title: A new approach to determining gas-particle reaction probabilities and application to the heterogeneous reaction of deliquesced sodium chloride particles with gas-phase hydroxyl radicals.
abstract: The reaction kinetics for gaseous hydroxyl radicals (OH) with deliquesced sodium chloride particles (NaCl(aq)) were investigated using a novel experimental approach. The technique utilizes the exposure of substrate-deposited aerosol particles to reactive gases followed by chemical analysis of the particles using computer-controlled scanning electron microscopy with energy-dispersive analysis of X-rays (CCSEM/EDX) capability. Experiments were performed at room temperature and atmospheric pressure with deliquesced NaCl particles in the micron size range at 70-80% RH and with OH concentrations in the range of 1 to 7 x 10(9) cm(-3). The apparent, pseudo first-order rate constant for the reaction was determined from measurements of changes in the chloride concentration of individual particles upon reaction with OH as a function of the particle loading on the substrate. Quantitative treatment of the data using a model that incorporates both diffusion and reaction kinetics yields a lower limit to the net reaction probability of gamma(net) > or = 0.1, with an overall uncertainty of a factor of 2.
authors.affiliation: W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, USA. Alexander.Laskin@pnl.gov
authors.forename: Alexander
authors.initials: A
authors.lastname: Laskin
authors.forename: Hai
authors.initials: H
authors.lastname: Wang
authors.forename: William H
authors.initials: WH
authors.lastname: Robertson
authors.forename: James P
authors.initials: JP
authors.lastname: Cowin
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ezell
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Finlayson-Pitts