The study of cryoconite – a specific organomineral sediment on the glacier surface – is essential to estimate environmental processes and sustainability, biogeochemical cycles, pollution rate and degree of human influence under conditions of climate change and diverse anthropogenic activities. Key chemical and physical features such as pH values, total organic carbon and hot-water extractable carbon content, microbial respiration, and particle-size distribution, as well as the content of some trace elements and pollution indices have been determined in materials sampled at the Mt. Elbrus region. The results obtained showed accumulation of easily decomposable carbon and correlated with it high rate of microbial respiration at the Garabashi Glacier, despite the low content of total organic carbon (max. 0.92

The intensive urbanization of environments and technogenic activity has an effect on the accumulation of trace elements in the soil and increases the toxicological risk to the terrestrial ecosystems and human health. We studied the distribution of seven priority trace elements (As, Cd, Pb, Zn, Ni, Cu, Hg) in the soil of the northernmost city in the world with a population more than 1 million people. To identify the spatial distribution of the trace elements, the GIS technologies have been used. Based on the data obtained, interactive maps of soil pollutionSoil pollution were made. It was found that the content of the studied trace elements exceeds the background values for the region and has a “hot spots” character. Four of the studied elements (Cu, Zn, Pb, As) on average exceed values of maximum permissible concentrations in soil. The highest levels of pollution are concentrated in the central part of the city, and this is associated with the location of major transport roads, as well as railway stations located in the city center. Accumulation of trace elements occurs in bottom sediments in the rivers of St. Petersburg, and this is associated with lateral runoff of dust from roads and adjacent areas. The level of contamination of bottom sediments varied with the degree of proximity to major transportation hubs. According to the analysis of the index, Zc was found that 57.35

The globalisation and omnidirectional character of anthropogenic processes has challenged scientists around the world to estimate the harmful effects of these processes on ecosystems and human health. Polycyclic aromatic hydrocarbons (PAHs) is one the most infamous group of contaminants, originated both from natural and anthropogenic processes. They could transport to high latitudes and altitudes through atmospheric long-distance transfer and further enter ecosystems of these vulnerable regions by deposition on terrestrial surfaces. An interesting object for tracking transboundary contamination processes in high mountain ecosystems is called cryoconite. Cryoconite, a dark-coloured supraglacial sediment which is abundant in polar and mountain environments, is considered as a storage of various pollutants, including PAHs. Thus, it may pose a risk for local human health and ecosystem through short-distance transfer. Studied cryoconite sediments were collected at the surface of Skhelda and Garabashi glaciers, Central Caucasus high-mountain region, as well as mudflow, moraine material and local soils at the Baksan Gorge in order to examine levels of their contamination. We analysed the content of 15 priority polyaromatic compounds from the US EPA list and used the method of calculation of PAHs isomer ratios with the purpose of identifying their source. To estimate their potential toxicity, Benzo[a]pyrene (BaP) equivalents were calculated. Maximum concentration was defined for NAP (84 ng×g-1), PHE (40 ng×g-1) and PYR (47 ng×g-1), with the minimum concentration for ANT (about 1 ng×g-1). The most polluted material is a cryoconite from Garabashi glacier because of local anthropogenic activities and long-distance transfer. High-molecular weight PAHs are dominated in PAHs composition of almost all samples. The most common sources of PAHs in studied materials are combustion processes and mixed pyrolytic/petrogenic origin. Toxicity levels of separate PAHs did not exceed the maximum permissible threshold concentrations values in most cases. However, the sum of PAHs in BaP equivalents exceed the threshold values in all samples, in some of them more than twice.

The surface of mountain glaciers is a place of accumulation of various biogenic organomineral and mineral compounds. As a result of intensive mass deglaciation of glaciers due to climate change and anthropogenic activity, this material can significantly affect the transformation of the landscape in the periglacial zone. Thus, this work considers the contamination of the surface of the Arctic, Antarctic, and Caucasian glaciers by priority pollutants. Atomic absorption spectroscopy was used to analyze trace elements (Cu, Zn, Ni, Cd, Pb) from cryoconite deposits. It was revealed that the cryoconite dust on the Ray-Iz glacier (Polar Urals) has a high level of nickel contamination, which comes to the glacier from local rock materials as a result of their weathering. The lowest concentrations of trace elements are found in one of the Arctic plots located at Mushketov and Aldegonda glaciers, the Caucasus, and the Antarctic, which is due to their relatively low content in the composition of rocks and the relatively low contribution of long-range transport of matter to the polar regions. Contamination of moraine sediments in the periglacial zone can make a significant contribution to the formation of the soil cover of these territories, the pollution of water bodies near the glacier, as well as affect the quality of life of the people living in the immediate vicinity of the mountain areas.

Cryoconite is a dark-colored supraglacial dust which may be found in polar and mountain regions in the world. These sediments represent a combination of mineral particles, black carbon and organic matter. Cryoconite is considered as a microbial hotspot on an uninhabited surface of glaciers as well as material which influence the level of albedo. Due to relatively similar microbiological and physicochemical features of cryoconite it could take part in development of primary soils. This is important because of current rapid deglaciation in the Caucasus region which will intensify due to ongoing climate change. The purpose of this research is to study physicochemical features of cryoconite, other types of sediments and cryoconite derived periglacial soils in Caucasus region, Kabardino-Balkarian republic as well as local Chernozems. Samples of cryoconite, moraines and mudflows were collected at Bezengi Glacier, the largest valley glacier at the Caucasus mountains. Cryoconite derived soils were collected in the adjacent Khulamo-Bezengi Gorge; Chernozems and fresh mudflow material were sampled at Baksan Gorge. Soil acidity (H2O, CaCl2), total organic carbon (TOC), basal respiration values and particle-size distribution were determined under laboratory conditions. Almost all samples of materials from the Bezengi Glacier as well as Chernozems were characterized by a neutral reaction, while some samples of mountain soils of the Khulamo-Bezengi Gorge were characterized as slightly acidic and acidic, especially with regard to exchangeable acidity. Basal respiration values range from 2.20 mg of CO2 per day in fresh mudflow to 35.09 mg of CO2 per day in the upper horizon of mountain soils. In general, relatively high values of basal respiration were typical for mountain soils, which also has been observed in cryoconite from cracks and holes due to high amount of easily accessible organic matter. Most of cryoconite and moraines from the Bezengi Glacier were characterized by a low content of organic carbon (about 0.10%), while in the upper horizons of mountain soils these values were the highest (up to 7.54%) due to input of cryoconite material in soils through water streams in the warm period of the year. Cryoconite and moraines were characterized by the predominance of coarse earth fraction while soils were characterized by the dominance of fine earth material. The study of particle-size of cryoconites and other materials from the Bezengi Glacier showed the dominance of the sand fraction (d=0.05-1mm). Fresh mudslides from the Baksan Gorge and mountain soils of the Khulamo-Bezengi Gorge were characterized in the same way. Chernozems of the Baksan Gorge were characterized by a high content of silt and clay fractions, which makes it possible to classify them as clay and clay loam. This work was supported by Russian Foundation for Basic Research, project No 19-05-50107 “The role of microparticles of organic carbon in degradation of ice cover of polar regions of the Earth”.

The problem of retreating glaciers is pronounced in almost all high-altitude and high-latitude landscapes. Black carbon is considered as one of the most important pollutants that contributes to global climate change and the melting of glaciers, especially in polar and mountainous regions due to formation of cryoconite. It is a supraglacial sediment which represents a mixture of black carbon, mineral particles and organic matter. Cryoconites are considered as accumulators of various pollutants such as polycyclic aromatic hydrocarbons, trace elements and radionuclides, which can be transported by aeolian and water flows to the downstream ecosystems and affect the safety of the region both directly and indirectly, through the cultivation of crops and grazing. Moreover, cryoconites considerably reduce the albedo of the glacier and take part in formation of primary soils after its retreat which is especially important in the context of global climate change.The main purpose of this research is to study the pollution of cryoconites, other sediments and soils by trace elements at the Central Caucasus mountainous region, Russia. Cryoconite, moraines and mudflows were sampled from the biggest valley glacier at the Caucasus mountains, Bezengi Glacier; cryoconite derived soils were collected from the Khulamo-Bezengi Gorge. Chernozems and fresh mudflow samples were collected at Baksan Gorge. Trace elements content was determined by flame and electrothermal atomic absorption spectrometric method according to the standard ISO 11047-1998 at Atomic absorption spectrophotometer. We determined concentrations of Cu, Pb, Zn, Ni, Cd due to the facts that they are the most toxic for human health as well as they are mostly accumulated in a black carbon.High concentrations of Zn (70.9 mg/kg) and Pb (30.0 mg/kg) in cryoconites have been determined on the Bezengi Glacier, which may be due to both local human activities and allochthonous pollution associated with the arrival of contaminated air masses from other regions. The content of Cu (max. 17.4 mg*kg), Ni (max. 19.0 mg*kg) and Cd (max. 0.052 mg*kg) was relatively low. However, concentrations of Zn (max. 89.2 mg*kg) and Cd (max. 0.313 mg*kg) in cryoconite derived soils were higher than in cryoconite which indicates high input of polluted material from the glacier into downstream ecosystems. The highest level of pollution with some trace elements has been determined in fresh mudflow: Cu = 40.7 mg*kg, Zn = 89.3 mg*kg, Ni = 42.0 mg*kg which also indicates that sediments act as a source of pollutants for mountain ecosystems. Pollution of Chernozems with trace elements was higher than in moraine sediments, however, it was lower than in cryoconites which shows possible impact of these sediments on pollution status of soils in mountainous region.This work was supported by Russian Foundation for Basic Research, project No 19-05-50107 “The role of microparticles of organic carbon in degradation of ice cover of polar regions of the Earth”.

In the Central Caucasus region, the intense process of deglaciation is identified as caused by cryoconite formation and accumulation. The fine earth materials were collected on the surfaces of Skhelda and Garabashi glaciers as well as from zonal soils of Baksan Gorge and were studied in terms of chemical, particle-size, and micromorpholo-gical features. Supraglacial sediments are located at the glacial drift area of material and, thus, due to transfer of these sediments to the foothill area, their fine earth material can affect micromorphological and chemical characteristics of adjacent zonal soils. Thin sections of mineral and organo-mineral micromonoliths were analyzed by classic micromorphological methods. Data obtained showed that the weathering rates of cryoconite and soil minerals are different. The cryoconite material on the debris-covered Skhelda Glacier originated from local massive crystalline rocks and moraines, while for Garabashi Glacier the volcanic origin of cryoconite is more typical. Soils of Baksan Gorge are characterized by more developed microfabric and porous media, but their mineralogical composition is essentially inherited from sediments of glacial and periglacial soils. These new data could be useful for understanding the process of evolution of the mineral matrix of cryoconite to the soil matrix formed at the foot of the mountain.

Rapid deglaciation is one of the most important challenges in the Earth science today. One reason of this is specific supraglacial sediments — cryoconites, which represent carbon-containing dust with organomineral matter and living organisms. Investigation of physical and chemical characteristics of cryoconites in the Central Caucasus is necessary in order to understand their influence on alpine territories biogeochemical cycles, pollution and development in conditions of intensive glacial melting and active anthropogenic influence. For this research cryoconites as well as moraines, soil-like bodies and soils have been sampled from the alpine Bezengi Glacier and adjacent Khulamo-Bezengi Gorge. Key physicochemical features (pH values, total organic carbon content, microbial respiration, particle-size distribution) as well as content of trace elements have been defined in sampled materials and several pollution indices (Geoaccumulation index, Contamination factor and Degree of pollution) have been calculated. Results obtained show low values of total organic carbon in cryoconites (max. 0.23%) but high values (max. 7.54%) in top horizon of soils located in floodplain, indicating its active fluvioglacial transfer which may further accelerate the development of soils. Microbiological activity in the studied soils was mostly influenced by additional input of labile organic carbon from cryoconites with water flows. Particle-size distribution was similar among the studied cryoconites, indicating dominance of sand fraction (up to 85.28%) while studied soils showed higher variability due to influence of weathering. Among the trace elements, cryoconites were mostly polluted by Zn (max. 85.70 mg·kg −1 ) which corresponds to high pollution according to pollution indices; Pb (max. 24.90 mg·kg −1 ) and Cu (max. 17.40 mg·kg −1 ), up to moderate pollution level. Redistribution of polluted cryoconite material as well as local anthropogenic activities increased pollution of periglacial soils by Zn (max. 89.20 mg·kg −1 ), Pb (max. 15.00 mg·kg −1 ) and Cu (max. 12.80 mg·kg −1 ), which was also proven by the pollution indices with up to high level of pollution.

Determination of geochemical and microbiological properties of the cryoconite, related types of sediments and periglacial soils is essential to investigate impact of glaciers on terrains development at the Central Caucasus region. The studied sediments were sampled at the Garabashi and Skhelda glaciers as well as in vertical sections of local soils at the Baksan gorge. Sampled materials were investigated in terms of physicochemical parameters and nutritional state. The trace elements concentrations (Cu, Pb, Zn, Ni, Cd) were also evaluated in samples selected. The data obtained shows much higher content of organic carbon in soils (up to 7.82%) in comparison with cryoconite (max. 1.63%) due to the effect of superficial vegetation cover, however, rates of microbial activity were similar between some samples of sediments and soils. The analysis of the particle size distribution shows a similarity of the studied materials: in almost all samples, there is a dominance of the sand fraction. Cryoconite sediments on both of the above-mentioned glaciers are found as enriched with phosphorus, essential values of potassium (298 mg/kg in K2O units) and ammonium nitrogen (N-NH4 - max. 247 mg*kg) are identified at Garabashi glacier which could be a result of long-distant transfer and anthropogenic activity. The highest content among trace elements was identified for Zn (62 mg*kg for cryoconite and 60.5 mg*kg for soils), the most contaminated materials were sediments from Garabashi glacier and Entisols, up to moderate level, which is mostly associated with anthropogenic activity. Thus, development of tourism in the Central Caucasus, which is mostly associated with construction and transport, affects the pollution status of supraglacial sediments and periglacial soils as well as their agrochemical and microbiological features.

Cryoconites are a dark-colored granular sediments found in glacial landscapes. Cryoconites are known as a dark colored accumulation of various origin material in superficial holed of the glaciers which formed in polar and mountain regions of the Earth. They can significantly accelerate glacier retreating by reducing the albedo of the glacier and play a significant role in the colonization of the territory after its retreat, being an "oasis" for development of microorganisms on an uninhabited glacier surface. The understanding of key cryoconites properties is necessary to understand their impact on the mountain glaciers of the Central Caucasus, especially taking into account their recent rapid retreat.The aim of this research is to study the physical and chemical characteristics of various cryoconites and cryoconite derived periglacial soils of the Central Caucasus. Eight cryoconite samples and eight soil samples from three soil sections were selected. The following characteristics of the samples were determined in laboratory conditions: total organic carbon (TOC), basal respiration level, pH H2O and exchangeable soil acidity, solid phase density and particle size distribution.The results of the analyses showed both differences and some similarities in the physical and chemical characteristics of the cryoconites and soils of periglacial zone which were studied. Cryoconites, on average, are characterized by lower values of basal respiration than more developed soils from this region. The total organic carbon content in most samples was relatively low, but its values increase significantly soils investigated due to accumulation of carbon in fine earth under the influence of primary vegetation. The water extractable acidity values showed a significant similarity between the studied cryoconites and soils, they vary from slightly acidic to slightly alkaline in both groups. At the same time, the variation of exchangeable acidity values between cryoconite samples is significantly greater than in developed soils. Moreover, the density of the solid phase of the studied cryoconites varies in a larger range of values than that of the studied soils due to variety of sources of cryoconite materials. However, the analysis of particle size distribution showed a significant similarity of the studied objects: in almost all samples there is a significant dominance of the sand fraction (d=1-0.05 mm). The obtained data indicate both the difference in the physical and chemical properties of the studied cryoconites among themselves, and the probable influence of cryoconites on soil formation in this region.This work was supported by Russian Foundation for Basic Research, project No 19-05-50107 “The role of microparticles of organic carbon in degradation of ice cover of polar regions of the Earths and in the process of soil-like bodies formation”.

Climate change and deglaciation are active processes in current changing environments. In the Central Caucasus region rapid degradation of glaciers is caused often by the formation of superficial blackcolored sediments — cryoconite. Cryoconite plays a crucial role in changing ecosystems and may contribute to the formation of primary soils after glacier retreat. Over the past 20 years, the frequency of mudflows and other dangerous mountain events have increased in the Central Caucasus, which is associated with the glacial retreats. Intensification of tourism results in increasing of traffic, recreational activity and environment contamination. Determination of the cryoconites geochemical properties in comparison with other types of sediments and local soils is crucial for investigation of geochemistry and contamination state of superficial glacial sediments. This environmental aspect is important in terms of the Central Caucasus settlements safety under conditions of deglaciation and anthropogenic influence. The sediments studied (cryoconite, mudflow, moraine) were sampled at Garabashi and Skhelda glaciers as well as some local soils at the Baksan gorge. Sampled materials were investigated in terms of physicochemical and agrochemical parameters. The concentrations of trace elements (Cu, Pb, Zn, Ni, Cd) were also determined and contamination indices (geoaccumulation index — Igeo, contamination factor - CF and degree of contamination — Cdegree) were used to evaluate the pollution status of studied material. Data obtained shows much higher content of organic carbon in soils (up to 7.82%) in comparison with cryoconite (max. 1.63%) due to presence of vegetation, however, the basal respiration values in some cases were similar between сryoconite and soils, indicating high rates of microbial activity in a cryoconite holes. It was found that almost all materials studied have sandy structure. Cryoconite sediments on both of the glaciers are enriched with phosphorus, high values of K2O (max. 298 mg·kg-1) and N-NH4 (max. 247 mg·kg-1) are identified at Garabashi glacier which could be influenced by long-distant transfer but mostly a result of local anthropogenic activity. In case of trace elements, the highest content is identified for Zn (62 mg·kg-1 for cryoconite and 60.5 mg·kg-1 for soils) and the most contaminated materials are cryoconite from Garabashi glacier and Entisols, up to moderate level, which is mostly associated with local anthropogenic activity.