• 한국환경과학회지
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• 제15권5호
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• pp.479-484
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• 2006

Removal of elemental mercury $(Hg^0)$ with the reactive species produced from dielectric barrier discharge (DBD) was studied. We investigated the effect of operating parameters such as the applied voltage, residence time, initial concentration and co-existence of other pollutants. The removal of $(Hg^0)$ was significantly promoted by an increase in the applied voltage of the DBD reactor system. It is important to note that at the same input power, the removal efficiency of $(Hg^0)$ was much higher than that of NO gas. These results imply that if the DBD system is used as a NOx treatment facility, it is capable of removing $(Hg^0)$ simultaneously with NOx.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2007년도 추계학술대회 논문집
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• pp.290-291
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• 2007

• 한국대기환경학회지
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• 제13권6호
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• pp.439-450
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• 1997

Atmospheric fine particles $(PM_{2.5})$ were collected at the background sites, Kangwha, Taean, and Kosan and characterized to understand their behaviors at the sites. Daily samples of $PM_{2.5}$ mass were measured and ionic species, carbonaceous species, and gaseous species were analyzed. Four-day backward trajectory analysis was also carried out. The mean concentrations of anthropogenic species were highest at Kangwha among three sites, while contributions from sea salts wree highest at Taean during the measurement period due to higher wind speed at Taean. Major chemical components in fine particles were sulfate, organic carbon, nitrate, and ammoniu. Most of the non-sea-salt (nss) sulfates in $PM_{2.5}$ might be present as ammonium sulfates at these sites. Most air parcels arriving at Kangwha and Taean were from northern China. Therefore, both sites were thought to be affected by the same air parcel. At Kosan, during the measurement period, air parcels were from either northern China or sourthern China. The nss sulfate concentration in the air parcels from southern China was higher, while the nss calcium, nitrate, and ammonium concentrations were higher when the air parcels were from northern China.

• 한국대기환경학회지
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• 제21권1호
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• pp.15-26
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• 2005

An experimental investigation of the gas-phase photooxidation of toluene-NO$_{x}$-air mixtures at sub-ppm concentrations has been carried out in a 6.9 m3, indoor smog chamber irradiated by blacklights. Measured parameters in the toluene-NO$_{x}$ experiments included $O_3$, NO, NO$_2$, NO$_{x}$, CO, SO$_2$ toluene, and air temperature. The initial toluene concentration ranged from 225 ppb to 991 ppb and the initial concentration ratio of toluene/NO$_{x}$ in ppbC/ppb was in the range of 5～20. It was found that the variation of gaseous species with irradiation time caused by the photooxidation of toluene-NO$_{x}$-air mixtures depended on the initial toluene concentration for similar concentration ratio of toluene/NO$_{x}$. The dependency of initial toluene concentration on the photooxidation of toluene-NO$_{x}$-air mixtures for toluene/NO$_{x}$=5～6 seemed to be opposite to that for toluene/NO$_{x}$=10～11. The arriving time at maximum ozone concentration depended on both initial toluene concentration and initial concentration ratio of toluene/NO$_{x}$. However, the maximum concentration of ozone formed by photooxidation depended only on the initial toluene concentration.luene concentration.

• 한국환경과학회지
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• 제16권4호
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• pp.433-440
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• 2007

The photodegradation and by-products of the gaseous toluene with $TiO_2$ (P25) and short-wavelength UV ($UV_{254+185nm}$) radiation were studied. The toluene was decomposed and mineralized efficiently owed to the synergistic effect of photochemical oxidation in the gas phase and photocatalytic oxidation on the $TiO_2$ surface. The toluene by the $UV_{254+185nm}$ photoirradiated $TiO_2$ were mainly mineralized $CO_2$ and CO, but some water-soluble organic intermediates were also formed under severe reaction conditions. The ozone and secondary organic aerosol were produced as undesirable by-products. It was found that wet scrubber was useful as post-treatment to remove water-soluble organic intermediates. Excess ozone could be easily removed by means of a $MnO_2$ ozone-decomposition catalyst. It was also observed that the $MnO_2$ catalyst could decompose organic compounds by using oxygen reactive species formed in process of ozone decomposition.

• 한국대기환경학회지
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• 제19권2호
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• pp.167-177
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• 2003

The number size distribution of urban aerosols ranging from 0.02 to 20 ${\mu}{\textrm}{m}$ in diameter was measured by using a scanning mobility particle sizer (SMPS) system and an aerodynamic particle sizer spectrometer (APS) at Seoul from November 30,2001 to January 14, 2002. The gaseous species such as CO, NO, NO$_2$, and $O_3$ were also continuously monitored. The daily average concentration of urban aerosols sorted into three groups (0.02~0.1 ${\mu}{\textrm}{m}$, 0.1~1 ${\mu}{\textrm}{m}$ and 1~10 ${\mu}{\textrm}{m}$) and the typical number, surface, and volume distributions of urban aerosols were discussed in this paper. The weekly variation of aerosol concentration was compared with those of gaseous concentrations. relative humidity, and visibility. The results showed that the particle number concentration seemed to increase in the morning and the number concentration of fine particles less than 1 fm in diameter seemed to increase when the concentrations of CO, NO, and NO$_2$ were high. The number concentration of fine particles was relatively high when the relative humidity was greater than 70％ during the increasing period of relative humidity. The visibility was weakly correlated with the concentration of aerosols ranging 0.1 to 1 ${\mu}{\textrm}{m}$, and the number size distribution for high visibility episode was apparently different from that for low visibility episode.

• 한국대기환경학회지
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• 제12권1호
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• pp.91-99
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• 1996

Ozone, sulfur dioxide, and nitrogen oxides were measured at Kosan, Cheju Island, Korea during the period of March 11 .sim. April 19, 1994. During the measurement period, the average SO$_{2}$ and NOx concentrations were about 0.97 ppb and 3.5 ppb, respectively. Average NO concentration was below the detection limit and thus the effect of NO during the period was negligible. The concentrations of SO$_{2}$ and Nox were lower than those at other urban area in Korea but higher than other remote areas in the world. Average $O_{3}$ concentration for the period was about 55 ppb, slightly higher than or comparable to those at remote marine areas in the world. Detailed analyses of trend of gaseous species concentrations show that the effects of local NO emission sources for NOx concentration were significant during the period, while those of local SO$_{2}$ emission sources were not high. Backward trajectory analysis results show that when SO$_{2}$ or $O_{3}$ concentration was higher than the average concentrations, the air parcels were transported from China.

• Environmental Analysis Health and Toxicology
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• 제12권3_4호
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• pp.43-54
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• 1997

Species, doses and routes extrapolation can be sucessfully carried out by using a physiologically-based pharmacokinetic (PBPK) approach. And PBPK approach to assess risk of hazardous chemicals is reasonable whatever the exposure scenarios are happened. Both partitioning coefficients of chemical between tissue and blood and enzymatic metabolic rate constants are key parameters to build up the PBPK model. In this study, we tried to estimate in vitro metabolic rate constants using a special apparatus instead to measure the in vivo constants which are used to PBPK simulation since the in vitro tests are less expensive and more convenient than in vivo tests. For the purpose, we designed and tested the new system to measure continuously the headspace concentration of VOC. The newly designed system is composed with a diffusion chamber which generates gaseous substrate, a reaction vessel with a recirculating pump to establish a closed system, an autbmatic sampler from a gas phase, a gas chromatography to analyze the headspace. In addition, a cold water condenser is attached between the reaction vessel and pump to reduce the content of gaseous moisture which interferes with chemical analysis. To validate the newly developed methodology, in vitro metabolic rate constants of trichloroethylene (TCE) as a prototype VOC were estimated by simulating observed results with an ACSL program. The simulated results are consistent to those estimated by the other research groups. This finding suggests that our newly designed closed system may be a useful apparatus to estimate in vitro metabolic rate constants for VOC.

• 한국안전학회지
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• 제10권3호
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• pp.68-80
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• 1995

A series of parametric calculations have been performed in order to investigate the short-term and short-range plume and puff behavior of toxic gaseous and solid pollutant dispersion in an open atmosphere. The simulation is made by the use of the computer program developed by this laboratory, in which a control-volume based finite-difference method is used together with the SIMPLEC algorithm for the resolution of the pressure-velocity coupling appeared In Wavier-Stokes equation. The Reynolds stresses are solved by the standard two-equation k-$\varepsilon$ model modified for buoyancy together with the RNG(Renormalization Group) k-$\varepsilon$ model. The major parameters considered in this calculation are pollutant gas density and temperature, the relative velocity of pollutants to that of the surrounding atmospheric air, and particulate size and density together with the height released. The flow field is typically characterized by the formation of a strong recirculation region for the case of the low density gases such as $CH_4$ and air due to the strong buoyancy, while the flow is simply declining pattern toward the downstream ground for the case of heavy molecule like the $CH_2C1_2$and $CCl_4$, even for the high temperature, $200^{\circ}C$. The effect of gas temperature and velocity on the flow field together with the particle trajectory are presented and discussed in detail. In general, the results are physically acceptable and consistent.

• 방사성폐기물학회지
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• 제16권1호
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• pp.11-39
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• 2018

Tritium and $^{14}C$ are two most important radionuclides released from nuclear facilities to the environment, and $^{14}C$ contributes dominant radiation dose to the population around nuclear power plants. This paper presents an overview of the production, pathway, species and levels of tritium and $^{14}C$ in nuclear facilities, mainly nuclear power plants. The methods for sampling and collection of different species of tritium and $^{14}C$ in the discharge gas from the stack in the nuclear facilities, atmosphere of the nuclear facilities and environment are presented, and the features of different methods are reviewed. The on-line monitoring methods of gaseous tritium and $^{14}C$ in air and laboratory measurement methods for sensitive determination of tritium and $^{14}C$ in collected samples, water and environmental solid samples are also discussed in detailed. Meanwhile, the challenges in the determination and speciation analysis of tritium and $^{14}C$ are also highlighted.