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Methyl bromide, other brominated methanes, and methyl iodide in polar firn air

Sturges, W.T.; McIntyre, H.P.; Penkett, S.A.; Chappellaz, J.; Barnola, J.-M.; Mulvaney, R.; Atlas, E.; Stroud, V.. 2001 Methyl bromide, other brominated methanes, and methyl iodide in polar firn air. Journal of Geophysical Research, 106 (D2). 1595-1606. 10.1029/2000JD900511

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Abstract/Summary

We report measurements of brominated, bromochlorinated, and iodinated methanes in air extracted from deep firn at three polar locations (two Antarctic and one Arctic). Using a firn diffusion model, we are able to reconstruct a consistent temporal trend for methyl bromide from the two Antarctic sites. This indicates a steady increase by about 2 ppt from the midtwentieth century to 8 ppt today. The Arctic firn, however, contained extremely high levels of methyl bromide as well as numerous other organic gases, which are evidently produced in situ. The other brominated species (dibromomethane, bromochloromethane, bromodichloromethane, dibromochloromethane, and bromoform) showed little or no long-term trend in Antarctic firn and therefore are evidently of entirely natural origin in the Southern Hemisphere. A clear seasonal trend was observed in the upper firn for the shortest-lived halocarbons (notably bromoform and methyl iodide). The same species were present at lower abundance at the higher altitude and more inland Antarctic site, possibly due to their origin from more distant oceanic sources.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1029/2000JD900511
Programmes: BAS Programmes > Antarctic Science in the Global Context (2000-2005) > Signals in Antarctica of Past Global Changes
ISSN: 0148-0227
NORA Subject Terms: Atmospheric Sciences
Chemistry
Date made live: 12 Nov 2012 09:24
URI: http://nora.nerc.ac.uk/id/eprint/20305

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