Date of Graduation

2015

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Division of Plant and Soil Sciences

Committee Chair

Louis M. McDonald

Committee Co-Chair

Jeffrey Skousen

Committee Member

Nicole Waterland

Abstract

Metal contaminated soils are a problem throughout the world. Because metals accumulate in the food chain they have been linked to adverse human and ecosystem health. One promising approach to remediating metal contaminated soils is phytoremediation but success has been limited by an incomplete understanding of the factors that control metal uptake by plants, including the effects when more than one contaminant metal is present in the system. Metal contaminated soil for this study was collected from near Spelter in Harrison County WV, the site of a former zinc smelting site that has contaminated residential soils and stream sediments with zinc, lead, cadmium, copper and other elements of concern. The ability of four important agricultural crops- radish ( Raphinus sativus var. Cheriette); Indian mustard (Brassica juncea var. Mighty Mustard); corn (Zea mays var. Luscious, Hybrid Bicolor); and soybean (Glycine max var. Butterbean) to accumulate heavy metals and associated possible soil-plant interactions were investigated in a pot study. The first experiment quantified the uptake of zinc, lead, cadmium, copper and manganese as growth progressed from dry seeds to hydrated seeds to cotyledons and then to the roots, stems and leaves of the four species listed above. A second, smaller experiment incubated the Spelter soil with increasing concentrations of lead nitrate to determine if there were interactions in metal uptake by radish. The result shows that the potential for metal accumulation differs greatly among the four species. Radish, Indian mustard, and soybean showed a higher potential for metal uptake and accumulations compared to the monocot-corn. Metal accumulation from this study were in this order; Zn>Mn>Cu>Pb>Cd. Cadmium levels in this study were low but above guidance levels and thus, could contribute to the total body burden of Cd in humans. Among the four species, soybean roots had the highest Pb uptake but it was not translocated to the stems or leaves. In contrast, radish and Indian mustard had the highest translocation of Pb to stems and leaves, whereas corn did not accumulate or translocate appreciable Pb. Incubating a multi-metal contaminated soil with lead nitrate resulted in synergistic and antagonistic Zn uptake in radish and weaker synergistic effects for Cd, Cu and Mn. Overall, this work demonstrated that there was an observable trend for tissue Zn, Pb, Cu, and Cd concentrations to increase starting from seed imbibition, to cotyledon, to whole plants; except for Mn, where that there was no clear trend. Also this study established that heavy metal uptake was not only metal specific but also species specific. For example when we compared results for soybean with corn, we determined that soybean removed more metal and thus a better accumulator of metals. Interestingly, the two members of the family Brassicaceae-radish and Indian mustard had similar efficiency to accumulate metals in multi-contaminated soils. The results also suggested that current approaches to characterize the potential for metal uptake from multi-metal contaminated soils are inadequate. Specifically, that it is not possible to predict metal uptake without properly accounting for other metals in the system.

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