Potential source of CO2 emissions to the atmosphere from groundwater use in the Republic of Korea.

Carbon dioxide (CO2) is a major contributor to global warming, with emissions arising from various sources such as fossil fuel combustion, agriculture, and mining. In the Republic of Korea, atmospheric CO2 concentrations and emission flux have been systematically monitored since the 1990s. However, in the republic of Korea, CO2 emissions resulting from groundwater extraction remain largely unrecognized, despite their potential role in facilitating rapid material exchange within isolated subsurface environments. This study aims to evaluate the contribution of isolated CO2 emissions from groundwater extraction and to quantitatively estimate the associated the CO2 flux. Hydrochemical analysis reveal that the dominant water type is Ca-HCO3 type, identified in 343 wells (77.4 %), primarily resulting from water-rock interactions. The calculated partial pressure of CO2 (pCO2) in groundwater averaged 23 μatm, with a range of 0.2 to 362 μatm, with median value of 12 μatm. Based on an annual volume of groundwater extraction in Korea is 2.7 billion m3, the estimated CO2 emissions to the atmosphere to approximately 0.82 billion g/year. Notably, the northeastern karst region of the Korean Peninsula, characterized by a northeast-southwest oriented geological structure, exhibits higher CO2 emissions than the national average. Although this study does not fully account for spatial heterogeneity, future carbon assessments should incorporate more comprehensive evaluation of actual carbon cycling dynamics in subsurface environment.