Emission of biogenic halocarbons in temperate and tropical coastal zones

Leedham, Emma C. (2013) Emission of biogenic halocarbons in temperate and tropical coastal zones. Doctoral thesis, University of East Anglia.

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Abstract

Biogenically-produced halocarbons play an important role in regional and global biogeochemical
processes. These compounds are short-lived (lifetimes <6 months) and so have temporal and
spatial variability in their atmospheric distributions. Marine regions, in particular coastlines, have
been identified as important source regions for these compounds, and within these regions
macroalgae (seaweeds) are an important source. Despite their short lifetime, it is believed that
biogenic bromocarbons may contribute to stratospheric inorganic bromine (Bry). Measurement and
model studies have identified a 6 (1-8) ppt excess of stratospheric Bry that cannot be accounted for
via known sources of longer-lived halocarbons. Tropical regions are believed to play an important
role in this process, as deep convection may act as a rapid transport mechanism allowing these
compounds to reach the upper troposphere within their atmospheric lifetimes. Despite this
potential importance, gaps still remain in our knowledge of halocarbon biogeochemistry in this
region. This study provides the first dedicated measurements of tropical macroalgae via laboratory
incubations of 15 species. Laboratory studies on temperate macroalgae were also performed, with
a focus on the impact of exposure and desiccation on halocarbon emissions. Desiccation-related
halocarbon emissions are of interest due to a growing seaweed aquaculture industry; seaweeds are
often left to dry before processing. In situ atmospheric measurements of halocarbons around
Malaysia as part of the SHIVA campaign are also reported here. A study of halocarbon
concentrations in Malaysia allowed the identification of different regions characterised by different
source and atmospheric transport processes. We identified that strong coastal sources do exist in
this region, but that their distribution is patchy and model studies should not assume a constant,
strong coastal source. Laboratory and field measurements were combined in a final discussion
providing annual emission estimates for the Malaysian and south east Asian region. Of particular
interest is the potential impact of aquaculture, which, if projected expansions in production are met,
could account for a considerable proportion of future Malaysian annual bromoform emissions.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Brian Watkins
Date Deposited: 29 Jul 2013 13:40
Last Modified: 29 Jul 2013 13:40
URI: https://ueaeprints.uea.ac.uk/id/eprint/43075
DOI:

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