• Journal of Korean Society for Atmospheric Environment
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• v.33 no.4
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• pp.411-423
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• 2017

The spacial potential source contribution function (PSCF) method was utilized by considering topography and height of back trajectories based on the measurement of organic typo matter (OM), $NO_3{^-}$, $SO{_4}^{2-}$, and $NH_4{^+}$ at the Baegryungdo Super Site ($37^{\circ}57^{\prime}N$, $124^{\circ}37^{\prime}E$, 135 m a.s.l. (above sea level)) for three selected periods (i.e., January~April, May~August, and September~December) in 2013. The PSCF were calculated on the contributions of trans-boundary transport to the hourly mean concentrations using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). The cluster analysis using back trajectories was performed to identify the major airflows to the sampling site. The upper atmosphere in the Tianjin area of China and the lower atmosphere in the western coast area of Korea can be the major source of trans-boundary pollution to the sampling site during January~April resulted from PSCF. The area in Lianyungang-city and Liaoning-sheng, China can be responsibile for the nitrogen related secondary compounds during May~August, and Shandong Peninsula in China is the major source area during September~December. In addition, relationships between the cluster analysis of back trajectories and PSCF were investigated for the statistically significance level for the source areas.

• Journal of the Mineralogical Society of Korea
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• v.17 no.1
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• pp.37-47
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• 2004

Sulfates such as alunite and schwertmannite formed under oxidation condition play a important role in geochemical processes taken place at waste dumps and a creek from Dalseong mine, Daegu. Water chemistry shows pH decreases from upstream toward downstream creek, mainly due to formation of schwertmannite that is the most abundant phase along the creek. The removal of Al from the creek is preferentially attributed to formation of Al-bearing minerals and Al-sulphates. Among them, alunite is the most important Al-sink phase that occurs at higher pH than $pK_1$, Al hydrolysis constant. With high saturation index, alunite formed at the creek has a spherical form, commonly associated with schwertmannite. Secondary minerals formed on the surface of altered or weathered surfaces of heavy metals from the wasted dump that underwent severe oxidation, where alunite has characteristic habits which are spheric, radiating, and botrytis-like aggregates. Natroalunite occurs in association with alunite, or as mixtures of both of them. Because the pH decreases with distance due to formation of schwertmannite, although total contents of dissolved ions slowly lessen at least in the AMD, it is expected that the minerals precipitated at the creek can be exposed to subsequent dissolution, which may induce possible environmental problems.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.1
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• pp.27-32
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• 2001

The effect of $V_2O_5$, a donor-type dopant on the degradation of quality factor of ($Zr_{0.8}, Sn_{0.2})TiO_4$was compared with Ta$_2$O$_{5}$ doped ($Zr_{0.8}, Sn_{0.2})TiO_4$ in terms of microstructure, electrical conductivity, and oxidation state of the dopant. It is well known that the addition of the donor type species such as $Ta_2O_5,Nb_2O_5, Sb_2O_5, WO_{3}$, increases the quality factor of ($Zr_{0.8}, Sn_{0.2})TiO_4$due to decrease the oxygen vacancy concentration. Unlike other dopants, however, the addition of $V_2O_5$ decreased the quality factor. The degradation of quality factor of ($Zr_{0.8}, Sn_{0.2})TiO_4$was resulted from the formation of grain boundary phase and $V_2O_5$rich fiber shaped secondary phase, and the increasing the oxygen vacancy concentration due to unstability of oxidation state of vanadium ions in ($Zr_{0.8}, Sn_{0.2})TiO_4$ceramic.c.

• Journal of Environmental Science International
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• v.27 no.4
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• pp.241-250
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• 2018

The objective of this study was to estimate air quality trends in the study area by surveying monthly and seasonal concentration trends. To do this, the mass concentration of $PM_{10}$ samples and the metals, ions, and total carbon in the $PM_{10}$ were analyzed. The mean concentration of $PM_{10}$ was $33.9{\mu}g/m^3$. The composition of $PM_{10}$ was 39.2% ionic species, 5.1% metallic species, and 26.6% carbonic species (EC and OC). Ionic species, especially sulfate, ammonium, and nitrate, were the most abundant in the $PM_{10}$ and had a high correlation coefficient with $PM_{10}$. Seasonal variation of $PM_{10}$ showed a similar pattern to those of ionic and metallic species. with high concentration during the winter and spring seasons. $PM_{10}$ showed high correlation with the ionic species $NO_3{^-}$ and $NH_4{^+}$. In addition, $NH_4{^+}$ was highly correlated with $SO{_4}^{2-}$ and $NO_3{^-}$. We obtained four factors through factor analysis and determined the pollution sources using the United States Environmental Protection Agency(U.S. EPA) pollution profile. The first factor accounted for 51.1% of $PM_{10}$ from complex sources, that is, soil, motor vehicles, and secondary particles: the second factor indicated marine sources; the third factor, industry-related sources; and the last factor, heating-related sources. However, the pollution profile used in this study may be somewhat different from the actual situation in Korea because it was from US EPA. Therefore, to more accurately estimate the pollutants present, it is necessary to create a pollution profile for Korea.

• Journal of Korean Society for Atmospheric Environment
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• v.25 no.4
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• pp.275-288
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• 2009

The Korean government strengthened the environmental polices to manage and enhance Metropolitan Area air quality, and also has enforced "Special Act on Seoul Metropolitan Air Quality Improvement (SASMAQI)" issued in Dec. 2004. Recently government expanded the Seoul Metropolitan Air Quality Management District (SMAQMD) to the outskirts satellite cities of Seoul area through the "Revised Law Draft of SASMAQI". The SMAQMD has been alloted the allowable emission loads to the local governments on the basis of the carrying $PM_{10}$ capacity. However, in order to establish the effective air quality control strategy for $PM_{10}$, it is necessary to understand the corresponding sources which have a potential to directly impact ambient $PM_{10}$ concentration. To deal with the situations, many receptor methodologies have been developed to identify the origins of pollutants and to determine the contributions of sources of interests. The objective of this study was to extensively identify $PM_{10}$ sources and to estimate their contributions at the metropolitan area. $PM_{10}$ samples were simultaneously collected at the 3 semi-industrialized local cities in the Seoul metropolitan area such as Hwasung-si, Paju-si, and Icheon-si sites from April 15 to May 31, 2007. The samples collected on the teflon membrane filter by one $PM_{10}$ cyclone sampler were analyzed for trace metals and soluble ions and samples on the quartz fiber filter by another sampler were analyzed for OC and EC. Source apportionment study was then performed by using a positive matrix factorization (PMF) receptor model. A total of 6 sources were identified and their contributions were estimated in each monitoring site. Contribution results on Hwasung, Paju, and Icheon sites were as follows: 33%, 27%, and 27% from soil source, 26%, 26%, and 21% from secondary aerosol source, 11%, 11%, and 12% from biomass burning, 12%, 6%, and 5% from sea salt, 7%, 15%, and 19% from industrial related source, and finally 11%, 15%, and 16% from mobile and oil complex source, respectively. This study provides information on the major sources affecting air quality in the receptor sites and thus it will help to manage the ambient air quality in the metropolitan area by establishing reasonable control strategies, especially for the anthropogenic emission sources.

• Journal of the Korean Chemical Society
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• v.50 no.4
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• pp.315-320
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• 2006

manganese oxides have been prepared by Chimie Douce redox reaction between permanganate and chalcogen element fine powder under acidic condition (pH = 1). According to powder X-ray diffraction analyses, the S- and Se-doped manganese oxides are crystallized with layered birnessite and tunnel-type -MnO2 structures, respectively. On the contrary, Te-doped compound was found to be X-ray amorphous. According to EDS analyses, these compounds contain chalcogen dopants with the ratio of chalcogen/manganese = 4-7%. We have investigated the chemical bonding character of these materials with X-ray absorption spectroscopic (XAS) analysis. Mn K-edge XAS results clearly demonstrated that the manganese ions are stabilized in octahedral symmetry with the mixed oxidation states of +3/+4. On the other hand, according to Se K- and Te L1-edge XAS results, selenium and tellurium elements have the high oxidation states of +6, which is surely due to the oxidation of neutral chalcogen element by the strong oxidant permanganate ion. Taking into account their crystal structures and Mn oxidation states, the obtained manganese oxides are expected to be applicable as electrode materials for lithium secondary batteries.

• Journal of the Korean Magnetics Society
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• v.19 no.3
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• pp.113-119
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• 2009

$^{57}Fe_xCu_{1-x}O$(x = 0.0, 0.02) powders were prepared by sol-gel method and their crystallographic and magnetic hyperfine properties have been studied using X-ray diffraction and $M{\ddot{o}}ssbauer$ spectroscopy (MS). The crystal structure of the samples is found to be monoclinic without any secondary phases and their lattice parameters increase with increasing annealing temperature ($T_A$), which is attributed to an increase in oxygen-vacancy content. MS measurements at room temperature indicate that $Fe^{3+}$ ions substitute $Cu^{2+}$ sites and ferromagnetic phase grow with increasing $T_A$. Magnetic hyperfine and quadrupole interactions of $^{57}Fe_{0.02}Cu_{0.98}O$ ($T_A=500^{\circ}C$) in the antiferromagnetic state at 17 K have been studied, yielding the following results: $H_{hf}=426.94\;kOe$, ${\Delta}E_Q=-3.67\;mm/s$, I.S.=0.32 mm/s, ${\theta}=65^{\circ}$, ${\phi}=0^{\circ}$, and ${\eta}=0.6$.

• Journal of Environmental Science International
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• v.27 no.7
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• pp.597-610
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• 2018

This study observed particulate matter ($PM_{2.5}$ and $PM_{10}$) in the downtown area of Jeju City, South Korea, to understand the chemical composition of particulates based on an analysis of the water-soluble ionic species contained in the particles. The mass fraction of the ionic species in the sampled $PM_{10}$ and $PM_{2.5}$ was 44.3% and 42.2%, respectively. In contrast, in Daegu City and Suwon City, the mass fraction of the ionic species in $PM_{2.5}$ was higher than that in $PM_{10}$. The chloride depletion percentage of $PM_{10}$ and $PM_{2.5}$ in Jeju City was higher than 61% and 66%, respectively. The contribution of sea-salt to the mass of $PM_{10}$ (5.9%) and $PM_{2.5}$ (2.6%) in Jeju City was similar to that in several coastal regions of South Korea. The mass ratio of $Cl^-$ to $Na^+$ in the downtown area of Jeju City was comparable to that in some coastal regions, such as the Gosan Area of Jeju Island, Deokjeok Island, and Taean City. The mass fraction of sea-salt in $PM_{10}$ and $PM_{2.5}$ was very low, and the concentration of sodium and chloride ions in $PM_{10}$ was not correlated with those in $PM_{2.5}$ ($R^2$ < 0.2), suggesting that the effects of sea-salt on the formation of particulate matter in Jeju City might be insignificant. The relationship between $NH_4{^+}$ and several anions such as $SO_4{^{2-}}$, $NO_3{^-}$, and $Cl^-$, as well as the relationship between the measurement and calculation of ammonium ion concentration, suggested that sea-salts may not react with $H_2SO_4$, and $(NH_4)_2SO_4$ may be a major secondary inorganic aerosol component of $PM_{2.5}$ and $PM_{10}$ in Jeju City.

• Journal of the Korean Electrochemical Society
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• v.18 no.4
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• pp.143-149
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• 2015

Carbon-coated $Li_2MnSiO_4$ powders as the active materials for the cathode were synthesized by planetary ball milling and solid-state reaction, and their phase formation behavior and charge-discharge properties were investigated. Calcination temperature and atmosphere were controlled in order to obtain the ${\beta}-Li_2MnSiO_4$ phase, which was active electrochemically, and the carbon-coated $Li_2MnSiO_4$ active material powders with near single phase ${\beta}-Li_2MnSiO_4$ could be fabricated. The particles of the synthesized powders were secondary particles composed of primary ones of about 100 nm size. The carbon incorporation was essential to enable the Li ions to be inserted and extracted from $Li_2MnSiO_4$ active materials, and the initial capacity of 192 mAh/g could be obtained in the $Li_2MnSiO_4$ active materials with 4.8 wt% of carbon.

• Bulletin of the Korean Chemical Society
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• v.21 no.11
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• pp.1125-1132
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• 2000

The pH effect of the precursor solution on the preparation of $LiCoO_2$ by a solution phase reaction containing malonic acid was carried out. Layered $LiCoO_2$ powders were obtained with the precursors prepared at the different pHs (4, 7, and 9) and heat-treated at $700^{\circ}C(LiCoO_2-700)$ or $850^{\circ}C(LiCoO_2-850)$ in air. pHs of the media for precursor synthesis affects the charge/discharge and electrochemical properties of the $LiCoO_2electrodes.$ Upon irrespective of pH of the precursor media, X-ray diffraction spectra recorded for $LiCoO_2-850$ powder showed higher peak intensity ratio of I(003)/I(104) than that of $LiCoO_2-700$, since the better crystallization of the former crystallized better. However, $LiCoO_2$ synthesized at pH 4 displayed an abnormal higher intensity ratio of I(003)/I(104) than those synthesized at pH 7 and 9. The surface morphology of the $LiCoO_2-850$ powders was rougher and more irregular than that of $LiCoO_2-700$ made from the precursor synthesized at pH 7 and 9. The $LiCoO_2electrodes$ prepared with the precursors synthesized at pH 7 and 9 showed a better electrochemical and charge/discharge characteristics. From the AC impedance spectroscopic experiments for the electrode made from the precursor prepared in pH 7, the chemical diffusivity of Li ions (DLi+) in $Li0.58CoO_2determined$ was 2.7 ${\times}$10-8 $cm^2s-1$. A cell composed of the $LiCoO_2-700$ cathode prepared in pH 7 with Lithium metal anode reveals an initial discharge specific capacity of 119.8 mAhg-1 at a current density of 10.0 mAg-1 between 3.5 V and 4.3 V. The full-cell composed with $LiCoO_2-700$ cathode prepared in pH 7 and the Mesocarbon Pitch-based Carbon Fiber (MPCF) anode separated by a Cellgard 2400 membrane showed a good cycleability. In addition, it was operated over 100 charge/discharge cycles and displayed an average reversible capacity of nearly 130 mAhg-1.