乌鲁木齐市公园常见乔木对空气颗粒物的滞纳量

Particulate matter retention amount by leaves of common tree species in Urumqi People’s Park

为了探究公园绿化乔木叶片对大气颗粒物的滞纳量在冠层垂直和水平方向上的变化,选择乌鲁木齐市人民公园内分布广且冠层结构有差异的3种阔叶乔木夏橡(Quercus robur)、火炬树(Rhus typhina)、大叶白蜡(Fraxinus rhynchophylla),在7月叶片成熟期对其树冠不同高度(2、4、6 m)和方向(东、南、西、北)的12个位置分别进行叶片采集,分析不同乔木叶片对大气颗粒物(PM_(0.2-3)、PM_(3-10)、PM_(>10)及PM_(total))的单位叶面积滞纳量在冠层不同位置上的差异。结果表明:(1)不同乔木叶片对不同粒径颗粒物的单位叶面积滞纳量存在显著差异(P<0.05);对PM_(3-10)的单位叶面积滞纳量大小排序为夏橡>火炬树>大叶白蜡;对PM_(0.2-3)、PM>(10)及PM_(total)的单位叶面积滞纳量均呈现为夏橡>大叶白蜡>火炬树。夏橡对于不同粒径颗粒物的滞纳量最高且稳定,火炬树对PM_(3-10)的滞纳量较高,而大叶白蜡叶片对除了PM_(3-10)以外的颗粒物滞纳量较高。(2)3种乔木叶片对PM_(0.2-3)、PM_(3-10)、PM_(>10)及PM_(total)的滞纳量在冠层不同高度上具有一定的差异,且差异性均遵守同一规律,即:2 m>4 m>6 m;树冠高度对于叶片滞纳PM_(0.2-3)、PM_(>10)及PM_(total)的影响显著(P<0.05),对于PM_(3-10)的滞纳量极显著(P<0.01);叶片对不同粒径颗粒物滞纳量在冠层方向上未呈现显著性(P>0.05);树冠高度和方向的交互作用也未呈现显著性(P>0.05)。(3)所选树种冠层各点位叶片表面滞纳的颗粒物以PM>(10)为主,PM_(3-10)次之,PM_(0.2-3)量则最小;PM_(0.2-3)主要集中在树冠西北方向4 m处,PM_(3-10)集中在西北方向而树冠高度上无明显规律,PM>(10)在树冠底层2 m处分布较多而方向上并无明显规律。本研究结果可为城市园林管理部门合理选配绿化树种提供科学依据。

The objective of this study was to explore the vertical and horizontal variations of leaf particulate matter retention amount of park greening trees.Three broad-leaved tree species,Quercus robur,Rhus typhina and Fraxinus rhynchophylla,widely distributed in Urumqi People’s Park and with different canopy structures,were selected.Leaves were collected at 12 positions of different canopy heights(2,4,6 m)and directions(east,south,west,north)at leaf maturity stage in July.The difference of retention capacity per unit leaf area of different tree species to atmospheric particulate matter(PM_(0.2-3)、PM_(3-10)、PM_(>10)and PM_(total))at different positions of canopy was analyzed.The results showed that:(1)There was a significant difference in retention amount of different sized particulate matters on leaves among different tree species(P<0.05).The retention capacity of PM_(3-10)per unit leaf area of different tree species across different positions was ranked as:Q.robur>R.typhina>F.rhynchophylla,while the retention capacity for PM_(0.2-3),PM_(>10)and PM_(total)was ordered as:Q.robur>F.rhynchophylla>R.typhina.Q.robur had the highest and stable retention capacity for particulates of different sizes,R.typhina had better retention capacity for medium-sized particulates,and F.rhynchophylla had better retention capacity for particulates except PM_(3-10).(2)There was a certain difference in retention capacity of various particulates at different canopy heights of the three species(P<0.05),and such difference of different sized particulates followed a same pattern,i.e.:2 m>4 m>6 m.Canopy height had a significant effect on leaf retention amount of PM_(3-10),PM_(>10)and PM_(total)(P<0.05),with an extremely significant effect on PM_(3-10)(P<0.01).There was no significant difference in leaf retention capacity to different sized particulates at different directions of canopy(P>0.05).There was no significant interaction of canopy height and direction(P>0.05).(3)PM_(>30)was the main particulate on leaf surface of examined tree species,PM_(3-10)was the second,and PM_(0.2-3)was the least.PM_(0.2-3)was mainly concentrated at 4 m height in the northwest direction,while PM_(3-10)was concentrated in the northwest direction,without obvious pattern in canopy height.PM_(>10)was more distributed at 2 m height in the bottom of canopy,but there was no obvious pattern in the direction.Our results can provide a scientific basis for reasonable selection of greening tree species for the urban park greening management department.