Language：Japanese   Publishing type：Research paper (scientific journal)  

© 2020 by the authors. Mineral dust aerosols, which comprise multiple mineral species, are transported far from their source desert areas to the open ocean. After an Asian dust outflow event was observed over a marine boundary layer in the western North Pacific on February 29, 2012 on research vessel (R/V) Hakuho Maru, two dust particles of about 6 μm diameter were analyzed. First, they were sliced by using a focused ion beam (FIB). Their mineralogical structures and the elemental distribution of their cross-sections were subsequently analyzed with the use of transmission electron microscopy (TEM) and energy-dispersive X ray spectrometry (EDS). These analyses revealed that the dust particles consisted mainly of calcite and silica. Furthermore, Fe-containing domains were found in the submicrometer area surrounded by calcite and silica. A sulfur-containing domain that co-exists with calcium was found in a small domain near the particle surface, but no clear sign of atmospheric aging was found in most of the calcite domain. The inhomogeneous particle structure implies that the dissolution of iron and calcite in dust particles after ocean deposition depends on the physical structures of particles and their degree of aging according to atmospheric conditions during transport. Those factors must be adequately treated when estimating Asian dust effects on marine primary production.

DOI： 10.3390/atmos11010078

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Other Link： http://orcid.org/0000-0003-3321-2475

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Copernicus {GmbH}  

DOI： 10.5194/acp-18-9207-2018

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Number size distributions of aerosol particles with diameters of 10-500 nm in the marine boundary layer were observed continually onboard the R/V Hakuho Maru over the equatorial and subtropical North Pacific and South Pacific during December 2011 March 2012. Number-size distributions over each area were parameterized using a sum of up to three lognormal functions. Bi-modal size distributions with peak diameters at 30-80 nm (Aitken mode) and 100-200 nm (accumulation mode) were observed frequently. Larger peak diameters of Aitken and accumulation modes were observed over the eastern equator, where 5-day backward trajectories showed that the air masses had derived from high chlorophyll oceanic regions without precipitation. Smaller peak diameters and low concentrations were often observed over the North Pacific. The trajectories show that such air mass originated from oceanic regions with less chlorophyll, exhibiting high precipitation frequency. New particle formation (NPF) events have often been observed over the mid-latitude eastern South Pacific with a low condensation sink (CS) and some dimethyl sulfide, although none was observed over the equator, where CS was higher. The lesser CS condition at NPF events was mostly correlated with local precipitation or precipitation along the trajectories within I day. These results suggest that differences of the number size distribution and occasions of NPF events among sea areas most closely accord with precipitation along the trajectories. (C) 2016 The Authors. Published by Elsevier Ltd.

DOI： 10.1016/j.atmosenv.2016.07.055

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

A new polar nephelometer (PN) has been developed to measure simultaneously the scattering angular distributions from 11.7 degrees to 168.3 degrees for individual particles in planes parallel and perpendicular to the polarization of the incident laser beam. Each detection plane had 21 silicon photodiode detectors to detect scattered light at a rate of 100 Hz. Laboratory experiments to validate the performance of the instrument were conducted using nearly mono-disperse spherical particles (polystyrene latex [PSL] and nigrosine) and nonspherical particles (sodium chloride [NaCl] and soot). The observed scattering angular distributions for individual PSL particles were in good agreement with the results of simulations based on Mie theory. Complex refractive index values for nigrosine particles were determined by comparing the observed scattering angular distributions with the results of simulations. Clear differences between the measured scattering angular distributions and the results of simulations based on Mie theory assuming spherical particles were observed for NaCl particles (mobility diameters of 500 and 700 nm) and propane soot particles (mobility diameters of 300, 500, and 700 nm). These results are reasonably explained by theoretical predictions. We also conducted initial observations of ambient particles in Nagoya city, Japan. Scattering angular distributions for particles with a mobility diameter of 500 nm and an average effective density of 1.4 or 0.3 g/cm(3), which were selected with a combination of differential mobility analyzer and aerosol mass particle analyzer, were measured using the PN. As results, scattering angular distributions for nearly spherical inorganic and organic particles with an average effective density of around 1.4 g/cm(3) were found to be distinguishable from nonspherical particles with an average effective density of around 0.3 g/cm(3). This study has demonstrated that our PN has the potential to distinguish between spherical and nonspherical particles.
Copyright (c) 2016 American Association for Aerosol Research

DOI： 10.1080/02786826.2016.1155105

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：COPERNICUS GESELLSCHAFT MBH  

The coating of black carbon (BC) with inorganic salts and organic compounds can enhance the magnitude of light absorption by BC. To elucidate the enhancement of light absorption of aged BC particles and its relation to the mixing state and morphology of individual particles, we conducted observations of particles at an Asian outflow site in Noto Peninsula, Japan, in the spring of 2013. Absorption and scattering coefficients at 405, 532, and 781 nm and mass concentrations/mixing states of refractory BC in PM2.5 were measured using a three-wavelength photoacoustic soot spectrometer and a single-particle soot photometer (SP2), respectively, after passage through a thermodenuder (TD) maintained at 300 or 400 degrees C or a bypass line maintained at room temperature (25 degrees C). The average enhancement factor of BC light absorption due to coating was estimated by comparing absorption coefficients at 781 nm for particles that with and without passing through the TD at 300 degrees C and was found to be 1.22. The largest enhancements (> 1.30) were observed under high absorption coefficient periods when the air mass was long-range transported from urban areas in China. Aerosol samples were also analyzed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray analyzer. The morphological features and mixing states of soot-containing particles of four samples collected during the high absorption events were analyzed by comparing microphotographs before and after the evaporation of beam-sensitive materials by irradiation with a high-density electron beam. The majority of the soot in all samples was found as mixed particles with sulfate-containing spherules or as clusters of such spherules. For samples showing high enhancement (> 1.30) of BC light absorption, the TEM showed that the internally mixed soot-containing particles tended to have a more spherical shape and to be thickly coated. The SP2 measurements also suggested that the proportion of thickly coated soot was greater. Thus, the observed enhancement of BC light absorption was found to differ according to the mixing states and morphology of soot-containing particles. The enhancement of BC light absorption in our in situ measurements and its relation with individual features of soot-containing particles will be useful to evaluate direct radiative forcing in the downwind areas of large emission sources of BC.

DOI： 10.5194/acp-16-2525-2016

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE INC  

Sizes and compositions of atmospheric aerosol particles can be altered by in-cloud processing by absorption/adsorption of gaseous and particulate materials and drying of aerosol particles that were formerly activated as cloud condensation nuclei. To elucidate differences of aerosol particles before and after in-cloud processing, aerosols were observed along a slope of Mt. Fuji, japan (3776 m a.s.l.) during the summer in 2011 and 2012 using a portable laser particle counter (LPC) and an aerosol sampler. Aerosol samples for analyses of elemental compositions were obtained using a cascade impactor at top-of-cloud, in-cloud, and below-cloud altitudes. To investigate composition changes via in-cloud processing, individual particles (0.5-2 mu m diameter) of samples from five cases (days) collected at different altitudes under similar backward air mass trajectory conditions were analyzed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray analyzer. For most cases (four cases), most particles at all altitudes mainly comprised sea salts: mainly Na with some S and/or CL Of those, in two cases, sea-salt-containing particles with Cl were found in below-cloud samples, although sea-salt-containing particles in top-of-cloud samples did not contain Cl. This result suggests that Cl in the sea salt was displaced by other cloud components. In the other two cases, sea-salt-containing particles on samples at all altitudes were without CL However, molar ratios of S to Na (S/Na) of the sea-salt-containing particles of top-of-cloud samples were higher than those of below-cloud samples, suggesting that sulfuric acid or sulfate was added to sea-salt-containing particles after complete displacement of Cl by absorption of SO2 or coagulation with sulfate. The additional volume of sulfuric acid in clouds for the two cases was estimated using the observed S/Na values of sea-salt-containing particles. The estimation revealed that size changes by in-cloud processing from below-cloud to top-of-cloud altitudes were less than 6% for sizes of 0.5-2 mu m diameter. The obtained results will be useful to evaluate the aging effect and transition of aerosol particles through in-cloud processing. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.atmosres.2013.10.011

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Language：English   Publisher：日本大気電気学会  

There is an ionospheric potential between conductive solid-earth and ionosphere which reaches approximately 250 kV. The ionospheric potential is generated by the spherical shell capacitance of which is formed by positively charged ionosphere and negatively charged solid-earth. The capacitance is charged and discharged by the global thunderstorm activity and air-earth current in the fair weather, respectively. This large-scale electric circuit is termed a global electric circuit. Recently, it is pointed out that the variation of ionospheric potential is associated with global climate change, so that some of scientists started revisiting this traditional topic. In order to promote their resurvey, we show that a ground-based measurement of atmospheric electric field highly affected by atmospheric clouds, aerosols, and so on is still a useful tool to measure the variation of ionospheric potential through the simultaneous observations of ground-based atmospheric electric field, aerosols, and clouds on the R/V Hakuho Maru over the Pacific Ocean. In the period we obtained Carnegie curve, the observed AEF did not correlate to atmospheric aerosol concentration. The most plausible interpretation is that the observed variation of AEF reflected the variation of ionosphere potential.

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Language：Japanese   Publisher：Japan Association of Aerosol Science and Technology  

Iron (Fe) is an essential element for marine phytoplankton growth. Long-range transport of atmospheric aerosols from the continent and subsequent deposition is an important process to supply Fe to the ocean. The mixing states with water-soluble materials are the significant factor for the dry and wet depositions of aerosol particles. In this study, we focused on water-insoluble Fe-containing particles and clarified the mixing states with water-soluble materials. We collected aerosol particles on the R/V Hakuho Maru in the mid-latitude over the North Pacific Ocean. Collected particles were analyzed using a transmission electron microscopy with a water dialysis method and an energy-dispersive X-ray (EDX) analysis. Particles larger than 0.5 μm in diameter during a dust event and no dust events (maritime and continental sample) were analyzed. The number fractions of water-insoluble material containing particles to total analyzed particles were 10% (maritime), 20% (continental) and 30% (dust event), respectively. Most of water-insoluble materials were mixed with water-soluble materials. Based on EDX analyses of water-insoluble materials in analyzed 3 samples, water-insoluble Fe-containing particles were found with other mineral components (Si or Al) and the number fractions of Fe-containing particles to total analyzed particles were 2% (maritime), 2% (continental) and 8% (dust events), respectively.

DOI： 10.11203/jar.29.104

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Language：Japanese   Publisher：日本大気電気学会  

In order to observe atmospheric ions in the free troposphere, measurements of atmospheric positive ions in the critical mobility range 5.0 and 0.63 cm<sup>2</sup>/Vs were conducted at the summit of Mt. Fuji (35.36N, 138.73E, 3776 m a.s.l.) from Aug. 8 to 23, 2011. Positive atmospheric ions were found to have a clear diurnal variation, with minimum concentrations during nighttime and with maximum daytime, which is possibly linked to ions transportation by valley breeze. This variation is clearer when the observation station is out of clouds in planetary boundary layer. A strong anti-correlation was found between air ion concentrations and coagulation sink. Enhanced ion concentrations were found when air mass had been transported over the sea and coagulation sink value is low.

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1029/2010JD015565

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.4209/aaqr.2010.11.0101

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.atmosres.2010.10.021

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Association of Aerosol Science and Technology  

Volume fraction (<i>ε</i>) of water-soluble material in atmospheric aerosol particles is an important parameter related to hygroscopicity and activation processes to cloud particles. In order to estimate ε of individual coarse dust particles, a confocal scanning laser microscope was applied to direct measurement of volume difference of individual particles before and after water-dialysis using Nuclepore filters (nominal pore size: 0.05 µm) as a collection substrate of an aerosol impaction sampler. Individual particles of Arizona Test Dust (ATD) and reference Asian dusts (CJ-1 and CJ-2) were analyzed for , and their results were combined into 3 size ranges (2-3.4, 3.5-8.4, and 8.5-30 µm) and 2 size ranges (2-3.4 and 3.5-10 µm), respectively. These test dust particles showed various ε ranging from 18% (ATD) to 41% (CJ-1) on the average. More than 50% of the analyzed test dusts particles contained soluble fraction (<i>ε</i>>10%), except the ATD particles of size range 2-3.4 µm which are dominated by particles with insoluble components.<br>

DOI： 10.11203/jar.26.147

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Language：Japanese   Publisher：日本エアロゾル学会  

This study focused on modification effects of soot-containing particles by aging and in-cloud scavenging processes. Morphological features and mixing states with water-soluble materials of soot-containing particles collected at two observation sites were analyzed by a transmission electron microscopy (TEM) with extraction of water-soluble materials. To elucidate the aging effects after their transport from megacities, we obtained aerosol samples for continental outflow at Cape Hedo, Okinawa in March 2008. Most soot-containing particles (0.2-0.7 μm) were mixed with water-soluble materials. Some soot-containing particles were found as clustered particles in multiple small (ca. 0.3 μm) spheroids. They were attributed to coagulation of solid spheroidal particles. At Mt. Tateyama (2300 m a.s.l.) in June 2007, cloud interstitial particles were measured using fog (&gt;10 μm)-cut inlets. During fog condition under high precipitation (2-6 mm/hr), most of cloud interstitial particles (0.3-0.5 μm) were less- or non-hygroscopic particles. The results of TEM analysis suggested that most of the cloud interstitial particles were soot particles without water-soluble materials. These observation results suggested that morphological modification with coagulation process under high aerosol concentration and population change of the particles with in-cloud scavenging process are key processes controlling morphology and mixing states of soot-containing particles in the atmosphere. These changes of soot-containing particles must be considered when estimating direct radiation effect of aerosols from megacities and assessing climatic effects by long range transport of soot aerosols.&lt;br&gt;

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東京海洋大学「海鷹丸」の南極海研究航海において,大気エアロゾルの光学的厚さ(AOT)の観測を実施した.南極海インド洋セクターでの500 nmでのAOTは,0.02-0.12の範囲であった.南極大陸沿岸域でのAOTは比較的低く,0.02前後であった.40-60゜Sの海域では,0.1以上の値を示すことがあった.インド洋低中緯度帯でのAOTは,0.05-0.15の範囲であった.風速とAOTとに正の相関がみられたことから,南極海では光学的に海塩粒子が卓越し,風速がAOTに影響を及ぼしていると考えられる.AOTが高くなるにつれ,オングストローム指数は減少した.AOTの波長スペクトルにおいて,380 nmと870 nmのAOTはべき関数からずれる傾向がみられた.レイリーの光学的厚さの算出方法を比較したところ,ずれが大幅に改善される可能性が示された.今後,より観測精度を高めていくためには,機器定数の精度を把握するとともに,レイリーの光学的厚さの算出方法の見直しなどが必要である.Aerosol optical thickness (AOT) was measured during Antarctic research cruises of R V Umitaka-Maru. The measured AOTs at 500 nm in the Indian sector of the Antarctic Ocean ranged from 0.02 to 0.12. In Antarctic coastal waters, the AOTs were as low as around 0.05. On the other hand, the some AOTs were higher than 0.1 from 40゜S to 60゜S. In middle and low latitude regions of the Indian Ocean, the AOTs ranged from 0.05 to 0.15. The AOTs were correlated with wind speed. It is indicated that sea-salt particles, generated by wind, dominated optically and wind speed affected the AOT in the Antarctic Ocean. Angstro¨m exponent decreased with increasing AOT. In the AOT wavelength spectra, some AOTs in 380 nm and 870 nm tended to deviate from the power function. Comparing calculation methods of Rayleigh optical thickness suggested a possibility of reducing the deviations of these AOTs. In the future, accuracy check of the instrument constant and review of the calculation method of Rayleigh optical thickness are recommended to enhance the accuracy of maritime AOT measurement.

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Language：Japanese   Publishing type：Research paper (scientific journal)  

南極海における大気エアロゾル粒子の粒径分布やイオン成分濃度,先駆ガス濃度の時空間分布を調べるために,「白鳳丸」や「タンガロア」,「海鷹丸」による船上観測をおこなった.海況の穏やかな南極海での観測では,直径0.1 μm以上の既存エアロゾル粒子数濃度が著しく低い条件下で,高濃度の核生成モード粒子(直径&lt;20 nm)を観測することがあった.逆に,既存のエアロゾル粒子数濃度が高い場合には,核生成モード粒子数濃度の増加は見られなかった.2005年1月に「海鷹丸」で観測したリュツォ・ホルム湾洋上のエアロゾル粒子中主要イオン濃度は,昭和基地で1月に観測される平均的な濃度とほぼ同じであった.「海鷹丸」と昭和基地との同時観測の結果,短時間に凝縮核数濃度が高くなるイベントの場合には,核生成モードやエイトケンモード粒子の粒径分布は両者で大きく異なっていた.To investigate spatial and temporal variation of number-size distribution of atmospheric aerosol particles in the Antarctic Ocean, atmospheric observations were conducted on research vessels: Hakuho-maru, Tangaroa, and Umitaka-maru. Concentrations of ionic constituents in aerosols and precursor gases (SO_2 and NH_3) were also measured during the cruises. Concentrations of nucleation mode particles (&lt;20 nm in diameter) were often high under the conditions of very low number concentrations of preexisting aerosol particles larger than 0.1 μm in diameter, when the ocean was calm. Nucleation mode particles did not appear when concentrations of preexisting aerosols were high. Major ionic concentrations of aerosols at Lutzow-Holmbukta observed by Umitaka-maru in January 2005 were almost the same as average values of those in January at Syowa Station. Especially for short-term increasing events in condensation nucleus concentration, large differences were found for number size-distributions of nucleation and Aitken mode particles between Syowa Station and Umitaka-maru in Lutzow-Holmbukta.

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Language：Japanese   Publisher：公益社団法人 大気環境学会  

Hygroscopic properties of atmospheric aerosol particles at Kagurazaka in Tokyo were investigated in four seasons. A tandem differential mobility analyzer system wasused to measure the dependence of particle size on relative humidity (RH) for monodisperse aerosols with dry mobility diameter of 100nm. In summer, the average of number fraction of growth particles at 65%RH and 70%RH was only 23% and 28%, respectively; however that at 78%RH and 83%RH was 50% and 61%, respectively. In the typical case, number fraction and growth factor in summer suddenly increase over 75-80%RH that were near deliquescence relative humidity of (NH4) 2SO4, NaCl or NaNO3. In autumn, number fraction and growth factor at any relative humidity were almost always smaller than those of other seasons. Number fraction of growth particles at 65%RHwas 41% and 59% in spring and winter, respectively, and similarly that at 70%RH was more than in autumn and summer. Especially in winter, number fraction and growth factor at any relative humidity were large. Number fractions at 70%RH were larger when atmospheric temperatures were low or atmospheric relative humidities were high, which suggests that secondary particles production process from gases relates to existence of particles that grow at low relative humidity.

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