Dainty Plant Can Power-Clean Cadmium-Contaminated Soils

By Sharon Durham
September 10, 2004

Delicate, white flowers belie the ability of the small plant called alpine pennycress to lift huge amounts of cadmium from contaminated soil. Agricultural Research Service agronomist Rufus Chaney, of the Animal Manure and By-Products Laboratory in Beltsville, Md., and a group of international scientists have found the plant can concentrate about 8,000 parts per million of cadmium in its leaves.

Cadmium is a naturally occurring element that is widely distributed in the Earth's crust, but zinc mining and smelting wastes can cause high cadmium contamination.

In 1992, the team of scientists from ARS, the University of Maryland, the University of Melbourne-Australia and Massey University-New Zealand began working with alpine pennycress (Thlaspi caerulescens), a plant capable of accumulating vast amounts of cadmium and zinc in aboveground leaves and stems. Using this plant, each year farmers could move soil metals into the harvestable plant shoots, making it possible to gradually reduce the soil concentration of cadmium to safe levels.

The cost of this remediation method, called phytoextraction, is about $250 to $1,000 per acre per year, according to Chaney. The alternative cleanup method--removal of contaminated soil and replacement with clean soil--costs about $1 million per acre. Most highly contaminated soils can be deemed safe after 10 years of phytoextraction, thus producing an effective cleanup at a far lower cost.

In 2000, a patent was filed by the University of Maryland on the use of alpine pennycress to remove cadmium from soil. No other similar technologies currently exist for remediation of cadmium-contaminated soils using plants. Cadmium phytoextraction using alpine pennycress has since been licensed to Phytoextraction Associates, LLC, of Baltimore, Md., which will soon conduct a commercial demonstration of the process.

Research is under way to develop a "super" phytoextraction plant.

Chaney's research is described in the September issue of Agricultural Research magazine.

ARS is the chief scientific research agency of the U.S. Department of Agriculture.