Photocatalysis and photosorption in the Earth's atmosphere

The troposphere of Earth is abundant in particles of solid and liquid aeros ols which have a large specific surface area and can be activated by visibl e light and wild ultraviolet (UV) solar radiation with wavelengths lambda > 300 nm for promoting different photocatalytic and photoadsorption processe s. This paper discusses possible heterogeneous photocatalytic and photosorp tion phenomena on the surface of solid tropospheric aerosols. These phenome na can proceed in nature at ambient conditions and can make an important co ntribution to the global chemistry of the Earths atmosphere. For example, t he particles of semiconductor metal oxides like TiO2, ZnO, and Fe2O3, are a ble to photocatalyze oxidation of organic compounds from the atmosphere by air oxygen and even mineralize them. For insulator metal oxides like SiO2, Al2O3, MhO, and CaO, which are the main components of tropospheric solid ae rosols, a substantial depletion of many halogen-containing organic compound s (freons) is possible via their destructive photoadsorption. All mentioned processes appear to be driven by mild solar UV radiation and can proceed i n the troposphere, in contrast to direct photochemistry which can take plac e only in the upper layers of the atmosphere.