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.
Institut de recherches sur la catalyse et l'environnement de Lyon, Université de Lyon 1, CNRS, UMR5256, IRCELYON, Villeurbanne F-69626, France.
Mélanie
M
Nicolas
Marieme
M
Ndour
Oumar
O
Ka
Barbara
B
D'Anna
Christian
C
George
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