• Journal of the Korean GEO-environmental Society
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• v.5 no.4
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• pp.13-24
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• 2004

This study was carried out to plan the prevention of the generation and discharge of Acid Rock Drainage (ARD). The Acid Base Accounting(ABA) test was performed for geological materials such as pit wall, waste rock and stream sediments near the Imgi abandoned pyrophyllite mine in Busan, Korea. In addition, hydraulic characteristics were tested with the disk tension infiltrometer around the waste rock dump. Maximum Potential Acidity(MPA) of geological materials near the Imgi mine was 246.942kg $H_2SO_4/t$, and maximum Acid Neutralising Capacity(ANC) was 8.7kg $H_2SO_4/t$. These results indicate the pit wall and waste rock, except most of stream sediments are acid generating geological materials. These have salt and free hydrogen ion which resulted from oxidation of sulfides. Hence they could be convert rain water to acid rock drainage. Although the waste rock dump of the Imgi mine have very low infiltration rate, slopes of the waste rock dump have many "V" type erosion gullies and multi-layers. These gullies and multi-layers have coarse clastic particle layers which have very large hydraulic conductivity. Through this coarse clastic particle layer a large part of rain flow into ground. And also this layer could function as aeration path which induced oxidation of sulfide minerals and generation of ARD continuously.

• Applied Chemistry for Engineering
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• v.7 no.4
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• pp.768-776
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• 1996

Carbon Black has various advantageous properties such as reinforcement, tinting, weathering, chemical resistance, electrical resistance, etc., but it has poor affinity in the solution. The purpose of this study is to enhance dispersion in the aqueous solution by altering the surface characteristics. Two different treatments were applied for both channel black and furnace black respectively. Channel black was treated in alkaline solution to replace hydrogen of the carboxyl group with alkaline metal, Li, Na, K. Furnace black has few functional groups, and it was treated with $HNO_3$ to increase the number of functional group on carbon black. It was seen that the substitution of alkaline metal on the surface of channel black enhances the degree of dispersion. Also the higher the acid concentration and reaction temperature, the more the number of some functional groups on the furnace black. Reaction time was not seen to be effective.

• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.344-350
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• 2019

Durability is very important for the commercialization of membranes and electrode assemblies (MEA) developed for proton exchange membrane fuel cells (PEMFC). Durability evaluation of stationary PEMFC MEA has a problem that the voltage change rate should be measured for a long time over 1000 hours under constant current conditions. In this study, the electrochemical durability evaluation protocol of membranes (OCV holding method) using to vehicle MEAs was applied to the stationary MEA for the purpose of shortening the durability evaluation time. After operation of the stationary and automobile MEA for 168 hours under conditions of OCV, cathode oxygen, $90^{\circ}C$ and relative humidity of 30%, I-V, LSV, CV, impedance and FER were measured and compared. When the hydrogen permeability, OCV change, ionic conductivity, and fluorine flow rate, which represent the durability of the membrane after degradation, were all examined, it was shown that durability of stationary MEA membrane was better than that of vehicles MEA membrane. In addition, the electrode degradation of stationary MEA was smaller than that of vehicles MEA after degradation operation. It was possible to evaluate in a short time using automotive protocol that the durability of stationary MEA was superior that of vehicle MEA in terms of membrane and the electrode.

• Membrane Journal
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• v.32 no.6
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• pp.411-426
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• 2022

Energy plays a significant role in modern lifestyle because of our extensive reliance over energy-operating devices. Therefore, there is a need for alternative and green energy resources that can fulfill the energy demand. For this, fuel cell (FCs) especially anion exchange membrane fuel cells (AEMFCs) have gained tremendous attention over the other (FCs) due to their fast reaction kinetics without using noble catalyst and allow to use of cheaper polymers with high performance. But lack of highly conductive, chemically, and mechanically stable anion exchange membrane (AEM) still main obstacle to the development of high performance AEMFCs. Therefore, graphene-based polymer composite membranes came into the existence as AEMs for the FCs. The exceptional properties of the graphene help to improve the performance of AEMs. Still, there are lot of challenges in the graphene derivatives based AEMs because of their high tendency of agglomeration in polymer matrix which reduced their potential. To overcome this issue surface modification of graphene derivatives is necessary to restrict their agglomeration and conserved their potential features that can help to improve the performance of AEM. Therefore, this review focus on the surface modification of graphene derivatives and their role in the fabrication of AEMs for the FCs.

• Economic and Environmental Geology
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• v.41 no.1
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• pp.15-32
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• 2008

The hydrochemical and isotopic (stable isotopes and noble gas isotopes) analyses for hot spring waters, cold groundwaters and surface water samples from the Seokmodo hot spring area of the Ganghwa province were carried out to characterize the hydrogeochemical characteristics of thermal waters and to interpret the source of thermal water and noble gases and the geochemical evolution of hot spring waters in the Seokmodo geothermal system. The hot spring waters and groundwaters show a weakly acidic condition with the pH values ranging from 6.42 to 6.77 and 6.01 to 7.71 respectively. The outflow temperature of the Seokmodo hot spring waters ranges from $43.3^{\circ}C\;to\;68.6^{\circ}C$. Relatively high values of the electrical conductivities which fall between 60,200 and $84,300{\mu}S/cm$ indicate that the hot spring waters were mixed with seawater in the subsurface geothermal system. The chemical compositions of the Seokmodo hot spring waters are characterized by Na-Ca-Cl water type. On the other hand, cold groundwaters and surface waters can be grouped into three types such as the Na(Ca)-$HCO_3$, Na(Ca)-$SO_4$ and Ca-$HCO_3$ types. The ${\delta}^{18}O\;and\;{\delta}D$ values of hot spring waters vary from -4.41 to -4.47%o and -32.0 to -33.5%o, respectively. Cold groundwaters range from -7.07 to -8.55%o in ${\delta}^{18}O$ and from -50.24 to -59.6%o in ${\delta}D$. The oxygen and hydrogen isotopic data indicate that the hot spring waters were originated from the local meteoric water source. The enrichments of heavy isotopes ($^{18}O\;and\;^2H$) in the Seokmodo hot spring waters imply that the thermal water was derived from the diffusion Bone between fresh and salt waters. The ${\delta}^{34}S$ values ranging from 23.1 to 23.5%o of dissolved sulfate are very close to the value of sea water sulfate of ${\delta}^{34}$S=20.2%o in this area, indicating the origin of sulfate in hot springs from sea water. The $^3H/^4He$ ratio of hot spring waters varies from $1.243{\times}10^{-6}\;to\;1.299{\times}10^{-6}cm^3STP/g$, which suggests that He gas in hot spring waters was partly originated from a mantle source. Argon isotopic ratio $(^{40}Ar/^{36}Ar=298{\times}10^{-6}cm^3STP/g)$ in hot spring waters corresponds to the atmospheric value.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.2
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• pp.87-96
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• 2004

Studies were conducted to select the candidate buffer material for a high-level waste (HLW) repository in Korea. This paper presents the hydraulic properties, the swelling properties, the thermal properties, and the mechanical properties as well as the radionuclide release-retarding capacity of Kyungju bentonite as part of those studies. Experimental results showed that the hydraulic conductivities of the compacted bentonite were very low and less than $10^{-11}$m/s. The values decreased with increasing the dry density of the compacted bentonite. The swelling pressures were in the range of 0.66 MPa to 14.4 ㎫ and they increased with increasing the dry density. The thermal conductivities were in the range of 0.80 ㎉/m $h^{\circ}C$ to 1.52 ㎉/m $h^{\circ}C$. The unconfined compressive strength, Young's modulus and Poison's ratio showed the range of 0.55 ㎫ to 8.83 ㎫, 59 ㎫ to 1275 ㎫, and 0.05 to 0.20, respectively, when the dry densities of the compacted bentonite were 1.4 Ms/㎥ to 1.8 Mg/㎥. The diffusion coefficients in the compacted bentonite were measured under an oxidizing condition. The values were $1.7{\times}10^{-10}$m^2$/s to 3.4{\times}10^{-10}$m^2$/s for electrically neutral tritium (H-3), 8.6{\times}10^{-14}$m^2$/s to 1.3{\times}10^{-12}$m^2$/s for cations (Cs, Sr, Ni), 1.2{\times}10^{-11}$m^2$/s to 9.5{\times}10^{-11}$m^2$/s for anions (I, Tc), and 3.0{\times}10^{-14} $m^2$/s to 1.8{\times}10^{-13}$m^2$/s $for actinides (U, Am), when tile dry densities were in the range of 1.2 Mg/㎥ to 1.8 Mg/㎥. The obtained results will be used in assessing the barrier properties of Kyungju bentonite as a buffer material of a repository in Korea.n Korea.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.3
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• pp.189-197
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• 2012

Geochemical composition of fracture filling minerals and groundwater was investigated to characterize geochemical characteristics of groundwater system at the KURT site. Minerals such as calcite, illite, laumontite, chlorite, epidote, montmorillonite, and kaolinite, as well as I/S mixed layer minerals were detected in the minerals extracted from the fracture surfaces of the core samples. The groundwater from the DB-1, YS-1 and YS-4 boreholes showed alkaline conditions with pH of higher than 8. The electrical conductivity (EC) values of the groundwater samples were around $200{\mu}S/cm$, except for the YS-1 borehole. Dissolved oxygen was almost zero in the DB-1 borehole indicating highly reduced conditions. The Cl- concentration was estimated around 5 mg/L and showed homogeneous distribution along depths at the KURT site. It might indicate the mixing between shallow groundwater and deep groundwater. The shallow groundwater from boreholes showed $Ca-HCO_3$ type, whereas deep groundwater below 300 m from the surface indicated $Na-HCO_3$ type. The isotopic values observed in the groundwater ranged from -10.4 to -8.2‰ for ${\delta}^{18}O$ and from -71.3 to -55.0‰for ${\delta}D$. In addition, the isotope-depleted water contained higher fluoride concentration. The oxygen and hydrogen isotopic values of deep groundwater were more depleted compared to the shallow groundwater. The results from age dating analysis using $^{14}C$ indicated relatively younger (2000~6000yr old) groundwater compared to other european granitic groundwaters such as Stripa (Sweden).

• Korean Journal of Environmental Biology
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• v.31 no.1
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• pp.37-44
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• 2013

This study was to investigate water quality and biotic community characteristics in Juam Lake. In water quality, water temperatures was $3.8{\sim}21.2^{\circ}C$, 6.7~8.6 in pH, $64{\sim}76{\mu}s\;cm^{-1}$ in Conductivity, $5.3{\sim}13.2mg\;L^{-1}$ in DO, $2.5{\sim}3.3mg\;L^{-1}$ in COD, $1.0{\sim}5.1mg\;L^{-1}$ in SS, $0.622{\sim}0.841mg\;L^{-1}$ in T-N, $0.007{\sim}0.019mg\;L^{-1}$ in T-P and $2.8{\sim}8.8mg\;m^{-3}$ in Chl-a. Revised Carlson's Index (TSIm) assessment using total phosphorus (TP) and chlorophyll-a domonstrated that the trophic states of Juam Lake were rated as mesotrophic. A total of 53 species of phytoplankton were identified. They were 28 Bacillariophyceae, 13 Chlorophyceae, 3 Cyanophyceae, and 9 Other algal taxa. The standing crops of phytoplankton was ranged from $113cells\;mL^{-1}$ to $2,909cells\;mL^{-1}$. A total of 16 species of zooplankton were identified (10 rotifers, 4 cladocerans and 2 copepods). Total zooplankton abundance was $309ind.\;L^{-1}$ to $435ind.\;L^{-1}$. The collected benthic macroinvertebrates from the surveyed sites in Juam Lake were 1,038 individuals, 33 species, 21 families and 12 orders. A dominant species was Uracanthella rufa and a subdominant species was Ecdyonurus kibunensis. Hydrophytes recorded from Juam Lake were identified 9 taxa. Emerged plants, floating plants among the hydrophytes was classified 8, 1 taxa, respectively. Ecosystem disturbance wildplant by Environment Ministry found were Paspalum distichum var. distichum and Ambrosia artemisiaefolia. A total of 30 species (6 families) were collected fishs from Juam Lake. There were 10 Korean endemic species (33.3% of collected species number) and 3 exotic species (10.0%).

• Korean Journal of Ecology and Environment
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• v.35 no.1 s.97
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• pp.52-61
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• 2002

This research was conducted to evaluate the effect of forest management practices on pH and electrical conductivity to get fundamental information on water purification capacity after forest operation. Rainfall, throughfall and stemflow　were　sampled at the study sites which consist of Abies holophylla and Pinus koraiensis　in Gwangreung Experimental Forest for S months from May to November 1999. Mean pH of the throughfall of the beginning of the event was higher in management (thinning and pruning) sites of Abies holophylla and Pinus koraiensis stands than nonmanagement site of Abies holophylla and Pinus koraiensis stands. In addition, pH of the throughfall of the total amount of the event showed similar trends which are higher pH in the management sites compared with the non- management sites. This result indicates that managements such as thinning and pruning improve tree butler capacity of rainfall pH. According to the linear regression results, pH of the throughfall of the total amount of the event in non-management sites = 0.735${\times}$pH of the throughfall of the beginning of the event in non-management sites+1.849 ($R^2\;=\;0.82$) and pH of the throughfall of the total amount of the event in management sites= 0.863${\times}$pH of the throughfall of the beginning of the event in management sites +1.0242 ($R^2\;=\;0.87$). In case of stemflow pH, pH of the sternflow of the total amount of　the event in non-management sites = 0.53${\times}$pH of the stemflow of the beginning of　the event in non- management sites+2.7709 ($R^2\;=\;0.64$) and pH of the stemflow of the total amount of the event in management sites = 0.5854${\times}$pH of the stemflow of the beginning of the event in management sites+2.7045 ($R^2\;=\;0.65$). Electrical conductivity (EC) of the throughfall of the beginning and total amount of the event was highest in non- management site in Abies holophylla, followed by management sites in fsies Abies holophylla, non-management site in Pinus koraiensis, and management sites in Pinus koraiensis stands, respectively. According to the linear regression results, EC of the throughfall of the total amount of the event in non-managementsites = 0.4045${\times}$EC of the throughfall of the beginning of the event in non-management sites+26.766 ($R^2\;=\;0.69$) and EC of the throughfall of the total amount of the event in management sites = 0.6002${\times}$EC of the throughfall of the beginning of the event in management sites+8.0184 ($R^2\;=\;0.54$). In case of stemflow EC, EC of thestemflow of the total amount of the event in non-management sites = 0.6298${\times}$EC of the stemflow of the beginning of the event in non-management sites+11.582 ($R^2\;=\;0.72$) and pH of the stemflow of the total amount of the event in management sites =0.602${\times}$pH of the stemflow of the beginning of the event in management sites+20.783($R^2\;=\;0.49$).