For years, researchers thought plants couldn’t take up persistent organic pollutants, or POPs, since the pollutants aren’t water soluble. But, from her greenhouse in Kingston, Ontario, Barb Zeeb, a professor in the department of chemistry and chemical engineering, has succeeded in removing these industrial chemicals and pesticides from soil by using a variety of plants, including pumpkins.
Dr. Zeeb, who holds the Canada Research Chair in Biotechnologies and the Environment, says that after the POPs are taken up, the plants are composted. Called “phytoextraction,” this process preserves and ultimately improves the natural quality of the soil.
“Traditionally, we dig up the contamination and take it to a hazardous-waste dumpsite or incineration facility, but then the soil is lost,” she says. “But, in using phytoextraction … after we pull all the contaminants out, you’ve still got this natural resource of the soil itself.”
The composted material may still need to be disposed of as hazardous waste, but the volume of contaminated matter has been greatly reduced, says Dr. Zeeb.
“Just about every city in southern Ontario has brown-field sites, meaning they’ve been contaminated with industrial chemicals or pesticides over the years,” she says. “Many of them are in the hearts of their cities and they’re being hindered from development because of the legacy of contamination.”
A number of firms have already shown interest in this “green technology,” which Dr. Zeeb and her students are trying to optimize with different, bigger plants. “It’s a long-term project,” she says.