R. G. Kovach

Spatial and temporal features of soil erosion in the forest-steppe zone of the East-European Plain

Data on the rate of the erosion-accumulation processes within the sloped junctions of soils studied on key plots in Tula, Kursk, and Belgorod oblasts were analyzed. Using the method of different-age tracers characterizing the erosion-aggradation of the soils during the last 140–150 years (the magnetic tracer) and during the last 20–25 years (the radiocesium tracer), the spatial and temporal features of the redistribution of the drifts on typical slopes in different parts of the forest-steppe zone of the East-European Plain were established. A clear trend of an increase in the soil erosion rate in this zone during the last 20–25 years was revealed compared to the average rate for the last 140- to 150-year-long plowing period, which was related to the climate warming, an abrupt reduction of the surface runoff during the spring snowmelt period, and the increasing soil-protecting role of the agricultural plants in the crop rotations because of the decrease in the proportion of row crops. The obtained results confirmed the continuous nature of the soil erosion and accumulation during the transport of the sediments, which was manifested in the alternation of the erosion zones and deposition zones on the slopes.

Factors and features of the hydrocarbon status of soils

The hydrocarbon status (HCS) of soils has been characterized using a set of quantitative parameters, which can be obtained in the routine laboratory studies of soil samples. This is a general quantitative and qualitative characterization of hexane bitumoids and individual polycyclic aromatic hydrocarbons prevailing in natural objects. Field survey of soil air has been performed in order to determine the composition and content of gaseous hydrocarbons. The features and factors of soil HCS formation have been studied in soils of eight key sites in forest, steppe, and dry-steppe landscapes of European Russia. Along with zonal diversity, the presence of any local anomalous natural or technogenic factor capable of affecting the soil HCS (gas emanations from the deep lithosphere, specific parent rocks, pollutant fallout from the atmosphere, confinement to an oil field, etc.) has been used as the criterion of their selection. It has been shown that, just as the humus and salt statuses of soils have become their important integrated characteristics, so the study of soil HCS allows reaching a new level of knowledge of the nature of soils and their processes. The parameters of soil HCS adequately reflect the features of bioclimatic and topolithological factors of pedogenesis, the properties of soils, and the level of technogenic impact on the soil cover. Accumulation of new factual data and refinement of soil-geographical studies are necessary for more thorough study of soil HCS.

Hydrocarbon status of soils under atmospheric pollution from a local industrial source

Contents and compositions of bitumoids, polycyclic aromatic hydrocarbons (PAHs), and free and retained hydrocarbon gases in soils along a transect at different distances from the local industrial source of atmospheric pollution with soot emissions have been studied. The reserves of PAHs progressively decrease when the distance from the source increases. Among the individual PAHs, the most significant decrease is observed for benzo[a]pyrene, tetraphene, pyrene, chrysene, and anthracene. On plowlands, the share of heavy PAHs—benzo[ghi]perylene, benzo[a]pyrene, perylene, etc.—is lower than in the forest soils. In automorphic soils of the park zone adjacent to the industrial zone, the penetration depth of four-, five-, and sixring PAHs from the atmosphere is no more than 25 cm. In soils under natural forest vegetation, heavy PAHs do not penetrate deeper than 5 cm; in tilled soils, their penetration depth coincides with the lower boundary of plow horizons. Analysis of free gases in the soil air revealed hydrocarbons only under forest. From the quantitative and qualitative parameters of the content, reserves, and compositions of different hydrocarbons, the following modification types of hydrocarbon status in the studied soils were revealed: injection, atmosedimentation–injection, atmosedimentation–impact, atmosedimentation–distant, and biogeochemical types.

Hydrocarbon Status of Soils under Different Ages of Oil Contamination

Modifications of the hydrocarbon status (HCS) of soils at the stages of the injection input of oil pollutants and the subsequent self-purification of the soil layer from technogenesis products have been revealed in studies conducted on an oil field. Comparison with the HCS of background soils has been performed. Changes in the composition and concentration of bitumoids, polycyclic aromatic hydrocarbons (PAHs), and hydrocarbon gases have been established. The HCS of a freshly contaminated soil is characterized by the predominance of butane (the highest component) in the gaseous phase, an abrupt increase in the concentration of second-kind bitumoids, and a 100-fold increase in the content of PAHs compared to the background soil. In the old contaminated soil, free and fixed methane becomes the predominant gas; the content of bitumoids in the upper soil horizons is lower than in the freshly contaminated soils by two orders of magnitude but higher than in the background soil by an order of magnitude; the PAH composition in the soil with old residual contamination remains slightly more diverse than in the background soil.

Lateral migration of soil solid-phase material within a landscape-geochemical arena detected using the magnetic tracer method

Thorough studies of the lateral migration of the solid soil material and the large-scale mapping of the soil cover have been performed within a landscape-geochemical arena in the small catchment area of the Lokna River basin (Tula oblast). Podzolized clay-illuvial agrochernozems are the predominant soils in the catchment area. Nine soil types from four orders according to the 2004 soil classification have also been described. The morphological analysis of the soil profile structures revealed their changes related to the lateral migration of the solid-phase products of the pedogenesis. From the estimated reserves of the spherical magnetic particles as tracers of the mass transfer, the accumulation and dispersion zones of the solid-phase material in the soil cover have been separated and conclusions about the genesis of these zones and their place in the migration structure of the catchment basin have been drawn. The soil catenas within the landscape-geochemical arena have been classified in accordance with the migration intensity of the soil solid-phase material, the localization of deposits, and the degree of openness of the soil-geochemical conjugations. The effect of the lateral migration of the soil solid-phase material on the structure of the microarena soil cover and the soil genetic profiles has been revealed.

Comparative assessment of the contents of magnetic spherules, 137Cs, and 210Pb in soils as applied for the estimation of soil erosion

The contents of magnetic spherules and 137Cs and 210Pb isotopes were determined in gray forest soils of the Novosil Agroforest Experimental Station in Orel oblast (central part of European Russia). The spatial variability in the contents of these substances was studied, and their distribution in the soil profiles and along soil transects within the afforested and cultivated slopes was analyzed. Factors and processes favoring the accumulation of magnetic spherules and 137Cs and 210Pb isotopes in the soils, as well as their removal from the soils, were revealed. Similarities and distinctions in the patterns of their behavior were interpreted. Prospects for the combined use of these three tracers to estimate the rates of soil erosion and sediment deposition on the soil surface were tested.

Hydrocarbon Status of Alluvial Soils in the Istra Morphostructural Node (Moscow Oblast)

The effect of the current block structure of the earth’s crust and its most active sites (morphostructural nodes) on the natural hydrocarbon status of alluvial soils has been considered. Studies have been performed in the Istra district of Moscow oblast within the Istra morphostructural node. The node represents an area of increased geodynamic activity of the earth’s crust located at the convergence or intersection of block boundaries: mobile linear zones following large river valleys with alluvial soils. Soil cover mainly consists of alluvial humic-gley soils (Eutric Gleyic Fluvisols) of different depths and alluvial mucky-gley soils (Eutric Gleyic Histic Fluvisols). Some soils manifest stratification. Two factors forming the hydrocarbon status of soils are considered: soil processes and the effect of geodynamic activity, which is manifested within the morphostructural node. The contents of bitumoids and retained methane and butanes in alluvial soils appreciably increase at the entry of river valley into the node. The occurrence frequency of 5–6-ring polycyclic aromatic hydrocarbons (perylene and benzo[ghi]perylene) in mineral horizons increases. It has been concluded that alluvial soils within the Istra morphostructural node are characterized by the biogeochemical type of hydrocarbon status with signs of emanation type at sites with the highest geodynamic activity.

Hydrocarbon status of soils in the asphalt deposit area (Samara Bend)

The composition and distribution features of the main components of soil hydrocarbon complex― organic (noncarbonate) carbon, hexane bitumoids, and individual polycyclic aromatic hydrocarbons (PAHs)―in the area of depleted Bakhilovo asphalt deposit (Samara oblast) have been studied. According to their proportions, three genetic types of soil hydrocarbon status are distinguished: (a) emanation–injection type prevailing within the limits of the former production field and characterized by anomalous contents of heavy resinous bitumoids (5000–7000 mg/kg on the average) throughout the soil profile and a high content of PAHs (4–9 mg/kg on the average, 29 mg/kg as the maximum, with the dominance of naphthalene homologues); (b) emanation–biogeochemical type confined to mechanogenically undisturbed soils within and beyond the deposit area, where the emanation component is manifested in soils with heavy texture and higher concentrations and very light composition of bitumoids in the lower parts of the soil profile; and (c) atmosedimentation–biogeochemical type characteristic of conventionally background soils with light texture; benzo[a]pyrene traces are detected among PAHs in the upper soil horizon, which indicates the input of this hydrocarbon with aerosols from the atmosphere; the concentrations of bitumoids and PAHs in parent rocks are lower than in the soils.

Laboratory analytical methods for the determination of the hydrocarbon status of soils (a review)

Laboratory analytical methods suitable for the determination of the hydrocarbon status of soils (a specific soil characteristic involving information on the total content and qualitative features of soluble (bitumoid) carbonaceous substances and individual hydrocarbons (polycyclic aromatic hydrocarbons, alkanes, etc.) in bitumoid, as well as the composition and content of hydrocarbon gases) have been considered. Among different physicochemical methods of study, attention is focused on the methods suitable for the wide use. Luminescence-bituminological analysis, low-temperature spectrofluorimetry (Shpolskii spectroscopy), infrared (IR) spectroscopy, gas chromatography, chromatography–mass spectrometry, and some other methods have been characterized, as well as sample preparation features. Advantages and limitations of each of these methods are described; their efficiency, instrumental complexity, analysis duration, and accuracy are assessed.

Bituminous substances and polycyclic aromatic hydrocarbons in soils under lenses of oil and oil products in underground karst cavities (Polaznenskii Peninsula, Perm region)

Bituminous substances and polycyclic aromatic hydrocarbons in soils under karst rocks have been studied for revealing fluxes of oil and oil products in karst cavities near the earth’s surface (with the Polaznenskii Peninsula in Perm region as an example). It has been found that the hydrocarbon fluxes from underground oil lenses to the surface can be directly detected from the nonspecific organic components of soils and the composition of free gases circulating in soils. Changes in the soil-geochemical parameters indicative of the presence of an underground oil lens have been revealed. It has been shown that the hydrocarbon fluxes from underground oil lenses to the surface can be mapped from nonspecific organic soil components: composition and amount of bituminous substances, polycyclic aromatic hydrocarbons, and gaseous hydrocarbons.