Date of Award
Doctor of Philosophy
School of Science
Associate Professor Andrea Hinwood
Professor Will Stock
Dr Anna Callan
Field of Research Code
This study investigated the emission factors (EFs) for inorganic gases (CO2, CO, SO2, NO and NO2), carbonyls (formaldehyde, acetaldehyde, acetone, propionaldehyde, butyraldehyde and benzaldehyde), volatile organic compounds (VOCs) and particulate matter (PM2.5 and PM10) from laboratory-based fires of vegetation from five typical vegetation types of Western Australia. Species burnt were three grasslands (Spinifex represented by Triodia basedowii, Kimberley grass represented by Sehima nervosum and Heteropogon contortus, and an invasive grass represented by Ehrharta calycina (Veldt grass)), Banksia woodland and Jarrah forest under different combustion conditions. Chemical composition (water-soluble metals and polycyclic aromatic hydrocarbons – PAHs) and in vitro toxicity of PM2.5 were also measured. Vegetation samples were burnt in a ceramic chamber in varying combustion conditions altered by controlling the vegetation moisture content (<10%, 12–16% and 20–25%) and the air flow rate (0, 1.25 and 2.94 m.s-1). Burns of woodland (Banksia) and forest (Jarrah) had significantly higher EFs for CO, SO2 and PM2.5 compared with those from grassland (Spinifex). Emissions of temperate grass (Veldt) fires were significantly different from those of the tropical grass (Spinifex and Kimberley grasses), with lower EFCO2 and higher EFs for CO, carbonyls and PM2.5. EFs for SO2, NO and NO2 were variable between different vegetation types, indicating variation in the nitrogen and sulphur content of the fuels. The EFs for most carbonyls were similar between most vegetation types, with the exception of Veldt grass. Functions which may be useful to predict emissions of infrequently measured carbonyls (acetaldehyde, acetone and propionaldehyde) from the EF for formaldehyde, a commonly measured and reported substance, were also proposed. Fifteen VOCs were identified in the smoke, but concentrations were too low to be quantified. Benzene, toluene, styrene and indene were the most frequently detected VOCs.
Moisture content did not strongly influence the modified combustion efficiency (MCE) and EFs for gaseous pollutants, but significantly affected the EF for PM2.5 with higher emissions from burns of moister vegetation. Increasing the air flow rate significantly increased the emissions of most pollutants. However, combustion conditions did not strongly affect the PM2.5 chemical composition.
The MCE, EFs for CO and CO2 results in this study were similar to values reported from field measurements for similar vegetation types in Australia, indicating the applicability of these laboratory-based results. Emission factors were different to the profiles generated from vegetation fires in other parts of the world.
Toxicity of PM2.5 on human lung epithelial (A549) cells was assessed using cell viability and cytokine production measurements. Responses on cell viability were associated with K and Na concentrations in PM2.5, whilst the cytokine production of cells was more affected by the PM2.5-bound PAH, Al, Cu and Mn concentrations. Toxicity between vegetation types was different, which might be due to the differences in chemical composition of PM2.5. PM2.5 emitted from Jarrah burns appeared to have the highest toxicity on epithelial cells, followed by those from Banksia, Veldt grass and Spinifex. The findings of this study on toxicity of PM2.5 demonstrate the adverse impact on human health of particulate from bushfires and emphasise the importance of vegetation type on toxicological outcomes of bushfire-derived PM2.5.
The EFs obtained in this study can be used in models to estimate the emissions from bushfires in Australia, particularly Western Australia. Results on toxicity of PM2.5 provide information for relevant government agencies to preliminarily evaluate the risk to human health, especially for firefighters and communities in close proximity to bushfire events.
Dong, T. T. (2019). Chemical composition and toxicity of emissions from burning five vegetation types of Western Australia under experimental combustion conditions. https://ro.ecu.edu.au/theses/2180