植物叶面吸收污染物机制研究进展

Research progress on foliar absorption mechanism of pollutants

庞大的植被是大气污染物进入地表系统的重要过滤层,植被表面是污染物与植物相互作用的界面,大气污染物跨叶面进入植物体的运输行为对解释其环境效应至关重要.植物不仅能有效地消减城市大气污染,还可用作被动采样器动态监测不同时空尺度上大气污染的水平与特征,两者均须通过叶面吸收的方式得以实现.气孔与角质层是植物叶面吸收污染物的两种主要途径,角质层因其疏水性组成、精细微观结构及与植物有机体的紧密联系,是污染物跨叶面运输过程中的重要载体.本文主要综述植物叶面吸收大气重金属、有机污染物两方面的研究,总结植物叶面吸收污染物的相关机理及其影响因素(污染物理化性质、植物叶片表面特征和环境条件),并针对目前研究的不足之处提出展望:(1)深入探究植物叶面复杂的微观形貌特征对大气污染物在叶面沉积、滞留的影响,有助于筛选具有高效吸收污染物潜力的城市绿化树种;(2)角质层不仅是运输途径,也是污染物向植物叶片迁移过程中的主要屏障,目前角质层这两方面的功能对于污染物跨叶面运输的相对贡献尚不清楚.因此有必要进一步探究植物角质层立体组成结构对污染物吸附扩散等界面行为的影响;(3)有关有机污染物在活体植物中的叶面微界面行为方面的研究比较匮乏,未来可利用原位检测技术从细胞和亚细胞水平上更加高效灵敏地跟踪、量化多种有机污染物在植物叶面及角质层内部迁移的动态过程.

Large vegetation is an important filter layer for atmospheric pollutants to enter the surface system.The surface of vegetation is the interface between pollutants and plants.The transport behavior of atmospheric pollutants across the leaf surface is crucial to explain their environmental effects.Plant foliage could not only effectively alleviate urban air pollution,but also could be used as a passive sampler to dynamically monitor air pollution levels and characteristics at different spatial and temporal scales,both of which must be realized by foliar absorption.Stomata and cuticle are two major pathways for plant leaves to absorb atmospheric pollutants.Due to its fine microstructure,hydrophobic composition and close relationship with plant organisms,the cuticle plays an important role in carrying pollutants across the leaf surface.This paper mainly reviewed the studies on the foliar absorption of heavy metals and organic pollutants,summarized the relevant mechanisms and influencing factors of foliar absorption of pollutants(physicochemical properties of pollutants,surface characteristics of plant leaves and the environmental conditions),and proposed the outlook for the future research:(1)To explore the influence of complex microscopic features of the foliage on the deposition and retention of atmospheric pollutants on the leaf surface,which was conducive to select the urban greentree species with high pollutant absorption potential.(2)Cuticle is not only a transport route,but also the main barrier in the process of pollutant migration to the plant leaves.At present,the relative contribution of the two functions of cuticle to the transport of pollutants across the foliage remained unclear.Therefore,it is necessary to further explore the effect of the three-dimensional structure of the cuticle on the interface behavior of pollutants,such as adsorption and diffusion.(3)Studies on the micro-interface behavior of organic pollutants in living plants are scarce.In the future,in-situ detection technology can be used to more efficiently and sensitively track and quantify the dynamic migration process of multiple organic pollutants on the leaf surface and inside the cuticle at the cellular and subcellular levels.