Radiocarbon pollution and self-purification of humus in chernozems of the East-European plain in 1900–2008

The dynamics of the ¹⁴C content in the humus of chernozems in 1900?C2008 are considered. The elevated ¹⁴C content in the atmosphere because of nuclear weapons tests has led to the contamination of humus with bomb radiocarbon. In 1966?C1968, the ¹⁴C reserves in the profiles of chernozems exceeded the background ones by 15%; in 1978, by 12%; and, in 1998, by 2%. By the year of 2008, its reserves became equal to the background ones. The ¹⁴C distribution along the soil profiles changed. By 1978, the 0- to 30-cm-thick soil layer became free from radiocarbon due to its self-purification; however, at depths of 40?C70 and 100?C115 cm, its weak accumulation was registered. By 2008, the whole soil profile was free from ¹⁴C. The main mechanism of the soil self-purification from radiocarbon is suggested to be the constant substitution of fragments of humus compound structures for those of fresh organic matter entering the soils with the ¹⁴C content being in equilibrium with the atmospheric one, i.e., due to the renewal of the carbon in the humus. The rate of the carbon renewal and its migration in the soils are assed based on the ¹⁴C concentrations in the humus.     

Soils and the soil cover of the arkaim reserve (Steppe Zone of the Trans-Ural Region)

Soils of the Arkaim Reserve in the area around a unique settlement-fortress of the Bronze Age in Chelyabinsk oblast have been studied. These soils are generally typical of the entire Trans-Ural Plateau. The soil properties are characterized in detail on the basis of factual data on 170 soil pits and four soil catenas. The soil cover of the reserve is specified into six geomorphic groups: (a) denudational surfaces of the low mountains, (b) accumulative-denudational surfaces of the low mountains, (c) denudational-accumulative plain surfaces, (d) lacustrine-alluvial plain surfaces, (e) floodplain surfaces, and (f) slopes and bottoms of the local ravines and hollows. Chernozems occupy about 50% of the reserve; solonetzes and saline soils, 32%; meadow chernozems, 7%; and forest soils, 1%. The soils of the reserve are relatively thin; they have a distinct tonguing of the humus horizon and are often saline and solonetzic. The latter properties are inherited from the parent materials and are preserved in the soils for a long time under the conditions of a dry continental climate. The genetic features of the soils differ in dependence on the composition and age of the parent materials. With respect to the thickness of the soil profiles and the reserves of soil humus, the soils can be arranged into the following lithogenic sequence: the soils developed from the eluvium of igneous rocks-redeposited kaolin clay-montmorillonite-hydromica nonsaline and saline loams and clays. The content of C_org in the upper 20 cm varies from 2.5 to 5.6%, and the reserves of C_org in the layers of 0?C0.5 and 0?C1.0 m reach 57?C265 and 234?C375 t/ha, respectively. The soils of pastures subjected to overgrazing occupy two-thirds of the reserve. Their humus content is 10?C16% higher in comparison with that in the analogous plowed soils. Another characteristic feature of the humus in the soils of the pastures is its enrichment in the labile fraction (28?C40% of C_org).     

Concentrations of rare-earth elements in soils of the Prioksko-Terrasnyi state biospheric reserve

The concentrations of rare-earth elements were studied in the profiles of soddy podburs and mucky-humus gley soils. The soil horizons differed significantly in the contents of C_org (0?C26%), the physical clay (<0.01 mm) fraction (3?C31%), the acidity (pH 4 to 5.5), and the presence/absence of Al-Fe-humus accumulations. The most significant relationship was observed between the concentrations of rare-earth elements and the physical clay content, particularly for Nd: x(Nd, mg/kg) = 7 + 1.6y (fraction <0.01 mm, %). Weak biogenic accumulations in the upper horizons were observed for Nd, Ce, and Dy; Nd, Pr, and La accumulated in the Al-Fe-humus illuvial horizon. The concentrations of rare-earth elements in the studied soils formed the following sequence (mg/kg): Nd (20?C101)-Ce (10?C44)-La, Sm, Gd, Dy, Yb (3?C20)-Pr (1?C4)-Ho (0.1?C0.4)-Tm, Lu, and Tl (0.0). A clear trend was observed to higher contents of even-numbered elements as compared with odd-numbered elements, excluding La.     

Mathematical description of the dynamics of 12C and 14C in the soil humus

Mathematical tools that can be applied to analyze the dynamics of ¹⁴C and ¹²C isotopes in soil humus are discussed. A system of two differential equations is suggested to describe the dynamics of the ¹²C and the ¹⁴C/¹²C ratio (normalized to the NBS standard) with due account for the initial conditions and for the ¹⁴C dynamics in the atmosphere (in particular, the bomb effect). Possible analytical solutions to these equations and algorithms that can be used in the case when these solutions are absent are discussed. Routine problems of the assessment of the dates of soil burying and the coefficient of the humus mineralization on the basis of the experimentally determined ¹⁴C/¹²C ratios in the soil humus are considered with the use of published data. In particular, the specific features of the assessment of the parameters of these equations in the case of the insufficiency of the experimental data are analyzed.     

Features of the soil cover of the Vetluga-Unzhensk interfluvial area (Northeast of the Kostroma oblast)

This paper reveals the features of the soil cover of the territory of the Vetluga-Unzhensk interfluvial area, which is adjacent to the northern part of Uvaly, where contrasting combinations of alpha-humic and organo-accumulative soils are widespread. This is due to abruption of the clayey rocks of the Triassic age on the background of fluvioglacial sand sediments of the Dnieper glaciation, which is due to the complicated history of the formation of the relief of the characterized territory.     

Stimulation of the activity of microorganisms by humin preparations in oil-polluted soils

The influence of humin preparations obtained from low-moor peat by the mechanochemical method on the changes in the microflora number and hydrocarbon composition in oil-polluted soils was studied. The intense growth of the microorganisms in number especially in the oil-polluted soil was observed upon the application of humin acids (at a concentration of 0.005 wt %) extracted from mechanically processed peat. In this case, the content of the extracted bitumoids decreased down to 40 wt %. The soil microflora stimulated by the humin preparations was shown to have highly destructive oil-oxidizing activity reflected in the indices of the hydrocarbon biodegradation. The mechanochemical activation of peat allows raising the efficiency of extracting the humic acids and can be a reason for increasing the availability of their individual components and parts of molecules, including micro- and macroelements that are used by microbial cells as sources of nutrition and energy.     

Trends of the natural evolution of chernozems on the East European Plain

A generalized chronosequence of changes in the morphometric parameters of chernozems in the past 5100 years is analyzed. It is shown that the development of chernozems in the center of the East European Plain is characterized by both long-term (interglacial, encompassing the entire Holocene) and short-term (within separate climatic periods of the Holocene) trends. The long-term trend of the evolution of ordinary chernozems developed from the loess-like calcareous loam consists of a continuous increase in the thickness of the soil humus profile and an oscillating increase in the depth of the carbonate accumulations. The Late-Holocene short-term trends of the natural evolution of chernozems are characterized by the high spatial heterogeneity related to the patterns of climatic fluctuations and to the lithological composition of parent materials. In that period, the thickness of genetic horizons in the forest-steppe chernozems was increasing faster than that in the steppe chernozems.     

Mercury in humus horizons of soils in the Transbaikal region

The total mercury content has been determined in gray forest soils, chernozems, chestnut soils, and in different parent materials in the Transbaikal region. The mercury content is below the clarke value in the intrusive, effusive, and alluvial soil-forming rocks (0.004–0.024 mg/kg). In the humus horizons of the soils, it reaches 0.011–0.026 mg/kg, which is higher than the clarke value for the pedosphere. The mean background content of mercury in the soils of the Transbaikal region is 0.018 mg/kg. No significant positive correlation between the mercury content and the humus content of the soils has been revealed.     

Effect of chemical agents on ground beetles in field crops

The characteristics of the formation of a ground beetle community in winter rye, spring wheat, spring rape, and oat agrocenoses under conditions of the forest-steppe in the Ob River Region have been studied. It has been established that the use of the chemical agents specified by the technology of growing these crops does not substantially change the carabid community inhibiting the agrocenoses.