Studies On Bioremediation Of Arbuscular Mycorrhizal Fungi In Heavy Metal And Rare Earth Element-Contaminated Soil

Heavy metal pollution in soil has become more and more severe. For heavy metals can not be decomposed in the environment, heavy metal pollution has been a global problem threating to the environment.Arbuscular mycorrhizas (AM) are the symbiosis between majority of land plants and arbuscular mycorrhiza fungi. AM not only can improve plant nutrition, but also can promote plant resistance to stress. The aim of this study were: (1) to investigate mycorrhizal infection process of AM fungi G. intraradices on Astragalus sinicus L. and activities of fungal succinate dehydrogenase (SDH) and alkaline phosphatase (ALP) at different time; (2) to study the effect of mycorrhizal infection on the uptake of heavy metals and plant growth in heavy metals polluted soil; (3) to study the effect of inoculation with AM fungi and phosphate-solubilizing bacteria on plant growth and phosphorus uptake of A. sinicus. The main results of this study are as follows:The activities of SDH and ALP were positively related with plant dry matter. The higher the activities, the higher the dry matter. The activities of SDH and ALP were highest at 6 weeks and decreased at 9 weeks. While the infection rates of AM fungi were still higher at 9 weeks.Phosphate-solubilizing bacteria had evident effect on phosphate rock dissolving. Inocultion with AM fungi or phosphate-solubilizing bacteria in phosphate rock amended soil significantly improved phosphate uptake by A. sinicus. Co-inoculation with AM fungi and phosphate-solubilizing bacteria had more significant effect than single inoculation. Cu treatment decreased mycorrhizal infection and plant biomass of A. sinicus.Mycorrhizal infection decreased pH value in pot soil and enhanced the content of the exchangeable Cu in soil. Mycorrhizal treatment increased the uptake of Cu by A. sinicus. Inoculation with G. intraradices lowered Cu transferring from root to shoot and improved nutrient elements uptake, so plants inoculated with G. intraradices had higher biomass. Inoculation with G. mosseae accelerated Cu transferring from root to shoot and plants inoculated with G. mosseae had lower biomass. The infection rates of AM fungi were decreased with the increase of Cu added in soil, and the enzyme activities of SDH and ALP were decreased also. Cu in soil inhibited P and K uptake by A. sinicus, while mycorrhizal treatments improved P and K uptake.Increasing La concentrations in soil led to increased La accumulation in tissues of both mycorrhizal and non-mycorrhizal plants, but inoculation with Gig. margarita or G. intraradices reduced La concentrations in shoots and roots at higher concentrations of La in the soil. La treatments inhibited mycorrhizal infection and activities of SDH and ALP. Nutrient elements uptake were reduced by La application, but increased by inoculation with Gig. margarita or G. intraradices.Inoculation with G. mosseae in Cd and Zn polluted soil decreased Cd and Zn concentrations in shoots of maize and enhanced Zn accumulated in roots.In conclusion, appropriate AM fungi treatment in heavy metal or La polluted soil could be effective in alleviating heavy metal or La toxicity to the host. AM fungi infection could enhanced heavy metal accumulate in roots which is very important for phytoremediation in heavy metal polluted soil.