Atmospheric Science

Up with Bromine

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Science  08 Dec 2000:
Vol. 290, Issue 5498, pp. 1859
DOI: 10.1126/science.290.5498.1859c

Major volcanic eruptions eject particles and gases into the stratosphere, including the halogens chlorine (Cl) and bromine (Br), both of which contribute to the catalytic destruction of ozone, but the magnitude of the volcanic contribution of these gases is uncertain. Although enlarged polar ozone holes were observed after the Pinatubo eruption in 1991, these were attributed primarily to the effects of sulfate aerosols and other particles from the eruption on the formation of polar stratospheric clouds. Most of the volcanic Cl (which forms HCl) is likely scavenged before it reaches the stratosphere, but the potential effects of Br, which is much more potent at destroying ozone than Cl, are not well studied.

Bureau et al. now present a series of experiments which suggest that the Pinatubo eruption and other comparable eruptions could inject as much Br into the atmosphere as the annual budget from all other natural and anthropogenic sources. Their results show that in magmas, Cl, Br, and I partition strongly into a hydrous fluid phase, which is responsible for driving violent eruptions. Bromine seems less likely to be washed out in the eruption column than Cl, although further study of this is needed. — BH

Earth Planet. Sci. Lett. 183, 51 (2000).

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