Marine aerosol size distributions in the springtime over China adjacent seas

Size distributions and particle number concentrations of atmospheric aerosols in the size (diameter) range from 15 nm to 10μm were measured on board of a research ship during three cruises in China adjacent seas. The total particle number concentrations were in average around 4000cm-3 in Yellow Sea, 2000cm-3 in East China Sea and 1000cm-3 in South China Sea. The observed size distributions were fitted with two or three log-normal modes and the data were classified according to time, regions and calculated air mass back-trajectories. The size distribution spectra of air masses of polluted continental origin as their back-trajectories showed were characterized by single mode with total number concentrations between 1000 and 10000cm-3. The size distributions in marine air masses showed dual mode characteristics, one maximum at 40–60 nm and the other at 160–190 nm with total number concentrations below 1000cm-3. This type of dual mode was more pronounced at longer residence time of the air masses over the ocean. The burst of ultra-fine (UF) particles and the consequent growth processes were observed twice in Yellow Sea and possible reasons leading to these events are discussed. The particle growth rate (GR) was 3.4±0.93.4±0.9 and 3.5±1.6nmh-1, respectively (95% confidence interval), indicating that the UF particles can grow to cloud condensation nuclei (CCN) within the next 1–2 days.