Formation and growth of atmospheric aerosol particles from methanesulfonic acid, amines, and water
Authors
Matthew L Dawson — University of California, Irvine
Mychel E. Varner — University of California, Irvine
Veronique Michele Lucie Perraud — University of California
Michael Ezell — University of California
R. B. Gerber — University of California, Irvine
Alla Zelenyuk-Imre — Pacific Northwest National Laboratory
Barbara J Finlayson-Pitts — University of California
Category
Aerosol Properties
Description
Atmospheric aerosols impact visibility and affect human health and climate. Current climate models underestimate aerosol particles formed from the interaction of gas phase species in the atmosphere. An as-yet-unaccounted-for source of these particles is from methane sulfonic acid (CH3SO3H, MSA) and amines. MSA is an atmospheric oxidation product of a variety of organosulfur compounds, which are emitted in large quantities, particularly from the ocean. Amines have a variety of both biogenic and anthropogenic sources and have been shown to play an important role in particle formation with other gas-phase acids, particularly sulfuric acid. While nucleation from sulfuric acid accounts for the bulk of new particles formed in the atmosphere, particles formed from MSA and amines may help close the gap between measured and modeled atmospheric aerosols. Here we report results from laboratory studies of particle formation from the gas phase reactions of MSA with several amines. Experiments were performed in a unique, slow-flow, large-volume aerosol flow-tube reactor at 295 K and 1 atm, under conditions of varying relative humidity. Further experiments exploring the composition of particles formed from this source are underway using the SPLAT-II mass spectrometer. Experimental results are compared to an ab initio model describing cluster formation between MSA and the amines. The results of this comparison indicate an important role for water in the gas phase reaction of MSA and the amines to form particles. Atmospheric implications from this new source of particles are discussed.
