Phytoremediation Applications for Removing Heavy Metal Contamination from Soil and Water

Abstract

6 Over the past several years, scientists have discovered many examples of living plants that can remove heavy metals and other pollutants from soil and water. This potential approach to cleaning the environment, termed phytoremediation, draws on our centuries of experience in cultivating crops and is emerging as a low cost treatment technology. The idea that plants can be used for environmental remediation is not new. Extensive research on using plants and entire ecosystems for treating radionuclide contamination took place in Russia in the early 1960s (Timofeev-Resovsky, et aI., 1962). Since then, there have been a number of reports that aquatic plants such as water hyacinth, duckweed and water velvet can accumulate Pb, Cu, Cd, Fe, and Hg from contaminated water (Mo, et aI., 1989; Jackson, et aI., 1990; Dierberg, et aI., 1987). This ability is currently utilized in many constructed wetlands, which can be effective in removing some heavy metals and organics from water (Jain, et aI., 1989). The ability of plants to accumulate metals has usually been considered a detrimental trait. Metal-accumulating plants are directly or indirectly responsible for a proportion of the dietary uptake of toxic heavy metals by humans and other animals (Brown, et aI., 1994). While some heavy metals are required for life, their excessive accumulation in living organisms is always toxic, and is aggravated by their almost indefinite persistence in the environment. Recently the value of metal-accumulating terrestrial plants for environmental reme-diation has also been recognized (Baker, et aI., 1988; Cunningham, et aI., 1993; Wenzel, et aI., 1993). Crop plants such as Indian mustard have been used to extract heavy metals from soil and sediments and translocate those metals to the harvestable stalks and leaves of the plants (Raskin, et aI., 1994). This application, called phytoextraction, may be used in the removal of heavy metals in soils, sludges and sediments.