Comparison of Trees' Leaves Capability to Deposit Air Suspended Particles Using Scanning Electron Microscopy (SEM) Analysis

Subject Areas : Air Pollution

sara abbasi ¹ , Seyed Mohsen Hosseini ² , Nematollah Khorasani ³ , Abd al-Reza Karbasi ⁴

1 - Faculty of Environment and Energy, Science and Research Branch, Tehran Islamic Azad University, Theran, Iran
2 - Faculty of Natural Resources &Amp, Marine Sciences, Tarbiat Modares University (TMU), Noor, Mazandaran, Iran *(Corresponding Author)
3 - Faculty of Environmental Studies, Tehran University, Iran
4 - Faculty of Environment, University of Tehran, Iran

Received: 2017-11-29 Accepted : 2021-03-15 Published : 2021-05-22

Keywords: Air Suspended Particles, trees' leaves, Energy-dispersive X-ray spectroscopy, electron microscope,

Abstract :

Background and Objective: In this study, the characteristics of particles deposited on the surface of the leaves of species of Platanus orientalis, Ulmus carpinifolia, Robinia pseudacasia, Morus alba, and Fraxinus excelsior in the sideline of one of the crowded streets of Tehran (around Azadi Square) were investigated using scanning electron microscopy(SEM)and energy dispersive X-ray analysis.Method: A base was selected from each tree species. The tree bases were safe and next to each other on the sideline of a high-traffic street. The canopy of the trees was separated from each other. Healthy leaves were placed from a height of 2 to 2.5 meters above the ground surface from the outermost part of the canopy of trees on the street side. Samples were prepared in the laboratory for imaging with electron microscopy of the surfaces of leaves. More than 50 particles were investigated by elemental detector analysis. The mass percentage of the elements of each particle was recorded. The equivalent diameter for each particle that its image had been prepared by SEM-EDX was measured manually in ImageJ software. The leaves were prepared using an image scanner in Jpg format and the area of ​​the leaves was determined by Image J software. The weight of the particles sequestrated on the leaves of each tree was also weighed.Findings: the weight of deposited particles was measured and the leaves' capability of different species of tress to deposit particles was compared. This study is one of the few ones on elemental analysis of individual particles in Iran and it is the first time that the deposited particles on the leaves of trees are studied through this method. Twenty-one elements were detected in particles. Carbon, Oxygen, Iron, and Silica had the highest mass frequency and Carbon, Calcium, Silica, Oxygen, Iron and Potassium had the highest percentage of presence in particles. Particles less than 2.5 micrometers in diameter were the most abundant ones. Metal particles with a diameter between 2.5 to10 micrometers were the most abundant metal particles that were observed. The mean comparison of the diameter of deposited particles on the leaves of tress showed no significant difference between them. Particles' diameter was higher in Platanus orientalis, Morus­ alba, Fraxinus excelsior, Robinia pseudacasia and Ulmus carpinifolia, respectively. The highest rate of deposited particles on the leaf surface belonged to Platanus orientalis, Ulmus carpinifolia, Fraxinus excelsior, Robinia pseudacasia and Morus alba, respectively.Discussion and Conclusion: Leaf area, cracks, leaf surface roughness, wax, veins, and leaf shape have an effective role in changing the properties of deposited particles on the surface of the trees' leaves.

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