Atmospheric oxidation of organic pollution in cloud droplets - a climate effect?

Surface coverage of oleic acid (left axis, circles) and surface tensio

Surface coverage of oleic acid (left axis, circles) and surface tension (right axis, solid line) versus time measured when a film on synthetic seawater was exposed to gas-phase ozone.
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Atmospheric aerosol affects global climate both directly, by absorbing and scattering solar radiation, and indirectly, by influencing cloud formation and growth.

Cloud droplets coated with an organic layer have different optical properties and potential to cause rain than uncoated droplets. Atmospheric oxidation of the organic layer in polluted airmasses may decrease drizzle potential and cloud albedo. We have used neutron scattering to demonstrate that the oxidation of an organic surfactant film (oleic acid) on aqueous atmospheric aerosol by atmospheric ozone will hinder cloud droplet growth. Our experiments reveal that the organic film is not destroyed by oxidation but chemically altered to give a film containing about half the original organic material and with a higher surface tension. These results are also important for the study of the stability of organic films on Langmuir troughs towards oxygen and ozone.

MD King (Royal Holloway University of London), AR Rennie (Uppsala University, Sweden), KC Thompson (Birkbeck University of London), FN Fisher (Royal Holloway University of London), CC Dong, RK Thomas (University of Oxford), AV Hughes (ISIS)

Research date: December 2007

Further Information

MD King et al., J. Am. Chem. Soc. 126 (2004) 16710; New Scientist
184 (2004) 2478 p9

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