Date of Award
Master of Science
Phytoremediation is a green technology that uses plants to treat contaminated soil and groundwater. During the decades, phytoremediation has been successfully applied to remediate chlorinated solvents in a variety of environmental media. Plant sorption and uptake are key processes in the phytoremediation of chlorinated solvents. Most previous research assumed that sorption and uptake to plant roots is linear and noncompetitive, neglecting the competitive effect when co-contaminants are existed. Growing evidence, however, indicates that sorption and uptake by plants are nonlinear and competitive. This research focused on the competitive sorption and uptake of trichloroethylene (TCE) by plants in the presence of other chlorinated contaminants and their effects on phytomonitoring of organic contaminant mixtures in groundwater. The competitive sorption experiment was carried out using TCE and other homogeneous chlorinated ethenes and ethanes. Chlorinated ethenes were shown to exert significantly stronger competition on the sorption of TCE than chlorinated ethanes with molecular structures appeared to be the primary reason. Concentrations of both primary and competing compounds affect the extent of competition. Individual physiochemical properties of organic compounds could be related to the competitive capacity of chlorinated ethenes, but the roles appeared secondary. Hydroponic experiment was conducted to investigate the effect of tetrachloroethylene (PCE) and 1,1,2-trichloroethane (1,1,2-TCA) on the uptake of TCE by plants. Concentrations of VOCs in stems decreased along the height in both single and bio-solute systems, TCE/PCE ratio increased along height while TCE/1,1,2-TCA ratio was roughly constant. The results indicated that sampling point as well as the presence of co-contaminants are important considerations in phytomonitoring of organic contaminant mixtures.
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