Phytoremediation of a lead contaminated soil by selected green plants

As human populations grow worldwide, there is an increasing need to address the problems associated with the creation and disposal of wastes. Although a variety of recent technologies have been shown to be somewhat effective in the remediation of metal contaminated soils, e.g., chemical extraction and stabilization, they are often expensive and labor-intensive. Additionally, these technologies can impart detrimental effects on the chemical and physical properties of the soil under treatment. As an alternative, the less expensive, more environmentally benign use of green plants as tools for the remediation of contaminated soils (phytoremediation) has been studied in recent years.The reported research activities studied the ability of a variety of green plants to extract lead (Pb), cadmium (Ca) and barium (Ba) from metal contaminated soil. Additionally, the researcher studied the degree to which the addition of the synthetic chelate diethylenetriaminepentaacetate (DTPA) and dilute HNO3 affected: the phytoextraction of metals from contaminated soil; the translocation of these metals within study plants; and the effects that the treatments had on biomolecule production in Zea mays, Glycine max, Brassica juncea and Helianthus annuus. A growth chamber study was also conducted to determine if several species of green plants (Ipomoea leptophylla, Lycopersicon esculentum, Capsicum annuum and Tagetes minuta) were capable of hyperaccumulating any of the metals present in the contaminated soil. Additionally, a leachate study was performed to determine the effects that DTPA and HNO3 had on soil Pb mobility rates.Samples were analyzed for Pb, Ca and Ba using FAAS and the data were further analyzed to determine universal measures of variance. While no plants showed overall significant (p=0.05) differences with regard to both treatment and plant part, all species were capable of both accumulating and distributing Pb from the contaminated soil; no plants were able to extract Ba from the soil; some plants extracted trace amounts of Cd in various plant parts. Significant (p=0.05) differences were measured in chlorophyll a, chlorophyll b and carotenoid concentrations with regard to both plant and treatment. Results from the Pb mobility study showed significant (p=0.01) differences in Pb mobility with regard to both treatment and time.Department of Natural Resources and Environmental ManagementThesis (M.S.