Trees Doing the Dirty Work: Using Plants to Clear Toxic Mercury from Soil

Larchmont Scientist Researches Phytoremediation

by Paula Eisenberg

Larchmont's Dr. Ruth Gyure with associates Dr. Thomas Philbrick and Dr. Edwin Wong, Western Connecticut State University

(April 1, 2003) From the late nineteenth century into the mid-twentieth, Danbury, CT was a center of hat-making. During those decades, a toxic by-product of the trade was building up in the soil of downtown Danbury: nitrate of mercury, which was used to process beaver fur, sickened workers and poisoned the soil under the hat factories. Toxic though the soil is, various plants and weeds grow there, and they might turn out to be part of a clean-up solution. A Larchmont resident, Dr. Ruth Gyure, is part of a Western Connecticut State University research project seeking a way to use plants to remove contaminants from soil, a process called phytoremediation.

Dr. Gyure's lab is working with the City of Danbury, aided by a grant from the Environmental Protection Agency (EPA), to reclaim the 1/2 acre vacant lot near the university's campus. Digging up the toxic soil and removing it would be too expensive, so Danbury officials approached the university's biological and environmental sciences department for help.

If the plan works, newly planted trees would put down roots into the contaminated soil, draw the mercury up into the very wood, and hold it until later harvesting and safe disposal. The method can also work with other kinds of plants against other contaminants, including lead and petroleum.

Dr. Gyure, a microbial ecologist, is focusing on the contents of the soil itself. "There are thousands of different species of bacteria in the soil," she said. "I believe the bacteria are the primary players in the process of phytoremediation, and we need to learn how to get them to convert mercury to a safe form. We need to learn how to get the soil to release the mercury so the plants can take it up." She told the Gazette that the trees, primarily cottonwoods, will be planted later this spring. They and the soil and air will be monitored for at least the next three years to determine how much mercury is being removed from the soil, and whether it is escaping into the air.

Dr. Ruth Gyure in her Larchmont garden

The research could prove important in the global effort to clean up "brownfield" sites, those with moderate or low levels of contamination. Dr. Gyure and a graduate student will present a paper on the team's work at a national microbiology conference in May in Washington, DC.

Dr. Gyure grew up in Indiana and earned her B.S. and Ph.D. degrees from Purdue University. In the early 1980's, she served in the Peace Corps in the Central African Republic as an acquaculture specialist. She and her family moved here from Madison, Wisonsin, eight years ago. She serves on the board of the Sheldrake Environmental Center, and loves cycling and camping with her husband and teenage daughter. And even though her work requires a certain amount of digging in the dirt, in her free time she still enjoys rooting around in her own organic garden.