The reaction of alumina as a model substance for mineral aerosols with NO2 or HNO3 was studied using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The formation of nitrate on the Al2O3 surface was observed in both cases. In addition, during the initial phase of the NO2 reaction, intermediate nitrite formation was observed. The DRIFTS data provide insight into the reaction mechanism, which involves reaction of surface OH groups, the formation of a {AlOOH···NO2} adduct, and the formation of acidic OH groups. The reaction order in NO2 of 1.86 ± 0.1 was determined from a quantitative kinetic evaluation of a series of experiments with NO2 concentrations in the range of 1013 to 1015 molecules cm-3. The reactive uptake coefficient, γ, was determined from the infrared absorbance, which was calibrated by ion chromatography, and from the Al2O3 Brunauer−Emmett-Teller (BET) surface area. γ depended linearly on the NO2 concentration and varied from γ = 7.3 × 10-10 to 1.3 × 10-8 for [NO2] = 2.5 × 1013 to 8.5 × 1014 molecules cm-3. Estimations of the atmospheric impact showed that at these above conditions (γ = 10-9) nitrate formation on mineral aerosol from the NO2 reaction would be negligible.

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Stringent regulations worldwide will limit the level of particulate matter (PM) and particle number (PN) emitted from gasoline engines. Gasoline particulate filters (GPFs) present one strategy for meeting PM and PN limits over the full operating range of the engine. Over time these filters accumulate incombustible ash, increasing system pressure drop and adversely effecting engine performance. The effect of aging as a result of ash accumulation is examined over the full lifetime of gasoline particulate filters, using a novel accelerated aging system. This system utilizes a gasoline combustion chamber into which lubricating oil is injected simulating combustion in the cylinder — the primary source of ash. This report details the construction and validation of this system.