GROWTH-BEHAVIOR OF THE MARINE SUBMICRON BOUNDARY-LAYER AEROSOL

A box model for investigating the chemistry and growth of submicron pa rticles in the marine boundary layer was developed. Processes simulate d by the model were gas phase chemistry, in-cloud sulfate production, gas-to-particle transfer of condensable vapors, coagulation, dry depos ition of particles and gases, and entrainment between the boundary lay er and the free troposphere. According to model simulations, the most influential factor for the growth of nuclei and Aitken mode particles is the production rate of methane sulfonic acid (MSA) and other low-vo latility compounds in the gas phase. Processes controlling SO2 concent rations dictate the amount of non-sea-salt sulfate produced in the bou ndary layer but are less important for particle growth. The ratio of M SA to non-sea-salt sulfate in the particulate phase may vary largely, even when a constant MSA yield from dimethylsulfide (DMS) oxidation is assumed. Clouds decrease nuclei lifetime but do not affect their grow th significantly, unless the time between two cloud passages is very s hort. Sources other than DMS may produce condensable vapors that assis t particle growth to some extent. With our current knowledge of the co ncentrations of condensible matter in the marine boundary layer, howev er, it seems unlikely that small nuclei are able to grow into cloud co ndensation nuclei size over their lifetime. More information is needed on heterogeneous surface reactions that may occur between submicron p articles and vapors such as SO2, as well as on potential transport lim itations between condensable vapors and particles caused by thermodyna mics or organic surfactants.