Application Of Trichoderma Asperellum SM12-F1 And Combination With Ferrihydrite To Regulate The Growth And Arsenic Uptake Of Crop In Contaminated Soils

The over-accumulation of arsenic?As?in agricultural soils affects crop growth.Subsequently,the accumulated As can pose risk to human health via food-chain.In this study,the fungal strain of Trichoderma asperellum SM-12F1 capable of As resistance and form transformation was used as a research material.First,the effect of Trichoderma asperellum SM-12F1 on Brassica campestris L.which is sensitive to As growth on soils added exogenous As and its possible mechanisms were analyzed.Then,the growth of water spinach with hight uptake of As grown on As-contaminated soils combined addition of ferrihydrite and Trichoderma asperellum SM-12F1 and its uptake of As were assessed.Thirdly,the tentative idea of ferrihydrite-T.asperellum SM-12F1 composite was raised to explore its capacity of controlling available As was explored.The main results were shown as follow:1.The growth of Brassica campestris L.was significantly inhibited in soils spiked with As of 120mg kg^-1.Inoculation significantly decreased the As bioconcentration factor?BCF?of Brassica campestris L.and improve the growth of Brassica campestris L..Compared with As-contaminated soils without inoculation,the over-ground part biomass of Brassica campestris L.increased by 81.8%and the As uptake declined by 12.4%.Methylarsonic acid?MMA?and dimethylarsinic acid?DMA?were detected in water extraction of soil and the shoot of Brassica campestris L.tissues,which indicated that inoculation decrease soil As toxicity.The enzymes in Brassica campestris L.such as superoxide dismutase?SOD?and catalase?CAT?,and the contents of glutathione?GSH?,ascorbic acid?AsA?and malondialdehyde?MDA?,capable of reactive oxygen elimination,significantly enhanced during soil As exposure.However,inoculation lessened the activities or contents of SOD,CAT,GSH,and MDA in Brassica campestris L..2.Combined addition of ferrihydrite and T.asperellum SM-12F1 could significantly promote the growth of water spinach,decrease As uptake by water spinach and improve the biological and ecological function of soil.Compared with the control treatment,the combined addition of ferrihydrite and T.asperellum SM-12F1 significantly increased water spinach shoot and root biomass by 134%and138%,respectively,and lowered As content in shoot and root by 37%and 34%,respectively.Soil available As contents decreased by 40%.The total contants varieties of PLFAs increased markedly and gram positive?G+?,gram negative?G-?,actinobacterial,bacterial,fungal PLFAs increased by 114%,68%,276%,292%,133%,and 626%,respectively.Correspondingly,the soil enzyme activities was improved significantly.3.The composite of ferrihydrite-T.asperellum SM-12F1 could significantly increase soil available As contents 28 d after addition of the composite material.The contents of available As decreased by34.6%-56.1%after 126 d in culture compared with its start.The surface area and the pore volume decreased by 82.4%and 48.2%respectively after ferrihydrite-T.asperellum SM-12F1 composited.The result of SEM-EDS indicated that Fe disappeared and the relative amount of C and O increased observably.Based on the above evidences,it is suggested that metabolites of T.asperellum SM-12F1 or intrinsic organics covered the surface physicochemical feature,impeded As adsorption by ferrihydrite.