• Economic and Environmental Geology
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• v.53 no.6
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• pp.703-713
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• 2020

In many geological fields, including hydrogeology, it is of great importance to determine the heterogeneity of the subsurface media. This study briefly introduces the concept and theory of the method that can estimate the hydraulic properties of the media constituting the aquifer, which was recently introduced by Park (2020). After the introduction, the method was applied to the synthetic aquifer to demonstrate the practicality, from which various implications were drawn. The introduced technique uses a global optimization technique called the covariance matrix adaptation evolution strategy (CMA-ES). Conceptually, it is a methodology to characterize the aquifer heterogeneity by assimilating the groundwater level time-series data due to the imposed hydraulic stress. As a result of applying the developed technique to estimate the hydraulic conductivity of a hypothetical aquifer, it was confirmed that a total of 40000 unknown values were estimated in an affordable computational time. In addition, the results of the estimates showed a close numerical and structural similarity to the reference hydraulic conductivity field, confirming that the quality of the estimation by the proposed method is high. In this study, the developed method was applied to a limited case, but it is expected that it can be applied to a wider variety of cases through additional development of the method. The development technique has the potential to be applied not only to the field of hydrogeology, but also to various fields of geology and geophysics. Further development of the method is currently underway.

• Journal of Wetlands Research
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• v.24 no.2
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• pp.142-154
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• 2022

Arsenic (As) contamination in groundwater is one of the main problems in Bangladesh. As toxicity causes serious human health problems such as edema, skin cancer, bladder cancer, lung cancer, hyperkeratosis, premature birth, and black foot disease. As contamination in groundwater mainly originates from the geological characteristics of the area due to the influence of anthropogenic activities. Since most of the people in Bangladesh rely on tube well for drinking water, it is necessary to investigate the current status of As pollution and identify the treatment technologies that can be used to provide arsenic-free drinking water in water-scarce areas. A total of 92 papers were reviewed in this study to present a complete overview of the recent status of groundwater As contamination in Bangladesh and different low-cost remediation technologies. A method for evaluating the relative feasibility of different treatment technologies was also utilized to determine the most appropriate technologies for groundwater As treatment in Bangladesh. The districts with the highest groundwater As contamination include Brahamanbariya, Tangail, Barisal, Pabna, Patuakhali, Kurigram, Magura, and Faridpur, with concentrations exceeding 0.05 mg/L. Only six districts had relatively low groundwater arsenic concentrations (0.01 mg/L), including Kushtia, Khagrachari, Jessore, Dinajpur, Meherpur, and Munshiganj. There were a number of technologies used for treating As in water, but aerated electrocoagulation, Mg-Fe-based hydrotalcite-like compound, and electro-chemical As remediation (ECAR) reactor were found to be the most feasible treatment methods for As. Overall, the investment, operational, and maintenance costs, availability of materials, and expertise requirements should be considered when selecting the most appropriate treatment method for As in water.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.283-283
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• 2020

국가의 논의 타작물 재배 권장 정책과 농한기 수익을 위해서 동절기에도 농사가 가능한 시설농업이 발달했으며, 1990년 초부터 재배면적이 증가하여 2000년에는 10만 ha를 넘어섰고, 2018년에는 80만ha의 규모를 보이고 있다(농사로, 2019). 시설농업단지의 동절기 난방을 위한 에너지원으로 화석연료와 전기열원을 사용하고 있고, 특히 강변의 경우 지하수를 난방 열원으로 사용가능해 수막재배를 이용한 대규모 시설단지가 발달함에 따라 지하수의 이용량이 증가하고, 2015년 농업용 지하수 이용량은 연간 20억 톤에 이른다(GIMS, 2019). 난방이 필요한 동절기에 수막용수를 위한 지하수 이용량이 급증하여 계절적인 수위변화를 보이며, 특히 강변의 대규모 시설농업단지의 지하수의 부족현상이 빈번히 발생하는 실정이다(송성호, 2017). 본 연구지역은 낙동강 하구댐 설치 전만조 시 해수의 유입으로 암반지하수의 심도가 증가할수록 EC가 증가하는 특성을 보이는 곳으로, 지하수의 이용량이 급증하는 동절기에 특히 급격히 증가하여 지하수의 안정적인 수질관리를 위해 염분변화의 관리가 필요한 지역이다. 지하수의 계절적인 변화를 위해 시설농업단지내에 지하수 관측정이 설치되어 관측되고 있으며 본 연구에서는 관측정의 2013년 1월~2019년 1월까지 지하수의 EC변화를 관측하였다. 지하수의 수위(GL.m), 온도, EC를 1시간 주기로 관측하여 계적적인 변화를 분석하였고, EC의 증가가 큰 곳은 심도별로 센서(다중심도)를 설치하여 염도의 변화를 관측하였다. 지하수성분의 지질학적 기원분석을 위한 양음이온 분석을 연 1회 실시하였다. 또한 관측정의 심도별 변화를 알기 위해 동일지역에 충적, 암반 관측정을 따로 설치하고 관측하여 지표수와 지하수의 심도별 영향의 차이를 분석하였다. 동일지역의 관측결과 평균 5m이하의 수위변화를 보이나, 5m 이상의 수위변동을 보이는 관측망은 15년 14개소 17년 19개소로 증가추세를 보이며, 이는 주로 밀집된 시설하우스 단지의 수막재배를 위한 겨울철 지하수 사용량 증가가 원인인 것으로 판단된다. 본 연구지역은 강변지역에 밀집된 시설하우스단지의 동절기 수막재배를 위한 지하수 과다 사용으로 수위급감 및 수량부족현상이 반복되고 있어, 예방과 대책강구를 위해 지표수의 함양과 지하수사용량의 상관관계 분석과 자료축적 및 추가연구를 위한 장기관측이 요구된다.

• The Journal of Engineering Geology
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• v.33 no.4
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• pp.725-736
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• 2023

The compliance of deep geological disposal facilities for high-level radioactive waste with safety objectives requires consideration of uncertainties owing to temporal changes in the disposal system. A comprehensive review and analysis of the characteristics of this evolution should be undertaken to identify the effects on multiple barriers and the biosphere. We analyzed the evolution of the buffer, backfill, plug, and closure regions during the early phase of the post-closure period as part of a long-term performance assessment for an operating license application for a deep geological repository in Finland. Degradation mechanisms generally expected in engineered barriers were considered, and long-term evolution features were examined for use in performance assessments. The importance of evolution features was classified into six categories based on the design of the Finnish case. Results are expected to be useful as a technical basis for performance and safety assessment in developing the Korean deep geological disposal system for high-level radioactive waste. However, for a more detailed review and evaluation of each feature, it is necessary to obtain data for the final disposal site and facility-specific design, and to assess its impact in advance.

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.751-758
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• 2019

This study tested various assumptions that simplified the configuration of the numerical model for unsaturated zone's contaminant transport to simulate the pathway to exposed point. This study investigated the contaminant migration through in the pollutant exposure pathway of vadoze zone for risk assessment of the contaminated site. For the purpose, generic scenarios as well as contaminant-based scenarios were simulated using the numerical code for transport of the contaminant in the pathway. The finite-difference one-dimensional transport with adsorption and biodegradation were considered, and it also assumed that the initial concentration was also depleted over time. The results of the generic-scenario show that as the groundwater infiltration rate decreases, the longer the path from the source to the groundwater level, the lower the concentration at the point of inflow into the groundwater level. In particular, in the case of high biodegradation rate and rapid depletion of pollutant sources, statistically outliers were found in the simulated results and generic scenarios was good at prediction.

• Journal of the Society of Disaster Information
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• v.14 no.2
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• pp.141-153
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• 2018

Purpose : The subject site selected in this study was a place that was prepared through the reclamation of foreshore completed in 1973. Since then, the site has been occupied by the industry of ship repair for over 30 years. Method : The results of a precise soil examination conducted in 2013 showed that the site was seriously contaminated with TPH over an area of $10,000m^2$ and GL(-)3.0m in depth, with an expanding coverage of contamination. Results : The soil contamination by refined petroleum products often results in adverse effects to human health and ecological systems, thus the contamination should be purified as soon as possible. Conclusion : Hydrogeological investigation can be employed to assess the groundwater movement and propagation of contamination to determine the potential agents or contaminants in the soil contaminated with high concentration TPH.

• Journal of Food Hygiene and Safety
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• v.23 no.3
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• pp.271-275
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• 2008

Choline is important an organic compound for normal membrane function, acetylcholine synthesis, lipid transport, and methyl metabolism. In biological tissues and foods, there are multiple choline compounds that contribute to choline content. There are so many analytical methods for choline determination, such as radioisotopic, high-performance liquid chromatography, and gas chromatography/mass spectrometry. However, these existing methods are expensive, unmanageable, and time-consuming. In this study, we modified enzymatic method, which is applicable for the determination of choline in milk and infant formulas, and applied to bovine serum and muscle. The calibration curves were linear with higher correlation coefficients than 0.994. Recoveries obtained by calibration curves from the spiked bovine serum and muscle samples varied between 70.6 and 85.2%. The method may be suitable for use as a routine method in the determination of choline for biological tissue and food samples.

• Journal of the Korean Society of Food Culture
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• v.21 no.2
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• pp.179-186
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• 2006

To investigate the production of yogurt added with desalted bamboo shoots, the component analysis was conducted. Desalted bamboo shoots contained 82.59 % of moisture, 4.56 % of protein, 0.52 % of lipid, 0.50 % of ash and 11.72 % of total dietary fiber. The main mineral elements were Ca, P, S, Na, Mg and K. Yogurt base fermented with 0.005 % ABT-5 starter inoculum at $40\;^{\circ}C$ for 13 hr. For the preparation of bamboo shoots yogurt, various sugaring bamboo shoots were added to the yogurt base. Results of sensory evaluation of the yogurt containing bamboo shoots indicated that color, odor, taste, flesh size, flesh amount, mouth feel, and overall acceptability of the 15 %(w/v) bamboo shoots dicing $(5{\times}5{\times}5\;mm)$ showed higher preference than others. When bamboo shoot yogurt was kept at $4\;^{\circ}C$ for 15 days, pH, titratable acidity, viable counts of lactic acid bacteria and Bifidobacterium bifidum of yogurt were not changed.

• Economic and Environmental Geology
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• v.44 no.2
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• pp.123-133
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• 2011

The lab scale experiments to investigate the geochemical reaction among supercritical $CO_2$-mineral-brine which occurs at $CO_2$ sequestration sites were performed. High pressurized cell system (l00 bar and $50^{\circ}C$) was designed to create supercritical $CO_2$ in the cell, simulating the sub-surface $CO_2$ storage site. From the high pressurized cell experiment, the surface changes of Ca-feldspar, amphibole (tremolite) and olivine, resulted from the supercritical $CO_2$-mineral-brine reaction, were observed and the dissolution of minerals into the brine was also investigated. The mineral slabs were polished and three locations on the surface were randomly selected for the image analysis of SPM and the surface roughness value (SRV) of those locations were calculated to quantify the change of mineral surface for 30 days. At a certain time interval, SPM images and SRVs of the same mineral surface were acquired. The secondary minerals precipitated on the mineral surfaces were also analyzed on SEM/EDS after the experiment. From the experiments, the average SRV of Ca-feldspar increased from 2.77 nm to 20.87 nm for 30 days, suggesting that the dissolution of Ca-feldspar occurs in active when the feldspars contact with supercritical $CO_2$ and brine. For the amphibole, the average SRV increased from 2.54 nm to 8.31 nm and for the olivine from 0.77 nm to 11.03 run. For the Ca-feldspar, $Ca^{2+}$, $Na^+$, $Fe^{2+}$, $Si^{4+}$, $K^+$ and $Mg^{2+}$ were dissolved in the highest order and $Si^{4+}$, $Ca^{2+}$, $Fe^{2+}$ and $Mg^{2+}$ for the amphibole. Fe (or Mg) - oxides were precipitated as the secondary minerals on the surfaces of amphibole and olivine after 30 days reaction. Results suggested that $Ca^{2+}$, $Fe^{2+}$ and $Mg^{2+}$ rich minerals would be significantly weathered when it contacts with the supercritical $CO_2$ and brine at $CO_2$ sequestration sites.