PM10 and PM2.5 Dust-Retention Capacity and Leaf Morphological Characteristics of Landscape Tree Species in the Northwest of Hebei Province

Abstract

This study aimed to explain the reasons for the differences in the PM_2.5 and PM₁₀ dust-retention capacity of different tree species. Ten typical landscape tree species with a strong ability to adsorb particulate matter and improve the quality of the atmospheric environment were selected in Zhangjiakou, and the leaves of each tree species were collected from April to October. The PM_2.5 and PM₁₀ dust-retention capacity of different tree species were measured using an aerosol regenerator. The differences in the leaf structure of different tree species were analyzed using an electron microscope. The results showed that the PM₁₀ and PM_2.5 per unit leaf area of 10 tree species ranged from 1.31 ± 0.68 to 2.64 ± 1.29 μg·cm⁻² and from 0.28 ± 0.13 to 0.99 ± 0.34 μg·cm⁻², and the PM₁₀ and PM_2.5 dust-retention capacity per unit leaf area of coniferous trees was higher than that of broad-leaved trees. Further, the PM₁₀ dust-retention capacity per unit leaf area of each tree species in different months was the highest in October (3.17 ± 1.12 μg·cm⁻²) and the lowest in August (0.79 ± 0.56 μg·cm⁻²). The PM_2.5 dust-retention capacity per unit leaf area was the highest in October (0.99 ± 0.34 μg·cm⁻²) and the lowest in April (0.28 ± 0.13 μg·cm⁻²). The annual PM₁₀ and PM_2.5 dust-retention capacity per hectare of Pinus tabulaeformis was the highest and that of Ginkgo biloba was the lowest. The conifer trees have rough leaves, and broad-leaved trees have smooth leaves. The leaves of P. tabulaeformis and Picea asperata have a widespread stomata distribution, and the leaf surface is not smooth, with a large number of grooves and bulges. The number of stomata on the leaf surface of Salix babylonica and G. biloba is less than that of P. tabulaeformis and P. asperata. When the dust-retention capacity of PM_2.5 per unit leaf area is high, the corresponding roughness is also significant, and a good logarithmic relationship exists between roughness and PM_2.5 per unit leaf area (R² = 0.9504). The results of this study might have an important reference value in terms of the selection of tree species with strong PM₁₀ and PM_2.5 dust-retention capacity and the improvement in ambient air quality in the northwest of Hebei Province.