Effects Of β-cyclodextrin On Phytoremediation Of Soil Co-contaminated With Cd And BDE-209 By Amaranth Inoculated With Fungus

The primitive disposal activities such as sorting,open burning,and acid leaching,lead to elevated levels of pollutants especially heavy metals（HMs）and polybrominated diphenyl ethers（PBDEs）in soil,and posing potential human health risks because of their carcinogenicity,cytotoxicity,teratogenicity,and mutagenicity.Phytoremediation is an appealing remediation technology which mainly bases on the use of plants to take up,store,and/or degrade contaminants,with certain demonstrated advantages such as cost-effective,environmentally friendly,and in situ applicable,compared to physical and chemical remediation techniques.The plant–microbial interactions are effective in the remediation of contaminated soil,but the bioavailability of HMs and persistent organic pollutants（POPs）in soil is the critical factor in determining the efficiency of phytoremediation.Thus,a pot experiment was conducted to develop a suitable technology for the efficient removal of both Cd and BDE-209 simultaneously from co-contaminated soil by the combination of a series ofβ-CD concentration,arbuscular mycorrizal fungus or white-rot fungus,and Cd-hyperaccumulactor amaranth（Amaranthus hypochondriacus L.）.The key findings are as follows:（1）A pot experiment was conducted to investigate the effects of a series ofβ-cyclodextrin（β-CD）on phytoremediation of soil co-contaminated with Cd and BDE-209 by amaranth inoculated with arbuscular mycorrhizal fungus（AMF）–Rhizophagus intraradices.Results showed that the combination of mycorrhizal amaranth and 0.4%β-CD significantly enhanced Cd concentrations and contents in shoots,total PBDEs concentration in roots,and BDE-209 dissipation in soil.Moreover,the RI+β_0.4.4 treatment exerted the highest removal efficiency of both Cd and BDE-209.On the contrary,the xylem area,shoot Cd and BDE-209 concentrations and contents,and removal efficiency of Cd were markedly reduced in RI+β_0.8.8 and RI+β_1.2treatments,compared with single inoculation treatment.The well-organised chloroplast and well-defined root anatomical structure were also observed in the treatment of RI+β_0.4.Significant positive correlation was found between shoot biomass and chlorophyll concentrations.Shoot Cd or BDE-209 concentrations was positively correlated with xylem areas.In conclusion,mycorrhizal amaranth added with 0.4%β-CD could be used for the decontamination of soil polluted with mixture of Cd and BDE-209 due to the higher chlorophyll concentration and the larger xylem area.（2）A pot experiment was conducted to investigate the effects of a series ofβ-cyclodextrin（β-CD）concentrations on bioremediation of soil co-contaminated with Cd and BDE-209 using the combination of amaranth and the white-rot fungus Phanerochaete chrysosporium,with BDE-209 degrading ability.Results showed that white-rot fungus was beneficial to the growth of amaranth,Cd uptake and BDE-209degradation.The addition ofβ-CD further increased biomass of both shoots and roots,shoot Cd concentrations and contents,chlorophyll concentrations and soil manganese peroxidase（MnP）activities.Moreover,well-organized mesophyll cells were observed inβ-CD treatments,implying that the combination of white-rot fungus andβ-CD can alleviate the stresses of Cd and BDE-209 to mesophyll cells.The BDE-209degradation rate was positively correlated toβ-CD concentration or MnP activity in soil.Our results also revealed that RF+β_0.8.8 treatment possessed the highest removal efficiency for Cd due to its well-configured mesophyll cell and the highest shoot biomass,chlorophyll concentration,and shoot Cd concentration.Considering simultaneous removal of Cd and BDE-209 from soil,employing 0.8%β-CD to amaranth inoculated with white-rot fungus is promising for phytoremediation of soil co-contaminated with Cd and BDE-209.（3）Compared with arbuscular mycorrhizal fungus treatments,the inoculation with white-rot fungus,with or withoutβ-CD possessed higher Chl concentration,shoot biomass and well-configured mesophyll cell.In conclusion,considering simultaneous removal of Cd and BDE-209 from soil,adding 0.8%β-CD to amaranth inoculated with white-rot fungus is promising for phytoremediation of soil co-contaminated with Cd and BDE-209.