Search Results (19)

The degradation of modern and ancient permafrost-affected soils and organic-rich sediments and the release of relict soil organic matter from the frozen state are critical for understanding the global carbon cycle in a changing climate. The molecular structure of humic acids isolated from modern Cryosols and paleosoils from the Ice Complex deposits in the Batagay megaslump area was investigated. The elemental composition analysis was performed using a CHN analyzer, and molecular composition analysis was determined by CP/MAS ¹³C-NMR spectroscopy. Analysis of the molecular structure of humic acids showed that MIS 5e paleosoils are characterized by a relatively high content of aliphatic structural fragments (C,H-AL—29–36%) and a low content of aromatic structural fragments (AR/AL—0.49–0.43), which reveals low humification rates in this time period. The composition of humic acids from MIS 7 paleosoils shows a relatively high content of aromatic structural fragments compared to modern soils (AR/AL—0.47) and MIS 5e deposits (AR/AL—0.67–0.54), indicating a longer humification process in heterogenic conditions (warm and cold periods). The results indicate that the molecular structure of humic acids is a dynamic parameter of the environment that reflects the local conditions of pedogenesis and organic matter formation. Permafrost thawing leads to the release of organic matter (including matter that is relatively weakly resistant to biodegradation where aliphatic structural fragments dominate the composition of humic acids) that may strengthen the emission of climate-active gases into the atmosphere and boost climate change. Full article

The importance of research to assess the impact of potentially toxic trace elements (PTEs) on the environment and the importance of environmental monitoring, taking into account the natural variability of soil properties, shaped the aim of our study: to determine the background concentrations of PTEs in different soil profiles in the European Northeast, specifically in the Republic of Komi in Russia, taking into account the landscape and geochemical characteristics of the area. We analysed 173 soil samples from five main soil subtypes. The acid soluble forms of PTEs (Cu, Pb, Zn, Ni, Cd and Mn) were measured using an atomic emission spectrometer. We developed a database of PTE contents and created distribution maps for the Komi Republic using GIS technologies. The study found that PTE levels in soils from accumulative landscapes (such as depressions and floodplains) were generally higher than those in soils from eluvial landscapes (interfluves). We identified correlations between the levels of different PTEs and certain soil properties, providing insights into the biogeochemical migration patterns of these elements. The differentiation of PTEs in soil profiles was more pronounced in loamy automorphic soils and less so in sandy semi-hydromorphic and hydromorphic soils. Most soils, except floodplain soils, showed a clear eluvial–illuvial pattern of PTE distribution within the mineral soil profile, whereas floodplain soils showed a more uniform PTE distribution. The results of this study are useful for assessing the contamination levels of these soil types in high-latitude regions. Full article

Permafrost-affected regions in the Russian Arctic are a critical study area for studying the sources of metal elements (MEs) in soils originating from geological/pedogenic processes or from anthropogenic sources via atmospheric transport. In the Nadym region of the Yamalo-Nenets Autonomous District, we investigated the contents of soil organic carbon (SOC), total nitrogen (TN), and MEs across different soil types and horizons, explored the source apportionment of MEs, and assessed local ecological risks of potentially toxic elements (PTEs). The results showed that (1) the contents of SOC and TN in Histic Cryosols (8.59% and 0.27%) were significantly higher than in Plaggic Podzols (Arenic, Gelic, and Turbic) (2.28% and 0.15%) and in Ekranic Technosols (Umbric) (1.32% and 0.09%); (2) the concentrations of MEs in the Nadym region were lower than in other Arctic regions; (3) the primary sources of MEs were identified as geological processes (36%), atmospheric transport (23%), agricultural activities (21%), and transportation (20%); and (4) the permafrost-affected soils in the Nadym region exhibited low ecological risks from PTEs. These results underscore the critical role of geological and anthropogenic factors in shaping soil conditions and highlight the relatively low ecological risk from PTEs, providing a valuable benchmark for future environmental assessments and policy development in Yamal permafrost regions. Full article

In the framework of the implementation of the all-Russian climatic project “Carbon measurement test sites”, reference soils of “Seven Larches” carbon supersite, which is a benchmark and the only monitoring site in the Artistic latitudes, were investigated. The morphological structure of representative soils was specified, and it was found that soils are classified as Cryosols of different types (Histic, Stagnic or Gleyic). The basic physico-chemical characteristics of the soils were studied. By means of elemental analysis and ¹³C NMR spectroscopy, the composition and molecular structure of humic acids from organic and mineral soil horizons were studied. The surface (organic) soil horizons are characterized by high values of H:C molar ratios (1.2–1.3), which indicates a lower degree of the molecular structure aromaticity of humic acids from organic soil horizons. Analysis of the molecular structure of humic acids by ¹³C NMR spectroscopy showed that humic acids of the studied soils are characterized by the predominance of non-substituted aliphatic (0–47 ppm) and aromatic (108–164 ppm) fragments. Mineral soil horizons are characterized by higher stabilization of organic matter (with lower SOC content—0.5–0.9%) and higher hydrophobicity of humic acid molecules. Comparison of the obtained results with previously published data on the structural and elemental composition of humic acids isolated from soils of similar genesis and geographical location did not reveal any significant differences between the data obtained by us and previously published data. Thus, for “Seven Larches” carbon supersite “reference” parameters of elemental composition of humic acids, their molecular composition and degree of stabilization of soil organic matter were identified. Full article

The transition of soils into fallow state has a significant impact on the accumulation and transformation of soil organic matter (SOM). However, the issue of SOM transformation as a result of soil transition to fallow state in cryolithozone conditions is insufficiently studied. The aim of this study is to investigate the molecular weight (MW) distribution of humic acids (HAs) isolated from soils of central Yakutia. Native, fallow and agricultural soils in the vicinity of Yakutsk city were studied. MW distributions of HA preparations were obtained on an AKTAbasic 10 UPS chromatographic system (Amersam Biosciences, Uppsala, Sweden) using a SuperdexTM 200 10/300 GL column (with cross-linked dextran gel, fractionation range for globular proteins 10–600 kDa). The data on the molecular-mass distribution of HAs of fallow and agricultural soils of Central Yakutia were obtained for the first time. According to the obtained data, it was found that the highest carbon content in the structure of HAs was observed in agricultural soils (52.56%), and is associated with soil cultivation and fertilizer application. Among the HAs of fallow soils, we note that those soils that are in the process of self-vegetation have a relatively high carbon content in the HAs (45.84%), but the highest content was observed in fallow soils used as hayfields (49.98%), indicating that the reinvolvement of agriculture in fallow soils leads to an increase in the carbon content of HAs. According to the data of the MW distribution of HAs, it was found that the highest content of a high MW fraction of HAs was recorded in native soil (18.8%); this is due to the early stages of humification and the low maturity of organic matter. The highest content of a low MW fraction of HAs was recorded in agricultural soil (73.3%); this is due to the formation of molecular complexes of a “secondary” nature, which are more stable in the environment than the primary transformation products of humification precursors. The molecular composition of the HAs of fallow soils in the process of self-overgrowing is characterized by values closer to the HAs of native soils, which indicates their transformation towards HAs of native soils. The obtained results indicate that the reinvolvement of fallow soils leads to the transformation of the molecular composition of HAs towards HAs of agricultural soils, and to an increase in the resistance of SOM to biodegradation. Full article

The scavenging of atmospheric trace gases has been recognized as one of the lifestyle-defining capabilities of microorganisms in terrestrial polar ecosystems. Several metagenome-assembled genomes of as-yet-uncultivated methanotrophic bacteria, which consume atmospheric CH₄ in these ecosystems, have been retrieved in cultivation-independent studies. In this study, we isolated and characterized a representative of these methanotrophs, strain D3K7, from a subarctic soil of northern Russia. Strain D3K7 grows on methane and methanol in a wide range of temperatures, between 5 and 30 °C. Weak growth was also observed on acetate. The presence of acetate in the culture medium stimulated growth at low CH₄ concentrations (~100 p.p.m.v.). The finished genome sequence of strain D3K7 is 4.15 Mb in size and contains about 3700 protein-encoding genes. According to the result of phylogenomic analysis, this bacterium forms a common clade with metagenome-assembled genomes obtained from the active layer of a permafrost thaw gradient in Stordalen Mire, Abisco, Sweden, and the mineral cryosol at Axel Heiberg Island in the Canadian High Arctic. This clade occupies a phylogenetic position in between characterized Methylocapsa methanotrophs and representatives of the as-yet-uncultivated upland soil cluster alpha (USCα). As shown by the global distribution analysis, D3K7-like methanotrophs are not restricted to polar habitats but inhabit peatlands and soils of various climatic zones. Full article

The landscapes in the discontinuous permafrost area of Western Siberia are unique objects for assessing the direct and indirect impact of permafrost on greenhouse gas fluxes. The aim of this study was to identify the influence of permafrost on the CO₂ emission at the landscape and local levels. The CO₂ emission from the soil surface with the removed vegetation cover was measured by the closed chamber method, with simultaneous measurements of topsoil temperature and moisture and thawing depth in forest, palsa, and bog ecosystems in August 2022. The CO₂ emissions from the soils of the forest ecosystems averaged 485 mg CO₂ m⁻² h⁻¹ and was 3–3.5 times higher than those from the peat soils of the palsa mound and adjacent bog (on average, 150 mg CO₂ m⁻² h⁻¹). The high CO₂ emission in the forest was due to the mild soil temperature regime, high root biomass, and good water–air permeability of soils in the absence of permafrost. A considerable warming of bog soils, and the redistribution of CO₂ between the elevated palsa and the bog depression with water flows above the permafrost table, equalized the values of CO₂ emissions from the palsa and bog soils. Soil moisture was a significant factor of the spatial variability in the CO₂ emission at all levels. The temperature affected the CO₂ emission only at the sites with a shallow thawing depth. Full article

The soils of cold regions store up to 60% of all organic carbon on the planet. As a result of climate change, this organic matter can be biodegraded by microorganisms and thereby make an additional contribution to carbon balance. Nowadays, there are fragmentary data on organic C stocks in high-latitude soils and single works on the analysis of the quality of buried organic matter. This paper presents the first data on the molecular weight distributions of humic acids (HAs) extracted from soils and sediments in Yedoma. Molecular weight distributions of HAs preparations were obtained on an AKTAbasic 10 UPS chromatographic system (Amersham Biosciences, Sweden) using a SuperdexTM 200 10/300 GL column (with cross-linked dextran gel, fractionation range for globular proteins 10–600 kDa). As a result of the study, it was found that the buried soil horizons are characterized by the highest content of low molecular weight fraction (with molecular mass (Mr) 1.4–1.9 kDa and molar fraction in the range of 54.3–67.1%). The high molecular weight fraction is concentrated mainly in the superficial horizons and decreases with depth (with Mr 299–346 kDa and molar fraction in the range of 3.4–9.8%). In the Yedoma sediments, the maximum content of the medium-molecular fraction is observed (with Mr 24.6 kDa and 39.6% of the molar fraction), which may indicate a low rate of organic matter transformation in the permafrost. The data obtained serve as a database of analysis in terms of modeling the global carbon cycle in the cold regions of the planet. Full article

The formation of oxalates in soils and rocks under conditions of cryoarid climate, permafrost and taiga vegetation was studied. Whewellite and weddellite were found in four areas associated with the mining industry: on the kimberlite deposit of the Daldyn territory, in the lower reaches of the Markha River of the Central Yakut Plain, and on the coastal outcrop of the Allah-Yun Sellah-Khotun ore cluster. Whewellite was found in the upper organic horizon of Skeletic Cryosol (Thixotropic) (sample 151) and as a film on the surface of plant remains of Humic Fluvisols (sample 1663). Weddellite was found as an extensive encrustation on the surface of the soil and vegetation cover of Stagnic Cryosols Reductaquic (sample 984) and on a siltstone outcrop (sample KM-6-21). Calcium oxalates were identified by X-ray phase analysis, photographs of the samples were taken on a polarizing microscope, and the crystal morphology was studied on a scanning electron microscope. To determine the chemical composition of soils and rocks, the classical wet-chemical method was used; the physical properties of the studied samples were studied using a pH meter, the photoelectric colorimetric method, and a synchrotron thermal analysis device. The source of calcium for the formation of salts is the parent layers of the studied soils, represented by carbonate and carbonate clastic rocks, which cause neutral and slightly alkaline environments. High humidity, which is provided by the seasonal thawing of the permafrost, has a key role in the formation of the studied oxalates in Yakutia with a sharply continental cryoarid climate. Based on the studies, it was found that the first two samples are the products of lichen activity, and the third and fourth are at the stage of initial soil formation by micromycetes. In addition, the formation of these oxalates, in our opinion, is the result of the protective function of vegetation, in the first two cases, with a sharp increase in the load on lichens under technogenic impact, and in the second and third cases, when favorable conditions arise for initial soil formation, but under conditions of toxic content of heavy metals and arsenic. Full article

One quarter of the Northern hemisphere is underlain by permanently frozen ground, referred to as permafrost. Due to climate warming, irreversibly thawing permafrost is releasing organic matter frozen for up to a million years, most of which decomposes into carbon dioxide and methane, further enhancing the greenhouse effect. Part of this organic matter also consists of revived cellular microbes (prokaryotes, unicellular eukaryotes) as well as viruses that have remained dormant since prehistorical times. While the literature abounds on descriptions of the rich and diverse prokaryotic microbiomes found in permafrost, no additional report about “live” viruses have been published since the two original studies describing pithovirus (in 2014) and mollivirus (in 2015). This wrongly suggests that such occurrences are rare and that “zombie viruses” are not a public health threat. To restore an appreciation closer to reality, we report the preliminary characterizations of 13 new viruses isolated from seven different ancient Siberian permafrost samples, one from the Lena river and one from Kamchatka cryosol. As expected from the host specificity imposed by our protocol, these viruses belong to five different clades infecting Acanthamoeba spp. but not previously revived from permafrost: Pandoravirus, Cedratvirus, Megavirus, and Pacmanvirus, in addition to a new Pithovirus strain. Full article

This article presents the results of long-term research and monitoring of the soil cover exposed to the impact of the mining and processing plant developing diamond deposits in the northeast of Siberia. The soil collection includes 436 samples of different types of Cryosols. Soil pH; soil organic carbon (SOC); granulometric composition; and mobile forms of Pb, Ni, Mn, Cd, Co, Cr, Zn, Cu, and As were identified in the samples. Multivariate statistics of the correlation matrix, clustering analysis (CA), and principal component analysis (PCA) were used to determine the sources of heavy metals. The intensity of the accumulation of chemical elements in the soil was assessed using calculated concentration coefficients (K_c) and the index of total contamination of the soil cover (Z_c). In the study area, Cryosols are characterized by biogenic accumulation of Ni, Mn, and Cd in the upper soil layer and Cr, Ni, Co, Mn, and Cu in the suprapermafrost horizon. Correlation matrix, CA, and PCA revealed three distinct sources that could be considered for the investigated potentially toxic elements (PTEs): anthropogenic, lithogenic, and the source which comes from a mixed contribution of anthropogenic and lithogenic factors. The most anthropogenic contribution in the heavy metals in the study area appears in Zn, Cd, As, and Pb. The assessment interpreted that origin of Mn in the area is most likely to be a natural source. The content of Co, Cr, and Ni are controlled by both lithogenic control and anthropogenic sources. Active accumulation of mobile forms of Mn, Zn, and Ni with anomalously high concentration coefficients can be traced in the soils in the impact zone of mining operations. Anthropogenic soil contamination is spread over an area of 260 km². Full article

Forest fires are one of the most significant types of disturbance on a global scale, affecting biodiversity and biogeochemical cycles and playing an important role in atmospheric chemistry and the global carbon cycle. According to a remote monitoring information system, forest fires in Yakutia were the largest wildfires in the world in 2021. In this regard, mature pale-yellow soils unaffected by fire were investigated in comparison with the same soils that were strongly affected by surface fire in 2021 in the area surrounding Yakutsk, Yakutia region. Data obtained showed an intensive morphological transformation of the topsoil layers, increase of total organic matter and slight increase of pH, and apparent decrease of basal respiration and content of microbial biomass. A slight accumulation of Zn and Ni in soils due to wildfires was recorded, as well as alteration in the distributions of heavy metals in the soil profile. Moreover, an electric resistivity study was carried out during field studies. An influence of forest fire on the electrical resistivity value was not reliably found, but the vertical electrical resistivity sounding provided precise data regarding the degree of soil-permafrost layer homogeneity and/or heterogeneity. Full article

Vegetation and soils of the North Taiga zone were studied in natural and thermokarst-disturbed areas of Yana-Adycha interfluve (northeastern Yakutia). Soil research includes a description and physicochemical analysis of samples. The objects of study were selected taking into account the landscape diversity of the area experiencing permafrost melting due to pyrogenic factors under global climate change: young thermokarst and taiga untouched by fires and within the thermokarst basin of early Holocene. It was determined that the permafrost melting is accompanied by the transformation of homogeneous soil cover. After a forest fire, thawing depth increases and occurs redistribution of moisture and water-soluble matters. As a result, on the drier tops of byllars, the formation of albic material under the organogenic horizon is observed in the calcic cambic cryosol, which indicates a fairly fast transformation rate. In depressions, the forest is not recovered. In the mature alas, the vegetation and soil cover has a belt structure, represented by a combination of cryosols, stagnosols, and gleysols. In contrast to the soils of the Central Yakutia alases, there are almost no signs of lacustrine redeposition of soil, which indicates a difference in the processes of alas formation in different parts of the cryolitozone. Full article

In the Arctic zone, where up to 1024 × 1013 kg of organic matter is stored in permafrost-affected soils, soil organic matter consists of about 50% humic substances. Based on the analysis of the molecular composition of humic acids, we assessed the processes of accumulation of the key structural fragments, their transformations and the stabilization rates of carbon pools in soils in general. The landscape of the Lena River delta is the largest storage of stabilized organic matter in the Arctic. There is active accumulation and deposition of a significant amount of soil organic carbon from terrestrial ecosystems in a permafrost state. Under ongoing climate change, carbon emission fluxes into the atmosphere are estimated to be higher than the sequestration and storing of carbon compounds. Thus, investigation of soil organic matter stabilization mechanisms and rates is quite an urgent topic regarding polar soils. For study of molecular elemental composition, humic acids were separated from the soils of the Lena River delta. Key structural fragments of humic matter were identified and quantified by CP/MAS ¹³C NMR spectroscopy: carboxyl (–COOR); carbonyl (–C=O); CH^3–; CH^2–; CH-aliphatic; –C-OR alcohols, esters and carbohydrates; and the phenolic (Ar-OH), quinone (Ar = O) and aromatic (Ar–) groups as benchmark Cryosols of the Lena delta river terrestrial ecosystem. Under the conditions of thermodynamic evolutionary selection, during the change between the dry and wet seasons, up to 41% of aromatic and carboxyl fragments accumulated in humic acids. Data obtained showed that three main groups of carbon played the most important role in soil organic matter stabilization, namely C, H-alkyls ((CH₂)n/CH/C and CH₃), aromatic compounds (C-C/C-H, C-O) and an OCH group (OCH/OCq). The variations of these carbon species’ content in separated humics, with special reference to soil–permafrost organic profiles’ recalcitrance in the current environment, is discussed. Full article

Micromorphological investigation of soils is a powerful tool for studying the transformation of soils under the influence of various weathering mechanisms. In the Arctic region, under the influence of seasonal freezing/thawing processes, cryohydration is the leading type of weathering. Soils of different-aged islands of the Lena River Delta were investigated. Thin sections of soils were analyzed using a polarizing microscope Leica DM750P (Leica Camera AG, Wetzlar, Germany). X-ray fluorescence analysis was used to determine the chemical composition of the soils. As a result of the work, the rate of weathering of soil minerals was estimated, soil fabric was considered, as well as the chemical composition of the soil. The accumulation of poorly sorted circular striated sand due to active influence of the Lena River was noted on young soil from Samoylov isl. The formation of biogenic sand-silt crumb aggregates was noted at more ancient sites. Physical weathering of soil minerals under the influence of cryogenic processes has been noted. Full article