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| 1.
論文（リポジトリ） |
論文（リポジトリ）
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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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| 2.
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 |
