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Photocatalysis of air chemistry by sea spray acidifying compounds investigated using an aerosol smog chamber

: Zetzsch, C.; Alebic-Juretic, A.; Behnke, W.; Nolting, F.

Borrell, P.; Seiler, W.:
Transport and Transformation of Pollutants in the Troposphere. Proceedings of EUROTRAC Symposium '90
The Hague: SPB Academic Publishing, 1991
ISBN: 90-5103-058-4
EUROTRAC Symposium <1, 1990, Garmisch-Partenkirchen>
Conference Paper
Fraunhofer ITA ( ITEM) ()
aerosol; air chemistry; air pollution; Luftchemie; Luftverschmutzung; photocatalysis; Photokatalyse; physical chemistry; physikalische Chemie; sea spray; Seespray; Smog; smog chamber; Smogkammer; Troposphäre; troposphere

The behaviour of sea spray in tropospheric chemistry is investigated by exposing airborne NaCl aerosol to a photochemical smog in an aerosol smog chamber facility. In the presence of NOx, an intrusion of NO3 into the aerosol is observed, leading to a corresponding release of HCl, that is mainly absorbed on the glass walls of the chamber. A photochemical formation of atomic Cl is observed, much exceeding the expected from the well-known reaction of OH with HCl in the gas phase or a reaction of O3 with solvated Cl-, even if all the HCl released remained in the gas phase. In accompanying dark experiments, molecular Cl2 is identified to be a major precursor of the atomic Cl. With a teflon bag in the chamber, in the presence of HCl gas and O3 at 5O per cent relative humidity, the aerosol SiO2 and Fe2O3 are observed to enhance the formation of Cl by factors of 2-10 as compared to the production by OH + HCl; TiO2 aerosol acts as a strong photocatalyst and is effective by a factor of up to 100 0, even in the absence of O3. Heterogeneous reactions occuring on the surface of the aerosol and on the glass convert a considerable fraction of the HCl and a portion of the hydrocarbons to chlorinated products like phosgene, chloroacetone and 1,1-dichloroacetone.