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The co-occurrence of toxic vanadium (V) and chromium (VI) in groundwater receives incremental attention while knowledge on their interactions in biogeochemical processes is limited, with lack of efficient removal means. This study is the first to realize synchronous bio-reductions of V(V) and Cr(VI) with high efficiency by mixed anaerobic culture. After 72-h operation, 97.0 ± 1.0% of V(V) and 99.1 ± 0.7% of Cr(VI) were removed, respectively, with initial concentration of 1 mM for both V(V) and Cr(VI). Cr(VI) bio-reduction took priority while V(V) detoxification was inhibited. V(IV) and Cr(III) were the identified reduction products, both of which could precipitate naturally. Initial Cr(VI) and acetate concentrations as well as pH affected this process significantly. High-throughput 16S rRNA gene sequencing analysis indicated the accumulation of Anaerolineaceae , Spirochaeta and Spirochaetaceae , which could contribute to V(V) and Cr(VI) bio-reductions. The new knowledge obtained in this study will facilitate understanding the biogeochemical fate of co-existing V(V) and Cr(VI) in groundwater and development of bioremediation strategy for their induced combined pollution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Iron-based denitrification improved nitrogen removal at low C/N ratio in freshwaters. • Microbially mediated denitrification dominated rather than chemodenitrification. • Five fast-growing microbes accounted for over 99% of the community. • Amino acids and vitamins needed by an organism could be satisfied by another member. • The two-partner relationships increased community stability without limiting activity. Iron-dependent denitrification is a safe and promising technology for nitrogen removal in freshwaters. However, the understanding of microbial physiology and interactions during the process was limited. Denitrifying systems inoculated with freshwater samples were operated with and without iron(II) at a low C/N ratio for 54 days. Iron addition improved nitrogen removal. Batch experiments confirmed that microbially mediated reaction rather than abiotic reaction dominated during the process. Metagenomics recovered genomes of the five most abundant microorganisms, which accounted for over 99% of the community in every triplicate of the iron-based system. Based on codon usage bias, all of them were fast-growing organisms. The total abundance of fast-growing organisms was 38% higher in the system with iron than in the system without iron. Notably, the most abundant organism Diaphorobacter did not have enzymes for asparagine and aspartate biosynthesis, whereas Rhodanobacter could not produce serine and cobalamin. Algoriphagus and Areminomonas lost synthesis enzymes for more amino acids and vitamins. However, they could always obtain these growth-required substances from another microorganism in the community. The two-partner relationship minimized the limitation on microbial reproduction and increased community stability. Our results indicated that iron addition improved nitrogen removal by supplying electron donors, promoting microbial growth, and building up syntrophic interactions among microorganisms with timely communications. The findings provided new insights into the process, with implications for freshwater remediation. [ABSTRACT FROM AUTHOR]

Spatial distribution of vanadium in surface soils from different processing stages of vanadium-bearing titanomagnetite in Panzhihua mining and smelting area (China) as well as responses of microbial communities including bacteria and fungi to vanadium were investigated by fieldwork and laboratory incubation experiment. The vanadium contents in this region ranged from 149.3 to 4793.6 mg kg −1 , exceeding the soil background value of vanadium in China (82 mg kg −1 ) largely. High-throughput DNA sequencing results showed bacterial communities from different manufacturing locations were quite diverse, but Bacteroidetes and Proteobacteria were abundant in all samples. The contents of organic matter, available P, available S and vanadium had great influences on the structures of bacterial communities in soils. Bacterial communities converged to similar structure after long-term (240 d) cultivation with vanadium containing medium, dominating by bacteria which can tolerate or reduce toxicities of heavy metals. Fungal diversities decreased after cultivation, but Ascomycota and Ciliophora were still the most abundant phyla as in the original soil samples. Results in this study emphasize the urgency of investigating vanadium contaminations in soils and provide valuable information on how vanadium contamination influences bacterial and fungal communities. [ABSTRACT FROM AUTHOR]

Abstract: Polyaniline (PANI) films were electrochemically synthesized on graphite electrode and their ion-exchange selectivities for ClO4 − were investigated. Cyclic voltammetry (CV) results showed that PANI-H2SO4 film represented higher selectivity for ClO4 − than PANI–HCl and PANI–HClO4. Furthermore, the CV records of PANI–H2SO4 film in different acidic solutions demonstrated that ClO4 − exchange was performed in a lower potential range (from −0.025V to 0.097V), which is distinguished from SO4 2− and Cl−. Additionally, chronoamperomertry (CA) studies of PANI–H2SO4 film in 0.1M various acidic solutions (H2SO4, HCl and HClO4) confirmed that the diffusion coefficient values in HClO4 (13.319/18.184×10−6 cm2 s−1) were the biggest during doping/de-doping process. The exceptional ion-exchange selectivity for ClO4 − was explained by the process of dominant accumulation, quick insertion of anions, and the sluggish mobility of ClO4 − inside the membrane. Results of present work demonstrated that PANI may serve as a promising membrane for ClO4 − removal by ion-exchange process. [Copyright &y& Elsevier]