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

Kennesaw State University Research And Service Foundation, Kennesaw GA

Investigators

Abstract

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.