Hydroxyl radical-induced formation of highly oxidized organic compounds

TLDR

Secondary organic aerosol formation is a key atmospheric process affecting Earth’s radiation budget, health, and ecosystems, yet daytime hydroxyl radical reactions have traditionally been viewed as less important. The study aims to measure hydroxyl radical reactions with α‑ and β‑pinene. The authors used improved mass spectrometric methods to analyze these reactions. The study demonstrates that hydroxyl radical reactions with pinene produce highly oxidized products at higher yields than previously reported, corroborated by laboratory and field data, thereby improving the understanding of diurnal secondary organic aerosol formation.

Abstract

Abstract Explaining the formation of secondary organic aerosol is an intriguing question in atmospheric sciences because of its importance for Earth’s radiation budget and the associated effects on health and ecosystems. A breakthrough was recently achieved in the understanding of secondary organic aerosol formation from ozone reactions of biogenic emissions by the rapid formation of highly oxidized multifunctional organic compounds via autoxidation. However, the important daytime hydroxyl radical reactions have been considered to be less important in this process. Here we report measurements on the reaction of hydroxyl radicals with α- and β-pinene applying improved mass spectrometric methods. Our laboratory results prove that the formation of highly oxidized products from hydroxyl radical reactions proceeds with considerably higher yields than previously reported. Field measurements support these findings. Our results allow for a better description of the diurnal behaviour of the highly oxidized product formation and subsequent secondary organic aerosol formation in the atmosphere.