• Journal of Environmental Health Sciences
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• v.44 no.1
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• pp.24-30
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• 2018

Objectives: Based on the amount of amalgam, the duration of exposure, and the water pH, this study aims to investigate the change patterns in the mercury concentrations in water after amalgams have been introduced into sewage water. It is expected that the study results will be useful in improving the system for regulating the amount of mercury that is introduced into the environment. Methods: During the study, a glass test-tube with a cap was washed and disinfected using the glass laboratory device washing method. Then, 1, 2, 3, and 4 tabs were placed into a 10 mL pH 4 solution and 10 mL pH 7 distilled water. Each specimen was prepared in duplicate. The mean of the two mercury concentrations was used as the representative value, and the mercury concentration was measured using a mercury measurement device (DMA-80, Milestone, Italy) a total of eight times at one-week intervals. Results: The results show that the lower was the pH, the higher was the amount of amalgam. Also the longer was the duration, the more significant was the increase of mercury concentration in the water. Conclusions: Dental clinics are collected separately from dental clinics that used them. Given this, dental clinics in Korea must have the necessary facilities to separately collect mercury at their level. In addition, proper disposal systems and social attention to the proper management of dental wastes are required to prevent environmental pollution from mercury.

• Journal of the Korean Institute of Landscape Architecture
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• v.23 no.1
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• pp.51-65
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• 1995

Conservation of the natural environiment In chosun-Dynasty, Korea, is analysed on the basis of the of official records of the king's offices(Chosun-wangjo-sillok). In the popular ideologies of the dynasty, Seongleehak(philosophy of humanity arid natural laws) and Pungsu (geomancy) , the naturnal enviroment is defined as an entity con-sisting of Cheon (heaven) , San(mnountains) , Su (water), Geumsu (animals)and Chomok (plants) .the notion of Tacksi-Tackmul(being careful to take natural resources at the right time) was one of the Cheonmyung (eavenly decrees) . It was believed that violation of this principle resulted in natural disasters. Sasan(four mountains surrounding Hansungbu-, the capital city, now Seoul) , were strictly preserved according to geomancy practices. In areas other than the capital city, Sanlimcheontack (mountains, forests, rivers and ponds) were con-served for sustained production of building materials especially pinetrees for ship building, foods, firewoods, horses, and orter useful natural resources. Various conservation policy insturuments were adopted. Prunning trees was permitted only in October. Capturing fishes was allowed only after the spawning period. Protection areas were designated in Sasan, Seongjoesiplee (surroundings of the capital city) , Geumsan(protected mountains), Kangmujang(hunting and army training grounds), Sijang(firewood areas), Mokmajang(horse ranches) and Neungyuk(royal tombs) . Activities prohibited for conservation purposes included cutting timbers, burning, building houses or tombs, dumping wastes, farming and breaking up fresh land, grazing, hunting and trespassing. Positive actions for conservation were rituals to Heaven ennoblement of natural elements such as mountians or rivers, planting trees, Boto (supplementing soil on low ridges) , Josan (mounding) and making ponds. Boto, Josan and making ponds were to make ideal terrains for geomancy. Many government bodies and civil servants were engaged in the conservation activities. For example, Sanjik(forest keeper) was a special position with responsibility for forest management.

• The Journal of Engineering Geology
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• v.16 no.4 s.50
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• pp.351-357
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• 2006

Recently there is increasing the flow of hazardous chemical substances caused by industrial waste waters into a main river. It is needed to make the high treatment in drinking water treatment plants for reducing a health risk. Therefore, the monitoring of trace hazardous chemical substances by the industrial waste water inflow is available increasing economical efficiency of river management as well as reduction of risk. In this study, the most important substance among numerical and quantitative trace hazardous chemicals is Hexachlorobutadiene in an effluent of industrial wastes. However all items of GroupII which was included with semiconductor, electricity/electron and metal assemble was not detected. It means that we must consider the characteristics and behavior of load pollutants to water resources to select monitoring items. That was called 'preparatory monitoring'. We can reduce an economical consumption as well as risks from these pollutants using the preparatory monitoring.

• Korean Journal of Community Nutrition
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• v.24 no.5
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• pp.422-432
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• 2019

Objectives: The purposes of the study were to assess wastes generated in school foodservice and to identify factors influencing the generation of plate waste. Methods: A survey was administered from November 18-30 in 2015 to dietitians and nutrition teachers that were employed in schools located in Gyeonggi province. A questionnaire file and on-line survey site link were sent to the dietitians and nutrition teachers by e-mail. A total of 622 dietitians and nutrition teachers responded and 594 responses were used for data analysis after excluding 28 responses with significant missing data. Results: Plate waste was the major part of food waste generated in school foodservice. Vegetable menus and soup/stews were discarded the most as plate waste. The dietitians and nutrition teachers perceived students' unbalanced diet and lack of appreciation of food as causes of the plate waste. Regarding waste management, they were concerned about environmental contamination by food waste and felt uncomfortable about discarding food. No plate waste day was the most frequently used plate waste reduction activity, followed by newsletters on plate waste reduction. Difficulty in getting teachers' support for dietary education during meal time was rated the greatest barrier to implementing the activities. To reduce plate waste, they perceived that students should understand the importance of environment conservation, teachers should supervise students' eating during meal time, students should be educated about proper portion, and foodservice staff should improve food quality. Conclusions: To improve students' intake and reduce plate waste in school foodservice, foodservice staff need to involve students in school foodservice and improve the palatability of meals, especially vegetable dishes. School nutrition teachers and dietitians should educate students about healthy eating and environment conservation and the school community needs to understand and support plate waste reduction and healthy eating in schools.

• The KIPS Transactions:PartC
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• v.9C no.5
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• pp.783-788
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• 2002

Adaptive Cyclic Packet Dropping algorithm (ACPD), and Non-adaptive Cyclic Packet Dropping algorithm (NCPD) are applying stricter drop precedence than that of RIO algorithm. Especially, the ACPD algorithm drops adaptively packets for the congestion control, as predicting traffic pattern between each cycle. Therefore the ACPD algorithm makes up for the drawback of RIO algorithm and minimizes the wastes of the bandwidth being capable of predicting in the NCPD algorithm. And we executed a simulation and analyzed the throughput and packet drop rate based on Sending Priority changing dynamically depending on network traffic. In this algorithm, applying strict drop precedence policy, we get better performance on priority levels. The results show that the proposed algorithms may provide more efficient and stricter drop precedence policy as compared to RIO independent of traffic load. The ACPD algorithm can provide better performance on priority levels and keep stricter drop policy than RIO and the NCPD algorithm.

• Resources Recycling
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• v.26 no.5
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• pp.29-38
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• 2017

This study suggests optimal policy options for collection of used diapers through benchmarking of foreign countries and perception surveys. By conducting a survey, this study can identify the actual problems involved in the collection process and enhance the social acceptance toward diaper recycling policies. As a perception survey result, the economic burden of emission bags and sanitary issues were most important for the collection pilot test. Respondents thought that twice-a-week collection frequency was appropriate and that free emission bags might be preferable to participants. Currently municipal wastes are subject to waste management laws, which are applied by local governments. Diaper waste is categorized with municipal waste, so it seems to be treated by municipal waste systems. In terms of connection with government, possible alternatives were suggested to identify the relevant local government. Useful data could be obtained, to determine the economical viability of any future diaper recycling system implementation in the entire Seoul metropolis and adjacent areas of dense population.

• Applied Chemistry for Engineering
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• v.32 no.2
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• pp.205-213
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• 2021

The present study aimed to determine the effect of co-pyrolysis of sawdust biomass and scrap tyre waste employing different blending ratios of sawdust to waste tyre such as 100:0, 75:25, 50:50, 25:75, and 0:100. The thermochemical characterization of feedstocks was carried out by employing the proximate, ultimate analysis, and thermogravimetric (TGA) analyses, calorific values, and scanning electron microscope coupled with energy dispersive x-ray analysis (SEM-EDX) to select the blending ratio having better bioenergy potential amongst the studied ratios. The blending ratio of 25:75 (sawdust to waste tyre) was selected for the co-pyrolysis study in a fixed-bed pyrolysis reactor system based on its solid biofuels properties such as heating value (30.18 MJ/kg), and carbon (71.81 wt%) and volatile matter (63.82 wt%) contents. The pyrolysis temperatures were varied as 500, 600 and 700 ℃ while the other parameters such as heating rate and nitrogen flowrate were maintained at 30 ℃/min and 0.5 L/min respectively. The bio-oil yields as 31.9, 47.1 and 61.2 wt%, bio-char yields as 34.5, 34.2 and 31.4 wt% and gaseous product yields as 33.6, 18.60 and 7.3 wt% at the pyrolysis temperatures of 500, 600 and 700 ℃ respectively were obtained. The blends of sawdust and waste tyres showed the improved energy characteristics which could provide the solution for the beneficial management of sawdust and scrape tyre wastes via co-pyrolysis processing.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1206-1212
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• 2022

Cold-crucible induction melting (CCIM) technology has been intensively studied as an advanced vitrification process for the immobilization of highly radioactive waste. This technology uses high-frequency induction to melt a glass matrix and waste, while the outer surface of the crucible is water-cooled, resulting in the formation of a frozen glass layer (skull). In this study, for the fabrication of borosilicate glass waste form, CCIM operation test with 60 kg of glass per batch was conducted using surrogate wastes composed of Cs, Sr, and Nd as a representative of highly radioactive nuclides generated during spent nuclear fuel management. A 60 kg-scale glass waste form was successfully fabricated through melting and draining processes using a CCIM system, and its physicochemical properties were analyzed. In particular, to enhance the controllability and reliability of the draining process, an air-cooling drain control method that can control draining through air-cooling near drain holes was developed, and its validity for draining control was verified. The method can offer controllability on various draining processes, such as molten salt or molten metal draining processes, and can be applied to a process requiring high throughput draining.

• Korean Journal of Environmental Agriculture
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• v.42 no.3
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• pp.184-192
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• 2023

Microplastics are generated by the breakdown of plastic wastes in agricultural soil and residual pesticides in agricultural soil can adsorb on microplastics. In this study, the sorption characteristics of procymidone (PCM) and one of its metabolites, 3,5-dichloroaniline (DCA), on low-density polyethylene (LDPE) and polyvinyl chloride (PVC) microplastics were investigated. The sorption and desorption tests were carried out for 72 h using LDPE or PVC microplastic films to study the sorption isotherms of PCM and DCA and kinetics for sorption and desorption of PCM. The results show that the sorption data of PCM and DCA were better described by the Freundlich isotherm model (R²=0.7568-0.9915) than the Langmuir isotherm model (R²=0.0545-0.5889). The sorption potential of PVC for both PCM and DCA was greater than that of LDPE. The sorption data of PCM on PVC and LDPE were fitted better to the pseudo-second-order kinetic model than the pseudo-first-order kinetic model. The PCM sorption on LDPE was about three times faster than that on PVC. Both microplastic films released the sorbed PCM back to water, and more PCM was released from PVC than LDPE, but the desorption rate was faster with LDPE than PVC. Overall, the results show that different microplastics have different sorption characteristics for different chemicals. Also, the sorbed chemicals can be released back to environment suggesting the potential of contaminant spread by microplastics. Thus, the management practices of microplastics in agricultural soil need to consider their interaction with the chemical contaminants in soil.

• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.412-418
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• 2023

The surge in the oil prices, increasing global population, climate change, and waste management problems are the major issues which have led to the development of biofuels from lignocellulosic wastes. Cellulosic or second generation (2G) bioethanol is produced from lignocellulosic biomass via pretreatment, hydrolysis, and fermentation. Pretreatment of lignocellulose is of considerable interest due to its influence on the technical, economic and environmental sustainability of cellulosic ethanol production. In this study, furniture waste sawdust was subjected to alkaline peroxide (H₂O₂) for the production of reducing sugars. Sawdust was pretreated at different concentrations from 1-3% H₂O₂ (v/v) loadings at a pH of 11.5 for a residence time of 15-240 min at 50, 75 and 90 ℃. Optimum pretreatment conditions, such as time of reaction, operating temperature, and concentration of H₂O₂, were varied and evaluated on the basis of the amount of total reducing sugars produced. It was found that the changes in the amount of lignin directly affected the yield of reducing sugars. A maximum of 50% reduction in the lignin composition was obtained, which yielded a maximum of 75.3% total reducing sugars yield and 3.76 g/L of glucose. At optimum pretreatment conditions of 2% H₂O₂ loading at 75 ℃ for 150 min, 3.46 g/L glucose concentration with a 69.26% total reducing sugars yield was obtained after 48 hr. of the hydrolysis process. Pretreatment resulted in lowering of crystallinity and distortion of the sawdust after the pretreatment, which was further confirmed by XRD and SEM results.