• Korean Journal of Soil Science and Fertilizer
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• v.43 no.1
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• pp.68-74
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• 2010

Since ${NO_3}^-$ is amore favorable electron acceptor than Fe, high ${NO_3}^-$ loads function as a redox buffer limiting the reduction of Fe and following release of ${PO_4}^{3-}$ in flooded paddy soil. The effect ${NO_3}^-$ loaded through irrigation water on Fe reduction and ${PO_4}^{3-}$ release in paddy soil was investigated. Pot experiment was conducted where irrigation water containing 5 or 10 mg N $L^{-1}$ of ${NO_3}^-$ was continuously applied at 1 cm $day^{-1}$, and changes of ${NO_3}^-$, $Fe^{2+}$ and ${PO_4}^{3-}$ concentrations in soil solution at 5 and 10 cm depths beneath the soil surface were monitored as a function of time. Irrigation of rice paddy with water containing 5 mg N $L^{-1}$ of ${NO_3}^-$ led to reduced release of $Fe^{2+}$ and prevented solubilization of P at 5 cm depth beneath the soil surface. And application of irrigation water containing 10 mg N $L^{-1}$ of ${NO_3}^-$ could further suppress Fe reduction and solubilization of P through 10 cm depth soil layer beneath the surface. These results suggest that the introduction of high level ${NO_3}^-$ with irrigation water in rice paddy can strongly limit Fe reduction and P solubilization in root zone soil layer in addition to the excessive supply of N to rice plants.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.4
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• pp.400-406
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• 1998

To investigate the effect of simulated acid rain on the change in soil chemical properties, simulated acid rain of different pH was applied to the three soils of different texture. Simulated acid rain of pH 4.0 and 6.0 did not greatly change the soil pH, while simulated acid rain of pH 2.0 decreased greatly the soil pH. Decrease in soil pH were in the order of sandy loam > loam > clay loam, while increase in exchangeable acidity was in the order of clay loam > loam > sandy loam. Amount of nutrients leached downward due to the penetration of simulated acid rain into the soil was in the order of Ca > K > Mg. Exchangeable Al was not detected when soil acidity dropped to pH 5 and exchangeable acidity increased within a range of CEC. A total 1200mm of simulated acid rain(pH 3.0) can load $12kg\;ha^{-1}$ of $H^+$ ion, $128kg\;ha^{-1}$ of sulfur, $56kg\;ha^{-1}$ of nitrogen. The acidity of simulated acid rain pH 3.0 can be neutralized by addition of $444kg\;ha^{-1}$ of slaked lime. The amount of leached bases were equivalent to 923, 1731 and $1608kg{\cdot}ha^{-1}$ in sandy loam, loam and clay loam soil respectively.

• Resources Recycling
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• v.27 no.6
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• pp.23-29
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• 2018

Recently rapid economic growth and technological development have led to an increase in the generation of waste electrical and electronic equipment (WEEE). As the amount of electric and electronic waste generated increases, the importance of processing waste printed circuit boards (PCB) is also increasing. Various studies have been conducted to recycle various valuable metals contained in a waste PCB in an environmentally friendly and economical manner. To get anode slime containing Ag and Au, Anode copper prepared from PCB scraps was used by means of electro-refining. Ag and Au recovery was conducted by leaching, direct reduction, and ion exchange method. In the case of silver, the anode slime was leached at 3 M $HNO_3$, 100 g/L, $70^{\circ}C$, and Ag was recovered by precipitation, alkali dissolution, and reduction method. In the case of gold, the nitrate leaching residues of the anode slime was leached at 25% aqua regia, 200 g/L, $70^{\circ}C$, and Au was recovered by pH adjustment, ion exchange resin adsorption, desorption and reduction method. The purity of the obtained Au and Ag were confirmed to be 99.99%.

• Journal of Sensor Science and Technology
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• v.30 no.3
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• pp.154-164
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• 2021

In this study, the IoT sensor technology required for improving the survival rate and high-density productivity of individual shrimp in smart shrimp farming (which involves the usage of recirculating aquaculture systems and biofloc technology) was analyzed. The principles and performances of domestic and overseas water quality monitoring IoT sensors were compared. Furthermore, the drawbacks of existing aquaculture monitoring technologies and the countermeasures for future aquaculture monitoring technologies were examined. In particular, for farming white-legged shrimp, an IoT sensor was employed to collect measurement indicators for managing the water quality environment in real-time, and the IoT sensor-based real-time monitoring technology was then analyzed for implementing the optimal farming environment. The results obtained from this study can potentially contribute to the realization of an autonomous farming platform that can improve the survival rate and productivity of shrimp, achieve feed reduction, improve the water quality environment, and save energy.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.213-213
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• 2020

최근 나타나는 지구온난화와 이상기후로 인해 가뭄과 홍수피해 같은 자연재해 발생 빈도가 높아졌고, 하천에서는 오염된 수질과 수생태계 복원 및 수변공간 조성, 수자원 관리 등의 목적으로 수질환경 개선사업이 진행되고 있다. 수질환경 측면에서 하천에서 발생하는 가장 큰 문제점으로는 녹조 즉, 남조류의 발생을 예로 들 수 있다. 본 연구에서는 최근 보 개방을 통하여 수질개선 효과가 나타나고 있는 금강을 대상으로 세종보, 공주보, 백제보 구간에 대하여 주요 수질인자에 대한 상관관계 분석을 수행하였다. 특히 남조류 세포수와 주요 하천 수질인자를 Pearson's correlation analysis를 이용하여 상관관계를 분석하였고, 보 위치별 남조류 세포수를 종속변수로 하고, 상관도가 높은 수질인자를 독립변수로 하는 다중회귀식을 도출하여 금강 내 주요 하천 수질인자의 농도에 따른 남조류 세포수 관계를 규명하고자 하였다. 분석기간은 2012년 1월부터 2019년 12월까지 보 건설 이후 시점으로 선정하였고, 월 평균 남조류 개체수가 조류경보제 발령기준 관심단계이상에 해당하는 금강수계의 3개 보에 대하여 남조류 세포수와 수질에 영향을 끼치는 인자인 강수량, (수온)W·T, (수소이온농도)pH, (용존산소)DO, (생물화학적산소요구량)BOD, (화학적산소요구량)COD, (부유물질량)SS, (총질소)TN, (총인)TP, (클로로필-a)Chl-a, (전기전도도)EC, (질산성질소)NO₃-N, (암모니아성 질소)NH₃-N, (인산염 인)PO₄-P, (용존총질소)DTN, (용존총인)DTP, (총유기탄소)TOC 와의 상관관계를 분석하였다. 분석 결과 측정 지점별 남조류 세포수와 상관관계가 있는 인자는 서로 상이했지만 (수온)W·T과 pH의 경우 모든 지점에서 남조류 세포수와 양의 상관관계가 나타났다. 세종보는 W·T(0.383, P<0.01), pH(0.391, P<0.05)의 양의 상관계수를 나타냈고, 공주보에서는 (수온)W·T(0.436, P<0.05), pH(0.412, P<0.05)의 양의 상관관계를 나타냈다. 백제보에서는 (수온)W·T(0.415, P<0.01), pH(0.221, P<0.01)의 양의 상관성을 나타냈다. 남조류 세포수와 수질인자 간의 상관관계 분석에 따라 통계적으로 유의한 인자 중 (수온)W·T과 pH에 영향을 받는 영양염류와 퇴적물에 대한 후속 연구가 필요할 것으로 사료되며, 연구를 통해 제시된 남조류 세포수 다중회귀식은 주요 수질인자 농도에 따라 발생 가능한 남조류세포수를 예측하여 금강의 수질 관리에 활용될 수 있을 것으로 기대된다.

• Analytical Science and Technology
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• v.22 no.2
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• pp.186-190
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• 2009

The oxidation studies of a sulfur to a sulfate ion by various oxyhalide oxidants in organic (thiourea, methionine) and inorganic (sulfate, thiophosphate) compounds were carried out in an acidic solution. The optimized result of the oxidation reaction was obtained when a bromate compound (${BrO_3}^-$) as an oxidant and a 3 M $HNO_3$ solvent were used. The chemical yield for the oxidation of the organic and inorganic sulfur compounds to a sulfate ion was monitored as 80% for thiophosphate, 87% for methionine, and 100% for thiourea and sulfate within 5% RSD. The oxidations of thiourea required at least 1.6 equivalents of the bromate in an acidic solution. In the case of the oxidation of methionine and thiophosphate, the oxidation yields were above 80% if the bromate was used at 20 times higher than that of the substrates. The sulfate ion was quantitatively measured by using a GPC counting of $^{35}S$ followed by precipitates of $BaSO_4$. A quenching correction curve for the $^{35}S$ counting was obtained to use the difference via the precipitate weight result.

• Analytical Science and Technology
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• v.20 no.4
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• pp.268-278
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• 2007

Nitrite which can be derived from water for dilution of metal working fluid can induce nitroso compounds which can be classified as carcinogen, if it co-exists with ethanolamines added for pH control in metal working fluid. The survey of nitrite, nitrate and nitroso-compounds level in 42 metal-working fluids collected from 17 factories was done by ion chromatography and gas chromatography with mass detector. Diluted metal working fluid showed higher level of nitrite and nitrate compared with raw fluid. Nitrite was detected in 11 (52%) samples among 21 diluted solution. Three (14%) samples showed over German recommendation level ($20{\mu}g/mL$).N-nitrosodiethanolamine(NDELA) was detected in 18 samples among 21 diluted solution. Seven (33%) samples showed over German recommendation level ($5{\mu}g/mL$). The concentration of NDELA was correlated with nitrite ion ($R^2=0.453$, n=19).

• The Journal of the Convergence on Culture Technology
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• v.9 no.5
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• pp.523-528
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• 2023

The applicability as a material to improve solar cell performance was reviewed by synthesizing a phosphor that emits red wavelengths by a liquid synthesis method using a metal salt aqueous solution and a polymer medium as a starting material. An aqueous solution was prepared using nitrate of metals such as Ca, Zn, Al, and Eu, and a precursor impregnated with starch, a natural polymer, was sintered to synthesize CaZnAlO:Eu phosphor powder. The surface structure and composition analysis of the synthesized CaZnAlO:Eu phosphor powder were analyzed by scanning electron microscope(SEM) and energy-dispersed X-ray spectroscopy(EDS). The crystal structure of CaZnAlO:Eu phosphor particles was analyzed by an X-ray diffraction analyzer (XRD). As a result of measuring the photoluminescence(PL) characteristics of the phosphor, it was confirmed that a red phosphor with a light emitting wavelength of 650-780nm was successfully synthesized. According to SEM and EDS analysis, the synthesized Ca₁₄Zn₆Al_9.93O₃₅:Eu³⁺_0.07 phosphor powder has a uniform particle size, and Eu ions used as an activator are present. The synthesized CZA:Eu³⁺ phosphor can be used as a material that can increase the light absorption efficiency of the solar cell by converting ultraviolet or visible light down conversion into a wavelength in the near-infrared region.

• Journal of Applied Biological Chemistry
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• v.66
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• pp.394-403
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• 2023

In the pursuit of sustainable and environmentally-friendly agricultural practices, we conducted an extensive study on the rhizosphere bacteria inhabiting soils that have been devoid of chemical fertilizers for an extended period exceeding 40 years. Through this investigation, we isolated a total of 80 species of plant growth-promoting rhizosphere bacteria and assessed their potential to enhance plant growth. Among these isolates, Burkholderia cepacia CD2 displayed remarkable plant growth-promoting activity, making it an optimal candidate for further analysis. Burkholderia cepacia CD2 exhibited a range of beneficial characteristics conducive to plant growth, including phosphate solubilization, siderophore production, denitrification, nitrate utilization, and urease activity. These attributes are well-known to positively influence the growth and development of plants. To validate the taxonomic classification of the strain, 16S rRNA gene sequencing confirmed its placement within the Burkholderia genus, providing further insights into its phylogenetic relationship. To delve deeper into the potential mechanisms underlying its plant growth-promoting properties, we sought to confirm the presence of specific genes associated with plant growth promotion in CD2. To achieve this, whole genome sequencing (WGS) was performed by Plasmidsaurus Inc. (USA) utilizing Oxford Nanopore technology (Abingdon, UK). The WGS analysis of the genome of CD2 revealed the existence of a subsystem function, which is thought to be a pivotal factor contributing to improved plant growth. Based on these findings, it can be concluded that Burkholderia cepacia CD2 has the potential to serve as a microbial fertilizer, offering a sustainable alternative to chemical fertilizers.

• Economic and Environmental Geology
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• v.36 no.2
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• pp.111-121
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• 2003

The objective of this study is to investigate the physical and chemical properties for environmental assessment of water system affected by acid mine drainage (AMD) from coal mining activities in the Youngwol, Jungseon and Pyungchang areas in Korea. During November 2000 to July 2002, 6 times of water samples were collected season-ally from acid mine drainage and nearby streams at 13 coal mines in the study area. The physical and chemical properties including pH, Eh, TDS, salinity, bicarbonates and DO were measured in the field. Eighteen cations includ-ing Al, Ca, Fe, Mg, Mn and Zn, and 6 anions including nitrates and sulfates were also analyzed by ICP-AES and If, respectively. Acid water from the Jungam coal mine has typical characteristics of AMD with very low pH(3∼4) and high TDS(1,000∼5,000 mg/1). Relatively high concentrations(mg/kg) of heavy meals, especially for Al(380), Fe(80), Mn(44) and Zn(8), were found in water samples from the Jungam coal mine area. Water samples from the Seojin, Sebang and Sungjin coal mines also contained over 50 mg/l of Al, >100 mg/1 of Fe and )10 mg/1 of Mn. In addition to anioins, over 1,000 mg/l of sulfate was found in several water samples. Seasonally, the concentrations of metals and sulfates varied; wet season samples were relatively higher in metals and sulfates than dry season samples. It is needed to establish the proper remediation and environmental monitoring of the AMD continuously.