• Journal of Korean Society for Atmospheric Environment
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• v.14 no.4
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• pp.293-302
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• 1998

This study was performed to investigate the behavior of chlorobenzenes (CIBZS) and chlorophenols (CIPhs) in a thermally treated MSWI fly ash. The experiment was carried out in a fixed bed reactor at the temperature range of 300~$600^{\circ}C$. Reaction time range was between 30 and 120 minutes, and NB and 02 gases were used as carrier gas. The decomposition rate of CIBZS was more affected by reaction time than by the reaction temperature. The decomposition rate of CIPhs was affected by both parameters. Decomposition rate of CIBZS and CIPhs reached 80.4% and 96.6% at $600^{\circ}C$, 120 min, respectively. Considering the effect of O2 content, decomposition rate of CIBZS and CIPhs was the highest at 10% of O2 content. Declorination and decomposition reactions Pere investigated by analyzing homologue distribution. Higher chlorinated CIBZS and CIPhs homologue decreased but lower chlorinated compounds increased with the increase of temperature. Effect of O2 on the homologue distribution of these compounds was not clear in the range of our experiment conditions.

• Asian Journal of Turfgrass Science
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• v.11 no.1
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• pp.33-43
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• 1997

The production and decomposition rate of litters of major forest trees in Korea, such as Quercus acutissima, Quercus mogolica Robinia pseudoacacia Pinus rigida, Pinus thunbergiana, Abies koreana,Phy'llostackys reticulata, were estimated by Olson model. The amount of mineral nutrients in litters and soil were measured, and the relationships among them were studied. The annual litter production was the most in the forest of broadleaved deciduous trees and the least in the forest of monocotyledonous trees. The decomposition rate of broadleaved deciduous litters was higher than that of coniferous litters and lower than that of R. pseudoacacia litters. The time required for the decomposition of half of the accumulated organic matter of R.pseudoacacia litter, Quercus litter, P. rigida litter, Ph. reticulata litter, P. thunbergiana litter and .4.koreana litter in the forest stands were 1.263 years, 2.290~2.365 years, 2.644 years, 4.660 years,4.750 years, 6.699 years respectively. The amounts of N in litters and the amounts of N returned to the soil in the forests of R. pseudoacacia. Quercus, Pinus were proportional to the decay rate of organic matter. Key words: Annual litter production, Decomposition rate.

• Journal of Environmental Health Sciences
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• v.23 no.4
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• pp.127-132
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• 1997

The characteristics of the ozone treatments of phenol were studied in a laboratory scale wastewater treatment system. The ozone treatment of wastewater was carried out in a batch-type reactor. The initial pH of wastewater(7-10), volumetric flow rate(1-2l/min) and ozone concentration(20~30 mg/l) of aerating gas were considereal as experimental variables in the ozone treatment. Phenol was decomposed easily by the ozone in a batch treatment, where the rate determining step was the COD removal that is decomposition of intermediates formed by the ozonation of phenol. Phenol decomposition and COD removal could be expressed by the first order reaction for the phenol concentration and COD, respectively. Rate constants of phenol decomposition and COD removal increased with the initial pH, volumetric flow rate and ozone concentration of aeration gas. Under the present experimental condition, their relationships could be given by for the phenol decomposition $k'=4.46\times 10^{-9}[pH]_o ^{3.94}[O_3]^{1.42}Q_{O3}^{1.57}$ for the COD removal $k=2.46\times 10^{-10}[pH]_o ^{5.19}[O_3]^{1.15}Q_{O3}^{1.19}$

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.6
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• pp.594-600
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• 2023

In this study, a process model and optimization design direction for a hydrogen production plant through ammonia decomposition are presented. If the reactor decomposition rate is designed to approach 100%, the amount of catalyst increases and the devices that make up the entire system also have a large design capacity. However, if the characteristics of the hydrogen regeneration process are reflected in the design of the reactor, it becomes possible to satisfy the total flow rate of fuel gas with the discharged tail gas flow rate. Analyzing the plant process simulation results, it was confirmed that when an appropriate decomposition rate is maintained in the reactor, the phenomenon of excess or shortage of fuel gas disappears. In addition, it became possible to reduce the amount of catalyst required and design the optimized capacity of the relevant processes.

• Korean Journal of Environment and Ecology
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• v.25 no.6
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• pp.887-892
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• 2011

This study was to find out influence of heavy metal concentration in plant on microbial activities during decomposition of Artenmisia princeps var. orientalis and Equisetum arvense collected from an abandoned mine and control site in Cheongyang-gun Chungcheongnam-do. Microbial respiration rate showed the highest value at the time of the first collection, and then tended to decline over time. The highest microbial respiration rate appeared in leaf litters with low heavy metal contents, and A. princeps var. orientalis and E. arvense collected and decomposed at the control site showed the fastest decomposition rate. For both A. princeps var. orientalis and E. arvense, litters with low heavy metal content appeared to have higher microbial biomass. There was apparent quantitative correlation between decomposition rate and cumulative respiration rate of leaf litters, and between decomposition rate and microbial biomass of leaf litters. Thus, the study result showed that leaf litter with higher heavy metal content had a negative impacts on the growth and activity of microbial decomposer during decomposition processes.

• Journal of Environmental Science International
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• v.10 no.5
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• pp.315-321
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• 2001

This study was conducted to estimate the decomposition capacity for organic matter by microbe of tidal flat sediments (Hajae, Dongjin and Mankyung). The decomposition rate constants (K') have been determined by Thomas slope method and compared with the values of each tidal flats. The decomposition rates of organic matter by microbe were initially very slow, but at the end of 12 hours, very sharply increased. The values of decomposition rate constant for Dongjin, Mankyung and Hajae tidal flat sediment were 1.364$day^{-1}$/, 1.080d$day^{-1}$ and 0.735$day^{-1}$, respectively. The decomposition rate constant of Dongjin tidal flat sediment which affected by livestock wastewater was higher than others. The decomposition quantity (mg/g/day) of organic matter by microbe of tidal flat sediments was 0.4mg/g/day for Dongjin, 0.36mg/g/day for Mankyung and 0.36mg/g/day for Hajae. The average of decomposition quantity was 0.37mg/g/day. To calculate purification capacity (kg/ha) of organic matter by microbe, we applied to two assumption ; 1) biological action by microbe is occur within 0.1cm under surface 2) specific gravity of sediment are 2.5g/$\textrm{cm}^2$. The purification capacity of organic matter by microbe of tidal flat sediment was calculated to 9.25kg/ha. The relationships between decomposition rate constant (K') and ignition loss (I. L), chemical oxygen demand by sediment (CO $D_{sed}$), total carbon(TC), silt and clay as index of organic matter were a high positive($R^2$=0.97~1.00).

• The Korean Journal of Ecology
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• v.26 no.4
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• pp.203-208
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• 2003

Losses in the dry weight of leaf litter from six tree species were studied during 16 months on the forest floor in temperate deciduous forest of Mt. Cheonma in the vicinity of Seoul in Korea by using litter bag method. The decomposition rate of each leaf litter varies with each species. After 16 months elapsed, the leaf litter of Acer pseudo-sieboidianum showed the highest decomposition constant (0.82) as Olson´s decomposition constant, while that of Pinus densiflora showed the lowest decomposition constant (0.33). The decomposition constant of Quercus mongolica, Q. serrata, Betula ermani and Carpinus laxiflora showed 0.43, 0.37, 0.66 and 0.75, respectively. The decomposition constant of leaf litter was considered with temperature and precipitation which accumulated daily during each term of litter bag collection. The decomposition constant of leaf litter showed closely positive correlation with daily accumulative temperature and precipitation. The relationships between decomposition constant and the daily accumulative temperature and precipitation at each period of litter bag collection were analyzed through multi-regression analysis. The correlation coefficients as a result of multi-regression analysis in Q. mongolica, Q. serrata, P densiflora, B. ermani, C. laxiflorais and A. pseudo-sieboldianum were 0.83, 0.81, 0.69, 0.77, 0.77 and 0.62, respectively. The precipitation showed higher effect, about 10 times, on the leaf litter decomposition than the daily accumulative temperature.

• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4441-4448
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• 2022

The electrochemical oxidation process has been widely studied in the field of wastewater treatment for the decomposition of organic materials through oxidation using ·OH generated on the anode. Pt anode electrodes with high durability and long-term operability have a low oxygen evolution potential, making them unsuitable for electrochemical oxidation processes. Therefore, to apply Pt electrodes that are suitable for long-term operation and large-scale processes, it is necessary to develop a new method for improving the decomposition rate of organic materials. This study introduces a method to improve the decomposition rate of organic materials when using a Pt anode electrode in the electrochemical oxidation process for the treatment of organic decontamination liquid waste. Electrochemical decomposition tests were performed using sodium dodecylbenzenesulfonate (SDBS) as a representative organic material and a Pt mesh as the anode electrode. Y₂O₃ particles were introduced into the electrolytic cell to improve the decomposition rate. The decomposition rate significantly improved from 21% to 99%, and the current efficiency also improved. These results can be applied to the electrochemical oxidation process without additional system modification to enhance the decomposition rate and current efficiency.

• Journal of Pharmaceutical Investigation
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• v.11 no.3
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• pp.21-26
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• 1981

The rate of decomposition of calcium thioglycollate in aqueous solution was shown to increase with increasing temperature and with diluting concentration of calcium thioglycollate. The effect of additive on oxidation rate of calcium thioglycollate was studied to prepare the more stable depilatory formula using additives, such as thiourea, mannitol, sodium thiocyanide, nicotinamide, triethanolamine and ethylenediamine. In all cases, the rate of oxidation was reduced when the additive was present in the solution, among them triethanolamine and ethylenediamine inhibited the decomposition rate remarkably. It is assumed that the decomposition reaction in aqueous solution is pseudo-first order reaction.

• Journal of Korean Society on Water Environment
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• v.24 no.2
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• pp.174-179
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• 2008

The distribution of organic carbon and its decomposition rate were studied in the middle and down stream reaches of the Kum River system, Korea. Water samples were collected from May to June in 2006 at seven mainstream sites and three tributary sites from the river mouth to the Daechung Reservoir outlet. The change of DOC and POC were measured during incubation for the determination of decomposition rate. The reduction of organic carbon during 20 days' incubation was regarded as labile or biodegradable organic carbon (LDOC, LPOC), and the remaining organic carbon was regarded as recalcitrant organic carbon. The mean TOC was $5.17({\pm}1.49)mgC{\cdot}L^{-1}$ in the mainstream sites and $7.09({\pm}1.48)mgC{\cdot}L^{-1}$ in tributary sites, respectively. TOC comprised of 62% DOC and 38% POC. LPOC was approximately 68% of POC, while LDOC was only 24% of DOC. Mean decomposition rate of TOC was about $0.03day^{-1}$. Mean decomposition rates of LPOC ranged from $0.10day^{-1}$, and that of LDOC was approximately $0.08day^{-1}$. The decomposition rate of both LPOC and LDOC did not show significant difference between mainstream and tributary sites. The result of this study can give a guide to the selection of parameters in the calibration processes of water quality models.