| 초록 |
Distribution and behavior of baseline soil CO 2 were investigated in a candidate geologic CO 2 storage site in Pohang, with measuring CO 2 concentrations and carbon isotopes in the vadose zone as well as CO 2 fluxes and concentrations through ground surface. This investigation aimed to assess the baseline CO 2 levels and to build the CO 2 monitoring system before injecting CO 2 . The gas in the vadose zone was collected using a peristaltic pump from the depth of 60 cm below ground surface, and stored at gas bags. Then the gas components (CO 2 , O 2 , N 2 , CH 4 ) and #x3B4; 13 C CO2 were analyzed using GC and CRDS (cavity ringdown spectroscopy) respectively in laboratory. CO 2 fluxes and CO 2 concentrations through ground surface were measured using Li-COR in field. In result, the median of the CO 2 concentrations in the vadose zone was about 3,000 ppm, and the #x3B4; 13 C CO2 were in the wide range between #x2212;36.9 #x2030; and #x2212;10.6 #x2030;. The results imply that the fate of CO 2 in the vadose zone was affected by soil property and vegetations. CO 2 in sandy or loamy soils originated from the respiration of microorganisms and the decomposition of C 3 plants. In gravel areas, the CO 2 concentrations decreased while the #x3B4; 13 C CO2 increased because of the mixing with the atmospheric gas. In addition, the relation between O 2 and CO 2 , N 2 , and the relation between N 2 /O 2 and CO 2 implied that the gases in the vadose zone dissolved in the infiltrating precipitation or the soil moisture. The median CO 2 flux through ground surface was 2.9 g/m 2 /d which is lower than the reported soil CO 2 fluxes in areas with temperate climates. CO 2 fluxes measured in sandy and loamy soil areas were higher (median 5.2 g/m 2 /d) than those in gravel areas (2.6 g/m 2 /d). The relationships between CO 2 fluxes and concentrations suggested that the transport of CO 2 from the vadose zone to ground surface was dominated by diffusion in the study area. In gravel areas, the mixing with atmospheric gases was significant. Based on this study result, a soil monitoring procedure has been established for a candidate geologic CO 2 storage site. Also, this study result provides ideas for innovating soil monitoring technologies. |
