• Journal of Korean Society for Atmospheric Environment
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• v.33 no.5
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• pp.480-496
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• 2017

CMAQ (Community Multiscale Air Quality)-HDDM (High-order Direct Decoupled Method) simulations with MICS-Asia 2010 and INTEX-B 2006 emissions inventories were performed to investigate the impact of Chinese $NO_x$ and VOC emissions on 1-hr ozone concentrations over South Korea during May to July in 2014. Chinese $NO_x$ and VOC emissions in MICS-Asia 2010 were 60% higher and 100% lower than those in INTEX-B 2006 during the simulation period. It makes the ratio of Chinese VOC to $NO_x$ emissions in INTEX-B 2006 (Case 1) is 3.2 times higher than that in MICS-Asia 2010 (Case 2). When the observed period mean 1-hr ozone concentration averaged across 106 air monitoring sites in the SMA (Seoul Metropolitan Area) was 37.6 ppb, the modeled values were similar to each other; 37.3 ppb for Case 1, and 40.4 ppb for Case 2. Both cases show that daily maximum 1-hr ZOC (Zero-Out Contribution) of Chinese $NO_x$ and VOC emissions were as high as 55 ppb and 35 ppb for the episode respectively. Correlation coefficients between ZOC of Chinese $NO_x$ and VOC emissions and the SMA daily maximum 1-hr ozone were 0.49~0.69. It indicates that Chinese emissions occasionally affect the SMA daily ozone peaks. On the other hand, Case 2 predicted 7 ppb and 1 ppb higher ZOC of Chinese $NO_x$ and VOC emissions than Case 1, when simulated ozone in the SMA is over 80 ppb. It implies that upwind $NO_x$ emissions would be more important than upwind VOC emissions for the long-range transport of ozone in Northeast Asia.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.2
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• pp.215-224
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• 2004

We report the high concentration episodes for PM$_{10}$, SO$_2$, NO$_2$, and $O_3$ in many urban areas Korea during 2002. The high concentration episodes are identified based on the National Ambient Air Quality Standards and the observations obtained from the Regional Air Monitoring Network composed of approximately 160 air pollution monitoring stations located in a number of major or big cities in South Korea including Seoul, Pusan, Daegu, and Incheon cities. The results show that the twenty cases of high concentration episodes in 2002 consists of both ozone warning episodes (6 cases) and high PM$_{10}$ concentration cases (14 cases), and one half of the latter are found to occur in association with the Yellow Sand (Asian Dust) phenomena. The most outstanding characteristics of the reported episodes are the excessively high levels of maximum PM$_{10}$ concentrations during the Yellow Sand period (i.e., exceeding 3,000$\mu\textrm{g}$/㎥ in April, 2002) and their variable occurrence frequencies across seasons. The high ozone concentration episode days are mainly resulting from both the high photochemical reactions and poor ventilations. The high PM$_{10}$ concentration days during non Yellow Sand periods, however, mostly occurred under the influence of synoptic meteorological conditions such as stagnant or slowly passing high pressure centers, and consequently prevailing weak wind speeds over the Korean peninsula. The overall results of our study thus suggest the importance of both synoptic and local meteorological factors for high concentration levels in the major and/or big cities in Korea.n Korea.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.5
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• pp.598-607
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• 2004

In this study, the effects of two pre-treatment processes were observed prior to membrane filtration: pre-coagulation and pre-ozonation. To compare the effect of two above-mentioned pre-treatments, we adopted the four schemes: first one is direct membrane filtration of river surface water, second one is membrane filtration after pre-coagulation, third one is membrane filtration after pre-ozonation and fourth one is membrane filtration after pre-coagulation and pre-ozonation. There are two exceptional characteristics in applied processes. One is the usage of the MF membrane which has high ozone resisting characteristic. Therefore, ozone resides in membrane module during filtration. The other is adoption of Jet Mixed Separator (JMS) as coagulation-sedimentation process. The change in transmembrane pressure and permeate water quality were also examined. As a result, considering the filtration performance efficiency and permeate water quality, the process composed of filtration with combination of both pre-coagulation and pre-ozonation was proved most effective. The improved efficiency was due to the reduction of loading rate of fouling inducing materials to membrane module by coagulation process as well as variable reactions, such as degradation, particle destabilization and coagulation, occurred by residual ozone in membrane module. The additional effect of pre-coagulation before pre-ozonation is suppression of AOC, one of the by-products induced by ozonation. Therefore, combination of pre-coagulation and pre-ozonation is the effective process to overcome the major de-merit of ozonation i.e. by-products formation.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.6
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• pp.607-623
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• 2000

Major trends of ozone concentration variations in Korea were investigated by using observation data from around 100 stations for the period of 1991∼1997. In addition, important regulating those variations were inferred. Three measures such as the number of days exceeding 80ppb, the 95th percentile of daily maxima, and the annual average concentration were used for the analysis of multi-scale ozone concentration variations. Three areas in the southwest (Sosan, Mokpo, and Cheju) of which monitoring has been operated since 1995 showed the highest annual average concentrations over; this was noted because of the high annual average in the Yosu area in the early 1990s. Large increases in annual average concentrations were observed along the relatively cleaner areas connecting Kangnung and Kwangju(northeast to southwest), in contrast to polluted areas connecting Seoul and Pusan(northeast to southeast). Both the number of exceedance days and the daily maximum concentration were nearly constant in the Greater Seoul Area in spite of interannual flucturations associated with year-to-year changes in air temperature. Within the Greater Seoul Area, all three measures usually showed the same trend; they decreased in the middle and west and increased in the east and northeast. All three measures including the number of exceedance days increased largely at Sillim where the average concentration was high but no exceedance days were recorded in the early 1999s, Nationwide ozone concentration variations appear to be determined by the competitive influence of long-range transport and local urban emissions, Within the city including the Greater Seoul Area, changes in emission which accompany changes in population and in the number if vehicles ( in the process of urban development) were found to be important components of ozone concentration variations.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.8
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• pp.94-101
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• 2005

The silent discharge type ozonizer with three electrodes(central electrode, internal electrode, and external electrode) and one discharge gap(discharge gap between internal electrode and external electrode) has been designed and manufactured. It is a silent discharge type ozonizer for which the AC high frequency voltages applied to the central electrode within vacuum discharge tube and the internal electrode for which the external electrode is a ground Ozone is generated by silent discharge in discharge gap. At the moment, discharge characteristics and ozone generation characteristics were investigated in accordance with vacuum of discharge tube, frequency of AC power source, discharge power of ozonizer, and quantity of supplied oxygen gas. In consequence, ozone characteristics proportional to vacuum of discharge tube and frequency of AC power source. The maximum value of ozone can be obtained 7,700[ppm], 460[mg/h] and 70[g/kwh].

• Journal of Korean Society of Environmental Engineers
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• v.32 no.2
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• pp.209-218
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• 2010

The fifty six components of volatile organic compounds(VOCs) were continuously measured by the hour to see the distributions their of its concentration and the ozone creating contribution of nitric oxides and VOCs in Gamjeon Odor and VOCs Monitoring Network from April to September, 2008. Aromatics occupied 51.3% of VOCs and paraffins, alkanes and olefins came in order. The monthly concentration of VOCs in Gamjeon was high in July and low in September. As for hourly concentration of ozone and nitric oxides, ozone started to increase since 10am having the highest in the daytime, and nitric oxides had the different trend from that of ozone, showing the lowest in the daytime. The photochemical ozone creating potentials(POCPs) of toluene, propane, m/p-xylene, ethylbenzene, and 1,2,4-trimethylbenzene were 30.6%, 10.2%, 9.4%, 7.4% and 5.2% respectively. These five components occupied 62.8% of total POCPs, which means they contributed to the ozone creation mainly. Related with the ozone creating contribution, the ratio of VOCs to NOx was generally under 6 occupied 72.0%, which came under the area coexisting the limit of VOCs. Therefore it is thought that the management of emission source of VOCs is very important for the reduction of ozone.

• Asian Journal of Atmospheric Environment
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• v.6 no.2
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• pp.104-110
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• 2012

We studied the effects of elevated ozone ([$O_3$]) and $CO_2$ concentrations ([$CO_2$]) on the growth and photosynthesis of the hybrid larch $F_1(F_1)$ and on its parents (the Dahurian larch and Japanese larch). $F_1$ is a promising species for timber production in northeast Asia. Seedlings of the three species were grown in 16 open top chambers and were exposed to two levels of $O_3$ (<10 ppb and 60 ppb for 7 h per day) in combination with two levels of $CO_2$ (ambient and 600 ppm for daytime) over an entire growing season. Ozone reduced the growth as measured by height and diameter, and reduced the needle dry mass and net photosynthetic rate of $F_1$, but had almost no effect on the Dahurian larch or Japanese larch. There was a significant increase in whole-plant dry mass induced by elevated [$CO_2$] in $F_1$ but not in the other two species. Photosynthetic acclimation to elevated [$CO_2$] was observed in all species. The net photosynthetic rate measured at the growing [$CO_2$] (i.e. 380 ppm for ambient treatment and 600 ppm for elevated $CO_2$ treatment) was nevertheless greater in the seedlings of all species grown at elevated [$CO_2$]. The high [$CO_2$] partly compensated for the reduction of stem diameter growth of $F_1$ at high [$O_3$]; no similar trend was found in the other growth and photosynthetic parameters, or in the other species.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.3
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• pp.25-34
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• 2001

In this paper, discharge lamp ozonizer(DLO) of a new discharge type using superposition of gaseous electrical discharge for environment improvement was designed and manufactured. DLO is equipped with 3 electrodes(central ground electrode of discharge lamp type internal high voltage electrode of mesh type and external high voltage electrode of spiral type), and it is composed of double gap(gap between discharge lamp and internal electrode, gap between discharge lamp and external electrode). Internal and external electrodes are respectively applied AC high voltage which has 180[$^{\circ}$] phase difference. Ozone is generated by overlaying of each silent discharge which is respectively came from two gaps. At the moment discharge characteristics and ozone generation characteristics of DLO were investigated in accordance with quantity of supplied gas, discharge power and the number of DLO. When ozone generated by DLO was in contact with NO gas, removal characteristics was excellent, so it confirmed that DLO could be used as air environment improvement facility.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.5
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• pp.60-67
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• 2005

The superposed discharge type ozonizer of high ozone concentration using vacuum discharge tube has been designed and manufactured. It consists of three electrodes(central electrode, internal electrode, and external electrode) and one discharge gap(discharge gap between internal electrode and external electrode), is a superposed silent discharge type ozonizer for which the AC high voltages applied to the central electrode within discharge tube and the internal electrode has a $180{[^\circ]}$ phase difference and for which the external electrode is a ground. Ozone is generated by overlapping silent discharge between central electrode and external electrode, and silent discharge between internal electrode and external electrode. At the moment, discharge characteristics and ozone generation characteristics were investigated in accordance with vacuum of discharge tube, discharge power of ozonizer, and quantity of supplied oxygen gas. In consequence, high ozone concentration can be obtained 8840[ppm].

• Journal of Korean Society of Forest Science
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• v.96 no.5
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• pp.551-560
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• 2007

We investigated physiological damages and biochemical alleviation of five species of genus Acer under ozone fumigation in order to assess their tolerant ability against ozone toxicity. At the end of 150 ppb $O_3$ fumigation, photosynthetic characteristics were measured, and chlorophyll contents, malondialdehyde (MDA) and antioxidative enzyme activities were analyzed in the leaves of five maple trees (Acer buergerianum, A. ginnala, A. mono, A. palmatum, and A. palmatum var. sanguineum). The reduction of chlorophyll (chl) a in ozone-exposed plants was 16.8% (A. buergerianum) to 26.7% (A. ginnala) of control plants. For the content of chi b, A. ginnala and A. palmatum var. sanguineum represented the high reduction of 26.3% and 23.6%, respectively. The highest reduction on the chi a:b ratio was observed in the leaves of A. palmatum. The reduction of net photosynthesis in five species varied from 2.4% to 37.6%. Among five species, A. ginnala showed remarkable reduction (37.6%) for net photosynthesis in comparison with control. Carboxylation efficiency differed significantly (P < 0.05) among species and between control and ozone treatment. The reduction of carboxylation efficiency was the highest in the leaves of A. ginnala (44.7%). A. palmatum var. sanguineum showed the highest increase (41.7%) for MDA content. The highest increase of superoxide dismutase (SOD) activity represented in A. palmatum (26.1%) and the increase of ascorbate peroxidase (APX) activity ranged from 16.5% (A. ginnala) to 49.1% (A. palmatum var. sanguineum). A. mono showed the highest increase (376.6%) of glutathione reductase (GR) activity under ozone fumigation and A. buergerianum also represented high increase (42.3%) of GR activity. Catalse (CAT) activity increased in the leaves of A. ginnala, A. palmatun and A. palmatum var. sanguineum under ozone exposure, whereas A. buergerianum and A. mono decreased in comparison with control plants. In conclusion, physiological markers such as chlorophyll content and photosynthesis that responded sensitively to $O_3$ in maple trees were considered as the very important indicators in order to evaluate the tolerance against $O_3$ stress, and parameters were closely related with each other. Among anti oxidative enzymes, SOD and APX might be contributed to alleviate to $O_3$ toxicity through the increase of activity in all maple trees. Therefore, these compounds can be used as a biochemical maker to assess the stress tolerance to $O_3$.