Quantification of oxygenated volatile organic compounds (OVOCs) in seawater

• Main Author: Beale, Rachael
• Published: University of East Anglia 2011
• Subjects: 551.466
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551143

Oxygenated Volatile Organic Compounds (OVOCs) are low molecular weight (Cl-C3 compounds), volatile species that include alcohols, aldehydes and ketones. They are ubiquitous throughout thetroposphere where they alter the oxidative capacity of the atmosphere and influence the global ozone budget. The role of the ocean in the cycling of OVOCs remains largely unanswered due to a paucity of water measurements. Thisis . partly due to analytical difficulties in extracting these labile species from solution. Their presence at trace (nanomolar) concentrations and their high solubility makes efficient extraction from solution challenging. This thesis reviews the global importance and the current understanding of the OVOCs and highlights the uncertainty created from a paucity of oceanic measurements. It also details the available analytical capabilities for analysing these species, both in air and water to provide a platform from which to start method development. Developmental work was undertaken in order to design and validate two separate analytical techniques for the extraction of OVOCs from seawater: I) A Membrane Inlet - Proton Transfer Reaction / Mass Spectrometer (MI-PTRlMS) was optimised for the quantification of methanol, acetaldehyde and acetone in seawater, 2) a Purge andTrap- Gas Chromatography / Flame Ionisation Detection (P&T-GCIFID) system was developed for the extraction of ethanol, l-propanol, 2-propanol, propanal, acetone and acetaldehyde. Their independent capabilities are discussed as well as the advantages of their simultaneous use to provide maximum information regarding OVOC content within a sample. These techniques were deployed on two research cruises to as~ess the importance of an upwelling region and also to determine the spatial variability of both the concentration and flux of OVOCs in the Atlantic Ocean. The methods that have been developed during this research have increased the available data on OVOC concentrations in seawater and have shown that the ocean is important in the cycling of these trace gases.