Plant-assisted bioremediation as a green technology for recovering soil from PCB contamination

Bioremediation is an increasingly popular alternative to conventional methods for treating waste compounds, in line with environmental sustainability, with the possibility to degrade contaminants using natural microbial activity mediated by different consortia of microbial strains. Among the techniques of so-called green remediation, plant-assisted bioremediation seems to be one of the most promising techniques. Plant-assisted bioremediation is a technology that exploits the synergistic actions that are established in the rhizosphere between plant roots and microorganisms in order to remove, transform or immobilize toxic substances. The presence of plant species through the roots promotes the modification of the physico-chemical properties of contaminated soils as well as the release of root exudates. Organic pollutants may be partially co-metabolic degraded by root enzymes and/or completely biodegraded by microorganisms in the rhizosphere. The phytoremediation effectiveness depend on the use of plant species tolerant to the toxic effects of contaminants in the soil and with roots able to promote the development of a microbial community capable of supporting the degradation of the contaminant in the rhizosphere. This technique is used in preliminary experiments, one in the field and in two in greenhouse, using a soil diffusely contaminated by PCBs in which different plant species were tested. In the field experiment, two tree species (Tamarix gallica and clone Monviso of the genus Populus), were used. At the same time, soil microcosms were set up in greenhouse in order to study in detail the possible PCB degradation processes that occur in the rhizosphere. For this purpose, some microcosms were prepared in the presence/absence of Medicago sativa specie and others in the presence of the Monviso clone, the same used in the field experiment. In this work we describe the various experiments and their main results.