Multiphase Chemistry in the Atmosphere

Earth’s atmosphere comprises a complex mix of gas and condensed phases, where condensed phases facilitate multiphase chemical reactions that would not occur in the gas phase alone. These reactions drive dynamic physical and chemical processes across various spatial and temporal scales, playing a crucial role in the cycling of atmospheric trace constituents. Multiphase chemistry significantly influences geochemical cycles, human health, and climate. This review focuses on the chemical steps governing the cycling of important species, such as halogens, reactive nitrogen, and organics, within aerosol particles, a key type of atmospheric condensed phases, and at condensed phase–air interfaces. These interfaces include mineral oxides, ice, and aqueous solutions found in particulate matter, clouds, snow, and on oceanic and terrestrial surfaces. This review also discusses the important role of redox chemical cycling, the hydrogen bonding network and water activity in these processes.