Photochemistry of atmospheric dust: ozone decomposition on illuminated titanium dioxide.
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 x 10(-6) to 3 x 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.
Nicolas
Mélanie
M
Institut de recherches sur la catalyse et l'environnement de Lyon, Université de Lyon 1, CNRS, UMR5256, IRCELYON, Villeurbanne F-69626, France.
Ndour
Marieme
M
Ka
Oumar
O
D'Anna
Barbara
B
George
Christian
C
D000393:Air Pollutants / Q000737:chemistry*; D001272:Atmosphere / Q000737:chemistry*; D004391:Dust / Q000032:analysis*; D010126:Ozone / Q000737:chemistry*; D010777:Photochemistry; D014025:Titanium / Q000737:chemistry*
D000393:Air Pollutants; D004391:Dust; C009495:titanium dioxide; D010126:Ozone; D014025:Titanium