Das Projekt "Modellierung der Langzeitausbreitung von Cäsium 137 nach Freisetzung in den Pazifik vor Fukushima" wird vom Umweltbundesamt gefördert und von Helmholtz-Zentrum für Ozeanforschung Kiel (GEOMAR) durchgeführt. A sequence of global ocean circulation models, with horizontal mesh sizes of 0.5 , 0.25 and 0.1 , are used to estimate the long-term dispersion by ocean currents and mesoscale eddies of a slowly decaying tracer (half-life of 30 years, comparable to that of 137Cs) from the local waters off the Fukushima Dai-ichi Nuclear Power Plants. The tracer was continuously injected into the coastal waters over some weeks; its subsequent spreading and dilution in the Pacific Ocean was then simulated for 10 years. The simulations do not include any data assimilation, and thus, do not account for the actual state of the local ocean currents during the release of highly contaminated water from the damaged plants in March-April 2011. An ensemble differing in initial current distributions illustrates their importance for the tracer patterns evolving during the first months, but suggests a minor relevance for the large-scale tracer distributions after 2-3 years. By then the tracer cloud has penetrated to depths of more than 400 m, spanning the western and central North Pacific between 25 N and 55 N, leading to a rapid dilution of concentrations. The rate of dilution declines in the following years, while the main tracer patch propagates eastward across the Pacific Ocean, reaching the coastal waters of North America after about 5-6 years. Tentatively assuming a value of 10 PBq for the net 137Cs input during the first weeks after the Fukushima incident, the simulation suggests a rapid dilution of peak radioactivity values to about 10 Bq m-3 during the first two years, followed by a gradual decline to 1-2 Bq m-3 over the next 4-7 years. The total peak radioactivity levels would then still be about twice the pre-Fukushima values.
Das Projekt "Influence of permafrost on chemical and physical weathering" wird vom Umweltbundesamt gefördert und von Universität Zürich, Geographisches Institut durchgeführt. With increasing temperatures, permafrost is continuously thawing. This will lead in future to different thermal and hydrological conditions in the soil and regolith in cold regions. Therefore, climate change is assumed to cause a marked change in weathering conditions in high Alpine areas. Long-term chemical weathering and physical erosion rates are interrelated processes. In order to better understand landscape response to climate change, it is important to quantify both processes. The planned investigations generally aim at the estimate of element denudation/weathering rates and short- and long-term erosion of high Swiss Alpine soils (Upper Engadine: Albula and Val Bever). Both types of sites will be considered: a) with and b) without permafrost. The main objectives include 1) the evaluation of chemical weathering mechanisms using tracers such as immobile elements and Sr-isotopes 2) the determination of soil erosion rates (long-term) using two different techniques: a) in situ produced cosmogenic 10Be in soil sections and b) the inventory of meteoric 10Be in soils. Short-term erosion rates will be estimated using 137Cs as tracer. 3) determination of organic matter stocks in soil and characterisation and 14C dating of labile and stable (resistant to a H2O2 treatment) organic matter fractions. 4) Mapping of present day permafrost distribution and monitoring of near-surface and ground surface temperatures is essential for the understanding and prediction of the weathering behaviour of high Alpine regions. An important and innovative aspect is that chemical weathering and particularly erosion rates will be characterised using a multi-method approach. A cross-check of all the methods used will allow an extended interpretation and mutual control of the results. Furthermore, novel or very recently developed methods (erosion rates determined by meteoric 10Be using a non-steady-state approach; spatial on-site detection and characterisation of permafrost using a highly novel 3-D geophysical approach, 14C dating of stable (H2O2-resistant) soil organic matter, etc.) will be applied for the first time in high Alpine regions. The expected new insights will lead to a better understanding of the processes of high mountain soils and are a further step towards improving climate-related modelling of fast warming scenarios and increasing system disequilibria.
Das Projekt "Versauerungsentwicklung von 70 Hochgebirgsseen in kristallinen Einzugsgebieten Tirols und Kaerntens" wird vom Umweltbundesamt gefördert und von Universität für Bodenkultur Wien, Institut für Angewandte Geologie durchgeführt. Saure Depositionen fuehrten in grossen Gebieten Europas und Nordamerikas zur Versauerung von Gewaessern, deren Ausmass von Geologie, Groesse und Verwitterungsvermoegen der Einzugsgebiete abhaengig ist. Die zu untersuchenden Hochgebirgsseen liegen im Kristallin der Alpen und sind aufgrund der geologischen Verhaeltnisse ihrer Einzugsgebiete versauerungsgefaehrdet. Das gegenstaendliche Projekt besteht aus zwei Teilen: a) einem statistischen Vergleich des Seenzustandes anhand von 70 Hochgebirgsseen im Kristallin Tirols und Kaerntens im Abstand von 10 Jahren, und b) der Dokumentation langfristiger Entwicklungen von zwei charakteristischen Seen mit palaeolimnologischen Methoden. Es soll der Chemismus von 70 Hochgebirgsseen festgestellt werden. Zur Beurteilung der anthropogenen Belastung werden Schwermetall-, C-, N- und P-Analysen durchgefuehrt, die Datierung von aus zwei Seen entnommenen Sedimentkernen erfolgt mit 210Pb und 137Cs.