RUI: Restoration of lead (Pb) contaminated soils through chemically enhanced phytoextraction by switchgrass (Panicum virgatum)

尽管在限制新的铅（Pb）排放源方面取得了很大进展，但慢性铅危害仍然存在，特别是在城市地区。在美国的城市中，土壤中的弥漫性铅（从含铅汽油燃烧废气等来源分散到土壤中的铅）是一个持续的铅储存库，导致长期慢性暴露。开发高效除铅技术的努力包括许多生物和地球化学操作，每一种操作都产生了显著的增量改进。该项目的目标是将影响铅吸收的各个因素结合起来，以提高一种常见的快速生长模式植物（柳枝稷）从土壤中去除铅的效率。该项目的研究人员正在研究一系列土壤改进剂，包括杀菌剂、金属螯合剂和植物生长调节剂，以改善土壤中铅的去除，并将其集中到植物的地上部分。然后，这些植物可以被移除并以安全的方式处理。开发有效的铅植物修复技术的努力包括土壤杀菌剂（苯甲酰）处理，以降低丛枝菌根真菌（AMF）的金属排斥作用，以及在土壤中应用铅螯合剂，如柠檬酸，以调动铅并提高其对植物生物量的吸收。然而，在这种情况下，铅的植物毒性限制了植物的寿命，并造成了吸收能力的限制。该项目的研究人员正在研究是否可以通过叶面铁（Fe）、植物生长调节剂和外源一氧化氮供体的协调应用进一步增强植物对铅的提取。这些操作有助于提高高生物量柳枝稷（Panicum virgatum）的植物提取效率。研究小组正在使用肯尼索州立大学最先进的实验温室设施，以及从亚特兰大市区和佐治亚州Cedertown的前超级基金遗址取样的受污染土壤。系统地改变了土壤杀菌剂、螯合剂和铁、植物生长调节剂和外源一氧化氮（NO）供体单独和组合施用的实验条件，以优化每一种并测试协同效应。将提取和分析铅污染和非污染土壤中AMF组合的高通量DNA序列，以表征AMF的物种组成。正在对土壤和植物组织样品中的铅、铁、磷以及一整套宏观和微量营养素进行化学分析。该研究项目有潜力为植物修复的科学知识做出贡献，同时也培养本科生研究人员进行高水平的研究。该项目的结果有可能大大提高植物提取率，并指导适合技术转让的土壤恢复技术的发展。

Despite great progress in limiting new lead (Pb) sources of emissions, chronic lead hazards remain particularly in urban areas.  In U.S. cities, diffuse lead in soils (lead that has been dispersed in soils from a source such as leaded gasoline combustion exhaust) is a persistent reservoir of lead, contributing to long term chronic exposure. Efforts to develop efficient lead removal techniques have included a number of biological and geochemical manipulations that each, alone, has produced significant incremental improvements. A goal of this project is to combine the individual factors affecting lead uptake to increase the efficiency of lead removal from soils in a common, fast growing model plant (switchgrass). The project researchers are investigating a series of soil amendments, including a fungicide, metal chelator, and plant growth regulator, for improving lead removal from the soil and concentrating it into the above-ground parts of the plant. The plants could then be removed and disposed of in a safe manner.Efforts to develop efficient lead phytoremediation techniques have included soil fungicide (benomyl) treatments to down-regulate the metal exclusion actions of arbuscular mycorrhizal fungi (AMF) and the application of lead chelating agents, such as citric acid, in soil to mobilize lead and enhance its uptake to plant biomass. In such cases, however, the phytotoxicity of lead limits plant life and creates a limit on uptake capacity. The project researchers are studying whether phytoextraction of lead can be enhanced further by a coordinated application of foliar iron (Fe), plant growth regulator and exogenous nitric oxide donors. These manipulations may serve to increase the phytoextraction efficiency of the high biomass producing switchgrass (Panicum virgatum). The research team is using state-of-the-art experimental greenhouse facilities at Kennesaw State University, along with contaminated soils sampled from urban Atlanta and a former Superfund site in Cedertown, GA. Experimental conditions are being systematically varied among soil fungicide, chelate, and foliar application of iron, plant growth regulator and exogenous nitric oxide (NO) donor, singly and in combination, to optimize each and test for synergistic effects. High throughput DNA sequences of AMF assemblages in lead-contaminated and non-contaminated soils will be extracted and analyzed to characterize AMF species composition. The chemical analysis of lead, iron, phosphorous (P), and the full suite of macro- and micro-nutrients are being determined in soil and plant tissue samples. The research project has the potential for contributing to scientific knowledge on phytoremediation while also training undergraduate student researchers in high level research. Results of this project have the potential to dramatically improve phytoextraction rates and guide the development of a soil restoration technique appropriate for technology transfer.