Friday, February 26, 2010

The Oldest Eco-tech: Trees

We need a machine that can clean pollution out of the ground and the water table. It has to suck the bad stuff (pollutants) out and leave the good stuff (water and dirt) in. Then, somehow, the machine needs to break the poisonous molecules into smaller, harmless ones, thus recycling pollutants without producing any additional waste in the process. One imagines a tangle of tiny tubes linked to sensors, vials, and off-gas valves—an ecological engineer’s lifework, perhaps.

But environmental scientist Elizabeth Nichols and her graduate student Rachel Cook think the fantastic machine already exists: it’s a tree.

The state of North Carolina approached Nichols with the same problem in the mid-90’s. A World War II Air Force depot near Elizabeth City had been dismantled. The work uncovered concrete bunkers under the tarmac, and the bunkers were slowly seeping their contents—150,000 gallons of jet, diesel, and gasoline airplane fuel—into the surrounding soil. The fuel occupied the first level of water table, a mere 7 feet beneath the soil.

And the tarmac was about 100 meters from the Pasquotank River.

“The question was first how to slow the seepage down, then ultimately how to draw the pollutants off the water table. And how to do it without disturbing the surrounding ecology even more,” Nichols said.

Her answer was phytoremediation—an application that uses plants as well-designed eco-tech. Nichols and her collaborators (USGS, NCDENR, and US Coast Guard) planted poplar, willow, and pine trees to slow groundwater seepage, slowly draw the diluted fuel from the groundwater, and then release the broken-down fuel, in the form of hydrogen and oxygen, into the air.

“Jet fuel isn’t good for trees,” Nichols said, “and you can see bare spots where the soil is saturated.” But trees like the willow pull water off the top of the water table, where lighter jet fuel floats. Nichols and Cooks’ results imply that the trees have had significant impact on pollutant levels since 2006.

Phytoremediation as a major means of ecological remediation hasn’t been widely accepted, yet. This study serves as a demonstration site for North Carolina-- consideration of a holistic and far-seeing approach to an immediate threat to resources. Nichols and Cook want to prove that such foresight can be successful.

The study is funded by the EPA and North Carolina’s Department of Natural Resources’ 319 program to clean surface water. Cook’s paper describing the current state of groundwater at Elizabeth City site will be published in the next issue of the International Journal of Phytoremediation, due out later this year.


  1. Interesting study. I wonder why they chose to plant those particular species of trees? It seems as if the fuel had some effect on the health of the trees. Could this be a win-win situation for invasive species of trees? Rosemary Hallberg

  2. Very interesting article! Are there any plans on how to "neutralize" the heavier components of the fuels too?

  3. Proof that we need to stop synthesizing/engineering solutions to problems when there is already a natural solution. Great work!

  4. Neat. Maybe that could be a good solution for Steven Burgess' swine poop problem. Plant trees everywhere and filter that crap least the smell anyways. Probably not though.

    Seems like an incredibly low cost solution to a huge problem. However, this doesn't look like it would be useful unless time was given for these trees to do their work. I don't know how long it would take planting trees to at least cease further seepage, but that would have to be the minimum amount of time allowable before actual environmental harm was inflicted, right? I feel it wouldn't be a good solution for emergencies, but a good one still.

    Good post. Bravo.

  5. Nice intro and commentary. You managed to translate something that was probably hard to understand at first into something that I could comprehend without too much difficulty-even with the big words, you gave good explanations. Great for a non-science person such as myself.

  6. Wow I really like this study.
    @rhallberg from what I understood they used those species of trees because the pull water and the jet full out of the groundwater supply.
    I wonder how the trees are fairing though.

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