上海典型植物叶表滞尘离子组成及差异分析

Ion Composition and Variance Analysis of Particulates Deposited on Plant Leaves of Typical Tree Species in Shanghai

城市植被对大气颗粒物的滞纳是削减城市大气污染的重要途径。该研究使用单颗粒飞行时间质谱仪(SPAMS)在2016年7月-2017年4月期间对上海市2个典型污染区(吴泾工业区、松江交通枢纽)的大气颗粒物、自然降尘和4种典型绿化植物(香樟Cinnamomum camphora、二球悬铃木Platanus acerifolia、龙柏Sabina chinensis、水杉Metasequoia glyptostroboidesd)叶片表面滞尘的离子组成进行了一年四季共39 d的测定,结果表明:(1)上海典型污染区大气颗粒物、自然降尘和典型绿化树种叶片上滞留的颗粒物的主要离子成分依次为CN^-、NO_3^-、NO_2^-、SO_4^-、Cl^-等,不同类别的离子占比存在显著差异;(2)4树种均对主要来源于扬尘的Fe^+有着明显的吸附特征,但香樟与水杉叶片表面滞尘与同期自然降尘中的离子组成较为接近,表明2树种叶表滞尘过程受所在地区大气环境影响较大;而龙柏和悬铃木叶片滞尘的离子组成与同期降尘成分存在明显差异,在滞尘过程中表现出对特定离子的专属吸附特性。最后提出针对不同空气污染区选配更高效滞尘树种的建议,为提高城市植被的生态系统服务功能提供技术支撑。

Urban vegetation plays an important role in air pollution reduction.In this study,the single particle aerosol mass spectrometer（SPAMS）was applied to the measurement of ion composition of atmospheric particulates,natural dust-fall and ion composition of the particulates retained on plant leaves of such tree species as Cinnamomum camphora,Platanus acerifolia,Sabina chinensis,Metasequoia glyptostroboidesd in two typical polluted regions（Wujing Industrial Region and the Songjiang Traffic Hub）in Shanghai during the period from July 2016 to April 2017.The findings of the study suggested that main ionic components of the atmospheric particulates,dust-fall and particulates retained on plant leaves were CN-,NO3-,NO2-,SO4-,Cl-etc,and the proportion varied with ion types.A notable characteristics of iron adsorption were found in four tree species,which mainly came from dust,and the ion composition of particulates on Cinnamomum camphora and Metasequoia glyptostroboidesd leaves was relatively close to that of dust-fall within the same period,which indicated the influences of the local ambient air;on the other hand,there were significant discrepancy of the ion proportion between dust-fall and the particulates on Sabina chinensis and Platanus acerifolia and leaves,implying that these two tree species had an exclusive character of adsorption to some specific chemical compositions.Finally,proposals were put forward regarding the selection of proper tree species in the specific polluted areas for better dust-retention so that the ecosystem services of urban vegetations could be upgraded.