Green wall technology for sustainably improving environmental quality: Investigations into green wall plant health and particulate deposition

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Air pollution is of significant concern, affecting millions of people globally. Plants are effective air pollution remediators; certain species, however, may exhibit higher removal capacities. Additionally, due to the continual pollution exposure, some species may exhibit sensitivity to pollution and will thus be ineffective for use in 𝘪𝘯 𝘴𝘪𝘵𝘶 applications. This thesis assessed the particulate matter removal capacity of common green wall species used in 𝘪𝘯 𝘴𝘪𝘵𝘶 applications over a 6 month duration. High accumulating species were then identified, and leaf traits associated with enhanced particulate matter accumulation assessed. Leaf traits were not found to be exclusively related to enhanced particulate matter deposition; with small linear leaved species exhibiting the lowest particulate accumulation. The health of the green wall species from pollution exposure was then assessed. Most species did not encounter any significant differences among their health variables between polluted test sites and control glass house conditions, indicating their suitability for use 𝘪𝘯 𝘴𝘪𝘵𝘶. The particulate matter removal capacity of 𝘪𝘯 𝘴𝘪𝘵𝘶 Sydney green walls was then examined. To do this, air quality tests were conducted in front of green walls and matched reference walls across the test sites. There were no significant differences observed for ambient particulate matter concentrations between green wall and reference wall sites, perhaps due to the ‘passive’ nature of the green wall systems tested. There was also no significant difference observed between the wall types for proximal temperature conditions, but there was a significant difference for ambient noise reduction, with green walls having significantly lower noise conditions. Lastly, the pollutant removal capacity of Australian native species used in active green walls was assessed. Active native green walls were effective at reducing benzene, with similar removal efficiencies to previously tested ornamental species. They were also capable of removing particulate matter, however at lower efficiencies than ornamental species. Native plant active green walls were inefficient for carbon dioxide removal. The results of this thesis highlight the importance of species selection for maximum pollutant removal efficiency and the capacity for vegetation to have positive impacts on ambient conditions. The results also indicate improvements that can be made to green wall systems for a higher efficiency for 𝘪𝘯 𝘴𝘪𝘵𝘶 applications, including the conversion of passive systems to active systems and the inclusion of select species for increased removal efficiency and tolerance to pollution exposure.
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