탄산가스는 탄소나 그 화합물이 완전연소할 때, 생물이 호흡할 때, 발효 등에 의하여 생성되는 무색, 무취의 기체로 분자식은 CO2(이산화탄소)이며, 분자량은 44, 비중은 공기 1에 대하여 1.529이다. 식물은 탄산가스와 물을 원료로 태양에너지를 이용하여 탄수화물을 합성하므로 탄산가스는 광합성에 절대적으로 필요하며, 탄산가스가 충분하게 공급되지 않으면 광합성이 원활하게 이루어질 수가 없다. 일반적으로 식물은 대기중의 농도(0.03%)보다 높은 농도에서 포화점을 갖고 있으므로 대기중에서의 탄산가스의 농도는 식물의 광합성작용에 충분하지 못하며, 생육촉진을 위해서는 인위적인 방법으로 탄산가스 농도를 증가시키는 방법이 실용화되고 있다.(중략)

Carbon dioxide enrichment for greenhouse crops has generally been a standard commercial practice for many years. Vegetable crops such as tomato, cucumber, and lettuce respond positively to the CO2 enrichment. But improper CO2 enrichment leads to physiological damage and economical loss. This study was carried out to develop a CO2 concentration control algorithm considering growth stage and efficiency. The measurand was CO2 consumption rate and top fresh weight that represents growth stage. The weight of top fresh lettuce as a whole in the tray was measured through a non-destructive method. The demand in CO2 concentration according to growth stage was investigated. The results are summarized as follows. 1. The CO2 consumption rate could be measured within the error of ± 15.4mgCO2/hr in the range of CO2 concentration of 500-1500ppm. 2. The weight of top fresh lettuce could be measured within the error ± 4.3g in the range of 0-1400g. 3. The CO2 control model developed could determine an economical CO2 supply rate considering CO2 consumption rate and leakage rate. 4. The CO2 control algorithm based on the control model was composed of feedforward control for maintaining a stable CO2 concentration level, and feedback control with CO2 consumption rate and top fresh weight for adapting to the change in CO2 demand by growth stage. 5. For the performance test with the developed control algorithm on lettuce the decrease in CO2 supply rate was obtained without a significant decrease in top fresh weight.

레이저빔에 의한 철강재의 Ti 표면합금화에 미치는 C함량의 영향을 관찰하였다. 철강재상에 Ti 코팅 후 레이저빔 조사시 질소를 취입가스로 사용하면 부분적으로 TiN과 Fe2Ti가 형성된다. 저탄소강의 경우 Ti함량의 증가에 따라 임계냉각 속도의 증가로 마르텐사이트화가 억제된다. 고탄소강의 경우 Ti의 함량이 1.5%정도 임에도 훼라이트 조직이 형성되지 않고 마르텐사이트 조직이 형성되어 경화된다. 그리고 고탄소강의 Ti 표면합금층 형성에 부분적인 TiC의 석출이 있어 더욱 경도를 증가시키는 것으로 생각된다.

Carbon 14 (14C) is radioactive isotope of carbon which emits beta ray with long half-life (5730±30 years). Since the 14C is significantly hazardous for human being, the appropriate process to treat 14C is necessary. From the nuclear power plant, the ion exchange resin, graphite, and activated carbon are the main source of 14C. During the effort to reduce the volume of those wastes, the 14C is inevitably occurred as carbon dioxide (CO2) form, so called 14CO2. Thus, the development of technology to permanently capture and safely dispose 14CO2 is required. In this presentation, we introduce the decommissioning technology ranging from 14CO2 capture to solidification. First, the new class of glass adsorbent is developed which can irreversibly capture CO2 even under mild conditions. This material promotes the dissolution of alkaline earth ions due to the unstable glass structure. Then, the physical and chemical optimization of glass adsorbent enhances the performance of CO2 capture. Further, room temperature geopolymeric solidification is also performed to safely dispose 14C without any potential release.

Nuclear power plants use ion exchange resins to purify liquid radioactive waste generated while operating nuclear power plants. In the case of PHWR, ion exchange resins are used in heavy water and dehydration systems, liquid waste treatment systems, and heavy water washing systems, and the used ion exchange resins are stored in waste resin storage tanks. The C-14 radioactivity concentration in the waste resin currently stored at the Wolseong Nuclear Power Plant is 4.6×106 Bq/g, exceeding the low-level limit, and if all is disposed of, it is 1.48×1015 Bq, exceeding the total limit of 3.04×1014 Bq of C-14 in the first stage disposal facility. Therefore, disposal is not possible at domestic low/medium-level disposal facilities. In addition, since the heavy water reactor waste resin mixture is stored at a ratio of about 20% activated carbon and zeolite mixture and about 80% waste resin, mixture extraction and separation technology and C-14 desorption and adsorption technology are required. Accordingly, research and development has been conducted domestically on methods to treat heavy water waste resin, but the waste resin mixture separation method is complex and inefficient, and there are limitations in applying it to the field due to the scale of the equipment being large compared to the field work space. Therefore, we would like to introduce a resin treatment technology that complements the problems of previous research. Previously, the waste resin mixture was extracted from the upper manhole and inspection hole of the storage tank, but in order to improve limitations such as worker safety, cost, and increased work time, the SRHS, which was planned at the time of nuclear power plant design, is utilized. In addition, by capturing high-purity 14CO2 in a liquid state in a high-pressure container, it ensures safety for long-term storage and is easy to handle when necessary, maximizing management efficiency. In addition, the modularization of the waste resin separation and withdrawal process from the storage tank, C-14 desorption and monitoring process, high-concentration 14CO2 capture and storage process, and 14CO2 adsorption process enables separation of each process, making it applicable to narrow work spaces. When this technology is used to treat waste resin mixtures in PHWR, it is expected to demonstrate its value as customized, high-efficiency equipment that can secure field applicability and safety and reflect the diverse needs of consumers according to changes in the working environment.

An accumulation of spent nuclear fuel (SNF) has brought a considerable interest due to its energy and environmental issue. To effectively manage SNF, a pyroprocessing is introduced to separate useful resources from the spent fuels and to manufacture suitable fuels. In head-end process of pyroprocessing, spent fuels are thermally treated to prepare UO2 pellets, where various radioactive gases from SNFs are released during thermal treatment. Within these gases, C-14 as CO2 form is a radioactive fission product which had a long half-life of 5,730 years and emits beta radiation of 0.156 MeV. Generally, current CO2 capturing technologies include adsorption by solid materials, absorption by aqueous solutions, and membrane separation. Among these methods, absorption is an effective approach which traps CO2 effectively and and it is easy to operate at room temperature. In addition, it is highly recommended as immobilizing 14CO2 as CaCO3 formation due to the high thermal and chemical stability, and the relatively low solubility in water. Generally, a double alkali method has been proposed to capture low concentrated 14CO2 from the stream. This method for CO2 capture includes absorption process with NaOH solution and causticization using Ca(OH)2. In this study, CO2 emitted from SNF is captured using double alkali method, and the effects of operating conditions on capturing efficiency were investigated. Furthermore, considering the two-film theory, the effects of trapping conditions on the CO2 absorption performance were examined. The recovered CaCO3 from causticization was collected from the absorbing solution and analyzed.

This study investigates the dynamic effects of economic development, international cooperation, electricity consumption, and political risk on the escalation of CO2 emission in Vietnam. We adopted autoregressive distributed lag model and Granger causality method to examine the interaction between CO2 and various economic and political factors, including foreign direct investment, trade openness, economic growth, manufacture, electricity consumption, and political risk in Vietnam since the economic revolution in 1986. The findings reflect opposite influence between these factors and the level of CO2 in the intermediate and long-term durations. Accordingly, foreign direct investment and CO2 emission have a bidirectional relationship, in which foreign direct investment accelerates short-term CO2 emission, but reduces it in the long run through an interactive mechanism. Moreover, economic development increases the volume of CO2 emission in both short and long run. There was also evidence that political risk has a negative effect on the environment. Overall, the findings confirm lasting negative environmental effects of economic growth, trade liberalization, and increased electricity consumption. These factors, with Granger causality, mutually affect the escalation of CO2 in Vietnam. In order to control the level of CO2, more efforts are required to improve administrative transparency, attract high-quality foreign investment, and decouple the environment from economic development.

Purpose: The present study examines the effects of tourism on carbon dioxide emissions for selected South Asian economies over the time from 1995 to 2016. Research design, data and methodology: The present study is an annual time series analysis of tourism and CO2 emissions. The data is taken from World Development Indicators, an official data bank of World Bank. The study sample covers four South Asian countries, namely Bangladesh, India, Pakistan, Sri Lanka and Nepal. The empirical analysis is conducted by employing Pedroni panel cointegration, Fully Modified OLS, and Dynamic OLS approaches of estimation. Results: Tourism significantly increases environmental degradation in selected South Asian economies. The empirical estimated results indicate, that 1 % increase in tourism related activities leads to 0.16 % increase in CO2 emissions. In addition energy consumption and GDP are also causing an upsurge in CO2 emissions in the selected panel of South Asian economies. As the empirical results indicate that 1% increase in GDP stimulates carbon dioxide emissions by 0.23%. Conclusion: In order to protect the environment, the study emphasizes that sustainable tourism practices need to be promoted in the selected South Asian countries. Policy implication and provided and discussed.

Seasonal changes in the CO2 fixation rate and water-use efficiency in the leaves of six evergreen and two deciduous broad-leaved tree species on Jeju Island, Korea, were measured using a portable photosynthesis analyzer, to identify which species are most efficient in taking up CO2 from the air. The CO2 fixation rate was high in the deciduous species in spring and summer and decreased in fall, whereas it was high in the evergreen species in summer and fall and decreased in winter. The rate remained high in the deciduous tree Prunus yedoensis from spring to fall (> 7.1 μmol CO2/m2/s) and in two evergreen trees, Castanopsis cuspidata var. sieboldii and Cinnamomum camphora, in summer and fall (7.0 9.9 μmol CO2/m2/s). Therefore, these tree species fix atmospheric CO2 effectively. The water-use efficiency was higher in evergreen species than in deciduous species regardless of the season. Exceptionally, it was high in the deciduous species Zelkova serrata in spring and summer (> 100 μmol CO2/mol H2O), suggesting that Z. serrata is a useful tree for dry conditions due to its tolerance of water stress. The regressions of the CO2 fixation rate versus the evaporation rate and stomatal conductance were linear and non-linear, respectively. This suggests that the stomatal activity of leaves plays an important part in CO2 fixation of plants. In conclusion, C. cuspidata var. sieboldii, C. camphora, and P. yedoensis should be planted along roads or in urban spaces for the greening of cities and mitigation of CO2 concentrations in the air.

본 연구에서는 고온 가열된 시멘트 페이스트에 나타나는 균열을 CO2 가스 노출을 통한 회복 거동에 대해 관찰하였다. 시 험체는 W/C 40 %의 시멘트 페이스트로 설정하였다. 전기가열로를 목표온도까지 도달시킨 후 가열로 상부에 부착하여 일면 가열을 실시한 후 가열된 면에 나타난 균열을 고배율 카메라로 촬영하였다. 촬영결과 CO2 가스 노출을 통한 회복 재령으로 인하여 시멘트 페이스트의 균열이 더 이상 진행되지 않은 것을 관찰하였다.

This research investigated the characteristics of CO, CO2, and NO2 concentrations at main subway stations in Busan. The annual mean CO concentrations at the Suyeong and Nampo stations were 0.75 ppm and 0.48 ppm, respectively. Annual CO2 concentration at the Seomyeon 1- platform was 649 ppm. The NO2 concentrations at the Seomyeon 2- waiting room and the Yeonsan station were 0.048 ppm and 0.037 ppm, respectively. CO concentration was highest at two times of the day, and was proportional to the number of passengers commuting to and from work. The CO and CO2 concentrations were highest in winter, but NO2 concentration was highest in spring. CO and CO2 concentrations were highest on Saturday and lowest on Sunday. The correlation of CO and NO2 concentrations measured at the subway stations with those at the ambient air quality station were highest at the Seomyeon 1 and 2- waiting room and Jeonpodong. The correlation was lowest at the Yeonsan and Yeonsandong station. The number of days when CO2 concentration exceeded 700 ppm over the last three years at the Seomyeon 1- platform was 174. The findings of this research are expected to deepen understanding of the fine particle characteristics at subway stations in Busan and be useful for developing a strategy for controlling urban indoor air quality.