Role of oleic acid coating in the heterogeneous uptake of dimethylamine by ammonium sulfate particles

Reactive uptake by ammonium (NH4 +) salts is one of the major pathways for the gas-to-particle partitioning of alkyl amines. Recent studies using particles of individual ammonium salts and mixtures with hydrophilic organics have revealed that the degree of amine uptake depends on the phase state of ammonium salts, the particulate water contents and particle viscosity. The role of hydrophobic organic compounds, another important category of particulate organics commonly detected in the ambient atmosphere, in amine uptake remains unknown. Here we report the uptake of dimethylamine (DMA) by ammonium sulfate (AS) particles coated with fresh or ozone-aged bulk oleic acid (OA) at 60%, 30%, and