[Zurück]

L. Nieto-Gligorovski, S. Net, S. Gligorovski, H. Wortham, H. Grothe, C. Zetzsch:
"Spectroscopic study of organic coatings on fine particles, exposed to ozone and simulated sunlight";
Atmospheric Environment, 44 (2010), 40; S. 5451 - 5459.

This work intends to quantify the variation in optical properties of aerosol by in situ spectroscopic monitoring the ozonolysis of a mixture of typical biomass burning compounds. The
reaction occurs on silica and glass particles in the presence of simulated sunlight. Fused silica particles (Aerosil) were coated with a thin film of a mixture of 4-phenoxyphenol and 4-carboxybenzophenone. UV-VIS spectra of dichloromethane extracts from the particles recorded before and after treatment show development of a new band after prolonged ozone and light exposure.
Changes in optical properties are reported, and variations of spectroscopic features are discussed. We show that the ozone-induced heterogeneous photochemical reaction does produce species absorbing
light in the solar spectral range. Further, we demonstrate that the heterogeneous photosensitized reactions at 200ppb ozone (strongly ozone polluted regions) for a time period of 7h aging process can
increase of light absorption of atmospheric aerosols in the tropospheric actinic window (> 290 nm) by 0.4 absorption units * ng-C-1 * O3 ppm-1 in the region 290-358nm and by 1.0 absorption units * ng-C-1 * O3 ppm-1 in the region 360-448nm. Chemical changes of such surface films were identified by diffuse reflectance infrared Fourier transform spectroscopy of coated glass spheres, and we suggest formation of humic-like substances comparable to those reported in continental aerosol.

http://dx.doi.org/10.1016/j.atmosenv.2009.10.043