Hydrogen peroxide, tropospheric sources

The formation of hydrogen peroxide by photolysis of natural waters is discussed in Chapter 6. It is also formed by illumination of some sands and semiconductor oxides (Kormann et al., 1988 see also Section 6.E.3). Other sources of H2O2 include formation in the gas phase of the troposphere by the self-termination (dismutation) reaction of OOH and the autooxidation of reduced transition metals such as iron (Equation 4.4). The formation and fate of H2O2 in the atmosphere has been reviewed (Gunz and Hoffmann, 1990 Sakugawa et al., 1990). 

Hydrogen peroxide H2O2 is formed by the radical termination reaction HO2 + HO2, and exists in the troposphere generally at the mixing ratio in order of ppbv. Since H2O2 is water soluble, it is removed by the dissolution into cloud and fog water, while photolytic reaction is another important removal process. Methyl hydroperoxide CH3OOH also exists in the whole region of the troposphere in natural atmosphere as an oxidation product of methane. Its photolytic reaction is important as its removal process, and also as a radical source in the upper troposphere. 

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