Recent evidence has suggested that heterogeneous chemistry of oxygenated hydrocarbons, primarily carbonyls, plays a role in the formation of secondary organic aerosol (SOA); however, evidence is emerging that direct uptake of alkenes on acidic aerosols does occur and can contribute to SOA formation. In the present study, significant uptake of monoterpenes, oxygenated monoterpenes and sesquiterpenes to acidic sulfate aerosols is found under various conditions in a reaction chamber. Proton transfer mass spectrometry is used to quantify the organic gases, while an aerosol mass spectrometer is used to quantify the organic mass uptake and obtain structural information for heterogeneous products. Aerosol mass spectra are consistent with several mechanisms including acid catalyzed olefin hydration, cationic polymerization and organic ether formation, while measurable decreases in the sulfate mass on a per particle basis suggest that the formation of organosulfate compounds is also likely. A portion of the heterogeneous reactions appears to be reversible, consistent with reversible olefin hydration reactions. A slow increase in the organic mass after a fast initial uptake is attributed to irreversible reactions, consistent with polymerization and organosulfate formation. Uptake coefficients (gamma) were estimated for a fast initial uptake governed by the mass accommodation coefficient (alpha) and ranged from 1 x 10(-6)-2.5 x 10(-2). Uptake coefficients for a subsequent slower reactive uptake ranged from 1 x 10(-7)-1 x 10(-4). These processes may potentially lead to a considerable amount of SOA from the various biogenic hydrocarbons under acidic conditions, which can be highly significant for freshly nucleated aerosols, particularly given the large array of atmospheric olefins.
In this paper, we propose a parallel Schwarz generalized eigen-oscillation spectral element method (GeSEM) for 2-D complex Helmholtz equations in high frequency wave scattering in dispersive inhomogeneous media. This method is based on the spectral expansion of complex generalized eigen-oscillations for the electromagnetic fields and the Schwarz non-overlapping domain decomposition iteration method. The GeSEM takes advantages of a special real orthogonality property of the complex eigen-oscillations and a new radiation interface condition for the system of equations for the spectral expansion coefficients. Numerical results validate the high resolution and the flexibility of the method for various materials.