A Novel Mass Spectrometer for Atmospheric Measurements & Halocarbons During the CARIBIC and SAMBBA Aircraft Campaigns

Wisher, Adam (2015) A Novel Mass Spectrometer for Atmospheric Measurements & Halocarbons During the CARIBIC and SAMBBA Aircraft Campaigns. Doctoral thesis, University of East Anglia.

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Identification and monitoring of halocarbons in the atmosphere remains important for the purposes
of regulation and prediction of stratospheric ozone depletion. Measurements of these and other
compounds have created a demand for techniques that improve the number of atmospheric
compounds analysable. A prototype time-of-flight gas chromatography-mass spectrometer (GCMS)
was characterised for atmospheric measurements. Instrument performance was found to be
at the lower end of expectations. A comparison to a quadrupole GC-MS indicated that the TOF
GC-MS would be suitable for measurements in polluted environments.
As part of this comparison, a number of halocarbons were analysed in London, U.K. as
part of the ClearfLo campaign. HCFCs were found at higher concentration than their Northern
Hemispheric (NH) baseline values. Furthermore, HFC-134a and HFC-227ea were almost double
their NH baseline. CH2Cl2, C2Cl4 and C2HCl3 were encountered at high concentrations and
sources of very short-lived bromomethanes (VSLB) were identified close to London.
As part of the CARIBIC project, five VSLB were measured in the mid-latitude upper troposphere/
lower stratosphere and tropical troposphere. Higher mixing ratios were encountered over
Southeast Asia, likely due to a locally longer CH2Br2 lifetime. Total bromine derived from these
five VSLB is at the lower end of the quantity required to balance the stratospheric bromine budget.
During the SAMBBA project, biomass burning and natural sources of COS, methyl halides
and other halocarbons were assessed over Brazil. Methyl halide emissions from rainforest and
savannah fires were quantified. The Cerrado savannah was found to be a strong source of COS.
Regional biomass burning emission estimates indicate that this is an important region for emissions
of these compounds. Terrestrial, natural sources of CH3Cl, CH3Br and CHCl3 were confirmed
over the Amazon rainforest. Emissions from a localised source of CHCl3 were identified and
wetlands or agricultural soil disturbance were hypothesised as a likely cause.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Users 2259 not found.
Date Deposited: 30 Jun 2015 13:50
Last Modified: 30 Jun 2015 13:50
URI: https://ueaeprints.uea.ac.uk/id/eprint/53425

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