10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
The Mixing State of Aerosol Particles in Asian Outflow Observed in the Spring of 2017
CUIZHI SUN, Kouji Adachi, Kentaro Misawa, Joe Hing Cho Cheung, Charles C.K. Chou, Nobuyuki Takegawa, Tokyo Metropolitan University
Abstract Number: 771 Working Group: Aerosol Transport and Transformation
Abstract Anthropogenic emissions of aerosols and trace gases from East Asia have large influences on air quality and climate both on regional and global scales. The mixing state of black carbon (BC) aerosols, which is a key parameter for investigating the radiative impact of aerosols, has not been well understood because analytical methods for quantifying the mixing state of BC is limited. We have conducted an intensive measurement campaign in Taiwan in the spring of 2017, with the main focus being on the chemical composition and mixing state of aerosols in Asian outflow. The measurement was made at the Cape Fuguei (CAFE) station (25°N, 121°E) located on the northern tip of Taiwan from February 21 to March 14 in 2017. The laser induced incandescence-mass spectrometric analyzer (LII-MS) was used to measure the chemical composition of aerosol particles classified by the mixing state of BC. The combination of online LII-MS measurements and offline transmission electron microscope (TEM) analysis can provide useful insights into the variability in the mixing state of aerosols in Asian outflow. The other instruments include an Aerodyne mini aerosol mass spectrometer (mini-AMS), a particle-into-liquid sampler coupled with ion chromatography (PILS-IC), and filter sampling. A comparison of the LII-MS, mini-AMS, PILS-IC, and filter data demonstrates that sulfate, nitrate, and BC were quantified with reasonable accuracy.
Large enhancements in the mass concentration of PM2.5 aerosols were found during the measurement period. Backward trajectory analysis suggests that the enhancements were not due to local sources but to regional transport of air masses from the Asian continent. Sulfate was found to be the dominant chemical composition of fine mode aerosol particles. Nitrate was relatively minor in fine mode and abundant in coarse mode aerosols. The LII-MS data shows that the mass fraction of sulfate internally-mixed with BC was as high as 15% in highly polluted air masses. The variability in the mixing state of BC observed by the LII-MS was qualitatively consistent with that obtained from the TEM analysis. Factors affecting the variability and possible dependence of the LII-MS sensitivity to various types of mixing state (e.g., shell-core, attached) are discussed in detail.