Trees: a clean, green pollution solution

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On August 20, 2003

A UMR researcher’s studies on how trees can help clean up the environment has received a $270,000 boost from the U.S. Environmental Protection Agency.

Joel Burken, associate professor of civil and environmental engineering, and civil engineering student Anna Stoverink examine poplar saplings in the lab.

Dr. Joel Burken, associate professor of civil and environmental engineering, will conduct a three-year study on the use of trees to identify and clean contaminants in groundwater. The grant comes from the EPA’s Midwest Hazardous Substance Research Center at Purdue University and is made possible in part by a donation from BP Group’s Environmental Management Co.

The grant will support a combination of laboratory and field work in the area of "phytoremediation," an environmental cleanup method that involves planting various hybrid and native trees to stabilize soils, remove contaminated groundwater and soak up excess water before it has a chance to pick up contaminants. Some of the work will be done in the greenhouse to be constructed this fall atop Butler-Carlton Hall on campus. Other work will be conducted at various contaminated sites across the nation.

Those proposed field sites include the Portsmouth Gas Diffusion Plant in Ohio, a Department of Energy uranium-enriching facility where chlorinated solvents were used for parts cleaning; the Aberdeen Proving Grounds (Army testing site) in Maryland, where chlorinated solvents were disposed improperly after use in chemical processes; a University of Washington test plot near Seattle, Wash., where lined cells have been planted with poplars and other trees and chlorinated solvents have been added in a controlled experiment; and a Navy submarine base, a disposal site on Naval Undersea Warfare Center (NUWC) Division Keyport near Seattle, where chlorinated solvents are being remediated with hybrid poplars.

Burken will collaborate with a University of South Carolina professor, Dr. Lee Newman, who leads the research at the Washington sites.

Phytoremediation is a relatively new concept in the field of environmental engineering, but Burken has been studying it for more than a decade. He initiated his research while a graduate student at the University of Iowa.

Some contaminants targeted by phytoremediation include chlorinated solvents or degreasers, paint thinners, engine cleaners, and dry-cleaning chemicals. According to Burken, these are the most common groundwater contaminants in the United States.

"The big benefit of phytoremediation is that it helps the environment and ecology instead of destroying it like some other pollution clean-up strategies, such as incineration," says Burken.

Though phytoremediation has some limitations, Burken is hopeful that it will have more widespread applications in the future, particularly for mildly-contaminated, long-term situations. A site that is too toxic, for example, is not a good candidate for phytoremediation because the toxins can kill the trees. Moreover, it may be toxic enough to need immediate cleanup, rather than a slow, more natural cleanup, says Burken.

"It’s not used for all sites now and definitely not for all contaminants, but as we better understand and start to engineer the systems instead of understanding only what happens naturally, I think we’ll be able to go after more and more contaminants and more and more locations."

In addition to being environmentally sound, phytoremediation is also economical, Burken says. "Once you implement it, the system requires no more energy. It’s basically solar-driven."

Burken has conducted research at about 10 sites across the United States. He also is working on innovative ways to identify particular contaminants by taking trunk samples from the trees. This process, called "phytomonitoring," was recently highlighted in the journal Environmental Science and Technology. Phytomonitoring consists of taking core samples about the size of a pencil from the bark, then analyzing them to determine the level of contamination in the soil beneath the tree.

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On August 20, 2003. Posted in Research