Schmidt Ulrich
Innoterr, Königsbergerstr. 8,67269 Grünstadt, Germany.
J Environ Qual. 2003 Nov-Dec;32(6):1939-54. doi: 10.2134/jeq2003.1939.
For heavy metal-contaminated agricultural land, low-cost, plant-based phytoextraction measures can be a key element for a new land management strategy. When agents are applied into the soil, the solubility of heavy metals and their subsequent accumulation by plants can be increased, and, therefore, phytoextraction enhanced. An overview is given of the state of the art of enhancing heavy metal solubility in soils, increasing the heavy metal accumulation of several high-biomass-yielding and metal-tolerant plants, and the effect of these measures on the risk of heavy metal leaching. Several organic as well as inorganic agents can effectively and specifically increase solubility and, therefore, accumulation of heavy metals by several plant species. Crops like willow (Salix viminalis L.), Indian mustard [Brassica juncea (L.) Czern.], corn (Zea mays L.), and sunflower (Helianthus annuus L.) show high tolerance to heavy metals and are, therefore, to a certain extent able to use the surpluses that originate from soil manipulation. More than 100-fold increases of lead concentrations in the biomass of crops were reported, when ethylenediaminetetraacetic acid (EDTA) was applied to contaminated soils. Uranium concentrations could be strongly increased when citric acid was applied. Cadmium and zinc concentrations could be enhanced by inorganic agents like elemental sulfur or ammonium sulfate. However, leaching of heavy metals due to increased mobility in soils cannot be excluded. Thus, implementation on the field scale must consider measures to minimize leaching. So, the application of more than 1 g EDTA kg(-1) becomes inefficient as lead concentration in crops is not enhanced and leaching rate increases. Moreover, for large-scale applications, agricultural measures as placement of agents, dosage splitting, the kind and amount of agents applied, and the soil properties are important factors governing plant growth, heavy metal concentrations, and leaching rates. Effective prevention of leaching, breeding of new plant material, and use of the contaminated biomass (e.g., as biofuels) will be crucial for the acceptance and the economic breakthrough of enhanced phytoextraction.
对于重金属污染的农田，低成本的植物提取措施可能是新土地管理策略的关键要素。当向土壤中施加试剂时，重金属的溶解度及其随后被植物的积累量会增加，从而增强植物提取效果。本文概述了提高土壤中重金属溶解度、增加几种高生物量产量且耐金属植物的重金属积累量的现有技术水平，以及这些措施对重金属淋溶风险的影响。几种有机和无机试剂可以有效且特异性地提高几种植物物种对重金属的溶解度，进而提高其积累量。柳树（Salix viminalis L.）、印度芥菜[Brassica juncea (L.) Czern.]、玉米（Zea mays L.）和向日葵（Helianthus annuus L.）等作物对重金属具有较高的耐受性，因此在一定程度上能够利用土壤处理产生的多余重金属。当将乙二胺四乙酸（EDTA）施用于受污染土壤时，据报道作物生物量中铅浓度增加了100多倍。当施用柠檬酸时，铀浓度可大幅增加。镉和锌浓度可通过元素硫或硫酸铵等无机试剂提高。然而，不能排除由于土壤中迁移性增加导致重金属淋溶的情况。因此，在田间规模实施时必须考虑采取措施尽量减少淋溶。所以，当作物中铅浓度未提高且淋溶率增加时，施用超过1 g EDTA kg(-1)是低效的。此外，对于大规模应用，诸如试剂的施用方式、剂量拆分、施用试剂的种类和数量以及土壤性质等农业措施是控制植物生长、重金属浓度和淋溶率的重要因素。有效防止淋溶、培育新的植物材料以及利用受污染的生物质（例如作为生物燃料）对于强化植物提取的接受度和经济突破至关重要。
