※一部利用できない機能があります
| 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
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 ; Takami, Akinori ; Ishida, Takatsugu ; Taniguchi, Yuta ; Hasegawa, Shuichi ; Chan, K. Chak ; Kim, Pyo Yong ; Lin, Neng-Huei ; Hatakeyama, Shiro
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
|
||||
| 3.
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
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
|
||||
| 4.
論文（リポジトリ） |
論文（リポジトリ）
|
Itahashi, Syuichi ; Hatakeyama, Shiro ; Shimada, Kojiro ; Takami, Akinori
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
|
||||
| 5.
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
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
|
||||
| 6.
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
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
|
||||
| 7.
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
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
|
||||
| 8.
論文（リポジトリ） |
論文（リポジトリ）
|
Taniguchi, Yuta ; Shimada, Kojiro ; Takami, Akinori ; Lin, Neng-Huei ; Chan, K. Chak ; Kim, Pyo Yong ; Hatakeyama, Shiro
概要:
Trace metals in aerosols were observed at an urban site (Kumamoto, Kyushu, Japan) and a rural site (Cape Hedo, Okinawa,
…
Japan) to investigate the relative contributions of transboundary air pollutants from mainland Asia and local air pollutants in western Japan. We used a cascade impactor to collect aerosols in five size classes. We apportioned the sources of the air masses on the basis of elemental components. Transboundary and local air pollutants were distinguished by use of the Pb/Cu and V/As ratios in selected size fractions of aerosols. The contribution of Pb (primarily from coal combustion in China) to total anthropogenic elements was greatest in spring, autumn, and winter in the 0.5-1 µm size fraction at both collection sites. The atmospheric environment at both sites was affected by this transboundary air pollutant. The contribution of Cu (primarily from local vehicle traffic) to total anthropogenic elements was greatest in all seasons in the 2.5-10 µm fraction at Kumamoto. Local air pollutants such as road dust, automobile brake abrasion, and waste incineration affected ambient air quality in Kumamoto. Because these pollutants resided mainly in the coarse aerosol fraction (> 2.5 µm), most of them were not transported to Cape Hedo in air bodies that we were able to trace to Kumamoto by backward projection. Based on our data the ambient air quality at Cape Hedo was little affected by local air pollutants emitted in the Kumamoto area.
続きを見る
|
||||
| 9.
論文（リポジトリ） |
論文（リポジトリ）
|
Shimada, Kojiro ; Shimada, Masamichi ; Takami, Akinori ; Hasegawa, Shuichi ; Fushimi, Akihiro ; Arakaki, Takemitsu ; Watanabe, Izumi ; Hatakeyama, Shiro
概要:
This study investigated the source categories and emission areas of carbonaceous aerosols transported from East Asia to the East China Sea. Mass concentrations of heavy metals, ionic components, organic carbon, and elemental carbon (EC)
…
were measured at the Cape Hedo Atmosphere and Aerosol Monitoring Station in Okinawa, Japan, throughout 2010. The relative influences of different categories of aerosols were determined by positive matrix factorization, and the source regions of each emissions category were evaluated by using the total potential source contribution function. Five source categories were identified: dust, sea salt and nitrate, secondary species, coal combustion, and oil combustion. The results showed that the major source of aerosols in North China is coal combustion, whereas the major source in South China, Japan, and Korea is oil combustion. The relative contributions of the five sources to EC concentrations at Cape Hedo were dust 7.0%, sea salt and nitrate 19.1%, secondary species 28.5%, oil combustion 12.8%, and coal combustion 32.6%. In particular, wintertime coal combustion in residential areas of North China contributed significantly to EC in 2010. The results also indicate that the contribution of coal combustion in source areas was higher in winter (52%), whereas the contribution of oil combustion was higher in spring (33%).
続きを見る
|
||||
| 10.
論文（リポジトリ） |
論文（リポジトリ）
|
島田, 幸治郎 ; Shimada, Kojiro ; 高見, 昭憲 ; Takami, Akinori ; 加藤, 俊吾 ; Kato, Shungo ; 梶井, 克純 ; Kajii, Yoshizumi ; 畠山, 史郎 ; Hatakeyama, Shiro
概要:
Seasonal variation and origin of long-range transported carbonaceous aerosols from East Asia to the East China Sea were
…
investigated. The mass concentrations of elemental carbon (EC), organic carbon (OC), particulate matter smaller than 2.5 μm (PM_<2.5>) and gaseous CO were measured at the Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS) located on Okinawa, Japan, in 2004-2008. The concentrations of these chemical substances were simultaneously high during the spring and winter (EC: 0.14 - 0.19 μg C/m^3, OC: 0.62 - 0.82 μg C/m^3, PM_<2.5>: 14.8 - 19.9 μg/m^3, O_3: 43 - 55 ppbv, CO: 183 - 221 ppbv) but low during summer (EC: 0.03 - 0.08 μg C/m^3, OC: 0.28 - 0.44 μg C/m^3, PM_<2.5>: 9.85 - 14.8 μg/m^3, O_3: 14 - 23 ppbv, CO: 68 - 93 ppbv). It was postulated that pollutants were transported to CHAAMS by migratory high pressures and cold fronts from the Asian continent during the spring and winter, whereas a monsoon transported the oceanic air mass from the Pacific during the summer. The contributions of the carbonaceous aerosol concentrations from China were noticeably higher according to the EC, OC and emissions. The carbonaceous aerosol origin was identified by the OC/EC ratios and the correlation betweenthe EC and OC. The OC/EC ratio was low during the spring and winter (OC/EC: 5.7 - 8.0), but high during the summer (OC/EC: 10.2 - 18.9). These results implied a similar conclusion, i.e., the anthropogenic pollutants were transported to CHAAMS from Asia in the spring and winter, whereas in the summer, a monsoon transported the oceanic clean air mass. A photochemical oxidation reaction was also identified from the high OC/EC ratio. Based on the back trajectories of the air masses, the correlations between the OC/EC showed that the origin of the carbonaceous aerosols in North China (NC) was different from South China (SC). It is also suggested that origin of the carbonaceous aerosols in Japan (JP) and Korea (KR) have an influence on the formations of the secondary organic carbon (SOC) via the reactions of the VOCs, causing the OC fraction to increase.
東アジアから東シナ海に長距離輸送される炭素質エアロゾルについて季節変化を調べ発生源及び起源推定を行った。EC、OC、PM_<2.5> 重量濃度、O_3 、CO は沖縄県辺戸岬に設置されている国立環境研究所大気エアロゾル観測ステーションにて 2004年から 2008 年まで観測を行った。EC（0.14 - 0.19 μg C/m^3）、OC（0.62 - 0.82 μg C/m^3）、PM_<2.5>（14.8 - 19.9 μg/m^3）、O_3（43 - 55ppbv）、CO（183 - 221 ppbv） 濃度は春季、冬季に高く、一方で EC（0.03 - 0.08 μg C/m^3）、OC（0.28 - 0.44 μg C/m^3）、PM_<2.5>（9.85 - 14.8 μg/m^3）、O_3（14 - 23 ppbv）、CO（68 - 93 ppbv） 濃度は夏季に低い挙動を示していた。冬季には主に北西季節風、春季には移動性高気圧と寒冷前線によってアジア大陸から大気汚染物質が輸送される一方で、夏季は太平洋からの清浄な空気が辺戸岬に輸送された。後方流跡線で発生源判別した EC、OC 濃度とエミッションデータの結果から、中国から輸送される炭素質エアロゾル濃度の寄与が高いことが考えられる。 次に炭素質エアロゾルの OC/EC 比から起源推定を行った。OC/EC 比は（5.7 - 8.0）春季、冬季に低く、一方で OC/EC 比は（10.2 - 18.9）夏季に高い値を示した。この OC/EC 比の季節変動は各成分濃度の季節変動と次のように説明できる。アジア大陸から輸送された炭素質エアロゾルは化石燃料燃焼起源の影響が強く、また、光化学酸化反応の影響が示唆される。さらに、後方流跡線で発生源判別した OC と EC 関係とエミッションデータから算出した OC/EC 比の結果から、中国国内でも炭素質エアロゾルを構成する物質の燃焼起源は異なっていることが考えられる。また、日本、韓国起源の汚染気塊においては VOCから OC への光化学酸化反応の影響が大きく、OC の割合が増加していた事が考えられる。 続きを見る |
