AbstractPrimary biological aerosol particles (PBAPs), otherwise commonly referred to as 'bioaerosols', are a subset of atmospheric aerosol particles that comprise pollen, fungal spores, bacteria, and viruses, and other biological matter suspended in the atmosphere. Whilst PBAPs are naturally produced, these particles play a fundamental role in the Earth system, influencing natural and agricultural ecosystems, potentially exacerbating animal and human diseases, and contributing to climate processes. However, a considerable lack of understanding remains concerning the pathways that these particles contribute to, owing to the difficulties in detecting and quantifying these particles. This thesis focuses on the detection and characterisation of PBAPs using a real-time online detection technique, known as ultraviolet light-induced fluorescence (UV-LIF) spectrometry. Whilst various UV-LIF spectrometers have been deployed for measurement campaigns in a range of geographic locations worldwide, studies quantifying classification performance and inter-comparisons of different UV-LIF spectrometers are limited. As such, there remain some considerable uncertainties in the detection abilities and consistency of these instruments, with consequent impacts on training algorithms for PBAP classification. Multiple UV-LIF spectrometers were deployed in both ambient measurement campaigns, and laboratory experiments. The initial ambient study, characterising and inter-comparing biofluorescent aerosol emissions from four sites in the UK indicated a similar dominance of wet-discharged fungal spores across most of the study sites, but illustrated the difficulties that currently exist when attempting to characterise these particles following collection by UV-LIF spectrometers. By conducting a laboratory UV-LIF inter-comparison study to assess instrument detection abilities, distinct fluorescent responses could not be identified between the different biological particle groups sampled (bacteria, fungal spores, and pollen). Differences in fluorescent responses were, however, identified between instruments which were nominally the same, and therefore it was suggested that due to these differences training data for supervised techniques is not cross-compatible between instruments. The final comparison study of UV-LIF spectrometers and offline, traditional measurement techniques, illustrated that these instruments are adept at detecting select fungal spores, and bacterial particles in ambient conditions. However, the results from using both unsupervised and supervised analysis techniques illustrated some continuing issues in distinguishing between these two particle groups when using UV-LIF spectrometers. By conducting both ambient and laboratory studies, and demonstrating the use of both unsupervised and supervised particle discrimination and characterisation methods, the findings in this thesis contribute towards an improved understanding of how different UV-LIF spectrometers respond to both known and unknown particle types. The results of which consequently highlight the impacts that this has for the application of different analysis techniques for PBAP characterisation.
|Date of Award||1 Aug 2021|
|Supervisor||Martin Gallagher (Supervisor) & David Topping (Supervisor)|
- Primary biological aerosol particles