Effects of SO₂ on NH₄NO₃ Photolysis: The Role of Reducibility and Acidic Products

Abstract

Nitrate photolysis is a vital process in secondary NOx release into the atmosphere. The heterogeneous oxidation of SO2 due to nitrate photolysis has been widely reported, while the influence of SO2 on nitrate photolysis has rarely been investigated. In this study, the photolysis of nitrate on different substrates was investigated in the absence and presence of SO2. In the photolysis of NH4NO3 on the membrane without mineral oxides, NO, NO2, HONO, and NH3 decreased by 17.1, 6.0, 12.6, and 57.1% due to the presence of SO2, respectively. In the photolysis of NH4NO3 on the surface of mineral oxides, SO2 also exhibited an inhibitory effect on the production of NOx, HONO, and NH3 due to its reducibility and acidic products, while the increase in surface acidity due to the accumulation of abundant sulfate on TiO2 and MgO promoted the release of HONO. On the photoactive oxide TiO2, HSO3 –, generated by the uptake of SO2, could compete for holes with nitrate to block nitrate photolysis. This study highlights the interaction between the heterogeneous oxidation of SO2 and nitrate photolysis and provides a new perspective on how SO2 affects the photolysis of nitrate absorbed on the photoactive oxides.

The heterogeneous reactions of toluene/O3/NH3 on hematite nanoparticles: the impact of light illumination on organic ammonium salt formation

“…In addition, the NH 4 + might be volatilized under high light intensity, which would lead to some ammonium benzoate separated from the surface of hematite nanoparticles. 60 From what have been discussed above, light illumination promoted NOC formation from the heterogeneous reactions of toluene/O 3 /NH 3 on hematite nanoparticles compared to that under the dark condition.…”

“…The main reason for this phenomenon was the volatilization of ammonium salts under high light intensities. 60 Although the growth trend of spectral peak intensity was lower, the production of organic ammonium salts under the light intensity of 100 mW cm −2 was still stronger than that under the dark condition.…”