Investigation of long-range transported PM2.5 events over Northern Taiwan during 2005–2015 winter seasons

• Published in: Atmospheric environment (1994) Vol. 217; p. 116920
• Main Authors: Hung, Wei-Ting, Lu, Cheng-Hsuan (Sarah), Wang, Sheng-Hsiang, Chen, Sheng-Po, Tsai, Fujung, Chou, Charles C.-K.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-11-2019
• Subjects: Aerosol composition analysis; Asian dust; Chinese haze; Long-range transport; PM2.5; Aerosol composition analysis; Chinese haze; Asian dust; Long-range transport; PM2.5
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2019.116920

In-situ PM2.5 observations and the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) aerosol reanalysis were analyzed to characterize long-range transported high PM2.5 events over Northern Taiwan during winter seasons. MERRA-2 aerosol composition was evaluated using independent in-situ observations at the Cape Fuguei (CAFE) site. Results showed that MERRA-2 was able to distinguish the contribution of different species within complicated aerosol mixtures. Fifty transported high PM2.5 events were identified during the winters of 2005–2015. To investigate the transport characteristics associated with Asian continental outflow, these events were further classified into sulfate-dominated, dust-dominated and mixed-composition events. More than 80% of transported events were influenced by Asian dust and 20% of them were dust-dominated. Both sulfate-dominated and dust-dominated events showed similar average PM2.5 concentrations (~44 μg m−3), while dust-dominated events showed a higher average PM10 concentration (114 μg m−3) and thus a lower PM2.5/PM10 ratio (0.41) compared to sulfate-dominated events (94 μg m−3 and 0.46, respectively). Results indicated that the low-level trough at 700 hPa plays a critical role in determining the transport paths of dust aerosols and their impact on local air quality. Therefore, the influence of Asian dust over Northern Taiwan cannot be neglected during winter seasons, and could potentially offset the effectiveness of emission controls and pollutant reductions. Such potential impacts could occur over vast areas affected by Asian continental outflow. The utilization of aerosol reanalysis provided valuable insights for long-range transport studies in the regions with complicated aerosol compositions.
•A systematic procedure is used to identify long-range transported high PM2.5 event.•More than 80% of wintertime transported events were affected by Asian dust.•Contributions of Chinese haze were relatively constant during transported events.•Meteorology plays a critical role in the transport pattern of dust aerosols.•Transported dust may potentially offset the effectiveness of emission controls.