Atmospheric Sulfuric Acid‐Dimethylamine Nucleation Enhanced by Trifluoroacetic Acid
Yiqun Lu, Ling Liu, Ning An, Gan Yang, Yiliang Liu, Theo Kurtén, Hanna Vehkamäki, Xiuhui Zhang, Lin Wang
Abstract
Abstract Sulfuric acid (SA)‐dimethylamine (DMA)‐H 2 O cluster formation has been proven to be responsible for a significant part of new particle formation (NPF) in a Chinese megacity. However, the possible involvement of common atmospheric acids in the subsequent growth of SA‐DMA clusters remains elusive. We simulated formation and growth of clusters using atmospheric relevant concentrations of SA, DMA, and trifluoroacetic acid (TFA), a commonly observed atmospheric perfluorocarboxylic acid, using Density Functional Theory combined with Atmospheric Cluster Dynamics Code. The presence of TFA leads to complex cluster formation routes and an enhancement of NPF rates by up to 2.3 ([TFA] = 5.0 × 10 6 molecules cm −3 , [SA] = 1.0 × 10 6 molecules cm −3 , and [DMA] = 1.5 × 10 9 molecules cm −3 ). The agreement of (SA) 1 ·(DMA) 1‐2 ·(TFA) 1 concentrations between simulations and ambient measurements during NPF events validates model predictions and implies that perfluorocarboxylic acids could potentially boost atmospheric SA‐DMA NPF rates.