Abstract
Artificial snow production is a crucial part of modern skiing resorts in Austria and globally, and will develop even more so with changing precipitation patterns and a warming climate trend. Producing artificial snow requires major investments in energy, water, infrastructure and manpower for skiing resorts. In addition to appropriate meteorological conditions, the efficiency of artificial snow production depends on heterogeneous ice-nucleation, which can occur at temperatures as high as −2°C when induced by specific bacterial ice nucleating particles (INPs). We aimed to investigate the presence, source and ice nucleating properties of these particles in the water cycle of an alpine ski resort in Obergurgl, Tyrol, Austria. We sampled artificial snow, river water, water pumped from a storage pond and compared it to samples collected from fresh natural snow and aged piste snow from the area. Particles from each sampled system were characterized in order to determine their transport mechanisms at a ski resort. We applied a physical droplet freezing assay [DRoplet Ice Nuclei Counter Zurich (DRINCZ)] to heated and unheated samples to characterize the biological and non-biological component of IN-activity. Bacterial abundance and community structure of the samples was obtained using quantitative PCR and Illumina Mi-Seq Amplicon Sequencing, and their chemical properties were determined by liquid ion-chromatography, energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). The results show the flow of biological and inorganic material from the river to the slopes, an uptake of new microorganisms through the air and the piping, and possible proliferation or introduction of ice nucleation active biological particles in aged piste snow. Natural snow, as the first stage in this system, had the lowest amount of ice nucleation active particles and the least amount of biological and mineral particles in general, yet shares some microbial characteristics with fresh artificial snow.
Highlights
A wide range of scientific research indicates a warming trend of the global climate, with the Alps especially prone (IPCC, 2014)
The highest concentration of ice nucleating particles (INPs) at high temperatures and the largest heterogeneities were found in the aged slope snow
The natural snow samples showed the lowest activities of all samples and extended below the previously reported INP concentrations from precipitation (Figure 2A; Petters and Wright, 2015)
Summary
A wide range of scientific research indicates a warming trend of the global climate, with the Alps especially prone (IPCC, 2014). INPs play an important role in the formation of clouds (Cziczo et al, 2013), where natural snow crystals originate They impact cloud radiative properties, cloud lifetime and climate (Matus and L’Ecuyer, 2017). Biological additives like Snomax R , originating from inactivated ice nucleating P. syringae, are prohibited for snow production in many countries, including Austria. Even when no additives are used for snow production, there are always INPs present in the water used and in the general environment Their concentration has been reported to be enhanced in precipitation and freshly fallen snow, indicating that certain active nucleators might trigger precipitation, and accumulate there (Christner et al, 2008a,b; Conen et al, 2017). In this study we investigate for the first time how microbial as well as non-microbial INPs are introduced, distributed and persist in such a system and assess their impact on the overall ice nucleation ability of the water
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