Volume 56 (2010) Issue 3 Pages 257-266
To improve phytoremediation efficiency of polycyclic aromatic hydrocarbons (PAHs), pot experiment was conducted to introduce arbuscular mycorrhizal fungi, aromatic hyrocarbon degrading bacteria (ARDB), and rhamnolipids into phytoremediation system. Alfalfa biomasses, the number of heterotrophs and ARDB, dehydrogenase activity, polyphenol oxidase activity and residual PAHs concentration were determined after 90 days of alfalfa growth. The results indicated that the average removal efficiency of total PAHs by multi-technique phytoremediation system reached to 60.48%, which was 251.83% greater than that of phytoremediation itself (17.19%). Importantly, the multi-process system was capable of removing most of the high molecular weight PAHs (HMW-PAHs) from soil, the highest average removal percentage of HMW-PAHs, such as fluoranthene, pyrene and benzo[a]pyrene were 89.39%, 88.36% and 92.31%, respectively. A sharp increase in the size of the heterotrophic and aromatic hyrocarbon degrading microbial populations was observed, which resulted in increase of soil dehydrogenase and polyphenol oxidase activities. The key elements for successful phytoremediation were the use of biosurfactant that increase bioavaliable of PAHs in soil, and inoculation of microorganisms (arbuscular mycorrhizal fungi and ARDB) that accelerate plant growth and increase PAHs removal from heavily contaminated soils. The synergistic use of these approaches resulted in rapid and massive biomass accumulation of plant tissue in contaminated soil, putative providing more active metabolic process, and led to more rapid and more complete removal of PAHs.