Weis Judith S, Weis Peddrick
Department of Biological Sciences, Rutgers University, Newark, NJ 07102, USA.
Environ Int. 2004 Jul;30(5):685-700. doi: 10.1016/j.envint.2003.11.002.
Marshes have been proposed as sites for phytoremediation of metals. The fate of metals within plant tissues is a critical issue for effectiveness of this process. In this paper we review studies that investigate the effects of plants on metals in wetlands. While most of these marsh plant species are similar in metal uptake patterns and in concentrating metals primarily in roots, some species retain more of their metal burden in below ground structures than other species, which redistribute a greater proportion of metals into above ground tissues, especially leaves. Storage in roots is most beneficial for phytostabilization of the metal contaminants, which are least available when concentrated below ground. Plants may alter the speciation of metals and may also suffer toxic effects as a result of accumulating them. Metals in leaves may be excreted through salt glands and thereby returned to the marsh environment. Metal concentrations of leaf and stem litter may become enriched in metals over time, due in part to cation adsorption or to incorporation of fine particles with adsorbed metals. Several studies suggest that metals in litter are available to deposit feeders and, thus, can enter estuarine food webs. Marshes, therefore, can be sources and well as sinks for metal contaminants. Phragmites australis, an invasive species in the northeast U.S. sequesters more metals below ground than the native Spartina alterniflora, which also releases more via leaf excretion. This information is important for the siting and use of wetlands for phytoremediation as well as for marsh restoration efforts.
沼泽地已被提议作为金属植物修复的场地。植物组织内金属的归宿是这一过程有效性的关键问题。在本文中，我们回顾了研究植物对湿地中金属影响的相关研究。虽然这些沼泽植物物种大多在金属吸收模式以及主要在根部富集金属方面相似，但有些物种在地下结构中保留的金属负荷比其他物种更多，而其他物种则将更大比例的金属重新分配到地上组织，尤其是叶子中。储存在根部对金属污染物的植物稳定化最为有利，当金属集中在地下时其有效性最低。植物可能会改变金属的形态，并且由于积累金属也可能遭受毒性影响。叶子中的金属可能通过盐腺排出，从而回到沼泽环境。随着时间的推移，叶和茎凋落物中的金属浓度可能会因阳离子吸附或含有吸附金属的细颗粒的掺入而在金属中富集。几项研究表明，凋落物中的金属可供沉积取食者利用，因此可以进入河口食物网。因此，沼泽地既可以是金属污染物的来源，也可以是汇。芦苇是美国东北部的一种入侵物种，它在地下封存的金属比本地的互花米草更多，互花米草也通过叶片排泄释放更多金属。这些信息对于湿地植物修复的选址和利用以及沼泽恢复工作都很重要。
