`Green Clean:` Researchers determining natural ways to clean contaminated soil


Source: ScienceDaily

Researchers at North Carolina State University are working to demonstrate that trees can be used to degrade or capture fuels that leak into soil and ground water. Through a process called phytoremediation – literally a “green” technology – plants and trees remove pollutants from the environment or render them harmless.

Through a partnership with state and federal government agencies, the military and industry, Dr. Elizabeth Nichols, environmental technology professor in NC State’s Department of Forestry and Environmental Resources, and her team are using phytoremediation to clean up a contaminated site in Elizabeth City, N.C.

Phytoremediation uses plants to absorb heavy metals from the soil into their roots. The process is an attractive alternative to the standard clean-up methods currently used, which are very expensive and energy intensive. At appropriate sites, phytoremediation can be a cost-effective and sustainable technology, Nichols says.

The Coast Guard site was planted with a mixture of fast-growing trees such as hybrid poplars and willows to prevent residual fuel waste from entering the Pasquotank River by ground water discharge. About 3,000 trees were planted on the five-acre site, which stored aircraft fuel for the Coast Guard base from 1942 until 1991. Fuels had been released into the soil and ground water over time. Efforts to recover easily extractable fuel using a free product recovery system – also called “oil skimmers” – had stalled so other remedial options were considered before choosing phytoremediation.

“We knew that tree growth would be difficult on portions of the site due to the levels of fuels in the soil and ground water, but, overall, we thought the trees could keep this contamination from moving toward the river by slowing ground water flow,” Nichols said. “Trees need water for photosynthesis so they absorb water from the ground; that process can slow the amount of ground water flowing toward the river.”

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