Analyses of LASI (Light Absorbing Snow Impurities) within samples of snow pits collected in an high alpine environment

Abstract

Global warming is impacting the earth way faster than expected. Several processes take part in global warming and thus may enhance or reduce the effects. One of them is the Albedo, which is the fraction of solar light that is reflected by a surface and therefore contributes to the prevention of further warming. Fresh snow shows a high albedo, but the presence of Light Absorbing Snow Impurities (LASI) leads to faster melting snow, because the impurities heat up. This leads to less snow and therefore to less albedo. This thesis is dedicated to analyzing three different groups of LASI. Water Insoluble Organic Carbon (WIOC), Elemental Carbon (EC) and Mineral Dust (MD). The analysis of carbon is achieved through a thermal - optical analyzer (TOA). For MD, Inductively Coupled Plasma - Optical Emission Spectroscopy (ICP – OES) was applied. To compare the samples taken from different positions at the glacier, cation - chromatography was used. Based on the calcium and especially the ammonium concentrations, a comparison of the snow samples investigated within this thesis with earlier samples collected nearby was possible. The data showed good agreement, regarding the seasonal trend as well as absolute concentration values. Therefore, the two data sets can be merged for future investigations. A comparison of the WITC (Water Insoluble Total Carbon), WIOC and EC data with studies conducted in other regions, allowed to discuss agreement and differences regarding elevation, vicinity of emission sources and remoteness of the site. Except of 2020, all carbon depth profiles do not show a seasonal trend. For all other years elevated concentrations could be seen at different times, throughout the year. Besides carbon parameters, data for thirteen elements was analyzed. With those concentrations, a mass balance of fifteen MD samples was done. With the data gathered in this thesis, WITC, WIOC, EC and MD concentrations representing the accumulation periods of the years 2017 - 2022 from the Austrian Alps are available and can be used for comparison and modeling. Additionally, a method for the correction of the TOA for samples containing MD has been elaborated and looks very promising. Three criteria for the determination whether a sample contains MD or not, were tested and evaluated. MD accounts for the majority of the mass of insoluble particles, being much more prominent than organic matter.