Characteristics and mixing state of aerosol at the summit of Mount Tai (1534 m) in Central East China: First measurements with SPAMS

Abstract The size-resolved chemical composition and mixing state of single particles were observed by using single particle aerosol mass spectrometry (SPAMS) from May 12 to June 8, 2017. A total of 979,899 particles were successfully ionized to identify 6 main particle groups including carbon-rich particles (47.66%), K-rich particles (28.78%), heavy-metal particles (10.12%), sodium particles (8.86%), dust particles (3.89%), and ammonium particles (0.67%). The wind direction and speed had large impacts on the proportion of carbonaceous aerosol particles and had little influence on heavy-metal particles. The relative humidity (RH) had great impacts on the chemical components of aerosol particles. The proportion of secondary particles increased, while the primary particles diminished as RH increased. The proportion of carbon-rich particles decreased with increasing particle size. However, the size distributions varied significantly for different types of carbonaceous particles. Sodium particles and heavy-metal particles were mainly concentrated at sizes larger than 1 μm. K-rich particles had a maximum proportion at 0.5–1.0 μm. The number fraction of ammonium particles predominated chiefly at 0.6–2.0 μm. It has been found that aerosol particles, mainly from burning processes, were mixed with 36 [C 3 ] + to different degrees at Mt. Tai. A high proportion of ammonium particles were mixed with organics and elemental carbon (OCEC), elemental carbon-sulfate (EC-sulfate), and elemental carbon-secondary (EC-secondary) particles, while few of these particles were mixed with EC-nitrate particles, which indicated that the ammonia in the air was inclined to combine with organic species and sulfate. A higher proportion of atmospheric particles mixed with nitrate were observed compared to those mixed with sulfate.