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GEOPHYSICAL RESEARCH LETTERS, VOL. 25, NO. 20, PAGES 3835–3838, 1998

Heterogeneous Chemistry of NO₂ on Mineral Oxide Particles: Spectroscopic Evidence for Oxide-Coordinated and Water-Solvated Surface Nitrate

T. M. Miller

Department of Chemistry, University of Iowa, Iowa City

V. H. Grassian

Department of Chemistry, University of Iowa, Iowa City

Abstract

In this study, transmission FT-IR and diffuse reflectance UV-vis spectroscopies were used to probe the heterogeneous chemistry of gaseous nitrogen dioxide on mineral oxide particles. In particular, the role of pre- and post-adsorbed water on the heterogeneous chemistry of NO₂ on Al₂O₃ and TiO₂ was investigated. At 298 K, NO₂ reacts with the surface of these mineral oxides to form surface nitrite and nitrate. The spectroscopic data show that two distinct types of surface nitrate exist, oxide-coordinated and water-solvated nitrate. The relative amounts of oxide-coordinated and water-solvated nitrate are dependent on the coverage of adsorbed water on the surface of the mineral oxide particle. The importance of this water layer in the heterogeneous atmospheric chemistry of mineral oxide aerosol is discussed.

Received 20 May 1998; accepted 21 August 1998.

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Citation: Miller, T. M., and V. H. Grassian (1998), Heterogeneous Chemistry of NO₂ on Mineral Oxide Particles: Spectroscopic Evidence for Oxide-Coordinated and Water-Solvated Surface Nitrate, Geophys. Res. Lett., 25(20), 3835–3838.

Copyright 1998 by the American Geophysical Union.