Soil is a complex system in which the plant rhizosphere acts as an efficient bioreactor able to accelerating the degradation of xenobiotic such as PAH. Rhizosphere microbial activities of an urban polluted site were monitored during the phytoremediation using Festuca arundinacea Schreb. The seasonal changes of microbial biomass, degradation specificity and efficiency of enzymatic processes of soil contaminated with a mixture of aged PAH, metals and organic pollutants were monitored and quantified. The mutagenic potential of soil extracts was assayed using different Salmonella typhimurium strains in order to assess the toxicity before and after phytoremediation. The microbial ability to degrade PAH has been evaluated using phenanthrene as the only source of carbon for microbial cultures and there was a 60% reduction in the initial phenanthrene concentration. The results of this work suggest that the enhancement of persistent PAH degradation is favoured by a robust F. arundinacea growth and by an efficient bacterial extracellular enzyme production and activity in soil. The marked removal of carcinogenic PAH by F. arundinacea rhizosphere is particularly intriguing.
