Exploring the interplay between particulate matter capture, wash-off, and leaf traits in green wall species

Mamatha Tomson; Prashant Kumar; K V Abhijith; John F Watts

doi:10.1016/j.scitotenv.2024.170950

Exploring the interplay between particulate matter capture, wash-off, and leaf traits in green wall species

Sci Total Environ. 2024 Apr 15:921:170950. doi: 10.1016/j.scitotenv.2024.170950. Epub 2024 Feb 14.

Authors

Mamatha Tomson¹, Prashant Kumar², K V Abhijith³, John F Watts⁴

Affiliations

¹ Global Centre for Clean Air Research (GCARE), School of Sustainability, Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, Surrey, United Kingdom; Centre for Atmospheric Chemistry, School of Earth, Atmospheric and Life Sciences, University of Wollongong, Northfields Ave, Wollongong, NSW 2522, Australia.
² Global Centre for Clean Air Research (GCARE), School of Sustainability, Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, Surrey, United Kingdom; Institute for Sustainability, University of Surrey, Guildford GU2 7XH, Surrey, United Kingdom. Electronic address: P.Kumar@surrey.ac.uk.
³ Global Centre for Clean Air Research (GCARE), School of Sustainability, Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, Surrey, United Kingdom.
⁴ School of Mechanical Engineering Sciences, University of Surrey, Guildford GU2 7XH, Surrey, United Kingdom.

PMID: 38360301
DOI: 10.1016/j.scitotenv.2024.170950

Abstract

The study investigated inter-species variation in particulate matter (PM) accumulation, wash-off, and retention on green wall plants, with a focus on leaf characteristics. Ten broadleaf plant species were studied in an experimental green wall. Ambient PM concentrations remained relatively stable throughout the measurement period: PM₁: 16.60 ± 9.97 μgm^-3, PM_2.5: 23.27 ± 11.88 μgm^-3, and PM₁₀: 39.59 ± 25.72 μgm^-3. Leaf samples were taken before and after three rainfall events, and PM deposition was measured using Scanning Electron Microscopy (SEM). Leaf micromorphological traits, including surface roughness, hair density, and stomatal density, exhibited variability among species and leaf surfaces. Notably, I.sempervirens and H.helix had relatively high PM densities across all size fractions. The study underscored the substantial potential of green wall plants for atmospheric PM removal, with higher Wall Leaf Area Index (WLAI) species like A.maritima and T.serpyllum exhibiting increased PM accumulation at plant level. Rainfall led to significant wash-off for smaller particles, whereas larger particles exhibited lower wash-off rates. Leaf micromorphology impacted PM accumulation, although effects varied among species, and parameters such as surface roughness, stomatal density, and leaf size did not consistently affect PM deposition. The composition of deposited particles encompassed natural, vehicular, salt, and unclassified agglomerates, with minimal changes after rainfall. Air Pollution Tolerance Index (APTI) assessments revealed that I.sempervirens displayed the highest air pollution tolerance, while O.vulgare had the lowest. APTI showed a moderate positive correlation with PM deposition across all fractions. The study concluded that the interplay of macro and micromorphology in green wall plant species determines their PM removal potential. Further research is needed to identify the key leaf characteristics for optimal green wall species selection for effective PM removal.

Keywords: Air quality; Green walls; Leaf micro-morphology; PM deposition; PM wash-off.

MeSH terms

Air Pollutants* / analysis
Air Pollution*
Environmental Monitoring
Particulate Matter / analysis
Plant Leaves / chemistry
Plants
Trees

Substances

Particulate Matter
Air Pollutants