1.

論文(リポジトリ)

論文(リポジトリ)
Deng, Yange ; Fujinari, Hiroaki ; Yai, Hikari ; Shimada, Kojiro ; Miyazaki, Yuzo ; Tachibana, Eri ; Deshmukh, K. Dhananjay ; Kawamura, Kimitaka ; Nakayama, Tomoki ; Tatsuta, Shiori ; Cai, Mingfu ; Xu, Hanbing ; Li, Fei ; Tan, Haobo ; Ohata, Sho ; Kondo, Yutaka ; Takami, Akinori ; Hatakeyama, Shiro ; Mochida, Michihiro
出版情報: Atmospheric Chemistry and Physics.  22  pp.5515-5533,  2022-05-02.  European Geosciences Union — Copernicus Publications
URL: http://hdl.handle.net/20.500.12000/0002017926
概要: Filter-based offline analysis of atmospheric aerosol hygroscopicity coupled to composition analysis provides information complementary to that obtained from online analysis. However, its application itself and comparison to online analysis have remained limited to date. In this study, daily submicrometer aerosol particles (PM0.95, 50 % cutoff diameter 0.95 µm) were collected onto quartz fiber filters on Okinawa Island, a receptor of East Asian outflow, in the autumn of 2015. The chemical composition of water-soluble matter (WSM) in PM0.95, PM0.95 itself, and their respective hygroscopicities were characterized through the offline use of an aerosol mass spectrometer and a hygroscopicity tandem differential mobility analyzer. Thereafter, results were compared with those obtained from online analyses. Sulfate dominated the WSM mass (59 %), followed by water-soluble organic matter (WSOM, 20 %) and ammonium (13 %). WSOM accounted for most (91 %) of the mass of extracted organic matter (EOM) and the atomic O-to-C ratios (O : C) of WSOM and EOM were high (mean ± standard deviation were 0.84 ± 0.08 and 0.78 ± 0.08, respectively), both of which indicate highly aged characteristics of the observed aerosol. The hygroscopic growth curves showed clear hysteresis for most samples. At 85 % relative humidity (RH), the calculated hygroscopicity parameter κ values of the WSM (κWSM), WSOM, EOM, andPM0.95 (κPM0.95 ) were 0.50 ± 0.03, 0.22 ± 0.12, 0.20 ± 0.11, and 0.47 ± 0.03, respectively. An analysis using the thermodynamic Extended Aerosol Inorganics Model (E-AIM) shows, on average, that inorganic salts and WSOM contributed 88 % and 12 %, respectively, of the κWSM (or κPM0.95 ). High similarities were found between offline and online analysis for chemical compositions that are related to particle hygroscopicity (the mass fractions and O : C of organics and the degree of neutralization) and also for aerosol hygroscopicity. As possible factors governing the variation in κWSM, the influences of WSOM abundance and the neutralization of inorganic salts were assessed. At high RH (70 %–90 %), the hygroscopicity of WSM and PM0.95 was affected considerably by the presence of organic components; at low RH (20 %–50 %), the degree of neutralization could be important.This study not only characterized aerosol hygroscopicity at the receptor site of East Asian outflow but also shows that offline hygroscopicity analysis is an appropriate method, at least for aerosols of the studied type. The results encourage further applications to other environments and to more in-depth hygroscopicity analysis, in particular for organic fractions. 続きを見る
2.

論文(リポジトリ)

論文(リポジトリ)
Shimada, Kojiro ; Nohchi, Masayuki ; Maeshima, Koji ; Uchino, Tomonori ; Kobayashi, Yusuke ; Ono, Kazuki ; Ogata, Hiroko ; Katsumi, Naoya ; Inazu, Koji ; Okochi, Hiroshi
出版情報: Scientific Reports.  12  pp.4249-,  2022-03-11.  Springer Nature
URL: http://hdl.handle.net/20.500.12000/0002017922
概要: The concentrations of polycyclic aromatic hydrocarbons (PAHs) in aerosol were measured in Shinjuku, which is central Tok yo, Japan, for 10 years from 2007 to 2016. The efects of changes in emission sources and their degradation by reaction with ozone were assessed in this study. There was no signifcant increasing or decreasing trend of the PAH concentrations during 10 years (P> 0.05). The average selected seven the PAH concentrations (0.88 ng ­m−3) during 10 years was lower than those in New York and Paris. However, the trend of ozone concentrations is increasing in central Tokyo. This inconsistency raises a question. Did the fact that the ozone concentration was higher than the PAH concentrations promote PAH degradation? To apportion the PAH sources, we used PAH concentration profles and positive matrix factorization analysis. The contribution of vehicle emissions to the PAHs ranged from 40 to 80%. Ozone concentrations increased by 3.70%/year during 10 years. The theoretical degradation rates of PAHs by ozone, which were calculated using a pseudo-frst-order rate equation, suggested that the lifetimes of benzo[a]pyrene (BaP) decreased by 1 min from 2007 to 2016. We investigated the aging of BaP using the profle of the isomer ratios. We found that the aging of BaP at the urban and roadside sites were nearly identical indicating aging regardless of the season. Although the decomposition of BaP is promoted by the photochemical oxidation reaction, this result suggests that a certain threshold value exists as the degree of the decomposition. This degradation of PAH can improve chemical loss processes in air quality model. 続きを見る
3.

論文(リポジトリ)

論文(リポジトリ)
Shimada, Kojiro ; Takami, Akinori ; Ishida, Takatsugu ; Taniguchi, Yuta ; Hasegawa, Shuichi ; Chan, K. Chak ; Kim, Pyo Yong ; Lin, Neng-Huei ; Hatakeyama, Shiro
出版情報: Aerosol and Air Quality Research.  21  2021-09.  Taiwan Association for Aerosol Research
URL: http://hdl.handle.net/20.500.12000/0002019347
概要: We investigated the changes in the carbonaceous-aerosol sources and their effects on the long-term elemental carbon (EC) and organic carbon (OC) concentration trends at the Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS) in Okinawa, Japan, during the period 2004-2013. We obtained the EC and OC concentrations by conducting semi-real-time measurements using a carbon monitor, and performing an offline thermal/optical filter analysis according to the Interagency Monitoring of Protected Visual Environments (IMPROVE) protocol. The annual average concentration of the EC remained constant between 2004 and 2013, but that of the OC decreased at a rate of 0.11 µg C m^<-3> y^<-1> (α > 0.05). The secondary OC (SOC)/OC ratio showed an increasing trend from 2004 till 2011, which may have been caused by a reduction in primary emissions of OC and compositional changes in the organic compounds originating in China, from which air pollutants were frequently transported during spring and winter. Although the EC concentration did not change appreciably in either season, the OC concentration decreased at rates of 0.10 µg C m^<-3> y^<-1> and 0.11 µg C m^<-3> y^<-1> during spring and winter, respectively. We estimated the contributions from the various sources of carbonaceous aerosol, viz., biomass burning, fossil-fuel combustion, and air-pollutant transport from China, based on the OC/EC ratio, which decreased from 5.7 to 2.4 in terms of the annual average. The growing share from fossil-fuel combustion is responsible for the decline in biofuel-burning OC emissions transported from China to CHAAMS. 続きを見る
4.

論文(リポジトリ)

論文(リポジトリ)
Miura, Kaori ; Shimada, Kojiro ; Sugiyama, Taichi ; Sato, Kei ; Takami, Akinori ; Chan, K. Chak ; Kim, Sun In ; Kim, Pyo Yong ; Lin, Neng-Huei ; Hatakeyama, Shiro
出版情報: Scientific Reports.  9  pp.12591-,  2019-08-29.  Springer Nature
URL: http://hdl.handle.net/20.500.12000/0002019365
概要: This paper reports the long term observation of particle-associated polycyclic aromatic hydrocarbons (PAHs) at Cape Hedo Atmosphere and Aerosol Monitoring Station, a remote site in the Western Pacifc Ocean, from 2008 to 2015. This is the first long-term study that evaluated the contribution of long-range transport of PAHs in East Asia. No obvious trend (P>0.05) was found in a particular season over the years. However, there are seasonal variations of PAH concentrations with higher in spring and winter. The higher PAH are attributed to air masses from the area including part of China. Source apportionment using three different approaches, i.e., PAH compositional pattern analysis, PAH diagnostic ratio analysis and positive matrix factorization modeling, showed the combined high contribution of biomass burning (18%, 14%) and coal combustion (33%, 24%) in spring and winter. In addition, the contribution of ship emissions (35%) was relatively high in spring, whereas that of vehicle emissions (36%) was relatively high in winter. The contribution of coal combustion to PAH has decreased throughout the years, likely due to changes in energy structure in China. The contribution of biomass burning to PAH has showed no trend, being stable, and that of vehicular emissions has increased. 続きを見る
5.

論文(リポジトリ)

論文(リポジトリ)
Itahashi, Syuichi ; Hatakeyama, Shiro ; Shimada, Kojiro ; Takami, Akinori
出版情報: Aerosol and Air Quality Research.  19  pp.587-600,  2019-03.  Taiwan Association for Aerosol Research
URL: http://hdl.handle.net/20.500.12000/0002019366
概要: Intensive observation campaigns approximately 1 week long were conducted periodically from March 2010 to November 2015 a t Cape Hedo, Okinawa, Japan. The maximum daily mean sulfate aerosol (SO_4^<2->) concentrations surpassed 15 µg m^<–3> in spring 2012. In this study, source apportionment for these high concentrations was conducted using an air quality model with the tagged tracer method, and the main source was identified as volcanoes in March and as anthropogenic emissions from China in April. In March, the prevailing northerly wind transported a volcanic SO_2 plume with a low conversion ratio to Cape Hedo. The impacts of 15 volcanoes in Japan were estimated, and a substantial impact from Sakurajima, which accounted for more SO_2 than anthropogenic emissions from Japan, was found. Because the model had difficulty capturing the highest concentration, three sensitivity simulations were performed to consider the uncertainty of the volcanic SO_2 emission amounts and injection heights, revealing the importance of the injection height in addition to the SO_2 emission amount. Throughout April, contributions from anthropogenic emissions from China were found; hence, this source was further divided into 31 provincial scales. Shandong and Jiangsu Provinces, which are the first and seventh largest emission sources in China, respectively, were identified as significant sources at Cape Hedo. These sources showed day-to-day variation in their contributions, and the highest contribution from Shandong Province occurred on April 23, whereas that from Jiangsu Province occurred on April 22. 続きを見る
6.

論文(リポジトリ)

論文(リポジトリ)
Ou-Yang, Chang-Feng ; Chang, Chih-Chung ; Wang, Jia-Lin ; Shimada, Kojiro ; Hatakeyama, Shiro ; Kato, Shungo ; Chiu, Jia-Yang ; Sheu, Guey-Rong ; Lin, Neng-Huei
出版情報: Aerosol and Air Quality Research.  17  pp.3037-3051,  2017-12.  Taiwan Association for Aerosol Research
URL: http://hdl.handle.net/20.500.12000/0002019359
概要: Air samples were collected at Mt. Fuji Research Station (FRS) for the measurements of volatile organic compounds (VOCs) in the summers of 2015 and 2016. In this study, 24 compounds were analyzed, of which only 12 halocarbons were quantified in 2015. The average total concentrations of target VOCs were 2.62 ± 1.38 and 2.99 ± 0.95 ppb in 2015 and 2016, respectively. The concentrations of individual VOCs ranged from a few ppt to a few ppb, indicating a highly inhomogeneous feature at the FRS. A cluster analysis of 3-day backward trajectories was performed for the sampling time. Except for the aromatic compounds, the VOCs showed relatively low concentrations in association with air masses originating from the coastal region in the low latitudes (15°N–35°N) of East Asia in 2015. By contrast, the clusters with elevated VOC concentrations mainly came from the high latitudes (35°N–60°N) of the Asian continent in 2016. No particular diurnal pattern was found for VOCs and CO, which might have resulted from suppressed mountain-valley winds at the FRS. Halocarbons regulated by the Montreal Protocol showed low variability and were in favorable agreement with background values at the Gosan station (GSN) and those reported in the literature. Other partially halogenated compounds with higher variability, such as CH_3Cl and CHCl_3, showed discrepancies at the FRS and GSN. 1,2-dichloroethane (R-150), 1,1-dichloroethane (R-150a), and 1,4-dichlorobenzene (p-DCB) were also measured at the FRS with concentrations of 24 ± 14, 38 ± 13, and 13 ± 10 ppt, respectively, in 2015. A close relationship between n-pentane and i-pentane with R^2 more than 0.85 was found in both 2015 and 2016. Low ratios of n/i-pentane ranging from 0.25 to 0.67 were observed in the free troposphere at the FRS, comparable to most mountain stations. 続きを見る
7.

論文(リポジトリ)

論文(リポジトリ)
Cai, Mingfu ; Tan, Haobo ; Chan, K. Chak ; Mochida, Michihiro ; Hatakeyama, Shiro ; Kondo, Yutaka ; Schurman, I. Misha ; Xu, Hanbing ; Li, Fei ; Shimada, Kojiro ; Li, Liu ; Deng, Yange ; Yai, Hikari ; Matsuki, Atsushi ; Qin, Yiming ; Zhao, Jun
出版情報: Aerosol and Air Quality Research.  17  pp.3194-3208,  2017-12.  Taiwan Association for Aerosol Research
URL: http://hdl.handle.net/20.500.12000/0002019360
概要: A suite of advanced instruments were employed to measure aerosol hygroscopicity, volatility and chemical composition at a suburban site in the Pearl River Delta (PRD) Region and at a marine site in Okinawa, respectively. The results showed that the particle number concentration in PRD is approximately ten times higher than that in Okinawa. Organics contributes about one half of the total NR-PM_1 concentration in PRD, while sulfate is the dominant component (about 60%) in Okinawa. Diurnal variation of the chemical species demonstrated that the site in PRD was affected by trafficrelated sources and industrial emissions, while the one in Okinawa is mainly affected by regional emissions. The V-TDMA measurements showed that a large fraction (20-45%) of particles in Okinawa volatilized at about 200°C and nearly all particles volatilized at about 300°C, indicating that the particles were almost volatile in Okinawa. In contrast, a fraction (15-21%) of particles in PRD did not evaporate even when heated to about 300°C, implying that these particles might contain black carbon or low-volatile organics. For 40-200 nm particles in Okinawa, the hygroscopicity parameter κ is around 0.5, significantly higher than that of PRD particles (κ ≈ 0.26). Particles tend to have bimodal distribution in PRD and unimodal in Okinawa, indicating that the former is externally mixed while the latter is internally mixed. 続きを見る
8.

論文(リポジトリ)

論文(リポジトリ)
Tatsuta, Shiori ; Shimada, Kojiro ; Chan, K. Chak ; Kim, Pyo Yong ; Lin, Neng-Huei ; Takami, Akinori ; Hatakeyama, Shiro
出版情報: Aerosol and Air Quality Research.  17  pp.3119-3127,  2017-12.  Taiwan Association for Aerosol Research
URL: http://hdl.handle.net/20.500.12000/0002019361
概要: We observed the size distributions of mass concentration, ionic composition, and trace metal concentration in aerosols c ollected at an urban site in Kumamoto Prefecture (KM) and a rural site at Cape Hedo in Okinawa Prefecture (HD) between 2012 and 2015. To evaluate the contribution of transboundary nitrate and locally emitted nitrate in the aerosols at Kumamoto, we distinguished between days of transboundary air pollution from East Asia and days of local air pollution on the basis of a threshold for Pb concentration and the ratio Pb (in 0.5 < projected area diameter (Dp) < 1.0 µm)/Cu (in 2.5 < Dp < 10 µm). Fine nitrate (particulate NH_4NO_3) did not arrive at HD from the Asian continent even under long-range transport conditions. Fine nitrate emitted in Kumamoto and its vicinity also was not transported to HD, even in an air mass that passed over KM and reached HD within one day. Almost all fine nitrate was converted to coarse nitrate during transport by dissociation of fine nitrate and adsorption of HNO_3 on larger aerosol particles. Transboundary nitrate existed largely in the particle size range of 0.5 < Dp < 10 µm, and the contribution of transboundary nitrate in the particle size range of 0.1 < Dp < 0.5 µm was about 20% even under long-range transport conditions. The contribution of transboundary nitrate in particles with Dp < 2.5 µm at KM was approximately 50%, 50%, and 80% in spring, autumn, and winter, respectively. 続きを見る
9.

論文(リポジトリ)

論文(リポジトリ)
Sugiyama, Taichi ; Shimada, Kojiro ; Miura, Kaori ; Lin, Neng-Huei ; Kim, Pyo Yong ; Chan, K. Chak ; Takami, Akinori ; Hatakeyama, Shiro
出版情報: Aerosol and Air Quality Research.  17  pp.3106-3118,  2017-12.  Taiwan Association for Aerosol Research
URL: http://hdl.handle.net/20.500.12000/0002019362
概要: We developed an index to investigate the effect of transboundary air pollution (TAP) on the air quality of Kumamoto City, Japan. We estimated the effect of TAP by using the index and positive matrix factorization (PMF). Polycyclic aromatic hydrocarbons (PAHs) and trace metals were analyzed from the daily samples of the Total Suspended Particles (TSPs) collected seasonally from Oct. 2014 to Aug. 2015. These chemical components exhibited high concentrations in spring and winter, which is consistent with the data in the literature. Pb was identified as the TAP tracer owing to its high concentrations in winter and spring. Indeno(1, 2, 3-cd)pyrene (IcdP) was used as the local emission tracer in Kumamoto on the basis of previous studies. We applied the IcdP/Pb ratio as the index. The index enables the detection of TAP in daily data sets. PMF identified six factors: soil and road dust, biomass and waste burning, heavy oil combustion, fishing boats, vehicle emission, and coal combustion. The average contribution of TAP on the days when transboundary pollution was high was evaluated as being 46%. 続きを見る
10.

論文(リポジトリ)

論文(リポジトリ)
Itahashi, Syuichi ; Hatakeyama, Shiro ; Shimada, Kojiro ; Tatsuta, Shiori ; Taniguchi, Yuta ; Chan, K. Chak ; Kim, Pyo Yong ; Lin, Neng-Huei ; Takami, Akinori
出版情報: Aerosol and Air Quality Research.  17  pp.3079-3090,  2017-12.  Taiwan Association for Aerosol Research
URL: http://hdl.handle.net/20.500.12000/0002019364
概要: An intensive observation campaign at Cape Hedo, Okinawa, Japan was conducted from late October to early November 2015 to investigate the behavior of long-range transported atmospheric pollutants. During this period, sulfate (SO_4^<2->) was the dominant aerosol component. The sources of SO_4^<2-> were estimated by using the air quality model with the tagged tracer method. The main source of high SO_4^<2-> concentration varied day-to-day. When the westerly wind was dominant (October 27), the main source was anthropogenic SO_2 emissions in China. When the northerly wind prevailed (November 1), the impact of volcanoes in western Japan was significant and the conversion ratio from SO_2 to SO_4^<2-> was lowest, at less than 70%, because of the faster transport. During the latter part of the campaign, the northerly to easterly winds were prominent, and the impacts of Korea, Japan, and ships on SO_4^<2-> observed at Cape Hedo were also clear. When the contributions from Korea, Japan, and ships were the highest (November 4), the conversion ratio was also the highest, at greater than 95% because of long-range transport. The modeled sources of volcanoes and ship emissions corresponded well with the observed coarse-mode SO_4^<2-> and V/Mn ratio, respectively. The mutual evaluation of sources from model and observations enable SO_4^<2-> sources to be estimated with higher confidence. 続きを見る