Selective photocatalytic reduction of selenate over TiO2 in the presence of nitrate and sulfate in mine-impacted water.

Selenium contamination is a critical global issue across numerous industries. Industrial waters such as mine-impacted water (MIW) can contain toxic levels of selenate, in addition to varying concentrations of many different dissolved species from the underlying strata, such as sulfate, carbonate, nitrate, organic matter, and many dissolved metals. The removal of selenate from MIW is desired, due to selenate's acute and chronic toxicity in aquatic ecosystems at elevated concentrations. However, due to the complexity of the water matrix and the presence of many other dissolved constituents, this is often very challenging. In this study, we present for the first time the reduction of selenate in a real industrial wastewater, namely MIW, and reveal a significant advantage of photocatalytic reduction; the ability to selectively reduce selenate from >500 µg L-1 to <2 µg L-1 in the presence of the more energetically favourable electron acceptor, nitrate (250× molar concentration of selenate) and high concentrations of sulfate (1,940× molar concentration of selenate). The presence and impacts of sulfate, chloride, carbonate, and nitrate on the competitive adsorption and reduction of selenate on TiO2 are thoroughly investigated for the first time, using formic acid as an electron hole scavenger. The electron transfer mechanism proposed follows TiO2 conduction band electrons are responsible for the reduction of selenate to elemental Se (Se0) and both carbon dioxide radicals (CO2·-) and Se conduction band electrons are responsible for the further reduction of Se0 to hydrogen selenide (H2Se).

A comparison of whole-genome shotgun-derived mouse chromosome 16 and the human genome.

The high degree of similarity between the mouse and human genomes is demonstrated through analysis of the sequence of mouse chromosome 16 (Mmu 16), which was obtained as part of a whole-genome shotgun assembly of the mouse genome. The mouse genome is about 10% smaller than the human genome, owing to a lower repetitive DNA content. Comparison of the structure and protein-coding potential of Mmu 16 with that of the homologous segments of the human genome identifies regions of conserved synteny with human chromosomes (Hsa) 3, 8, 12, 16, 21, and 22. Gene content and order are highly conserved between Mmu 16 and the syntenic blocks of the human genome. Of the 731 predicted genes on Mmu 16, 509 align with orthologs on the corresponding portions of the human genome, 44 are likely paralogous to these genes, and 164 genes have homologs elsewhere in the human genome; there are 14 genes for which we could find no human counterpart.