Investigating the Formation of Organic Nitrogen Species during the Atmospheric Oxidation of Volatile Organic Compounds

Particulate matter less than 2.5 µm in diameter, termed PM2.5, lies within the respirable size range for humans and is therefore considered an important air quality standard. Within the respirable and often toxic chemical constituents in PM2.5 exist a range of organic nitrogen (ON) compounds. Atmospheric ON is difficult to characterize due to its various complexities; it spans a wide range of volatilities and polarities and originates from both biogenic and anthropogenic sources. This thesis details the use of two-dimensional gas chromatography (GC×GC) coupled to nitrogen chemiluminescence detection (NCD) for the analysis of ON compounds in atmospheric aerosol.
The development of a highly sensitive analytical technique, relying on GC×GC-NCD, allowed for time-resolved measurements of carcinogenic nitrosamines in urban ambient PM2.5 to be made. The total nitrosamine concentrations in London exceeded the public health recommendations, prompting an estimation of the lifetime cancer risk from exposure to nitrosamines via inhalation to be made.
The GC×GC-NCD technique was also used to investigate the formation of carcinogenic nitrosamines and nitramines formed during the atmospheric degradation of amines relevant to CO2 capture. Implementation of amine-based CO2 capture technology results in small but significant amounts of amines being emitted to the atmosphere. The atmospheric photo-oxidation pathways of various amines were investigated during a series of chamber experiments at the European Photoreactor. Complementary techniques such as ion chromatography (IC) were also used, to monitor the formation of aminium nitrate salts for
example.
Later work in this thesis includes the use of IC to characterise water-soluble ions in aerosol on the East coast of Peninsular Malaysia, and to study the influence of highly industrialised regions on aerosol composition at rural coastal locations. Additionally, GC×GC coupled to time-of-flight mass spectrometry (TOF-MS) was used as part of a collaborative project focusing on the composition of gas and particle phase cooking emissions.