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刘辰明,张志强,陈立欣,邹瑞,张璐,高源,李冬梅.降雨对北方城市5种典型城市绿化树种叶面滞尘的影响.生态学报,2018,38(7):2353~2361 本文二维码信息
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降雨对北方城市5种典型城市绿化树种叶面滞尘的影响
Impacts of rainfall on leaf PM (airborne particulate matter) detention in five commonly used urban tree species in northern China
投稿时间:2017-04-21  修订日期:2017-11-16
DOI: 10.5846/stxb201704210726
关键词大气颗粒物  PM2.5  树种  滞尘  降雨冲刷
Key Wordsatmospheric particulates  PM2.5  tree species  foliar dust retention  rainfall effected dust removal
基金项目国家林业公益性行业科研专项(20130430103);北京市教育委员会科学研究与研究生培养共建项目
作者单位E-mail
刘辰明 北京林业大学水土保持学院, 教育部水土保持与荒漠化防治重点实验室, 北京 100083  
张志强 北京林业大学水土保持学院, 教育部水土保持与荒漠化防治重点实验室, 北京 100083 zhqzhang@bjfu.edu.cn 
陈立欣 北京林业大学水土保持学院, 教育部水土保持与荒漠化防治重点实验室, 北京 100083  
邹瑞 北京林业大学水土保持学院, 教育部水土保持与荒漠化防治重点实验室, 北京 100083  
张璐 北京林业大学水土保持学院, 教育部水土保持与荒漠化防治重点实验室, 北京 100083  
高源 北京林业大学水土保持学院, 教育部水土保持与荒漠化防治重点实验室, 北京 100083  
李冬梅 北京林业大学水土保持学院, 教育部水土保持与荒漠化防治重点实验室, 北京 100083  
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摘要:
城市树木和森林植被净化大气颗粒污染物的功能受到了广泛的重视,但由于受多种植被特征与环境因素的影响,定量评价城市植被净化大气颗粒污染物功能非常困难。研究了不同降雨条件下大叶黄杨、银杏、栾树、五角枫、杜仲5种我国北方城市绿化典型树种叶面滞尘量的变化特征。在选定的样树冠层分上、中、下3层和东、南、西、北4个方向,采集成熟叶片,采用刷洗样本叶表,抽取水样及分级抽滤并烘干称重的方法,测定这5种树种降雨后12d(夏季累积滞尘量)、14mm降雨后(小雨)、29mm降雨后(中雨)以及室内模拟降雨30mm/h(15mm雨量)后叶片表面不同粒径大气颗粒污染物的滞留量。研究结果表明:降雨对不同粒径颗粒物去除能力有较大差异,除银杏以外,PM > 10以上颗粒物更容易去除;小雨对颗粒物的冲刷能力有限;中雨可以冲刷掉50%以上总颗粒物;室内模拟强降雨可以冲刷掉90%以上颗粒物,随着降雨增大,各粒径颗粒物随之冲刷量增加;同时叶表结构对抗冲刷能力有显著影响,革质叶片更容易滞尘及冲刷,绒毛结构滞尘能力较低,抗冲刷能力较强;北方大叶黄杨具有综合去除空气中颗粒物优势(小雨TSP冲刷量为(775.06±33.99)mg/m2),银杏具有去除细颗粒物优势(中雨PM2.5冲刷量为(426.55±40.83.99)mg/m2)。
Abstract:
It is widely acknowledged that urban trees and forests can significantly improve air quality by removing airborne particulate matter (PM) and thus safeguard the health of urban residents. However, it is very difficult to accurately assess the ability of tree species to capture PMs from the air as such processes are governed by several biotic and abiotic factors. Here, we present a first ever study that explores the effects of rainfall on the detention of PMs by leaves in five commonly used urban greening species in northern China, including Ginkgo biloba, Acer mono Maxim, Euonymus japonicus, Koelreuteria paniculata, and Eucommia ulmoides. Our specific objectives were to:1) quantify how much PMs detained on the leaves of five different tree species can be washed off by natural and simulated rainfall events, 2) compare the difference in PM removal between tree species under different amounts of rainfall, and 3) analyze the factors that might contribute to the differences in PM removal under different rainfall conditions. Leaves were uniformly collected from top, middle, and bottom layers of the tree canopy at four cardinal directions from the sampling trees after several minutes of rainfall and 12 days after rainfall. Each sampled tree leaf was sealed in a plastic bag immediately after collection. To measure the quantity of PMs trapped on leaves, the samples were washed and water used for washing was collected. Thereafter, 10% of the water was dried to determine the weight of total suspended particulates (TSP), while the remaining 90% of the water was passed through a 10μm mesh filter and then through a 2.5μm mesh filter. These filters were then dried to determine the weight of PM > 10μm (PM > 10) and PMs that were between 2.5 and 10μm (PM10-2.5). Then, 20% of the filtered water was dried to determine the weight of PMs that were < 2.5μm (PM2.5). Once the quantity of airborne particulate matter held per unit leaf area was determined for each of the study species, leaves were sampled after exposure to the following rainfall conditions:light rain (14mm), moderate rain (29mm), 30mm/h indoor simulated rain (equal to 15mm), and 12 days after rain (to determine the saturated dust held in summer). The result indicated that the amount of PM washed off from the leaves by rainfall varied greatly with the size of the particulates and the rainfall condition (including the intensity and amount of precipitation). For all species except Ginkgo biloba, PM10 could be washed off even under light natural rainfall condition and the amount and intensity of rainfall were critical factors in controlling PM removal. Overall, 50% and 90% of the TSP were removed by moderate rainfall and simulated torrential rainfall, respectively, due to higher intensity of rainfall. One major factor that contributes to the above observations is the surface structure of leaves:smooth surfaces, like leathery leaves, have better ability to trap PMs, which also wash-off more easily. Among the five species, Euonymus japonicus recorded the best overall absorption of particulates (washed TSP:(775.06±33.99)mg/m2, light rain), while Ginkgo biloba had an edge on absorbing particulates of small sizes (washed PM2.5:(426.55±40.83.99)mg/m2, moderate rain). We concluded that the species differed in their ability to trap airborne PMs and in the rate of removal of PM from the leaves by a rainfall event, and this was influenced by the differences in the surface structure of leaves of the species, rainfall amount and intensity, as well as the particulate size.
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