• Transactions of the Korean hydrogen and new energy society
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• v.18 no.2
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• pp.197-206
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• 2007

There are several methods for the hydrogen production such as steam reforming of natural gas, photochemical method, biological method, electrolysis and thermochemical method, etc. Many researches have been widely performed for the hydrogen production method having low production cost and high efficiency. In this paper, the patents concerning the photochemical hydrogen production method were gathered and analyzed. The search range was limited in the open patents of USA(US), European Union(EP), Japan(JP), and Korea(KR) from 1996 to 2005. Patents were gathered by using key-words searching and filtered by filtering criteria. The patent application trend was analyzed by the years, countries, companies, and technologies.

• Journal of Environmental Science International
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• v.14 no.8
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• pp.749-760
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• 2005

This study examines the local ozone photochemistry in the urban air. The photochemical formation and destruction of ozone was modeled using a photochemical box model. For the model prediction of ozone budget, measurements were carried out from an urban monitoring station in Seoul ($37.6^{\circ}N,\;127^{\circ}E$), Korea for intensive sampling time period (Jun. $1\~15$, 2003). Photochemical process is likely to play significant role in higher ozone concentrations during the sampling period. The results of model simulation indicated that photochemical ozone production pathway was the reaction of NO with $HO_2$ while ozone destruction was mainly controlled by a photochemical destruction pathway, a reaction of $H_2O$ with $O(^1D).$ The contribution of NMHCs to formation and destruction of ozone in the urban was significant. This was entirely different from remote marine environment. The rates of net photochemical ozone production ranged from 0.1 to 1.3 ppbv $h^{-1}$ during the study period.

• Journal of Environmental Science International
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• v.11 no.6
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• pp.497-506
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• 2002

A Photochemical-Trajectory model was used to understand the production of ozone in the atmospheric boundary layer. This model was composed of the trajectory and the photochemical models. To calculate trajectories of air parcels, winds were obtained from the three-dimensional nonhydrostatic mesoscale model (PSU/NCAR MM5V2), and the results were interpolated into constant height surfaces. Numerical integration in the trajectory model was performed by the Runge-Kutta method. The photochemical model consisted of chemical reactions and photodissociation processes. Chemical equations were integrated by the semi-implicit Bulirsch-Stoer method. We performed our experiments from 21 July to 23 July 1994 during the summer time for Seoul area. During the time of maximum ozone concentration in Seoul, four trajectories of air parcels which traveled from Inchon to Seoul were selected. Ozone concentrations estimated by two models are compared with observed one in Seoul area and the photochemical-trajectory model is better fitted than pure photochemical model. During the selected period, high ozone concentrations in Seoul area were more influenced by transferred pollutants from Inchon than emitted pollutants in Seoul.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.2
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• pp.161-176
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• 2010

We examined high ozone episodes observed during the intensive measurement periods (11 May~21 June and 30 July~11 August 2009) in the Gulf of Gwangyang. During that period, there were a few events (or days) in which 1 hr averaged ozone concentrations were greater than 100 ppbv. The analysis of ozone budget and photochemical characteristics related to the ozone production was carried out using a photochemical box model. Ozone sensitivity to $NO_x$ and VOCs was also examined in the study area during the measurement period. Diurnal variation of ozone during the episodes was similar to that of odd hydrogen radicals ($HO_2,CH_3O_2$, and $RO_2$), suggesting significant correlation with photochemical production of ozone during the episodes. In general, ozone concentration in the study area during the measurement period was sensitive to VOCs, whereas ozone was sensitive to $NO_x$ under certain conditions. Ozone sensitivity assessment using a radical budget analysis and $NO_x$/VOCs-control strategy was consistent with that using indicator species ($H_2O_2/HNO_3$ ratio).

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.2
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• pp.118-136
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• 2010

Photochemical characteristics of ozone ($O_3$) and its precursors such as $O_3$ budget and $O_3-NO_x$-VOC sensitivity were analyzed in different physico-chemical properties of air masses around the Mexico City Metropolitan Area (MCMA) using aircraft observations during March 2006. The physico-chemical properties of air masses were categorized into 5 groups: boundary layer (BL), biomass burning (BB), free tropospheric continent (FTCO) and marine (FTMA), and Tula industrial complex (TIC). Results from the $O_3$ budget analysis indicated that $O_3$ production for BL, FTCO, and FTMA (for BB and TIC) was mainly controlled by a photochemical production pathway, a reaction of NO with $HO_2$ (with $RO_2$), while the main pathway of photochemical $O_3$ destruction for BL, FTCO, and FTMA (for BB and TIC) was a reaction of $HO_2$ with $O_3$ (of $H_2$ with $O^1$(D)). In addition, most of air mass categories (especially FTCO) were estimated to be $NO_x$-sensitive for $O_3$ production with lower $NO_y$, higher ratios of the other indicator species (e.g., $O_3/(NO_y-NO_x$), $H_2O_2/HNO_3$, etc.), and the lower removal rate of radicals ($\leq$0.5) by the reaction of OH with $NO_2$ than those of the VOC-sensitive condition.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.66-66
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• 2022

• Journal of Environmental Science International
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• v.16 no.1
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• pp.1-8
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• 2007

Atmospheric photochemistry of $O_3-NOx-RH$ were considered theoretically, to clarify the reasons for the different trends of between the formation of photochemical oxidants (Ox) and its primary pollutants for the Low-and High-NOx regimes. Equations of OH, $HO_2$, and production of ozone ($O_3$) as a function of nitrogen oxides (NOx) and reactive hydrocarbons (RH) were represented in this study. For the Low-NOx regime, $HO_2$ radical is proportional to RH but independent of NOx. OH radical is proportional to NOx but inversely-proportional to RH. $O_3$ production is proportional to NOx but has a weak dependence on RH. For the High-NOx regime, OH and $HO_2$ radicals concentrations and $O_3$ production are proportional to RH but inversely-proportional to NOx. In addition, the Osaka Bay and surrounding areas of Japan were evaluated with the mass balance of odd-hydrogen radicals (Odd-H) using CBM-IV photochemical mechanism, in order to distinguish the Low- and High-NOx regimes. The Harima area (emission ratio, RH/NOx = 6.1) was classified to the Low-NOx regime. The Hanshin area (RH/NOx = 3.5) and Osaka area (RH/NOx = 4.3) were classified to the High-NOx regime.

• Transactions of the Korean hydrogen and new energy society
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• v.4 no.2
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• pp.5-15
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• 1993

Hydrogen production in visible light with the following semiconductor systems, $CdS-WO_3$, $CdS-TiO_2$, have been investigated in the presence of redox catalyst (Pt, $RuO_2$). MeOH, EtOH, isopropanol, sulfide/sulfite mixture, lactic acid were used as sacrifical reagents. The optimal condition for $H_2$ evolution was found to be in qgueous lactic acid media for $CdS-WO_3/RuO_2$. The photochemical efficiency for this system was 1.05 % and the $H_2$ evolution rate was 26.5ml/min. at $6.07{\times}10^{-5}$ einstein/sec photon rate

• Journal of Environmental Health Sciences
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• v.34 no.1
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• pp.62-69
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• 2008

The life cycle assessment method for environmental impact assessment was used, in this study, to assess the production process of wheat flour which is the most important material in the food industry. Environmental impact assessments were compared between that of the Ministry of Environment, Republic of Korea (method I) with that of the Ministry of Commerce, Industry and Energy (method II). Life cycle inventories (LCI) was performed using internal and external databases and the production statistics database of company S. The procedure of life cycle impact assessment (LCIA) was followed in terms of classification, characterization, normalization and weighting to identify the key issues. The impact categories of method I were divided into 8 categories with consideration of : abiotic resources depletion, global warming, ozone depletion, photochemical oxidant creation, acidification and eutrophication. The impact categories of method II were divided into 10 categories with consideration of: abiotic resources depletion, global warming, ozone depletion, photochemical oxidant creation, acidification, eutrophication, human toxicity, freshwater aquatic ecotoxicity, marine aquatic ecotoxicity and terrestrial ecotoxicity.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.1
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• pp.50-62
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• 2011

Temporal trends and spatial distributions of ozone concentrations in Pohang were investigated using data measured at 4 air quality monitoring stations (i.e., Daedo, Jukdo, Jangheung, and Desong) during 2002-2006. The monthly mean ozone concentrations were highest during April and June and decreased during July and August, which follows the typical trend in the Northeast Asia region. The high springtime ozone concentration might have been strongly influenced by the enhanced photochemical ozone production of accumulated precursors during the winter under increased solar radiations. In July and August, ozone levels were decreased by frequent and severe precipitation that caused lower mean monthly solar radiation and efficient wash-out of ozone precursors. This suggests that precipitation is extremely beneficial in the aspect of ozone pollution control. High ozone concentrations exceeding 80ppb dominantly occurred in May and June during the late afternoon between 16:00~17:00. Ozone concentrations were higher in Jangheung and Daesong relative to Daedo and Jukdo, whereas total oxidants $(O_3+NO_2)$ were higher in Jangheung and Daedo. In the suburban area of Daesong, ozone concentrations seem to be considerably higher than those in urban sites of Daedo and Jukdo due to lower ozone loss by NO titration with lower local NO level.