ИСТИНА

The input of mineral dust pays an important role in the climate system and its main impacts include alteration of snow optical properties. Equally import is the changes in radiation budget and biogeochemical cycling of nutrients (iron, nitrogen and phosphorous), major and trace elements. Mineral dust from the North Africa and deserts of the Middle East is regularly deposited on the glaciers in Caucasus. These events disturb the chemistry of snow deposits. In this research we present a geochemical and mineralogical characterization of dust reaching the Caucasus. Snow and ice samples contained dust were analyzed for major cations and anions. Additionally trace elements were analyzed for selected samples. Mineralogical composition was analysed by X-ray diffraction using an Ultima IV X-ray diffractometer. The total dust deposited on glaciers may have three different components: dust from local sources (nunataks, rock outcrops), sporadic arrival of large aeolian desert dust events and background continuous terrigenous aerosol emissions. Composition of dust events was consistent with what is found in atmospheric aerosol collected at Mediterranean sites over periods of large dust events. The dust samples were presented by clay (smectite, palygorskite, illite, kaolinite, chlorite) and non-clay minerarls (quartz, calcite, dolomite, feldspar). The relative abundance of clay minerals was high (> 30%), that together with the smaller sizes of particles indicate long-range transport. EF of trace elements in dust samples were compared with EF of local anthropogenic and natural sources in Elbrus area. The research was supported by the Russian Science Foundation (project no. 17-17-01270).