Long-term monitoring of trace volatile organic compounds in ambient air of Western Australia by proton transfer reaction-mass spectrometry (PTR-MS)

[Truncated abstract] Volatile organic compounds (VOC) are a class of reactive trace species ubiquitous within the Earth's lower atmosphere, being emitted from anthropogenic and biogenic sources both locally and globally. VOC are involved in numerous documented atmospheric issues, including photochemical production of ozone and formation of secondary organic aerosol (SOA) in the troposphere. Measuring of VOC concentration and speciation under ambient conditions is pivotal for producing informed environmental and health guidelines, for defining emissions controls strategies, to assess ecosystems response, and ultimately to advance scientific understanding of the atmosphere. This thesis describes the monitoring of VOC concentrations in real time (on-line) and for long-term (several months across three years) in ambient air of two representative locations of Western Australia: the central business district of Perth – the State capital city – and the rural village of Yarloop, in the proximity of an isolated alumina refinery about 100 km south of Perth. The ambient levels (ppb) of tens of VOC where monitored by means of Proton Transfer Reaction-Mass Spectrometry (PTR-MS). This chemical ionization mass spectrometric technique allows for highly time-resolved VOC concentration measurements, however, with the disadvantage of providing chemical identity cues limited to the molecular weight of the compound. To partly address this shortcoming, parallel VOC measurements were performed by means of the US EPA toxic organic compound measurements protocols (US EPA TO). These off-line methods provide detailed chemical identity of a several VOC, although with limited temporal resolution.