Amplified Trace Gas Removal in the Troposphere

TLDR

Tropospheric pollutants and trace gases are largely controlled by reactions with the short‑lived hydroxyl radical (OH), whose regeneration pathways were previously considered well understood. The study reports a previously unrecognized pathway that accelerates OH regeneration without generating ozone, evidenced by unusually high OH concentrations in the Pearl River Delta despite low ozone levels.

Abstract

Going Faster The concentrations of most tropospheric pollutants and trace gases are kept in check by their reactions with hydroxyl radicals (OH). OH is a short-lived, highly reactive species that is produced in the atmosphere by photochemical processes, and regenerated in the chain of chemical reactions that follows the oxidative destruction of those molecules. These regeneration mechanisms were thought to be fairly well understood, but now Hofzumahaus et al. (p. 1702 , published online 4 June) present evidence of a pathway not previously recognized. In a study of atmospheric composition in the Pearl River Delta, a highly polluted region of China, greatly elevated OH concentrations were observed without the correspondingly high levels of ozone expected from current models. Thus, OH concentrations may be augmented by a process that speeds the regeneration of OH without producing ozone.