重一 山本

Significant impacts of heterogeneous reaction on the chemico-physical properties of dust particles during severe dust events over East Asia in 2015

Heterogeneous processes play an important role in changing the chemical, physical, optical, and radiative characters of dust particles at regional and global scales, especially in East Asia, where both the emissions of mineral dust and anthropogenic pollutants are huge. To investigate the chemical and physical impacts of heterogeneous reactions on dust particles, three dust and/or air pollution episodes were observed and simulated in Beijing, China and Fukuoka, Japan during 27 March and 2 April, 2015. The results confirmed that heterogeneous reactions were the major mechanisms producing coarse mode nitrate and sulfate in the presence of dust particles, with the concentrations of coarse mode nitrate reaching 19 μg/m in Beijing and 4 μg/m in Fukuoka. We also found that heterogeneous processes and subsequent hygroscopic growth significantly changed the mixing state and size of dust particles. As a result of the internal mixing of nitrate, sulfate, and aerosol liquid water, the volume concentration of dust doubled when the relative humidity (RH) was relatively high (> 80%), and the dust particles tended to be spherical when the volume fraction of dust coatings reached 20%.