Abstract. Dicarboxylic acids are believed to stabilize pre-nucleation clusters and facilitate new particle formation in the atmosphere, but the detailed mechanism leading to the formation of multi-component critical nucleus involving organic acids, sulfuric acid (SA), base species, and water remains unclear. In this study, theoretical caculations are performed to elucidate the interactions between succinic acid (SUA) and clusters consisting of SA-ammonia (AM)/dimethylamine (DMA) in the presence of hydration of up to six water molecules. Formation of the hydrated SUA·SA·base clusters by adding one SUA molecule to the SA·base hydrates is energetically favorable. The addition of SUA to the SA·base hydrates either triggers proton transfer from SA to the base molecule, resulting in formation of new covalent bonds, or strengthens the pre-existing covalent bonds. The presence of SUA promotes hydration of the SA·AM and SA·AM·DMA clusters but dehydration of the SA·DMA clusters. At equilibrium, the uptake of SUA competes with the uptake of the second SA molecule to stabilize the SA·base clusters at atmospherically relevant concentrations. The clusters containing both the base and organic acid are capable of further binding with acid molecules to promote their subsequent growth. Our results indicate that the multi-component nucleation involving organic acids, sulfuric acid, and base species promotes new particle formation in the atmosphere, particularly under polluted conditions.
Mixed Ligand Complexes of Alkali Metal Salts of Some Organic Acids with O-Hydroxyacetophenone Phenylhydrazone ?2, 4 ? Dinitrophenyl Hydrazone