A U.S. study suggested that plants might be an effective method of removing toxins from contaminated soils by a process called phytoremediation.

"There are some really cool plants out there that will not only tolerate very toxic soils but will accumulate some of those metals to very high levels in the shoot," said Professor Leon Kochian, director of the U.S. Plant, Soil and Nutrition Laboratory located at Cornell University. He noted, as an example, Thlaspi caerulescens, a member of the cabbage family also known as Alpine pennycress.

Kochian said Thlaspi accumulates metals to "astounding levels," packing its leaves with 30,000 to 40,000 parts per million of zinc and 10,000 to 20,000 parts per million of cadmium.

Although the weed is too small to have a meaningful impact on a heavily polluted site, Kochian is trying to identify the molecular mechanisms that allow Thlaspi to tolerate having up to 4 percent of its leaf mass consist of very toxic metals.

"We have found a couple of membrane transporter genes that look really interesting," he said. "The idea is to identify a suite of hyperaccumulation genes and transfer them into a plant with bigger biomass."