Aric, Cutanic, Ochric) artificially polluted with zinc and lead (550 mg/kg Pb + 880 mg/kg Zn); and (iii) Albic Retisols (Loamic, Cutanic, Ochric) artificially polluted with phosphogypsum (40%). We measured the total and water-soluble species of chemical elements in the samples. Bioassay tests included six different methods. Chemical and biological variables were aggregated by the principal component analysis. It was shown that toxicity values of tested samples in case of eluate test organisms (Ceriodaphnia affinis, Paramecium caudatum, Scenedesmus quadricauda, and bacterial test system Escherichia coli) characterized the studied soils as less toxic than direct soil bioassay tests (Eisenia fetida and Sinapis alba). Finally, we discussed possible ways to improve the informative value of the ecotoxicological assessment of soils by bioassay tests.