October 28, 2004 Think toxins in your soil are scary? Maybe you should grow a pumpkin patch.
That’s what a recent study, conducted by Kenneth Reimer and two of his colleagues at the Royal Military College of Canada, suggests. According to the report, a pumpkin plant can remove significant amounts of DDT and other harmful pollutants from contaminated soil.
Reimer’s experiment lends credence to the emerging technology of phytoremediation—a biological process by which certain plants extract chemicals from soil, sediment, or water. Of the five plant varieties Reimer’s group tested, pumpkin plants extracted the most DDT, and their close relative—the zucchini—came in second.
DDT and other persistent organic pollutants (POPs) are especially difficult to remove from contaminated soil because they do not dissolve in water, a condition that makes them become more deeply attached to the soil’s organic matter as time passes.
DDT was introduced around the time of World War II as a popular insecticide, as well as an effective combatant against carriers of typhus and malaria. However, after its ability to endure for long periods of time in the environment—and the subsequent negative health consequences for humans and animals alike—became known, the chemical was banned in the United States and other countries. Some developing nations, however, still rely on DDT for disease protection.
For their study, Reimer and his colleagues took soil from a site in the western Canadian Arctic that had been exposed to DDT between 1947 and 1950, and then grew selected plants in the sample soil in a greenhouse during the summer of 2002 and the winter of 2003.
According to an early draft of Reimer’s report—which will be published in the November 15 edition of Environmental Science & Technology—size was an important factor in the success of the pumpkin and zucchini plants as cleanup agents. Both plants have a large above-ground biomass, as well as leaves with greater surface areas—a physiology that enables them to accumulate larger amounts of DDT and perhaps also translocate it more easily.
But while the plants can take pollutants out of the soil, they can’t get rid of them. Reimer said the next step would be to segregate the contaminated plants and compost them into a residue that could be sent to a more conventional location for disposal, such as a landfill or incinerator.
“So, you’re using the plant as an extraction mechanism,” Reimer told Outside.
When asked about the practicality of applying his findings to the world’s large-scale problem of soil contamination, Reimer said, “I think [the study] shows some promise. We’re still a ways from the marketplace.”
In order for pumpkins, zucchinis, and other special plants to do their work, Reimer said they need more time compared to the alternative solution, which is to dig up all the soil in the contaminated area and put it in an incinerator. For sites that need quick cleaning, he said, the latter is still a better option.
Still, Reimer’s findings mark an important step in the emergence of phytoremediation as a solution to contamination problems.
“For us, dealing with organochlorines—which are some of the most persistent pollutants in the environment—is really exciting,” he told Outside.
Obaid Faroon, from the U.S. Agency for Toxic Substances and Disease Registry, told Outside that while the details behind Reimer’s study are still forthcoming, “According to this report, it’s very promising.”
