Arsen i dansk drikkevand - et undervurderet sporstof

Epidemiologiske undersøgelser har vist, at grundstoffet arsen selv i små mængder kan forårsage alvorlige sygdomme. Grænseværdien i drikkevand er derfor sænket til en femtedel af den tidligere værdi. Det giver en del problemer for grundvandet som drikkevandsressource

Mars og Marsaktiviteter - nye projekter under opsejling

Mars Simulerings Laboratoriet på Aarhus Universitet har bidraget med vigtig viden i forbindelse med Mars-missionerne, og der er også udsigt til, at igangværende projekter kommer i betragtning til NASAs og ESAs Mars-ekspeditioner i 2007 og 2011

Microbial iron reduction and greenhouse gas production in response to organic matter amendment and temperature increase of periglacial sediments, Bolterdalen, Svalbard

Arctic permafrost soils store substantial reserves of organic matter (OM) from which microbial transformation contributes significantly to greenhouse gas emissions of CH4 and CO2. However, many younger sediments exposed by glacier retreat and sea level change in fjord landscapes lack significant organic carbon resources, so their capacity to promote greenhouse gas emissions is unclear. We therefore studied the effects of increased temperatures (4°C and 21°C) and OM on rates of Fe(III) reduction, CO2 production, and methanogenesis in three different Holocene sedimentary units from a single site within the former marine limit of Adventdalen, Svalbard. Higher temperature and OM addition generally stimulated CH4 production and CO2 production and an increase in Bacteria and Archaea abundance in all units, whereas an equal stimulation of Fe(II) production by OM amendment and an increase in temperature to 21°C was only observed in a diamicton. We observed an accumulation of Fe(II) in beach and delta deposits as well but saw no stimulating effect of additional OM or increased temperature. Interestingly, we observed a small but significant production of CH4 in all units despite the presence of large reservoirs of Fe(III), sulfate, and nitrate, indicating either the availability of substrates that are primarily used by methanogens or a tight physical coupling between fermentation and methanogenesis by direct electron transfer. Our study clearly illustrates a significant challenge that comes with the large heterogeneity on a narrow spatial scale that one encounters when studying soils that have complex histories.publishedVersio

Влияние семантики локализованности на текстовую внешнетемпоральную транспозицию

Языковая временная семантика в лингвистических исследованиях последних лет рассматривается как широкая сфера языковых/речевых отношений различных категорий (грамматических, функционально- семантических, текстовых), т.е. как область пересечения, иногда концентрации аспектуального, собственно темпорального, таксисного и другого аналогичного содержания, где центральное место принадлежит глагольной единице, потенциальные функциональные возможности которой и определяют указанные грамматические отношения

Analysis and survival of amino acids in Martian regolith analogs

We have investigated the native amino acid composition of two analogs of Martian soil, JSC Mars-1 and Salten Skov. A Mars simulation chamber has been built and used to expose samples of these analogs to temperature and lighting conditions similar to those found at low latitudes on the Martian surface. The effects of the simulated conditions have been examined using high-performance liquid chromatography (HPLC). Exposure to energetic ultraviolet (UV) light in vacuum appears to cause a modest increase in the concentration of certain amino acids within the materials, which is interpreted as resulting from the degradation of microorganisms. The influence of low temperatures shows that the accretion of condensed water on the soils leads to the destruction of amino acids, supporting the idea that reactive chemical processes involving H2O are at work within the Martian soil. We discuss the influence of UV radiation, low temperatures, and gaseous CO2 on the intrinsic amino acid composition of Martian soil analogs and describe, with the help of a simple model, how these studies fit within the framework of life detection on Mars and the practical tasks of choosing and using Martian regolith analogs in planetary research

Silicates Eroded under Simulated Martian Conditions Effectively Kill Bacteria—A Challenge for Life on Mars

The habitability of Mars is determined by the physical and chemical environment. The effect of low water availability, temperature, low atmospheric pressure and strong UV radiation has been extensively studied in relation to the survival of microorganisms. In addition to these stress factors, it was recently found that silicates exposed to simulated saltation in a Mars-like atmosphere can lead to a production of reactive oxygen species. Here, we have investigated the stress effect induced by quartz and basalt abraded in Mars-like atmospheres by examining the survivability of the three microbial model organisms Pseudomonas putida, Bacillus subtilis, and Deinococcus radiodurans upon exposure to the abraded silicates. We found that abraded basalt that had not been in contact with oxygen after abrasion killed more than 99% of the vegetative cells while endospores were largely unaffected. Exposure of the basalt samples to oxygen after abrasion led to a significant reduction in the stress effect. Abraded quartz was generally less toxic than abraded basalt. We suggest that the stress effect of abraded silicates may be caused by a production of reactive oxygen species and enhanced by transition metal ions in the basalt leading to hydroxyl radicals through Fenton-like reactions. The low survivability of the usually highly resistant D. radiodurans indicates that the effect of abraded silicates, as is ubiquitous on the Martian surface, would limit the habitability of Mars as well as the risk of forward contamination. Furthermore, the reactivity of abraded silicates could have implications for future manned missions, although the lower effect of abraded silicates exposed to oxygen suggests that the effects would be reduced in human habitats

Chemical and isotopic characteristics of a glacier-derived naled in front of Austre Grønfjordbreen, Svalbard

The chemical and stable isotope composition of a glacier-derived naled in front of the glacier Austre Grønfjordbreen, Svalbard, is examined to elucidate how secondary processes such as preferential retention and leaching affect naled chemistry. Internal candle ice layers have a chemical composition almost similar to that of the lower stratified granular ice layer, whereas the upper granular ice layer has a significantly different composition, which resembles the composition found in glacier meltwater. Grey, platy cryogenic calcite precipitates are found in clusters on the surface of the naled assemblage, indicating preferential retention of Ca2 +  and HCO3 −. This process is particular pronounced in the distal part of the naled. The isotopic composition in the naled is in accordance with the local meteoric water line and without indications of kinetic fractionation during freezing. The ability to form ice-marginal naled indicates that Austre Grønfjordbreen has the high meltwater storage potential required for triggering a glacier surge event