Wei Wen-Jun, Wang Bing, Niu Xiang
Key Laboratory of Forest Ecology and Environment of National State Forestry and Grassland Administration, Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing 100091, China.
Liaoning Academy of Forestry, Shenyang 110032, China.
Huan Jing Ke Xue. 2020 Jul 8;41(7):3136-3147. doi: 10.13227/j.hjkx.201912264.
As the most important carrier of atmospheric particles captured by plants, the differences in micromorphology characteristics and leaf roughness are important determinants of particle capture capacity. Leaf micromorphology usually changes with growth (internal factor), and with environmental pollution intensity (external factor). The existing dust-spray simulation was always short; however, the leaf micromorphology changes had a clear delayed response, and therefore its results could not reflect the micromorphology changes caused by internal and external factors that influence the particulate capture capacity of leaves. In the present study, new and old leaves were used to study leaf growth, and different pollution source conditions were selected to study pollution intensity under natural conditions, to analyze the changes in leaf surface micromorphology and their impacts on particulate capture capacity. It was found that the amounts of TSP, PM, PM, and PM on the old leaves of three evergreen trees ( var., , and ) were higher than those of the new leaves, and the amounts of the particles with respect to the old leaves increased with leaf growth. Moreover, there were significant differences between the new and old leaves regarding the captured amount of different-sized particles. The increase in needle roughness (Rq) of the three evergreen trees, caused by growth, was the main factor that led to an increase in particle capture capacity for old leaves. The TSP and PM captured amounts of , , , , and were higher in the heavily polluted area than in the clean area. The amounts of PM and PM captured by , , and in the heavily polluted area were higher than those in the clean area; however, the amounts of PM and PM captured by and in the clean area were higher than those in the heavily polluted area. Pollution intensity very significantly affected the capture capacity of TSP, PM, and PM by leaves, as well as significantly affecting the capture capacity of PM. This was mainly caused by the leaf micromorphology changes found in the heavily polluted area, such as stomatal index decrease, waxy layer degradation, more irregular surface texture and boundaries of the epidermal cells, and longer and hardened trichomes. These changes caused the Rq values to be generally higher in the heavily polluted area than in the clean area, and the roughness of the abaxial surface increased more notably than that of the adaxial surface. These results will provide data support for further revealing the driving factors of particulate matter capture capacity of leaves and proposing more scientific urban forest management measures to improve their particulate matter removal function.
作为植物捕获大气颗粒物的最重要载体，叶片微观形态特征和叶片粗糙度的差异是颗粒物捕获能力的重要决定因素。叶片微观形态通常随生长（内部因素）以及环境污染强度（外部因素）而变化。现有的喷尘模拟时间总是较短；然而，叶片微观形态变化具有明显的延迟响应，因此其结果无法反映影响叶片颗粒物捕获能力的内部和外部因素所导致的微观形态变化。在本研究中，利用新叶和老叶研究叶片生长，并选择不同污染源条件研究自然条件下的污染强度，以分析叶片表面微观形态变化及其对颗粒物捕获能力的影响。研究发现，三种常绿乔木（ 变种、 、 ）老叶上的总悬浮颗粒物（TSP）、细颗粒物（PM）、可吸入颗粒物（PM）和超细颗粒物（PM）含量均高于新叶，且老叶上的颗粒物含量随叶片生长而增加。此外，新叶和老叶在不同粒径颗粒物的捕获量方面存在显著差异。三种常绿乔木因生长导致的针叶粗糙度（Rq）增加是老叶颗粒物捕获能力增加的主要因素。在重污染区域， 、 、 、 、 的TSP和PM捕获量高于清洁区域。 、 、 在重污染区域捕获的PM和PM量高于清洁区域；然而， 和 在清洁区域捕获的PM和PM量高于重污染区域。污染强度对叶片捕获TSP、PM和PM的能力有极显著影响，对PM的捕获能力也有显著影响。这主要是由重污染区域发现的叶片微观形态变化引起的，如气孔指数降低、蜡质层退化、表皮细胞表面纹理和边界更不规则以及毛状体更长且变硬。这些变化导致重污染区域的Rq值总体上高于清洁区域，且叶片背面粗糙度的增加比正面更显著。这些结果将为进一步揭示叶片颗粒物捕获能力的驱动因素以及提出更科学的城市森林管理措施以提高其颗粒物去除功能提供数据支持。
