Migration of organic carbon and trace elements in the system glacier-soil in the Central Caucasus alpine environment.

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. [ABSTRACT FROM AUTHOR]