Effects Of Arbuscular Mycorrhizal Fungi On Bioremediation Of Heavy Metals Contaminated Soil

Heavy metal pollution is a worldwide problem,and the large area and variety of heavy metal contaminated soils in China have seriously affected ecosystem security and human health.Phytoextraction using hyperaccumulators is one of the effective measures to remediate heavy metal pollution in soil,but it cannot be widely applied due to factors such as low plant biomass and low growth rate.How to improve the efficiency of bioremediation of heavy metal contaminated soils is an important issue that needs to be addressed.Arbuscular mycorrhiza fungi(AMF)form a symbiotic relationship with most terrestrial plant species,which can not only improve plant nutrition,but also enhance the host plant resistance to heavy metals,and have good prospects for application in bioremediation of heavy metal contaminated soil.However,there is a lack of uniform understanding and reports on the bioremediation effects of AMF on heavy metal contaminated soils,mainly attributed to the differences in different plant types,AMF species and soil physicochemical properties in various studies.Through data analysis,it is important to clarify the remediation effect of AMF on heavy metal contaminated soils and to screen out an effective combined plant-microbial remediation system for bioremediation of different heavy metal contaminated soils.In this study,we used a Hierarchical Meta-analysis to analyze the bioremediation effect of AMF on cadmium,lead and arsenic contaminated soil with more serious pollution,and to investigate the effects and mechanism of AMF on host plant growth and heavy metal uptake with the characteristics of plant biomass,nutrient(phosphorus)uptake,heavy metal uptake and transport,and plant antioxidant indices;using Meta-regressions to clarify the effects of soil heavy metal concentration,soil p H,soil organic matter,and AMF colonization on the remediation effect of AMF;by model selection and model-averaged importance of terms,the key factors affecting plant biomass,phosphorus concentration,and heavy metal uptake by AMF were identified.The optimization conditions for the combined remediation of heavy metal contaminated soil by AMF and hyperaccumulators were screened,providing theoretical guidance for the application of AMF in heavy metal soil pollution remediation.The main conclusions obtained are as follows:(1)AMF significantly improve plant biomass in cadmium,lead,and arsenic contaminated soil and slow down the toxic effects of heavy metals.Inoculating AMF significantly increased the biomass,phosphorus concentration,and antioxidant enzyme activity of shoot and root of plants in polluted soil,reduced the translocation factor of heavy metals from root to shoot,and significantly decreased the content of malondialdehyde,a marker of lipid peroxidation in the cell membrane of plant.(2)The effect of AMF on hyperaccumulators and non-hyperaccumulators was different.The inhibition of transport of Cd,Pb and As from root to shoot of non-hyperaccumulators by AMF was significantly greater than that of hyperaccumulators,and the translocation factor were reduced by 14.31%(non-hyperaccumulators)and10.18%(hyperaccumulators),respectively,compared to uninoculated.The effect of AMF on Cd transport was more significant,with the translocation factor reduced by 23.04%(non-hyperaccumulators)and 14.18%(hyperaccumulators),respectively;the combined effect of AMF on plant biomass showed that inoculation with AMF significantly increased the shoot heavy metal uptake of hyperaccumulators,and the total effect on Cd,Pb,and As uptake increased by 36.12% compared with that of non-inoculated plants,which improved the restoration efficiency of hyperaccumulators;AMF significantly reduced the transport of heavy metals to shoot of non-hyperaccumulators.The AMF significantly reduced the transport of heavy metals from root to shoot,diluted the concentration of heavy metals in shoot,and slowed down the toxic effect.(3)AMF Glomus versiforme,Funneliformis mosseae have good potential for application in bioremediation of heavy metal contaminated soil.Compared with uninoculated,the total effect of hyperaccumulators inoculated with G.versiforme and F.mosseae on the extraction of Cd,Pb and As increased by 58.2% and 45.74% in shoot and61.3% and 37.7% in root,respectively;inoculation with G.versiforme and F.mosseae increased the uptake of Cd in root of hyperaccumulators by the inoculation of G.versiforme and F.mosseae increased the cadmium uptake in root of hyperaccumulators by84.23% and 38.66%,respectively;G.versiforme increased the cadmium extraction in shoot by 47.86%,and F.mosseae had no significant effect on the cadmium uptake in shoot.(4)There were differences in the optimal conditions for the combined remediation of cadmium and lead contaminated soil by AMF and hyperaccumulators.In cadmium-contaminated soil,the remediation effect was better under weak acidic and weak alkaline conditions,and AMF increased shoot biomass and cadmium uptake by40.28% and 46.83%,respectively(p>0.05);Solanaceae increased shoot biomass and cadmium uptake by 48.38% and 30.06%,respectively,and was the best plant type for remediation of cadmium-contaminated soil.In lead-contaminated soil,the remediation effect was better under alkaline conditions,and AMF increased shoot biomass and lead uptake of hyperaccumulators by 54.05% and 65.11%;the shoot biomass and cadmium uptake of Asteraceae increased by 14.57% and 45.9%,respectively,indicating better remediation effects on lead contaminated soil.