Hydrogen Peroxide and Its Decay Products

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). 

Several dozen measurements of atmospheric H2O2 levels in air, precipitation, and cloudwater have been summarized by Gunz and Hoffmann (1990). A strong tendency for H2O2 to partition from the vapor phase to the liquid phase is reflected by its high Henry s law coefficient of about 10 M/atm (Yoshizumi et al., 1984 Martin and Damschen, 1981) there are also several mechanisms for direct in situ formation in the aqueous phase. 

Concentrations of hydrogen peroxide in atmospheric water samples such as rainwater are usually considerably higher than those determined in surface water samples. For example, Zika et al. (1982) found rainwater collected in southern Florida and the Bahamas to contain levels ranging from 1-7 x 10 M. Levels of up to 3 X 10 M were detected in southern California and Tokyo rainwater (Kok, 1980 Yoshizumi et al., 1984), although the usual hourly mean concentration was about an 

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