Ozonolysis of oleic acid adsorbed to polar and nonpolar aerosol particles.
Single-particle kinetic studies of the reaction between oleic acid and O 3 have been conducted on two different types of core particles: polystyrene latex (PSL) and silica. Oleic acid was found to adsorb to both particle types in multilayer islands that resulted in an adsorbed layer of a total volume estimated to be less than one monolayer. The rate of the surface reaction between surface-adsorbed oleic acid and O 3 has been shown for the first time to be influenced by the composition of the aerosol substrate in a mixed organic/inorganic particle. A Langmuir-Hinshelwood mechanism was applied to the observed dependence of the pseudo-first-order rate constant with [O 3], and the resulting fit parameters for the ozone partition coefficient ( K O 3 ) and maximum first order rate constant ( k 1,max ) suggest that the reaction proceeded faster on the less polar PSL core at lower [O 3] due to the increased residence time of O 3 on the PSL surface, but the reaction was ultimately more efficient on the silica surface at high [O 3]. Values for the uptake coefficient, gamma oleic , for reaction of oleic acid on PSL spheres decrease from 2.5 x 10 (-5) to 1 x 10 (-5) with increasing [O 3] from 4 to 25 ppm and overlap at high [O 3] with the estimated values for gamma oleic on silica, which decrease from 1.6 x 10 (-5) to 1.3 x 10 (-5). The relationship between gamma oleic and the more common expression for gamma O 3 is discussed.
Rosen
Elias P
EP
Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, USA.
Garland
Eva R
ER
Baer
Tomas
T
D000327:Adsorption; D000336:Aerosols / Q000737:chemistry*; D007700:Kinetics; D018625:Microscopy, Atomic Force / Q000295:instrumentation / Q000379:methods; D008855:Microscopy, Electron, Scanning / Q000295:instrumentation / Q000379:methods; D019301:Oleic Acid / Q000737:chemistry*; D010126:Ozone / Q000737:chemistry*; D010316:Particle Size; D011137:Polystyrenes / Q000737:chemistry; D012680:Sensitivity and Specificity; D012822:Silicon Dioxide / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation / Q000379:methods; D013499:Surface Properties
D000336:Aerosols; D011137:Polystyrenes; D019301:Oleic Acid; D010126:Ozone; D012822:Silicon Dioxide; C024075:styrofoam