Bestimmung langlebiger kosmogener ($^{10}Be, ^{26}$Al)und anthropogener ($^{137}Cs, ^{238,239,240}$Pu) Radionuklidein Umweltproben mittels α-, γ- undBeschleuniger-Massen-Spektrometrie zur Untersuchunggeologischer Vorgänge

The combination of radioanalytical methods and ultrasensitive Accelerator Mass Spectrometry (AMS) allows the determination of long-lived cosmogenic radionuclides in the environment, which can be used to quantify geological processes. In the first part of the studies presented here, the radiochemical investigation of quartz rich samples from the interior of the Wohlthat-Massiv, Queen Maud Land, Antarctica is presented. The in-situ produced cosmogenic nuclides $^{10}Be and {26}$Al of two nunataks (isolated mountain peaks) at different elevations were measured by CologneAMS und ANU AMS to investigatethe surface exposure history. The pure quartz separates were prepared by two different methods (Kohl und Nishiizumi 1992, Altmaier 2000) and the results compared. The results provide a history for the ice sheet of this unexplored area which suggests, in close accordance with prior works (Altmaier et al. 2010), that the upper nunatak was exposed gradually between 0.75-3.57 million years ago, while the lower nunatak emerged from beneath the surface of the ice sheet over the period 0.65-1.10 million years ago. In the absence of tectonic uplift, this $^{10}Be and {26}$Al data suggest that the thickness of the ice was reduced from the polar center towards the coastal area in reaction to a global cooling process. The lowering rate of the ice surface is on the order of less than one meter per thousand years. In the second part of the studies, the anthropogenic influences on soil erosion in cultivated landscapes are investigated. Soil samples were analyzed by a radiochemical pathway designed by Priest et al. (1999) to extract and measure Fallout $^{(238),239,240}$Pu by $\alpha$-spectrometry and AMS. The pathway was adapted especially for the Cologne AMS and successfully established, however, some samples were also measured for validation by the ANU AMS. To verify the Pu-data, the long lived radionuclide $^{137}$Cs, which also originated from the fallout, was measured by x-ray spectrometry. The results of the examination show that during the first 20 years of cultivation nearly 50 % of the nuclide inventory was been removed. Due to the fact that plutonium and caesium bind predominantly on small particle sizes, the loss of falloutinventory directly reflects the loss of fertile fine soil fractions. This result correlates with the changes of the humus content and the decreased harvest reported by Lobe et al. (2001, 2005, 2011), i.e. due to erosion the most important nutrient reservoirs were carried away irreversibly over the first two decades of cultivation