Roadside Moss Turfs in South East Australia Capture More Particulate Matter Along an Urban Gradient than a Common Native Tree Species

Abstract

Urbanisation largely consists of removing native vegetation. Plants that remain interact with air quality in complex ways. Pollutants can be detrimental to plant growth; plants sometimes reduce air quality, yet some species also improve it through phytoremediation. A common pollutant of concern to human health in urban areas is particulate matter (PM), small particles of solid or liquid. Our study compared roadside moss turfs with leaves of a common Australian tree species, Pittosporum undulatum, in their ability to capture PM along an urban gradient. We sampled nine sites, three in each of three levels of urbanisation: low, medium, and high according to road type (freeway, suburban road, quiet peri-urban road). In addition, we deployed a PM monitor over a two-week period in one site of each urban level to provide concentrations of PM2.5. We used chlorophyll fluorescence (Fv/Fm; maximum quantum yield of photosystem II) as a measure of plant stress. We extracted PM in three size fractions using a filtration and washing technique with water and chloroform. Site averages for moss turfs were between 5.60 and 33.00 mg per g dry weight for total PM compared to between 2.15 and 10.24 mg per g dry weight for the tree leaves. We found that moss was more sensitive to increasing urbanisation, both in terms of trapping proportionately more PM than the leaves, and also in terms of photosynthetic stress, with moss Fv/Fm declining by a site average of 40% from low to high urban “class” (0.76 to 0.45). Our study highlights the stressors potentially limiting moss persistence in cities. It also demonstrates its ability to trap PM, a trait that could be useful in urban applications relating to urban greening or air quality.

Usefulness of Tree Species as Urban Health Indicators

“…Based on the APTI values, we demonstrated that A. saccharinum was moderately tolerant, while P. acerifolia was intermediate. Alotaibi et al [34] reported that the reduction of leaf area was significantly recorded in contaminated areas for P. acerifolia. These findings suggest that the differences in the reduction in leaf areas between tree species at different locations may be due to the availability of leaf surface area and the capacity of leaves for capturing air pollutants [35].…”

Differences in Airborne Particulate Matter Concentration in Urban Green Spaces with Different Spatial Structures in Xi’an, China

“…However, in the open green spaces dominated by lawns, the settling effect of airborne particulate matter in the air was less hindered, and the airborne particulate matter directly settled on the ground due to the effect of gravity [51]. In addition, mosses showed a higher capability of trapping atmospheric particulate matter than certain trees [52]. Therefore, different vegetation structures had different distributions of airborne particulate matter at different heights of vegetation.…”

Phyto-Cleaning of Particulate Matter from Polluted Air by Woody Plant Species in the Near-Desert City of Jodhpur (India) and the Role of Heme Oxygenase in Their Response to PM Stress Conditions

“…However, the ability to capture PM on leaves is strongly linked to the characteristics of the species (Jouraeva et al 2002;Saebø et al 2012). Plant shape and porosity (Leonard et al 2016), leaf surface morphology, the complexity of the layer of cuticular waxes, the arrangement of stomata and the presence of trichomes on leaves Haynes et al 2019;Prusty et al, 2005) are very important. Urban greenery is able to remove signi cant amounts of pollutants from the air in cities (Kroeger et al 2018;Pugh et al 2012;Vailshery et al 2013;Yang et al 2005), and therefore air phytoremediation is becoming increasingly popular worldwide, especially as it does not involve any tangible costs (Paton-Walsh et al 2019).…”