Effects of NO2 on oxidation mechanisms of atmospheric pollutant SO2 over Baumberger sandstone

The influence of NO2 on oxidation of atmospheric pollutant gas SO2 has been studied through Baumberger sandstone degradation. Experiments were conducted in a set of laboratory atmospheric chambers. By exposure of stone specimens to various pollutant regimes; e.g. single and combined pollutant gases (SO2, NO2), the reaction products (i.e. nitrite, nitrate, sulphite and sulphate) collected from run-off solutions as well as extracted from stones were analysed. Presentation rates of pollutant gases in terms of mg/cm2 s have been used to assess the interaction of SO2 and NO2 pollutant gases with Baumberger sandstone. For the first time, the contribution of NO2 to SO2 oxidation over the sample surface has been quantified (e.g. 37% in dry surface condition and 9% in wet surface condition). SO2 oxidation over Baumberger sandstone in the presence of NO2 produces nitrates over the surface of the sample; however, when no sandstone is present no NO2 oxidation is produced.