Humble fungi found in most back gardens could help clean up battlefields contaminated with depleted uranium.
At present, sites can be partial decontaminated by physically collecting and disposing of fragments from shells. However, radioactive particles and dust from explosions remain in the soil, preventing full reclamation.
Now, a research team in Scotland has established that common fungi can grow on and chemically lock away the offending uranium. As their hyphal filaments sprawled across fragments of depleted uranium, the tubules gradually became coated in a yellowy mineral.
This, it turned out, locked the uranium into a chemical form inaccessible to biological organisms, and unlikely to dissolve into surface waters.
At twice the density of lead, depleted uranium is added to weapons to give them extra force to penetrate targets. But the complete fallout from exploding missiles is impossible to collect physically. This means that hazardous radioactive uranium-235 in the material, which can cause kidney toxicity and has been linked with nerve damage and lung cancer, can persist in the environment for decades.
"The fungal-produced minerals are capable of long-term uranium retention, so this may help prevent uptake of uranium by plants, animals and microbes," says team leader Geoffrey Gadd of the University of Dundee. "It might also prevent the spent uranium from leaching out from the soil," he says.
Essentially, the fungi form uranyl phosphate minerals which stabilise the uranium. "They change its chemistry from being highly chemically unstable and reactive metallic uranium to one of the most chemically stable forms, thus preventing uranium migration through the food chain," says Gadd.
Gadd says that any clean-up operation based on the fungi would be very low-tech. All that would be needed in practice would be to add moisture and nutrients to soil to help fungi flourish.
"You can go to just about any soil, and you'd find fungi that would lock away uranium," he says. "You could literally pick them from your own back garden."
But he cautions that the minerals probably couldn't ever be considered harmless as they still contain uranium, and this could still be toxic if eaten. Nor have the Dundee team yet worked out a practical way to collect and dispose of the trapped uranium.
The finding itself was a bonus in research mainly aimed at tracing the environmental fate of uranium. "Our work is only very preliminary," he says.
Ultimately, it might be possible to devise practical ways of using the fungi to decontaminate sites, Gadd says.
Journal reference: Current Biology (vol 18, R375).
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By Bsdts
Mon May 05 17:52:16 BST 2008
Even if the fungi lock away the uranium, keeping it out of the food chain and making it chemically stable, etc., isn't it still radioactive? Wouldn't there still be the same problem of radioactive exposure in living next to the affected area, or even just walking by?By Rob Chansky
Mon May 05 19:12:25 BST 2008
Yeah, sorta. It's not much radiation and it's mainly Alpha particles which don't penetrate clothing or skin. The problem is that the DU blows about as dust, gets inhaled, and then all its radioactivity goes toward messing up the lungs, in addition to the heavy metal toxicity.By Soylent
Mon May 05 23:48:22 BST 2008
"Even if the fungi lock away the uranium, keeping it out of the food chain and making it chemically stable, etc., isn't it still radioactive?"By Pete
Mon May 05 20:52:28 BST 2008
Depleted uranium poses no radiation threat. It simply doesn't decay quickly enough. However It is chemically poisonous. So having fungi suck it up would seem to be a good idea. It depends on where the fungi go afterwards as compared to leaving the uranium in the ground. The "area" is not radioactive, as the article would suggest.By David
Tue May 06 03:14:52 BST 2008
If it were not radioactive then what would there be to "decay"? Surely on the contrary it very definitely IS radioactive, although not highly so? It continues to pose a radiation threat despite the slow decay because the finely divided dusts can get airborne and ingested or taken into the lungs; most of the isotopes of concern produce alpha decay, which is of little concern outside the body, but lethal once inside it.By Soylent
Tue May 06 12:01:33 BST 2008
U-238 has a half-life of 4.5 billion years and U-235 0.7 billion years. In natural uranium you find only 0.7% U-235; in depleted uranium it's some 0.2-0.3%. Ingesting or inhailing significant amounts of uranium, natural or depleted, poses a toxicological rather than radiological threat.All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
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