Formation of extremely low-volatility organic compounds from styrene ozonolysis: Implication for nucleation

Abstract

Styrene is a highly reactive compound with the dual nature of aromatics and olefins. This work presents evidence for formation of extremely low-volatility organic compounds (ELVOCs) from styrene ozonolysis. The molecules of ELVOCs were analyzed using a high-resolution orbitrap mass spectrometer. The results show that ELVOCs were oligomers characterized by stabilized Criegee radicals (SCIs) as chain units. The addition of C₆H₅CHOO (SCI1) or CH₂OO (SCI2) can dramatically decrease the oligomers' volatility. At low relative humidity (RH), ELVOCs are mainly formed from the reaction of RO₂ radical, C₆H₅OO·, with SCI1 and SCI2; however, ELVOCs are primarily produced by the reaction between benzoic acid and SCI1 at high RH. Ambient particles were also collected to propose the probable oligomers from styrene-SCI. Our results suggest that styrene-SCI derived ELVOCs may act as nucleating agents, potentially providing an experimental basis for nucleation events that frequently occur in urban areas.

Keywords: Criegee radical; Nucleation; Oligomers; Relative humidity; Styrene.