A simplified description of the evolution of organic aerosol composition in the atmosphere

TLDR

Organic aerosol is composed of many species from direct emissions or reactions, making explicit chemical characterization difficult. Across laboratory and field environments, bulk OA occupies a narrow Van Krevelen line (H:C vs O:C) with slope ≈ –1, and atmospheric aging processes shift aerosols along this line toward greater oxidation, informing model representation.

Abstract

Organic aerosol (OA) in the atmosphere consists of a multitude of organic species which are either directly emitted or the products of a variety of chemical reactions. This complexity challenges our ability to explicitly characterize the chemical composition of these particles. We find that the bulk composition of OA from a variety of environments (laboratory and field) occupies a narrow range in the space of a Van Krevelen diagram (H:C versus O:C), characterized by a slope of ∼−1. The data show that atmospheric aging, involving processes such as volatilization, oxidation, mixing of air masses or condensation of further products, is consistent with movement along this line, producing a more oxidized aerosol. This finding has implications for our understanding of the evolution of atmospheric OA and representation of these processes in models.