Soil CO2 Flux Monitoring for Geologic Carbon Storage: Assessing the Background CO2 Levels Prior to Artificial CO2 Release Experiment in Eumsung, Korea

Abstract:

With potential risks of CO₂ leakage and subsequent impacts on surrounding abiotic and biotic environments, development of adequate monitoring strategies is essential for successful geologic carbon storage (GCS). To accomplish such goal, a controlled artificial CO₂ release experiment site has been established in Eumsung, Korea. Prior to the scheduled release in fall 2015 at the depth of 2.5 m, grid measurements of soil CO₂ fluxes at the surface and shallow subsoil CO₂ concentrations at various depths were conducted periodically in order to assess the background soil respiration fluxes. Following the installation of automated soil flux chambers, the mean flux was found to be 2.1 µmol m^-2 s^-1 over the period of June to August 2015. However, as expected, spatial and temporal variations of the CO₂ flux among the chambers were observed, ranging from about 0.5 to 4.0 µmol m^-2 s^-1. In addition, it was found that rainfalls, including few incidents of heavy monsoonal rain, have hindered the collection of reliable data. Spatiotemporal variability of soil CO₂ flux is due to its strong dependence on surrounding soil conditions (i.e. temperature and soil moisture content) and meteorological conditions. Hence by integrating the results obtained by portable accumulation flux chamber method and subsoil CO₂ concentration measurements along with environmental data, we expect to produce a more reliable background value. In addition to expanding the sampling area, subsoil CO₂ concentration measurements at various depths is also expected to provide valuable observations on the evolution and vertical movement of CO₂ through the soil profile to the surface. Carefully assessed background CO₂ flux level, from monitoring over a sufficiently long-term site characterization period and when its spatiotemporal variability is well understood, will be the key to successful leakage detection in GCS facilities.

※ This subject is supported by Korea Ministry of Environment (MOE) as "K-COSEM Research Program".