PHYTOREMEDIATION: AN EMERGING TECHNOLOGY FOR CONTAMINATED SITES

J.L. Schnoor, L.A. Licht, S.C. McCutcheon, N.L. Wolfe and L.H. Carriera
Department of Civil and Environmental Engineering, The University of Iowa, Iowa City, IA, 52242, 319-335-5649 and U.S. Environmental Protection Agency, Environmental Research Laboratory, Athens, GA, 30605, 706-546-3301

ABSTRACT

Phytoremediation is an emerging technology for contaminated sites that is attractive due to its low cost and versatility. It is a form of ecological engineering that has proven effective in several full-scale applications of shallow contaminated sites. Plants have the ability to withstand greater concentrations of organic pollutants than most microorganisms, and they can take up chemicals quickly and convert them to less toxic metabolites. In addition, they stimulate degradation of organic chemicals in the rhizosphere by root exudates, enzymes, the build-up of organic carbon in the soil, and the enrichment of rhizosphere microbial communities.

In this paper, the direct uptake of organic chemicals by plants and enzyme activity, both within the plants and from exudates, will be discussed. Nitroreductase, dehalogenase, laccase, peroxidase and nitrilase activity have been examined for a number of plant species at the EPA Environmental Research Laboratory in Athens, Georgia. Full scale applications of hybrid poplar trees have been used by investigators at The University of Iowa to take up excess nutrients and atrazine in agricultural runoff, to close and cap landfills, and to treat landfill leachate. Trinitrotoluene (TNT) and ammunition wastes are a candidate for remediation using this technology.

Key words: phytoremediation, exudates, enzymes, plants, organics