Dynamics of reactive and inert gases in soil air and groundwater in the context of thedetermination of noble gas temperatures

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Dissolved (noble) gases in groundwater are established tracers for dating as well as reconstruction of climate conditions in the past. Noble gas studies of recent years have shown that a better understanding of the processes that determine gas contents during groundwater recharge is necessary - especially with regard to the use of noble gases in groundwater in paleoclimate research. Hence, in this study, the importance of reactive gas processes in the subsurface under various hydrogeological and climatic conditions shall be studied empirically as well as with the help of modeling. To derive as general as possible conclusions, the project comprises the installation and subsequent sampling of a total of 4 test sites. A detailed understanding of the interaction between the unsaturated and saturated soil zone requires the collection of a broad range of physical and chemical parameters. Two of the test sites shall serve the long-term observation of the gas composition of soil air and groundwater. A further test site shall in the first place enable the investigation of the so far hardly systematically studied phenomenon of groundwater degassing. Finally, the fourth test site shall be installed in a tropical climate region, in order to investigate the effect of enhanced precipitation and biological activity in the soil.The systematically collected data shall in the first place enable an assessment of the applicability and if appropriate an extension of currently discussed models for the noble gas concentrations in groundwaters. These models are of fundamental significance for the method of noble gas thermometry, but also important for the application of gas tracers for groundwater dating. Beyond this field of application, the results of this study are important for a better understanding of the gas-related biogeochemical and physical processes in the subsurface. Hence the study is related to a wide research field of practical relevance, especially with regard to gas reactions and transport at contaminated sites and during remediation measures.