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| 1.
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論文（リポジトリ）
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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
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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.
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| 2.
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Shimada, Kojiro ; Nohchi, Masayuki ; Maeshima, Koji ; Uchino, Tomonori ; Kobayashi, Yusuke ; Ono, Kazuki ; Ogata, Hiroko ; Katsumi, Naoya ; Inazu, Koji ; Okochi, Hiroshi
概要:
The concentrations of polycyclic aromatic hydrocarbons (PAHs) in aerosol were measured in Shinjuku, which is central Tok
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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.
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| 3.
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Shimada, Kojiro ; Nohchi, Masayuki ; Maeshima, Koji ; Uchino, Tomonori ; Kobayashi, Yusuke ; Ogata, Hiroko ; Katsumi, Naoya ; Inazu, Koji ; Okochi, Hiroshi
概要:
The concentrations of polycyclic aromatic hydrocarbons (PAHs) in aerosol were measured in Shinjuku, which is central Tok
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yo, Japan, for 10 years from 2007 to 2016. The effects of changes in emission sources and their degradation by reaction with ozone were assessed in this study. There was no significant 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 profiles 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-first-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 profile 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.
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| 4.
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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)
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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.
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| 5.
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山脇, 拓実 ; Yamawaki, Takumi ; 大河内, 博 ; Okochi, Hiroshi ; 山本, 修司 ; Yamamoto, Shuji ; 山之越, 恵理 ; Yamanokoshi, Eri ; 島田, 幸治郎 ; Shimada, Kojiro ; 緒方, 裕子 ; Ogata, Hiroko ; 勝見, 尚也 ; Katsumi, Naoya ; 皆巳, 幸也 ; Minami, Yukiya ; 加藤, 俊吾 ; Kato, Shungo ; 三浦, 和彦 ; Miura, Kazuhiko ; 戸田, 敬 ; Toda, Kei ; 和田, 龍一 ; Wada, Ryuichi ; 竹内, 政樹 ; Takeuchi, Masaki ; 小林, 拓 ; Kobayashi, Hiroshi ; 土器屋, 由紀子 ; Dokiya, Yukiko ; 畠山, 史郎 ; Hatakeyama, Shiro
概要:
At the summit of Mt. Fuji in July and August from 2012 to 2018, 27 kinds of anthropogenic volatile organic compounds (AV
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OCs) and 6 types of biogenic volatile organic compounds (BVOCs) in the air and in cloud water were determined. AVOCs occupied about 90％ of the VOCs in the cloud water (volume-weighted mean VOCs concentration: 2.07 nM, n＝159) and the main component was toluene, reflecting its high concentration in the ambient air. The concentration of the AVOCs in the cloud water was high when the airmass was transported from the southern continent and was about 1.5 times higher than that when it came from the ocean. The concentration of toluene in the cloud water decreased exponentially with the increase in the total ion concentration. The concentrations of some VOCs such as chloroform, o-xylene, and limonen in the cloud water were several times higher than their Henryʼs law predicted values. Among the chlorinated hydrocarbons, highly hydrophobic chloroform was more concentrated than dichloromethane in the cloud water. Atmospheric surfactants such as HULIS (Humic-like Substances) could affect the enrichment of the VOCs in the cloud water even in the free troposphere.
2010年から2018年までの7月と8月に富士山頂（標高3,776 m）で大気および雲水を採取して、27種類の人為起源揮発性有機化合物 (AVOCs) （塩素化炭化水素16種、単環芳香族炭化水素8種、二環芳香族炭化水素3種）と6種類の生物起源揮発性有機化合物を分析した。雲水中VOCs （体積加重平均VOCs濃度： 2.07 nM、n＝159）の約9割はAVOCsであり、主成分はトルエンであった。これは富士山頂における大気中トルエン濃度が高いことを反映していた。雲水中AVOCs濃度は空気塊が大陸南部から輸送されたときに高く、最低濃度を示した海洋由来時の約1.5倍であった。雲水中トルエン濃度は総無機イオンの低下とともに指数関数的に減少した。雲水中クロロホルム、o-キシレン、リモネン濃度は大気中濃度とヘンリー定数から求めた計算値に比べて実測値は数倍高く、ヘンリー則からの予測値以上に濃縮されていた。疎水性が高いVOCsほど雲水に高濃縮されており、自由対流圏における雲水でもHULIS （フミン様物質）のような界面活性物質がVOCsの高濃縮に関与していることが示唆された。 続きを見る |
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| 6.
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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
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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.
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| 7.
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論文（リポジトリ）
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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
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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.
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| 8.
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論文（リポジトリ）
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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
概要:
Air samples were collected at Mt. Fuji Research Station (FRS) for the measurements of volatile organic compounds (VOCs)
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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.
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| 9.
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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
概要:
A suite of advanced instruments were employed to measure aerosol hygroscopicity, volatility and chemical composition at
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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.
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| 10.
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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
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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.
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| 11.
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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
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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%.
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| 12.
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論文（リポジトリ）
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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
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(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.
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| 13.
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論文（リポジトリ）
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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,
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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.
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| 14.
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Matsunaga, N. Sou ; Shimada, Kojiro ; Masuda, Tatsuhiko ; Hoshi, Junya ; Sato, Sumito ; Nagashima, Hiroki ; Ueno, Hiroyuki
概要:
Ozone concentration in Tokyo Metropolitan area is one of the most serious issues of the local air quality. Tropospheric ozone is formed by radical reaction including volatile organic compound (VOC) and nitrogen oxides (NOx). Reduction
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of the emission of reactive VOC is a key to reducing ozone concentrations. VOC is emitted from anthropogenic sources and also from vegetation (biogenic VOC or BVOC). BVOC also forms ozone through NOx and radical reactions. Especially, in urban area, the BVOC is emitted into the atmosphere with high NOx concentration. Therefore, trees bordering streets and green spaces in urban area may contribute to tropospheric ozone. On the other hand, not all trees emit BVOC which will produce ozone locally. In this study, BVOC emissions have been investigated (terpenoids: isoprene, monoterpenes, sesquiterpenes) for 29 tree species. Eleven in the 29 species were tree species that did not emit BVOCs. Three in 12 cultivars for future planting (25%) were found to emit no terpenoid BVOCs. Eight in 17 commonly planted trees (47%) were found to emit no terpenoid BVOC. Lower-emitting species have many advantages for urban planting. Therefore, further investigation is required to find the species which do not emit terpenoid BVOC. Emission of reactive BVOC should be added into guideline for the urban planting to prevent the creation of sources of ozone. It is desirable that species with no reactive BVOC emission are planted along urban streets and green areas in urban areas, such as Tokyo.
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| 15.
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峰島, 知芳 ; Minejima, Chika ; 中根, 令以 ; Nakane, Ray ; 島田, 幸治郎 ; Shimada, Kojiro ; 利谷, 翔平 ; Riya, Shohei ; 佐藤, 啓市 ; Sato, Keiichi ; 大山, 正幸 ; Ohyama, Masayuki ; 寺田, 昭彦 ; Terada, Akihiko ; 細見, 正明 ; Hosomi, Masayuki
概要:
It has been recently reported that the direct emission of nitrous acid (HONO) from soils can be a significant source of
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HONO especially during the day when a sufficient HONO source has not been found. In this study, the direct HONO emission from rice paddy soil was measured in the field during the mid-summer drainage period. To investigate the impact of fertilization, the system with a traditional amount of fertilization (the chemical nitrogen fertilizer system) and a non-fertilized system (the control system) were prepared. The maximum flux was 40.4 ng/m^2/s which was observed after the soil oxidation reduction potential (Eh) had increased from negative values to positive values. The flux was higher during the daytime (3.5±0.9 ng/m2^/s) than the nighttime (1.0±0.3 ng/m^2/s). This cannot be explained only by the shift in the chemical equilibrium. The chemical nitrogen fertilizer system had a greater HONO flux than the control system on average. The reason could be that the chemical nitrogen fertilizer system has a lower soil moisture content. It was found that the direct emission amount from rice paddy soils may have a non-negligible impact on the atmospheric HONO concentrations.
土壌からの亜硝酸ガス (HONO) の直接発生が昼間に存在する未解明のHONO発生源となり得る可能性が指摘されている。我々は、水田の中干し期間に、ダイナミックチャンバー法とフィルターパック法を用いてHONOの直接発生量を測定した。観測されたフラックスは、先行研究と同様の値で、最大値は40.4 ng/m^2/sであり、土壌の酸化還元電位 (Eh) が負の還元状態から正の酸化状態に変化した後であった。また、フラックスは日中に多く (3.5±0.9 ng/m^2/s)、夜間に少なかったが (1.5±0.3 ng/m^2/s)、フラックスの増大は土壌温度の変化による化学平衡の偏りと気液平衡だけでは説明できなかった。肥料施肥の影響を調べるために、化学窒素肥料を慣行量施肥した系（施肥系）と、無施肥の系（コントロール系）の2系を比較した結果、施肥系の方がコントロール系よりHONOフラックスが平均して大きかった。これは、土壌中のNO_2^－、NO_3^－に差がなかったことから、施肥系の方が土壌の含水率が低かったことが原因として考えられる。今回観測されたフラックスの大気中HONO濃度への影響は無視できない大きさであることがわかった。 続きを見る |
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| 16.
論文（リポジトリ） |
論文（リポジトリ）
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松永, 壮 ; Matsunaga, N. Sou ; 石倉, 淳士 ; Ishikura, Atsushi ; 島田, 幸治郎 ; Shimada, Kojiro ; 星, 純也 ; Hoshi, Junya ; 齊藤, 伸治 ; Saito, Shinji ; 上野, 広行 ; Ueno, Hiroyuki
概要:
The high ozone concentration in urban atmospheres including Tokyo is still one of the important environmental issues. On
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e of the possible causes is ozone formation by unconsidered VOC. In this study, we performed chamber experiments to understand the importance of biogenic VOCs emitted from urban green flora. Isoprene and α-pinene were added to ambient air and irradiated by UV. The ozone and formaldehyde concentrations were measured to compare the ozone formation potential with the control. The ozone formation potential of isoprene was also compared to that of toluene. Considering the typical emission rates of isoprene and α-pinene, 10 and 0.7 ppbv of these VOCs were separately added to the ambient air in the chamber. Both isoprene and α-pinene showed approximately 30％ higher ozone concentrations compared to the control after 6 h of UV irradiation. On the other hand, isoprene showed a 33％ higher ozone concentration than toluene for a 10 ppbv addition to the ambient air after 6 h of reaction. This means that the ozone formation by biogenic VOC is important as well as that of anthropogenic VOCs, such as toluene, which is a typical anthropogenic VOC. The possibility that biogenic VOCs emitted from green areas and street trees are important for ozone formation has been suggested by this study.
都市におけるオゾン高濃度は現在も解決できていない環境問題の一つである。その原因の一つとして考えられるのが、未考慮のVOCによるオゾン生成である。そこで本研究では、都市緑地や街路樹から放出される生物起源VOCによるオゾン生成の重要性を確認することを目的にチャンバー実験を行った。この実験では、実大気をフッ素樹脂製のバッグに充填し、そこへ代表的な生物起源VOCである、イソプレンとα-ピネン、人為起源VOCであるトルエンを添加し、UVを照射しオゾン濃度と、これもオゾン生成能が大きく毒性の高いホルムアルデヒド濃度を測定した。UV照射を行い6時間後のオゾン濃度を何も添加しない実大気であるコントロールと比較したところ、イソプレン、α-ピネンのいずれの場合でもオゾン濃度はコントロールに比べて約30％高くなった。また、イソプレンとトルエンを同量添加して行った並行実験では、反応開始6時間後にはイソプレンの方が平均で33％高いオゾン濃度を示した。こうした結果からイソプレンが都市大気中で大きなオゾン生成能を持つことが確認できた。本研究によって、生物起源VOCによるオゾン生成が人為起源VOCによるオゾン生成に対して重要である可能性が示された。 続きを見る |
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| 17.
論文（リポジトリ） |
論文（リポジトリ）
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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)
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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
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| 18.
論文（リポジトリ） |
論文（リポジトリ）
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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
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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 |
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| 19.
論文（リポジトリ） |
論文（リポジトリ）
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Shimada, Kojiro ; Sheikh, M. Ali. ; Okuma, Y. ; Itoh, M. ; Fujimura, H. ; Shinzato, N. ; Yamamoto, H. ; Daigo, K. ; Shioi, Y. ; Oomori, T.
概要:
琉球大学21世紀COEプログラム「サンゴ礁島嶼系の生物多様性の総合解析」平成19年度成果発表会（平成20年3月1日開催） 招待講演会会場：理系複号棟102号室，ポスター発表会場：琉球大学50周年記念館1F
研究報告書 |
