Kinetics and mechanism of the heterogeneous reaction of N2O5 with mineral dust particles.

The heterogeneous interaction of N2O5 with Saharan dust particles was investigated using aerosol flow tubes with detection of N2O5 by cavity-ring-down spectroscopy. The uptake coefficient, γ, was determined to be 0.02 ± 0.01 on airborne Saharan dust particles, independent of relative humidity (RH, 0-67%) and initial N2O5 concentration (5 × 10(11)-3 × 10(13) molecule cm(-3)). Analysis of gas- and particulate phase products suggests that N2O5 undergoes heterogeneous hydrolysis forming particulate nitrate. The independence of γ on the initial N2O5 concentration indicates that, on the seconds time scale of these experiments, the heterogeneous reaction of N2O5 with dust particles is not restricted to the external particle surface but internal reactive sites are also available. The particles could be deactivated with respect to N2O5 uptake only when pre-treated with very high levels of HNO3.