• Journal of Korean Society for Atmospheric Environment
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• v.10 no.E
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• pp.311-324
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• 1994

The quantitative knowledge of N $O_{\gamma}$ (＝N $O_{x}$ ＋HN $O_3$＋/PAN＋N $O_3$ ＋$N_2$ $O_{5}$ ＋HN $O_2$＋N $O_3$$^{-10}$ ＋organic nitrates＋......)distribution is essential in tropospheric chemistry, especially, especially that related to understanding the processes leading to ozone production. Ambient concentrations of NO, N $O_2$, HN $O_3$ and PAN as well as total N $O_{\gamma}$ were measured during June and early July 1992 at a rural site(Candor, NC), in the central Piedmont region of NC. The measurements of N $O_{\gamma}$ species were made in an effort to provide a comprehensive understanding of nitrogen chemistry and to investigate the total nitrogen budget at the site. N $O_{\gamma}$, N $O_2$, and NO showed diurnal variations with maxima in the morning. The maximum N $O_{\gamma}$ concentration reached was 14.5 ppbv, and the maximum concentrations of NO and N $O_2$ were 5.4 and 7.8 PPbv, respectively. The mean N $O_{\gamma}$ concentration as found to be 2.88$\pm$1.58 ppbv(n=743). The mean concentrations of NO and N $O_2$, were found to be 0.15 $\pm$ 0.29 ppbv(n＝785) and 1.31 $\pm$ 0.99 ppbv(n＝769). Products of photochemical oxidants, (N <$O_{\gamma}$-N $O_{x}$ ), such as HN $O_3$ and PAN, as well as ozone showed diurnal variation with maxima in the afternoon and minima at night The fractions of individual reactive nitrogen species to total N $O_{\gamma}$ were investigated and contrasted to the results from remote marine site and rural continental sites. N $O_{x}$ was the major species to total N $O_{\gamma}$(45%). NO concentrations appeared to be nearly constant whether the Prevailing winds were from continental areas or from oceanic areas. Linear regression of $O_3$ with (N $O_{\gamma}$- N $O_{x}$ )/N $O_{\gamma}$ (i.e. percent N $O_{x}$ converted to the photochemical products of N $O_{\gamma}$) yielded ( $O_3$) ＝25.8 〔 N $O_{\gamma}$-N $O_{x}$ 〕/(N $O_{\gamma}$) ＋27, ( $r^{2}$＝0.58). The regression intercept is interpreted as the ozone back ground (intercept=27ppbv) and the slope suggests that 8.6 molecules of ozone are formed per molecule of N $O_{x}$ oxidized products (when the average N $O_{\gamma}$ concentration, about 3 ppbv at the site, is used). The N $O_{x}$ N $O_{\gamma}$ ratio was used as an indicator of the chemical age of airmasses and the ratio showed strong positive correlations with HN $O_3$( $r^{2}$=0.58), PAN ( $r^{2}$=0.46) and $O_3$( $r^{2}$=0.62). Larger N $O_{\gamma}$ and N $O_{x}$ N $O_{\gamma}$ ratio were found when winds came from continental sides. It may suggest that synoptic meteorological conditions and transport of N $O_{x}$ are important in the distribution of N $O_{\gamma}$ and its relationship with photochemical oxidants at the site.

• Journal of Korean Society for Atmospheric Environment
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• v.25 no.2
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• pp.133-140
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• 2009

In order to examine the effects of micrometeorological and climatological influences on urban scale particulate air pollutants observed in Busan, power spectrum analysis was applied to the observed particulate matter with aerodynamic diameter ${\le}10{\mu}m$ ($PM_{10}$) for the period from 1991 to 2006. Power spectrum analysis has been employed to the daily mean $PM_{10}$ concentrations obtained at 13 sites to identify different scales of periodicities of $PM_{10}$ concentrations. The results show that, aside from the typical and well-known periodicities such as diurnal and annual variations caused by anthropogenic emission influences, another two significant peaks of power spectrum density were identified: 21 day and $3{\sim}4$ year of periodicities. Cospectrum analysis indicates that the intraseasonal 21 day periodicity are found to be negatively correlated with wind speed and surface pressure but shows consistently positive with relative humidity and temperature. This result implied that 21 day periodicity is presumably relevant to the secondary aerosol formation processes through the photochemical reaction that can be subsequently resulted from hygroscopic characteristics of aerosol formation. However, the interannual $3{\sim}4$ year of periodicity is found to have positive correlation with pressure, and negative with temperature and relative humidity, which is rather consistent with both characteristics of air mass during the Asian dust event and the occurrence frequency of Asian dust whose periodicities have been recorded inter-annually over the Korean peninsula.

• Bulletin of the Korean Chemical Society
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• v.23 no.9
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• pp.1218-1242
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• 2002

Photochemical reactions of aromatic carbonyl compounds with silyl ketene acetals have been explored. Irradiation of acetonitrile or benzene solutions containing aryl aldehydes or ketones in the presence of silyl ketene acetals is observed to promo te formation of ${\beta}-hydroxyester$, 2,2-dioxyoxetane and 3,3-dioxyoxetane products. The ratios of these photoproducts, which arise by competitive single electron transfer (SET) and classical Paterno-Buchi mechanistic pathways, is found to be dependent on the degree of methyl-substitution on the vinyl moieties of the ketene acetals in a manner which reflects expected alkyl substituent effects on the oxidation potentials of these electron rich donors. An analysis of the product distribution arising by irradiation of a solution containing butyrophenone (6) and the silyl ketene acetal 9, derived from methyl isobutyrate, provides an estimate of the rate constants for the competitive Norrish type Ⅱ, SET and Paterno-Buchi processes occuring. Finally, sequences involving silyl ketene acetal-aryl aldehyde or ketone photoaddition followed by 2,2-dioxyoxetane hydrolysis represent useful procedures for Claisen-condensation type, ${\beta}-hydroxyester$ synthesis.

• BMB Reports
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• v.35 no.4
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• pp.358-363
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• 2002

Chemical and photochemical processes during storage and preparation rapidly degrade retinol, the most active form of vitamin A. therefore, the efficacy of incorporation into liposomes in order to modulate the kinetics of retinol degradation was investigated. Retinol was readily incorporated into multilamellar liposomes that were prepared form soybean phosphatidylcholine; the extent of the incorporation was 98.14±0.93% at pH 9.0 at a ratio of 0.01 : 1 (wt:wt) retinol : phospholipid. It was only marginally lower at higher retinol concentrations. The pH of the hydration buffer had a small effect. The incorporation efficiency ranged from 99.25±0.47% at pH 3 to 97.45±1.13% at pH 11. The time course of the retinol degradation in the aqueous solution in liposomes was compared to that of free retinol and free retinol with α-tocopherol under a variety of conditions of pH(3, 7, and 11), temperature(4, 25, 37, and 50℃), and light exposure(dark, visible, and UV). The retinol that was incorporated into the liposomes degraded significantly slower than the free retinol or retinol with α-tocopherol at pH 7 and 11. At pH 3, where the free retinol degrades rapidly, the degradation kinetics were similar in liposomes and the presence of α-tocopherol. At pH 7.0 and 4℃ in the light, for example, free aqueous retinol was completely degraded within 2 days, while only 20% of the retinol in the liposomes were degraded after 8 days. In general, the protective effect of the liposome incorporation was greater at low temperatures, at neutral and high pH, and in the dark. The results suggest that protection is greater in the solid, gel phase than in the fluid liquid crystalline phase lipids. These results indicate that the incorporation into liposomes can extend the shelf-life of retinol under a variety of conditions of temperature, pH, and ambient light conditions.

• BMB Reports
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• v.33 no.3
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• pp.256-262
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• 2000

In this study the disassembly process of chlorophyII (ChI)protein complexes of a stay-green mutant (ore10 of Arabidopsis thaliana) was investigated during the dark incubation of detached leaves. During this dark-induced senescence (DIS), the Chi loss was delayed in the mutant, while the photochemical efficiency of photosystem II (PSII) or Fv/Fm was accelerated when compared with the wild type (WT) leaves. This indicates that the decrease in Fv/Fm is a separate process and not causally-linked to the degradation of Chi during DIS of Arabidopsis leaves. In the native green gel electrophoresis of the Chi-protein complexes, which was combined with an additional twodimensional SDS-PAGE analysis, the delayed senescence of this mutant was characterized by the appearance of an aggregate at 1 d or 2 d, as well as very stable light harvesting complex II (LHCII) trimers until 5 d after the start of DIS. The polypeptide composition of the aggregates varied during the whole DIS at 5 d. Dl protein appeared to be missing in the aggregates. This result supports the idea of a faster depletion of functional PSH in the mutants compared with WT, as suggested by the earlier reduction of Fv/Fm and the stable Chl a/b ratio in the mutants. At 5 d, the WT leaves also often showed aggregates, but the polypeptide composition was different from those of ore10. The results presented suggest that the formation of aggregates, or stable LHCII trimers in the stay-green mutants, is a way to structurally protect Chi-protein complexes from serious proteolytic degradation. Detailed disassembly processes of Chi-protein complexes in WT and ore10 mutants are discussed.

• Bulletin of the Korean Chemical Society
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• v.32 no.2
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• pp.583-589
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• 2011

Fluorescence correlation spectroscopy (FCS) is a sophisticated and an accurate analytical technique used to study the diffusion of molecules in a solution at the single-molecule level. FCS is strongly affected by many factors such as the stability of the excitation power, photochemical processes, mismatch between the refractive indices, and variations in the cover glass thickness. We have studied FCS near the surface of a cover glass by using rhodamine 123 as a fluorescent probe and have observed that the surface has a strong influence on the measurements. The temporal autocorrelation of FCS decays with two characteristic times when the confocal detection volume is positioned near the surface of the cover glass. As the position of the detection volume is moved away from the surface, the FCS autocorrelation becomes one-component decaying; the characteristic time of the decay is the same as the faster-decaying component in the FCS autocorrelation near the surface. This observation suggests that the faster component can be attributed to the free diffusion of the probe molecules in the solution, while the slow component has its origin from the interaction between the probe molecules and the surface. We have characterized the surface contribution to the FCS measurements near the surface by changing the position of the detection volume relative to the surface. The influence of the surface on the diffusion of the probe molecules was monitored by changing the chemical properties of the surface. The surface contribution to the temporal autocorrelation of the FCS strongly depends on the chemical nature of the surface. The hydrophobicity of the surface is a major factor determining the surface influence on the free diffusion of the probe molecules near the surface.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4258-4264
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• 2011

The total mercury concentration ($Hg_T$) of surface snow samples collected along a ~1500 km transect in east Queen Maud Land was determined using inductively coupled plasma sector field mass spectrometry to address the behavior of Hg on the Antarctic Plateau. Due to the volatile nature of mercury, measures were taken against Hg loss from standard solutions by choosing appropriate container material and stabilizing agents. Glass bottles with Teflon-lined caps were superior to Teflon and polyethylene containers in protecting against Hg loss, but addition of gold chloride ($AuCl_3$) or bromine chloride (BrCl) was necessary to ensure preservation of Hg. As Hg loss was also observed in snowmelt samples, our analysis may underestimate the actual amount of HgT in the snow. Even so, the measured HgT was still very low (< 0.4-10.8 pg $g^{-1}$, n = 44) without a signal of depositional enhancement accompanying photo-oxidation of atmospheric elemental mercury in austral midsummer. Moreover, the dynamic variation along the traverse implies spatial and temporal heterogeneity in its source processes.

• The Plant Pathology Journal
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• v.32 no.4
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• pp.300-310
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• 2016

Pathogen infection in plants induces complex responses ranging from gene expression to metabolic processes in infected plants. In spite of many studies on biotic stress-related changes in host plants, little is known about the metabolic and phenotypic responses of the host plants to Pseudomonas cichorii infection based on image-based analysis. To investigate alterations in tomato plants according to disease severity, we inoculated plants with different cell densities of P. cichorii using dipping and syringe infiltration methods. High-dose inocula (${\geq}10^6cfu/ml$) induced evident necrotic lesions within one day that corresponded to bacterial growth in the infected tissues. Among the chlorophyll fluorescence parameters analyzed, changes in quantum yield of PSII (${\Phi}PSII$) and non-photochemical quenching (NPQ) preceded the appearance of visible symptoms, but maximum quantum efficiency of PSII ($F_v/F_m$) was altered well after symptom development. Visible/near infrared and chlorophyll fluorescence hyperspectral images detected changes before symptom appearance at low-density inoculation. The results of this study indicate that the P. cichorii infection severity can be detected by chlorophyll fluorescence assay and hyperspectral images prior to the onset of visible symptoms, indicating the feasibility of early detection of diseases. However, to detect disease development by hyperspectral imaging, more detailed protocols and analyses are necessary. Taken together, change in chlorophyll fluorescence is a good parameter for early detection of P. cichorii infection in tomato plants. In addition, image-based visualization of infection severity before visual damage appearance will contribute to effective management of plant diseases.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.E1
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• pp.19-26
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• 2006

The decomposition of gaseous $CH_3CHO$ was investigated by metal loaded $TiO_2$ (pure $TiO_2,\;Pt/TiO_2,\;Pd/TiO_2,\;Mn/TiO_2\;and\;Ag/TiO_2$) with $UV/TiO_2$ process and $UV/TiO_2/O_3$ process at room temperature and atmospheric pressure. Metal loaded $TiO_2$ was prepared by photodeposition. Decomposition of $CH_3CHO$ was carried out in a flow-type photochemical reaction system using three 10W black light lamps ($300{\sim}400nm$) as a light source. The experimental results showed that the degradation rate of $CH_3CHO$ was increased with Pt and Ag on $TiO_2$ compared to pure $TiO_2$, but decreased with depositing Pd and Mn on pure $TiO_2$. The considerable increase in the degradation efficiency of the $CH_3CHO$ was found by a combination of photocatalysis and ozonation as compared to only by ozonation or photocatalysis. Loading of Pt on $TiO_2$ promoted conversion of gaseous ozone. The degradation rate of gaseous $CH_3CHO$ decreased with an increase of water vapor in the feed stream for the both $UV/TiO_2\;and\;UV/TiO_2/O_3$ processes. The pure $TiO_2$ was more affected by the water vapor than Pt loaded $TiO_2$.

• Journal of the Korean earth science society
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• v.21 no.3
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• pp.287-301
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• 2000

In order to investigate the factors and processes affecting the vertical distributions of ozone, we analyzed the ozone profile data measured using ozonesonde from 1995 to 1997 at Pohang city, Korea. In the course of our study, we analyzed temporal and spatial distribution characteristics of ozone at four different heights: surface (100m), troposphere (10km), lower stratosphere (20km), and middle stratosphere (30km). Despite its proximity to a local, but major, industrial complex known as Pohang Iron and Steel Co. (POSCO), the concentrations of surface ozone in the study area were comparable to those typically observed from rural and/or unpolluted area. In addition, the findings of relative enhancement of ozone at this height, especially between spring and summer may be accounted for by the prevalence of photochemical reactions during that period of year. The temporal distribution patterns for both 10 and 20km heights were quite compatible despite large differences in their altitudes with such consistency as spring maxima and summer minima. Explanations for these phenomena may be sought by the mixed effects of various processes including: ozone transport across two heights, photochemical reaction, the formation of inversion layer, and so on. However, the temporal distribution pattern for the middle stratosphere (30km) was rather comparable to that of the surface. We also evaluated total ozone concentration of the study area using Brewer spectrophotometer. The total ozone concentration data were compared with those derived by combining the data representing stratospheric layers via Umkehr method. The results of correlation analysis showed that total ozone is negatively correlated with cloud cover but not with such parameter as UV-B. Based on our study, we conclude that areal characteristics of Pohang which represents a typical coastal area may be quite important in explaining the distribution patterns of ozone not only from surface but also from upper atmosphere.