Bioremediation Of Cu And Zn Polluted Soil Using Arbuscular Mycorrhizal Fungi And Medicago Sativa

Soil pollution by heavy metals is a major problem in the world,because most of the heavy metals are very toxic to human health and could stay in soils for long time.Copper(Cu)and zinc(Zn)are two micronutrients important to plant growth and development in normal condition.It has been demonstrated that the contents of two metals in soils were increased in recent years.When the contents of Cu and Zn are more than the limition,most of the plants will be harmed,such as chlorotic existed,carbon fixation reduced,nutrient acquisition altered,and growth reduced.Arbuscular mycorrhizal(AM)fungi are one of the widely spread micro-organisms,which could form symbiosis with most of the vascular plants in natural or artificial ecosystem.It has been demonstrated that AM symbionts could increase the stressed ability of host plants in heavy metal polluted soil.Nowadays,using bioremediation methods to recovery heavy metal polluted soils with AM fungi has been one of the hotspots in environmental and ecological science.On the basis of this,alfalfa(Medicago sativa L.)was selected to test the influence of AM fungi on the bioremediation to the heavy metals Cu/Zn absorption and distribution strategies.This study included three experiments:1)assess the influence of the AM fungal(Glomus versiforme)symbiosis on the acquisition and distribution of Cu in alfalfa.2)assess the influence of the G.versiforme symbiosis on the acquisition and distribution of Zn in alfalfa.3)assess the influence of the G.versiforme symbiosis on the acquisition and distribution of Zn and Cu in alfalfa.The results are listed as follows:1)Inoculation G.versiforme could improved the two varieties of alfalfa growth under the condition of Cu,Zn,Cu/Zn composite pollution,such as improved plant height,branch level,ground diameter,biomass and other growth indexes.Thus AM fungi could enhanced the tolerance of alfalfa to heavy metal stress.In different treatments,the shoot biomass increased significantly while the mowing frequency increased.Thus,the suitable mowing intensity and mowing frequency could enhanced the bioremediation efficiency of M.sativa to heavy metal contaminated soil.2)In Cu,Zn,Cu/Zn composite pollution condition,Fe,Mg,Mn,P and other mineral nutrition content in inoculated G versiforme of the two varieties of alfalfa were significantly increased.AM fungi could improved the mineral nutrition status of alfalfa,and indirectly to increase its tolerance to heavy metal stress,and improved the growth condition of plants in heavy metal polluted soils.3)Inoculation G versiforme could influenced alfalfa biomass,thus improved the Cu and Zn content in per plant.Mowing treatment significantly increased the shoot of Cu and Zn accumulation,and improved the efficiency of heavy metal pollution soil bioremediation.4)In Cu treatment,inoculation with G.versiforme,the change efficiency of absorption ability to Cu of the variety of alfalfa Empress were reached 300%and Algonquin reached 450%.In Zn treatment,inoculation with G versiforme,the change efficiency of absorption ability to Zn of the variety of alfalfa Empress increased 290%and Algonquin reached 140%.In Cu/Zn composite pollution condition,inoculation with G.versiforme,the change efficiency of absorption ability to Zn of the variety of alfalfa Empress reached 903%,and the absorption ability to Cu reached 684%.In a word,inoculated with AM fungi could improved the absorption ability of alfalfa to bioremediate Cu and Zn in polluted soils.