| With the development of modern industry,heavy metals inevitably enter the environment,and their pollution of soil and water bodies is becoming increasingly serious,among which,arsenic(As)and antimony(Sb)are concerned because of high toxicity and extensiveness.Microbial combined super-enrichment phytoremediation of arsenic-antimony contaminated soils has become a research hotspot for the treatment of arsenic-antimony contaminated soils because of low-cost and environment-friendly.In this study,we firstly isolated and screened strains that could also oxidize arsenic-antimony from field contaminated soil,determined their maximum tolerance concentration to arsenic-antimony and optimal growth conditions,further investigated the promoting effect of the strains,and finally applied the strains to the rhizosphere of Pteris vittate L.by potting test.The biomass,arsenic-antimony content of each part,arsenic-antimony content in rhizosphere and bulk soil,and antioxidant enzyme activity in the leaves of Pteris vittate L.were measured after 70 d of incubation.The aims were:(1)obtain efficient arsenic-antimony oxidizing bacteria to continuously enrich the species of arsenic-antimony oxidizing bacteria;(2)investigate the effect of arsenic-antimony oxidizing bacteria on the uptake of arsenic-antimony by Pteris vittate L.,and to provide a theoretical basis for the joint microbial-plant remediation of arsenic-antimony pollution.The main results were as follows:(1)Five strains of arsenic-antimony oxidizing bacteria were isolated and selected from field contaminated soil and identified by 16 S r RNA.The five strains of arsenic-antimony oxidizing bacteria belonged to four genera,named Agrobacterium sp.C1,Azospirillum sp.C2,Ensifer sp.C7,Achromobacter sp.C18,Ensifer sp.C22,respectively,among which,Azospirillum sp.C2,Ensifer sp.C7,Achromobacter sp.C18,Ensifer sp.C22 were the first reported strains with arsenic-antimony oxidizing ability.(2)Achromobacter sp.C18,a strain with high tolerance to arsenic and antimony,was investigated for its optimal growth conditions and growth promotion characteristics.The results showed that Achromobacter sp.C18 could grow in a wide range of conditions,at p H5~9,at 25~45°C,and in a salinity range of 0~5%.At the same time,Achromobacter sp.C18 had the ability to produce indole acetic acid and iron carriers,with indole acetic acid yield of2.14 mg L-1,but without the ability to dissolve phosphorus.(3)We selected contaminated soils in the field of Lengshuijiang River and used pot experiments to study the effects of Achromobacter sp.C18 on the growth and arsenicantimony enrichment of Pteris vittate L..The results showed that Achromobacter sp.C18 significantly promoted the plant height of Pteris vittate L.in soils contaminated with high arsenic-antimony.The addition of Achromobacter sp.C18 significantly promoted the uptake of arsenic-antimony by Pteris vittate L.in soils with different contamination levels.The contents of arsenic-antimony in all parts of Pteris vittate L.increased with soil contamination concentration.The arsenic content of Pteris vittate L.leaves increased by 14.5%~23.9%,and the antimony content increased by 29.9%~178.7%.The arsenic content in stems increased by11.5%~34.0%,and the antimony content increased by 31.9%~84.4%.The arsenic content in roots increased by 16.8%~138.2%,and the antimony content increased by 18.5%~25.0%.The arsenic-antimony content in the soil was also reduced accordingly,mainly reflected in the significant reduction of arsenic-antimony in the rhizosphere soil.The arsenic-antimony oxidizing bacteria helped enrich more arsenic in the upper part of Pteris vittate L.,and the enrichment and transport coefficients increased compared with the control,meanwhile it could enhance the transport capacity of Sb in Pteris vittate L.to increase transport coefficient.The addition of arsenic-antimony oxidizing bacteria increased the POD,CAT,and SOD activities in the leaves of Pteris vittate L.,but with the increase of contamination,high concentration of arsenic-antimony contamination had an inhibitory effect on POD activity.In conclusion,an arsenic-antimony oxidizing strain was obtained in this study,which has application value in the remediation of arsenic-antimony contaminated soil.On the one hand,it can promote the growth of Pteris vittate L.,and on the other hand,it can affect the uptake efficiency of arsenic-antimony by Pteris vittate L..Therefore,this study provides a theoretical basis for the remediation of arsenic-antimony contaminated soil by microorganisms combined with super-enriched plants. |
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