Plants suck metal from polluted land: The British Association for the Advancement of Science annual meeting

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The Independent Online
PLANTS that 'suck' valuable metals out of polluted soil could provide a lucrative crop for the future, scientists said yesterday.

Lead in land around Britain's abandoned smelting mines, or sprinkled for years on roadside verges, could be siphoned up, leaving clean, fertile soil.

Steven McGrath, from the Agricultural and Food Research Council's Institute for Arable Crops Research in Hertfordshire, told the meeting that such 'hyper-accumulators' can store thousands of times more metal than 'normal' species. The latex in one example, Sebertia acuminata, a native of metal-rich soils, can be 11 per cent nickel. It might be possible to tap these trees for nickel as others are tapped for rubber.

Scraping one metre of topsoil off a polluted site produces around 3,000 tons of metal-contaminated soil per hectare. This dries down to just a few kilograms of ash with metal concentrations of up to 20 per cent.

'We are told by people who do smelting that this is equivalent to a good ore,' Dr McGrath said. He said Dupont, the United States chemical giant, is interested in using his 'bio-ore' techniques to clean up land contaminated with lead.

'Around Britain's cities, metal industries have produced haloes of land polluted with metal deposits. The old mining sites where they smelted the lead emitted a lot of metal which came down on hills and moors,' Dr McGrath said.

Dr McGrath's team tested 10 plant species on a site contaminated with 20 years' worth of London sludge and recorded the take-up of metals such as zinc, copper, manganese and cadmium. The researchers found that three species - a close relative of alyssum, an alpine penny cress and northern rock cress - had an unusually large capacity for storing metals.

He is confident that the work, funded in part by the US Army, should produce a cheaper way to deal with polluted land than any of today's approaches.