harvested. Then plants can be either burned orsold. Even if the plants cannot be used, incineration and disposal of the plants is still cheaperthan traditional remediation methods. As a comparison, it is estimated a site containing 5000tons of contaminated soil will produce only 20-30 tons of ash (Black, 1995). This method isparticularly useful when remediating metals. Some metals are also being recycled from the ash.Phytovolatization is the uptake and vaporization of pollutants by a plant. This mechanism takes asolid or liquid contaminant and transforms it to an airborne vapor. The vapor can either be thepure pollutant, or the plant can metabolize the pollutant before it is vaporized, as in the case ofmercury, lead and selenium (Ackerman, 1996). Phytodegradation is plants metabolizingpollutants. After the contaminant has been drawn into the plant, it assimilates into plant tissue,where the plant then degrades the pollutant. This metabolization by plant-derived enzymes suchas nitrosedictase, laccase, dehalogenase, and nitrilase assimilates into plant tissue, where theplant then degrades the pollutant. This metabolization by plant-derived enzymes such asnitroredictase, laccase, dehalogenase, and nitrilase, has yet to be fully documented, but has beendemonstrated in field studies (Boyajian and Carriera, 1997). The daughter compounds can beeither volatized or stored in the plant. If the daughter compounds are relatively benign, the plantscan still be used in traditional applications. The most effective current phytoremediation sites inpractice combine these three mechanisms to clean up a site. For example, poplar trees canaccumulate, degrade and volatize the pollutants in the remediation of organics. Phytoremediation is more than just planting and letting the foliage grow; the site mustbe engineered to prevent erosion and flooding and maximize pollutant uptake. There are 3 mainplanting techniques for phytoremediation. The first is growing ...
