Bioremediation of soil and water: application to chemical and nuclear pollutions

Bioremediation is a branch of biotechnology that uses natural or diverted biological mechanisms to address environmental problems. The biological agents can be simple organic molecules, such as DNA or antibodies, or live or dead organisms (bacteria, microalgae, fungi, higher algae and plants). Phyto-remediation refers more specifically to using plants to decontaminate polluted soil, water, or air. Unlike organic pollutants such as PCBs1, TNT2, TCE3, which can be metabolized by soil microorganisms and plant roots, radionuclides - like most heavy metals - cannot be degraded. Thus, bioremediation strategies for radionuclides will consist into: - stabilization/mineralization to reduce their bioavailability through a change in their redox state; - for soil, their extraction using the plant nutrition mechanisms; - for polluted solutions, their extraction using the 'cation traps' properties of plant cell walls. Compared to physicochemical methods conventionally used to decontaminate soils but which lead to a sharp decline in fertility and productivity, bioremediation is considered a friendly environmental technology. An important advantage of this technique is its cost, much lower than traditional remediation techniques. By cons, bioremediation cannot be applied in an emergency, because processing times are spread over several years - even decades - depending on the degree of pollution. Therefore current research focuses on optimizing the processing time. We present in this paper several examples of in situ bioremediation of heavy metals and radionuclides, and we discuss in conclusion the negative and positive aspects of this technique. (author)