Habitat restoration of contaminated soils

In addition to our efforts to use plants to remove toxic elements from contaminated sites, we are also interested in using plants to stabilize the contaminants in situ (phytostabilization). This is to prevent migration of contaminants to the ground water or their indiscriminate dispersal to the atmosphere via soil erosion and wind. The goal of this project is to determine suitable soil amendment treatments, as well as identifying appropriate plant species, necessary to revegetate a barren site.

A chemical company near San Francisco Bay was faced with such a problem: the site was contaminated with arsenic, mercury, lead, and selenium, PCBs and PAHs, that it was unable to support any vegetation. There was a serious risk that the contaminants would be distributed well beyond the contaminated area through soil erosion and wind or by drainage to the groundwater. In order to phytostabilize the site, we first conducted soil characterization experiments and determined pH, heavy metal content, and nutritional status. We then tested different types of soil amendments to improve soil quality so as to support vegetative growth. Using dolomite and organic fertilizer we were able to effectively reduce soil acidity and ameliorate soil conditions to obtain optimum plant growth. Among the various species tested, fawn tall fescue was the most tolerant species and was chosen for the phytorestoration of the contaminated site.