• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.1
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• pp.1-15
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• 1996

This study is concerned with the property changes(chemical and mechanical) of the used oil in diesel engine, which were sampled from a test engine with dynamometer and various cars. The properties of oil are TAN, viscosity, oxidation, ZDTP depletion factor and etc. Also the relation between the change of chemical and antiwear property of used oil was strongly related to ZDTP depletion factor as wall as the change of TAN(total acid number), sulfation and pentan unsoluble contents which were reated to the formation of protect film in sliding area. The oil used in pick-up(small) truck engine was deteriorated within the shortest distance than that of other cars. The antiwear property of used oil was decreased sharply as the running distance were over 5,000km. The oil used to mini bus was the least to deteriorate of properities for the funning distance.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.9 no.2
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• pp.64-72
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• 2004

We measured the vertical profiles of $O_2$, H$_2$S, and pH in sediment pore water beneath marine cage fish farms using a microsensor with a 25 ${\mu}{\textrm}{m}$ sensor tip size. The sediments are characterized by high organic material load. The oxygen consumption, hydrogen sulfide oxidation, and sulfate reduction rates in the microzonations (derived from the vertical distribution of chemical species concentration) were estimated by adapting a simple one-dimensional diffusion-reaction model. The oxygen penetration depth was 0.75 mm. The oxic microzonations were divided into upper and lower layers. Due to hydrogen sulfide oxidation within the oxic zone, the oxygen consumption rate was higher in the lower layer. The total oxygen consumption rate integrated with reaction zone depth was estimated to be 0.092 $\mu$mol $O_2$cm$^{-2}$ hr$^{-1}$ . The total hydrogen sulfide oxidation rate occurring within 0.7 mm thickness was estimated to be 0.030 $\mu$mo1 H$_2$S cm$^{-2}$ hr$^{-1}$ , and its turnover time in the oxic sediment layer was estimated to be about 2 minutes. This suggests that hydrogen sulfide was oxidized by both chemical and microbial processes in this zone. The molar consumption ratio, calculated to be 0.84, indicates that either other electron accepters exit on hydrogen sulfide oxidation, or elemental sulfur precipitation occurs near the $O_2$- H$_2$S interface. Total sulfate reduction flux was estimated to be 0.029 $\mu$mol cm$^{-2}$ hr$^{-1}$ , which accounted for more than 60% of total $O_2$ consumption flux. This result implied that the degradation of organic matter in the anoxic layer was larger than in the oxic layer.

• Journal of the Mineralogical Society of Korea
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• v.23 no.2
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• pp.107-115
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• 2010

Removal and mineralization of dissolved uranium by bacteria in KURT (KAERI Underground Research Tunnel), Korea Atomic Energy Research Institute (KAERI) was investigated. Two different bacteria, IRB (iron-reducing bacteria) and SRB (sulfate-reducing bacteria) was used, and minerals formed by these bacteria were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Compared to uranyl ions, ferric ions were preferentially reduced by IRB, showing that there is no significant reduction and removal of uranium. However, uranium concentration considerably decreased by addition of Mn(II). Results show that a sulfide mineral such as mackinawite (FeS) is formed by SRB respiration through combination of Fe(II) and S without manganese sulfide formation. In the presence of Mn(II), however, uranium is removed effectively, suggesting that the sorption and incorporation of uranium could be affected by Mn(II) onto the sulide minerals.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.67-73
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• 2019

We carried out basic research to evaluate covering material for improving and managing contaminated benthic environments in coastal areas. Changes in nutrient concentration such as phosphate, hydrogen sulfide of contaminated sediment, and pH, Oxidation Reduction Potential (ORP) were investigated through mesocosm experiments for 6 months by covering contaminated sediment with granulated coal ash. Calcium oxide eluted from the granulated coal ash was confirmed to neutralize acidified sediment by increasing pH through hydrolysis. Also, calcium oxide and silica eluted from the granulated coal ash adsorbed and precipitated with phosphate in the sediment. The concentration of phosphate in the sediment investigated decreased by ca. 84.31 %. Similarly, the concentration of hydrogen sulfide decreased by 133.5 mg/L in one month. The hydrogen sulfide is considered to have reacted with substances such as manganese oxide which were eluted from the granulated coal ash and precipitated. Also, it was concluded that the hydrogen sulfide was reduced since anaerobic conditions in the sediment weakened. According to the results of these mesocosm experiments, granulated coal ash was found to be effective to remediate and manage benthic environments by covering the surface layer of sediment.

• Resources Recycling
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• v.31 no.2
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• pp.49-55
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• 2022

In the present study, the thermodynamic evaluation of the sulfate-roasting process was conducted to extract vanadium from the Korean vanadium titano-magnetite ore. The leaching efficiency of vanadium and other impurities was analyzed for varying roasting temperatures and addition of Na₂SO₄. In the case of sulfate roasting, the roasting temperature was 200 ℃ higher than that previously observed Na₂CO₃ roasting. However, the higher leaching efficiency of vanadium and lower leaching efficiency of other impurities, such as aluminum and silicon, were observed. The high selectivity for the extraction of vanadium in sulfate roasting would result from the reaction mechanism between SO₂ gas and vanadium concentrate.

• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.24-31
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• 2008

Sulfate reducing bacteria (SRB) is universally distributed in the sediment, especially in marine environment. SRB reduce sulfate as electron acceptor to hydrogen sulfide in anaerobic condition. Hydrogen sulfide is reducing agent enhancing the reduction of the organic and inorganic compounds. With SRB, therefore, the degradability of organic contaminants is expected to be enhanced. Ferrous iron reduced from the ferric iron which is mainly present in sediment also renders chlorinated organic compounds to be reduced state. The objectives of this study are: 1) to investigate the reduction of TCE by hydrogen sulfide generated by tht growth of SRB, 2) to estimate the reduction of TCE by ferrous iron generated due to oxidation of hydrogen sulfide, and 3) to illuminate the interaction between SRB and ferrous iron. Mixed bacteria was cultivated from the sludge of the sewage treatment plant. Increasing hydrogen sulfide and decreasing sulfate confirmed the existence of SRB in mixed culture. Although hydrogen sulfide lonely could reduce TCE, the concentration of hydrogen sulfide produced by SRB was not sufficient to reduce TCE directly. With hematite as ferric iron, hydrogen sulfide produced by SRB was consumed to reduce ferric ion to ferrous ion and ferrous iron produced by hydrogen sulfide oxidation decreased the concentration of TCE. Tests with seawater confirmed that the activity of SRB was dependent on the carbon source concentration.

• Proceedings of the KSEEG Conference
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• 2003.04a
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• pp.53-56
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• 2003

폐광석에 함유되어 있는 중금속 원소는 물리ㆍ화학적 환경의 변화에 따라서 안정화 되어 자연적으로 정화가 진행되거나 혹은 재 용출될 수 있어 중요한 오염원으로 작용할 수 있다. 따라서 폐광석에 함유된 중금속이 흡착된 상태로 존재하는지, 광물형태(탄산염광물, 산화광물, 황산염광물 및 황화광물)로 존재하는지, 산화환경 혹은 환원환경에서 안정한 다른 광물의 결정 내에 치환된 형태로 존재하는 지를 규명하는 것은 물리화학적 환경변화에 따른 중금속의 거동(흡착반응, 탈착반응, 용해반응, 침전반응)을 예측할 수 있는 매우 유용한 평가 방법이라고 할 수 있다. (중략)

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.11 no.2
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• pp.95-102
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• 2013

There was a study for biological characteristics, except for physico-chemical and mineralogical properties, on the natural bentonite that is considered as a buffer material for the high-level radioactive waste disposal site. A bentonite slurry that was prepared from a local 'Gyeongju bentonite' in Korea was incubated in a serum bottle with nutrient media over 1 week and its stepwise change was observed with time. From the activated bentonite in the nutrient media, we can find a certain change of both solid and liquid phases. Some dark and fine sulfides began to be generated from dissolved sulfate solution, and 4 species of sulfate-reducing bacteria (SRB) were identified as living cells in samples that were periodically taken and incubated. These results show that sulfate-reducing (or metal-reducing) bacteria are adhering and existing in the powder of bentonite, suggesting that there may be a potential occurrence of longterm biogeochemical effects in and around the bentonite buffer in underground anoxic environmental conditions.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.6
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• pp.843-853
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• 2009

The sediment samples were collected from Seonakdong River and were analyzed for sulfide species such Acid Volatile Sulfide(AVS) and Elemental Sulfur(ES) and Chromium Reducible Sulfide(CRS). Then characteristics of the formation of sulfide species were investigated for six selected samples. Finally the relationship between environmental factors and sulfate reducing rate(SRR) was investigated using two selected samples. Concentrations of AVS and CRS were relatively high, which suggests that organics input to the sediments has been continued until recently and that potential of heavy metals leaching from the sediments is low. SRR in the sediments was closely related to fraction of fine particles(silt+clay) and also to dissolved organic carbon content of the sediment(DOCsed). The dependences of environmental factors such as organic content, temperature, sulfate concentration on the SRR was relatively strong in the selected experiments conducted with the samples from Noksan gate and Daejeo gate samples. The environmental factor dependencies were stronger in the Noksan gate samples than in the Daejeo gate samples, which is probably due to higher surface area of the Noksan gate sediments.

• Journal of Periodontal and Implant Science
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• v.37 no.1
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• pp.1-10
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• 2007

연구 목적 : 구취의 주된 화학적 요소는 휘발성 황 화합물 (VSCs)들이다. 이들은 치태, 설태, 타액과 혈액, 상피세포의 혐기성 그람 음성 세균에 의한 단백분해 변성으로 만들어 진다. 또한 구취는 치주질환과 타액내의 세균의 증가를 야기하는 불량한 구강 위생상태에서 기인한다고 보고되고 있다. 이 연구의 목적은 VSCs를 측정함으로 구취에 대한 비외과적 치주 치료의 영향을 평가하고, 타액내의 세균 수를 측정함으로써 VSCs와의 상관관계를 살펴보고자 하는 것이다. 연구 대상 및 방법 : 중등도의 만성치주염을 가지는 23명의 참가자들이 대조군과 실험군으로 분류되었다. 대조군은 구강위생교육 (치간청결기구와 혀세정 포함)만을 시행하였고 실험군은 구강위생교육과 함께 24시간 내에 전악 치석제거술과 치근활택술을 시행하였다. 치료 전과 치료 4주 후에 VSCs 농도를 $Halimeter^{(R)}$(Interscan Corp., CA, USA)를 사용하여 측정하였고 타액 시료는 혐기성과 호기성 조건에서 배양되었다. 결과 : 4주 후에 두 군 모두에서 휘발성 황화합물의 농도가 유의하게 감소하였고, 실험군에서의 감소량이 통계적으로 유의하게 더 크게 나타났다. 타액 내 세균의 배양에서 총세균수에 대한 혐기성 세균의 비율이 실험군에서만 통계적으로 유의하게 감소하였다. 그러나 세균의 비율과 휘발성 황화합물의 농도와의 상관관계는 낮게 나타났다. 즉 구취의 감소는 타액 요인 보다는 치주치료에 의한 다른 복합적인 인자의 작용에 의한 것으로 추론할 수 있었다. 결론 : 본 연구는 중등도의 치주염환자에서 구강위생교육만으로도 구취의 주요 화학적 요인인 휘발성 황화합물의 농도를 감소시킬 수 있으나 비외과적 치주치료를 동반하였을 때 더욱 큰 효과를 얻을 수 있는 것으로 해석된다. 그러나 실험 참가자의 수가 적었고 장기간의 분석이 이루어지지 않았으므로 앞으로 더 많은 연구가 구취에 대한 치주치료의 영향을 이해하기 위해서 필요할 것으로 사료된다.