Promotion of pyrene removal from soils by plant-microbial association

Pyrene-degrading bacteria along with alfalfa were studied for their potential in removal of pyrene contamination from soil.43.49% of pyrene was degraded by P6-alfalfa association at 20 d.In contrast,23.46% and 15.21% of pyrene was only removed by strain P6 and alfalfa,respectively.It was indicated that the P6-alfalfa association was more effective in removal of pyrene.The pyrene was also both detected in the shoots and roots of alfalfa,and more pyrene was accumulated in the roots than those in the shoots.Through analysis of pathways of pyrene removal,this enhanced removal of pyrene by plant-microbial association might be the result of alfalfa promoted microbial degradation.The POD(peroxidase)in plant roots was higher than that in shoots,and the PPO(phenol oxidase)in roots was lower than that in shoots.The catalase and polyphenol oxidase activities in soil were both higher in planted soil than unplanted soil.And the bacterial populations in soil,especially in rhizosphere were also inspired by the growth of alfalfa.These could be explained by the rhizosphere effect.This enhanced dissipation of pyrene in planted soil might be due to increased biological activity in the rhizosphere.Therefore,bio-removal of pyrene in the contaminated soils was feasible using alfalfa.