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Title: Temporal and spatial variability of halogenated compounds and other trace gases
Author: O'Sullivan, Deborah Antoinette
ISNI:       0000 0001 3454 4290
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2008
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Air samples. from four aircraft campaigns and two surface experiments covering a large geographical area over both hemispheres have been analysed using the technique of gas chromatography mass spectroscopy (GCMS). Around 40 trace gases have been detected and where possible quantified, including most of the CFC's, HCFC's, and halon's, HFC-134a, HFC-152a, HFC-365mfc, CCI4, CH3CCb, CH3Br, CH3CI, and a number of short lived halogenated compounds including CH31, CHBr3, CH2BrCI, and n-C3H7Br. From the data obtained it has been possible to investigate the spatial and temporal variability of halogenated compounds, including variations with altitude, longitude, and interhemispheric ratios. Significant quantities of the short lived bromocarbons (CHBr3, CH2Br2, CH2BrCI, CHBr2CI, CHBrCI2, n-C3H7Br) and methyl iodide (CH31) have been observed in air samples collected within the upper troposphere lower stratosphere (UTLS) region of the atmosphere, implying that the contribution of these compounds to stratospheric ozone loss is potentially significant. Evidence has also been found which suggests that sub-tropical regions of the Pacific Ocean and' coastal waters around the Phillipines are particularly productive source regions for all of these compounds. In addition using data from a plant enclosure study the potential for terrestrial ecosystems to both emit and take up a number of halogenated compounds has been identified. Although the significance of these results remains unclear. The atmospheric mixing ratios of all four CFCs measured in this study are decreasing due to the reduction in global emissions of these compounds as a result of their regulation under the Montreal Protocol. A significant decrease in the mixing ratios of carbon tetrachloride (CCI4) and methyl chloroform (CH3CCb) has also been observed in the 2000 - 2006 CARIBIC data. In contrast there is evidence to suggest that halon's 1211 and 2402 are still slowly increasing in the atmosphere. For all the HCFC's and HFC's measured in this study (HCFC-21, HCFC22, HCFC-141b, HCFC-142b, HCFC-124, HCFC-123, HFC-134a, HFC-152a, and HFC365mfc), clear inter hemispheric gradients were observed with higher mixing ratios in the NH, consistent with a predominantly NH anthropogenic source for these compounds. However there is evidence to suggest that emissions from Asia are becoming increasingly important for a number of these compounds. In addition evidence was found which suggests a continuing source for CFC-11, CFC-12, CFC-113 and CFC-114.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available