Evaluating the mechanisms for phytoremediation of MTBE.

摘要

This thesis examines the dominant mechanisms and measures the engineering parameters for phytoremediation of Methyl tert butyl ether (MTBE) employing bench scale and tree scale experiments. Phase 1, hydroponic plant uptake experiments, indicate 30% reduction in MTBE mass in water over a 1-week period by small poplar saplings. A mass balance indicated that MTBE was untransformed during transport through the small poplar saplings and the transpiration stream concentration factor (TSCF) was computed to be approximately 1, suggesting MTBE is actively transpired by plants at the same concentration as in groundwater. The high TSCF and low RCF indicated that phytovolatilization is the primary mechanism for phytoremediation of MTBE in aqueous bench scale studies.; Phase 2 investigated the potential for microbial degradation of MTBE in the rhizosphere of poplar trees. All studies indicated that MTBE degradation in plant rhizosphere occurs minimally, if at all, and at rates that are very slow and insignificant compared to the rapid rate of plant-assisted transpiration of MTBE shown in phase 1.; Since the first two phases indicated that phytovolatilization is the primary mechanism for MTBE removal from contaminated sites, Phase 3 focused on measuring and predicting evapotranspiration (ET) of large 12&feet; poplar trees since. Results inferred that the Penman-Monteith equation can provide reasonable ET rates for evaluation of chemical uptake during phytovolatilization in the field.; The last phase, Phase 4, researched the fate and transport of MTBE in large (12&feet;) trees in an enclosed chamber allowing for MTBE mass balances to be completed. A deficit of MTBE mass was observed in replicate experiments in a short time period (2-weeks) indicating degradation was occurring within the mature tree. More significantly, tert-butyl alcohol a degradation product of MTBE was detected in increasing amounts as MTBE was detected in decreasing amounts in the leaves as the experiment progressed, further signifying MTBE degradation was occurring.; In conclusion, high uptake rates of MTBE by the poplar tree and degradation within the poplar tree makes phytoremediation of MME a promising technology.