Aging Process of Sea Salt Particles Driven by Glyoxal: Implications for Climate Effects

Atmospheric sea spray aerosol (SSA) undergoes chemical aging during long-distance transport, leading to significant alterations in its climate effects. However, the aging mechanisms of SSA driven by oxygenated volatile organic compounds (OVOCs) remain unclear. Hence, the aging processes of NaCl particles driven by glyoxal (GL), a representative OVOC, are systematically investigated using molecular dynamics (MD) simulations and density functional theory (DFT) calculations. MD simulations with high GL coverage show that GL readily mixes with NaCl and preferentially orients its carbonyl groups toward the NaCl surface. The adsorption of GL on the NaCl surface is dominated by the interaction between the O atom of GL (OGL) and the Na atom of the surface. DFT calculations with single GL coverage further reveal the formation of the OGL–Na bond between GL and NaCl. The mixing process of GL and NaCl is regulated by both the number of aldehyde groups engaging in the interfacial coordination and the corresponding lengths of OGL–Na bonds. The subsequent heterogeneous oxidation of GL by an OH radical proceeds mainly via a barrierless H-abstraction pathway to form HC(O)CO radicals, which may further react with methylamine/ammonia and contribute to brown carbon formation. Our results reveal the importance of incorporating such aging mechanisms into atmospheric models to improve climate predictions.