Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Civil and Environmental Engineering

Collaborative Specialization

Global Health Systems in Africa

Supervisor

Yanful, Ernest K.

2nd Supervisor

Macfie,Shelia

Co-Supervisor

Abstract

Contaminated soils are a global environmental concern requiring the development of low cost and sustainable remediation techniques. Often soils are contaminated by more than one class of contaminants (mixed contamination) which further complicates remediation efforts. Phytoremediation of contaminated soils has gained great attention as a low-cost and environmentally friendly remedial option. Given these desired advantages, there is not as much information available on plant species suitable for phytoremediation of mixed contaminated soil compared to single class soil contamination. This research evaluates the potential of established phytoremediation plants: alfalfa, oat, ryegrass, indian mustard, sunflower, tall fescue and switch grass to remediate a ternary mixed contaminated soil through greenhouse experiment in pots. Mixed contaminated soil was prepared by spiking soil with Copper (Cu) and Lead (Pb), pyrene and DDT as model compounds for common organic and inorganic contaminants found in mixed contaminated sites; metals, petroleum based hydrocarbon and pesticides. A phytotoxicity test was conducted prior to pot experiment to determine preliminary toxicity of mixed contamination on plants. Results eliminated tall fescue and switch grass from further consideration. Alfalfa, oat, ryegrass, indian mustard and sunflower were grown in triplicates for 72days in pots containing clean and mixed contaminated soils. In addition, unplanted mixed contaminated soils were maintained alongside for the same duration. Results demonstrate that sunflower and indian mustard were the most tolerant plants to the studied contaminant mixtures and concentration. However, only sunflower had the potential to simultaneously remove metals, PAH and pesticide from contaminated soil. Oat was identified as unsuitable for phytoremediation of metal-PAH-pesticide contaminated soil due to its ability to increase exchangeable Cu compared to unplanted soils. In soils planted with ryegrass, exchangeable Cu in soil was redistributed to a less mobile organic fraction while a reduction was observed for exchangeable Pb. The presence of alfalfa in mixed contaminated soils improved the degradation pyrene and DDT only with no metal reduction or changes in metal fractions. Overall the work supports the use of phytoremediation as a potential remedial option for mixed contaminated soils.

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