Particulate matter deposition on roadside plants and the importance of leaf trait combinations

- Hair presence and leaf shape but not leaf arrangement influence particulate deposition on urban plants.
- Metals within particulate reveal source apportionment including vehicle exhaust and tire and road wear particles.
- Urban plantings should consider interspecific differences in leaf traits and leaf trait combinations in model estimates of particulate deposition.

Road and vehicle use in urban environments are key contributors to urban air pollution and increase concentrations of carbon monoxide, polyaromatic hydrocarbons and particulate matter (particles <100 μm diameter). Plants, which can intercept these pollutants, are increasingly recognised as practical mitigation methods to reduce ambient pollution, especially adjacent roadsides. We quantified particulate matter loads in 16 common native species along Sydney roadsides and linked findings to leaf traits. For each species, we tagged individuals within the first 2 m of road edges and recorded leaf area, shape and arrangement, also noting the presence of leaf hairs. We then quantified particulate matter loads deposited in each sample over three months and, for two morphologically distinct species, Acacia parramattensis and A. longifolia, the composition and concentration of metals in deposited particulate matter. We found particulate deposition varied according to species and leaf shapes but not sample months and, those species with leaf hairs accumulated significantly more particulate matter. Furthermore, we found metals associated with vehicle use including copper, chromium and manganese in collected particulate matter. Ultimately, our results highlight the importance leaf trait combinations can have in affecting particulate matter deposition.