Ozonolysis of Trimethylamine Exchanged with Typical Ammonium Salts in the Particle Phase

Alkylamines contribute to both new particle formation and brown carbon. The toxicity of particle-phase amines is of great concern in the atmospheric chemistry community. Degradation of particulate amines may lead to secondary products in the particle phase, which are associated with changes in the adverse health impacts of aerosols. In this study, O₃ oxidation of particulate trimethylamine (TMA) formed via heterogeneous uptake of TMA by (NH₄)₂SO₄, NH₄HSO₄, NH₄NO₃ and NH₄Cl, was investigated with in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and proton transfer reaction mass spectrometry (PTR-MS). HCOOH, HCHO, CH₃N═CH₂, (CH₃)₂NCHO, CH₃NO₂, CH₃N(OH)CHO, CH₃NHOH and H₂O were identified as products on all the substrates based upon IR (one-dimensional IR and two-dimensional correlation infrared spectroscopy), quantum chemical calculation and PTR-MS results. A reaction mechanism was proposed to explain the observed products. This work demonstrates that oxidation might be a degradation pathway of particulate amines in the atmosphere. This will aid in understanding the fate of particulate amines formed by nucleation and heterogeneous uptake and their potential health impacts during atmospheric aging.