In this study, denitrification linked to the oxidation of arsenite (As(III)) to arsenate (As(V)) was shown to be a widespread microbial activity in anaerobic sludge and sediment samples that were not previously exposed to arsenic contamination. When incubated with 0.5 mM As(III) and 10 mM NO3-, the anoxic oxidation of As(III) commenced within a few days, achieving specific activities of up to 1.24 mmol As(V) formed g-1 volatile suspended solids d-1 due to growth (doubling times of 0.74-1.4 d). The anoxic oxidation of As(III) was partially to completely inhibited by 1.5 and 5 mM As(III), respectively. Inhibition was minimized by adding As(III) adsorbed onto activated aluminum (AA). The oxidation of As(III) was shown to be linked to the complete denitrification of NO3- to N2 by demonstrating a significantly enhanced production of N2 beyond the background endogenous production as a result of adding As(III)-AA to the cultures. The N2 production corresponded closely the expected stoichiometry of the reaction, 2.5 mol As(III) mol-1 N2-N. The oxidation of As(III) linked to the use of common-occurring nitrate as an electron acceptor may be an important missing link in the biogeochemical cycling of arsenic.
ASJC Scopus subject areas
- Water Science and Technology
- Waste Management and Disposal
- Ecological Modeling