Uptake of hydrogen peroxide on the surface of Al2O3 and Fe2O3
Résumé
The heterogeneous interaction of H2O2 with solid films of Al2O3 and Fe2O3 was investigated under dark conditions and in presence of UV light using a low pressure flow tube reactor coupled with a quadrupole mass spectrometer. The uptake coefficients were measured as a function of the initial concentration of gaseous H2O2 ([H2O2]0 = (0.15–16.6) × 1012 molecule cm−3), irradiance intensity (JNO2=0.002−0.012s−1JNO2=0.002−0.012s−1), relative humidity (RH = 0.003–73%) and temperature (T = 268–320 K). Deactivation of mineral surfaces upon exposure to H2O2 was observed and only initial uptake coefficients of H2O2 were quantified, given by the following expressions: γ0 (Al2O3) = 1.10 × 10−3/(1 + RH0.93) and γ0 (Fe2O3) = 1.05 × 10−3/(1 + RH0.73) (calculated using BET surface area, estimated conservative uncertainty of 30%) at T = 280 K. The initial uptake coefficients were found to be independent of the UV irradiation intensity and concentration of H2O2. Temperature dependence of γ0 measured at RH = 0.3% corresponded to almost temperature independent values of γ0 at lower temperatures of the study (268–280 K) and to rather rapid decrease of γ0 with increase of temperature above 290 K, according to the following expressions: γ0 (Al2O3) = 8.7 × 10−4/(1 + 5.0 × 1013exp(−9700 T−1)) and γ0 (Fe2O3) = 9.3 × 10−4/(1 + 3.6 × 1014exp(−10300 T−1)). The present experimental data support current considerations that uptake of H2O2 on mineral aerosol is potentially an important atmospheric process which should be accounted for in the atmospheric models.