Enhanced ClNO$_2$ formation at the interface of sea-salt aerosol

Kavli Affiliate: David T. Limmer

| First 5 Authors: Seokjin Moon, David T. Limmer, , ,

| Summary:

The reactive uptake of $mathrm{N_2O_5}$ on sea-spray aerosol plays a key
role in regulating NO$_mathrm{x}$ concentration in the troposphere. Despite
numerous field and laboratory studies, a microscopic understanding of its
heterogeneous reactivity remains unclear. Here, we use molecular simulation and
theory to elucidate the chlorination of $mathrm{N_2O_5}$ to form ClNO$_2$, the
primary reactive channel within sea-spray aerosol. We find the formation of
ClNO$_2$ is markedly enhanced at the air-water interface due to the
stabilization of the charge-delocalized transition state, as evident from the
formulation of bimolecular rate theory in heterogeneous environments. We
explore the consequences of the enhanced interfacial reactivity in the uptake
of $mathrm{N_2O_5}$ using numerical solutions of molecular reaction-diffusion
equations as well as their analytical approximations. Our results suggest that
the current interpretation of aerosol branching ratios needs to be revisited.

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