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Abstract:
Halocarbons are important vectors of reactive halogens to the
atmosphere, where the latter participate in several chemical key
processes. Many efforts have been made to quantify their sources and
sinks. However, those are still designated to large uncertainties. In
contrast to other coastal habitats such as salt marshes and kelp
communities, seagrass meadows have so far not been investigated with
regard to trace gases. In order to study seagrass meadows as a potential
source for halocarbons to the atmosphere, we conducted dynamic flux
chamber measurements at a coastal site in List/Sylt, Northern Germany.
Emissions of halocarbons from seagrass meadows into the atmosphere were
found for chloromethane (CH3Cl), bromomethane (CH3Br), iodomethane
(CH3I), and bromoform (CHBr3) being the main compounds, while the
sediment seems to be a net sink for CH3Cl and CH3Br. Stable carbon
isotopes of halocarbons were determined using a newly developed
comprehensive coupled isotope and mass balance for dynamic flux
chambers. Mean stable carbon isotope compositions of the emitted
halocarbons were -50 parts per thousand (CH3Cl), -52 parts per thousand
(CH3Br), -63 parts per thousand (CH3I) and -14 parts per thousand
(CHBr3). (C) 2013 Elsevier Ltd. All rights reserved.
