20th century trends and budget implications of chloroform and related tri- and dihalomethanes inferred from firn air

Worton, D.R.; Sturges, W.T.; Schwander, J.; Mulvaney, R. ORCID: https://orcid.org/0000-0002-5372-8148; Barnola, J.-M.; Chappellaz, J.. 2006 20th century trends and budget implications of chloroform and related tri- and dihalomethanes inferred from firn air. Atmospheric Chemistry and Physics, 6 (10). 2847-2863. https://doi.org/10.5194/acp-6-2847-2006

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Abstract/Summary

Four trihalomethane (THM; CHCl3, CHBrCl2, CHBr2Cl and CHBr3) and two dihalomethane (DHM; CH2BrCl and CH2Br2) trace gases have been measured in air extracted from polar firn collected at the North Greenland Icecore Project (NGRIP) site. CHCl3 was also measured in firn air from Devon Island (DI), Canada, Dronning Maud Land (DML), Antarctica and Dome Concordia (Dome C), Antarctica. All of these species are believed to be almost entirely of natural origin except for CHCl3 where anthropogenic sources have been reported to contribute ~10% to the global burden. A 2-D atmospheric model was run for CHCl3 using reported emission estimates to produce historical atmospheric trends at the firn sites, which were then input into a firn diffusion model to produce concentration depth profiles that were compared against the measurements. The anthropogenic emissions were modified in order to give the best model fit to the firn data at NGRIP, Dome C and DML. As a result, the contribution of CHCl3 from anthropogenic sources, mainly from pulp and paper manufacture, to the total chloroform budget appears to have been considerably underestimated and was likely to have been close to ~50% at the maximum in atmospheric CHCl3 concentrations around 1990, declining to ~29% at the beginning of the 21st century. We also show that the atmospheric burden of the brominated THM's in the Northern Hemisphere have increased over the 20th century while CH2Br2 has remained constant over time implying that it is entirely of natural origin.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.5194/acp-6-2847-2006
Programmes:	BAS Programmes > Global Science in the Antarctic Context (2005-2009) > Climate and Chemistry - Forcings and Phasings in the Earth System
ISSN:	1680-7316
Format Availability:	Electronic, Print
Additional Information. Not used in RCUK Gateway to Research.:	Open access journal
Additional Keywords:	Snow chemistry , Methane
NORA Subject Terms:	Glaciology Atmospheric Sciences
Date made live:	19 Jul 2007 13:49 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/166

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