We have undertaken a kinetic study of heterogeneous ozone decomposition on alpha-Fe2O3 (hematite) and alpha-Al2O3 (corundum) aerosols under ambient conditions of temperature, pressure, and relative humidity in order to better understand the role of mineral dust aerosol in ozone loss mechanisms in the atmosphere. The kinetic measurements are made in an environmental aerosol reaction chamber by use of infrared and ultraviolet spectroscopic probes. The apparent heterogeneous uptake coefficient, gamma, for ozone reaction with alpha-Fe2O3 and alpha-Al2O3 surfaces is determined as a function of relative humidity (RH). The uptake of ozone by the iron oxide surface is approximately an order of magnitude larger than that by the aluminum oxide sample, under dry conditions. At the pressures used, alpha-Fe2O3 shows clear evidence for catalytic decomposition of ozone while alpha-Al2O3 appears to saturate at a finite ozone coverage. The measured uptake for both minerals decreases markedly as the RH is increased. Comparison with other literature reports and the atmospheric implications of these results are discussed.

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Mineral dust aerosol plays an important role in the Earth's radiative budget on both regional and global scales. To better understand the impact of this component of the Earth's atmosphere, the extinction spectra for several key components of mineral dust aerosol have been measured in an environmental aerosol reaction chamber. The extinction spectra are measured over a broad wavelength range, which includes both IR (650 to 5000 cm−1) and UV‐Vis (12,500 to 40,000 cm−1) spectral regions. Experimental data are compared with Mie theory simulations derived from available literature optical constants. In a few cases, we have needed to modify the published optical constant data sets to ensure Kramers‐Kronig consistency. In general, the Mie‐based simulations are in excellent agreement with experimental data over the full IR‐UV spectral range, except in the immediate neighborhood of the IR resonance absorption lines where particle shape effects on the resonance line profiles can be significant.

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