November 2001

From Virginia Tech

Virginia Tech study may help develop more effective clean up of gasoline spills

BLACKSBURG, Va., Nov. 8, 2001— In an effort to enable more effective clean up of gasoline spills, Virginia Tech geological sciences researchers are looking at whether microbes use terminal electron accepting processes sequentially or simultaneously.

The research will be presented during the 113th National Geological Society of America meeting in Boston, Nov. 1-10, 2001.

Jackson M. Spain is conducting the research as part of his master’s thesis, under the direction of Madeline Schreiber, assistant professor of geological sciences.

Underground storage tanks such as those at service stations sometimes leak, creating underground gas plumes, Spain said. The gas then can get into the groundwater. The most dangerous components of the gasoline are benzene, toluene ethylbenzine, xylenes, or BTEX, because they are most soluble and most likely to get into the groundwater. BTEX, particularly benzene, are carcinogenic.

Bioremediation, which relies on naturally occurring subsurface bacteria to break down contaminants, is an accepted treatment method for cleaning up gasoline spills. The terminal electron accepting process (TEAP) that bacteria use to break down gasoline compounds exerts a strong control on the extent and efficiency of bioremediation. The use of oxygen (aerobic respiration) yields the most energy to the bacteria and thus results in the most complete and rapid bioremediation. When oxygen is not present, bacteria can use other TEAPs, such as nitrate reduction, iron reduction, sulfate reduction, and methanogenesis, to break down gasoline compounds.

"Our study is looking at two specific TEAPs, iron reduction and methanogenesis," Spain said. "We’re studying how the heterogeneities of Fe(III) concentrations affect which TEAPs are utilized. We’re trying to see if the differences in the Fe(III) concentrations would cause the TEAPs to be used simultaneously instead of sequentially, which is how the theory predicts and how it’s now modeled."

If the researchers find that the Fe(III) concentration does affect the use of TEAPs so that they are used simultaneously, scientists can better model the degradation of a plume. "Then, if we can better model the process, we can better clean it up," Spain said. "We can better model how long it would take for remediation to occur or how long we would have to get the gas out before it became a bigger problem."

The poster, "The Role of Fe(III) Heterogeneity in Controlling Bioremediation of Petroleum Contaminated Aquifers," by Spain and Schreiber will be at the Hynes Convention Center Hall D booth 25 from 8 a.m. until noon on Thursday, Nov. 8, as part of Session 151, Environmental Geosciences.

Dr. Madeline E. Schreiber can be reached at mschreib@vt.edu or 540-231-3377
PR CONTACT: Sally Harris 540-231-6759 slharris@vt.edu











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