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Geng, H.,Park, Y.,Hwang, H.,Kang, S.,Ro, C.-U. Copernicus GmbH 2009 Atmospheric Chemistry and Physics Vol.9 No.18
<P>Abstract. Low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA) shows powerful advantages for the characterization of ambient particulate matter in environmental and geological applications. By the application of the low-Z particle EPMA single particle analysis, an overall examination of 1800 coarse and fine particles (aerodynamic diameters: 2.5-10 μm and 1.0-2.5 μm, respectively) in six samples collected on 28 April-1 May 2006 in the marine boundary layer (MBL) of the Bohai Sea and Yellow Sea was conducted. Three samples (D1, D2, and D3) were collected along the Bohai Bay, Bohai Straits, and Yellow Sea near Korea during an Asian dust storm event while the other three samples (N3, N2, and N1) were collected on non-Asian dust (NAD) days. Based on X-ray spectral and secondary electron image data, 15 different types of particles were identified, in which soil-derived particles were encountered with the largest frequency, followed by (C, N, O)-rich droplets (likely the mixture of organic matter and NH4NO3), particles of marine origin, and carbonaceous, Fe-rich, fly ash, and (C, N, O, S)-rich droplet particles. Results show that during the Asian dust storm event relative abundances of the (C, N, O)-rich droplets and the nitrate-containing secondary soil-derived particles were markedly increased (on average by a factor of 4.5 and 2, respectively in PM2.5−10 fraction and by a factor of 1.9 and 1.5, respectively in PM1.0−2.5 fraction) in the MBL of the Bohai Sea and Yellow Sea, implying that Asian dust aerosols in springtime are an important carrier of gaseous inorganic nitrogen species, especially NOx (or HNO3) and NH3. </P>
Song, Y.-C.,Eom, H.-J.,Jung, H.-J.,Malek, M. A.,Kim, H. K.,Geng, H.,Ro, C.-U. Copernicus GmbH 2013 Atmospheric Chemistry and Physics Vol.13 No.6
<P>Abstract. In our previous works, it was demonstrated that the combined use of quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA), which is also known as low-Z particle EPMA, and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) imaging has great potential for a detailed characterization of individual aerosol particles. In this study, extensively chemically modified (aged) individual Asian dust particles collected during an Asian dust storm event on 11 November 2002 in Korea were characterized by the combined use of low-Z particle EPMA and ATR-FTIR imaging. Overall, 109 individual particles were classified into four particle types based on their morphology, elemental concentrations, and molecular species and/or functional groups of individual particles available from the two analytical techniques: Ca-containing (38%), NaNO3-containing (30%), silicate (22%), and miscellaneous particles (10%). Among the 41 Ca-containing particles, 10, 8, and 14 particles contained nitrate, sulfate, and both, respectively, whereas only two particles contained unreacted CaCO3. Airborne amorphous calcium carbonate (ACC) particles were observed in this Asian dust sample for the first time, where their IR peaks for the insufficient symmetric environment of CO32− ions of ACC were clearly differentiated from those of crystalline CaCO3. This paper also reports the first inland field observation of CaCl2 particles probably converted from CaCO3 through the reaction with HCl(g). HCl(g) was likely released from the reaction of sea salt with NOx/HNO3, as all 33 particles of marine origin contained NaNO3 (no genuine sea salt particle was encountered). Some silicate particles with minor amounts of calcium were observed to be mixed with nitrate, sulfate, and water. Among 24 silicate particles, 10 particles are mixed with water, the presence of which could facilitate atmospheric heterogeneous reactions of silicate particles including swelling minerals, such as montmorillonite and vermiculite, and nonswelling ones, such as feldspar and quartz. This paper provides detailed information on the physicochemical characteristics of these aged individual Asia dust particles through the combined use of the two single-particle analytical techniques, and using this analytical methodology it is clearly shown that internal mixing states of the aged particles are highly complicated. </P>
Neutron capture measurements and resonance parameters of dysprosium
Shin, S. G.,Kye, Y. U.,Namkung, W.,Cho, M. H.,Kang, Y. -R.,Lee, M. W.,Kim, G. N.,Ro, T. -I.,Danon, Y.,Williams, D.,Leinweber, G.,Block, R. C.,Barry, D. P.,Rapp, M. J. Springer-Verlag 2017 The european physical journal. A, Hadrons and nucl Vol.53 No.10
<P>Neutron capture yields of dysprosium isotopes (Dy-161, Dy-162, Dy-163, and Dy-164) were measured using the time-of-flight method with a 16 segment sodium iodide multiplicity detector. The measurements were made at the 25m flight station at the Gaerttner LINAC Center at Rensselaer Polytechnic Institute. Resonance parameters were obtained using the multilevel R-matrix Bayesian code SAMMY. The neutron capture data for four enriched dysprosium isotopes and one natural dysprosium sample were sequentially fitted. New resonances not listed in ENDF/B-VII. 1 were observed. There were 29 and 17 new resonances from Dy-161 and Dy-163 isotopes, respectively. Six resonances from Dy-161 isotope, two resonances from Dy-163, and four resonances from Dy-164 were not observed. The capture resonance integrals of each isotope were calculated with the resulting resonance parameters and those of ENDF/B-VII. 1 in the energy region from 0.5 eV to 20MeV and were compared to the capture resonance integrals with the resonance parameters from ENDF/B-VII. 1. A resonance integral value of the natural dysprosium calculated with present resonance parameters was 1405 +/- 3.5 barn. The value is similar to 0.3% higher than that obtained with the ENDF/B-VII. 1 parameters. The distributions of the present and ENDF/B-VII. 1 neutron widths were compared to a Porter-Thomas distribution. Neutron strength functions for Dy-161 and Dy-163 were calculated with the present resonance parameters and both values were in between the values of 'Atlas of Neutron Resonances' and ENDF/B-VII. 1. The present radiation width distributions of Dy-161 and Dy-163 were fitted with the chi(2) distribution by varying the degrees of freedom.</P>
Jung, H.J.,Kim, B.,Ryu, J.,Maskey, S.,Kim, J.C.,Sohn, J.,Ro, C.U. Pergamon Press ; Elsevier [distribution] 2010 Atmospheric environment Vol.44 No.19
Subway particle samples collected at four underground subway stations in Seoul, Korea were characterized by a single-particle analytical technique, low-Z particle electron probe X-ray microanalysis. To clearly identify indoor sources of subway particles, four sets of samples collected in tunnels, at platforms, near ticket offices, and outdoors were investigated. For the samples collected in tunnels, Fe-containing particles predominate, with relative abundances of 75-91% for the four stations. The amounts of Fe-containing particles decrease as the distance of sampling locations from the tunnel increases. In addition, samples collected at the platform in subway stations with platform screen doors (PSDs) that limit air-mixing between the platform and the tunnel showed marked decreases in relative abundances of Fe-containing particles, clearly indicating that Fe-containing subway particles are generated in the tunnel. PM<SUB>10</SUB> mass concentration levels are the highest in the tunnels, becoming lower as the distance of sampling locations from the tunnel increases. The extent of the decrease in PM<SUB>10</SUB> in stations with PSDs is also larger than that in stations without PSDs. The results clearly indicate that Fe-containing particles originating in tunnels predominate in the indoor microenvironment of subway stations, resulting in high indoor PM<SUB>10</SUB> levels, and that PSDs play a significant role in reducing Fe-containing particles at platforms and near ticket offices.