Heterogeneous reaction of N₂O₅ with illite and Arizona test dust particles

Abstract

The heterogeneous reaction of N2O5 with airborne illite and Arizona test dust (ATD) particles was investigated at room temperature and at different relative humidities using an atmospheric pressure aerosol flow tube. N2O5 at concentrations in the range 8 to 24 × 1012 molecule cm−3 was monitored using thermal-dissociation cavity ring-down spectroscopy at 662 nm. At zero relative humidity a large uptake coefficient of N2O5 to illite was obtained, γ(N2O5) = 0.09, which decreased to 0.04 as relative humidity was increased to 67%. In contrast, the uptake coefficient derived for ATD is much lower (~0.006) and displays a weaker (if any) dependence on relative humidity (0–67%). Potential explanations are given for the significant differences between the uptake behaviour for ATD and illite and the results are compared with uptake coefficients for N2O5 on other mineral surfaces.