Bromine, atmospheric chemistry

Orlando JJ (2003) Atmospheric chemistry of organic bromine and iodine compounds. Handbook Environ Chem 3R 253-299. 

The halogen family, fluorine, chlorine, bromine, and iodine has only recently been introduced into atmospheric chemistry.9 The catalytic cycle, with an atom such as Cl in the presence of its monoxide CIO, can... 

The atmospheric chemistry of bromine can be regarded as similar to that of chlorine. As far as HF is concerned, it does not react with hydroxyl since it persists, it limits the concentration of the atom F and its oxide FO. Hence, HF is the sink for fluorine in the stratosphere, before it disappears in the troposphere. 

The atmospheric chemistry of the organobromides is similar to that of the organochlo-rides degradation ultimately produces bromine atoms which may participate in catalytic destruction of ozone through a BrOx catalytic cycle (reactions 12 and 13). 

Investigation of photochemical properties of molecules important for atmospheric chemistry, especially bromine and nitrogen containing compounds (Institut Jozef Stefan, Ljubljana). 

Keywords Atmospheric chemistry Water reactions Bromine atoms OH radicals Potential energy surfaces Ab initio computations... 

The formation quantum yields of the excited bromine atoms Br( Pi/2) increases from 0.4 at 444 nm to 0.89 at 510 nm close to the dissociation limit of reaction (4.82), and then decreases (Peterson and Smith 1978). As for the photolytic processes of Br2, several other studies have also been made (Haugen et al. 1985 Cooper et al. 1998), but no absolute photolytic quantum yields has been measured. For the purpose of atmospheric chemistry total photolytic quantum yields of Br2 can be approximated to be unity for the wavelength region of 200-510 nm. 

Wennberg, P. Atmospheric chemistry bromine explosion. Nature 397, 299-301 (1999)... 

The family method was applied within an atmospheric chemistry box model to NOy, HOx, Cly, Ox and Bry families in order to study the effect of increases in ground level bromine emissions on stratospheric ozone by Ramarosmi et al. (1992), and for simulations of lower stratospheric HCl in Douglass and Kawa (1999). The nonlinear features of tropospheric ozone production from nitrogen oxides and VOCs were reproduced using a numerical method based on family methods in Elliott et al. (1996). 

Like the PCDD/PCDFs discussed previously, the environmental persistence of these species is controlled not only by their gas-phase chemistry, but also by processes occurring in the particle phase, on surfaces, and in the aqueous phase. The vapor pressures of these species, especially the multiply brominated congeners, are quite low, and so gas-phase studies are difficult and usually limited to temperatures above 300 K. The limited knowledge of the atmospheric chemistry of the PBDEs is summarized below. 

Carothers claimed that he kept going only because he finally received one of Illinois few scholarships, 750 embellished with esteem. But he must also have persevered because he loved chemistry. As he admitted, even the smell of his laboratory coat, saturated with the inexpressibly pungent and complicated odors of lab no. 219 [filled him] with a nostalgia to return to the atmosphere of sweetly blended sulfur dioxide, bromine, chlorine, ammonia, hydrogen chloride, phosgene, chloroacetone, etc., etc., etc. ... 

Information available regarding the chemistry of lead in air is limited. Before the ban on sales of leaded gasoline, lead particles were emitted to the atmosphere from automobiles as lead halides (mostly PbBrCl) and as double salts with ammonium halides (e.g., 2PbBrCl NH4Cl. Pb3[P04]2, and PbS04 [Biggins and Harrison 1979 Ter Haar and Bayard 1971]). After 18 hours, approximately 75% of the bromine and 30-40% of the chlorine disappeared, and lead carbonates, oxycarbonates and oxides were produced. 

A third factor comes into play in bromine chemistry, which is that atmospheric solutions containing bromide and chloride are most typically formed from seawater. Wave action generates small airborne droplets of seawater, which thus initially contain the elements in the ratios found in seawater. The molar ratio of Br- to Cl- is 1 650. However, despite the relatively small amounts of bromide relative to chloride, it plays a disproportionate role because of its reactivity and because its chemistry is closely intertwined with chloride ion chemistry. Table 8.16, for example, shows some of the interhalogen reactions of bromide and chloride. It can be seen that the chemistry preferentially generates Br2 rather than Cl2. 

These data also demonstrate the impact of bromine chemistry on the stratosphere (see Chapter 12.D). The initial ODP for methyl bromide is 15, due primarily to the large a factor associated with bromine chemistry. However, since it is removed by reaction with OH in the troposphere as well as by other processes such as hydrolysis in the oceans and uptake by soils and foliage (see Chapter 12.D), it has a short atmospheric lifetime of 1.3 years and hence the ODP decreases rapidly with time, toward a long-term steady-state value. 

Singh, O.N. and Fabian, P. (1999) Reactive bromine compounds, in P. Fabian and O.N. Singh (eds.). Reactive Halogen Compounds in the Atmosphere, The Handbook of Environmental Chemistry Vol. 4E, Springer, Berlin, pp. 1-43. 

The discovery of relationships between atmospherical and soil chemistry opened new possibilities for explanations of geomedical causes. Earlier, cases of goitre were often ascribed to the fact that people used too little salt-water fish in their diet. Recent investigations have shown, however, that in inland districts with low precipitation, the soil as well as the vegetation has a low iodine content (LIg, 1972). Whether the differences in the bromine content, which also was found, has any influence, is unknown. 

---