Study On Migration And Transformation Of Arsenic In Aquatic Plant Mediated By EDTA

Ethylenediaminetetraacetic acid(EDTA)is widely used in detergents,textile and paper bleaching processes,food industry and medicine,and is eventually discharged into the environment.It has a strong ability to separate metal ions,and the chelate that can be formed with metal arsenic(As)has strong stability and is difficult to biodegrade.To understand the effect of EDTA on the migration and transformation of arsenic in aquatic plants will be beneficial to the rational use of aquatic plants to remediate the water environment pollution caused by arsenic mediated by EDTA.This study took the aquatic plant system polluted by arsenic as the research object,and exposeed it to 0,0.5,5.8,and 28 mg/L EDTA respectively and determined the total arsenic in the overlying water and the total arsenic and arsenic species in the aquatic plants,as well as chlorophyll,total protein(TP),malondialdehyde(MDA),superoxide dismutase(SOD),catalase(CAT),arsenate reductase glutathione(GSH)of Acorus calamus(emergent plants),Hydrilla verticillata(submerged plants),and Pistia stratiotes(floating plants),to explore the influence of EDTA on the migration and transformation of arsenic,biological toxicity and bioavailability and its influence mechanism.This study found that:(1)EDTA mediation could desorb the arsenic fixed in the sediment into the overlying water through chelation,and the low concentration of EDTA had the best activation effect on the arsenic in the sediment.(2)EDTA mediation could significantly enhance the arsenic accumulation and absorption capacity of aquatic plants,and medium and low concentrations of EDTA had the greater contribution to the accumulation of arsenic in aquatic plants.The order of EDTA to promote the absorption and enrichment of total arsenic by aquatic plants was: Acorus calamus >Hydrangea verticillata > Pistia stratiotes.(3)The effect of EDTA on the migration and transformation of arsenic was related to the type of plant and the time of exposure culture.EDTA significantly promoted the methylation and detoxification of As(V)into methylarsenic(MMA)and dimethylarsenic(DMA)in Hydrilla verticillata and Pistia stratiotes.Moreover,the effect of low and medium concentration of EDTA mediator on the detoxification mechanism of arsenic was significantly greater than that of high concentration of EDTA.(4)The complex formed by EDTA and As had a harmful effect on the normal biochemical reaction mechanism of plants,and plants roduced large amounts of chlorophyll,proteins,malondialdehyde,catalase,superoxide dismutase,and reduced glutathione in response to arsenic stress.