title: New Particle Formation from Methanesulfonic Acid and Amines/Ammonia as a Function of Temperature.
abstract: Previous studies have shown that methanesulfonic acid (MSA) reacts with amines and ammonia to form particles, which is expected to be particularly important in coastal and agricultural areas. We present the first systematic study of temperature dependence of particle formation from the reactions of MSA with trimethylamine (TMA), dimethylamine (DMA), methylamine (MA), and ammonia over the range of 21-28 °C and 0.4-5.9 s in a flow reactor under dry conditions and in the presence of 3 × 1017cm-3water vapor. Overall activation energies (Eoverall) for particle formation calculated from the dependence of rates of particle formation on temperature for all of these bases are negative. The negative Eoverallis interpreted in terms of reverse reactions that decompose intermediate clusters in competition with the forward reactions that grow the clusters into particles. The average values of Eoverallfor the formation of detectable particles are: TMA, -(168 ± 19) kcal mol-1; DMA, -(134 ± 30) kcal mol-1; MA, -(68 ± 23) kcal mol-1; NH3, -(110 ± 16) kcal mol-1(±1σ). The strong inverse dependence of particle formation with temperature suggests that particle formation may not decline proportionally with concentrations of MSA and amines if temperature also decreases, for example at higher altitudes or in winter.
authors.affiliation: Department of Chemistry, University of California, Irvine , Irvine, California 92697, United States.
authors.forename: Haihan
authors.initials: H
authors.lastname: Chen
authors.affiliation: Department of Chemistry, University of California, Irvine , Irvine, California 92697, United States.
authors.forename: Barbara J
authors.identifier: 0000-0003-4650-168X
authors.initials: BJ
authors.lastname: Finlayson-Pitts
mesh_terms: D000588:Amines; D000641:Ammonia; D013696:Temperature
chemical_list: D000588:Amines; D000641:Ammonia