Using Trees as Cleaning Tools

  • 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.

Related Links

Development Mangling the Mangroves

  • Mangroves at Mary's Creek, St. John (Photo by Frank Olivier)

If you were a tropical fish living in the
Caribbean, there’s a good chance you would have spent
your youth darting between the roots of mangroves.
Those saltwater plants guard young fish from predators.
Mangroves also protect shorelines from erosion and
hurricanes. But now it’s the mangroves that need
protection. Ann Dornfeld reports:

Transcript

If you were a tropical fish living in the
Caribbean, there’s a good chance you would have spent
your youth darting between the roots of mangroves.
Those saltwater plants guard young fish from predators.
Mangroves also protect shorelines from erosion and
hurricanes. But now it’s the mangroves that need
protection. Ann Dornfeld reports:

It’s a brilliantly sunny, gusty day on St. Thomas in the US Virgin Islands. Stanley
Berry has backed his motorboat into an opening in this quiet mangrove bay. He’s
one of the island’s traditional French fishermen. He’s lean, bronzed and bare-
chested.

“I going yellowtail snapper tonight. I’m doin’ night fishing. See if I can catch
something tonight, God spare life.”

Berry says the red mangroves that ring this bay serve as a sort of daycare for the
young fish he’ll eventually catch.

“If you have to snorkel around and check it out, you’ll notice that all these little
fishes are different type of grouper, snapper, you name it all comes and all the
baby ones come and hang around in there so the big fish don’t eat ’em. It protects
’em. It’s real good for the fish to come and spawn in here and stuff.”

Mangroves’ dry branches are home to birds and lizards. Their roots prevent sediment
from the land from seeping into the water. And mangroves provide a buffer zone that
protects inland areas from storms moving in from the ocean.

As important as they are, these mangroves are at risk. David Olsen is director of the
US Virgin Islands Division of Fish and Wildlife. He says island natives understand
the value of the mangroves. But he says developers aren’t as appreciative. One
company wants to rip out the red mangroves on this bay for new construction.

“They would basically line the entire area with condominiums, have docks
basically filling the entire bay, eliminate all the traditional use, and plant a little
fringe of black mangroves.”

Olsen says developers have to leave some mangroves in their plans, because the
islands have a no-net-loss policy for wetlands. But the black mangroves they want to
plant don’t grow in the water. That means they wouldn’t serve as fish nurseries.

This is hardly an isolated incident.

“We have lost, in the Virgin Islands, probably 50 percent of our mangrove areas
over the last half a century.”

Rafe Boulon is Chief of Resource Management for the Virgin Islands National Park.
He says mangroves are often filled with dirt for new construction.

“Anytime people fill land, typically they’re filling mangroves because they’re
selecting nice calm bays and that’s where the mangroves are.”

Boulon says mangroves are in much better shape here on St. John, a 30-minute ferry
from St. Thomas. That’s because most of this island is a national park.

If you want to see firsthand why mangroves are so important, all you need is a mask
and snorkel. The water is kind of murky and golden from fallen leaves. But it’s rich
with sealife.

“Okay, so we just got out of the water, and we saw probably a dozen different
species of juvenile varieties of the fish you see when you snorkel or dive out in the
deep water. And they’re darting among the mangroves and chasing each other –
really, really playful.”

Boulon says for people new to the islands, mangroves can seem like a swamp. They
release methane as leaf litter decomposes. And the roots collect trash that floats in
from sea.

“So hence, if they’re dirty and smelly there’s no really good purpose for them –
however, they’re very, very important ecosystem here.”

The trick is to convince the scores of people who are building new homes on the
Virgin Islands of the value of mangroves, including a new wave of retiring baby
boomers.

For The Environment Report, I’m Ann Dornfeld in St. John.

Related Links

Romancing the American Chestnut

  • American chestnuts (left) are smaller than Chinese and European chestnuts. The Chinese and European varieties are also resistant to the blight, making the imports more desirable to growers. (Photo by Lester Graham)

Food is always a big part of the holidays. But one
traditional food has – for the most part – disappeared from American tables. The Great Lakes Radio Consortium’s Lester Graham reports:

Transcript

Food is always a big part of the holidays. But one traditional food has – for the most part – disapeared from American tables. The Great Lakes Radio Consortium’s Lester Graham reports:


(Sound of Nat King Cole singing, “Chestnuts roasing on an open fire…”)


That old chestnut of a song romanticizes roasting chestnuts as a part of the holidays. But a lot of us have never even seen chestnuts, let alone roasted them on an open fire. Chestnuts used to be a major part of the Eastern hardwood forest. There were millions of them. In fact, 25 percent of all the mature trees were chestnuts. But a blight, imported with some Chinese chestnut trees, slowly wiped out the American chestnuts. Now, they’re gone.


Well… almost. Much of the root stock is still alive. Sprouts grow until the blight knocks them back again. A blight only hurts the standing tree where it branches out.


And, in a few isolated pockets in the Midwest, the blight hasn’t reached the trees. A few American chestnuts are alive and growing and some of them are free of the blight. At Nash Nursuries in central Michigan, owner Bill Nash is guiding us through a rare sight… a grove of American chestnuts.


“These are 20 years old and as you can see, they’re fairly good sized. The American chestnut is quite a rapid growing tree. It’s well-suited for our climate, so it doesn’t have any of the problems that some of the hybrids do as far as growing and cultural care you have to take care of them. The Americans, you get them started and they’re pretty much on their own.”


In a few places in Michigan and Wisconsin there are small groves of chestnuts. They’re prized trees. They’re great for shade. The hardwood is rot resistant and makes great furniture and fence posts. And the chestnuts are eaten by humans and wildlife alike. Bill Nash says the tree will be popular again if it ever overcomes the blight that’s hit it so hard.


“The American chestnut will make another big comeback in this country as a yard tree, as a timber tree, as a wildlife tree.”


That part about a wildlife tree is more important than just worrying about the squirrels and bunnies. Chestnuts were an important food source for all kinds of animals.


Andrew Jarosz is a plant biologist at Michigan State University. He says the loss of chestnuts has been hard on wildlife populations.


“Chestnuts shed nuts in a more regular pattern than oaks, which will have what are called mast years – where they’ll have major crops, massive crops one year and very small crops in other years – which means it’s either feast or famine if you’re depending on oaks.”


Since the blight first began hitting American chestnuts about a century ago, researchers have been looking into all kinds of ways to stop it. One way is to cross it with the Chinese chestnut which has a couple of genes that resist the blight. But it takes a long time to breed out the Chinese characteristics from the American chestnuts and still keep the resistant genes.


Another approach is genetic manipulation. Genetically modifying the American chestnut tree to make it disease resistant. Again, work is underway, but it takes a long time. And even after success, it’s likely some people won’t like the idea of releasing a genetically modified organism into the wild.


The final approach worked in Europe when the blight hit there. It seems there’s a naturally occuring virus that kills the blight. It spread naturally in Europe. There are a few groves in Michigan that have naturally acquired the virus and it’s working to keep the blight at bay. Andrew Jarosz is working on the research. He says the trick is figuring out how to get the virus to spread to other trees short of manually spreading it on cankers infected by the blight.


“If we’re literally talking about millions of trees across probably, you know, the eastern third of the country, we obviously can’t treat every canker on every tree. And we need to be able to figure out a way to deploy the virus in a way that it can spread.”


Even with all that hopeful research, it’ll be ten years at least before some practical solutions end up in the forests, and Jarosz believes a couple of centuries before the American chestnut holds the place it once did in the forests.


Bill Nash knows it’ll be a while before there are major changes, but he is optimistic about the American chestnut.


“Oh, I would think the tree has a bright future. There’s enough people working on that, enough programs going on now… So, I would suspect that in the not-too-distant future we should have some of this progress made. You know, Robert Frost in his poem predicted the comeback of the American chestnut, that something would arise to offset that blight. And we’re starting to see that.”


Frost put it this way: “Will the blight end the chestnut? The farmers rather guess not, It keeps smoldering at the roots And sending up new shoots Till another parasite Shall come to end the blight.”


Seems Frost was an optimist too.


For the Great Lakes Radio Consortium, this is Lester Graham.

Related Links

New Research in Drug Development

Scientists say they might have found a more efficient way to produce drugs
and chemicals from plants. The Great Lakes Radio Consortium’s Lester Graham
reports… it might reduce the cost of developing drugs: