Elemental compositions and sizes of carbonaceousfly ash particles fromatmospheric deposition collected at Cape Hedo, Okinawa, Japan:Implications for their long-range transportation and source region variation

Özet

Spheroidal carbonaceous particles (SCPs) are a type of carbonaceousfly ash resulting from high-temperatureindustrial fossil fuel combustion. In this study, we examined thefluxes, elemental compositions (18 elementsincluding silicon, sulfur, and aluminum but not carbon) and sizes of dry-deposited SCPs in the atmosphere atCape Hedo (the northernmost part of Okinawa Island) to assess the temporal variation. The study site at CapeHedo is suitable for investigating atmospherically deposited SCPs, particularly for evaluating their long-rangetransportation, because Cape Hedo is situated in an outflow region of East Asian pollutants. High SCPfluxesmostly occurred in autumn and winter when air masses came from the Asian continent. Additionally, we de-termined the temporal variations in the elemental compositions and the sizes of the SCPs during four week-longsampling periods and these results suggest that the high SCPfluxes were due to the transportation of the particlesfrom the Asian continent to the study site. The potential source regions of the particles during respective periodsare very consistent with the backward air mass trajectories. Results of our study would imply that sources of theSCPs deposited in the area changed temporarily, and that coarse particulate-pollutants such as SCPs weretransported from the eastern Asian continent to Okinawa Island during the periods under specific meteorologicalconditions. Ourfindings suggest that the examination of SCPs from atmospheric deposition can contribute to theassessment of atmospheric transportation, specifically for particulate pollutants in the atmospheric boundarylayer.