Heterogeneous Reaction of NO2 on Al2O3: The Effect of Temperature on the Nitrite and Nitrate Formation

Although recent evidence suggests that the heterogeneous reaction of NO2 on the surface of mineral aerosol plays an important role in the atmospheric chemistry, a fundamental understanding of how temperature influences the rate and extent of nitrate formation processes remains unclear. This work presents the first laboratory study of the effect of temperature on heterogeneous reaction of NO2 on the surface of gamma-Al2O3 in the temperature range of 250-318 K at ambient pressure. From the analysis of IR spectra, nitrite was found to be an intermediate product at temperatures between 250 and 318 K. It is proved by our experiments that nitrite would convert to the bidentate nitrate as the reaction proceeded. In addition, it is interesting to find that the rate of conversion increased with decreasing temperature. Along with nitrite decrease, the initial rate of nitrate formation increased while the rate of nitrate formation in the steady region decreased with decreasing temperature. The uptake coefficients at seasonal temperatures were determined for the first time and were found to be sensitive to temperature. Finally, atmospheric implications of the role of temperature on the heterogeneous reaction of NO2 with mineral aerosol are discussed.