ABSTRACT
An increasingly industrialized global economy and rapid rise in world population over the last century have led to dramatically elevated releases of anthropogenic chemicals, particularly heavy metals, into the environment. Heavy metal-contaminated soils have caused serious problems threatening ecological systems and human health, and have recently attracted considerable public attention. Concentrations of heavy metals that have exceeded safety levels in soil should be treated (Baker et al. 1994). There are several methods used for soil remediation, including chemical, physical and biological techniques. Physical treatments involve removal from contaminated sites (soil excavation), deep burial (land —lling) and capping, while chemical methods use strong acids and chelators to wash polluted soils. These approaches are expensive, impractical and at times impossible to carry out, as the volume of contaminated materials is very large. Furthermore, they irreversibly affect soil properties, destroy biodiversity and may render the soil useless as a medium for plant growth. Recently, phytoremediation, a diverse collection of plant-based technologies to clean contaminated environments, using either naturally occurring or genetically engineered plants (Cunningham et al. 1997) represents a novel, environmentally friendly and cost-effective technology. Importantly, byproducts of phytoremediation can —nd a range of other uses.
