The Hygroscopic Behavior of Partially Volatilized Coastal Marine Aerosols Using the Volatilization and Humidification Tandem Differential Mobility Analyzer Technique

Coastal marine nucleation, Aitken and accumulation mode aerosol particles with back trajectories indicative of marine origin were examined using a Volatilization and Humidification Tandem Differential Mobility Analyzer (VH-TDMA) to reveal the volatilization temperatures of the various component species. The diameter hygroscopic growth factors of the residue particles were continually examined throughout the volatilization process. In each of the three modes the dominant particle type appeared to be composed of the same four physicochemically distinct species though in different ratios. These species exhibited volatility and hygroscopic behavior consistent with combinations of a volatile organic species, sulfuric acid, ammonium sulfate or bisulfate, iodine oxide and an insoluble non-volatile residue. The Aitken and Accumulation mode aerosols contain large fractions of the insoluble, volatile, organic like material, and the volatilization of this species results in a distinct increase in the water volume uptake of the particles. Of the four distinct species only the sulfuric acid like species constituted an increasing volume fraction with decreasing particle size. This finding indicates that nucleation mode particles constitute an acidic seed and as such would undergo acid catalyzed secondary organic aerosol growth at a faster rate. The lack of a non-volatile hygroscopic residue consistent with sea salt in these particles implies that the aerosolization of seawater is not the dominant production mechanism for these submicrometer coastal marine aerosols