Friday, June 19, 2009

Phytoremediate Explosives - Plant Grass - for a Quick Solution

Mounting evidence shows native grasses could destroy explosives pollution
The Kansas City Star

Missouri researchers are investigating whether native grasses can clean up pollution caused by explosives at hundreds of locations across the country.

Besides the obvious reason, TNT is not good for you.

But grass, it turns out, might be dynamite for the problem.

TNT contaminates hundreds of sites in the US and Australia, from military firing ranges to old production dumps to waterways, and poses a threat to the human nervous system and to the liver and kidneys. It’s suspected to cause cancer. It can cause allergic reactions and attack the immune system, and it may lead to birth defects.

Left alone in the soil, TNT breaks down into an even more toxic substance.

If the problem is left in the dirt, maybe that’s where the solution can grow.

Three Missouri researchers have hit on an idea that could potentially scrub away the TNT danger:
Simply plant the right kind of grass.

The notion started with mounting evidence that native grasses could render harmless a common weed killer. That herbicide, atrazine, is the second most common herbicide used in agriculture in the U.S. and has been a stubborn pollutant in the nation’s waterways. Mounting evidence has shown that certain native grasses, and the microbes that thrive around their roots, convert the toxic leftovers from atrazine into harmless carbon dioxide.

Robert Lerch, John Yang and Chung-Ho Lin began talking about how chemically similar atrazine is to the explosives TNT and RDX. “If it worked for atrazine, we thought it might work for these things,” said Lin, a research professor for the University of Missouri Center for Agroforestry.

Should their idea succeed, it would offer a greener, cheaper and possibly quicker way to clean up more than 530 sites across the USA contaminated by the explosives.

Trinitrotoluene, or TNT, and cyclotrimethylene trinitramine, also called RDX, began creeping into U.S. soil and waterways decades ago, before the manufacturers of explosives came under stricter regulation.

The problem isn’t small. Of the 538 locations identified by the US Department of Defense with RDX or TNT contamination, 20 are Superfund sites — classified by the federal government as the country’s most dangerous abandoned toxic waste sites. Congress rejected a Pentagon proposal in 2005 to exempt the military from regulations for pollution from munitions.

“It’s a serious problem, and it’s widespread,” said Andrew Wetzler of the Natural Resources Defense Council. To clear a field tainted by those explosives — typically to haul away the dirt for incineration — can run from $100,000 to $1 million an acre.

The researchers in Columbia have doped soil samples with explosives and planted two species of grass.

In essence, the explosives practically disappear.

It’s unclear whether it’s the grasses — Eastern gamagrass and switchgrass [Panicum virgatum] seem to work best — do the work themselves, whether it’s two forms of bacteria that thrive in soils around grass roots that do the trick, or if something happens in how they work together.

But in a closet-size room basking in fluorescent lights, a solution to explosives pollution looks to be taking root.

The scientists added RDX and TNT to cup-size soil samples and planted the grasses. In just weeks, the toxic chemicals degraded harmlessly into carbon dioxide and water. “It’s a controlled situation to look at how these chemicals break down,” said Yang, the director of the Center of Environmental Sciences at Lincoln University.

The next step, perhaps still a year or two away, is to test the process outdoors.

The researchers are talking with the Army — the initial research has been covered by $110,000 in Defense Department grants — about trying the grasses on already contaminated sites.

Since the grasses are native and grow easily across the Midwest and the Southeast, they pose no threat of kudzu-like exotic species seen as their own environmental threat.

Initial tests show that the amount of RDX in soil is reduced by 50 percent in a matter of weeks, and TNT contamination drops by 95 percent. So, Lerch said, a year or two after planting, a field could be cleaned of the explosives contamination. And the cost might run less than $3,000 per acre.

“If this works, it will be great".

partially sourced ENN news
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Also interesting to note that switchgrass is also a promising third generation cellulosic source for ethanol production and is being researched extensively for that role as well.

Presumably the same process might be operating with a number of other grass species noted as being tolerant to atrazine. This could include a range of common tropical and warm temperate turf species that are tolerant to the herbicide.

Anyone in the Australian military out there that might want to fund a project here in Australia??

1 comment:

123 123 said...

Cool post as for me. It would be great to read a bit more concerning this matter. Thank you for giving this info.
Joan Stepsen
Computer geeks