Study on Capturing PM2.5 Capability of Tree Species in Different Functional Areas

Abstract

Trees can capture PM on account of their foliage’s structure, thus, improving air quality. We determined leaf PM-retaining capability (PM2.5, PM>2.5, PM) of evergreen shrub (Euonymus japonicas) and decicuous trees (Sophora japonica, Fraxinus chinensis, Ginkgo biloba, Populus tomentosa) in different functional areas. The leaf micromorphological structure was observed using a field emission environmental scanning electron microscopy. We found that E. japonicas should be planted in traffic and industrial areas, while S. japonica, G. biloba, F. chinensis should be chosen as complementary in clean areas. S. japonica, G. biloba were adapted well to polluted environment, but, F. chinensis was not. KEYWORD: CAPTURING PM2.5; DIFFERENT FUNCTIONAL AREAS; structural feature International Conference on Industrial Technology and Management Science (ITMS 2015) © 2015. The authors Published by Atlantis Press 585 deciduous trees was about 2.5 m, and that of evergreen shrub was about 1.0 m. All sample trees were not suffering from obvious pests or diseases. During the experiment, samples were stored at 4°C in fridge. 2.2.2 Analysis of PM For each tree species, three batches of test material were prepared. And for each batch, 50-60 leaves were selected. The leaves were washed with a brush. The total hemi-surface leaf area was measured using Image J software (Version 1.46; National Institutes of Health, USA) after scanned (HP Scanjet 3570c, Japan). As for the filtration procedure, we used filter membranes with the pore of 2.5 μm, these filter membranes were pre-weighed after 24 h drying at 40°C using a balance with 0.1 mg accuracy (SI-114, Denver Instrument, USA). Particles in filter membranes was PM>2.5 (particles with diameter greater than 2.5 μm). In addition, filtered filtrate were dried to constant weight with baker immediately, thus, only PM2.5 was left. The resulting weight was finally divided by leaf area. We obtained the weight of deposited PM>2.5 and PM2.5 per unit leaf area for each washed leaf sample. PM was the sum of PM>2.5 and PM2.5. 2.2.3 Analysis of leaf surfaces characteristics For each of the specie, three leaves were randomly selected, and cut into 5 mm × 5 mm samples from different parts of the leaf avoiding main vein. Then the samples were adhered to the aluminum tube using double-sided adhesive tape. The field emission scanning electron microscope (FESEM, Quanta 200, FEG, USA) was used to observe the upper and lower leaf surfaces characteristics.