University of Tasmania
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Investigation of the composition of woodsmoke and methods for apportioning woodsmoke to air pollution in Launceston

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posted on 2023-05-26, 09:24 authored by Jordan, TB
Launceston, a city with a population of approximately 80,000 located in the north of Tasmania, Australia, regularly experiences high levels of air pollution during winter. Ambient `PM_(10)` (particulate matter with an aerodynamic diameter smaller than 10 micrometres) levels exceed the Australian 24-hour guideline of `50` `˜í¬¿g``/``m^3` around 20-40 times during the May to September period each year. This is generally attributed to residential woodburning, with approximately one third of households using woodheaters or open fireplaces. This thesis reports on investigations into characterising and quantifying the contribution of woodsmoke to wintertime air pollution in Launceston. An historical record of air quality in Launceston was reconstructed using polycyclicaromatic hydrocarbons (PAHs) as surrogates for air pollution in a dated sediment core taken from the upper Tamar Estuary. The overall depth profile showed that levels of PAHs began increasing at the end of the 19th century and have been relatively steady since the 1930s. Pyrogenic source ratios similar to woodburning were found in both atmospheric and sedimentary samples, although quantification of the woodburning contribution was not possible using PAHs alone. Factors affecting atmospheric sampling of PAHs were investigated, including the impact of sampling rate, the vapour-particle phase distribution on various components of the sampling system and degradation caused by different filter media. Because of the inability of PAHs to differentiate between fossil fuel and wood combustion there was a need to identify alternative tracers for wood combustion. A dilution tunnel was used to collect emissions from woodheaters operated with different airflow settings, and around 100 organic compounds were quantified. Although the majority of compounds were not detected in ambient air samples, levoglucosan was found to be not degraded in the atmospheric samples and was identified as a consistent tracer for woodsmoke. Levoglucosan concentrations in ambient `PM_(10)` indicated that woodheaters contributed about 80% of wintertime air pollution in Launceston. To validate the use of levoglucosan as a tracer for woodsmoke, the contribution of biomass and fossil fuel sources of carbon to Launceston ambient aerosols was determined by measuring the carbon-14 content using accelerator mass spectrometry. Fossil sources had a relatively low and constant input irrespective of the particulate loading, consistent with transport-related emissions. Conversely, the biomass input, most likely from woodsmoke, was found to increase linearly with particulate loading, and contributed around 97-99% of the total organic carbon fraction of Launceston wintertime PM10. A modified combustion method was developed for samples collected on borosilicate filter media.


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Copyright 2005 the author

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