NH₃ Converts Criegee Intermediates to Nitrogenous Organics

Abstract. Ammonia (NH₃), the dominant alkaline gas in the atmosphere, plays a critical role in urban air quality, but its molecular-level interactions with organics remain poorly understood. Here, we uncover a hidden chemical pathway: NH₃ efficiently scavenges stable Criegee intermediates (SCI) – critical radical in organic aerosol formation. Using high-resolution Orbitrap mass spectrometry, we capture the first real-time evidence of NH₃ reacting with styrene-derived C₇-SCI to form a hazardous peroxide amine (C₇H₉O₂N) while suppressing traditional SCI-driven aerosol components like benzoic acid and oligomers. Due to unstable bond of peroxide in the molecule, C₇H₉O₂N can further decompose into more stable compounds (imine C₇H₇N and amide C₇H₇ON). This study discovered a critical reaction pathway for the formation of organic amines through the reaction of NH₃ and SCI, which not only bridges a critical gap in understanding NH₃’s role in aerosol chemistry but also exposes a previously overlooked health risk from nitrogen-enriched particulate matter.