Atmospheric particulate matter (PM) emission from overpasses is serious. To optimize the solution of planting design in the overpass, it is essential to understand the plant's ability to capture PM. In this study, leaf samples were collected from 11 plant species commonly existing in five overpass greening areas in Changsha, China. The PM retention per unit leaf area (Mleaf), PM retention on a unit greening land (Mland), and leaf surface microstructure were measured and analyzed. Results showed that the Mleaf of Ophiopogon japonicus (1.59 g/m2) exhibited the highest value, and that of Nandina domestica (0.23 g/m2) was the lowest value. The Mland of O. japonicus, Fatsia japonica, and Magnolia grandiflora was the highest based on the leaf area index. Leaves with wide gullies and cuticular wax significantly affected the PM retention ability of plants. Plant height played an important role in the PM retention ability in the overpass. Multilayered canopy structures such as arbor-shrub-herb had great potential for PM retention in overpasses. Based on the results, a PM retention design scheme of overpass greening space was proposed. This study provided an optimal solution for providing critical insights and guidance for developing effective PM reduction strategies in urban overpass environments.
Keywords: Particulate matter; planting design of overpass; retention.
The complex structure of the overpass leads to the most serious air pollution with high source emissions and particulate matter (PM) concentrations. However, the study of plant PM retention in overpass greening is still insufficient. This study demonstrated that the PM retention ability of plant species is correlated with leaf surface microstructure, leaf area index, and plant height. Multilayered canopy structures such as arbor–shrub–herb had great potential for the PM retention in overpasses. The PM retention design pattern of greening plants for overpasses was proposed by optimizing the selection of plant species. This study aimed to provide theoretical knowledge for scientific overpass attached greening design and ideas and references for urban green space design in PM reduction.