Aerosol soluble proteins in Asian dust in southwestern Japan

Aerosol proteins, as core biological components of bioaerosols, are garnering increasing attention due to their environmental significance, including their roles in atmospheric processes and associated health risks. However, observational data on the proteins are very limited, leaving their distribution and variation in the atmosphere poorly understood. To investigate the long-distance transport of proteins with Asian dust in the Northern Hemisphere middle latitude westerlies to remote downwind areas, we quantified the soluble proteins in aerosol particles, referred to as aerosol soluble proteins (ASPs), collected in the coastal city of Kumamoto, Japan, during the spring of 2023, when three dust events occurred. The concentration of ASPs ranged from 0.22 to 1.68 μg m^-3, with an average concentration of 0.73 ± 0.36 μg m^-3 under dust conditions and 0.31 ± 0.05 μg m^-3 under non-dust conditions. During the dust periods, the largest concentration of ASPs (1.68 μg m^-3) coincided with the peak concentration of suspended particulate matter, and the concentration strongly correlated with the mass concentration of particles larger than 2.5 μm, indicating a close dependence of ASPs on dust particles. Primary estimations indicated a dry deposition flux of ASPs at approximately 1.10 ± 0.87 mg m^-2 d^-1 under the dust conditions. These results prove that Asian dust efficiently transports proteins, facilitating their dispersion in the atmosphere.