Microbial reduction and migration of As/Fe mediated by electron shuttle:Differences between incorporated and adsorbed As(V)

Metal-reducing bacteria play a central and important role in the biogeochemical cycle of arsenic(As)and iron(Fe).Research on As/Fe migration from arsenic-containing iron minerals mediated by electronic shuttles is of significance to groundwater protection and human health.Further,the redox activity and bioavailability of goethite with differing occurrence and distribution of arsenic have not been studied clearly.In this study,the function of electron shuttle AQDS in Fe(III)bioreduction was determined.It was found that acidic conditions were conducive to the growth and reproduction of strain D2201,which was beneficial to the reduction of As(V)/Fe(III).The OD600nm value of the bacteria at pH 6 exceeded twice that at pH 8.Then,three types of goethite,namely pure goethite(Gt),coprecipitated As(V)-goethite(Gt-As),and adsorbed arsenic-goethite(Gt*As),were compared for microbial reduction reactivity.X-ray photoelectron spectroscopy analysis illustrated the proportion of OH-content in Gt-As was much lower than that of Gt and Gt*As,indicating Gt-As carried more surface defects and had higher bioavailability.The Fe(II)content released from AQDS-mediated bioreduction of Gt-As was two-fold higher than that of Gt and Gt*As at pH 7.In addition,pH significantly affected goethite bioreduction efficiency and arsenic migration degree.The dissolved Fe(II)concentration for Gt-As was 0.98,0.133,and 0.139 mM at pH 6,7,and 8,respectively;corresponding to dissolved As(T)content of 3.51,1.48,and 1.31μM within 9 days of culture.This study highlights the significant influence of AQDS and mineral structure on the As/Fe biochemical cycle,which will help further develop the bioremediation of arsenic-contaminated sediments.

Microcystis aeruginosa aggravated arsenic accumulation in silver carp during silver carp controlling algal bloom in arsenic-contaminated water

Silver carp mediated biological control techniques are often advocated for controlling cyanobacteria blooms in eutrophic water,which are often enriched with arsenic(As).How-ever,the transfer and fate of As during the biological control of cyanobacteria blooms by silver carp in As-rich eutrophic water remain unclear.Based on the simulated ecosystem experiment,the accumulation of As in silver carp and the transfer and fate of As in the water-algae-silver carp system during Microcystis aeruginosa blooms controlled by silver carp were investigated.Microcystis aeruginosa showed high tolerance to As(V).The accumulation of As in different tissues of silver carp was different,as follows:intestine>liver>gill>skin>muscle.After silver carp ingested As-rich Microcystis aeruginosa,As accumulation in the intestine,liver,gill,and skin of silver carp was enhanced under the action of digestion and skin contact.Compared with the system without algal,As accumulation in the intestine,liver,gill,and skin of silver carp increased by 1.1,3.3,3.3,and 9.6 times,respectively,after incubation for 30 days in the system with Microcystis aeruginosa,while the accumulation of As in the muscle was only slightly increased by 0.56 mg/kg.This work revealed the transfer and fate of As during algal control by silver carp,elucidated the accumulation mechanism of As in water-algae-silver carp system,enriched our understanding of As bioaccumulation and transformation in As-rich eutrophication water,and provided a scientific basis for as-sessing and predicting As migration and enrichment in water-algae-silver carp system.