Soils frequently receive a wide range of contaminants from industrial activities, sewage sludge disposal, metal processing, and energy production, and in many cases remediation is both expensive and intrusive to the ecosystem. Phytoremediation is the use of plants and plant processes to remove, degrade, or render harmless hazardous materials present in the soil or groundwater. Phytoremediation can occur through a series of complex intereactions between plants, microbes, and the soil, including accumulation, hyperaccumulation, exclusion, volatilization, and degradation.
Plants also stabilize mobile contaminated sediments by forming dense root mats under the surface.
The science of phytoremediation arose from the study of heavy metal tolerance in plants in the late 1980s. The discovery of hyperaccumulator plants, which contain levels of heavy metals that would be highly toxic to other plants, prompted the idea of using certain plant species to extract metals from the soil and, in the process, clean up soil for other less tolerant plants. Scientists also found that certain plants could degrade organic contaminants by absorbing them from the soil and metabolizing them into less harmful chemicals. In many cases, even the physical presence of a plant can improve the condition of the soil, giving it structure and stability and altering hydrology by enhancing water retention and preventing erosion. There is no doubt that plants and the microbes associated with them can profoundly alter an ecosystem.