• Journal of Soil and Groundwater Environment
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• v.12 no.5
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• pp.115-123
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• 2007

Immobilization of contaminants in subsurface environment is one of the major processes that determine their fate. Especially, immobilization by oxidative-coupling reactions, which is irreversible in the bio-chemical reactions and results in a significant reduction of toxicity, can be successfully applied for the remediation of contaminated soil and groundwater more effectively than conventional degradation. As a catalyst of this oxidative-coupling reaction, manganese oxide has many advantages in practical aspects as compared to microorganisms or oxidoreductive enzymes extracted from microorganisms, fungi, or plants. This paper is to present recent research achievements on the treatment mechanisms of various organic contaminants by manganese oxide. Especially, treatment methods of non-reactive organic compounds to Mn oxide are the main focus; i.e., application of reaction mediator, PAHs treatment method, combination with an appropriate pretreatment such as reduction using $Fe^0$, which suggests the potential of a wide range of engineering application. Concerning the natural carbon cycle processes, immobilization and stabilization by oxidative coupling reaction can be effectively applied as a environmentally-friend remediation method especially for aromatic contaminants which possess a high resistance to degradation.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.4
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• pp.25-33
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• 2019

Operating characteristics of a 30 L microbial electrolysis cell (MEC) for producing biogas from sewage sludge was studied. During the 32-day inoculation period, carbon dioxide concentration decreased and methane concentration increased with operating time, and the overall methane content of biogas was 69.1% with a production rate of 171.6 mL CH₄/L·d. In fed-batch experiments for 6 operating cycles, CH₄ concentration of 66.5~77.2% was obtained at a production rate of 184.9~372.9 mL CH₄/L·d, COD, TS and VS removal efficiency ranged from 28.2 to 42.1%, 20.7 to 37.5% and 18.5 to 36.9%, respectively. The MEC system was observed to be stabilized as operating cycles were repeated after inoculation. In the last operating cycle, 5221 mL/L of methane was produced with CH₄ yield of 316.7 L CH₄/kg COD_rem, and the energy recovery was 73%.

• Korean Journal of Microbiology
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• v.50 no.3
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• pp.191-200
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• 2014

Gas hydrates play a significant role in the global carbon cycle and climate change because methane, a greenhouse gas, can be released from the dissociation of gas hydrate. Anaerobic oxidation of methane (AOM) is an important process that consumes more than 90% of the methane released into the hydrosphere and atmosphere. In this study, the microbial community associated with the methane gas hydrate sediment in the Ulleung basin, East Sea of Korea (UBGH) was analyzed by phylogenetic analysis of the mcrA and 16S rRNA gene libraries. A vertical stratification of the dominating anaerobic methane oxidizer (ANME)-1 group was observed at the surface and the sulfate methane transition zone (SMTZ). The ANME-2c group was found to be dominant in the high methane layer. The archaea of marine benthic group B, which is commonly observed in the AOM region, accounted for more than 50% of the identifications in all sediments. Nitrate reducing bacteria were predominant at SMTZ (Halomonas: 56.5%) and high methane layer (Achromobacter: 52.6%), while sulfate reducing bacteria were not found in UBGH sediments. These results suggest that the AOM process may be carried out by a syntrophic consortium of ANME and nitrate reducing bacteria in the gas hydrates of the Ulleung Basin of the East Sea.

• 한국생물공학회:학술대회논문집
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• 2002.04a
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• pp.461-464
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• 2002

A Chemoautotroph identified as an Aeromonas sp. strain JS-1 was isolated from fresh water. Aeromonas sp. strain JS-1 used the $H_2$ and $CO_2$ as energy and carbon sources, respectively. Growth characteristics for improving the $CO_2$ fixation rate were examined in batch cultivation. Its results shown that the optimal growth appeared at culture conditions of $35^{\circ}C$, pH 7 and NaCl 0.1%(w/v). Some hydrogen-oxidizing bacteria were reported that the enzyme activity of ribulose 1,5-bisphosphate carboxylase- oxygenase (RubisCO-EC 4.1.1.39), in the key enzyme of the Calvin-Benson cycle. A RubisCO was purified from a chemoautotrophic bacterium, Aeromonas sp. strain JS-1. the enzyme was purified by ammonium sulfate precipitation, DEAE-sepharose CL-6B and gel filtration chromatography. The RubisCO showed that molecular mass was about 560KDa from gel filtration chromatography and nondenaturing PAGE, and the RubisCO was confirmed to consist of $L_8S_8$ enzyme structure by sodium dodecyl sulfate polyacrylamide gel electrophoresis. A large subunit was about 56KDa and small one was about 15kDa. The Km values of the enzyme for ribulose 1,5-bisphosphate(RUBP), $NaH^{14}CO_3$, and $Mg^{++}$ were estimated to be 0.25mM, 5.2mM, and 0.91mM, respectively. The optimum temperature for RubisCO enzymatic activity were $50^{\circ}C$, and the enzymatic activity was stable up to $45^{\circ}C$.

• Applied Biological Chemistry
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• v.40 no.2
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• pp.134-138
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• 1997

The objective of this study was to examine the effect of phosphorus deficiency on nitrogen fixation and photosynthesis of nitrogen fixing soybean plant under $CO_2$ enrichment condition. The soybean plants(Glycine max [L.] Merr.) inoculated with Bradyrhizobium japonicum MN 110 were grown with P-stressed(0.05 mM-P) and control(1 mM-P) treatment under control$(400\;{\mu}l/L\;CO_2)$ and enrichment$(800\;{\mu}l/L\;CO_2)$ enviromental condition in the phytotron equipped with high density lamp$(1000\;{\mu}Em^{-2}S^{-1})$ and $28/22^{\circ}C$ temperature cycle for 35 days after transplanting(DAT). At 35 DAT, phosphorus deficiency decreased total dry mass by 64% in $CO_2$ enrichment condition, and 51% in control $CO_2$ condition. Total leaf area was reduced significantly by phosphorus deficiency in control and enriched $CO_2$ condition but specific leaf weight was increased by P deficiency. Phosphorus deficiency significantly reduced photosynthetic rate(carbon exchange rate) and internal $CO_2$ concentration in leaf in both $CO_2$ treatments, but the degree of stress was more severe under $CO_2$ enrichment condition than under control $CO_2$ environmental condition. In phosphorus sufficient plants, $CO_2$ enrichment increased nodule fresh weight and total nitrogenase activity(acetylene reduction) of nodule by 30% and 41% respectively, but specific nitrogenase activity of nodule and nodule fresh weight was not affected by $CO_2$ enrichment in phosphorus deficient plant at 35 DAT. Total nitrogen concentrations in stem, root and nodule tissue were significantly higher in phosphorus sufficient plant grown under $CO_2$ enrichment, but nitrogen concentration in leaf was reduced by 30% under $CO_2$ enrichment. These results indicate that increasing $CO_2$ concentration does not affect plant growth under phosphorus deficient condition and phosphorus stress might inhibit carbohydrate utilization in whole plant and that $CO_2$ enrichment could not increase nodule formation and functioning under phosphorus deficient conditions and phosphorus has more important roles in nodule growth and functioning under $CO_2$ enrichment environments than under ambient condition.

• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.534-538
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• 2017

In this study, the molecular weight controlled pitches derived from pyrolyzed fuel oil (PFO) were prepared using solvent extraction and were carbonized. Electrochemical characteristics of lithium battery anode materials were investigated using these petroleum pitches. Three pitch samples prepared by the thermal reaction were 3903 (at $390^{\circ}C$ for 3 h), 4001 (at $400^{\circ}C$ for 1 h) and 4002 (at $400^{\circ}C$ for 2 h). The prepared hexane insoluble pitches were analysed by XRD, TGA, SEM and Gel permeation Chromatography (GPC). The electrochemical characteristics of the PFO-derived pitch as an anode material were investigated by constant current charge/discharge, cyclic voltammetry and electrochemical impedance tests. The coin cell using pitch (4001) and the electrolyte of $LiPF_6$ in organic solvents (EC : DMC = 1 : 1 vol%, VC 3 wt%) has better initial capacity (310 mAh/g) than that of other pitch coin cells. Also, this carbon anode showd a high initial efficiency of 82%, retention rate capability at 2 C/0.1 C of 90% and cycle retention of 85%. It was found that modified pitches improved the cycling and rate capacity performance.

• Fire Science and Engineering
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• v.34 no.4
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• pp.1-6
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• 2020

In this study, the authors measured voltage and current waveforms in real time during a serial arc discharge. The analysis results of the arc discharge radiation patterns exhibited intermittent discharge, arc growth, creation of a heat generating area, occurrence of plume, and formation of a red heat area, which proceeded in that order. When the serial arc discharge was introduced, the current and voltage waveforms exhibited periodicity as sine waves. It was also observed that a restriking transient voltage occurred when the waveform changed from positive (+) to negative (-) and vice versa. When the discharge proceeded, the amount of heat generated for 1 s and 600 s was approximately 0.317 mJ, and 190 mJ, respectively. The duration of the short circuit was approximately 1.66 ms, and in the case of the voltage waveform, it was evident that the electric potential increased to 49.9 V in the same cycle. Furthermore, when the discharge proceeded, the effective value (RMS value) of the current was approximately 1.72 A with a maximum current of approximately 2.53 A, whereas the effective value of the voltage was approximately 42.8 V with a maximum of approximately 208 V.

• Journal of Agricultural Extension & Community Development
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• v.16 no.2
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• pp.363-384
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• 2009

This study aimed at finding directions for Korean agriculture to establish a new paradigm of sustainable development. Various problematic issues and concerns in the environment necessitate the transformation of Korea's development paradigm from unconditional growth to "Green Growth" through new policies on green value and review of various advanced researches. In this research, the environment-friendly agriculture's problems, particularly in agribusiness were analyzed. Drawing from Michael Porter's Value Chain Analysis, this research developed a value chain model in agriculture that reflects the environment and the present situations. Future directions in the agriculture sector were also discussed. Korea realized food self-sufficiency through the green revolution in the early 1970s. However, a lot of problems have also occurred, including ground and water pollution and the destruction of ecosystems as a result of the overuse of pesticides and chemical fertilizers. In the late 1970s, the growing interest on environment-friendly agriculture led to the introduction of sustainable methods and techniques. Unfortunately however, these were not innovative enough to foster environment-friendly agriculture. Thereafter, the consumers' distrust on agricultural products has worsened and concerns about health have increased. In view of this, the Ministry of Food, Agriculture, Forestry and Fisheries introduced in December 1993 a system of Quality-Certified Products for organic and pesticide-free agri-foods. Although a fundamental step toward the sustainability of the global environment, this system was not enough to promote environment-friendly agriculture. In 2008, Korea's vision is for "Low Carbon Green Growth" to move forward while also coping with climate change. But primary sectors in a typical value chain do not consider the green value of their operations nor look at production from an environmental perspective. In order to attain sustainable development, there is a need to use less resources and energy than what is presently used in Korean agricultural and value production. The typical value chain should be transformed into a "closed-loop" such that the beginning and the end of the chain are linked together. Such structure allows the flow of materials, products and even wastes among participants in the chain in a sustained cycle. This may result in a zero-waste sustainable production without destroying the ecosystem.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.3
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• pp.268-276
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• 2015

In this study, $CO_2$ reduction type quaternary component high fluidity concrete was produced with more than 80% reduction in cement quantity to increase the use of industrial byproducts and enhance construction performance, thereby reducing $CO_2$ emissions. Furthermore, the quality properties, and $CO_2$ reduction performance of this concrete were evaluated. As a result of the quality evaluation of quaternary component blended high fluidity concrete with $CO_2$ reduction, the target performance could be achieved with a 80% or more reduction of cement quantity by mixing a large amount of industrial byproducts. The required performance level was obtained even though the flow, dynamic, and durability characteristics decreased a little compared to conventional mix. In addition, to analyze the $CO_2$ reduction performance of quaternary component blended high fluidity concrete with $CO_2$ reduction, the life cycle assessment (LCA) of the concrete was performed and the results showed that compared to the conventional mix, the carbon emissions decreased by 62.2% and the manufacturing cost by 24.5%.

• Journal of Bio-Environment Control
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• v.18 no.2
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• pp.112-118
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• 2009

To determine the effects of circulation frequency of nutrient solution, three frequencies of 10min. on/10min. off; 10min. on/110min. off; and 10min. on/1,430min. off. treatments were applied to leafy vegetable production using deep flow technique (DFT) systems and their growth and phytonutrient content were investigated. In the 10min. on/I,430min. off treatment, dissolved oxygen concentration (DOC) 17 days after treatment decreased to 2.8mg. $L^{-1}$, known to be a low DOC that causes hypoxia, and thereafter decreased to 1.5mg. $L^{-1}$ 20 days after treatment. Fresh weight of 7 leafy vegetables in the 10min. on/1,430min. off treatment was lower by 0${\sim}$24% than those in the 10min. on/110min. off treatment, and those in the 10min. on/10min. off was higher by -2${\sim}$34% than those in the 10min. on/110min. off treatment as control. As the more frequent circulation was applied, the higher phosphorous content and the lower carbon to nitrogen ratio (C/N ratio) and total ascorbic acid contents were resulted. Results indicate that the circulation frequency of 110min, on/110min. off could be recommended for the production of the tested leafy vegetables in DFT systems.