Alpine pennycress doesn't just
thrive on soils contaminated with zinc and cadmiumit cleans them up by
removing the excess metals. Click the image for more information about
Acidifying Soil Helps Plant Remove Cadmium, Zinc
Metals By Sharon
Durham June 14, 2005
Acidifying cadmium-contaminated soil can help a plant called alpine
pennycress to remove even more cadmium and zinc from contaminated soil,
Agricultural Research Service (ARS) and
cooperating scientists report.
Chaney and University of Maryland
colleagues Shengchun Wang and Scott Angle have found lowering the soil
pHincreasing its aciditycan maximize the ability of alpine
pennycress (Thlaspi caerulescens) to remove cadmium and zinc metals from
The scientists used a particular strain of alpine pennycress from
southern France in their research. In the study, they increased the acidity of
two soils collected at different fields near a zinc smelter at Palmerton, Pa.
The pH of the soils was lowered from a neutral level of 7 to an acidic level of
about 4.7 by using sulfur.
Alpine pennycress was grown on these soils for six months and then
analyzed. As the pH was lowered, concentration of cadmium in the plant shoots
rose. But if the pH was lowered below 6, the soils were so acidic that the
alpine pennycress yields were reduced.
Alpine pennycress can concentrate cadmium in its leaves up to about
8,000 parts per million. Harvesting the above-ground vegetation annually makes
it possible to gradually reduce the soil concentration of cadmium to safe
levels. The cost of this remediation method, called phytoextraction, costs
about $250 to $1,000 per acre per year, according to Chaney. He's based at the
Manure and By-Products Laboratory in Beltsville, Md.
The alternative clean-up methodremoval and replacement with
clean soilcosts about $1 million per acre. Most highly contaminated soils
can be deemed safe after three to 10 years of phytoextraction, an effective
clean-up at far lower cost. The technology will be especially useful in
cleaning up rice paddy soils in Asia, where mine waste contamination is causing
human health effects from cadmium accumulated in rice grain.
In 2000, a patent was filed by the University of Maryland on the use
of alpine pennycress for the phytoextraction of cadmium from soil, and a patent
has been granted in Australia. No other similar technologies currently exist
for remediation of cadmium contaminated soils using plants.
ARS is the U.S. Department of
Agriculture's chief in-house scientific research agency.