Articles | Volume 14, issue 22
Atmos. Chem. Phys., 14, 12455–12464, 2014
https://doi.org/10.5194/acp-14-12455-2014
Atmos. Chem. Phys., 14, 12455–12464, 2014
https://doi.org/10.5194/acp-14-12455-2014

Research article 27 Nov 2014

Research article | 27 Nov 2014

Modeling of gaseous methylamines in the global atmosphere: impacts of oxidation and aerosol uptake

F. Yu and G. Luo F. Yu and G. Luo
  • Atmospheric Sciences Research Center, State University of New York, 251 Fuller Road, Albany, New York 12203, USA

Abstract. Gaseous amines have attracted increasing attention due to their potential role in enhancing particle nucleation and growth and affecting secondary organic aerosol formation. Here we study with a chemistry transport model the global distributions of the most common and abundant amines in the air: monomethylamine (MMA), dimethylamine (DMA), and trimethylamine (TMA). We show that gas phase oxidation and aerosol uptakes are dominant sinks for these methylamines. The oxidation alone (i.e., no aerosol uptake) leads to methylamine lifetimes of 5–10 h in most parts of low and middle latitude regions. The uptake by secondary species with uptake coefficient (γ) of 0.03 (corresponding to the uptake by sulfuric acid particles) reduces the lifetime by ~30% over oceans and much more over the major continents, resulting in a methylamine lifetime of less than 1–2 h over central Europe, eastern Asia, and eastern US. With the estimated global emission flux, from the literature, our simulations indicate that [DMA] in the model surface layer over major continents is generally in the range of 0.1–2 ppt (parts per trillion) when γ = 0.03 and 0.2–10 ppt when γ = 0, and decreases quickly with altitude. [DMA] over oceans is below 0.05 ppt and over polar regions it is below 0.01 ppt. The simulated [MMA] is about a factor of ~2.5 higher while [TMA] is a factor of ~8 higher than [DMA]. The modeled concentrations of methylamines are substantially lower than the limited observed values available, with normalized mean bias ranging from −57 (γ = 0) to −88% (γ = 0.03) for MMA and TMA, and from −78 (γ = 0) to −93% (γ = 0.03) for DMA.

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Short summary
Global lifetimes and concentrations of gaseous methylamines (MMA, DMA, and TMA) have been simulated. Oxidation and aerosol uptakes are dominant sinks for these methylamines. The oxidation alone leads to their lifetimes of 5-10h in most parts of low and middle latitude regions. The uptake by secondary species can shorten their lifetime to as low as 1-2h over central Europe, eastern Asia, and the eastern US. The modeled concentrations are substantially lower than observed values available.
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