Date of Award


Degree Type


Degree Name

Master of Science in Integrative Biology (MSIB)



Committee Chair/First Advisor

Dr. Sigurdur Greipsson

Second Committee Member

Dr. Thomas McElroy

Third Committee Member

Dr. Daniel M. Deocampo

Fourth Committee Member

Dr. Hanan El-Mayas


Contamination of soils with lead (Pb) continues to pose a risk to the health of humans especially in residential urban areas. Remediation of these soils is necessary to reduce the amount of Pb and alleviate risk to human health. Phytoextraction of Pb through chemically induced accumulation of Pb in the harvestable foliage and removal of contaminated plant material has great potential in offering a solution to this environmental problem. The effects of the combined application of a soil fungicide (benomyl), synthetic chelates (ethylenediamineteteraacetic acid, EDTA), and foliar-Fe supplement on lead (Pb) phytoextraction from contaminated soil by switchgrass (Panicum virgatum) was examined. Leadcontaminated (76 mg Pb kg−1) urban topsoil collected from Atlanta was placed in pots (n=32) seeded with switchgrass. Pots were arranged in a completely randomized design with the following treatments: (C) Control, (B) Benomyl, (E) EDTA, (F) Foliar-Fe, (BE) Benomyl + EDTA, (BF) Benomyl + Foliar-Fe (FE) Foliar-Fe + EDTA, (BFE) Benomyl + Foliar-Fe + EDTA. Each treatment was replicated with four pots for each treatment combination and five plants per pot. Chemical treatments were initiated at 82 days after planting (DAP) when leaf tips showed yellowing. On 82 DAP, benomyl (20 mg kg-1 soil) was applied to the soil of plants in treatments B, BE, BF, and BFE. EDTA was added (6.2 mg kg-1 total) in 8 split applications for plants in treatments E, BE, FE, and BFE. On 92 and 96 DAP, EDTA 0.1 mmol kg-1 was applied to the soil of plants in ETDA treatments, and on days 100, 106, 112, 118, 127, and 135 DAP 1 mmol kg-1 was added to plants in EDTA treatments. On 103, 109, and 166 DAP, foliar-Fe (20 mg L-1 Iron (II) Sulfate Heptahydrate) was applied directly in three doses to the above-ground foliage of plants in treatments F, BF, FE, and BFE. Plants were harvested at 155 DAP. Samples from both the shoots and roots were analyzed for element concentration (Fe, Mn, P, Pb, and Zn) using either inductively coupled plasma (argon) atomic emission spectroscopy (ICP-AES) or atomic absorption spectrometer (AA-Spec). Plant growth and soil element data were analyzed for significant differences among individual treatment combination means (Control, B, E, F, BE, BF, FE, and BFE) using one-way ANOVA with Fisher’s Test for Least Significant Difference as a post-hoc test. Additionally, data were analyzed for categorical differences and interaction effects for treatment with benomyl, EDTA, and foliar-Fe using General Linear Model. All statistical analyses were run in Minitab® (version 17.1.0) (Minitab Inc. 2013) with statistical significance accepted at 5% confidence level (α=0.05). Shoot Pb concentration did not vary significantly among treatments. However, increased biomass in the shoots of plants in the EDTA treatment resulted in an increase of total extracted Pb in the shoots: 0.17 mg in plants treated with EDTA. This value was a 24% increase above the Control plants (0.13 mg). Plants treated with EDTA had significantly higher root Pb concentration (117 mg kg-1). This value was a 168% increase above the Control plants (43.7 mg kg-1). Arbuscular mychorrhizal fungi (AMF) presence was suppressed in plants treated with EDTA and benomyl. Suppression of AMF activity by benomyl had no significant effect on Pb extraction by the switchgrass. However, translocation-ratio of Pb concentration in shoots to roots (TF) was significantly higher in plants treated with foliar-Fe, indicating a significant effect of foliar-Fe on Pb extraction. In conclusion, switchgrass has been shown to be able to accumulate Pb in its tissues, though treatment under the conditions of this study did not significantly affect shoot concentrations of Pb. The increase in soil pH with EDTA treatment (from 5.5 to 6.9) may have reduced the efficacy of EDTA in effecting Pb transport and should be considered in future studies. It is noteworthy that foliar-Fe treatment was successful in increasing TF of Pb from roots to shoots, and should be explored further as a phytoextraction enhancement. Further research in regard to the use of foliar-Fe application to increase the TF of Pb in switchgrass is recommended especially under higher soil level of Pb before initiating a pilot study in the field.