The Characteristics Of Leaf Particulate Matter Among Trees With Different Diameters At Breast Height And Tree Canopy

Airborne particulate pollution is one of the major environmental problems at present.Trees can improve the atmospheric environment by intercepting airborne particles.It is of great significance to understand the mechanism of trees interception of dust and production by studying the variations of leaf particulate matter among trees with different diameters at the breast height and the spatial variations of leaf particulate matter in the canopy.In this study,we collected leaf samples from trees with different diameters at breast height and different canopy height of trees.The leaf particulate matter retention amount and particle size distribution were measured.The main conclusions were:1)The DHB showed no significant effects on leaf particulates retention per unit leaf surface,but had significant impacts on particulates retention per single tree.The DHB which can capture more particulates was 12.8²5.5 cm.The maximum captured PM_2.5,PM₁₀ and TSP were 5.77 g/plant,12.88 g/plant and 43.08 g/plant per single tree,respectively.2)Retention capacity of PM_2.5 per unit leaf area showed significant differences among different species.The amounts of particulate matter captured by tested species on per unit leaf area ranged as follows: Pinus tabuliformis > Sophora japonica > Ginkgo biloba > Salix babylonica > Fraxinus chinensis > Populus tomentosa.Retention capacity of PM_2.5 per plant was in the order of Sophora japonica > Populus tomentosa > Pinus tabuliformis > Salix babylonica > Ginkgo biloba > Fraxinus chinensis.From these results,we can conclude that assessment of the retention capacity of PM_2.5 by plants should be based on multi-scale comparisons.3)PM_2.5,PM₁₀ and TSP retention amounts of lower leaves were greater,while higher leaves was smaller.The larger values of TSP retention amount are concentrated in the inside and the outside.While,the PM₁₀ retention amount was on the contrary,the higher values observed for the middle and the outside leaves.The larger PM_2.5 retention amount was concentrated in the middle canopy.4)There existed two peak values of the foliar dust for the investigated species,with its peak values of the dust size being different along the canopy.There existed three peaks of the foliar dust collected from the inner canopy,but two peaks for the samples collected from the middle and outer canopy.The peak values decreased along the variations of inner,middle and outer canopy.