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RISS 인기검색어
- 검색키워드
- 저자 : Syuichi Itahashi (검색결과 3 건)
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Satoru Chatani,Syuichi Itahashi,Kazuyo Yamaji 한국대기환경학회 2021 Asian Journal of Atmospheric Environment (AJAE) Vol.15 No.2
Continuous monitoring of hourly PM2.5 component concentrations has been performed in Japan. The objective of this study was to evaluate the advantages of continuous monitoring to obtain data that can be useful for regional air quality simulations. Inclusion of transboundary transport in the simulations improved the correlation between the observed and simulated hourly concentrations of SO4 2-, NO3 -, secondary organic aerosols (SOA), and metals in PM2.5. Black carbon was an exception, suggesting the overestimation of emissions in upwind countries. Including volcanic and dust emissions also improved the correlations between the observed and simulated hourly concentrations of SO4 2- and metals, respectively. However, despite the good correlation achieved by including transboundary transport, it also resulted in overestimated NO3 - and SOA concentrations in western Japan during the winter. Further improvements are necessary, such as balancing with SO4 2- and the dry deposition of gaseous HNO3 for NO3 -, and new treatment of the partitioning and aging of semivolatile organic aerosols, which have been incorporated into recent models for SOA. The differences in model performance with regard to simulating metal concentrations suggest imbalances in the speciation profiles used for countries other than Japan. Further, comparing the observed and simulated hourly concentrations helped identify the key processes driving air quality. This revealed evening peaks in black carbon concentrations, owing to the relatively stable atmosphere; and early morning peaks in NO3 - concentration, owing to the low temperature and high humidity through thermodynamic equilibrium. This study demonstrated that continuous monitoring of hourly variations in PM2.5 composition is valuable for understanding the roles of the emission sources and for improving future models, both of which contribute to deriving effective PM2.5 suppression strategies.
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Yusuke Kiriyama,Hikari Shimadera,Syuichi Itahashi,Hiroshi Hayami,Kazuhiko Miura 한국대기환경학회 2015 Asian Journal of Atmospheric Environment (AJAE) Vol.9 No.1
Increasing ozone concentrations are observed overJapan from year to year. One cause of high ozoneconcentration in the Kanto region, which includesareas inland from large coastal cities such as metropolitanTokyo, is the transportation of precursors bysea breezes. However, high ozone concentrationsare also observed in the morning, before sea breezesapproach inland areas. In this point, there would bea possibility of residual ozone existing above thenocturnal boundary layer affects the ozone concentrationin the following morning. In this study, weutilized the Weather Research and Forecasting modeland the Community Multiscale Air Quality model toevaluate the effect of regional precursors and residualozone on ozone concentrations over the inlandKanto region. The results show that precursors emittedfrom non-metropolitan areas affected inlandozone concentrations more than did precursors frommetropolitan areas. Moreover, calculated resultsindicate downward transportation of residual ozone,resulting in increased concentration. The residualozone was also affected by precursors emitted fromnon-metropolitan areas.
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Hiroshi Hayami,Yuta Iga,Syuichi Itahashi,Kazuhiko Miura,Tatsuhiro Mori,Tatsuya Sakurai 한국대기환경학회 2022 Asian Journal of Atmospheric Environment (AJAE) Vol.16 No.3
The global limit on the sulfur content of ship fuel was reduced from 3.50% to 0.50% in January 2020 to reduce ship emissions of SO2 and particulate matter. We conducted observational campaigns before and after the new global limit was introduced to detect changes in coastal air quality. We measured ambient concentrations of SO2 and CO2 ship plumes on shore with the sniffing method under the Kanmon Bridge over the Kanmon Straits between Honshu and Kyusyu Islands, Japan, for several weeks in August to September in 2019 and 2020. The fuel sulfur content (FSC) estimated from our measurements mainly varied from 0.50% to 3.00% in 2019, whereas the range narrowed to 0.10% to 0.40% in 2020, showing that all the ships complied. The mean FSC in 2020 was reduced to 16% of that in 2019, which was consistent with the reduction in the ambient SO2 concentration. Sakurai et al. (2021) estimated that after the 2020 global limit was brought in, SO2 emissions from ships were reduced to 24% of their previous values by assuming that all ships have a FSC of 0.50%. Our results indicate the 2020 global limit led to much greater reductions in SO2 emissions from ships than expected.
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