S. A. Shoba

Soil-geographical database of Russia.

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.

Current ideas on the possible pathways for the formation of humic substances in soils

In the current approach to the study of humic substances (HSs), they are usually considered as complex chemical polymeric compounds with a specific combination of properties. This concept of HSs cannot explain their role in soils as a depot of nutrients for microorganisms and some experimental data. The main problem is related to the low energy efficiency of this depot of nutrients, because microorganisms have to consume energy for synthesizing enzymes that destroy HS polymers (macromolecules). At the same time, the recently proposed consideration of HSs as a system of supramolecular compounds completely eliminates this contradiction. In this work, an attempt has been made to consider HSs from other positions based on their possible functional role in soils and entire ecosystems. A scheme has been proposed for the transformation of the litterfall that is based on the supramolecular nature of the HSs and confirmed by reported experimental results.

Submicromorphology of soil magnetic fractions

The spatial and vertical distribution patterns of ferromagnetic particles in soddy-podzolic and chernozemic soils subjected to technogenic loads have been studied. A classification of soil magnetic particles according to their morphological features is suggested. It takes into account the shape and the character of the particles’ surface, which are specified by the genesis of the particles, and may be used for diagnostic purposes.

Biogeochemistry of Carbon, Iron, and Heavy Metals in Wetlands (Analytical Review)

Microorganisms and higher plants play an important role in the processes of mobilization and immobilization of nutrients and toxicants in water-logged soils. Their role is especially significant in the behavior of redox-sensitive elements: carbon, iron, and heavy elements (Cr, U, and As). Organic carbon in hydromorphic soils takes part in the reduction of Fe(III) and other elements with variable valency. Iron oxides sorb many heavy metals; the microbial reduction of iron oxides influences their mobility. The mobility of arsenic, which is a siderophilic element, increases as a result of the reduction of iron oxides and hydroxides after a decrease in reduction potential. Chromium and uranium compounds in wetlands are precipitated, but their mobility can increase with the reduction of iron oxides and hydroxides.

The formation of magnetic ferric oxides in soils over underground gas storage reservoirs

The concepts of the specific mechanisms responsible for the formation of magnetic ferric oxides in soils over artificial gas storage reservoirs are considered for the first time. Upon the interaction of technogenic allochthonous methane with soil, some biogeochemical barriers are formed that are characterized by the accumulation of solid products resulting from the functioning and development of the soil. The pedogenic new formations are represented by fine magnetic ferric oxides of specific shape. They are the result of an elementary soil-forming process—oxidogenesis composed of a complex of microprocesses of biogenic and abiogenic nature.

Magnetic susceptibility as an indicator of heavy metal contamination of urban soils (Review)

Researchers have a particular interest in the assessment of magnetic susceptibility due to aerial contamination of soils by magnetite and heavy metals. The content of magnetite and other magnetic minerals in urban soils is tens and hundreds of times higher than their background values. The properties of technogenic magnetics are also different: whereas background soils are dominated by thin superparamagnetic and single-domain particles, large multidomain particles prevail in urban soils. Technogenic magnetics consist of micron-sized spherules. It has been proven that there is a correlation between magnetic susceptibility and the total content of heavy metals in soil. However, each city (or its district) has its own level, either positive or negative, which is determined by the nature of local contamination. Magnetic susceptibility maps have been created even for some countries (Poland, United Kingdom, etc.). Local surveys of urban areas, for example of a city or its vicinity, is of the greatest practical interest. Such maps reflect detailed contamination by heavy metals. Critical values of magnetic susceptibility above which soil is considered contaminated, differ between countries.

Ephemeral Fe(II)/Fe(III) layered double hydroxides in hydromorphic soils: A review

Ephemeral green rust is formed seasonally in some hydromorphic soils. It consists of Fe(II)/Fe(III) layered double hydroxides with different types of interlayer anions and different oxidation degrees of iron (x). In synthetized stoichiometric green rust, x = 0.25–0.33; in soil fougerite, it may reach 0.50–0.66. The mineral stability is provided by the partial substitution of Mg2+ for Fe2+. The ephemeral properties of the green rust are manifested in the high sensitivity to the varying redox regime in hydromorphic soils. Green rust disappears during oxidation stages, which complicates its diagnostics in soils. For green rust formation, excessively moist mineral soil needs organic matter as a source of energy for the vital activity of iron-reducing bacteria. In a gleyed Cambisol France, where fougerite is formed in the winter, the index of hydrogen partial pressure rH2 is 7.0–8.2, which corresponds to highly reducing conditions; upon the development of oxidation, fougerite is transformed into lepidocrocite. In the mineral siderite horizon of peatbogs in Belarus, where green rust is formed in the summer, rH2 is 11–14, which corresponds to the lower boundary of reducing conditions (rH2 = 10–18); magnetite is formed in these soils in the winter season upon dehydration of the soil mass.

Iron compounds in sulfate-carbonate soils on red-colored Cambrian rocks in the southern Angara region

In some regions of Irkutsk oblast in the southern Angara region, brown carbonate-sulfate soils have been formed on red-colored Cambrian rocks. In the automorphic soils, even a low content of hematite strongly affects the soil color, and the increase in its content only slightly enhances the red color of the soil. The brown color of carbonate soil is due to the partial preservation of lithogenic hematite in the upper part of the soil profile. The abundant gypsum “preserves” the lithogenic hematite in the carbonate-sulfate soil; the oxidation of iron is also hampered in this soil. Important changes occur in the wetted dark solonchak: lithogenic hematite is dissolved, the structure of iron chlorite loses order, and coarse and crystallized magnetite is formed in the humus horizon.

Ferrihydrite in soils

Ferrihydrite—an ephemeral mineral—is the most active Fe-hydroxide in soils. According to modern data, the ferrihydrite structure contains tetrahedral lattice in addition to the main octahedral lattice, with 10–20% of Fe being concentrated in the former. The presence of Fe tetrahedrons influences the surface properties of this mineral. The chemical composition of ferrihydrite samples depends largely on the size of lattice domains ranging from 2 to 6 nm. Chemically pure ferrihydrite rarely occurs in the soil; it usually contains oxyanion (SiO144-, PO43-) and cation (Al3+) admixtures. Aluminum replace Fe3+ in the structure with a decrease in the mineral particle size. Oxyanions slow down polymerization of Fe3+ aquahydroxomonomers due to the films at the surface of mineral nanoparticles. Si- and Al-ferrihydrites are more resistant to the reductive dissolution than the chemically pure ferrihydrite. In addition, natural ferrihydrite contains organic substance that decreases the grain size of the mineral. External organic ligands favor ferrihydrite dissolution. In the European part of Russia, ferrihydrite is more widespread in the forest soils than in the steppe soils. Poorly crystallized nanoparticles of ferrihydrite adsorb different cations (Zn, Cu) and anions (phosphate, uranyl, arsenate) to immobilize them in soils; therefore, ferrihydrite nanoparticles play a significant role in the biogeochemical cycle of iron and other elements.

Technologies and standards in the information systems of the soil-geographic database of Russia

The achievements, problems, and challenges of the modern stage of the development of the Soil-Geographic Database of Russia (SGDBR) and the history of this project are outlined. The structure of the information system of the SGDBR as an internet-based resource to collect data on soil profiles and to integrate the geographic and attribute databases on the same platform is described. The pilot project in Rostov oblast illustrates the inclusion of regional information in the SGDBR and its application for solving practical problems. For the first time in Russia, the GeoRSS standard based on the structured hypertext representation of the geographic and attribute information has been applied in the state system for the agromonitoring of agricultural lands in Rostov oblast and information exchange through the internet.