"Phytoremediation or the use of plants to degrade, extract, contain or immobilize contaminants is a new soft technology that is increasingly being studied as a low-cost approach to remediation Physical containment of contaminants by plants can take the form of binding the contaminants within a humic molecule (humification), physical sequestration of metals as occurs in some wetlands, or by root accumulation in nonharvestable plants. Certain trees sequester large concentrations of metals in their roots, and although harvesting and removal is difficult or impractical, the contaminants present a reduced human or environmental risk while they are bound in the roots. Risk reduction may also be achieved by transforming the contaminant into a form that is not hazardous, or by rendering the contaminant nonbiodegradeable."
This is being tested on Nuclear Waste and positive results have emerged from the use of Popular Trees and Sunflower Plants.