@article {1439, title = {Does atmospheric processing of saturated hydrocarbon surfaces by NO3 lead to volatilization?}, journal = {Geophysical Research Letters}, volume = {33}, number = {17}, year = {2006}, note = {ISI Document Delivery No.: 085ZJTimes Cited: 23Cited Reference Count: 28Knopf, D. A. Mak, J. Gross, S. Bertram, A. K.}, month = {Sep}, pages = {5}, type = {Article}, abstract = {The heterogeneous oxidation of a saturated hydrocarbon monolayer by NO3 was studied. A flow tube reactor coupled to chemical ionization mass spectrometry was used to determine the reactive uptake coefficient of NO3 on these surfaces, and X-ray photoelectron spectroscopy (XPS) was used to investigate surface oxidation and to determine if exposure to NO3 leads to volatilization of the organic substrate. The uptake coefficient of NO3 by an alkane monolayer is about (8.8 +/- 2.5) x 10(-4), which may lead to competitive oxidation compared with OH, due to the higher atmospheric abundance of NO3 under certain conditions. The XPS results are consistent with the formation of 1) C-O groups, 2) ketones or aldehydes, and 3) carboxylic groups. The XPS results also suggest that NO3 does not rapidly volatilize the organic surface: even under extremely polluted conditions, maximum 10\% of the organic layer is volatilized.}, keywords = {FILMS, GAS-PHASE PRODUCTS, HETEROGENEOUS REACTION, KINETICS, LIQUID, OLEIC-ACID, ORGANIC AEROSOLS, ozone, PARTICLES, REACTIVE UPTAKE}, isbn = {0094-8276}, url = {://000240642600004}, author = {Knopf, D. A. and Mak, J. and Gross, S. and Bertram, A. K.} } @article {1157, title = {Reactive uptake of O-3 by multicomponent and multiphase mixtures containing oleic acid}, journal = {Journal of Physical Chemistry A}, volume = {109}, number = {25}, year = {2005}, note = {ISI Document Delivery No.: 940CZTimes Cited: 55Cited Reference Count: 80}, month = {Jun}, pages = {5579-5589}, type = {Article}, abstract = {The heterogeneous reaction of O-3 with lauric acid/oleic acid (LA/OA) mixtures and myristic acid/oleic acid (MA/OA) mixtures were studied as a function of con position, physical state, and microstructure at 298 K. Lauric acid and myristic acid are both alkanoic acids whereas oleic acid is an alkenoic acid. Additionally, we investigated the uptake of O-3 by multicomponent mixtures that closely represent the composition of meat-cooking, aerosols. These measurements were performed with a rotating-wall flow-tube reactor coupled to a chemical ionization mass spectrometer. The reactive uptake coefficients (gamma) of O-3 on liquid LA/OA and MA/OA solutions range from 4 x 10(-4) to 7.2 x 10(-4) The gamma values measured for solid-liquid LA/OA and MA/OA mixtures (which consist of solid LA or solid MA. in equilibrium with a liquid) range from 2 x 10(-5) to 1.7 x 10(-4). These experiments show that only 79\% solid by mass in the solid-liquid mixture can decrease gamma by an order of magnitude compared to the liquid mixtures. The gamma values for solid-liquid mixtures that closely represent the composition of meat-cooking aerosols range from 1.6 x 10(-5) to 6.9 x 10(-5). We found that gamma of solid-liquid mixtures depends on the microstructure of the mixtures, which in turn depends on the method of preparing the films. Furthermore, experiments employing solid-liquid mixtures show an increase in gamma with increasing film age. This can be explained either by the formation of a nonequilibrium phase followed by its relaxation to the stable phase or by Ostwald{\textquoteright}s ripening, which refers to a change in the solid microstructure due to a tendency to minimize the total surface free energy of the solid. We used the obtained gamma values to estimate OA lifetimes for polluted atmospheric conditions. For liquid solutions, the lifetimes were on the order of a few minutes. The lifetimes derived for solid-liquid mixtures are up to 75 min, significantly longer than for liquid solutions. Our study emphasizes the effect of the physical state and microstructure of multicomponent mixtures on the heterogeneous chemistry.}, keywords = {AIR-POLLUTION, ATMOSPHERIC PARTICLES, CLOUD MICROPHYSICS, FINE ORGANIC AEROSOL, HETEROGENEOUS REACTION, KINETICS, METAL-ALLOYS, ozone, PARTICULATE MATTER, UNSATURATED FATTY-ACIDS}, isbn = {1089-5639}, url = {://000230122600007}, author = {Knopf, D. A. and Anthony, L. M. and Bertram, A. K.} }