Sea spray aerosol (SSA) ejected through bursting bubbles
at the
ocean surface is a complex mixture of salts and organic species. Submicrometer
SSA particles have long atmospheric lifetimes and play a critical
role in the climate system. Composition impacts their ability to form
marine clouds, yet their cloud-forming potential is difficult to study
due to their small size. Here, we use large-scale molecular dynamics
(MD) simulations as a “computational microscope” to
provide never-before-seen views of 40 nm model aerosol particles and
their molecular morphologies. We investigate how increasing chemical
complexity impacts the distribution of organic material throughout
individual particles for a range of organic constituents with varying
chemical properties. Our simulations show that common organic marine
surfactants 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 SSA surface heterogeneity with Brewster angle microscopy
on model interfaces. These observations indicate that increased chemical
complexity in submicrometer SSA leads to a reduced surface coverage
by marine organics, which may facilitate water uptake in the atmosphere.
Our work thus establishes large-scale MD simulations as a novel technique
for interrogating aerosols at the single-particle level.