• Journal of Korean Society for Atmospheric Environment
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• v.20 no.3
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• pp.381-396
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• 2004

In order to understand the precipitation acidity and chemical composition of ion species in Iksan area as well as to know the difference of chemical characteristics in precipitation samples from the viewpoint of precipitation sampling method, precipitation samples were collected by wet-only automatic precipitation sampler and bulk manual precipitation sampler in Iksan, from March 2003 to August 2003. The mean pH of precipitation was 5.0. There was a little significant difference in the mean value of pH between automatic and manual sampler. However, pH values of some precipitation samples were lower in automatic sampler than in manual sampler, especially in case of precipitation samples with small rainfall for March 2003. The mean concentrations of each ions in precipitation were generally a little higher in precipitation samples collected by the manual sampler than in those collected by the automatic sampler because of accumulation of dry deposition on the surface of glass funnel installed at the manual sampler during the sampling period or no rainfall. Dominant species determining the acidity of precipitation, were N $H_4$$^{[-10]}$ and nss-C $a^{2+}$ for cations and nss-S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ for anions. The mean concentration of N $H_4$$^{+}$ and nss-C $a^{2+}$ were 31 $\mu$eq/L and 9 $\mu$eq/L for the automatic sampler and 40 ueq/L and 16 ueq/L for the manual sampler, respectively. In addition, nss-S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ were 27 $\mu$eq/L and 13 $\mu$eq/L for the automatic sampler and 32 $\mu$eq/L and 17 $\mu$eq/L for the manual sampler, respectively. Although the concentrations of the acidifying ions of nss-S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ were about 3 times higher than those for foreign pristine sites, precipitation acidity were estimated to be natural due to the neutralization reaction of the alkaline species of N $H_4$$^{+}$ and nss-C $a^{2+}$ with its higher concentrations. Considering the ratios of nss-S $O_4$$^{2-}$/N $O_4$$^{[-10]}$ nss-S $O_4$$^{2-}$, it was found that ammonium sulphate was dominant in Iksan precipitation. The major non-sea salt ions were maximum concentrations for March, but decreased with increasing of precipitation amount.on amount.

• Food Science and Preservation
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• v.15 no.3
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• pp.352-360
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• 2008

The extraction yield and storage stability of Codium fragile pigments extracted in acetone, ethanol or methanol were studied. Methanol was the most effective solvent for pigment extraction, providing an extraction yield of $25.0{\pm}2.10\;mg/g$ (my base). As shown by TLC and HPLC analysis, chlorophyll a(0.40 mg/g) and chlorophyll b(1.94 mg/g) were the major pigment components in dried Codium fragile. The total chlorophyll content of Codium fragile stored a 40C in light or dark conditions for 30 weeks remained at 23.2% and 58.4% respectively. The effect of metal ions ($Cu^{++}$, $Zn^{++}$, $Fe^{++}$ and $Mg^{++}$) on pigment stability was analyzed Among the four metal ions $Cu^{++}$ was the most effective stabilizer of Codium fragile pigments during storage, and $Zn^{++}$ ion was the second most effective. In the presence of 1 mM $Cu^{++}$, the total chlorophyll retained in Codium fragile stored at 40C in light or dark conditions was increased to 47.0% and 88.8% after 30 weeks storage, respectively. The optimum concentrations of $Zn^{++}$ and $Cu^{++}$ for pigment stabilization under dark conditions were 0.5 mM and 0.1 mM, respectively.

• Resources Recycling
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• v.24 no.4
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• pp.22-31
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• 2015

From results obtained by adjusting experimental variables based on the kinetic, the nucleation rate for formation of precipitated calcium carbonate (PCC) was investigated. Formation behavior of PCC was investigated for various concentrations of NaOH solution and $Na_2CO_3$ addition methods in the $Ca(OH)_2$ slurry. The range of nucleation rate was investigated for dissolution rates of major ion concentrations, $Ca^{2+}$ and $CO{_3}^{2-}$. In case of high concentration of major ions, vaterite and calcite were synthesized. The high nucleation rate was achieved for lower either $Ca^{2+}$ or $CO{_3}^{2-}$ ion concentration, calcite was mainly synthesized and when concentration of major ions was low, aragonite was synthesized. Furthermore, the formation of calcite was decreased with increasing concentration of NaOH. homogeneous aragonite could be obtained by addition 5 M NaOH. Therefore, in this study, specific shape of polymorphs could be prepared through controlling supersaturation.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.1
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• pp.87-97
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• 2004

NMHC (non-methane hydrocarbons) and fine particles such as P $M_{10}$ and P $M_{2.5}$ were measured at KIST (Korea Institute of Science and Technology) in Seoul for a month from the end of May. At the beginning of June, peak ozones exceeded 100ppb both near KIST and in Seoul while ozone and fine particles decreased from the middle of June due to frequent precipitation. Because the measurement site was close to trees on a hill, isoprene concentration went up to 4.1ppb with an average of 0.76ppb. Toluene was the highest all day long, but particularly high concentration in the afternoon implied a contribution of emission from solvent use as well as vehicle exhaust. Eighty-five percent of P $M_{10}$ was P $M_{2.5}$ on an average since major ions except sea salt, including nitrate, were present within P $M_{2.5}$. Daily variations of pollutants were generally similar except for NMHC. One of major differences in NMHC variation was maintenance of a relative high concentration in rainy day, showing that NMHC were not effectively scavenged by precipitation.ion.ion.

• Environmental Engineering Research
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• v.15 no.2
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• pp.93-98
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• 2010

This study aims to determine the chemical composition and seasonal variation of atmospheric acid deposition in order to identify possible sources contributing to precipitation. Sampling and analysis of 132 wet deposition samples were carried out from January to December 2008 at Mae Hia Research Center, Chiang Mai University, Chiang Mai Province. Total precipitation was 1,286.7 mm. Mean electro-conductivity and pH values were 0.94 mS/m and 6.27, respectively. Major cations ($Na^+$, ${NH_4}^+$, $K^+$, $Ca^{2+}$, and $Mg^{2+}$) and major anions ($HCOO^-$, $CH_3COO^-$, $Cl^-$, ${NO_3}^-$, and ${SO_4}^{2-}$) were determined by Ion Chromatography. The relative volume weight mean concentrations of anions, in descending order, were ${SO_4}^{2-}$ > ${NO_3}^-$ > $Cl^-$ > $CH_3COO^-$ > $HCOO^-$ and those of cations were $NH_4^+$ > $Ca^{2+}$ > $Mg^{2+}$ > $K^{+}$ > $Na^+$. Results of a principle component analysis highlighted the influence of various possible sources of ions such as agricultural activity, fuel combustion, marine sources, soil resuspension, and biomass burning.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.334-337
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• 2004

Groundwater chemistry in Namwon area, Korea, was investigated to understand the contribution of geochemical processes on groundwater chemistry. For this study, a total of 279 groundwater samples were collected from 93 wells distributed over the study area. Higher concentrations of major ions are generally encountered in the shallow alluvial wells, suggesting that these chemicals are originated from the surface contamination sources. Mass balance analysis based on reaction stoichiometry reveals that the water chemistry is regulated by three major chemical processes: weathering of silicate/ carbonate minerals, input of C1/SO$_4$ salts, and nitrate generating processes. The results show that mineral weathering is the most dominating factor regulating the groundwater chemistry. However, the groundwaters with the higher salt concentration indicate the larger mineral weathering effect, suggesting that some part of the mineral weathering effect is also associated with the anthropogenic activities such as limes applied to the cultivated lands, carbonates (CaCO$_3$) in the cement materials.

• Journal of Korean Society for Atmospheric Environment
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• v.8 no.3
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• pp.155-161
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• 1992

A simple, fast yet sensitive method is described for the determination of fifty elements in coal by inductively coupled plasma mass spectrometry. The method involves complete dissolution of coal with mixed acid $(HNO_3, HF, HClO_4)$ in hish pressure Teflon bomb and subsequent inductively coupled plasma mass spectrometric(ICP-MS) measurement. The accuracy of the method, being evaluated by the analysis of NIST SRMs (1632a, 1632b) is better than 20% RSD for most elements. The limits of detection defined by two times $\sigma$ (standard deviation of operational blank) are in order of sub-ppm to ppm, which are low enough to quantitate most elements. However, the determiantions for few elements such as V, As, Se are severely interfered by molecular ions such that their accurate determiantions are not possible. Analytical results for twentyon coals from eight countries including six ones world major coal producing, Korea, Japan, China, I.C.S., U.S.A., Canada, Australia, and South Africa are presented. While the results for major elements agree well with the existing ones, those for a few trace elements disagree considerably. The existing values are considerably higher. It is not possible to judge which are more accurate. However, the exisisting values are more likely to be errorous inasmuch as they are obtained without using high purity reagents and clean laboratory techniques.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.82.2-82.2
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• 2011

Major solar eruptive events, consisting of both a large flare and a near simultaneous fast coronal mass ejection (CME), are the most powerful explosions in the solar system, releasing $10^{32}-10^{33}$ ergs in ${\sim}10^{3-4}\;s$. They are also the most powerful and energetic particle accelerators, producing ions up to tens of GeV and electrons up to hundreds of MeV. For flares, the accelerated particles often contain up to ~50% of the total energy released, a remarkable efficiency that indicates the particle acceleration is intimately related to the energy release process. Similar transient energy release/particle acceleration processes appear to occur elsewhere in the universe, in stellar flares, magnetars, etc. Escaping solar energetic particles (SEPs) appear to be accelerated by the shock wave driven by the fast CME at altitudes of ~1 40 $R_s$, with an efficiency of ~10%, about what is required for supernova shock waves to produce galactic cosmic rays. Thus, large solar eruptive events are our most accessible laboratory for understanding the fundamental physics of transient energy release and particle acceleration in cosmic magnetized plasmas. They also produce the most extreme space weather - the escaping SEPs are a major radiation hazard for spacecraft and humans in space, the intense flare photon emissions disrupt GPS and communications on the Earth, while the fast CME restructures the interplanetary medium with severe effects on the magnetospheres and atmospheres of the Earth and other planets. Here I review present observations of large solar eruptive events, and future space and ground-based measurements needed to understand the fundamental processes involved.

• Food Science and Biotechnology
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• v.15 no.3
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• pp.424-430
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• 2006

Low molecular weight polyphenols were isolated from hot water extracts of radiata pine (Pinus radiata) bark using a Sephadex LH-20 column and characterized by $^1H$ and $^{13}C$ NMR, UV, FT-IR, and GC-MS analyses. Major compounds isolated and identified were protocatechuic acid, trans-taxifolin, and quercetin. Trans-taxifolin, an important intermediate in biosynthetic route of proanthocyanidin (PA), was isolated in large quantities and indicates that PA is a major component of radiata pine bark. Small amounts of polyphenols were identified by GC-MS analysis. The presence of p-hydroxybenzoic acid, vanillic acid, protocatechuic acid, cis- and trans-feruic acid, p-coumaric acid, trans-caffeic acid, (-)-epicatechin, (+)-catechin, trans- and cis-taxifolin, (+)-gallocatechin, and quercetin was confirmed by comparison of mass fragmentation patterns and retention times (RT) with authentic samples. In addition, the presence of astringenin, astringenin glycoside, trans- and cis-leucodelphinidin was strongly assumed from characteristic mass fragment ions due to their conjugated structure and retro Diels-Alder reaction, and also from biosynthetic route of PA. GC-MS analysis allowed us to detect small amounts of phenolic acids and flavonoids and eventually discriminate trans- and cis-configuration in the identified polyphenols.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.82.2-82.2
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• 2010

The development of bipolar plate having high efficiency and chemical properties has a major impact on fuel cell applications commercialization. Even though graphite bipolar plate has high electric conductivity and chemical resistance, it has demerits about mass production and brittle property for commercialization. Hence, metallic bipolar plate can be substitute for fuel cell bipolar plate. Although its inadequate corrosion behavior under PEMFC environment lead to a deterioration of membrane by dissolved metal ions, metallic bipolar plate for PEMFC is more suitable for automotive and residential power generation system because of its high mechanical strength, low gas permeability and applicability to mass production. Therefore, several types of coating has been applied to prevent corrosion and oxide film growth and to achieve more high durability. This work presents durability of coated metal bipolar plate for low temperature PEMFC which made for fuel cell vehicle. This results showed surface treatment increase long-term durability, even electric conductivity and corrosion resistance.