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pH가 낮은 탄산수의 CO<sub>2</sub> 탈기에 따른 용존탄소동위원소 변화
채기탁,유순영,김찬영,박진영,방하은,이인혜,고동찬,신영재,오진만,Chae, Gitak,Yu, Soonyoung,Kim, Chan Yeong,Park, Jinyoung,Bang, Haeun,Lee, Inhye,Koh, Dong-Chan,Shinn, Young Jae,Oh, Jinman 한국지하수토양환경학회 2019 지하수토양환경 Vol.24 No.3
It is known that ${\delta}^{13}C_{DIC}$ (carbon-13 isotope of dissolved inorganic carbonate (DIC) ions) of water increases when dissolved $CO_2$ degases. However, ${\delta}^{13}C_{DIC}$ could decrease when the pH of water is lower than 5.5 at the early stage of degassing. Laboratory experiments were performed to observe the changes of ${\delta}^{13}C_{DIC}$ as $CO_2$ degassed from three different artificial $CO_2$-rich waters (ACWs) in which the initial pH was 4.9, 5.4, and 6.4, respectively. The pH, alkalinity and ${\delta}^{13}C_{DIC}$ were measured until 240 hours after degassing began and those data were compared with kinetic isotope fractionation calculations. Furthermore, same experiment was conducted with the natural $CO_2$-rich water (pH 4.9) from Daepyeong, Sejong City. As a result of experiments, we could observe the decrease of DIC and increase of pH as the degassing progressed. ACW with an initial pH of 6.4, ${\delta}^{13}C_{DIC}$ kept increasing but, in cases where the initial pH was lower than 5.5, ${\delta}^{13}C_{DIC}$ decreased until 6 hours. After 6 hours ${\delta}^{13}C_{DIC}$ increased within all cases because the $CO_2$ degassing caused pH increase and subsequently the ratio of $HCO_3{^-}$ in solution. In the early stage of $CO_2$ degassing, the laboratory measurements were well matched with the calculations, but after about 48 hours, the experiment results were deviated from the calculations, probably due to the equilibrium interaction with the atmosphere and precipitation of carbonates. The result of this study may be not applicable to all natural environments because the pressure and $CO_2$ concentration in headspace of reaction vessels was not maintained constant as well as the temperature. Nevertheless, this study provides fundamental knowledge on the ${\delta}^{13}C_{DIC}$ evolution during $CO_2$ degassing, and therefore it can be utilized in the studies about carbonated water with low pH and the monitoring of geologic carbon sequestration.
Yu, Soonyoung,Lee, Pyeong-Koo,Yun, Seong-Taek,Hwang, Sang-Il,Chae, Gitak Springer-Verlag 2017 Environmental earth sciences Vol.76 No.9
<P>Volatile organic compounds (VOCs) detected in stormwater were compared with VOCs present in emission sources, air, groundwater, and influent to sewage treatment plants in Seoul to understand their fate and transport in the urban hydrological system. Stormwater is a carrier of non-point source pollutants and contains VOCs from land surfaces and air. Samples of stormwater and influent to sewage treatment plants were collected and analyzed for 61 VOCs, while the VOCs in emission sources, air and groundwater were investigated through literature reviews for comparison. The results showed that the most frequently detected VOCs in stormwater were similar to those in air. However, the atmospheric concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX), and methyl tertiary-butyl ether (MTBE) were too low to explain their frequent detection and high concentrations in stormwater. As a result, land surfaces seem to be a primary source of these VOCs in stormwater. Comparison of the VOCs in stormwater and groundwater showed that toluene and MTBE were frequently detected in both media, but more often and at higher concentrations in stormwater. This finding indicates that stormwater recharge is a source of toluene and MTBE in groundwater. Regarding groundwater, land surfaces seem to be a primary source of toluene, while urban air is the primary source in the case of MTBE. Specifically, the MTBE values in air were sufficiently high to explain its levels in groundwater, which had continually increased and remained low afterward. Furthermore, the high ratios of TEX (toluene, ethylbenzene, and xylenes) to benzene and MTBE in stormwater indicated that TEX had additional sources other than vehicles, most likely hydrocarbon solvents. These solvents seem to be a primary source of TEX and other frequently detected VOCs in stormwater. However, trichloroethylene (TCE), tetrachloroethylene (PCE) and their dechlorination intermediates were far more frequently detected and at higher concentrations in groundwater than in stormwater. Additionally, their concentrations frequently exceeded the water- quality criteria. It seems that halogenated solvents had produced contamination plumes of these chlorinated VOCs in the Seoul aquifer. Based on VOCs detected in Seoul, stormwater was mixed with groundwater in combined sewers and flowed into sewage treatment plants. The results imply that organic solvents should be handled with extreme care to protect groundwater quality.</P>
고압 유체 시료의 pH 및 알칼리도 측정 방법 : 가상 시료를 활용한 실용성 평가
송민석,문수현,채기탁,방준환,Minseok Song,Soohyeon, Moon,Gitak Chae,Jun-Hwan Bang 한국지하수토양환경학회 2024 지하수토양환경 Vol.29 No.1
As part of monitoring technology aimed at verifying the stability of CO<sub>2</sub> geologic storage and mitigating concerns about leakage, a method for measuring the pH and alkalinity of high-pressure fluid samples was established to obtain practical technology. pH measurement for high-pressure samples utilized a high-pressure pH electrode, and alkalinity was measured using the Gran titration method for samples collected with a piston cylinder sampler (PCS). Experimental samples, referencing CO<sub>2</sub>-rich water and CO<sub>2</sub> geologic storage studies, were prepared in the laboratory. The PCS controls the piston, preventing CO<sub>2</sub> degassing and maintaining fluid pressure, allowing mixing with KOH to fix dissolved CO<sub>2</sub>. Results showed a 6.1% average error in high-pressure pH measurement. PCS use for sample collection maintained pressure, preventing CO<sub>2</sub> degassing. However, PCS-collected sample alkalinity measurements had larger errors than non-PCS measurements, limiting PCS practicality in monitoring field settings. Nevertheless, PCS could find utility in preprocessing for carbon isotope analysis and other applications. This research not only contributes to the field of CCS monitoring but also suggests potential applications in studies related to natural analogs of CCS, CO<sub>2</sub>-rock interaction experiments, core flooding experiments, and beyond.
포항 지역 토양 CO<sub>2</sub>의 분포 및 거동 특성 연구: CO<sub>2</sub> 지중저장 부지 자연 배경 조사 및 예비 해석
박진영,성기성,유순영,채기탁,이세인,염병우,박권규,김정찬,Park, Jinyoung,Sung, Ki-Sung,Yu, Soonyoung,Chae, Gitak,Lee, Sein,Yum, Byoung-Woo,Park, Kwon Gyu,Kim, Jeong-Chan 한국지하수토양환경학회 2016 지하수토양환경 Vol.21 No.1
Distribution and behavior of baseline soil CO<sub>2</sub> were investigated in a candidate geologic CO<sub>2</sub> storage site in Pohang, with measuring CO<sub>2</sub> concentrations and carbon isotopes in the vadose zone as well as CO<sub>2</sub> fluxes and concentrations through ground surface. This investigation aimed to assess the baseline CO<sub>2</sub> levels and to build the CO<sub>2</sub> monitoring system before injecting CO<sub>2</sub>. 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<sub>2</sub>, O<sub>2</sub>, N<sub>2</sub>, CH<sub>4</sub>) and δ<sup>13</sup>C<sub>CO2</sub> were analyzed using GC and CRDS (cavity ringdown spectroscopy) respectively in laboratory. CO<sub>2</sub> fluxes and CO<sub>2</sub> concentrations through ground surface were measured using Li-COR in field. In result, the median of the CO<sub>2</sub> concentrations in the vadose zone was about 3,000 ppm, and the δ<sup>13</sup>C<sub>CO2</sub> were in the wide range between −36.9‰ and −10.6‰. The results imply that the fate of CO<sub>2</sub> in the vadose zone was affected by soil property and vegetations. CO<sub>2</sub> in sandy or loamy soils originated from the respiration of microorganisms and the decomposition of C<sub>3</sub> plants. In gravel areas, the CO<sub>2</sub> concentrations decreased while the δ<sup>13</sup>C<sub>CO2</sub> increased because of the mixing with the atmospheric gas. In addition, the relation between O<sub>2</sub> and CO<sub>2</sub>, N<sub>2</sub>, and the relation between N<sub>2</sub>/O<sub>2</sub> and CO<sub>2</sub> implied that the gases in the vadose zone dissolved in the infiltrating precipitation or the soil moisture. The median CO<sub>2</sub> flux through ground surface was 2.9 g/m<sup>2</sup>/d which is lower than the reported soil CO<sub>2</sub> fluxes in areas with temperate climates. CO<sub>2</sub> fluxes measured in sandy and loamy soil areas were higher (median 5.2 g/m<sup>2</sup>/d) than those in gravel areas (2.6 g/m<sup>2</sup>/d). The relationships between CO<sub>2</sub> fluxes and concentrations suggested that the transport of CO<sub>2</sub> 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<sub>2</sub> storage site. Also, this study result provides ideas for innovating soil monitoring technologies.
다채널 지표토양 CO<sub>2</sub> 농도 모니터링(SCM) 시스템 개발 및 적용성 평가 연구
성기성,유순영,최병영,박진영,한래희,김정찬,박권규,채기탁,Sung, Ki-Sung,Yu, Soonyoung,Choi, Byoung-Young,Park, Jinyoung,Han, Raehee,Kim, Jeong-Chan,Park, Kwon Gyu,Chae, Gitak 한국지하수토양환경학회 2015 지하수토양환경 Vol.20 No.1
Monitoring of $CO_2$ release through the ground surface is essential to confirm the safety of carbon storage projects. We conducted a feasibility study of the multi-channel surface-soil $CO_2$-concentration monitoring (SCM) system as a soil $CO_2$ monitoring tool with a small scale injection test. The background concentrations showed the distinct diurnal variation. The negative relation of $CO_2$ with temperature and the low $CO_2$ concentrations during the day imply that surface-soil $CO_2$ depends on photosynthesis and respiration. After 4.2 kg of $CO_2$ injection (1 m depth for 29 minutes), surface-soil $CO_2$ concentrations increased in the all five chambers, which were located less than 2.8 m of distance from each other. The $CO_2$ concentrations seem to be recovered to the background around 4 hours after the injection ended. To determine the leakage, the data from Chamber 2 and 5 with low increase rates were used for statistical analyses. Coefficient of variation for 30 minutes ($CV_{30min}$.) is efficient to determine a leakage signal, with reflecting the fast change in $CO_2$ concentrations. Consequently, SCM and $CV_{30min}$ could be applied for an efficient monitoring tool to detect $CO_2$ release through the ground surface. Also, this study provides ideas for establishing action steps after leakage detection.