Properties of Seawater Surfactants Associated with Primary Marine Aerosol Particles Produced by Bursting Bubbles at a Model Air-Sea Interface

Surfactants account for minor fractions of total organic carbon in the ocean but can significantly influence the production of primary marine aerosol particles (PMA) at the sea surface via modulation of bubble surface tension. During September and October 2016, model PMA (mPMA) were produced from seawater by bursting bubbles at two biologically productive and two oligotrophic stations in the western North Atlantic Ocean. Total concentrations of surfactants extracted from mPMA and seawater were quantified and characterized via measurements of surface tension isotherms and critical micelle concentrations (CMCs). Surfactant CMCs in biologically productive seawater were lower than those in the oligotrophic seawater suggesting that surfactant mixtures in the two regions were chemically distinct. mPMA surfactants were enriched in all regions relative to those in the associated seawater. Surface tension isotherms indicate that mPMA surfactants were weaker than corresponding seawater surfactants. mPMA from biologically productive seawater contained higher concentrations of surfactants than those produced from oligotrophic seawater, supporting the hypothesis that seawater surfactant properties modulate mPMA surfactant concentrations. Diel variability in concentrations of seawater and mPMA surfactants in some regions is consistent with biological and/or photochemical processing. This work demonstrates direct links between surfactants in mPMA and those in the associated seawater.