Revealing the Impacts of Chemical Complexity on Submicron Sea Spray Aerosol Morphology

Sea spray aerosol (SSA) ejected through bursting bubbles at the ocean surface are complex mixtures of salts and organic species. Composition affects their ability to form marine clouds which cover nearly three-quarters of the Earth and play a critical role in the climate system. Submicron SSA particles have long lifetimes in the atmosphere and impact the Earths climate, yet their cloud-forming potential is difficult to study at the single-particle level using conventional experimental techniques due to their small size. Here, we use large-scale molecular dynamics (MD) simulations as a computational microscope to provide never-before-seen, dynamical views of 40-nm model aerosol particles and their detailed molecular morphologies. We investigate how increasing chemical complexity impacts the distribution and partitioning of organic material throughout individual particles for a range of organic constituents with varying chemical properties. Our simulations show that organic surfactants commonly found in SSA readily partition between both the surface and interior of the aerosol, indicating that nascent SSA may be more heterogeneous than traditional morphological models suggest. We support our computational observations of heterogeneity at the SSA surface with Brewster angle microscopy on model interfaces. Ultimately, our work establishes large-scale MD simulations as a novel technique for interrogating aerosols at the single-particle level, and shows the morphological mechanisms underlying why submicron SSA readily absorb waterand thus have a higher cloud forming potentialthan would otherwise be predicted for organic-rich aerosols.