• Journal of Korean Society for Atmospheric Environment
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• v.19 no.E3
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• pp.129-136
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• 2003

Effects of inorganic aerosols on the kinetics of the hydroxyl radical reactions with selected aliphatic alkanes have been investigated using the relative rate technique. The relative rates in the absence and presence of aerosols were determined for n-butane, n-pentane, n-hexane, n-octane, and n-decane. P-xylene was used as a reference compound. Inorganic aerosols including (NH$_4$)$_2$SO$_4$, NH$_4$NO$_3$, and NaCl aerosols at two different aerosol concentrations that are typical of polluted urban conditions were tested. Total surface areas of aerosols were 1400 (Condition I) and 3400 $\mu$$m^2$ cm$^{-3}$ (Condition II). Significant changes in the relative rates in the presence of the inorganic aerosols were not observed for the n-butanel/$.$OH, n-pentanel/$.$OH, n-hexanel/$.$OH, n-octanel/$.$OH, and n-decanel/$.$OH reactions versus p-xylenel/$.$OH reaction. These results suggest that the promoting effects depend on the semiconducting property of the aerosols and the nature of the organic compounds.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.6
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• pp.758-766
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• 2006

A two-stage bioreactor, which consists of a biotrickling filter module and a biofilter module in series, was investigated for the enhanced treatment of a VOC mixture, toluene and methyl ethyl ketone (MEK). Throughout the experiments, the overall inlet loading rate was maintained at approximately $43g/m^3/hr$, but the inlet ratios of the VOCs were modified. The experimental results showed that the different ratios of the VOC mixture resulted in changes of overall removal efficiencies, elimination capacities (ECs) and microbial accumulation on the surface of each packing material. The ratio of inlet toluene to MEK at 50 : 150 was found to be most effective in terms of the overall removal efficiency, because, at this condition, MEK (i.e., the hydrophilic compound) was mostly removed in the biotrickling filter module and the following biofilter module was used to remove toluene. It was also found that when the inlet loading rate of the VOC mixture was serially increased stepwise within short-term periods, the ECs for toluene dropped significantly but the ECs for MEK increased at the ratio of the VOC mixture. These results implied that substrate interaction and/or substrate preferable utilization might have an effect on the biological removal of each compound in the two-stage bioreactor; therefore, the bioreactor should be operated in the condition where the substrate interaction could be minimized in order to maximize overall performance of the two-stage bioreactor.

• Journal of Korean Society for Atmospheric Environment
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• v.13 no.4
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• pp.249-256
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• 1997

To identify the long-term influence of acid rain treatment on tree growth, acid rain of various composition (pH 2.0, pH 4.0 and pH 5.6 as control) was applied to several landscape trees for five months (April through August, 1991). Tree height, pH values and $Al^{3+}$ concentration in soil were investigated. Acid rain treatments seemed to promote height growth in the first year (1991), but have become an inhibiting factor over five years. All of coniferous species and most broad-leaved species, except Acer ginnala, showed opposite trends in height responses to acid rain treatments between the first (1991) and last (1996) year. In contrast, Acer ginnala showed similar trends to acid rain treatments in the height growth between 1991 and 1996. This result suggested that Acer ginnala has a characteristic adapability to acid rain stress. pH values of surface soil were lower than those of 30 cm soil depth. This fact suggested that acid rain treatments made surface soil acidic condition. In addition, physiological characteristics (photosynthesis, stomatal condition and biomass) have to be investigated to identify the relationship between long-term effects of $AL^{3+}$ concentration and growth.

• Ocean and Polar Research
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• v.30 no.4
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• pp.453-466
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• 2008

In order to examine the generation mechanism of long ocean waves along the west coast of Korea and to understand the amplification process of the long ocean waves, sea level, atmospheric pressure and wind data observed every minute from 2007 March 29 to 2007 April 1 were analyzed and onedimensional numerical ocean model experiments were performed. An atmospheric pressure jump propagated southeastward from Backryungdo to Yeonggwang along the west coast of Korea with speed of $13{\sim}27\;m/s$ between 2007 March 30 23:00 and 2007 April 1 1:30. Average magnitude of pressure jump was 4.2 hPa. As a moving atmospheric jump propagated from north to south along the coast, long ocean waves were generated and the sea level abnormally rose or fell at Anheung, Kunsan, Wido and Yeonggwang. Average amplitude of sea level rise (or fall) was about 113.6 cm. In a one-dimensional numerical ocean model, nonlinear shallow water equations were numerically integrated and a moving atmospheric pressure jump with traveling speed of 24 m/s was used as an external force. While the atmospheric pressure jump travels over 60 m depth ocean, a long ocean wave is generated. Because the propagation speed of the atmospheric jump is almost equal to that of the long ocean wave, Proudman resonance occurs and the long ocean wave amplifies. As the atmospheric pressure jump moves into the coastal area shallower than 60 m, the speed of the long ocean wave decreases and Proudman resonance effect decreases. However, the amplitude of the long ocean wave increases and wave length becomes shorter because of shoaling effect. When the long ocean wave hits the land boundary, amplitude of the long ocean wave drastically amplifies due to reflection. Data analysis and numerical experiments suggest that the southeastward propagation of an atmospheric pressure jump over the shallow ocean, which is a necessary condition for Proudaman resonance, generated the long ocean waves along the west coast of Korea on 2007 March 31 and the ocean waves amplified due to shoaling effect in the coastal area and reflection at the shore.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.6
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• pp.675-688
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• 2007

To characterize organic and elemental carbon (OC and EC), and water-soluble organic carbon (WSOC) contents, daily $PM_{2.5}$ measurements were performed in August 2006 (summer) and Jan $11{\sim}Feb$ 12 2007 (winter) at an urban site of Gwangju. Daily size-segregated aerosol samples were also collected for WSOC analysis. No clear seasonal variations in EC and WSOC concentrations were observed, while seasonal differences in OC concentration, and OC/EC and WSOC/EC ratios were shown. The WSOC/OC ratio showed higher value in summer (0.56) than in winter (0.40), reflecting the greater enhancement of secondary WSOC formation at the site in summer. Secondary WSOC concentrations estimated using EC tracer method were in the range $0.0{\sim}2.1\;{\mu}g/m^3$ (average $0.42\;{\mu}g/m^3$) and $0.0{\sim}1.1\;{\mu}g/m^3\;(0.24\;{\mu}g/m^3)$, respectively, accounting for $0{\sim}51.6%$ (average 16.8%) and $0{\sim}52.5%$ (average 13.1 %) of the measured WSOC concentrations in summer and winter. Sometimes higher WSOC/OC ratio in winter than that in summer could be attributed to two reasons. One is that the stable atmospheric condition often appears in winter, and the prolonged residence time would strengthen atmospheric oxidation of volatile organic compounds. The other is that decrease of ambient temperature in winter would enhance the condensation of volatile secondary WSOC on pre-existing aerosols. In summertime, atmospheric aerosols and WSOC concentrations showed bimodal size distributions, peaking at the size ranges $0.32{\sim}0.56\;{\mu}m$ (condensation mode) and $3.2{\sim}5.6\;{\mu}m$ (coarse mode), respectively. During the wintertime, atmospheric aerosols showed a bimodal character, while WSOC concentrations showed a unimodal pattern. Size distributions of atmospheric aerosols and WSOC with a peak in the size range $0.32{\sim}0.56\;{\mu}m$ were observed for most of the measurement periods. On January 17, however, atmospheric aerosols and WOSC exhibited size distributions with modal peaks in the size range $1.0{\sim}1.8\;{\mu}m$, suggesting that the aerosol particles collected on that day could be expected to be more aged, i.e, longer residence time, than the aerosols at other sampling periods.

• Korean Chemical Engineering Research
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• v.48 no.5
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• pp.556-560
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• 2010

An atmospheric surface modification using plasma treatment method was applied to butadiene rubber to improve its adhesion strength by plate type reactor. In order to investigate the optimum reaction condition of plasma treatment, type of reaction gas(nitrogen, argon, oxygen, air), gas flow rate(30~100 mL/min), treated time(0~30 s) and primer modification method(GMA, 2-HEMA) were examined in a plate type plasma reactor. The results of the surface modification with respect to the treatment procedure was characterized by using SEM and ATR-FTIR. As the gas flow rate and treated time increases the contact angle decreases. The greatest adhesion strength was achieved at optimum condition such as flow rate of 60 mL/min, treated time 5 s and modification primer containing 2-HEMA for air. Due to the atmospheric surface modification using plate plasma method consequently reduced the wettability of butadiene rubber and resulted in the improvement of the adhesion.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.6
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• pp.577-585
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• 2014

A series of experiments using atmospheric-pressure non-thermal plasma coupled with transition metal catalysts were performed to remove ethylene from agricultural storage facilities. The non-thermal plasma was created by dielectric barrier discharge, which was in direct contact with the catalyst pellets. The transition metals such as Ag and $V_2O_5$ were supported on ${\gamma}-Al_2O_3$. The effect of catalyst type, specific input energy (SIE) and oxygen content on the removal of ethylene was examined to understand the behavior of the hybrid plasma-catalytic reactor system. With the other parameters kept constant, the plasma-catalytic activity for the removal of ethylene was in order of $V_2O_5/{\gamma}-Al_2O_3$ > $Ag/{\gamma}-Al_2O_3$ > ${\gamma}-Al_2O_3$ from high to low. Interestingly, the rate of plasma-catalytic ozone generation was in order of $V_2O_5/{\gamma}-Al_2O_3$ > ${\gamma}-Al_2O_3$ > $Ag/{\gamma}-Al_2O_3$, implying that the catalyst activation mechanisms by plasma are different for different catalysts. The results obtained by varying the oxygen content indicated that nitrogen-derived reactive species dominated the removal of ethylene under oxygen-lean condition, while ozone and oxygen atoms were mainly involved in the removal under oxygen-rich condition. When the plasma was coupled with $V_2O_5/{\gamma}-Al_2O_3$, nearly complete removal of ethylene was achieved at oxygen contents higher than 5% by volume (inlet ethylene: 250 ppm; gas flow rate: $1.0Lmin^{-1}$; SIE: ${\sim}355JL^{-1}$).

• Journal of Environmental Health Sciences
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• v.31 no.1
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• pp.15-22
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• 2005

This study was conducted to evaluate air injection mode on stabilization of solid waste in lysimeter. For three lysimeters, one was maintained under anaerobic condition as control, and air was injected into two lysimeters in continuous mode (atmospheric pressure) and intermittent mode (high pressure of 2 bar). Distilled water was sprayed over solid waste in 1.4 l/$m^3$(solid waste)/day, supposing rainfall intensity of 1,200 mm/yr and 30% infiltration. Oxygen in landfill gas was not detected in control lysimeter during operational days. After 30 day-aeration, oxygen concentrations of continuous and intermittent modes were maintained in 14% and 6%, respectively. $COD_{Cr}$ removal efficiencies of continuous and intermittent modes were about 70% and 50%, and BOD5 removal efficiencies were about 80% and 20%, respectively. In view of oxygen supply, and $COD_{Cr}$ and $BOD_5$ removal, continuous air injection mode of atmospheric pressure was more effective than intermittent mode of 2 bar. Settling degree of solid waste in case of two air injection modes was 3 times higher than that of anaerobic condition as control. Considering the above results, it was thought that air injection (especially continuous atmospheric pressure) could improve degradation of solid waste and induce preliminary stabilization in landfill site.

• Journal of Ecology and Environment
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• v.46 no.3
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• pp.161-171
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• 2022

Background: Epilobium hirsutum L. is designated as an endangered plant in South Korea located in Asia, due to the destruction of its habitats through the development of wetlands. Therefore, in this study, in order to find a light condition suitable for the growth and ecophysiological responses of Epilobium hirsutum L., those of this plant under treatment with various light qualities in a smart farm were measured. Results: In order to examine the changes in the physiological and growth responses of Epilobium hirsutum L. according to the light qualities, the treatment with light qualities of the smart farm was carried out using the red light: blue light irradiation time ratios of 1:1, 1:1/2, and 1:1/5 and a red light: blue light: white light irradiation time ratio of 1:1:1. As a result, the ecophysiological responses (difference between leaf temperature and atmospheric temperature, transpiration rate, net photosynthetic rate, intercellular CO₂ partial pressure, photosynthetic quantum efficiency) to light qualities appeared differently according to the treatments with light qualities. The increase in the blue light ratio increased the difference between the leaf temperature and the atmospheric temperature and the photosynthetic quantum efficiency and decreased the transpiration rate and the intercellular CO₂ partial pressure. On the other hand, the white light treatment increased the transpiration rate and intercellular CO₂ partial pressure and decreased the temperature difference between the leaf temperature and the ambient temperature and photosynthetic quantum efficiency. Conclusions: The light condition suitable for the propagation by the stolons, which are the propagules of Epilobium hirsutum L., in the smart farm, is red, blue and white mixed light with high net photosynthetic rates and low difference between leaf temperature and atmospheric temperature.

• Journal of the Korean earth science society
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• v.28 no.3
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• pp.374-387
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• 2007

We examined the characteristics of atmospheric circulation over East Asia to find the causes of the unusual warm winter 2006/2007 in Korea. During that time, the anomalous atmospheric conditions are characterized by the weakening of the Siberian High and the Aleutian Low, the enhancement of low-level south easterlies near Korea, and the weakening of upper-level jet to the south of Japan. These patterns are considerably associated with the atmospheric condition of non-blocking year over the Siberia (60-140E). In addition, both El $Ni\widetilde{n}o$ and Arctic Oscillation (AO) are likely to induce those patterns. Therefore, it is suggested that the anomalous atmospheric states related to non-blocking flow, El $Ni\widetilde{n}o$, and the positive phase of AO are responsible for the warmest winter season in 2006/2007 for the period of 1958/1959-2006/2007.