Emission of biogenic halocarbons in temperate and tropical coastal zones

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.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2013

Author dc:creator

• Leedham, Emma C.

Language dc:language

en