10:00 〜 10:15
[AAS12-17] 2014年及び2015年富士山で捕集したエアロゾルの個別粒子分析
キーワード：大気エアロゾル、透過型電子顕微鏡、個別粒子分析
Atmospheric aerosol particles impact on climate effects by scattering and absorbing solar radiation directly, and by changing radiative properties of clouds indirectly as cloud condensation nuclei (CCN). Climate effects of atmospheric aerosol depend to a large extent on physicochemical properties of individual particles. Morphological features and mixing states of individual particles in the free troposphere are important to investigate aging of particles during long-range transport and its potential impacts on climate. To elucidate morphological features and chemical composition of individual particles according to their sources and weather conditions, we collected aerosol samples at the summit of Mt. Fuji (35.36°N, 138.73°E, 3776 m a.s.l) located in the free troposphere during summer in 2014 and 2015.
The aerosol samples were obtained using a cascade impactor (the 50 % cut-off diameters of the stages were 0.25 μm and 1.0 μm) on carbon-coated collodion films for 1 hour at flow rate of about 0.55 L/min. To measure the heights of individual particles, particles were coated with Pt / Pd alloy at a shadowing angle of arctan 0.5. Size and chemical composition of individual particles were analyzed using a transmission electron microscope (TEM) equipped with an energy-dispersive X-ray (EDX) analyzer. In this study, 11 samples were obtained and analyzed. The backward trajectories and the average relative humidity (RH) along the trajectories were computed using the HYSPLIT trajectory model (https://ready.arl.noaa.gov/HYSPLIT_traj.php).
In this study, the particles were classified into 9 types (Figure1) based on their morphological features (Ueda et al., 2011). Most of particles were classified as eroded, dome-like or cluster particles. In this study, particles classified as the cluster particles were included in 6 samples. The cluster particles were comprised of some units of spherical or coccoid particles. It is reported that the cluster particles are formed under low RH and rich in sulfur (Ueda. et al., 2011). In this study, however the cluster particles were formed under high RH condition. Analysis based on backward trajectories indicates that the sizes of individual particles that constituted cluster particles depend on sources and weather conditions. Therefore, the formation mechanism of cluster particles has to be investigated further.
The aerosol samples were obtained using a cascade impactor (the 50 % cut-off diameters of the stages were 0.25 μm and 1.0 μm) on carbon-coated collodion films for 1 hour at flow rate of about 0.55 L/min. To measure the heights of individual particles, particles were coated with Pt / Pd alloy at a shadowing angle of arctan 0.5. Size and chemical composition of individual particles were analyzed using a transmission electron microscope (TEM) equipped with an energy-dispersive X-ray (EDX) analyzer. In this study, 11 samples were obtained and analyzed. The backward trajectories and the average relative humidity (RH) along the trajectories were computed using the HYSPLIT trajectory model (https://ready.arl.noaa.gov/HYSPLIT_traj.php).
In this study, the particles were classified into 9 types (Figure1) based on their morphological features (Ueda et al., 2011). Most of particles were classified as eroded, dome-like or cluster particles. In this study, particles classified as the cluster particles were included in 6 samples. The cluster particles were comprised of some units of spherical or coccoid particles. It is reported that the cluster particles are formed under low RH and rich in sulfur (Ueda. et al., 2011). In this study, however the cluster particles were formed under high RH condition. Analysis based on backward trajectories indicates that the sizes of individual particles that constituted cluster particles depend on sources and weather conditions. Therefore, the formation mechanism of cluster particles has to be investigated further.