• Economic and Environmental Geology
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• v.50 no.6
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• pp.545-554
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• 2017

Birnessite is one of the dominant Mn (oxyhydr)oxide phases commonly found in soil and deep ocean environments. It typically occurs as nano-sized and poorly crystalline aggregates in the natural environment. It is well known that birnessite participates in a wide variety of bio/geochemical reactions as a reactive mineral phase with structural defects, cation vacancies, and mixed valences of structural Mn. These various bio/geochemical reactions control not only the fate and transport of inorganic and organic substances in the environment, but also the formation of diverse Mn (oxyhydr)oxides through birnessite transformation. This review assessed and discussed about the phase transformation of birnessite under a wide range of environmental conditions and about the potential geochemical factors controlling the corresponding reactions in the literature. Birnessite transformation to other types of Mn (oxyhydr)oxides were affected by dissolved Mn(II), dissolved oxygen, solution pH, and co-existing cation (i.e., $Mg^{2+}$). However, there still have been many issues to be unraveled on the complex bio/geochemical processes involved in the phase transformation of birnessite. Future work on the detail mechanisms of birnessite transformation should be further investigated.

• Economic and Environmental Geology
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• v.45 no.2
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• pp.195-204
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• 2012

Biomineralization has been explored for geochemical cycles and microbial tolerance mechanisms to metal toxicity. Here, we are introducing NanoFermentation which enables economic, environmentally friendly, requiring low input energy, and scalable manufacturing of nano-dimensioned magnetite. We are also focusing on controlling factors of crystallite size which can determine superparamagnetism and ferrimagnetism. Controlling factors are such as microbial species, temperature, incubation time, medium composition, substituted elements and their concentration, precursor type, reaction volume, precursor concentration density and their combinations. Crystallite size distribution of biomagnetite depends on the balance between nuclei generation and crystal growth. Biomineralization will elucidate elemental cycles on earth crust and microbial ecology as well as it will be applied to material sciences and devices via massive production of nanomaterials.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.408-408
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• 2021

지진에 의한 변동과 전조 현상을 규명하기 위한 다양한 연구들이 진행되었으며, 기존 연구들에서는 지진 발생의 주요 원인은 주로 단층 운동에 의한 지각 반응을 중심으로 분석하고 그 결과들을 제시하였다. 지하층에서 지진이 발생하나 발생의 원인은 지각뿐만 아니라 수환경과 연계된 인자들까지 존재하여 매우 다양하다. 즉, 지각, 토양, 토질 등 지하의 변동과 연관성이 매우 높고 수 많은 수환경자료들(지하수위, 라돈, ph, 기타 수질 요소)을 통해서 지각운동에 따른 변화와 지진발생 가능성에 대한 상관관계를 규명할 수 있는 가능성이 매우 높다. 기존 지진이 나타나는 주요 원인은 주로 활성 단층 운동에 의한 지각 반응의 영향으로 지진 발생 이전에 지각의 팽창과 변형에 의해 지하수, 지하수 수질요소(라돈, 전기전도도, 수온 등)의 지화학적 변동이 일어날 수 있는 가능성이 존재하며, 이러한 수환경 빅데이터는 지진 발생 가능성 증대와 재현기간 및 규모 증대 등 상관성이 매우 큰 것으로 분석된다. 본 연구에서는 국내발생하는 지진에 대한 경향성 분석을 통하여 내륙에서 발생하는 지진과 바다에서 발생하는 지진의 경향성 및 연관성을 분석하고자 한다. 또한 지진 발생 지역에 대하여 수환경 빅데이터(지하수위, 라돈, 수온, 전기전도도, 강수량 등)와 지진발생과의 상관관계를 분석하여 주요 원인을 제시하고자 한다.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.479-486
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• 2009

In natural environments, manganese (Mn) exists in the valence of +2, +3, and +4 and plays a pivotal role as a strong oxidant or reductant in the geochemical cycles of elements. Especially, Mn forms varying (oxyhydr)oxides. The oxidation state of structural Mn is characteristic to each oxide and is one of the most important factors controlling its geochemical behaviors such as solubility, sorption capacity, and redox potential. Therefore, it is important to elucidate processes governing Mn oxidation state in predicting the fate and transport of many redox sensitive elements in the environment. X-ray photoelectron spectroscopy (XPS) is a very useful method to determine the oxidation state of various elements in solid phases. In this study, the oxidation states of structural Mn in MnO, $Mn_2O_3$, $MnO_2$ were assessed based on the binding energy spectra of $Mn2p_{3/2}$ and Mn3s using XPS and were compared with those reported elsewhere. $Mn2p_{3/2}$ binding energies were determined as 640.9, 641.5, 641.8 eV for MnO, $Mn_2O_3$, $MnO_2$, respectively, which indicates that the binding energy increased with increasing Mn oxidation state. It was also noted that Ar etching may cause changes in electronic structure configuration on surface of the original sample.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.1
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• pp.56-68
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• 2005

We measured nitrate and other nutrients in sediment pore waters retrieved from three sites at the southern upper-tidal flats of the Ganghwa Island. Denitrification rate is estimated by applying a simple 1-D model to the nitrate profiles. Results from Jangwha and Dongmak sites are $7.8{\sim}9.4{\times}10^{-7}{\mu}mol{\cdot}cm^{-2}{\cdot}sec^{-1}$, and $1.4{\sim}3.6{\times}10^{-7}{\mu}mol{\cdot}cm^{-2}{\cdot}sec^{-1}$, respectively. Rates are comparable to those reported around the world in an order of magnitude. Denitrification was lower in summer. The rates were about 1.5 times higher at site where the surface sediments consist of relatively coarser particles. This implies that particle size would control the reactant supply to the subsurface sediment. One may claim the denitrification as an evidence of the biogeochemical purification function of tidal flat. However, the purification seems not a general attribute of a tidal flat when whole system is scrutinized by a thermodynamic criterion. Currently the term 'tidal flat' is used when describing the diverse coastal wetlands such as salt marshes, sandy tidal flats and muddy tidal flats, which exhibit quite different ecological functions. Thus it is worthy of mentioning that the classification of coastal wetlands on the basis of sedimentological characteristics and biogeochemical functions should facilitate our understanding.

• Economic and Environmental Geology
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• v.50 no.6
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• pp.423-433
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• 2017

Korea Institute of Geoscience and Mineral Resources and Department of Geological Survey and Mineral Exploration in Myanmar have explored the Kalaymyo chromitite deposit, Myanmar since 2013. It is now necessary to find a geochemical indicator for efficient mineral exploration in the future and building a 3D geological model for this ore deposit. Mantle podiform chromitite is a major type of Cr ore in this region, which is considered to be formed by mantle-melt interaction beneath the mantle-crust boundary of oceanic lithosphere. In this study we measured major element composition of spinels in harzburgite, dunite and chromitite, and examined the hypothesis that spinel Cr#(molar Cr/(Cr+Al)${\times}$100) can be used as a geochemical indicator in exploration for the Kalaymyo chromitite. The results show that there is a clear correlation between spinel Cr# and distribution of chromitite. The spinel Cr# of harzburgite increases with decreasing the distance from the chromitite bodies. The spinel composition is also closely associated with texture and occurrence of spinels. The high Cr# spinels (30-48) are subhedral to euhedral and enclosed by olivine whereas the low Cr# spinels (16-27) are anhedral and commonly associated with pyroxenes. Often the low Cr# spinels show symplectite intergrowths with pyroxenes, indicating their residual nature. These petrological and geochemical results suggest that the high Cr# spinels have resulted from mantle-melt interaction. We suggest that spinel Cr# can be used as a geochemical indicator for Cr ore exploration and as one of critical factors in 3D geological model in the Kalaymyo chromitite deposit.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.4
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• pp.385-392
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• 2008

In this study, seawater intrusion was assessed employing a kind of biological parameters such as Escherichia coli and Enterococcus faecalis while lab-prepared reclaimed water was recharged to prevent seawater intrusion. Chemical factors indicating seawater intrusion such as Cl$^-$, Ca$^{2+}$, Mg$^{2+}$ and specific conductivity were also simultaneously investigated where an ion exchange between a matrix in artificial aquifer and cations in solution was estimated. Both Escherichia coli and Enterococcus faecalis were shown to be very sensitive against degree of salinity during saline water intrusion. Enterococcus faecalis more strongly resisted against salinity than that of Escherichia coli. The ratio of Enterococcus faecalis divided by E. coli in the process of seawater intrusion increased up to more than 50$\sim$100 times in 18 hours whereas E. coli was died off more than 90% during pumping and recharge rate kept at 10 mL/min. However, when the rates of both recharge and pumping was kept at 5 mL/min, Enterococcus faecalis / Escherichia coli was sustained in the range of 2.5$\sim$5.0, while Escherichia coli showed dimished death rate. Chemical factors such as Cl$^-$, Ca$^{2+}$, Mg$^{2+}$ and specific conductivity showed more than 0.9 of high correlation each other well explaining the degree of seawater intrusion. The degree of ion exchange between artificial aquifer and saline water can be efficiently interpreted by both minus $\Delta$Na, $\Delta$Mg variation and positive $\Delta$Ca variation.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.25 no.2
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• pp.9-25
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• 2020

In 2010 and 2015, total 77 surface sediment samples were collected to assess the anthropogenic effects of trace metals in surface sediments of Garolim Bay, and the physical characteristics (particle size and specific surface area) and geochemical components (major (Al, Ca, Fe, K, Ba) and trace metals (Mn, Cs, Cr, Co, Ni, Cu, Zn, Pb), organic carbon and calcium carbonate) were analyzed. Mean grain size of Garolim Bay surface sediments ranged from 0.51-5.58 Ø (mean 3.98 Ø) and increased from the inlet of bay to the inner bay, and from the waterway to the land. Most of the metal concentrations except for some elements showed the similar distribution to those of mean grain size and specific surface area. As the particle size decreased and the specific surface area increased, the metal concentration increased. In order to estimate the factors controlling the concentration of trace metals, factor analysis was performed, and three factors were extracted (92.7% of the total variation). Factor 1 accounted for 71.3% of the total variation, which was a grain size factor. Factor 2 accounted for 14.2% of the total variation, Factor 3 accounted for 7.2% of the total variance. Enrichment factor was calculated using the particle size corrected background concentration. Metals with a enrichment factor of 1.5 or higher and the number of samples were 4 for Cr (St. 1, 16, 27, 39) and 1 for Pb (St. 39), but there were little differences in the concentrations of 1M HCl leached metals for these metals. The percentage of 1M HCl leached fraction to total metal concentration decreased in the order of Pb~Co>Cu>Zn~Mn>Ni>Cr. Comparing this value with contaminated and clean sediments in other coastal areas, the percentages for each metal were similar regardless of the trace metal levels in all regions. This fact might be resulted from the reaction between the 1M HCl solution and the different sediment constituents, indicating that there is a limit to apply this percentage of leached metal to the estimation of the contamination extent.