• Applied Chemistry for Engineering
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• v.22 no.2
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• pp.167-172
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• 2011

In this work, the effect of surface treatment on mesoporous carbons (MCs) supports was investigated by analyzing surface functional groups. MCs were prepared by a conventional templating method using mesoporous silica (SBA-15) for using catalyst supports in direct methanol fuel cells (DMFCs). The MCs were treated with different phosphoric acid ($H_3PO_4$) concentrations i.e., 0, 1, 3, 4, and 5 M at 343 K for 6 h. And then Pt-Ru was deposited onto surface treated MCs (H-MCs) by chemical reduction method. The characteristics of Pt-Ru catalysts deposited onto H-MCs were determined by specific surface area and pore size analyzer, X-ray diffraction, X-ray photoelectron, transmission electron microscopy, and inductive coupled plasma-mass spectrometer. The electrochemical properties of Pt-Ru/H-MCs catalysts were also analyzed by cyclic voltammetry experiments. From the results of surface analysis, an oxygen functional group was introduced to the surface of carbon supports. From the results, the H4M-MCs carbon supports surface treated with 4 M $H_3PO_4$ led to uniform dispersion of Pt-Ru onto H4M-MCs, resulting in enhancing the electro-catalytic activity of Pt-Ru catalysts.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.28 no.3
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• pp.95-120
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• 2023

Methane (CH₄) is a key greenhouse gas in the atmosphere with 85 times greater greenhouse potent relative to carbon dioxide (CO₂). The atmospheric concentration of CH₄ is rapidly increasing due to the intensive usage of CH₄ and the thawing of the cryosphere. Additionally, with the current warming of ocean water, the dissociation of gas hydrates, an ice-like compound and the largest reservoir of CH₄ on Earth, is expected to occur, resulting in the release of CH₄ from the seafloor into the overlying water and atmosphere. Moreover, bottom water hypoxia is another concern that potentially introduces greenhouse gases into the atmosphere. With ongoing global warming and eutrophication, the size and duration of bottom water hypoxia are rapidly increasing. These low-oxygen conditions would relocate the redox zone shallower in sediment or in the water column, causing the release of CH₄ into the atmosphere and thereby intensifying global warming. However, there exists a gap in the understanding of CH₄ dynamics including its generation in relation to bottom water hypoxia. Therefore, this review article aims to understand the relationship between CH₄ and bottom water hypoxia and to draw attention to CH₄ investigation in Korea.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.765-779
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• 2023

The Daum Vent Field (DVF) was newly discovered in the Central Indian Ridge during the hydrothermal expedition by the Korea Institute of Ocean Science & Technology (KIOST) in 2021. In this paper, we describe the detailed mineralogy and geochemistry of hydrothermal chimney and mound to understand the nature of hydrothermal mineralization in the DVF. The mineral assemblages (pyrite±sphalerite±chalcopyrite) of dominant sulfides, FeS contents (mostly <20 mole %) of sphalerite, and (Cu+Zn)/Fe values (0.001-0.22) of bulk compositions indicate that the DVF has an strong affinity with basaltic-hosted seafloor massive sulfide (SMS) deposit along the oceanic ridge. Combined with the predominance of colloform and/or dendritic-textured pyrite and relatively Fe-poor sphalerite in chimneys, the fluid-temperature dependency of trace element systematics (Co, Mn, and Tl) between chimney and mound indicates that the formation of mound was controlled by relatively reducing and high-temperature fluids compared to chimney. The δ³⁴S values (+8.31 to +10.52‰) of pyrite reflect that sulfur and metals were mainly leached from the associated basement rocks (50.6-61.3%) with a contribution from reduced seawater sulfur (38.7-49.4%). This suggests that the fluid-rock interaction, with little effect of magmatic volatile influx, is an important metal source for the sulfide mineralization in the DVF.

• Journal of Soil and Groundwater Environment
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• v.10 no.1
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• pp.43-57
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• 2005

Twelve bottom sediments and three cores were collected in Juam reservoir for a study on transportation, which was controlled by particle grain size (2mm-200{\mu}m,\;200-100{\mu}m,\;100-50{\mu}m,\;50-20{\mu}m,\;<20{\mu}m), and vertical distribution of heavy metals. Sediment cores were sliced into 2 to 5 cm intervals to measure heavy metal concentrations in interstitial water and sediments with depth. Pb isotopic compositions of core samples were determined to calculate sedimentation rate. Regardless of sampling sites, levels of heavy metals and trace elements in bottom sediments are nearly constant with mean values of $14.9\;{\mu}g/g\;for\;As,\;0.81{\mu}g/g\;for\;Cd,\;30.7{\mu}g/g\;for\;Cu,\;34.7{\mu}g/g\;for\;Ni,\;63.3{\mu}g/g\;for\;Pb\;and\;87.9{\mu}g/g\;for\;Zn$. In general, Cu, Pb, Zn, Wi, and Cr in fraction of $<20{\mu}m$ exhibit the highest concentration, but content of As is the highest in grain size of $2\;mm-200\;{\mu}m$ and $200-100\;{\mu}m$. Fe and Mn occur as the dissolved compositions of the highest concentrations in interstitial waters and increase in their concentrations toward lower part of cores. On the contrary, concentrations of Zn and Cu show the highest value in the uppermost part in cores, suggesting these elements are released from reductive dissolution of hydroxides and oxidation of organic matters under different redox conditions. The highest accumulations of Cu, Ni, Pb, and Zn contents in the sediment cores are observed at 0-4 cm layers, and concentrations of Cu and Pb are especially high, implying these heavy metals are originated from anthropogenic sources. The apparent sedimentation rate estimated using unsupported $^{210}Pb$ is 0.91 cm $year^{-1}$, corresponding about 10 cm sedimentation in total depth since construction of Juam dam. These results will provide available information for management of bottom sediment in Juam reservoir.

• Microbiology and Biotechnology Letters
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• v.40 no.2
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• pp.128-134
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• 2012

Foot and mouth disease (FMD) is one of the most notorious and contagious viral diseases afflicting cloven-hoofed animals. In this study, the physicochemical properties of leachate from a FMD landfill site at 773-1, Waryong, Andong, Korea and the ground water from 777, Waryong, Andong, Korea, were analyzed for 1 year from December $10^{th}$ 2010 to November $17^{th}$ 2011. The leachate was collected from the FMD landfill site during March, May, July, September and November, 2011 and changes in pH, brix, water content, insoluble solids, crude proteins, crude lipids, total and reducing sugars and ash content were determined. Considering the annual profiles of temperature and rainfall at the FMD landfill site, the dramatic changes in the physicochemical properties of the leachate from March to July, and especially from May to July, such as increases in pH, and a rapid reduction of brix and organic matter, may be closely linked to the growth of microorganisms in the leachate. The sharp decreases in the concentration of biominerals, such as Mg, Ca, and Fe from 1073, 4311 and 56.2 ppm in March to 151, 78, and 0.1 ppm in November, further suggest that decreases in organic matter in the leachate result from degradation by microorganisms originating from the intestines of the livestock. Analysis of the profiles of the organic materials in the leachate revealed that the properties of the leachate were similar to those of excremental matter-derived water. These results could be applied to a number of fields for the analysis of organic matter behavior, the development of the degradation process, and risk analysis in the environment for hygiene and food industries, of leachate from FMD landfill sites.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.7 no.1
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• pp.1-7
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• 2009

This study has been focused on determining the chemical composition of $^{14}C$ - in terms of both organic and inorganic $^{14}C$ contents - in reactor coolant from 3 different PWR's reactor type. The purpose was to evaluate the characteristic of $^{14}C$ that can serve as a basis for reliable estimation of the environmental release at domestic PWR sites. $^{14}C$ is the most important nuclide in the inventory, since it contributes one of the main dose contributors in future release scenarios. The reason for this is its high mobility in the environment, biological availability and long half-life(5730yr). More recent studies - where a more detailed investigation of organic $^{14}C$ species believed to be formed in the coolant under reducing conditions have been made - show that the organic compounds not only are limited to hydrocarbons and CO. Possible organic compounds formed including formaldehyde, formic acid and acetic acid, etc. Under oxidizing conditions shows the oxidized carbon forms, possibly mainly carbon dioxide and bicarbonate forms. Measurements of organic and inorganic $^{14}C$ in various water systems were also performed. The $^{14}C$ inventory in the reactor water was found to be 3.1 GBq/kg in PWR of which less than 10% was in inorganic form. Generally, the $^{14}C$ activity in the water was divided equally between the gas- and water- phase. Even though organic $^{14}C$ compound shows that dominant species during the reactor operation, But during the releasing of $^{14}C$ from the plant stack, chemical forms of $^{14}C$ shows the different composition due to the operation conditions such as temperature, pH, volume control tank venting and shut down chemistry.

• Journal of the Korean Society of Groundwater Environment
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• v.6 no.2
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• pp.59-65
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• 1999

Both the groundwater changes due to different pumping rates and the geochemistry of thermal waters in the Suanbo area are considered in this study. The observation of groundwater level change since 1991 shows that the change is directly correlated with pumping rates of thermal waters and reveals the retardation of ca. 5 weeks after pumping. The hydrogeological aquifer in the area is under reducing condition. The thermal waters are of Na-HCO$_3$ type. and are alkaline (pH=8.5∼8.7) with low TDS values (274∼284 mg/l) and high concentrations of Na (68∼72 mg/l). F (6.4∼8.9 mg/l), and HCO$_3$(136∼146 mg/l). Oxygen and hydrogen isotope ratios of thermal water indicate a meteoric water origin. The activities of Rn-222 and Ra-226 in both thermal water and local groundwater were determined to delineate possible geochemical controls on the Rn-222 and Ra-226. The Rn-222 concentrations are several orders of magnitude greater than the Ra-226 concentrations. The concentrations of Rn-222 range from 190 to 7.490 pCi/1 with an average of 2,522 pCil/l. and those of Ra-226 average 0.32 pCi/1 with the range from 0.25 to 0.42 pCi/1. The concentrations of Rn-222 and Ra-226 are inversely correlated with EC and alkalinity. The pH it positively correlated with Ra-226. The correlation between Rn-222 and Ra-226 is poor. Thermal waters in the study area are produced from highly fractured phyllite. The thermal water qualify. CSAMT (controled-source audiofrequency magnetotelluric) prospecting, and petrological evidences, however, indicate that the heat is possibly transmitted through deep normal faults reaching a deep granite batholith, and the phyllite acts only as a groundwater pathway.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.3
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• pp.215-225
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• 1999

To study the vertical variations of major elements, trace elements and rare earth elements(REEs) contents in deep-sea sediments, six cores from Korea Deep-sea Environmental Study area(KODES) were analyzed. Topmost sediment layers of KODES area are divided into two Units; brown-colored and peneliquid Unit I and pale brown-colored and relatively solidified Unit II. Contents of major elements, REEs, Cu, Sr and Rb in each Unit are almost same, while contents of Mn, Ni and Co in Unit I are two or three times higher than those in Unit II. R-mode factor analysis represents that surface sediments are composed of alumino-silicate phase (AI-Ti-K-Mg-Fe-Rb-Ce), apatite phase (Ca-P-Cu-Sr-Trivalent Rare Earth Elements) and Mn-oxide phase(Mn-Ni-Co). Factor scores in silicate and apatite phases in each Unit are nearly same, whereas those in Mn-oxide phase in Unit I is higher than those in Unit II. While NilCu ratio in Unit I is two times higher than that in Unit II. We interprete the geochemical fractionation of Ni and Cu as a result that Ni can be remobilized in oxygen-depleted micro-environment in Units I and II and then easily reprecipitated in Unit I, while most of Cu supplied together with organic material is decomposed mostly in Unit I and sorbed into apatite.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.3
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• pp.115-120
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• 2016

$CeO_2$ is used as a co-catalyst with $TiO_2$ to improve the catalytic activity of $MnO_x$ and characterization of nano-sized powder is identified with de-NOx efficiency. A comparison between $MnO_x-CeO_2/TiO_2$ and single $CeO_2$ was conducted in terms of microstructural analysis to observe the behavior of $CeO_2$ in the ternary catalyst. The $MnO_x-CeO_2/TiO_2$ catalyst was synthesized by sol-gel method and the average particle size of the single $CeO_2$ is about $285{\mu}m$ due to the low thermal stability, whereas the particle size $MnO_x-CeO_2/TiO_2$ is about 130 nm. The strong interaction between Ce and Ti was identified through the EDS mapping by transmission electron microscopy (TEM). The improvement about 20 % of $de-NO_x$ efficiency is observed in the low-temperature ($150^{\circ}C{\sim}250^{\circ}C$) and vigorous oxygen exchange by well-dispersed $CeO_2$ is the reason of catalytic activity improvement.

• Resources Recycling
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• v.22 no.3
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• pp.57-64
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• 2013

Sulfurization reaction characteristics of $Eu_2O_3$, uranium oxides($UO_2$, $U_3O_8$), mixture of $Eu_2O_3$ and uranium oxides, Eu-doped uranium oxides($(U,Eu)O_2$, $(U,Eu)_3O_8$), and phase-separated products prepared by HOX (High temperature OXidation) of $(U,Eu)O_2$ were investigated in the temperature range from 400 to $800^{\circ}C$. Only $Eu_2O_3$ in the mixture of $Eu_2O_3$ and uranium oxides was converted into $Eu_3S_4$ by sulfurization reaction at $450^{\circ}C$ without reaction between them. Sulfurization reaction behavior of $(U,Eu)_3O_8$ and $(U,Eu)O_2$ up to $600^{\circ}C$ was similar to $U_3O_8$ and $UO_2$, respectively, while they were sulfurized into Eu-rich $(U,Eu)S_x$ and ${\alpha}-US_2$ at $800^{\circ}C$. In the sulfurization of RE-rich $(U,Eu)_4O_9$ and $U_3O_8$ prepared by high temperature oxidation, it was confirmed that RE-rich $(U,Eu)S_x$ and UOS phases were formed at $600^{\circ}C$. For Eu-rich $(U,Eu)O_2$ and $UO_2$ prepared by reduction of HOX products, it was identified that Eu-rich (U,Eu)OS was formed at $450^{\circ}C$ by sulfurization of Eu-rich $(U,Eu)O_2$, while $UO_2$ remained unreacted.