Methods of Soil Environmental Remediation - Environmental Geomechanics - page 443

15.5.6. Phytoremediation
This process gathers all the techniques using plants to transform, degrade,
concentrate, stabilize or volitalize pollutants. It is a complex method of
environmental remediation that cannot be reduced to sowing seeds. Existing
technologies include:
− phytoextraction : use of accumulating plants to extract, transport and
concentrate ground pollutants in the parts fo the plant that can be harvested;
− phytostabilization : use of plants to reduce the bioavailability, mobilization or
scrubbing of pollutants;
− rhizofiltration : use of the roots to absorb, concentrate or precipitate the
pollutants of a liquid waste;
− phytovolatization : stimulation of volatilization by means of plants that absorb
the pollutants then eliminate them by perspiration;
− phytodegradation : transformation of the organic compounds of the pollutant
by means of biochemical reactions generated by the many enzymes contained in
plants;
− degrading activity of the rhizosphere : use of plants to stimulate the micro-
organisms present in the rhizosphere, thus generating a higher biodegrading activity.
15.6. Conclusions
There are various methods of environmental remediation. Different designs aim
to immobilize, destroy or remobilize contaminants. They are based on multiple
processes: biological, physicochemical, thermal and electrokinetic. The choice of a
particular environmental remediation technique should not be made at random but
must be carefully considered since the choice of technique is based on the results of
methods used to detect pollution. It requires a good comprehension of the specific
problems (pollutants, environment of pollution) and/or an excellent cost-
effectiveness ratio. The choice of environmental remediation technique thus requires
us to take account of its cost, feasibility, implementation time, duration of
exploitation and risks to the environment due to rehabilitation.
A summary of environmental remediation techniques for contaminated media is
given in Table 15.12. Complex contamination problems frequently require the use of
a combination of techniques. An effective cure therefore often requires solutions that
fulfil the specific requirements of the media involved.