Particulate Amine Salts as Dynamic Hubs for Atmospheric Nitrogen Exchange

Here, we overturn this paradigm by demonstrating that these salts instead serve as dynamic hubs for nitrogen exchange. By using integrated ab initio calculations and high-resolution mass spectrometry, we show that dimethylamine (DMA) and trimethylamine (TMA) salts are efficiently initiated by •OH, generating reactive radical cation intermediates, which is not considered in previous organic nitrate chemistry.

Meanwhile, sulfates dramatically accelerate the subsequent oxidation process by lowering free energy barriers by orders of magnitude compared to water-mediated pathways. Quantitative branching ratios reveal a bifurcated fate for oxidized amine salts: over 47.5% yields low-volatility amides (CH₂NCHO and (CH₃)₂NCHO) that preferentially remain in the particle phase, and the remaining 52.5% produces volatile species (CH₃NH₂ and CH₃NC) that partition to the gas phase.