Bromine Chemistry in the Stratosphere

FIGURE 12.44 Organic bromine compounds observed at the earth s surface from 1988 to 1996 (adapted from Wamsley et al., 1998). 

Chapter 4, the absorption cross sections of the major sources of bromine to the stratosphere, CH3Br, CBrClF2 (Halon-1211), and CBr3F (Halon-1301), are substantial well out into the 250-nm region. The C-Br bond is even weaker than the C-Cl bond, as is generally the case for bromine compared to chlorine bonds (e.g., Lee et al., 1999a). For example, the C-Br bond strength is 70 kcal mol-1 versus 85 kcal mol-1 for C-Cl and 110 kcal mol-1 for C-F the C-Br bond breaks first  

FIGURE 12.45 Schematic of gas-phase and heterogeneous bromine chemistry in the stratosphere. The heavier dark lines show the heterogeneous (het) chemistry. 

The atmospheric chemistry of other bromo-chloromethanes that are present in smaller amounts in the troposphere (Fig. 12.44) is discussed by Orkin et al. (1997) and Bilde et al. (1998). 

These sinks for Br compete with its reaction (32) with Os  

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