Environmental Protection

Researchers, Chrysler Test Trees for TCE Remediation

Purdue University researchers are collaborating with Chrysler LLC in a project to use poplar trees to eliminate pollutants from a contaminated site in north-central Indiana.

The researchers plan to plant transgenic poplars at the site, a former oil storage facility near Kokomo, Ind., this summer. In a laboratory setting, the transgenic trees have been shown to be capable of absorbing trichloroethylene (TCE) and other pollutants before processing them into harmless byproducts.

Richard Meilan, a Purdue associate professor, is currently at work to transform one variety of poplar suited to Indiana's climate; cold-hardy poplars are generally more difficult to alter than the variety used in a laboratory setting. In a study Meilan co-authored, published last October in Proceedings of the National Academy of Sciences, poplar cuttings removed 90 percent of the TCE within a hydroponic solution in one week. The engineered trees also took up and metabolized the chemical 100 times faster than unaltered hybrid poplars.

Meilan said he thinks the transgenic poplars will be able to remove the TCE from the site, which was contaminated by tainted oil stored there in the 1960s. The chemical, used as an industrial solvent and degreaser, lies within 10 feet of the surface, making it accessible to poplar roots, he said.

Planting transgenic trees in the field remains controversial, Meilan said, primarily due to concerns that inserted genes, or transgenes, might escape and incorporate into natural tree populations.

Meilan has applied for a permit to grow transgenic poplars in a field, or non-laboratory, setting from the Animal and Plant Health Inspection Service, the government organization responsible for regulating such research activities, he said.

In order to comply with permit guidelines and to protect the environment, Meilan's team will take measures to prevent any plant material from leaving the site and will remove the trees after three years, short of the five it takes for poplars to reach sexual maturity, he said.

Besides their use in phytoremediation, or pollution removal, poplars have promise as a feedstock for cellulosic ethanol. To investigate their potential in this area, the U.S. Department of Energy awarded a $1.3 million grant to Meilan and two colleagues.

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