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Abstract

39Ar Atom Trap Trace Analysis (ATTA) is a new dating method for the environmental sciences. With its half-life of 269 years and a dating range of 50 to 1000 years, it closes a gap in the set of the previously available dating methods. This thesis provides the first application of 39Ar ATTA on a lake system, i.e. Lake Kivu in Rwanda, including an elaborate data analysis routine using a 1D simulation tool. With 39Ar ATTA, extreme concentrations of 39Ar were found in some distinctly localised water layers in Lake Kivu and using the 1D simulation analysis, this effect could be traced to groundwater inflow springs featuring the highest 39Ar concentrations described so far. Several methodological improvements are presented as well which were necessary to achieve feasibility for this 39Ar ATTA study on Lake Kivu. Additionally, the potential of a total dissolved gas sensor (TDG) is explored with the aim of expanding its capabilities to measure the dissolved gasses in Lake Kivu and their partial pressures. An experimental setup to this end that simulates a pressure environment comparable to Lake Kivu is presented. Data from this experiment show the complexity of the coupled system of dissolved CH4 and CO2, water and a PTFE membrane. Moreover, a method to achieve a good partial pressure resolution from the TDG measurements of Lake Kivu is presented. Finally, a brief summary of the application of 39Ar ATTA on several environmental systems further demonstrates the versatility of 39Ar dating with ATTA for different environmental research contexts.