Comparative study of geophysical and soil-gas investigations at the Hartousov (Czech Republic) natural CO_2 degassing site

摘要

Our study at this natural analog site contributes to the evaluation of methods within a hierarchical monitoring concept suited for the control of CO_2 degassing. It supports the development of an effective monitoring concept for geological CO_2 storage sites-carbon capture and storage as one of the pillars of the European climate change efforts. This study presents results of comprehensive investigations along a 500-m long profile within the Hartousov (Czech Republic) natural CO_2 degassing site and gives structural information about the subsurface and interaction processes in relation to parameters measured. Measurements of CO_2 concentrations and investigation of the subsurface using electrical resistivity tomography and self-potential methods provide information about subsurface properties. For their successful application it is necessary to take seasonal variations (e.g., soil moisture, temperature, meteorological conditions) into consideration due to their influence on these parameters. Locations of high CO_2 concentration in shallow depths are related to positive self-potential anomalies, low soil moistures and high resistivity distributions, as well as high δ13C values and increased radon concentrations. CO_2 ascends from deep geological sources via preferential pathways and accumulates in coarser sediments. Repetition of measurements (which includes the effects of seasonal variations) revealed similar trends and allows us to identify a clear, prominent zone of anomalous values. Coarser unconsoli-dated sedimentary layers are beneficial for the accumulation of CO_2 gas. The distribution of such shallow geological structures needs to be considered as a significant environmental risk potential whenever sudden degassing of large gas volumes occurs.