Pumpkins can clean up toxic soils

WASHINGTON, DC, October 21, 2004 (ENS): Pumpkins and zucchinis have the ability to remove DDT from soil, a chemist at the Royal Military College of Canada has found.

A greenhouse study by chemist Dr. Ken Reimer and his team suggests that phytoremediation with these plants is a environmentally friendly technique for cleaning up sites contaminated with DDT, PCBs and other harmful compounds.

Once they have taken up the contaminants, the pumpkins would not be eaten. The pumpkins would be allowed to ripen and then composted with their vines to reduce their volume before they are disposed of in landfills or incinerated.

"Our research has shown that members of the Cucurbita pepo species, including pumpkins, are particularly effective in this regard," Reimer says. "Phytoremediation offers a green solution to cleaning up contaminated sites."

The report is scheduled to appear in the November 15 edition of "Environmental Science & Technology," a peer-reviewed journal of the American Chemical Society headquartered in Washington, DC.

DDT was applied widely as an insecticide in North America until it was banned in 1972. Some developing nations still use DDT for protection against typhus and malaria, and it endures for long periods of time in the environment, posing a potential health threat to humans and animals.

Persistent organic pollutants like DDT, PCBs and dioxins are difficult to remove from soils because they are not water soluble, and the difficulty increases with the passage of time. To clean up contaminated sites, it has been necessary to excavate the soil and place it in a landfill or burn it in a high temperature incinerator.

Reimer and his coworkers, Alissa Lunney and Barbara Zeeb, conducted a greenhouse study of five plant species: rye grass, tall fescue, alfalfa, zucchini and pumpkin. The researchers used soil from a site in the Canadian Arctic where DDT had been sprayed to protect workers from mosquitoes.

"The cold temperatures meant that the contamination was virtually identical to the technical grade DDT mixture that had originally been used," Reimer says. The researchers were able to examine the ability of the test plants to remove DDT from soil that had been contaminated for several decades.

Pumpkins took up the largest amount of DDT, while another member of the Cucurbita pepo species, zucchini, came in second at about half the pumpkins’ accumulation.

While the technique is not likely to replace traditional methods any time soon, Reimer says, phytoremediation could offer an inexpensive and environmentally friendly alternative, especially in small communities and developing countries where money is an obstacle to cleanup.



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