FIGURE 7.f6 Model-predicted fraction of HNO, (/,,NOl) produced by heterogeneous N205 and NO, hydrolysis in January (adapted from Dentener and Crutzen, 1993).

I Jun

FIGURE 7.17 Model-predicted ratio, R(u, of 03 concentrations with aerosol reactions included those without for all months (adapted from Dentener and Crutzen, 1993).

Indeed, reactions (50) and (51) represented the first syntheses of gaseous BrNOz (Finlayson-Pitts et al., 1989b) and IN02, respectively (Barnes et al., 1991). The importance of reactions (49)—(51) lies in the fact that the gaseous nitryl halides produced all absorb light in the actinic region, giving reactive halogen atoms (see Chapter 4.U). While the relative importance of these reactions as a source of halogen atoms is uncertain, they clearly could be important in the marine boundary layer as well as some distance inland from coastal marine areas. In addition, Michelangeli et al. (1991) have suggested they may occur in the stratosphere after the eruption of alkaline volcanoes such as El Chichon. Finally, some unique (hopefully!) situations such as the oil well burning in Kuwait produced plumes containing large concentrations of salt in which such reactions can potentially occur (e.g., Cahill et al., 1992). The reader is referred to reviews by Finlayson-Pitts (1993), Graedel and Keene (1995), and De Haan et al. (1999) for further discussion of this issue.

It should be noted that these reactions are analogous to the reactions of N205 with HC1 on ice discussed in Chapter 12.

A potential reaction of N2Os that, however, has not been reported to date in atmospherically relevant systems is the addition of N205 across the double bond of alkenes:

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