Vol 52, No 8 (2019)

On the basis of the review of available literature sources, the approaches to the systematics of peat soils in different soil classifications systems (Russian, German, FAO-UNESCO, WRB, and Soil Taxonomy) are discussed and compared with the landscape-based classifications of boreal mires. Among the diagnostic criteria, the most important in the systematics of peat soils and peatlands are the peat thickness, trophic status as the availability of nutrients and as a botanical concept, and acidity (pH) of peat and peat waters. The following suggestions are made: (a) to establish the peat thickness ≥30 cm as a criterion for peat soils, (b) to exclude the contents of nutrients in the peat from the diagnostic scheme for peat soils, and (c) to develop this scheme on the basis of geobotanical indicators. The latter may include active peat-forming plants, as well as plant species settling on the regressive mires under conditions of a cessation or drastic slowdown of peat accumulation. It is also recommended that the type of mesotrophic peat soils should be added to the Russian soil classification system and that the subtype of wet regressive soils should be distinguished within the oligotrophic type of peat soils along with the existing subtype of destructive soils.

Humic acids (HAs) make up to 30–50% of the soil organic matter, which is the main reservoir of organic carbon in the biosphere. The common isolation protocol for HAs implies alkaline extraction from soils followed by acidification of the extract with HCl to pH 2. International Humic Substances Society (IHSS) recommends isolation of HAs in oxygen-free atmosphere (e.g., under nitrogen or inert gas purging) to prevent oxidative transformations of HAs during the extraction process. In the Russian school of soil science, extraction is usually conducted without the use of nitrogen. In the present work, we compared the physicochemical properties of HAs isolated from A1 horizons of soddy-podzolic soil (Retisol) and chernozem (Chernozem) by 0.1 M NaOH in the presence and absence of oxygen. The soils used in this study represented zonal types of southern taiga and steppe, respectively, and differed markedly with respect to humus formation conditions. The yield of humic substances (C_org content in the extracts), their elemental composition, functional groups content, molecular-weight distributions (gel filtration on Sephadex G-75), paramagnetic properties, and absorption spectra in the visible, UV, and IR regions were studied. For both soils, no statistically significant differences were found in the quantitative yield, molecular weight distribution, absorption spectra in the visible, UV and IR regions between HAs isolated by alkaline extraction in the presence and absence of oxygen. At the same time, for the HAs extracted from the Retisol soil in the presence of oxygen, higher O : C ratios, higher contents of quinone and carboxyl groups, and significantly higher content of free radicals were observed. This was revealed with the use of elemental analysis, potentiometric titration, ¹H and ¹³C NMR spectroscopy, and electron paramagnetic resonance spectroscopy. For the Chernozem HAs, these differences were not observed. The obtained results suggest that partial oxidation of the soil organic matter components takes place during alkaline extraction from the Retisol in the presence of oxygen. In the Chernozem, humification process is apparently accompanied by significant oxidative transformation of organic residues, so the presence of molecular oxygen does not cause further oxidation of HAs under alkaline conditions. Our results indicate that, for the isolation of HAs from the mineral horizons of Chernozems, the use of oxygen-free atmosphere is optional. In the case of Retisols, the use of oxygen-free atmosphere is desirable, especially if it is intended to study the reactions of HA oxidation upon, for example, enzymatic catalysis.

Granite is an important soil-forming rock and is widely distributed in the cold-temperate forest area of northeast China, such as northern Greater Hinggan, where its biochemical weathering plays an important role in the formation of local soils. Due to the special latitude and elevation, lichen plays a crucial role in the biochemical weathering of granite here, of which the role of low molecular organic acids (short for organic acids) is of interest. We simulated the concentrations of oxalic acid (OA) and succinic acid (SA) in the local lichens of Northeast China, applied OA or SA (10, 20, 30, 40, and 50 mmol L^–1) to granite powders for 1 (10 min), 10, 20, 30, 40, 50, or 60 days, and studied the effects of organic acids on the bio-weathering process of granite, such as the dissolution regularity of various ions and the morphological changes of rock surfaces. OA and SA both induced the weathering and dissolving of granite, significantly promoted the release of Na⁺, K⁺, Al³⁺, Fe³⁺, Mg²⁺, Mn²⁺, Ca²⁺, and \({\text{SiO}}_{3}^{{2 - }}\) from granite powders. For the ion dissolution, the effect of OA was stronger than that of SA. Infrared analysis showed that both organic acids did not change the structures of their own groups, and the weathering mechanism was mainly the complexation of organic acids. The results of electron microscopy also presented the dissolution of granite powders by organic acids, and the effects were enhanced as the treatment time increased. After organic acid applications, the concentrations of dissolved ions from the granite powder varied with the type and concentration of organic acids, and treatment time. The concentration of each ion usually reached its maximum at 50 or 40 mmol L^–1 OA, and 50 mmol L^–1 SA (except for Fe³⁺ of some treatments). At day 1, the concentrations of \({\text{SiO}}_{3}^{{2 - }}\), Al³⁺, Fe³⁺, and Mn²⁺ treated with OA were higher than those of other times. Compared with SA, OA could dissolve more ions from granite powders, especially at day 1. However, the metal ions dissolved by OA were easy to complex with OA, so the concentrations of ions treated by SA were higher than those of OA, and the ions dissolved by OA would enter into the soils more frequently in OA–metal complexes.

Traditional techniques and methods for evaluation and detection of soil samples are tedious, laborious, expensive, and time-consuming. In comparison, spectroscopic techniques have successfully overcome some of these disadvantages and can supplement or replace them. As soil is a complex media, it is difficult to assign specifically spectral features for physicochemical properties of soil. This study discusses the combined application of Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR), and Scanning Electron Microscopy coupled to EDX microprobe (SEM/EDX) methods for estimating soil physicochemical properties. For this purpose, 30 topsoil samples were measured according to standard methods of soil analysis. All spectra were collected in the mid-infrared (MIR) from 4000 to 650 cm^-1. Chemometric methods were used in the analysis of multivariate data using the Quant2 package in OPUS 7 software and improved the prediction of soil properties using partial least squares regression (PLSR). The results showed that specific surface area (SSA MB-titration) had the best predictions for the soil properties in ATR-FTIR study with a RPD of 2.08, RMSE of 13.50 m² g^–1, and R² of 0.77 (very good); followed by cation exchange capacity, organic carbon, SSA (BET), Al, clay, and Ca (good); saturation, sand, silt/clay, electrical conductivity, saturated hydraulic conductivity, K, silt, Fe, C, and Si (fair); O, Mg, pH, bulk density, porosity, total pore volume, and particle density (poor). Also, we found that SEM-EDX is able to perform a rapid simultaneous multielement analysis without any special soil sample preparation. Consequently, modern techniques, such as ATR-FTIR and SEM-EDX can be used for such studies according to the information needed and the time required for the sample preparation.

Noneroded and eroded chernozems in the southeast of Western Siberia are characterized by the great moisture deficit at the beginning of the winter season. By the end of the cold period, water reserves in the snow are sufficient to compensate for this deficit. However, snowmelt saturates only the upper 50 cm of the soil profiles. After the snowmelt season, soil moisture storage in the layers of 50–100 and 100–150 cm is equal to the pre-winter storage; in some years, it is even lower. The impermeable ice layer in the soil prevents full absorption of the snowmelt. The analysis of 80-year-long data on winter precipitation in three major geomorphic areas of the southeast of Western Siberia (Novosibirsk Ob region, Cis-Salair region, and Kuznetsk Depression) made it possible to distinguish between four climatic cycles—low-snow (1938–1962), normal snow (1963–1988), high-snow (1988–2012), and the current very high-snow (since 2013)—in all these regions.

We developed a novel method using image analysis to quantify the content and shape characteristics of coarse fragments in an Alfisol developed from loess over outwash. A total of 45 soil samples (about 600–1000 g each) were collected at 10-cm depth interval from 0 to 150-cm deep at three transects in the profile. The coarse fragments were separated from the soil fine-earth particles and photographed in the laboratory. The images were processed using ImageJ processing software that provides total count, total area, and mean circularity of each sample, as well as shape characteristics (circularity, aspect ratio, roundness, and solidity) of each coarse fragment. The amount of coarse fragments (coarse fragments, total count/mass, and total area/mass) varied with depth and was highest in the 2C1 and BC horizons where the soil was developed from coarse glacial outwash and a mixing of coarse outwash and loess. The coarse fragments content was lower in the loess and fine glacial outwash horizons. Approximately 9.6% of coarse fragments in weight or 14.5% by count moved from the glacial outwash layer into the loess layer (Ap and Bt horizons). The shape characteristics showed large variations at 50–110 cm depth where the soil was developed from coarse glacial outwash and a mixing of coarse outwash and loess. The mean circularity, roundness, and solidity of the coarse fragments at the topsoil were larger than those at the 50-110 cm, indicating that rounder stones tend to move faster than irregularly shaped stones during the frost heaving. This method provides a robust, fast and quantitative way to estimate the distribution and the shape characteristics of coarse fragments in a soil sample that can be applied to help better understand soil formation.

In a model laboratory experiment on gray forest soil, the succession of microbial communities during the decomposition of proteins, lipids, and polysaccharides was studied. Proteins were mineralized during the first three months; active decomposition of lipids started two months after the beginning of the experiment. Differences in the functional diversity of microbial communities during the succession were revealed using the method of multisubstrate testing of respiration activity. Microbial respiratory responses to introduction of nitrogen-containing compounds (amino acids) were the highest in variants with decomposition of nitrogen-free compounds and low in protein variants. The ratio of respiratory responses of microbial communities to introduction of carboxylic acids to that of amino acids characterized the nitrogen supply in the soil. This parameter may be useful for reconstruction of initial presence of organic materials in various archaeological contexts.

Ecotoxicity of nanoparticles (50–100 nm) of Cu, Ni, and Zn has been assessed by changes in biological indicators of an ordinary chernozem (Haplic Chernozem (Loamic)) of Rostov-on-Don in the laboratory model experiment with incubation of soil samples with nanopowders of these elements added to soil in concentrations 100, 1000, and 10 000 mg/kg. The effects of biological indicators have been determined 10, 30, and 90 days after soil contamination. The addition of Cu, Ni, and Zn nanoparticles led to a decrease of the total number of bacteria, abundance of Azotobacter bacteria, catalase and dehydrogenase activities, and germination and length of roots of radish sown. Reliable cases of hormesis were not detected. Nanoparticles of Cu and Zn showed higher toxicity than Ni nanoparticles, and this was inconsistent with the hypothesis, according to which the toxicity of nanoparticles depended only on their size and did not depend on chemical nature of the element. According to the integral indicator of biological state of soil, maximal toxicity of Cu, Ni, and Zn nanoparticles was observed on the 30th day after contamination.

Analytical data on the distribution of chemical elements with respect to soil combinations as area units of the inventory of the factors of the anthropogenic impact on the soil cover are presented. The identification of soil combinations in the Soligorsk mining region of Belarus is based on the analysis of the morphogenetic soil cover pattern and combines typological and topological approaches within the concept of adaptive landscape farming. The spatiotemporal changes in the parameters of anthropogenic soil salinization on agricultural lands are evaluated using geoinformation tools for data processing and modeling. The qualitative interpolation of agrochemical data over the areas under anthropogenic impact in the Soligorsk region is used as a spatial basis for optimizing land use in large agricultural enterprises. The selection of salt-tolerant crops as a measure to optimize the agricultural use of human-salinized soils and to reduce the ecological risks for the local population is discussed. It is recommended to cultivate sugar beet (Beta vulgaris), lucerne (Medicago), and perennial grasses (timothy (Phleum pretense), cocksfoot (Dactylis glomerata), and smooth bromegrass (Bromus inermis)) in the zone of the greatest anthropogenic impact.