Bentonite, primarily composed of montmorillonite, plays a crucial role as one of the engineering barrier materials in a deep geological repository (DGR). The advantageous properties of montmorillonite, such as its swelling capacity, low permeability, and low thermal conductivity, make it a key component as a buffer material for isolating high-level radioactive waste from the surrounding natural environment. It has been known that the stability of montmorillonite is influenced by a wide range of pressure-temperature-composition (P-T-X) conditions relevant to the DGR environment. When considering potential geological events, of notable concerns are its interactions with groundwater or seawater at elevated temperatures, leading to safety hazards within the system. In this study, therefore, we investigated the hydration and dehydration reactions of Ca-montmorillonite with saline fluids such as NaCl and KCl solutions at elevated pressures and temperatures by conducting in-situ X-ray diffraction experiments using both a capillary sample heating cell and a resistive-heated diamond anvil cell. As a result, we observed different hydration states of montmorillonite depending on the chemical composition of fluids, i.e., tri-hydrated layers in NaCl and bi-hydrated layers in KCl solutions, respectively. Furthermore, we identified that montmorillonite undergoes distinct stepwise dehydration with increasing temperature, and the dehydration temperature of montmorillonite significantly increases with increasing water pressure. Consequently, this study would provide insights into the stability of hydrated montmorillonite in a seawater-dominated fluid environment and its implications for the long-term safety of the disposal system.

Bentonite is a potential buffer material of multi-barrier systems in high-level radioactive wastes repository. Montmorillonite, the main constituent of the bentonite, is 2:1 type aluminosilicate clay mineral with high swelling capacity and low permeability. Montmorillonite alteration under alkaline and saline conditions may affect the physico-chemical properties of the bentonite buffer. In this study, montmorillonite alteration by interaction with synthetic alkaline and saline solution and its retention capacity for cesium and iodide were investigated. The experiments were performed in three different batches (Milli-Q water, alkaline water, and saline water) doped with cesium and iodide for 7 days. Alteration characteristics and nuclide retention capacity of original- and reacted bentonite was analyzed by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscope (SEM), Nuclear Magnetic Resonance (NMR) and Cation Exchange Capacity (CEC) analysis. From the results, cesium retention occurred differently depending on the presence of competing ions such as K, Na, and Mg ions in synthetic solutions, while iodide was negligibly removed by bentonite. Montmorillonite alteration mainly occurred as cation exchange and zeolite minerals such as merlinoite and mordenite were new-formed during alkaline alteration of the montmorillonite. CEC value of reacted bentonite increased by formation of the zeolite minerals under alkaline conditions.

Bentonite, which mostly consists of montmorillonite, is considered as a suitable buffer material for disposal of high-level radioactive wastes in deep geological repository due to its high swelling capacity, low permeability, and strong retention capacity of radionuclide migration. Alkaline and saline solutions originated from degradation of cementitious material and seawater intrusion, respectively, may cause the changes in mineralogical and chemical properties of montmorillonite with various processes such as cation exchange within the interlayer, dissolution of montmorillonite, and precipitation of second minerals. In this study, montmorillonite alteration under alkaline and saline environments and its influences on retention of cesium and iodide by bentonite buffer were investigated. The reactions of bentonite (Bentonil-WRK) with alkaline solutions (0.1 M KOH and NaOH) and simulated saline solution were performed for 7 days in batch experiments at 25°C. After the experiments, reacted bentonite samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Short Wavelength Infrared (SWIR) spectrometry. The concentrations of cesium and iodide dissolved in the solutions were analyzed using an inductively coupled plasma mass spectrometer (ICP–MS). The XRD patterns showed significant decrease in the interlayer space of montmorillonite after the reaction with alkaline solution due to cation exchange and change in hydration status at the interlayer. The retention of cesium and iodide in alkaline and saline solutions were affected by montmorillonite alteration and ion competition. Therefore, the montmorillonite alteration affecting the nuclide retention capacity and long-term stability of bentonite buffer should be considered in the safety assessment of long-term geological disposal performance.

Chlor-alkali (CA) membranes as key materials to generate chlorine gas and sodium hydroxide are composed of sulfonic acid layer (S-layer) and carboxylic acid layer (C-layer) to provide fast sodium ion transport and slow hydroxide ion diffusion, respectively. Aciplex F, a representative CA membrane is made in a double layer form via thermal adhesion of both layers after each single layer film is independently fabricated. Unfortunately, the membrane fabrication induces delamination particularly in their interface as a result of hydroxide ion diffusion occurring during CA operation, leading to rapid increase in electrochemical overpotential. In this study, selective chemical conversion technique was developed to solve the delamination issue. Their effectiveness was proved by applying the same concept to a wide range of PFSA membrane.

Saline water electrolysis is an electrochemical process to produce valued chemicals by applying electric power. Perfluorinated sulfonic acid (PFSA) ionomers have been used as polymer electrolyte membrane (PEM) materials owing to their high sodium ion selectivity and barrier properties. However, sulfonic acid groups in PFSA ionomers are chemically decomposed under a basic catholyte condition, which makes the PEM materials lose their ionic selectivity and Faraday efficiency. In this study, double layered membranes were prepared by anchoring cross-linked hydrocarbon ionomers, as a protection layer to catholyte atmosphere, into the water channels, particularly, located at around the surface of a PFSA membrane. Here, each monomer results in the identical chemical architecture and different free volume content when polymerized.

Saline water electrolysis is a representative electrochemical conversion to produce chlorine gas and sodium hydroxide as major products by applying electric power. Perfluorinated sulfonic acid (PFSA) ionomers have been usually used as polymer electrolyte membrane materials owing to high sodium ion selectivity and strong resistance to acidic compounds (e.g., Cl2, HCl and so on) produced in anode. However, PFSA ionomers have been suffering from chemical degradation occurring when exposed under harsh basic condition in cathode. In this study, double layered chlor-alkali membranes were prepared by anchoring crosslinked hydrocarbon ionomer via radical polymerization technique in water channels located in a surface layer of PFSA ionomer membranes and electrochemically evaluated.

Riboswitches are structured RNA motifs that can directly bind specific metabolites. The binding of metabolites further regulates downstream metabolism eliminating the need for any regulatory proteins. We searched for novel bacterial vitamin B1 binding riboswitches in the metagenome of sun-dried saline soil. Soil microbial metagenomes were studied using NGS analysis. A total of approximately 50 Gb of the sequence data was obtained by Hi-seq and 454 GS FLX sequencing, and these sequences were subjected to riboswitch search. Hi-seq generated 614 contigs showing similarity to riboswitches, while 454-based sequencing generated 383 similar contigs. We matched whole metagenome contigs to local BLAST databases constructed using 91 previously known bacterial vitamin B1 thiamine pyrophosphate (TPP)-box motifs, and 11 SAM S-box motifs. Repetitive BLAST comparisons to local BLAST databases with nucleotide sequences from NGS identified 14 novel TPP-box motifs, and 7 S-box motifs respectively from the metagenome contigs. Further, RNA secondary structure analysis with public databases Rfam, and RibEx using these 21 riboswitch candidates revealed one contig, D8PYI to possess the most probable TPP-box structure. We constructed intragenic synthetic riboswitches to investigate whether the TPP-box motif region in D8PYI could harness gene expression in the presence of TPP. Construction of biosensors containing 100~400 bp fragments of D8PYI contigs, and in vivo imaging using the biosensors displayed TPP-specific changes in the expression of a green fluorescence protein reporter. In this regard, the adaptation of in silico riboswitch screening from environmental metagenomes could provide biosensors for detection of specific metabolites.

Soluble salts are dominant form at reclaimed tidal saline soil, which can be improved by leaching with excessive irrigation water. The objective of this study was to evaluate the effect of irrigation on soil salinity and corn (Zea mays) growth at reclaimed tidal saline soil. A field experiment was conducted at Saemangeum reclaimed tidal land in Korea, during two successive growing seasons between 2013 and 2014. During the growing season, three different irrigation practices were applied as following; (1) irrigation at −35 kPa, (2) irrigation at −50 kPa, and (3) no-irrigation. Soil salinity was significantly decreased with increasing irrigation rates. Soluble cations were statistically decreased with irrigation; especially the depression of soluble Na was greater than other cations. Corn growth was significant with irrigation practice and the length of stem, panicle number, and stem thickness was statistically greater compared to the control. Although the germination rate was more than 95% in all treatment, withering rate was great in both growing seasons, which was significantly decreased with irrigation practice. Our results indicated that salt control is critical at reclaimed tidal saline soil and irrigation practice based on soil potential could be one of the best management options to alleviate salt damages for stable crop production at reclaimed tidal saline soil.

염수전기분해(saline water electrolysis) 또는 클로로-알칼리 막공정(chlor-alkali membrane process)은 양이온교환 막과 전극으로 구성되는 전해셀에 전기를 가하여, 고순도(> 99%)의 고부가가치 화합물(예 : 염소, 수소, 수산화나트륨)을 직 접 제조하는 화학공정이다. 염수전기분해의 경제성은 동일한 양의 화합물을 생산하기 위해 투여되는 에너지 소비량을 저감 시킴으로 달성될 수 있다. 이러한 이슈는 전해질이나 전극의 고유 저항을 줄이거나, 전해질과 전극 사이의 계면 저항을 감소 시킴으로 달성시킬 수 있다. 본 연구에서는 전자빔 동시조사법을 사용하여, 높은 화학적 안정성을 지닌 탄화수소계 술폰산 이 오노머 막의 표면에 높은 이온선택성을 갖는 고분자를 접목 시키는 시도가 이루어졌다. 이를 통해, 고분자 전해질 막의 이온 전도성을 보완함과 동시에, 전극과의 계면 저항을 감소시켜, 전기화학적 효율 향상이 이루어짐을 관찰하였다.

Irrigation with saline water of rivers and groundwater reservoir into paddy field cause decreases rice production depending on water salinity. The purpose of this research was to determine the critical concentration of water salinity for provision of a basic information on the stable rice production in west costal area of Honam region. A greenhouse experiment was conducted at the 13 levels of saline water [0.01(control) 0.03, 0.05, 0.08, 0.10, 0.13, 0.15, 0.20, 0.25, 0.30, 0.50, 0.70, 1.00%] in transplanted rice using c.v. Cheongho and tolerance to different water salinities was evaluated at three growth stages of the rice plant such as [(35 DAT:Tillering), (81 DAT:Heading), and (106 DAT:Ripening)], respectively. Increasing water salinity significantly decreased grain yield and the higher in salinity the severe effect on yield reduction. The growth responses to water salinity varied at different growth stages of rice. At 35 DAT, increased water salinity decreased plant height and number of tillers significantly. Higher water salinity delayed the days to heading by 2 days (0.05%), 4 days (0.08%) and 7 days (0.1%). The critical water salinity at 35 DAT was below 0.08%. At 81 DAT, Cheongho survived at 0.10 and 0.08% salinity, respectively. However, at water salinity levels above 0.10%, the yield components such as number of panicles and number of spikelet decreased drastically. Thus, it was suggested that the critical water salinity at the mid-stage (tillering~heading, 81 DAT) was 0.05%, At 106 DAT, based on yield index that gives above 50% grain yield, the 0.05% salinity showed the lowest 61.1% grain yield of 19.2 g/plant as compared with the highest grain yield of 31.4 g/plant at 0.01% (control).

고염도 용액에서 sodium alginate 파울링을 가압식 전량여과 조건에서 관찰하였다. NaCl 및 CaCl2를 이용하여 이온 강도를 0.6 M로 제조한 용액에 sodium alginate를 2, 20 그리고 50 mg/L 투여한 후 공극크기 0.1 μm의 친수 성 PVDF 멤브레인을 통해 0.2 bar의 정압 조건에서 여과하였다. Na 혹은 Ca에 의한 이온강도가 높은 경우 파울링은 감소하였으나, Na와 Ca가 모두 존재하는 경우 여과 초기 파울링이 급격히 증가하는 경향을 나타내으며, 이온 강도가 높 은 경우 sodium alginate 농도에 따른 파울링속도에는 큰 차이가 없었다.

동해 영덕 연안의 저염수를 보기 위하여 지난 2010년 격월별(2월 23일, 4월 6일, 6월 8일, 8월 19일, 10월 6일, 12월 20일)로 20개의 정점에서 CTD 관측을 수행하였다. 혼합층은 여름에 약 10 m 깊이로 얕았으며, 겨울에 약 20 m 깊이에서부터 저층까지 혼합층을 나타내었다. 연중 5℃ 이하의 찬 물이 수온 약층 이심을 점하고 있었다. 염분 약층은 8월에는 깊이 20 m에, 10월에는 깊이 40 m에 분포하였으며 연중 가장 뚜렷하였다. 뚜렷한 저염수는 10월에 깊이 10 m에서 나타났는데, 10월에 강수량-증발량의 값이 음을 보였다, 이것은 10월에 영덕 연안에서 나타나는 저염수가 이류되어 온 것임을 시사하였다. 동해의 영덕 연안에서 나타나는 저염수는 동한 난류가 주요한 역할을 하는 것으로 보여진다.

서남부간척지 벼 담수표면 직파재배시 합리적인 질소기비시용시기와 시비량을 구명하고자 세사양토(문포통, 염농도0.1~0.2%)에서 동진 2호를 공시하여 시험한 결과를 요약하면다음과 같다. 4월 중순에 담수표면직파재배에서 파종전 기비시용시 적정입모수가 확보되었으나, 파종 후 10일, 20일 및 30일에 기비를 시용한 경우에는 적정입모수가 확보되지 않아 수량감소가컸다. 파종전 기비 시용 처리시 m2당 입모수는 163개이었으나파종 후 10, 20, 30일 기비시용 처리에서는 m2당 평균 98개로 파종전 기비시용에서 입모수가 많았다. 수량은 파종전 기비 시용 처리에서는 10a당 523 kg이었으나,파종후 10, 20, 30일 기비시용 처리에서는 10a당 평균433 kg로 파종전 기비 시용 처리에서 파종후 기비 시용처리보다 수량이 증수되었다. ha당 질소시비량 200 kg에서 쌀수량이 10a당 541 kg으로 처리간 수량이 가장 많았으나 질소시비량 170 kg/ha에서도 질소시비량 200 kg과 통계적 유의성이 인정되지 않았다. 따라서 서남부간척지에서 담수표면직파재배를 할 때의 기비시용 시기는 입모확보 및 쌀 수량과 염해 등을 고려해 볼 때파종전에 기비를 시용하는 방법이 파종후에 기비를 시용하는방법보다 좋을 것으로 보이며 또한 질소시비량을 표준시비200 kg/ha 보다 적은 170 kg/ha로 시용해도 적당할 것으로 생각된다.