Long term, continuous and high frequency measurements of CHBr3 and CH2Br2 from five different AGAGE stations have been presented and analysed in this thesis. The CHBr3 and CH 2Br2 mixing ratio ranged from 0.93 ppt to 65.26 ppt. Their background concentration is approximately 0.98 and 1.01 ppt for the Northern Hemisphere. CHBr3 and CH 2Br2 data correlated very well with each other across all five stations. At coastal locations, both bromocarbons displayed a seasonal variation induced by local, summer production. The seasonal variation detected at Jungfraujoch station was dictated by the stronger summer loss processes. Higher CHBr3 and CH2Br2 concentrations often come from coastal sectors, suggesting macroalgae sources. Through AGAGE measurements, the global CHBr3 emission is estimated to be between 1 ± 0.04 Tg Br y(l and 4.9 ± 0.2 Tg Br y(l (based on 57 to 280 Gg Br yr-1 emission of CH2Br2) via a calculated 0.085 ([CH2Br21/[CHBr31) source ratio estimate. CHBr3, CH2Br2 and several halocarbons' degradation schemes and their subsequent halogen chemistry scheme has been incorporated into a three-dimensional tropospheric Lagrangian Chemistry Transport model - STOCHEM CRI v2-R5 . STOCHEM-CRI allowed us to validate the high emission estimate derived from AGAGE measurements, predict the distribution of the source and product gases and study the impact of CHBr3/Bromine on tropospheric species such as ozone. CHBr3 and CH2Br2 estimated lifetimes in STOCHEM-CRI are shorter than the literature values. Their organic product gases are all short lived species that rapidly degrade and produce inorganic bromine product gases. CHBr3 and CH2Br2 zonal plots indicate possible source gas injection of Br into the stratosphere. Zonal plots of Brx (mainly as Br, BrO, HOBr and BrN02) suggest the possibility of product gas injection of Br into the stratosphere. CHBr3 and halogen chemistry has reduced the overall oxidation capacity of the lower troposphere. 1.12% of the total 0 3 burden is lost per Tg of Br emitted into the model. Other radical species' burden also decreased, while hydrocarbon burdens increased
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:682722 |
| Date | January 2014 |
| Creators | Xiao, Ping |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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