[Interaction of biosurfactant-microorganism to enhance phytoremediation of aged polycyclic aromatic hydrocarbons (PAHS) contaminated soils with alfalfa (Medicago sativa L.)].

A pot experiment in greenhouse was carried out to investigate the interactive effect of rhamnolipids (RH) addition and PAHs-specific degrading bacteria (DB) inoculation on the phytoremediation efficiency for removal polycyclic aromatic hydrocarbons (PAHs) from agricultural soils. Results indicated that RH addition and DB inoculation promoted alfalfa (Medicago sativa L. ) growth and PAHs degradation in the soil. After 90 days, residual PAHs concentration in soil reduced 30.0% and 49.6% for the treatment of RH and DB, respectively, but only 21.7% for control. For the treatment of RH + DB, residual PAHs concentration in soil reduced 53.9%, showing synergy effect of RH addition and DB inoculation. In addition, the average PAHs degradation gradually reduced with the increase of the PAHs rings, but DB inoculation promoted the degradation of four-ring PAHs and five-ring PAHs. The number of PAHs degrading bacteria and dehydrogenase activity increased with the removal ratio of PAHs. Therefore RH addition and PAHs-specific degrading bacteria inoculation were effective in enhancing the phytoremediation efficiency of the long-term PAHs contaminated soils.