Argonne researchers and technicians are tracking how well poplar trees are containing and removing toxic solvents (such as Trichloroethane, 1,1-Dichloroethane, and 1,1,1-Trichloroethane, Trichloroethylene) from underground water. Pictured here are Cristina Negri, Lawrence Moss, John Quinn, Rob Piorkowski. (Photo by Shawn Allee)
When you think of cleaning up toxic waste, you might think of technicians digging huge holes
and carting off contaminated soil. It’s expensive, and they’re often just putting the soil and the
problem, somewhere else – say, to a hazardous waste landfill. Shawn Allee met researchers
who hope trees can clean some toxic waste, and leave the landscape in place:
Transcript
When you think of cleaning up toxic waste, you might think of technicians digging huge holes
and carting off contaminated soil. It’s expensive, and they’re often just putting the soil and the
problem, somewhere else – say, to a hazardous waste landfill. Shawn Allee met researchers
who hope trees can clean some toxic waste, and leave the landscape in place:
Argonne National Laboratory is a Big Science kinda place.
It’s a federal lab southwest of Chicago where they study particle physics, nuclear energy, and
advanced environmental clean-up.
The irony is, the place has been around so long, it’s now cleaning up its own environmental
messes.
In fact, it’s Larry Moss’s job. He takes me to a toxic waste site where trees help clean the soil.
More on those trees in a sec – first, here’s why Larry Moss needs them.
“This site was a very busy site back in the 50s and 60s. We had a large manufacturing process
for reactor components – did a lot of testing of reactor assemblies and different fuel mixtures. And to
do that you had to clean all that equipment and a lot of that solvent came down here.
There was a unit that was called a French drain, which basically was a trench filled with gravel. They would come down here and dump chemicals into this trench, and their theory was it would dissolve into the ground. They
thought it would just go away.”
Those solvents did not go away. They leeched into underground water.
The solvents potentially cause cancer and other problems, so the government said Argonne
needed to do something about the mess.
Researcher Christina Negri lays out what the options were.
“Put a parking lot on top of the pollution area
and basically leave it there forever. The other extreme, it would have been: dig out the soil, take it
somewhere – where you haven’t changed much. You’ve moved it from here to a landfill. That’s not the solution as
well.”
Those options – covering it up or carting it off – are also expensive.
So, Argonne researchers figured they’d try something new.
Negri says they hope to eliminate pollution on site – with the help of poplar trees.
Negri: “We’re taking advantage of a trait that these trees have to
go about finding water.”
Allee: “Let me get a closer look at a tree, here.”
Negri: “What you have to picture in your mind – See the height of the tree?”
Allee: “I’m looking at one that’s as tall as a three story walk-up building I live in.”
Negri: “You have to flip it 180 degrees and imagine the roots are going down that deep.”
Negri says they coaxed the roots into going straight down instead of spreading out. It seems to
work; the poplar trees are sucking water out of the ground and taking up solvent.
“Part of it is degraded within the plant. Part of it goes out into the air, which sounds like an
ominous thing to say, right? But if you do your calculations right, there’s much less risk when
these compounds are in the air than there is when they’re down 30 feet below.”
Negri’s team hopes the poplar trees will be more sustainable and cheaper than alternatives, but
they’re likely to be slower.
After all, it took years for the trees to grow. That’s fine for Argonne, because no one’s at risk – but that’s
not the case everywhere.
“Arguably, this is not the remedy you would adopt if you had, like, a tank spill or something that
you really need to go in right away, clean up and be done very quickly. It’s not a remedy if there’s
anybody’s at risk.”
This isn’t the only attempt to use plants to clean up toxic waste. The science behind it is called
‘phytoremediation.’
In other examples, scientists tried alpine pennycress to clean up zinc, and pigweed to suck up
radioactive cesium.
Negri says the trick is to use the right plant for the right toxin and know whether the plants stays
toxic, too.
Still, she says, toxic waste is such a big problem, it’s good to have lots of tools in your clean-up
toolbox.
For The Environment Report, I’m Shawn Allee.