Abstract of PhD Thesis

The measurement and analysis of C2-C8 non-methane hydrocarbons at Mace Head atmospheric research station, Ireland

Clare Noone (2005) - National University of Ireland, Galway

The determination of diurnal and seasonal natural emissions of C2-C8 non methane hydrocarbons (NMHC’s) in Ireland is currently of major uncertainty and forms the main research work of this thesis. So this research is deemed to be novel, is essential for the compilation of an ozone budget for Ireland, and provides important data for current and future air quality legislation. Observations of NMHCs are reported here for measurements observed at Mace Head for 2003, using an automated GC system developed by Martin, (2002).

Over the period January to December 2003, a seasonal cycle for the majority of the NMHCs was observed. On-site measurements were used in conjunction with air-mass origin classification, developed by Gray, (2002) to investigate photochemical ageing, atmospheric transport and the nature of source types affecting the sampling region. The relationship between isopentane and n-pentane, showed a possible oceanic source, while in the case of 2 & 3-methylpentane, the difference in ratios between European and North American air became apparent.

A novel approach to the estimation of biogenic emissions was investigated in this work. It is estimated that up to 90% of isoprene, 60% of ethene and 40% of propene emissions were biogenic in nature during 2003.

The comprehensive data set obtained during 2003 gave a unique opportunity to test the Polluted Air-mass Model (PAM), developed by Gray, (2002), providing a stringent test of emission inventories, model oxidation chemistry and model derived budgets from ozone. Overall, there was reasonably good agreement between modelled and measured data. Isoprene and ethene values for 2003 were several times higher than results from the PAM model, pointing to strong biogenic components that are not accounted for in the model.