城市绿地植物群落特征对亚微米颗粒物的影响

植物群落是构成城市绿地的基本单元之一,也是绿地发挥空气颗粒物调节功能的基础。亚微米级颗粒物,即PM1颗粒物对大气能见度、环境质量与人体健康等均存在严重的负面危害。为探究城市绿地植物群落对亚微米颗粒物水平的调节机制,本研究基于实地测量,针对不同类型植物群落内PM1颗粒物水平的差异,以及群落冠层结构对PM1浓度的影响开展定量研究。结果表明,植物群落对亚微米颗粒物具有一定的减滞效果。8种常见群落类型中,针阔-乔草型群落减滞PM1颗粒物的能力最优,阔叶-乔灌草群落次之,针叶-灌草型群落最弱,但不同类型植物群落内部的PM1浓度差异并不显著。植物群落的冠层结构同PM1颗粒物间存在明显的非线性响应关系,部分冠层指标存在关键的拐点阈值。当冠层郁闭度大于75%,疏透度小于55%左右时,植物群落减滞PM1颗粒物的效果最佳。

Impacts of Plant Community Characteristics on Submicron Particles

Plant communities are basic components of urban green spaces, which play potent role in regulating air particle levels. Submicron particles have serious negative effects on air visibility, environmental quality and human health. Understanding the regulation mechanism of plant communities on submicron particles may better facilitate the mitigation of submicron particles (PM₁) pollution through the construction of urban green spaces. Based on field investigations, differences in the daily PM₁ level among eight plant community types were quantitatively analyzed, and correlations between daily PM₁ and various canopy parameters, including canopy density (CD), canopy porosity (CP), leaf area index (LAI) and sky view factor (SVF) were further established to detect critical thresholds. Results shows that plant community has a certain effect on reducing submicron particles, but there is no significant difference in daily PM₁ level among different community types in summer. Among the eight plant community types, mixed trees and grasses type may most effectively reduce PM₁, followed by broad-leafed trees, shrubs and grasses type, while conifer shrubs and grasses type has the weakest effect. The responses of daily PM₁ to various canopy characteristics are complicated, featuring non-linear relationships with critical thresholds. Plant communities with CD greater than 75% and CP less than 55% have outstanding effects on reducing submicron particles.