• Journal of the Korean Electrochemical Society
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• v.17 no.3
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• pp.164-171
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• 2014

A highly sensitive and selective non-enzymatic glucose sensor has gained great attention because of simple signal transformation, low-cost, easily handling, and confirming the blood glucose as the representative technology. Until now, glucose sensor has been developed by the immobilization of glucose oxidase (GOx) on the surface of electrodes. However although GOx is quite stable compared with other enzymes, the enzyme-based biosensors are still impacted by various environment factors such as temperature, pH value, humidity, and toxic chemicals. Non-enzymatic sensor for direct detecting glucose is an attractive alternative device to overcome the above drawbacks of enzymatic sensor. Many efforts have been tried for the development of non-enzymatic sensors using various transition metals (Pt, Au, Cu, Ni, etc.), metal alloys (Pt-Pb, Pt-Au, Ni-Pd, etc.), metal oxides, carbon nanotubes and graphene. In this paper, we show that Ni-based nano-particles (NiNPs) exhibit remarkably catalyzing capability for glucose originating from the redox couple of $Ni(OH)_2/NiOOH$ on the surface of ITO electrode in alkaline medium. But, these non-enzymatic sensors are nonselective toward oxidizable species such as ascorbic acid the physiological fluid. So, the anionic polymer was coated on NiNPs electrode preventing the interferences. The oxidation of glucose was highly catalyzed by NiNPs. The catalytically anodic currents were linearly increased in proportion to the glucose concentration over the 0~6.15 mM range at 650 mV versus Ag/AgCl.

• Journal of agriculture & life science
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• v.45 no.6
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• pp.251-263
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• 2011

In order to investigate treatment effects of limestone and steel refining slag for paddy soils contaminated with arsenic and heavy metals, a lab-column test was carried out under reducing environments of flooded paddy soils. In conditions of the flooded paddy soils, at the point of time when iron and manganese were reduced and leached rapidly, heavy metals also leached rapidly, and some leachate samples from an untreated soil exceeded regulatory standards. On the contrary, all samples from soils treated with limestone 5% and steel refining slag 5% respectively were below the regulatory standards, showing much lower heavy metal concentrations than in the untreated soil. Arsenic increased continuously during the observation period according to its typical characteristics, and along with decreasing redox potential, arsenic was expected to leach as $H_3AsO_3$-of form $A^{3+}$ with high mobility and strong toxicity. Limestone and steel refining slag showed high treatment effects against heavy metals present in soil and steel refining slag especially showed the high treatment effects against arsenic.

• Resources Recycling
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• v.30 no.3
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• pp.30-40
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• 2021

The present study investigates the bioleaching efficiencies of arsenic via contact and non-contact mechanisms. The attachment of Acidithiobacillus ferrooxidans was restricted by a partition system comprising a semi-permeable membrane with a molecular weight cutoff of 12-14 kDa. The results were compared for two arsenic concentrations in the system (1.0% and 0.5% w/v) to maintain a homogeneous system. The overall bacterial performance was monitored by comparing total arsenic and iron concentrations, Fe ion speciation, pH, and solution redox potentials in flask bioleaching experiments over a period of 10 d. Our results indicated that bacterial attachment could increase arsenic extraction efficiency from 20.0% to 44.9% at 1.0 % solid concentrations. These findings suggest that the bacterial contact mechanism greatly influences arsenic bioleaching from mine tailings. Therefore, systems involving two-step or non-contact bioleaching are less effective than those involving one-step or contact bioleaching for the efficient extraction of arsenic from mine tailings.

• Journal of The Korean Society of Grassland and Forage Science
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• v.42 no.2
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• pp.108-113
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• 2022

Arsenic (As) uptake and accumulation from agricultural soil to rice vary depending on the soil environmental conditions such as soil pH, redox potential, clay content, and organic matter (OM) content. Therefore, these factors are important in predicting changes in the uptake and accumulation of As in rice plants. Here, we studied the chemical properties of As-contaminated and/or rice straw compost (RSC)-treated soils, the growth responses of RSC-applied rice plants under As-contaminated soils, the changes in As content of soil, and the relationship between As uptake and accumulation from the RSC-treated soils to the rice organs under As-contaminated soils. Rice plants were cultivated in 30 mg kg^-1 As-contaminated soils under three RSC treatments: 0 (control), 12, and 24 Mg ha^-1. No significant differences were indicated in the chemical properties of pre-experimental (before transplanting rice seedling) soils, with the exception of EC, OM, and available P₂O₅. As the treatment of RSC under 30 mg kg^-1 As-contaminated soils increased, EC, OM, and available P₂O₅ increased proportionally in soil. Increased soil RSC under As-contaminated soils increased shoot dry weight of rice plants at harvesting stage. As content in roots increased proportionally with RSC content, whereas As content in shoots decreased under As-contaminated soil at all stages of rice plants. Nevertheless, As accumulation were significantly decreased in both roots and shoots of RSC-treated rice plants than those in the plants treated without RSC. These results indicate that the use of RSC can mitigate As phytotoxicity and reduce As accumulation in rice plants under As-contaminated soils. Therefore, RSC can potentially be applied to As-contaminated soil for safe crop and forage rice production.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.3
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• pp.43-53
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• 2023

This batch experiment evaluated the impacts of major plant nutrient releases by applying the modified Hyperbola model on the leachates and N₂O emissions from incorporated rice hull biochar with organic fertilizer materials. The treatments consisted of the control as incorporated with organic fertilizer materials, the incorporated rice hull biochar with organic fertilizer materials, and the incorporated plasma-activated rice hull biochar with organic fertilizer materials under redox conditions. The results indicated that the maximum release amount of NH₄-N was 3486.3 mg L^-1 in the control, and their reduction rates of NH₄-N, NO₃-N, PO₄-P, and K were 8.0%, 17.5% 44.3.0% and 8.7%, respectively, relative to the control. In the control, the highest soluble amount of PO₄-P was 681.0 mg L^-1. The estimations for accumulated NH₄-N, NO₃-N, PO₄-P, and K-releases in all the treatments were significantly (p<0.01) fitted with a modified Hyperbola model. For greenhouse gas emissions, the lowest cumulative N₂O was 340.4 mg kg^-1 in the soil incorporated with plasma-activated rice hull biochar, and the reduction rates were 27.8% and 86.4% in the rice hull biochar and plasma-activated rice hull biochar treatments, respectively, compared to the control. Therefore, it concluded that the incorporated rice hull biochar can be especially useful for controlling PO₄-P release and N₂O emissions for bio-fertilizer applications.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.745-764
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• 2023

In the Republic of Congo, Banded iron formations (BIFs) occur in two areas: the Chaillu Massif and the Ivindo Basement Complex, which are segments of the Archean Congo craton outcropping in the northwestern and southwestern parts of the country. They show interesting potential with significant mineral resources reaching 2 Bt and grades up to 60% Fe. BIFs consist mostly of oxide-rich facies (hematite/magnetite), but carbonate-rich facies are also highlighted. They are found across the country within the similar geological sequences composed of amphibolites, gneisses and greenschists. The Post-Archean Australian Shale (PAAS)-normalized patterns of BIFs show enrichment in elements such as SiO₂, Fe₂O₃, CaO, P₂O₅, Cr, Cu, Zn, Nb, Hf, U and depletion in TiO₂, Al₂O₃, MgO, Na₂O, K₂O, Sc, Th, Ba, Zr, Rb, Ni, V. REE diagrams show slight light REEs (rare earth elements; LREEs) compared to heavy REEs (HREEs), and positive La and Eu anomalies. The lithological associations, as well as the very high (Eu/Eu^*)_SN ratios> 1.8 shown by the BIFs, suggest that they are related to Algoma-type BIFs. The positive correlations between Zr and TiO₂, Al₂O₃, Hf suggest that the contamination comes mainly from felsic rocks, while the absence of correlations between MgO and Cr, Ni argues for negligeable contributions from mafic sources. Pr/Pr^* vs. Ce/Ce^* diagram indicates that the Congolese BIFs were formed in basins with redox heterogeneity, which varies from suboxic to anoxic and from oxic to anoxic conditions. They were formed through hydrothermal vents in the seawater, with relatively low proportions of detrital inputs derived from igneous sources through continental weathering. Some Congolese BIFs show high contents in Cr, Ni and Cu, which suggest that iron (Fe) and silicon (Si) have been leached through hydrothermal processes associated with submarine volcanism. We discussed their tectonic setting and depositional environment and proposed that they were deposited in extensional back-arc basins, which also recorded hydrothermal vent fluids.

• Economic and Environmental Geology
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• v.56 no.1
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• pp.55-63
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• 2023

Variations in geochemical and mineralogical properties of the ferromanganese(Fe-Mn) crust reflect environmental changes. In the present study, geochemical and mineralogical analyses, including micro X-ray fluorescence and X-ray diffraction, were utilized to reconstruct the paleo-ocean environment of western Pacific Magellan seamount cluster. Samples of the Fe-Mn crust were collected using an epibenthic sledge from the open seamount XX (151° 51.12' 7.2" E and 16° 8.16' 9.6" N, 1557 meters below sea level) in the Western Pacific Magellan Seamount. According to the structure and phosphating status, the Fe-Mn crust of the OSM-XX can be divided into the following: phosphatizated (L4-L5), massive non-phosphatizated (L3), and porous non-phosphatizated (L1-L2) portions. All ferromanganese layers contain vernadite, and owing to the presence of carbonate fluorapatite (CFA), the phosphatizated portion (L4-L5) is rich in Ca and P. The massive non-phosphatizated section (L3) contains high Mn, Ni, and Co, whereas the porous non-phosphatizated portion (L1-L2), which comprises detrital quartz and feldspar, is rich in Fe. Variations in properties of the Fe-Mn crust from the OSM-XX reflect changes in the nearby marine environment. The formation of this crust started at approximately 51.87 Ma, and precipitation of the CFA during the global phosphatization event that occurred at approximately 36-32 Ma highlights an elevated sea level and low temperature during the associated period. The high Mn, Ni, and Co concentrations and elevated Mn/Fe ratios of samples from the massive phosphatizated portion indicate that the oxygen minimum zone (OMZ) was enhanced, and reducing conditions prevailed during the crust formation. The high Fe and low Mn/Fe ratios in the porous portion indicate a weak OMZ and dominantly oxidizing conditions. These data reflect environmental changes following the end of the Mi-1 glacial period in the Miocene-Oligocene boundary. Subsequently, Mn/Fe and Co/Mn ratios increased slightly in the outermost part of Fe-Mn crust because of the enhanced bottom current and OMZ associated with the continued cooling from approximately 9 Ma. However, the reduced carbonate dissolution rate in the Pacific Ocean from approximately 6 Ma decreased the growth rate of the Fe-Mn crust.

• 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.

• Economic and Environmental Geology
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• v.34 no.1
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• pp.13-23
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• 2001

Bentonite layers are intercalated within the basal conglomerates in the Tertiary sedimentary basins of Kampo, Janggi and Pohang, southeastern Korea. Eighteen samples of the bentonites went through X-ray diffraction, scanning electron microscopy, heavy mineral analyses, chemical analyses and oxygen, hydrogen stable isotope analyses to define the mineralogical characters of the bentonites. Heavy minerals such as zircons, apatites, amphiboles and biotites separated from bentonites show clean and euhedral surfaces, which are the characteristic features of volcanic origin. But biotites from the Chunbook Conglomerate are found as altered and heavily broken flakes which implies longer transportation of these bentonites. $TiO_{2}/Al_{2}O_{3} ratios of <2 $\mu$m particle fractions (the Chunbook Conglomerate 0.031; Janggi 0.029; Kampo 0.025) suggest that those are originated from volcanic tuffs. That is, the higher the value is, the more mafic in chemical compositions of the original tuffs. Authigenic montmorillonite and zeolite minerals were observed by SEM, which indicates diagenesis origin of bentonites. But the samples from the Chunbook Conglomerate showed only chaotically packed clay flakes in the matrix of sands or conglomerates, which implies detrital influence, not authigenic origin. The structural formulae of montmorillonite from these basins reflects their environment of formation. Fe (Ⅵ) can show the redox condition of its past environment and much lower $Fe^{2+}(Ⅵ)/Fe^{3+}(Ⅵ)$ ratios in montmorillonite of the Chunbook Conglomerate imply the greater oxidizing influence. Calculated burial depths from oxygen stable isotope data of the samples from the Chunbook Conglomerate generally fall to the range of 929~963 m whereas the real burial depth of this area is only 530~580 m. This could be explained as the bentonites of the Chunbook conglomerate had not been formed in situ. Discriminant analyses with the data from chemical analyses and structural formulae of montmorillonites show that bentonites from three different basins could definitely be distinguished with each other. This result arises from the different chemical compositions of original volcanic ashes and the difference of sedimentary environments.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.847-870
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• 2023

The safe disposal of high-level radioactive waste requires accurate predictions of the long-term geochemical behavior of radionuclides. To achieve this, the present study was conducted to model geochemical behaviors of uranium (U), plutonium (Pu), and palladium (Pd) under different hydrogeochemical conditions that represent deep groundwater in Korea. Geochemical modeling was performed for five types of South Korean deep groundwater environment: high-TDS saline groundwater (G1), low-pH CO₂-rich groundwater (G2), high-pH alkaline groundwater (G3), sulfate-rich groundwater (G4), and dilute (fresh) groundwater (G5). Under the pH and Eh (redox potential) ranges of 3 to 12 and ±0.2 V, respectively, the solubility and speciation of U, Pu, and Pd in deep groundwater were predicted. The result reveals that U(IV) exhibits high solubility within the neutral to alkaline pH range, even in reducing environment with Eh down to -0.2 V. Such high solubility of U is primarily attributed to the formation of Ca-U-CO₃ complexes, which is important in both G2 located along fault zones and G3 occurring in granitic bedrocks. On the other hand, the solubility of Pu is found to be highly dependent on pH, with the lowest solubility in neutral to alkaline conditions. The predominant species are Pu(IV) and Pu(III) and their removal is predicted to occur by sorption. Considering the migration by colloids, however, the role of colloid formation and migration are expected to promote the Pu mobility, especially in deep groundwater of G3 and G5 which have low ionic strengths. Palladium (Pd) exhibits the low solubility due to the precipitation as sulfides in reducing conditions. In oxidizing condition, anionic complexes such as Pd(OH)₃^-, PdCl₃(OH)₂^-, PdCl₄^2-, and Pd(CO₃)₂^2- would be removed by sorption onto metal (hydro)oxides. This study will improve the understanding of the fate and transport of radionuclides in deep groundwater conditions of South Korea and therefore contributes to develop strategies for safe high-level radioactive waste disposal.