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Journal article

Ozone decomposition on Saharan dust: an experimental investigation

Hanisch F, Crowley J ...see all

Atmospheric Chemistry and Physics, vol. 3 (2003) pp. 119-130

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Abstract

The heterogeneous reaction between O-3 and authentic Saharan dust
surfaces was investigated in a Knudsen reactor at; approximate to296
K. O-3 was destroyed on the dust surface and O-2 was formed with
conversion efficiencies of 1.0 and 1.3 molecules O-2 per O-3 molecule
destroyed for unheated and heated samples, respectively. No O-3 desorbed
from exposed dust samples, showing that the uptake was irreversible.
The uptake coefficients for the irreversible destruction of O-3 on
(unheated) Saharan dust surfaces depended on the O-3 concentration
and varied between 15 X 10(-4) and 5.5 x 10 6 for the initial uptake
coefficient (gamma(0) approximate to 3 x 10(-5) at 30 ppbv O-3 {STP)}
and between 4.8 x 10(-5) and 2.2 x 10(-6) for the steady-state uptake
coefficient {(gamma(SS)} approximate to 7 x 10(-6) at 30 ppbv O-3
{STP).} At very high O-3 concentrations the surface was deactivated,
and O-3 uptake ceased after a certain exposure period. Sample re-activation
(i.e. de-passivation) was found to occur over periods of hours, after
exposure to O-3 had ceased, suggesting that re-activation processes
play a role both in the laboratory and in the atmosphere.

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Authors

  • F. Hanisch

  • J. N. Crowley

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