• 한국환경과학회지
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• 제28권4호
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• pp.413-422
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• 2019

The objective of this study was to estimate the trends of air quality in the study area by analyzing monthly and seasonal concentration trends obtained from sampled data. To this aim, the mass concentrations of $PM_{2.5}$ in the air were analyzed, as well as those of metals, ions, and total carbon within the $PM_{2.5}$. The mean concentration of $PM_{2.5}$ was $22.7{\mu}g/m^3$. The mass composition of $PM_{2.5}$ was as follows: 31.1% of ionic species, 2.2% of metallic species, and 26.7% of carbonic species (EC and OC). Ionic species, especially sulfate, ammonium, and nitrate, were the most abundant in the $PM_{2.5}$ and exhibited a high correlation coefficient with the mass concentration of $PM_{2.5}$. Seasonal variations of $PM_{2.5}$ showed a similar pattern to those of ionic and metallic species, with high concentrations during winter and spring. $PM_{2.5}$ also had a high correlation with the ionic species $NO_3{^-}$ and $NH_4{^+}$. In addition, $NH_4{^+}$ was highly correlated with $NO_3{^-}$. Through factor analysis, we identified four controlling factors, and determined the pollution sources using the United States Environmental Protection Agency(U.S. EPA) pollution profile. The first factor, accounting for 19.1% of $PM_{2.5}$ was attributed to motor vehicles and heating-related sources: the second factor indicated industry-related sources and secondary particles, and the other factors indicated soil, industry-related and marine sources. However, the pollution profile used in this study may be somewhat different from the actual situation in Korea, since it was obtained from US EPA. Therefore, to more accurately estimate the pollutants present in the air, a pollution profile for Korea should be produced.

• Asian Journal of Atmospheric Environment
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• 제11권2호
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• pp.79-95
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• 2017

A number of field studies have provided evidence that biomass burning is one of the major global sources of atmospheric particles. In this study, we have collected $PM_{2.5}$ emitted from biomass burning combusted at open burning and laboratory chamber situations. The open burning experiment was conducted with the cooperation of 9 farmers in Chiba Prefecture, Japan, while the chamber experiment was designed to evaluate the characteristics of chemical components among 14 different plant species. The analyzed categories were $PM_{2.5}$ mass concentration, organic carbon (OC), elemental carbon (EC), ionic components ($Na^+$, ${NH_4}^+$, $Ca^{2+}$, $Mg^{2+}$, $K^+$, $Cl^-$, ${NO_3}^-$ and ${SO_4}^{2-}$), water-soluble organic carbon (WSOC), water-insoluble inorganic carbon (WIOC), char-EC and soot-EC. OC was the dominant chemical component, accounting for the major fraction of primary $PM_{2.5}$ derived from biomass burning, followed by EC. Ionic components contributed a small portion of $PM_{2.5}$, as well as that of $K^+$. In some cases, $K^+$ is used as biomass burning tracer; however, the observations obtained in this study suggest that $K^+$ may not always be suitable as a tracer for biomass burning emissions. Also, the results of all the samples tested indicate relatively low values of char-EC compared to soot-EC. From our results, careful consideration should be given to the usage of $K^+$ and char-EC as indicators of biomass burning. The calculated ratios of WSOC/OC and WIOC/OC were 55.7% and 44.3% on average for all samples, which showed no large difference between them. The organic materials to OC ratio, which is often used for chemical mass closure model, was roughly estimated by two independent methods, resulting in a factor of 1.7 for biomass burning emissions.

• 한국세라믹학회지
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• 제32권12호
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• pp.1357-1368
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• 1995

Nasigels of composition Na0.75Zr2PSi2O12 and Na3Zr2PSi2O12 have been synthesized by the sol-gel technique using metal alkoxide precursors. The monolithic dry gels of Na0.75Zr2PSi2O12 with no crack have been prepared by the control of the shrinkage rte, but gels of Na3Zr2PSi2O12 were impossible to prepare without cracking. The gels treated up to 80$0^{\circ}C$ led to the formtion of glass but the glasses were converted to the crystalline phases at above this temperature. Crystaline phases precipitated from the Na0.75Zr2PSi2O12 glass were NASICON-like phase, Na2Si2O5, and free Zirconia. Phase that precipitated from the Na3Zr2PSi2O12 was only rhombohedral NASICON. For Na0.75Zr2PSi2O12 gels, framework of PO4 tetrahedra and SiO4(PO4) tetrahedra formed at low temperature but changed to that of SiO4 and SiO4(PO4) tetrahedras as it were crystallized. In the case of Na3Zr2PSi2O12 gel, framework of isolated PO4 and SiO4 tetrahedras formed at low temperature but changed to SiO4(PO4) tetrahedra framework which usually formed in the NASICON crystal after crystallization at high temperature. The gels treated up to 80$0^{\circ}C$ contained the residual water. The ionic conduction was attributed to the motion of proton and Na+ ion at low (up to 150~20$0^{\circ}C$) and high temperatures, respectively. As the temperature of heat treatment increased, ionic conductivity gradaully increased with the extent of precipitation of crystalline phase.

• 전기화학회지
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• 제23권4호
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• pp.81-89
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• 2020

전기화학 소자의 성능을 이해하는 데 있어서 전해질 내 이온 전도 기작을 이해하는 것은 매우 중요하다. 그러나 이론적/실험적 어려움으로 인해 아직 완벽한 전해질 내 이온 전도 기작 분석법은 정립되지 못했다. 대신 이온 전도 기작을 기술하기 위한 몇 가지 수학적 모델이 고안되었으며, 본 총설에서는 대표적인 사례인 아레니우스(Arrhenius) 모델과 Vogel-Tammann-Fulcher(VTF) 모델을 소개한다. 일반적으로 이 두 모델은 이온 전도도, 확산 계수, 점도와 같은 이동 특성(transport properties)의 온도 의존성을 기술하는 데 사용되며, 주어진 전해질에 적합한 수학적 모델은 이동 물성의 로그 값과 온도의 역수가 이루는 그래프의 선형성을 통해 판별할 수 있다. 현재 많은 전해질 연구는 다양한 조성과 온도 범위에서 두 모델 중에서 더 적합한 모델을 선정하고, 이를 통해 이온 전도 기작 분석과 활성화 에너지를 도출한다. 향후 전해질 이동 특성을 더욱 정확하게 기술할 수 있는 모델의 개발이 필요하다.

• 생물환경조절학회지
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• 제9권2호
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• pp.79-84
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• 2000

Thymus속의 common thyme과 thyme의 담액수경 재배시 배양액의 이온농도를 달리하여 두 종의 생육과 품질을 비교하였다. 배양액의 이온농도는 1.2, 2.4, 4.8 그리고 $7.2mS.cm^{-1}$로 하였다. 두 종 모두 $0.5(EC=1.2\;mS.cm^{-1})$배와 1배의 낮은 이온농도 처리에서 생육이 좋았다. Common thyme과 lemon thyme의 생육은 배양액내 이온농도가 높아질수록 건물율은 증가했으나 초장, 근장과 생체중은 감소하였다. 엽록소 함량은 lemon thyme에서 더 높았으나 비타민 C의 함량과 정유함량은 common thyme에서 더 높았다. 두 종간의 주요 정유 성분 차이를 보면, common thyme의 주성분은 thymo과 carvacrol이고, lemon thyme은 geranio과 ${\alpha}-citral$로 각각 정유 성분의 50~70%를 차지하고 있다. 이들의 각 주성분의 함량은 생육이 좋았던 0.5배에서 가장 많았다. 결과적으로 수경재배시 common thyme과 lemon thyme 모두 허브 배양액 0.5배액으로 재배시 우수한 품질의 작물을 생산할 수 있었다.

• 대기
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• 제29권4호
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• pp.403-416
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• 2019

Precipitation samples were collected at the GAW Stations in Anmyeon-do and Gosan for 10 years (2008-2017) to analyze pH, electrical conductivity and NH₄⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, SO₄^2-, NO₃^-, Cl^-, and F^- ions. From the analysis, the correlation between pH and rainfall, the composition of precipitation and comparison with other regions, and the results of neutralization characteristics by seasonal and pH were determined. In the comparison of ion balance and conductivity for the validation of analytical data, the correlation coefficients were within the range of 0.996~0.999, implying good linear relationship. The volume-weighted pH of the Anmyeon-do and Gosan areas were 4.7 and 4.9, respectively. The pH of the rainfall was affected by washout and rainout in both areas. The ionic strength of precipitation at Anmyeondo and Gosan were 0.42 ± 0.63 mM and 0.37 ± 0.75 mM, indicating about 27.6% and 35.3% of the total precipitation as per a pure precipitation criterion (10^-4 M), respectively. The composition ratio of ionic species were 44.7% and 57.5% for marine sources (Na⁺, Mg²⁺, Cl^-), 40.6% and 22.2% for the secondary inorganic components (NH₄⁺, nss-SO₄^2-, NO₃^-), and 5.6% and 4.0% for the soil source (nss-Ca²⁺), respectively. The neutralization factor of Anmyeon-do and Gosan were 0.43~0.65 and 0.34~0.48, and the neutralization factors of calcium carbonate were 0.15~0.34 and 0.25~0.30, respectively. Thus, both regions have the highest rate of neutralization caused by ammonia. As pH increased in Anmyeon-do and Gosan, change in calcium carbonate became greater than that in ammonia.

• 한국농공학회논문집
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• 제64권3호
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• pp.25-32
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• 2022

To understand the distribution characteristics of PM_2.5 concentration in the Saemangeum Reclamation Area and nearby areas, three points of the background area, the occurrence area, and the affected area were selected and samples were collected for each season. The chemical composition was determined. As a result of analyzing the chemical composition contained in PM_2.5, NO₃^- (7.2 ㎍/m³), SO₄^2- (4.3 ㎍/m³), NH₄+ (4.3 ㎍/m³), OC (2.5 ㎍/m³), Si (1.3 ㎍/m³) m³) and EC (0.5 ㎍/m³) seemed to be the main components, and NO₃-, SO₄^2-, NH₄⁺, which are components that form secondary particles, occupied a large proportion. The composition ratio of PM_2.5 was investigated in the order of ion component (56.8%) > Unknown (27.4%) > carbon component (11.8%) > heavy metal component (4.0%). During the PM_2.5 high concentration case days, the ionic component accounted for 90.7% during atmospheric stagnation cases, whereas the chemical composition ratio was in the order of ionic component (51.7%) > heavy metal component (41.5%) > carbon component (6.8%) during yellow dust cases. It was found that the characteristic of PM_2.5 in the Saemangeum reclaimed land and surrounding areas is mainly influenced by outside (domestic and overseas) throughout the year. Ion components accounted for the largest portion of PM_2.5 components in this area, but there were few sources of SOx and NOx emission in the Seamangeum area, which are precursors for secondary particle formation. Therefore, it is judged that most of these are generated and influenced as a secondary reaction in the atmosphere from the outside.

• 한국대기환경학회지
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• 제34권1호
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• pp.38-55
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• 2018

Hourly measurements of $PM_{2.5}$ mass, organic and elemental carbon (OC and EC), and water-soluble ionic species were made at the air quality intensive monitoring stations in Baengryeongdo (BR) and Seoul (SL) during the winter (December 01~31, 2013) and summer (July 10~23, 2014) periods, to investigate the increase of $PM_{2.5}$ and secondary ionic species and the reasons leading to their increase during the two seasons. During winter, $PM_{2.5}$ and its major chemical species concentrations were higher at SL than at BR. Contribution of organic mass to $PM_{2.5}$ was approximately 1.7 times higher at BR than at SL, but the $NO_3{^-}$ contribution was two times higher at SL. Total concentration of secondary ionic species ($SO{_4}^{2-}$, $NO_3{^-}$, and $NH_4{^+}$) at BR and SL sites accounted for 29.1 and 40.1% of $PM_{2.5}$, respectively. However, during summer, no significant difference in chemical composition of $PM_{2.5}$ was found between the two sites with the exception of $SO{_4}^{2-}$. Total concentration of the secondary ionic species constituted on average 43.9% of $PM_{2.5}$ at BR and 53.0% at SL. A noticeable difference in chemical composition between the two sites during summer was attributed to $SO{_4}^{2-}$, with approximately twofold concentration and 10% higher contribution in SL. Low wind speed and high relative humidity were important factors in secondary formation of water-soluble ionic species during winter at SL, resulting in $PM_{2.5}$ increase. While the secondary formation during summer was attributed to strong photochemical processes in daytime and high relative humidity in nighttime hours. The increase of $PM_{2.5}$ and its secondary ionic species during the winter haze pollution period at SL was mainly caused either by long-range transport (LTP) from the eastern Chinese regions, or by local pollution. However, the increased $SO{_4}^{2-}$ and $NO_3{^-}$ during summer at SL were mainly caused by LTP, photochemical processes in daytime hours, and heterogeneous processes in nighttime hours.

• Asian Journal of Atmospheric Environment
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• 제9권1호
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• pp.66-77
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• 2015

In order to survey the seasonal variation of the chemical composition of particulate matter of $2.5{\mu}m$ or less ($PM_{2.5}$), $PM_{2.5}$ was sampled from 8 February 2013 to 31 March 2014 in an industrial area of Chiba Prefecture, Japan. Chemical measurements of the sample included: ionic components ($Na^+$, $NH_4{^+}$, $Ca^{2+}$, $Mg^{2+}$, $K^+$, $Cl^-$, $NO_3{^-}$ and $SO_4{^{2-}}$), carbonaceous components - organic carbon (OC) and elemental carbon (EC), and water-soluble organic carbon (WSOC). Also, secondary organic carbon (SOC) was measured based using the EC tracer method, and char-EC and soot-EC were calculated from the analytical results. The data obtained were interpreted in terms of temporal variation. Of the overall mean value of $PM_{2.5}$ mass concentration obtained during the study period, ionic components, OC and EC accounted for 45.3%, 19.7%, and 8.0%, respectively. $NO_3{^-}$ showed a unique seasonal distribution pattern due to a dependence on temperature and absolute humidity. It was estimated that an approximate temperature of $14^{\circ}C$, and absolute humidity of $7g/m^3$ were critical for the reversible reaction of $NH_4NO_3(p){\leftrightharpoons}NH_3(g)+HNO_3(g)$. The amount of OC and EC contributing to the monthly $PM_{2.5}$ mass concentration was higher in autumn and winter compared to spring and summer. This result could be attributed to the impact of burning biomass, since WSOC and the ratio of char-EC/soot-EC showed a similar pattern during the corresponding period. From the comparison of monthly WSOC/OC values, a maximum ratio of 83% was obtained in August (summer). The WSOC and estimated SOC levels derived from the EC tracer method correlated (R=0.77) in summer. The high occurrence of WSOC during summer was mainly due to the formation of SOC by photochemical reactions. Through long-term observation of $PM_{2.5}$ chemical components, we established that the degree to which the above-mentioned factors influence $PM_{2.5}$ composition, fluctuates with seasonal changes.

• 한국대기환경학회지
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• 제24권5호
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• pp.501-511
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• 2008

The Objective of this study is to examine the characteristic of fine aerosol $(PM_{2.5})$ obtained at Ieodo Ocean Research Station, which lies between the eastern part of China and the south western part of Korea. The average mass concentration of $PM_{2.5}$ was $21.5{\pm}17.0{\mu}g/m^3$ during June $2004{\sim}June 2006$. The concentration was the highest in winter $(34.8{\mu}g/m^3)$ and lowest in summer $(16.5{\mu}g/m^3)$. Water soluble ions were measured for samples collected from December 2004 to September 2005. Among them, $SO_4^{2-}\;and\;NH_4^+$ were the most abundant species and accounted for 32.2% and 14.2% of the $PM_{2.5}$ mass, respectively. The mass fraction of $SO_4^{2-}$ was higher in winter (42%) than in spring (26%). Nitrate concentrations were much lower than those of sulfate due mainly to evaporation during sampling period. The cluster analysis of backward airmass trajectories showed that the high mass loadings $(26.9{\mu}g/m^3\;on\;average)$ were associated with air originating inland China. Also, the seasonal variation of $PM_{2.5}$ mass was well correlated with the frequency of westerly winds passing through the western part of China. During the ABC-EAREX2005 (March 2005), $PM_{2.5}$ mass and major ionic concentrations were higher at Ieodo, compared with $PM_{2.5}$ measurements at Gosan while they were similar in variation pattern. These results suggested that $PM_{2.5}$ mass and its ionic composition of Ieodo Ocean Research Station were greatly influenced by continental outflows from China.