Showing papers by "Roland Psenner published in 2009"

High microbial activity on glaciers: importance to the global carbon cycle

Abstract: Cryoconite holes, which can cover 0.1–10% of the surface area of glaciers, are small, water-filled depressions (typically o1 m in diameter and usually o0.5 m deep) that form on the surface of glaciers when solar-heated inorganic and organic debris melts into the ice. Recent studies show that cryoconites are colonized by a diverse range of microorganisms, including viruses, bacteria and algae. Whether microbial communities on the surface of glaciers are actively influencing biogeochemical cycles or are just present in a dormant state has been a matter of debate for long time. Here, we report primary production and community respiration of cryoconite holes upon glaciers in Svalbard, Greenland and the European Alps. Microbial activity in cryoconite holes is high despite maximum temperatures seldom exceeding 0.11C. In situ primary production and respiration in cryoconites during the summer is often comparable with that found in soils in warmer and nutrient richer regions. Considering only glacier areas outside Antarctica and a conservative average cryoconite distribution on glacial surfaces, we found that on a global basis cryoconite holes have the potential to fix as much as 64 Gg of carbon per year (i.e. 98 Gg of photosynthesis minus 34 Gg of community respiration). Most lakes and rivers are generally considered as heterotrophic systems, but our results suggest that glaciers, which contain 75% of the freshwater of the planet, are largely autotrophic systems.

Microbiology and atmospheric processes: biological, physical and chemical characterization of aerosol particles

Abstract: . The interest in bioaerosols has traditionally been linked to health hazards for humans, animals and plants. However, several components of bioaerosols exhibit physical properties of great significance for cloud processes, such as ice nucleation and cloud condensation. To gain a better understanding of their influence on climate, it is therefore important to determine the composition, concentration, seasonal fluctuation, regional diversity and evolution of bioaerosols. In this paper, we will review briefly the existing techniques for detection, quantification, physical and chemical analysis of biological particles, attempting to bridge physical, chemical and biological methods for analysis of biological particles and integrate them with aerosol sampling techniques. We will also explore some emerging spectroscopy techniques for bulk and single-particle analysis that have potential for in-situ physical and chemical analysis. Lastly, we will outline open questions and further desired capabilities (e.g., in-situ, sensitive, both broad and selective, on-line, time-resolved, rapid, versatile, cost-effective techniques) required prior to comprehensive understanding of chemical and physical characterization of bioaerosols.

Trace elements in alpine and arctic lake sediments as a record of diffuse atmospheric contamination across Europe

Abstract: Summary 1. We surveyed the distribution of several trace elements in contemporary and pre-industrial sediment s in 275 lakes in alpine and arctic lake districts across Europe including the Pyrenees, Alps, the Rila Mountains, Retezat, Julian Alps, Tatras, Scottish mountains, Central Norway and Greenland. 2. Sediment cores were collected at the deepest part of each lake and analysed at two depths (surface sediment and at 15–17 cm depth) for Ti, Pb, Cd, Zn, Cu, As, Hg and Se. 3. The concentrations of trace elements found in the lakes included in the survey are comparable to those reported in aquatic sediments receiving higher contamination loads. With the exception of Greenland, a large percentage of lakes showed enrichment factors for most elements well above 1.5, indicating atmospheric contamination. The influence of contamination has increased the co-distribution of trace elements in sediments, with the exception of As. 4. Pb is the element that shows the highest contamination level at the European scale, followed by Hg and As. Zn, Cd, Cu and Se contamination is detectable to a lower degree. 5. The Tatra Mountains and Scotland seem to be most affected. Natural mechanisms leading to the formation of highly organic, metal-binding sediments may be the cause of the high levels in Scotland, whereas those in the Tatras appear to be due to elevated deposition. 6. The Retezat and Central Norway appear to be least polluted. 7. In the Alps, enrichments in Pb, Hg and Zn are higher in southern than in central areas suggesting a flux of these pollutants from the south. In the Pyrenees, the high natural levels of As are remarkable. Metal enrichments in the Rila Mountains are comparable to those in the Tatras, but concentrations are much lower. 8. In general terms, the increase in trace elements in modern with respect to pre-industrial sediments reflects the history of a long range contamination affecting the remotest locations in Europe.

Lakes of Europe

Abstract: Lakes of Europe show a great variability in their characteristics, with boreal lakes at northern latitudes as the most abundant lake type. The variability is a result of large gradients in climate, geological history, land use, and atmospheric deposition, mainly along a north–south axis. Worldwide, the best known lakes are probably Europe's lakes in the Alp region, most likely due to their spectacular surroundings and their long tradition of providing good research facilities with all necessary infrastructure. Lakes of Europe, including very remote lakes, are subjected to multiple stressors, climate change and atmospheric deposition being examples. These stressors can cause water quality problems. One of the most common water quality problems occurring in all European countries have been and still are harmful algal blooms.