An improved multiphase chemistry mechanism for methylamines: significant dimethylamine cloud production

Monomethylamine (MMA), dimethylamine (DMA), and trimethylamine (TMA) are important compounds for atmospheric key processes, e.g., new particle formation (NPF). A description of their multiphase chemical processing within atmospheric models is incomplete, but mandatory to describe their atmospheric budgets. In this study, a detailed multiphase chemistry mechanism was developed and first process model investigations were performed. The simulations focused on pristine marine conditions, where open research questions exist regarding ambient gas-phase concentrations of methylamines, particularly with regards to unexpectedly high DMA levels. The simulations reveal that TMA oxidation in cloud droplets results into DMA formation with a yield of around 87%, a missing DMA production pathway in current models. Also, it is demonstrated that about 21% and 69% of the respective DMA and TMA gas-phase oxidation proceed via autoxidation yielding HOOCH 2 NHCHO and HOOCH 2 N(CHO)CH 2 OOH, respectively. The discussed processes should be included into atmospheric models for advanced predictions of NPF and climate impacts.