1. Spatial distribution and origin of soil CO2 in Andeok area, Jeju.
- Author
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Ju, Gahyeun, Lee, Jeong-Ho, Moon, Soohyeon, Song, Minseok, Yu, Soonyoung, Kwon, Chang Woo, Yun, Seong-Taek, and Chae, Gitak
- Subjects
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SOIL air , *SOIL surveys , *SOILS , *SOIL testing , *GLOW discharges - Abstract
CO2 flux measurements and soil gas samples were collected to determine the origin and distribution characteristics of soil gas discharged at Andeok area, Jeju, South Korea. Additionally, this study aims to discuss agricultural activities that may contribute to increased soil CO2 emissions. CO2 flux was measured at 127 points, while soil gas sampling for gas components and carbon-13 (δ13CCO2) analysis was performed at 56 points. The measured CO2 fluxes in the study area ranged from 0.8 to 83.8 g/m2/d (mean: 14.3 g/m2/d), which was lower than CO2 fluxes observed in areas with geogenic CO2 discharge (e.g., near active volcanoes, faults, and CO2-rich water sources). The soil gas analysis revealed that the CO2 concentration and δ13CCO2 ranged from 491 to 23,722 ppmv (mean: 3,205 ppmv) and from −25.2 to −10.7‰ (mean: −19.4‰), respectively. In the cumulative probability diagram, the threshold values for CO2 flux and soil CO2 concentration were 41.3 g/m2/d and 6,693 ppmv, respectively. Samples exceeding the CO2 flux threshold were affected by urea fertilizer application based on land use nearby, and did not overlay with samples exceeding the soil CO2 threshold, indicating different transport mechanisms. Results from a detailed survey near a soil gas sampling location close to high soil CO2 showed that soil CO2 concentrations increased with depth, especially during summer when atmospheric temperatures increased. Spatially, higher soil CO2 concentrations were observed in areas with accumulated plant debris from tangerine orchards. The δ13CCO2 and relationships among CO2-O2, N2-CO2, and N2/O2-CO2 indicated that all collected samples had a biogenic origin. Although geogenic soil gases were not observed in this study, our findings are useful for future research on Jeju Island, as they provide baseline values for distinguishing geogenic soil gas from those with natural and agricultural origins. Moreover, this result provides insights into agricultural activities such as urea fertilization and plowing and their contribution to soil CO2 increase, and inspires future research on negative soil CO2 flux. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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