Date of Award

12-1-2019

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Liu, Jia

Abstract

Cr (VI) contaminated soil and tetrachloroethylene (PCE)/trichloroethylene (TCE) contaminated groundwater from a Superfund site were phytoremediated using sunflower (Helianthus annuus L.), a plant with strong adaptability and a hyperaccumulator which possesses great potential for phytoremediation. The Cr (VI) concentration was low of 0.16±0.04 mg/kg in the contaminated soil, and concentrations of PCE and TCE in irrigation water used to reflect influence of groundwater were 2.68±0.27 and 0.80±0.14 mg/L, respectively. For Cr (VI) remediation, physical characteristics, uptake of Cr (VI), bioaccumulation factor (BAF) and translocation factor (TF) were quantified. Analysis of the plants and the soils suggested that Cr (VI) was phytoextracted by roots, then transported from roots to shoots, leaves, seeds and stored within the parts. Both low nitrogen chemical fertilizer and biosolids were used as soil amendments to compare the efficiency of both the amendments on phytoextraction of Cr (VI), and the biosolids treated soil plants showed comparable phytoextraction to low nitrogen fertilizer treated soil plants. During the remediation of Cr (VI) from the co-contaminated soil matrix of both Cr (VI) and PCE/TCE, PCE and TCE were removed >99.9% from the soil matrix while Cr (VI) remediation, and neither PCE nor TCE were detected in effluents, plant tissues and soils after phytoremediation. The remediation of PCE/TCE were accomplished possibly by plant dehalogenation, degradation, plant volatilization, or soil volatilization. Cr (VI) in plant seeds from the contaminated soil plants was 0.36±0.08 mg/kg, which is much lower than the limit of 5.00 mg/kg in soil that will bring health concern. Concerning biodiesel properties, acid value and density were within American Society for Testing and Materials (ASTM) standard limits. Therefore, the produced biodiesel could be used as a potential renewable fuel. In addition, microbial biomass in rhizosphere soil was also studied before and after the remediation. The results showed that after phytoremediation, both biomass carbon and nitrogen increased for both Cr (VI) contaminated and Cr (VI)/PCE/ TCE co-contaminated rhizosphere soil, compared to their control ones. Increase of biomass carbon and nitrogen should be due to and could help the phytoremediation process. In sum, phytoremediation of low concentration Cr (VI) using H. annuus L. with biodiesel production could be a sustainable approach for solving both the environmental pollution problem and the energy crisis issue.

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