Researchers: Trees Clean Fuel-Contaminated Soil and Water
Once soil and groundwater are contaminated with fuels, cleaning them up can be both energy intensive and expensive. But researchers at North Carolina State University are working with trees to demonstrate that phytoremediation is a sustainable, cost-effective solution for degrading and capturing the leaked fuels from contaminated sites.
Phytoremediation is a form of bioremediation which treats environmental contamination using plants to mitigate the problem on site without having to remove the material and dispose of it somewhere else. The researchers from NC State are using this green technology to clean up a Coast Guard site in Elizabeth City, NC, which was used to store aircraft fuel for almost 50 years.
The Coast Guard site was planted with a mixture of fast-growing trees such as willows and hybrid poplars to prevent the residual fuel waste from entering the Pasquotank River through ground water discharge. About 3,000 trees were planted on the five acre remediation site – initially, 500 hybrid poplar and willow trees in 2006, and another 2,500 trees in 2007.
“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. 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.” – Dr. Elizabeth Nichols, environmental technology professor, NC State
Trees can take up fuel contaminants in the process of absorbing water from the ground, and some of the contaminants will be degraded by the trees during that process, while others will be released by tree leaves and stems into the air.
“Our initial results are very encouraging, and amounts of fuel in the ground have decreased much faster than anticipated, but there is still much to learn about how trees can impact residual, weathered fuels over time. There are two areas on the site where trees do not do well, but, overall, tree growth and survival are impressive.” – Nichols
According to the researchers, the Coast Guard has recognized the value of phytoremediation due to this study, and has established two additional phytoremediation systems at different locations on the base. Previous efforts to recover easily extractable fuel on the site using oil skimmers had stalled, so other remediation options were considered before choosing to try phytoremediation.
The research project was funded by the U.S. EPA, the North Carolina Department of Environment and Natural Resources, and British Petroleum North America.