Methyl tert-butyl ether (MTBE) is the most commonly used gasoline oxygenate in the North American's fuel industry. Its persistence in groundwater is of significant concern, which provides a major stimulus for the investigation and research on the environmental sites contaminated with MTBE. There is evidence that MTBE has become one of the most common contaminants in urban groundwater. Aerobic biodegradation has been viewed as one of the most effective methods for treating MTBE contamination, in which MTBE is broken down to the intermediate tert-butyl alcohol (TBA) through the activities of the enzymes cytochrome P-450 monooxygenase (CYP 450s), and TBA is further metabolized to the final products CO2 and H2O. Enzymes of the CYP 450s are the typical enzyme of vascular paints to play a critical role in the plant metabolism and we therefore have good reasons to believe that paints would be able to metabolize MTBE. Initial studies indicated that more than 24 plants from 15 families were found to be unable to degrade MTBE. Currently there is no data available in the research of phytoremediation of TBA. This paper examined the degradation potential of rert-butyl alcohol (TBA) by willow trees (Salix alba) within a carefully designed bioreactor. Pre-rooted willow trees were kept in an Erlenmeyer flask of 500 mL with 450 mL spiked aqueous solution for 12 days. TBA and other possible intermediates of TBA were measured by GC/FID. Willow tree uptake tests indicated that 15.26% TBA mass in aqueous solution was removed through willow tree activities at 15℃ over a 12-day period of exposure. No any other possible metabolite of TBA was tracked and trace amounts of TBA mass (<1%) were found within the willow tree biomass as insoluble residue during the entire period of tests. Excised willow roots and leaves were also used to investigate the potential of willow trees to degrade TBA within glass vessels with 25 mL spiked solution for 3 days. Results of metabolism tests with excised roots and leaves indicated that significant TBA reduction (>10%) was not observed in any of the tests and any other known metabolite of TBA was not detected. It is to conclude that TBA is also persistent to the attack of plant enzymes of willow trees. The persistency of TBA may be the key to inhibit and/or disrupt the CYP-450s enzymes of willow trees in the processes of the MTBE metabolism.
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