Ozone decomposition on Saharan dust: an experimental investigation
[摘要] The heterogeneous reaction betweenO3 and authentic Saharan dust surfaces was investigated in a Knudsen reactor atapprox 296 K. O3 was destroyed on the dust surface andO2was formed with conversion efficiencies of 1.0 and 1.3 molecules O2per O3 molecule destroyed forunheated and heated samples, respectively. No O3 desorbed from exposed dust samples,showing that the uptake was irreversible. The uptake coefficients for the irreversibledestruction of O3 on (unheated) Saharan dust surfaces depended on theO3 concentration andvaried between 3.5 x 10-4 and 5.5 x 10-6 for the initial uptake coefficient(g0approx 3 x 10-5 at 30 ppbv O3 STP) and between4.8 x 10-5 and 2.2 x 10-6 for the steady-state uptake coefficient(gssapprox 7 x10-6 at 30 ppbv O3 STP). At very highO3 concentrations the surface was deactivated,and O3 uptake ceased after a certain exposure period. Sample re-activation(i.e. de-passivation) was found to occur over periods of hours, after exposure toO3 had ceased,suggesting that re-activation processes play a role both in the laboratory and in the atmosphere.
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[效力级别] [学科分类] 大气科学
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