Photochemistry of Atmospheric Dust: Ozone Decomposition on Illuminated Titanium Dioxide

• Published in: Environmental science & technology 2009-10, Vol.43 (19), p.7437-7442
• Main Authors: Nicolas, Mélanie, Ndour, Marieme, Ka, Oumar, D’Anna, Barbara, George, Christian
• Format: Article
• Language: English
• Subjects: Air Pollutants - chemistry; Applied sciences; Atmosphere - chemistry; Atmospheric pressure; Catalysis; Chemical Sciences; Dust - analysis; Environmental Processes; Exact sciences and technology; Humidity; Minerals; Ozone; Ozone - chemistry; Photochemistry; Pollution; Titanium - chemistry; Ultraviolet radiation
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es901569d

The ozone decomposition onto mineral surfaces prepared with traces of solid TiO2 in a matrix of SiO2 in order to mimic mineral dust particles has been investigated using a coated-wall flow-tube system at room temperature and atmospheric pressure. The ozone uptake coefficients were measured both under dark conditions and irradiation using near UV-light. While uptake in the dark was negligible, a large photoenhanced ozone uptake was observed. For TiO2/SiO2 mixtures under irradiation, the uptake coefficients increased with increasing TiO2 mass fraction (from 1 to 3 wt %), and the corresponding uptake coefficient based on the geometric surfaces ranged from 3 × 10−6 to 3 × 10−5. The uptake kinetics was also observed to increase with decreasing ozone concentration between 290 and 50 ppbv. Relative humidity influenced the ozone uptake on the film, and a reduced ozone loss was observed for relative humidity above 30%. The experimental results suggest that under atmospherically relevant conditions the photochemistry of dust can represent an important sink of ozone inside the dust plume.