Plant enhanced degradation of phenanthrene in the contaminated soil

The degradative characteristics of phenanthrene, microbial biomass car bon, plate counts of heterotrophic bacteria and most probable number (MPN) of ph enanthrene degraders in non-rhizosphere or rhizosphere soils with uninoculating or inoculating phenanthrene degraders were measured. At the initial concentratio n of 20 mg phenanthrene/kg soil, the half-lives of phenanthrene in uninoculated non-rhizosphere soil, uninoculated rhizosphere soil, inoculated non-rhizosphere soil, and inoculated rhizosphere soil were measured to be 81.5, 47.8, 15.1 and 6 .4 d, respectively, and corresponding kinetic data fitted first-order kinetics. The highest degradation rate of phenanthrene was observed in inoculated rhizosph ere soil. The degradative characteristics of phenanthrene were closely related t o the effects of vegetation on soil microbial process. Vegetation could enhance the magnitude of rhizosphere microbial communities, microbial biomass content, a nd heterotrophic bacterial community, but barely influence those community compo nents responsible for phenanthrene degradation. Results suggested that combinati on of vegetation and inoculation with degrading microorganisms of target organic contaminants was a better pathway to enhance degradation of the organic contami nants in soil.