Trace Amines Scavenge Terpenoid-Derived Criegee Intermediates at Air–Liquid Interfaces to Form Atmospheric Organic Nitrogen

Abstract Organic nitrogen (ON) represents a chemically diverse fraction of atmospheric aerosols that profoundly modulates particle aging, toxicity, and light absorption. However, the exact kinetic pathways and timing of interfacial ON formation remain poorly constrained. Utilizing surface-sensitive mass spectrometry, we experimentally demonstrate that ambient, trace-level amines (5–40 ppt) can efficiently scavenge terpenoid-derived stabilized Criegee intermediates (SCIs) at the air–liquid boundary, successfully outcompeting interfacial hydration. Crucially, we elucidate a complete kinetic hierarchy for ON evolution across three sequential generations: SCIs, α-hydroxyalkyl-hydroperoxides (α-HH), and functionalized aldehydes all react with amines to converge on identical ON products. The reaction rates follow the strict order of SCI > α-HH > functionalized aldehyde, bypassing conventional bulk-phase carbonyl condensation via rapid nucleophilic attack and spontaneous H2O2 elimination. Rather than predicting global yields, our data explicitly identify a rapid, nonphotolytic entry point for ON formation that current condensed-phase schemes miss. Incorporating this bounded SCI–amine pathway into future multiphase mechanisms will significantly improve parametrizations of aerosol nitrogen chemical aging and ON-linked light absorption.