A. N. Gennadiev

Polycyclic aromatic hydrocarbons in soils: Sources, behavior, and indication significance (a review)

The current ideas of polycyclic aromatic hydrocarbons (PAHs) in soils are reviewed. Their natural and anthropogenic sources are discussed, and the mechanisms of their arrival from other environmental components to soils are considered. The main processes typical for PAHs in soils are defined; the sorption, degradation, and translocation features of polyarenes in the soil profile are shown. Attention is paid to the geographical features of the PAH distribution in soils. The use of data on the PAHs in soils for the indication of different natural and technogenic processes is also discussed.

Pyrogenic Polycyclic Aromatic Hydrocarbons in Soils of Reserved and Anthropogenically Modified Areas: Factors and Features of Accumulation

The accumulation features of pyrogenic polycyclic aromatic hydrocarbons (PAHs) in soils were analyzed depending on the type of burning material and the combustion conditions (the temperature, oxygen access, and dispersion of the combustion products). The PAH accumulation features in the soils of three reserved areas of forest, steppe, and peat fires were revealed. The distribution features of the PAHs resulting from the anthropogenic pyrogenic processes (the household combustion of wood and the inflammation of coal dumps) in soils were established. The differences in the qualitative composition of the PAHs arriving to the soils from the different pyrogenic sources were shown.

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.

Soil Erosion under Different Land Uses: Assessment by the Magnetic Tracer Method

A new method of magnetic tracer was applied by the authors for a quantitative assessment of erosional processes. The rates of erosion were determined for cultivated and virgin soils (predominantly, chernozems) on slopes in different parts of the United States and Russia. Quantitative parameters of soil loss and soil deposition for the slopes of different shapes and aspects were found. Specific features of erosional processes within different parts of slopes were revealed. The relationships between the intensity of erosion and the humus state of the soils were characterized, and the effect of land use on the rates of soil erosion was estimated.

The maps of soil tolerance toward pollution with oil products and polycyclic aromatic hydrocarbons: Methodological aspects

Natural factors ensuring soil tolerance toward pollution with technogenic hydrocarbons, particularly, oil products and polycyclic aromatic hydrocarbons, are considered. The maps of the self-purification capacity of the soils of Russia and its particular humid and arid regions with respect to their contamination with technogenic hydrocarbons are analyzed. The principles lying in the basis of these maps are discussed. It is argued that the cartographic assessment of soil tolerance toward pollution with technogenic hydrocarbons is necessary for setting the values of maximum permissible concentrations of hydrocarbons in soils, for the choice of adequate soil rehabilitation procedures, and for the organization of soil monitoring.

The influence of fires on the properties of forest soils in the Amur River basin (the Norskii Reserve)

The influence of forest fires on the properties of taiga brown, gley taiga brown, and alluvial bog soils widespread in the area of the Norskii Reserve (the Amur River basin) was studied. During several years after the fire, the humus content increased, especially in the soils subjected to fires of high intensity. In the soils of steep slopes, the humus content decreased due to damage to the forest vegetation and activation of lateral runoff after the fire. As a rule, in the soils subjected to fire, the C ha-to-C fa ratio increased and correlated with the fire intensity. Some relationships between the forest fires and the acid-base properties of the soils were revealed. After the fires, the pH values often became higher. The stronger the fire, the higher the pH values. The stony soils differed from the other ones, since the reaction of their upper horizons turned out to be more acid after the fires. The analysis of the authors’ and literature data showed that the pyrogenic changes of some soil properties have been poorly studied and need further investigation, including their geographical aspects.

Hydrocarbons in Soils: Origin, Composition, and Behavior (Review)

It has been shown that a large body of evidence on the sources, transformation, and migration of hydrocarbons in soils has been acquired by different researchers. Available data about the origin and behavior of hydrocarbon gases, total petroleum hydrocarbons, polycyclic aromatic hydrocarbons, alkanes, and other compounds have been considered successively. A wide range of natural and anthropogenic factors affecting the transformation and migration of hydrocarbons in soils have been analyzed. The indicative value of these compounds has been explained. At the same time, many problems related to hydrocarbons in soils are still insufficiently understood. Sparse and fragmentary data are available in the literature on the interaction of different hydrocarbon groups in the soil. Few data refer to the features of hydrocarbons in background zonal soils; there are almost no interzonal comparisons. The behavior of hydrocarbons in soils of different landscape-geographical positions is characterized in isolated publications. The hydrocarbon status of soils as an integral complex of interrelated hydrocarbons is almost not analyzed. Hydrocarbons of a single class (polycyclic aromatic hydrocarbons, hydrocarbon gases, n-alkanes, etc.) are usually characterized in each publication.

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.

Accumulation of Organic Carbon in Chernozems (Mollisols) under Shelterbelts in Russia and the United States

Shelterbelts that were created in place of meadow and meadow-steppe landscapes of the forest-steppe zone of northern continents serve as areas of carbon accumulation and participate in the formation of soil organic matter. In the Great Plains of the United States (in North Dakota, South Dakota, and Nebraska) and on the Central Russian Upland (Belgorod, Voronezh, and Kursk oblasts), a general tendency toward an increase in the Corg pool in the topsoil (0–30 cm) from the marginal parts of the shelterbelts toward their central parts by about 3.5–10.0 t per each 10 m has been identified. In 55 years of the existence of shelterbelts on chernozems in the European part of Russia, the mean annual rate of the organic carbon accumulation in the upper meter has been varying within 0.7–1.5 t/ha. In 19 years of the existence of a shelterbelt in the area of Huron (South Dakota), the mean annual rate of the organic carbon accumulation in the 1-m-thick layer of the Bonilla soil series (Haplustolls) has reached 1.9 t/ha.

Hydrocarbon status of soils in an oil-producing region with karst relief

Features and factors of the hydrocarbon status of soils developed in oil-producing karst regions were considered using an oilfield as an example. The notion of the hydrocarbon status of soils involves the proportions of the gas, bitumen, and polyarene components of the total hydrocarbons and their radial and lateral variations. The following types of soil hydrocarbon status were identified: (1) the background (reference) type; (2) the first kind of emanation type related to soil degassing (most probably, in an oilfield); (3) the technogenic type developed in the areas of oil spills, contaminated surface runoff, and industrial waste storage; and (4) the emanation type of the second kind related to the degassing and evaporation of spilled oil and other substances in underground karst caves. It was shown that the data on the hydrocarbon status of the soils can be used for the identification of hydrocarbon areas in the soil cover and the indication of the sources of pollutants deteriorating the environmental conditions in the landscape.