• Journal of the Korean Applied Science and Technology
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• v.39 no.2
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• pp.368-376
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• 2022

Spontaneous ignition occurs in industrial sites or anywhere in our lives, and is a phenomenon in which a substance ignites itself without an ignition source in the atmosphere. As the rate of chemical reaction increases, the heat generated increases, and the risk of spontaneous ignition increases. In this study, safe raw materials used for food and cosmetics were mixed to prepare coal spontaneous ignition prevention agents specifically among various spontaneous ignition phenomena. The effect of suppressing spontaneous combustion of coal was confirmed through lab and field tests with low-calorie, low-grade coal from Indonesia. As a result of the outdoor field test, the ignition prevention agent manufactured in this study compared with the control group(Fire after 90 days) showed excellent ignition inhibitors for more than 120 days. In addition, CO concentration control was confirmed by comparing the concentration of carbon monoxide for 50 days at the indoor coal yard. It was confirmed that the results were better than the comparative group coal and the existing anti-firing method. In addition, the possibility of coal fire prevention agents for indoor coal farms will be applied from 2024 was confirmed by studying the environment and safety of workers' working environments through official test such as soil and water quality test, MSDS of coal fire prevention agents in consideration of working workers, water quality, and eye irritation tests.

• Clean Technology
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• v.27 no.2
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• pp.152-159
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• 2021

Volatile organic compounds (VOCs) occur in indoor and outdoor industrial and urban areas and cause environmental problems. Malodorous VOCs, along with aesthetic discomfort, can have a serious effect on the human body. Compared with the existing method of reducing malodorous VOCs, a wet scrubbing method using an electrolytic oxidant has the advantage of reducing pollutants and regenerating oxidants. This study investigated the optimal conditions for producing OCl^-, a chlorine-oxidant. Experiments were conducted by changing the type of anode and cathode electrode, the type of electrolyte, the concentration of electrolytes, and the current density. With Ti/IrO₂ as the anode electrode and Ti as the cathode electrode, OClproduction was highest and most stable. Although OCl^- production was similar with the use of KCl or NaCl, NaCl is preferable because it is cheap and easy to obtain. The effect of NaCl concentration and current density was examined, and the OCl^- production rate and concentration were highest at 0.75 M NaCl and 0.03 A cm^-2. However, considering the cost of electric power, OCl^- production under the conditions of 1.00 M NaCl and 0.01 A cm^-2 was most effective among the conditions examined. It is desirable to produce OCl^- by adjusting the current density in accordance with the concentration and characteristics of pollutants.

• Journal of Environmental Science International
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• v.14 no.2
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• pp.231-240
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• 2005

The number of cases exceeding environmental standards of atmospheric ozone in the major cities in Korea has steadily increased during the past decades. In order to understand and analyze the atmospheric reactions in the atmosphere, especially the secondary photochemical reactions, smog chambers studies have been performed very actively by many research groups worldwide. However, these studies have focused on the mechanism of photochemical reactions in high concentration conditions, not at the ambient levels. Therefore, in-depth studies in these conditions are essentially needed to realize exact mechanism in the atmosphere near the earth surface, especially at Korean atmospheric conditions. In this experiment, the mechanism of photochemical smog was examined through a comparative experiment of smog chambers under sun light and black light conditions. The results of our study indicated that concentrations of ozone, aldehyde, and PAN increased as the radiation of light source increases. Photochemical reaction patterns can be considered quite similar for both black light and sun light experiments. Based on our experiments using toluene as a reactant which is present at significant high levels in ambient air relative to other VOCs, it was found that toluene could contribute notably to oxidize NO to $NO_2$, this reaction can eventually generate some other photochemical oxidants such as ozone, aldehyde, and PAN. The results of simulation and experiments generally showed a good agreement quite well except for the case of $O_3$. The restriction of oxidization of NO to $NO_2$ seems to cause this difference, which is mainly from the reaction of peroxy radical itself and other reactants in the real gas.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.22 no.4
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• pp.265-275
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• 2012

Objectives: The aim of this study was to investigate the distribution patterns and exposure concentrations of biological hazards in waste handling industries. Methods: We selected 3 recyclable waste sorting plants(RWS), 2 food recycling plants(FR), 1 landfill area(LA) and 1 waste incineration plant(WI). Total airborne bacteria and fungi were measured with single stage impactor and gelatin filters. Endotoxin and glucan were measured with polycarbonate filters in total and respirable dust. Results: The geometric mean of airborne bacterial concentration was the highest in FR($3,273CFU/m^3$), followed by LA, RWS, and WI as 1,334, 934, and $860CFU/m^3$. The fungal concentrations were 6,031, 5,052, 3,307, and $713CFU/m^3$ in RWS, WI, FR, and LA, respectively. By process, WI pit showed the highest concentrations of bacteria, fungi, and endotoxin, followed by inside of bulldozer in LA. The indoor to outdoor ratios of bacteria, fungi, endotoxin and glucan were 2.3, 4.0, 2.3, and 5.0 in RWS, 29.5, 4.9, 7.6, and 5.0 in FR, 5.3, 8.7, 26.8, and 9.5 in WI, respectively. Conclusions: We found that biological hazards, specifically bacteria in FR, fungi in RWS and endotoxin in WI pit and bulldozer at LA, should be controlled to prevent worker's respiratory diseases.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.2
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• pp.80-83
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• 2002

The effect of chloride content on the corrosion of reinforced bar in concrete was studied. The mixing ratio of the concrete was 1 : 1.78 : 5.35 : 4.73 (water : content : ballast : sand). The studied chloride content was in the range of 0∼3.5 wt%. The corrosion potentials were measured in every week for two years. The copper-copper sulfate electrode (CSE) was employed as a reference electrode. After two years, the corroded structure was examined and compared to measured corrosion potential. Any visible difference was founded in the specimen located indoor and outdoor. The chloride concentration enhanced rusting and reinforced bar, shifting the potential to active range. The results showed good argument with Van daveer criteria. In 3.5 wt% chloride, the potential shifted belong -350 mV after 58week. Specimen in 1.75 wt% chloride, showed the potential between -200 mV∼-350 mV. However those in free chloride solution maintained above -200 mV for the studied period. It can the concluded that the chloride enhanced corrosion of rebar in concrete and the electrochemical potential can be a promising corrosion monitoring technique.

• Korean Journal of Environmental Biology
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• v.25 no.3
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• pp.191-196
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• 2007

Indoor air differs from outdoor atmosphere since it contains chemical and physical contaminants from building materials. This study deals with the biological effects of volatile organic compounds (VOCs) released from synthetic fiber carpet materials. One group of Tradescantia inflorescence was exposed to VOCs from the carpet sample in the environmental test chamber, while the other inflorescence group was exposed to a TO-14 standard gas mixture (1 ppm) for comparison. After the exposure, VOCs from the carpet were analysed by the desorber/GC/MS method, and micronuclei in the pollen mother cells of Tradescantia were scored under a microscope $({\times}400)$ to evaluate the genotocixicity induced by the exposure to VOCs. The chemical analysis confirmed that a total of 12 VOCs were released from the carpet materials, among which stylene $(71.9{\mu}g\;m^{-3})$ and toluene $(49.6{\mu}g\;m^{-3})$ were in the highest concentration. Twenty four hours of exposure to VOCs from the carpet in the environmental test chamber resulted in a micronucleus frequency as high as $7.73{\pm}0.75MCN$ per 100 tetrads, which was similar to that induced after exposure to the TO-14 standard gas mixture (1 ppm) for 4 hours. Meanwhile, two hours of exposure to the standard gas mixture did not cause a significant increase in the genotoxicity compared to the spontaneous micronucleus frequency. This result indicates that exposure for a long time to the air contaminated with VOCs from the carpet materials causes a genotoxic effect. The biological-chemical combination analyses in the study proved to be an effective tool for monitoring the indoor air contaminants.

• Journal of Environmental Impact Assessment
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• v.27 no.4
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• pp.378-393
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• 2018

As atmospheric fine dust problems in Korea become more serious, there are growing needs to find the concentration of fine particles in indoor and outdoor areas and there are increasing demands for sensor-based portable monitoring devices capable of measuring fine dust concentrations instantly. The low-cost portable monitoring devices have been widely manufactured and used without the prescribed certification standards which would cause unnecessary confusion to the concerned public. To evaluate the reliability those devices and to improve their usability, following studies were conducted in this work; 1) The comparisons between sensor-based devices and comparison with more accurate devices were performed. 2) Several experiments were conducted to understand usefulness of the portable monitoring devices. As results, the absolute concentration levels need to be adjusted due to insensitivity of the tiny light scattering sensors in the portable devices, but their linearity and reproducibility seem to be acceptable. By using those monitoring devices, users are expected to have benefits of recognizing the changes of concentration more quickly and could help preventing themselves from the adverse health impacts.

• Particle and aerosol research
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• v.18 no.3
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• pp.51-59
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• 2022

In this work, virion concentration and its dose changes by HVAC and air cleaners were estimated in a subway station platform to control airborne infection of SARS-CoV-2. Collection efficiencies with particle size were measured for the air filter equipped in a HVAC in one subway station in Daejeon. Indoor PM_2.5 changes according to outdoor PM_2.5 with time were also measured to estimate air infiltration rate in the subway station platform. When infected persons generate virions by 10⁴, 10⁵, 10⁶, 3 × 10⁶ and 5 × 10⁶ h^-1 in a 2,400 m³ volume platform, the concentration and dose were estimated as 9, 92, 275 and 458 virions/m³ and 4, 43, 130 and 217 virions after 1 hour exposure, respectively. The concentration and dose were reduced by 70%, and 64%, respectively by operations of both HVAC (with a flow rate of 16,000 m³/h, MERV 11) and ten air cleaners(with total CADR 10,740 m³/h) compared to those without operation of both HVAC and air cleaners. However, virion dose in the platform was estimated to be too low at the general conditions due to a large space, a high air infiltration (3 h^-1) and a short residence time (usually < 10 mins) in the platform irrespective of the operations of HVAC or air cleaners. HVAC with filters and air cleaners would be more necessary in the concourse or shopping areas in the subway stations to reduce the infection dose from a few hundred to several tens virions in a hour.

• Journal of the Korean Institute of Landscape Architecture
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• v.45 no.4
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• pp.1-10
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• 2017

This study investigated indoor temperature and humidity control and PM1 and PM10 mitigation effects of a single green wall (Case 1), two green walls (Case 2), and two green walls plus a waterfall (Case 3) in comparison with a control without either a green wall or waterfall. Experiments were conducted in the office of Chungbuk National University from August to September, 2015. Experiments were carried out sequentially in the order of control, Case 1, Case 2, and Case 3. Data collected from August 17 to August 20, 2015 (Experiment 1), and from August 31 to September 3, 2015 (Experiment 2), when outdoor temperature was relatively constant, were analyzed. Plant volume ratios by indoor landscaping of the control, Case 1, Case 2 and Case 3 were 0.0, 0.6, 1.2, and 1.4%, respectively. Compared to the control, average temperatures of Case 1, Case 2 and Case 3 were decreased by 0.3~0.7, 0.7~0.9 and $1.0^{\circ}C$, respectively, and relative humidity was increased by 1.8~8.7, 9.2~14.6 and 14.8~21.9%, respectively. Three hundred minutes after exposure to mosquito repellent incense particles, the ratio of the remaining PM1 of the control, Case 1, Case 2 and Case 3 were 25.0, 22.0%, 21.2%, 17.3%, respectively, in Experiment 1 and 42.3, 28.9, 23.1, and 30.9%, respectively, in Experiment 2. As indoor greening increased the effect of indoor temperature, PM1 and PM10 mitigation were greater, and temperature and humidity were lower. The greater the relative humidity was, the faster PM1 and PM10 mitigation tended to be.

• Journal of Environmental Health Sciences
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• v.48 no.2
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• pp.59-65
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• 2022

Background: Since people move through microenvironments rather than staying in one place, they may be exposed to both indoor and outdoor PM_2.5 concentrations. Objectives: The aim of this study was to assess the exposure level of each sub-population group and evaluate the contribution rate of the major microenvironments. Methods: Exposure scenarios for sub-population groups were constructed on the basis of a 2019 Time-Use survey and the previous literature. A total of five population groups were classified and researchers wearing MicroPEM simulated monitoring PM_2.5 exposure concentrations in real-time over three days. The exposure contribution for each microenvironment were evaluated by multiplying the inhalation rate and the PM_2.5 exposure concentration levels. Results: Mean PM_2.5 concentrations were 33.0 ㎍/m³ and 22.5 ㎍/m³ in Guro-gu and Wonju, respectively. When the exposure was calculated considering each inhalation rate and concentration, the home showed the highest exposure contribution rate for PM_2.5. As for preschool children, it was 90.8% in Guro-gu, 94.1% in Wonju. For students it was 65.3% and 67.3%. For housewives it was 98.2% and 95.8%, and 59.5% and 91.7% for office workers. Both regions had higher exposure to PM_2.5 among the elderly compared to other populations, and their PM_2.5 exposure contribution rates were 98.3% and 94.1% at home for Guro-gu and Wonju, respectively. Conclusions: The exposure contribution rate could be dependent on time spent in microenvironments. Notably, the contribution rate of exposure to PM_2.5 at home was the highest because most people spend the longest time at home. Therefore, microenvironments such as home with a higher contribution rate of exposure to PM_2.5 could be managed to upgrade public health.