Showing papers in "Eurasian Soil Science in 2008"
TL;DR: In this article, the major mechanisms of sulfate adsorption were considered, including the most important of them: the ligand exchange with the formation of surface outer and innersphere complexes and the Coulomb interaction with the surface of mineral particles.
Abstract: The literature data on the adsorption of sulfates by soils were reviewed. Factors affecting the adsorption of sulfates and the major mechanisms of sulfate adsorption were considered, including the most important of them: the ligand exchange with the formation of surface outer-and innersphere complexes and the Coulomb interaction with the surface of mineral particles. Equations describing the adsorption isotherms of sulfates are given; some methods for the mathematical simulation of sulfate ion behavior in the “soil solid phase-soil solution” system are discussed.
56 citations
Abstract: A parallel scheme of extractions was used for determining heavy metal compounds in uncontaminated and artificially contaminated soils of Rostov oblast. A method for calculating the contents of complex and specifically adsorbed metal compounds from the difference in their concentrations in different extracts was suggested. It was found that the portion of firmly fixed metal compounds decreases and the portion of potentially mobile (exchangeable, complex, and specifically adsorbed) metal compounds increases with an increase in the degree of contamination of chernozems and chestnut soils with lead, copper, and zinc over a one-to two-year-long observation period. This was due to the capacity of heavy metal ions to substitute for the exchangeable cations in the exchange complex of the studied soils, to form complexes with the soil organic matter, and to participate in the specific adsorption. Some differences in the behavior of different metals were found.
55 citations
TL;DR: The susceptibility of soil organic matter (SOM) to mineralization decreases in the following sequence of zonal soils: tundra soil > soddy-podzolic soil > gray forest soil > chestnut soil > chernozem as discussed by the authors.
Abstract: The susceptibility of soil organic matter (SOM) to mineralization decreases in the following sequence of zonal soils: tundra soil > soddy-podzolic soil > gray forest soil > chestnut soil > dark chestnut soil > chernozem. The content of potentially mineralizable organic matter in the plowed soils is 1.9–3.9 times lower than that in their virgin analogues. The highest soil carbon sequestration capacity (SCSC) is typical of the leached chernozems, and the lowest SCSC is typical of the tundra soil. Taking into account the real soil temperatures and the duration of the warm season, the SCSC values decrease in the following sequence: leached chernozem > dark chestnut soil > chestnut soil ≥ tundra soil > gray forest soil > soddy-podzolic soil. Arable soils are characterized by higher SCSC values in comparison with their virgin analogues.
41 citations
TL;DR: In this article, a combined approach for fractioning metal compounds in soils on the basis of sequential and parallel extractions is proposed, which is used to assess the group composition of Zn, Cu, and Pb compounds in an ordinary chernozem and its changes upon the soil contamination with metals.
Abstract: A combined approach for fractioning metal compounds in soils on the basis of sequential and parallel extractions is proposed. This approach has been used to assess the group composition of Zn, Cu, and Pb compounds in an ordinary chernozem and its changes upon the soil contamination with metals. The contents of firmly and loosely bound metal compounds that are presumably fixed by the particular soil components (organic substances, carbonates, and silicate and nonsilicate minerals) have been determined.
33 citations
TL;DR: A review of world investigations into the geochemistry of stable isotopes is presented in this article, where the authors focus on two major directions: reconstruction of the environmental conditions and indication of the soil processes.
Abstract: A review of world investigations into the geochemistry of stable isotopes—a new area for soil science—is presented. Studies of the behavior of stable isotopes in soils are being developed in two major directions: reconstruction of the environmental conditions and indication of the soil processes. Investigations into the reconstruction of the environmental conditions are based on the assumption that the isotopic composition of carbon in the soil humus is inherited from and reflects the isotopic composition of carbon in the corresponding vegetation (the source of soil humus). At the same time, studies into the indication of soil processes are based on the effects of fractionation of carbon isotopes in the course of transformation of carbon compounds. In this case, the isotopic composition of carbon in the soil humus should differ from that in the initial plant material. The analysis of available data suggests that the current state of research does not allow assessing the entire diversity of the effects of isotopic fractionation in soils. New data on the isotopic composition of carbon of soil organic matter and carbonates are being actively accumulated at present. However, it is obvious that the effect of isotopic fractionation should be taken into account in the paleoenvironmental and paleoclimatic reconstructions.
31 citations
TL;DR: In this paper, temperature regimes of eleven plots with tundra soils were studied in the northeastern part of European Russia within the discontinuous permafrost zone, and the duration of soil temperature records ranged from 1 to 9 years.
Abstract: Temperature regimes of eleven plots with tundra soils were studied in the northeastern part of European Russia within the discontinuous permafrost zone. The duration of soil temperature records ranged from 1 to 9 years. The selected plots were representative of the diversity of landscape and soil conditions in the study area. Virgin tundra soils, a cultivated soil under sown grassland, and soils of secondary biocenoses that developed in place of the former sown grasslands were studied. It was shown that the winter and mean annual temperatures in the permafrost-affected soils drastically differ from those in the soils without permafrost, though the summer temperatures in the root zone of both soil groups are relatively similar. The soil temperature regimes were classified according to Russian (Dimo, 1972) and American (Soil Taxonomy, 1999) classification systems. The degree of detail provided by the Russian system proved to be somewhat greater; at the same time, in contrast to the American system, it does not make it possible to distinguish the soils with warm permafrost in the discontinuous permafrost zone from the soils without permafrost at all.
31 citations
TL;DR: An integrated study of the qualitative and quantitative composition of polycyclic aromatic hydrocarbons (PAHs) in the atmospheric precipitation-soil-lysimetric water system was performed using high performance liquid chromatography.
Abstract: An integrated study of the qualitative and quantitative composition of polycyclic aromatic hydrocarbons (PAHs) in the atmospheric precipitation-soil-lysimetric water system was performed using high performance liquid chromatography. It was shown that the accumulation of low-molecular PAHs (phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, and chrysene) in soils is due to the transformation of organic matter and the regional transport and deposition of PAHs with atmospheric precipitation on the underlying surface. High-molecular polyarenes (benz[b]fluoranthene, benz[k]fluoranthene, benz[a]pyrene, dibenz[a,h]anthracene, benzo[ghi]perylene, and indeno[1,2,3-cd]pyrene) mainly result from the decomposition of soil organic matter.
27 citations
TL;DR: In this paper, the effect of the initial moisture content on the spatial distribution of the water retention was investigated in the field, and the results showed that the preferential flow was more evident in the case of the dry initial soil water content than for the two wetter initial conditions.
Abstract: The initial soil moisture content affects the water flow and solute transport through the vadose zone, but researchers are in disagreement about the extent and nature of its effects. Better understanding of the initial moisture effect on the water movement will help to prevent groundwater contamination and increase crop production by improving the efficiency of water use in irrigation practice. Therefore, in this study, the effect of the initial moisture content on the spatial distribution of the water retention was investigated in the field. A total of 4 cm of water was applied to duplicate plots with each of three initial moisture conditions within 2 h using a rainfall simulator. Following the application and a 2-h redistribution period, 100 soil samples were taken from different depths of each plot using a grid sampling system to be analyzed for their gravimetric water content in the laboratory. Statistical and geostatistical analyses were performed to analyze the spatial structure of the collected data. The results showed that the preferential flow was more evident in the case of the dry initial soil water content than for the two wetter initial conditions. Both the classical and geostatistical analyses supported that the overall water retention was uniformly distributed throughout the profile except at 20–30 cm, where the coefficient of variation and the percent nugget to total semivariance ratio were high, indicating some degree of preferential flow through large pores (macropores). These results suggest that similar studies should be conducted on different field soils under more different initial moisture conditions so that the effect of the macropores on the water flow and chemical transport can be better understood.
27 citations
TL;DR: An assessment of the ecological state of soils has been performed in the area of mining and metallurgical enterprises of Norilsk Nickel Company with respect to the level of soil contamination by heavy metals, the state of the vegetation, and the biological activity of the soils.
Abstract: An assessment of the ecological state of soils has been performed in the area of mining and metallurgical enterprises of Norilsk Nickel Company with respect to the level of soil contamination by heavy metals, the state of the vegetation, and the biological activity of the soils. The territory within 4 km from Norilsk is characterized by high concentrations of heavy metals, the absence of trees, and the disturbance of the organic matter mineralization. This zone corresponds to level 5 of the loss of environmental quality. At distances of 4–16 km from the city, the state of the environment corresponds to level 4, and, at distances of 16–25 km, to level 3. In the latter zone, the soils are characterized by increased concentrations of acid-soluble and mobile metal compounds, though the concentrations of water-soluble metal compounds do not exceed the maximum permissible levels; the soil microbiological activity is normalized. The state of the environment at a distance of 25 km from Norilsk is close to level 2. Soil contamination with heavy metals is accompanied by a rise in the portion of Cu, Ni, and Co compounds bound with amorphous iron oxides and hydroxides, as well as in the portion of their mobile forms.
25 citations
TL;DR: In this article, the ages of microbial fractions isolated from the buried and surface soils were determined using the method of 14C atomic mass-spectrometry, which reached 2100 years in the A1 horizon of the buried paleosol, which corresponded to the archaeological age of the kurgan (1st century AD).
Abstract: Chestnut paleosols buried under steppe kurgans about 4800, 4000, and 2000 years ago and their background analogues were studied in the dry steppe zone on the Volga-Don interfluve. Morphological, chemical, microbiological, biochemical, and radiocarbon studies were performed. Paleoclimatic conditions in the region were reconstructed on the basis of paleosol data. The ages of microbial fractions isolated from the buried and surface soils were determined using the method of 14C atomic mass-spectrometry. It reached 2100 years in the A1 horizon of the buried paleosol, which corresponded to the archaeological age of the kurgan (1st century AD). The ages of microbial biomass isolated from the B2 horizons of the buried paleosol and the background surface soil comprised 3680 ± 35 and 3300 ± 30 years, respectively. The obtained data confirmed our assumption about preservation of microorganisms of the past epochs in the paleosols buried under archaeological monuments. It is ensured by various mechanisms of adaptation of soil microbial communities to unfavorable environmental conditions (anabiosis, transformation of bacteria into nanoforms, etc.). The possibility to stimulate germination of the ancient dormant microbial pool isolated from the buried paleosols by 2–3 orders of magnitude with the use of β-indolyl-3-acetic acid as a signal substance was demonstrated.
25 citations
TL;DR: In this article, the authors have shown that carbon reserves in soils generally increase upon soil exclusion from agricultural use and that carbon accumulation in abandoned soils depends on the soil type, the time elapsed since the soil abandoning (the restoration period), and the thickness of the layer for which the rate of carbon accumulation is determined.
Abstract: Experimental studies and the analysis of published data have shown that carbon reserves in soils generally increase upon soil exclusion from agricultural use. The rate of carbon accumulation in the abandoned soils depends on the soil type, the time elapsed since the soil abandoning (the restoration period), and the thickness of the layer for which the rate of carbon accumulation is determined. For the upper 20-cm-thick layer, it varies from 66 to 175 g C/m2 per year in dependence on the type of soil and averages 111 g C/m2 per year. The highest rate is typical of the first 10–15 years of soil restoration. According to our calculations, the carbon sequestration in the upper 20-cm-thick layer of Russian soils due to changes in land use was 184–673 Mt C in 1990–2005 and may reach 282–1030 Mt C by 2020.
TL;DR: In this paper, the authors obtained quantitative estimates for the biogoecenotic variation of the carbon pool in autonomous soils of the European territory of the former USSR, which indicated a high spatial variability of this parameter.
Abstract: Quantitative estimates were obtained for the biogoecenotic variation of the carbon pool in autonomous soils of the European territory of the former USSR, which indicated a high spatial variability of this parameter. The variation coefficient for carbon pool in the 0- to 1-m soil layer can reach 60% even in similar biogeocenoses within the same bioclimatic region. Parameters of intrabiogeocenotic variability of carbon pool in the soil were discussed. Their relationships with the type of biogeocenosis, vegetation, and soil moisture conditions were considered.
TL;DR: In this paper, the influence of forest fires on the properties of alluvial bog soils in the Norskii Reserve (the Amur River basin) has been studied, and some relationships between the forest fires and acid-base properties of the soils were revealed.
Abstract: 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.
TL;DR: In this paper, the composition and accumulation patterns of priority polycyclic aromatic hydrocarbons (PAHs) in soils of Vasilievsky Island in Saint Petersburg were studied.
Abstract: The composition and accumulation patterns of priority polycyclic aromatic hydrocarbons (PAHs) in soils of Vasilievsky Island in Saint Petersburg were studied. Concentrations of benzo[a]pyrene were found to exceed maximum permissible concentrations in all the samples, and the maximum recorded concentration exceeded the MPC by 50 times. Concentrations of other PAHs also exceeded the background values. The main soil pollutants were found to be fluoranthene, pyrene, benzo[b]fluoranthene, benzo[a]pyrene, and benzo[g, h, i] perylene, the part of which in the total content of PAHs was 65–80%.
TL;DR: In this article, the authors studied virgin, cultivated, and old-arable soils in the area of Olbia, one of the antique poleis in the northern part of the Black Sea region and showed that the soils cultivated during the antique time still preserve some features differing them from their virgin analogues.
Abstract: Virgin, cultivated, and old-arable soils have been studied in the area of Olbia, one of the antique poleis in the northern part of the Black Sea region. It is shown that the soils cultivated during the antique time still preserve some features differing them from their virgin analogues. In the course of agrogenic evolution, progressive changes in the morphology of dry steppe soils are not accompanied by the improvement of soil aggregation at lower levels. Macromorphological indices attest to the enhanced development of humification processes and leaching of carbonates and soluble salts in the soils cultivated during the antique time. At the same time, a number of soil degradation processes are vividly manifested in the cultivated soils. It is suggested that this process can be referred to as the soil allopseudomorphosis.
TL;DR: The thermal diffusivity of the upper horizons of model soddy-podzolic soils in the lysimeters depends on their water contents and varies within 2.1-4.1 m 2 /s as discussed by the authors.
Abstract: The thermal diffusivity of the upper horizons of model soddy-podzolic soils in the lysimeters depends on their water contents and varies within 2.1-4.32 × 10 -7 m 2 /s in the Ap horizon, 1.59-3.99 × 10 -7 m 2 /s in the B1 horizon, 1.28-3.74 × 10 -7 m 2 /s in the plowed B2 horizon, and 1.12-4.10 × 10 -7 m 2 /s in the B2 horizon. The dependence of the thermal diffusivity on the soil water content is described by an inverted parabolic curve for the Ap horizon, an S-shaped curve for the B1 and B2 horizons, and by a curve of transitional type for the plowed B2 horizon. The temperature regimes of model soils with different morphologies of the profile do not differ much and are close to the soil temperature regime under natural conditions on the plots of the weather station of Moscow State University.
TL;DR: In this article, the chemical properties of the saline-alkali soils are largely related to the presence of soda (Na2CO3, NaHCO3) in the soils.
Abstract: Diagnostics, methods of evaluation, and geography of saline-alkali (soda) soils are discussed. The saline-alkali soils include soils of different genetic types with the following chemical properties: the pH of the water suspensions equal to or higher than 8.5; the total alkalinity exceeding 1.4 meq/100 g of soil and the sum of water-soluble calcium and magnesium; and the presence of soluble “alkaline” salts in the soil profiles, the hydrolysis of which results in the alkaline reaction of the soils. The chemical properties of the saline-alkali soils are largely related to the presence of soda (Na2CO3, NaHCO3) in the soils. According to their morphological properties, saline-alkali soils are divided into two groups: alkaline soils with an undiferentiated profile and without a morphologically pronounced solonetzic (natric) horizon, and alkaline soils with a pronounced natric horizon (solonetzes). Solonetzes, in turn, are divided into (a) alkaline solonetzes (with soda or with soda and neutral salts), (b) solonetzes salinized with neutral salts (saline soils) with increased alkalinity in the solonetzic and lower lying horizons, (c) saline solonetzes throughout the profile, and (d) leached solonetzes containing no soluble salts in the profile and almost no exchangeable sodium in the soil exchange complex (SEC) (“dead” solonetzes). The latter two groups of solonetzes cannot be ranked among the alkaline soils. The alkalinity of the saline-alkali soils under study is due to carbonate and bicarbonate ions (carbonate alkalinity), organic acid anions (organic alkalinity), and borate ions (borate alkalinity). The carbonate alkalinity is due to both soda (Na2CO3, NaHCO3) and CaCO3.
TL;DR: In this article, the need for the All-Russia soil-geographic database satisfying international standards is substantiated and the procedure for creating the State Soil-Geographic Database of the Russian Federation is described.
Abstract: The need for the All-Russia soil-geographic database satisfying international standards is substantiated. Soil functions and the role of soils as a natural resource are analyzed. The soil resources of Russia are briefly described, and the problem of soil degradation is discussed. It is shown that the Russian legislative base regulating soil management and soil conservation policies is in a very poor state and requires improvement. The world policy of soil conservation is compared with the situation in Russia. The procedure for creating the State Soil-Geographic Database of the Russian Federation is described. It is supposed that it will consist of three major directions: the creation of a geographic database on a scale of 1: 2.5 M, the creation of a database of soil profiles, and the creation of a generalized database of the factors of soil formation and morphogenetic soil features. In addition, information about the economic use of typological soil units distinguished on the Soil Map of Russia on a scale of 1: 2.5 M (2007) will be aggregated.
TL;DR: The results of long-term studies of chernozem development in anthropogenically disturbed landscapes of the forest-steppe zone are discussed in this paper, where critical points and characteristic times of the formation of humus horizons are determined.
Abstract: The results of long-term studies of chernozem development in anthropogenically disturbed landscapes of the forest-steppe zone are discussed. Parameters characterizing the formation of the humus horizon of chernozems and the rate of this process are presented. Critical points and characteristic times of the formation of humus horizons are determined. The regeneration of soil properties as dependent on the degree of anthropogenic disturbance of chernozems is estimated.
TL;DR: In this paper, a typical small watershed named Tongshuang in the black soil region of northeast China, which was subjected to drastic erosion before 1980 and was managed subtly after 1980, was chosen as a study area.
Abstract: Soil organic carbon is a soil property of central importance for soil quality and the global carbon cycle. Studies specifically aimed at the relationship between the spatial variation of soil organic carbon and environmental factors are few. In this paper, a typical small watershed named Tongshuang in the black soil region of northeast China, which was subjected to drastic erosion before 1980 and was managed subtly after 1980, was chosen as a study area. Classical statistic and geostatistic analysis methods, in combination with a geographic information system (GIS), were used to quantitatively research the spatial variation characteristics of the soil organic carbon and their relation to the topographic factors and land use. The data on the soil organic carbon, topographic factors, and land use were obtained by soil sampling and measurements derived from DEM, remote sensing images, and field investigations, respectively. The classical statistics analysis results indicated that the variability of the soil organic carbon was moderate (Cv = 0.30). The slope position and land use types were the most discriminating factors. The soil organic carbon content was the highest in the grassland and lowest in the coniferous forest (P < 0.01). It increased gradually along the slope position gradients from the interfluve to the toe slope. The geostatistics analysis showed that the soil organic carbon had a strong spatial correlation. The C0/(C0 + C) was 0.1608, which was mainly induced by structural factors. The mean soil organic content is 2.27% in this watershed. It is on a very low level in the northern black soil of northeast China. In this small watershed of the eroded black soil region, the present soil and water conservation measures play an important role in controlling the soil loss. However, the soil organic carbon’s restoration is unsatisfactory. Nearly three-quarters of the land has worrisome productivity. How to improve the soil organic carbon content while targeting the soil fertility is a pressing need.
TL;DR: A concept of the relationship between the electrical parameters of soils and their pedogenesis was advanced on the basis of the known classical laws of electromagnetism and the general theory of pedogenesis as mentioned in this paper.
Abstract: A concept of the relationship between the electrical parameters of soils (the electrical resistivity and the natural electrical potential) and their pedogenesis was advanced on the basis of the known classical laws of electromagnetism and the general theory of pedogenesis. It was shown that the electrical parameters of soils primarily depend on the density of the mobile electric charges, which include cations of the soil exchange complex and ions of the soil solution. Model notions were developed to explain the laws of the changes in the electrical parameters in the main genetic soil types for the catenary and zonal levels of the soil cover organization.
TL;DR: In this article, the Oao-BHFao-M profile was used to classify petrozems with O-M profiles into three groups: (1) petroZems with the O-m profile, (2) podzols and podzolized podburs on the substrates with an admixture of morainic derivatives of acid rocks, and (3) shallow (<5-10 cm) pebbly soils on the substrate without an admixtures of allochthonous material (the rarest variant).
Abstract: Soil formation on hard rocks—nepheline syenite, amphibolite, metamorphized gabbro diabase, and their derivatives—was studied in the mountainous tundra and in the northern and middle taiga zones of the Kola Peninsula and Karelia (in the Kivach Reserve). It was found that the soils developing from these rocks could be classified into three groups: (1) petrozems with the O-M profile (the most common variant), (2) podzols and podzolized podburs on the substrates with an admixture of morainic derivatives of acid rocks, and (3) shallow (<5–10 cm) pebbly soils on the substrates without an admixture of allochthonous material (the rarest variant). In soils of the third group, the pedogenic alteration of the mineral matrix does not result in the appearance of phyllosilicates in the fine fractions if these phyllosilicates are initially absent in the rock. In these soils, the protion of the organic matter, and binding of iron released from the weathered silicate minerals into iron-organic complexes) are virtually undifferentiated by the separate soil horizons because of the very low thickness of the soil profiles. These soils have the Oao-BHFao-M profile; it is suggested that they can be classified as leptic podburs. An admixture of morainic material containing phyllosilicate minerals favors a more pronounced differentiation of the modern pedogenic processes by separate soil horizons even in the case of shallow soil profiles; the intense transformation of phyllosilicates takes place in the soils.
TL;DR: In most cases, fluorine, boron, selenium, and arsenic pollution deteriorates the ecological-biological properties of ordinary chernozems: the number of saprotrophic bacteria (especially those of the Azotobacter genus) that of fungi, and the enzymatic activity decreases, while the phytotoxicity becomes higher as discussed by the authors.
Abstract: In most cases, fluorine, boron, selenium, and arsenic pollution deteriorates the ecological-biological properties of ordinary chernozems: the number of saprotrophic bacteria (especially those of the Azotobacter genus) that of fungi, and the enzymatic activity decreases, while the phytotoxicity becomes higher, etc. The consequences of this pollution are related to the nature of the element, its concentration in the soil, the chemical form of the compound, and the time period from the moment of pollution. The elements studied form the following sequences according to their effect on the properties of an ordinary chernozem: B > Se > As > F (when the maximum permissible concentration (MPS) of these elements was accepted as the unit of measure) and Se > As > B > F (when the units of measurement were mg/kg or mmol/kg of soil).
TL;DR: Paleosols buried under kurgans of the Bronze (end of the fourth and the third millennia BC), Early Iron (1st-3rd centuries AD), and Medieval (13th century AD) epochs have been studied on the Ilovlya River (a tributary of the Don River) terrace.
Abstract: Paleosols buried under kurgans of the Bronze (end of the fourth and the third millennia BC), Early Iron (1st–3rd centuries AD), and Medieval (13th century AD) epochs have been studied on the Ilovlya River (a tributary of the Don River) terrace. The evolution of chestnut soils in the south of the Privolzhskaya Upland during the last 5000 years has been traced. It is shown that the mean weighted contents and distribution of soluble salts, gypsum, and carbonates in the soil profiles have been subjected to cyclic changes. The total microbial biomass and its trophic structure in the A1, B1, and B2k horizons of paleosols of different ages have been determined. A comparative analysis of the morphological, chemical, and microbiological data on the paleosols of different ages has been used to reconstruct the climatic dynamics for the last 50 centuries. The aridity of the climate in the studied region increased at the end of the third-the beginning of the second millennia BC and in the second and third centuries AD. The humidization of the climate took place in the 1st and in the 12th–13th centuries AD.
TL;DR: Salting out is recommended as a fast, simple, and cheap alternative to chromatographic methods for preparative separation of humic acids if large amounts of functionally different fractions need to be obtained as discussed by the authors.
Abstract: Humic acids (HAs) represent heterogeneous and polydisperse mixture of molecules that differ in their chemical structure, composition, and functional properties. Fractionation of HAs is of key importance for understanding their interactions with various organic and inorganic compounds, for studying their physiological activity, and for predicting their behavior in natural environments and agroecosystems. Existing fractionation methods are rather laborious and time consuming, which limits their application in fundamental science and industry. It is shown that fractionation of humic acids with ammonium sulfate ensures their preparative separation with respect to (a) hydrophobicity, (b) molecular size, and (c) charge dependent on the amount of functional groups. Salting out at the lowest and highest degrees of saturation with ammonium sulfate, upon which precipitation of the molecules occurs, makes it possible to separate humic acids into functionally different high-molecular-weight/hydrophobic and low-molecular-weight/hydrophilic fractions. The first fraction is characterized by a lower electrophoretic mobility than the second fraction. The weight percentage of the components coagulated at the lowest degree of salt saturation can be used as a quantitative parameter for comparing hydrophobic properties of humic acids. Salting out is recommended as a fast, simple, and cheap alternative to chromatographic methods for preparative separation of humic acids if large amounts of functionally different fractions need to be obtained.
TL;DR: In this paper, the composition and fabric of the upper permafrost layer and its relationship with permfrost-affected soils developing from the loamy substrates on the interfluves within coastal lowlands of northern Yakutia are considered.
Abstract: The composition and fabric of the upper permafrost layer and its relationships with the permafrost-affected soils developing from the loamy substrates on the interfluves within coastal lowlands of northern Yakutia are considered The studied area is characterized by the maximum activity of cryogenic processes and a shallow depth of seasonal thawing The permafrost layer affected by the maximum thawing during the Holocene has a specific morphology attesting to the impact of soil processes on it In general, the modern soil profile and the underlying permafrost layer can be distinguished as the soil-permafrost complex It is subdivided into the soil profile, the transient layer, and the intermediate layer The morphology and properties of the transient layer depend on the character of the soil horizons above the permafrost table The lateral migration of raw organic substances takes place above the permafrost surface between the particular elements of the cryogenic soil complexes; this material tends to accumulate within the transient layer
TL;DR: In this paper, the structural-functional significance of the shape and orientation of soil porosity is demonstrated by the example of agrogray and alluvial soils of the forest-steppe zone.
Abstract: Modern concepts of the morphology and geometry of soil structure are discussed. It is shown that the geometry of soil pores can serve as an indispensable indicator of the structural state of soils. The structural-functional significance of the shape and orientation of soil pores in addition to the total soil porosity is demonstrated by the example of agrogray and alluvial soils of the forest-steppe zone. Theoretical concepts and factual materials discussed in this paper can be considered the first stage of formalization of existing notions about the geometrical aspects of soil structure in the context of the systems arrangement of soils.
TL;DR: In this article, Angiospermae (deciduous arborous and herbaceous plants) were found to take part in the formation of humus in agro-gray soils.
Abstract: Tissues of Angiospermae (deciduous arborous and herbaceous plants) were found to take part in the formation of humus in the agrogray soils. The proportions of lignic phenol contents between the soils did not change neither upon their plowing, no their drainage. Within the catenas studied, the maximal accumulation of phenol compounds takes place in the soils of the mesodepressions with long-term reduction conditions and in the soils of the microdepressions with spring perched water on two levels. In the Fe-Mn nodules of the agrogray soils, lignin of higher plants was found. Its fractional composition was correlated with the predominant vegetation. With the increasing size of the nodules, the amount of products of lignin oxidation in the nodules decreased due to its mineralization. Drainage caused a deep transformation of lignin in the Fe-Mn nodules, especially in the coarse fractions of concretions. The mineralization of lignin aromatic compounds under aerobic conditions was accompanied by the significant increase in the share of phenol acids.
TL;DR: The analysis of spatial sequences of genetic horizons as elementary constituents of soil profiles in relation to the factors of soil formation makes it possible to draw several new conclusions about the geneses and geography of soils in the north of the Russian and West Siberian plains.
Abstract: The analysis of spatial sequences of genetic horizons as elementary constituents of soil profiles in relation to the factors of soil formation makes it possible to draw several new conclusions about the geneses and geography of soils in the north of the Russian and West Siberian plains. An important role in the spatial diversity of automorphic soils of these territories belongs to the texture of the parent materials and to the stratification of the latter within the soil profiles. The study of spatial soil sequences with due respect for the character of the parent materials suggests that the popular notion about the ideal bioclimatic zonality of the soils within these vast plains should be refined. It is shown that this notion is grounded in the phenomenon of good agreement between the bioclimatic zonality and the sedimentation zonality (or, according to I.A. Sokolov, the striated pattern of different types of sediments) in the studied territory. In turn, the sedimentation zonality was shaped by the directed movements of Quaternary glaciers over the plains from the north, northwest, or northeast.
TL;DR: In this paper, a decrease in the depth of organic surface horizons (forest litters and steppe mats), the reserves of organic matter in them, and an increase in their renewal rate were noted for virgin and fallow soils when going from the southern taiga to the dry steppe zone.
Abstract: A decrease in the depth of organic surface horizons (forest litters and steppe mats), the reserves of organic matter in them, and an increase in their renewal rate were noted for virgin and fallow soils when going from the southern taiga to the dry steppe zone. Zonal changes in the content and reserve of easily decomposable soil organic matter showed a similar tendency: these parameters regularly decreased from soddy-podzolic soils of the southern taiga to chestnut and light chestnut soils of the dry steppe. An exception from this series is provided by fallow chernozems of the steppe zone noted for the lowest content and reserve of labile organic matter in the series of soils studied. Similar, although less pronounced, tendencies were observed for the arable soils.