The conversion of gaseous isoprene (Iso g) into secondary organic aerosol is a major tropospheric process that affects air quality and the Earth's radiative balance. Herein we report that Iso g is protonated upon collision with mildly acidic water (1 < pH < 4) thereby initiating the formation of oligomers in the condensed phase. The identical dependences of IsoH +, (Iso) 2H + and (Iso) 3H + on pH, and the linear and quadratic dependences of (Iso) 2H +/IsoH + and (Iso) 3H +/IsoH + on Iso g, respectively, imply that the oligomerization process is propagated by reactions of Iso g with interfacial cationic carriers (Iso) iH +. Decreasing IsoH +/IsoD + > (Iso) 2H +/(Iso) 2D + > (Iso) 3H +/(Iso) 3D + ratios in solvent deuteration experiments are consistent with direct and inverse kinetic isotope effect for initiation (protonation) and propagation steps, respectively. These experiments show that atmospheric isoprene, and possibly other biogenic unsaturate gases, will readily polymerize on weakly acidic aerosols, fogs and clouds.
|Original language||English (US)|
|Journal||ACS National Meeting Book of Abstracts|
|State||Published - 2011|
ASJC Scopus subject areas
- Chemical Engineering(all)