US Coast Guard Demonstration Site, Elizabeth City, NC
Cook. R. L., J. Landmeyer, B. Atkinson, J.P. Messier, Elizabeth Guthrie Nichols. 2010. Field Note: Successful Establishment of a Phytoremediation System at a Petroleum Hydrocarbon Contaminated Shallow Aquifer: Trends, Trials, and Tribulations. International Journal of Phytoremediation. 12: 716-732.
Press Release September 2009
“Researchers Use Trees to Clean Contaminated Soil and Ground Water.”
North Carolina State University, state and federal agencies, and private industry are working together to demonstrate that trees can be used to degrade or contain fuels that leak into soil and ground water.
Dr. Elizabeth Guthrie Nichols, associate professor in Environmental Technology in the Department of Forestry and Environmental Resources, and collaborators established a phytoremediation demonstration site at the U.S. Coast Guard Training Facility in Elizabeth City, N.C. This effort was supported by funding from the U.S. EPA/NCDENR/Division of Water Quality 319 Program, the U.S. Geological Survey, the U.S. Coast Guard, and British Petroleum, North America. Dr. Nichols worked with Mr. Brad Atkinson (NCDENR), Dr. James Landmeyer (USGS), Mr. J.P. Messier (U.S. Coast Guard), and Ms. Rachel Cook (NCSU graduate student) to design and implement the phyto-demonstration site.
Phytoremediation is literally a “green technology;” it uses plants to remove pollutants from the environment or to render them harmless. The process is an attractive alternative to the standard clean-up methods currently used, which can be expensive and energy intensive. Phytoremediation can be a cost-effective and sustainable technology for use at appropriate sites.
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. Due to past activities, fuels had been released into soil and ground water over time. Efforts to recover easily extractable fuel using a free product recovery system had stalled so other remedial options were considered and some options were pilot-tested 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 towards the river by slowing ground water flow,” Nichols said. “Trees need water for photosynthesis so they take up water from the ground which can slow the amount of ground water flowing towards the river.”
Trees can take up fuel contaminants when they take up water from the ground. Some contaminants will be degraded by trees during this process while other contaminants will be released to air by tree leaves and stems. “We wanted to demonstrate that the trees would first slow the movement of fuel towards the river,” Nichols said. Trees can also increase the abundance and diversity of soil microorganisms around their roots. Some of these soil microorganisms will degrade the fuel still in the ground. “This can be a slower process, but we also want to show that trees will remove the remaining fuel footprint over time,” Nichols said.
Initially, 500 hybrid poplar and willow trees were planted in 2006. Another 2,500 trees were planted in 2007. “Our initial results are very encouraging, and amounts of fuel in the ground have decreased much faster than anticipated,” says Nichols, “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. The Coast Guard has recognized the value of phytoremediation from this study, and has established two additional phytoremediation systems at different locations on base.
NCSU received a $240,584 grant from the USEPA and NCDENR’s Division of Water Quality 319 program, and an additional $15,000 grant from British Petroleum North America, to establish the demonstration site. NCSU was recently awarded another USEPA/NCDENR 319 grant to continue monitoring the site for tree growth and fuel reduction, tree toxicity to fuels, changes to ground water levels and flow, and how fuel contamination is actually removed by the trees.