Particulate matter pollution capture by leaves of seventeen living wall species with special reference to rail-traffic at a metropolitan station |
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| Institution: | 1. State Key Laboratory Incubation Base of Urban Environmental Processes and Digital Simulation, College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China;2. State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China;3. Public Meteorological Service Center, China Meteorological Administration, Beijing 100081, China;1. Ministry of Education Key Laboratory of Silviculture and Conservation, Beijing Forestry University, Beijing 100083, China;2. School of Environment, Henan Normal University, Key Laboratory for Yellow River and Huai River Water Environment and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, Xinxiang, Henan 453007, China;3. Henan Vocational College of Agriculture, Zhengzhou, Henan 451450, China;4. National Energy R&D Center for Non-food Biomass, Beijing 100083, China |
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| Abstract: | Atmospheric Particulate Matter (PM) constitutes a considerable fraction of urban air pollution, and urban greening is a potential method of mitigating this pollution. The value of living wall systems has received scant attention in this respect. This study examined the inter-species variation of particulate capture by leaves of seventeen plant species present in a living wall at New Street railway station, Birmingham, UK. The densities of different size fractions of particulate pollutants (PM1, PM2.5 and PM10) on 20 leaves per species were quantified using an Environmental Scanning Electron Microscope (ESEM) and ImageJ image-analysis software. The overall ability of plant leaves to remove PM from air was quantified using PM density and LAI (Leaf Area Index); any inter-species variations were identified using one-way Anova followed by Tukey’s pairwise comparison. This study demonstrates a considerable potential for living wall plants to remove particulate pollutants from the atmosphere. PM capture levels on leaves of different plant species were significantly different for all particle size fractions (P < 0.001). Smaller-leaved Buxus sempervirens L., Hebe albicans Cockayne, Thymus vulgaris L. and Hebe x youngii Metcalf showed significantly higher capture levels for all PM size fractions. PM densities on adaxial surfaces of the leaves were significantly higher compared to abaxial surfaces in the majority of the species studied (t-test, P < 0.05). According to EDX (Energy Dispersive X-ray) analysis, a wide spectrum of elements were captured by the leaves of the living wall plants, which were mainly typical railway exhaust particles and soil dust. Smaller leaves, and hairy and waxy leaf surfaces, appear to be leaf traits facilitating removal of PM from the air, and hence a collection of species which share these characters would probably optimize the benefit of living wall systems as atmospheric PM filters. |
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| Keywords: | Outdoor air pollution Urban green infrastructure Green walls Railway pollution |
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