Simultaneous oxidation of arsenic and antimony at low and circumneutral pH, with and without microbial catalysis. Asta Andrés, María Pilar Nordstrom, Kirk McCleskey, Blaine Arsenic Antimony Iron This research was partially funded by the Project REN 2003-09590-C04-02 from the Spanish Government. MPA was financially supported by the Spanish Government with a Ph.D. fellowship. We wish to express our gratitude to Javier Sánchez-España of the Instituto Geológico y Minero de España (IGME) for providing the Iberian Pyritic Belt field samples and to Prof. Heather Jamieson, the Giant Mine staff, and the Department of Indian and Northern Affairs Canada for the opportunity to obtain microbial biofilm from the Giant Mine. We thank Patricia Acero and Kate Campbell for their constructive comments during the preparation and review of this manuscript. We are grateful to Dr. Nat Wilson and an anonymous reviewer, to Associate Editor Jenny Webster-Brown and to Executive Editor Ron Fuge for their insightful comments. Any use of trade, product, industry, or firm names is for descriptive purposes only and does not imply endorsement by the US Government. Arsenic and antimony are common mine-water pollutants and their toxicity and fate are strongly influenced by redox processes. In this study, simultaneous Fe(II), As(III), and Sb(III) oxidation experiments were conducted to obtain rates under laboratory conditions similar to those found in the field for mine waters of both low and circumneutral pH. Additional experiments were performed under abiotic sterile conditions to determine the biotic and abiotic contributions to the oxidation processes. Our results showed that under abiotic conditions in aerated Fe(III)-sulfuric acid solutions, Sb(III) oxidizes slightly faster than As(III). The oxidation rates of both elements were accelerated by increasing As(III), Sb(III), Fe(III), and chloride concentrations in the presence of light. For unfiltered circumneutral water from the Giant Mine (Yellowknife, NWT, Canada), As(III) oxidized at 15-78 µmol/L/h whereas Sb(III) oxidized at 0.03-0.05 µmol/L/h during microbial exponential growth. In contrast, As(III) and Sb(III) oxidation rates of 0.01-0.03 and 0.01-0.02 µmol/L/h, respectively, were obtained in experiments performed with acid unfiltered mine waters from the Iberian Pyritic Belt (SW Spain). These results suggest that the Fe(III) formed from microbial oxidation abiotically oxidized As(III) and Sb(III). After sterile filtration of both mine water samples, neither As(III), Sb(III), nor Fe(II) oxidation was observed. Hence, under the experimental conditions, bacteria were catalyzing arsenic and antimony oxidation in the Giant Mine waters and iron oxidation in the acid waters of the Iberian Pyrite Belt. 2026-02-18T09:03:27Z 2026-02-18T09:03:27Z 2012 journal article Published version: Asta, M.P., Nordstrom, D.K., McClesckey, R. B. (2012). Simultaneous oxidation of arsenic and antimony at low and circumneutral pH, with and without microbial catalysis. Applied Geochemistry, 27, 281-291. https://doi.org/10.1016/j.apgeochem.2011.09.002 0883-2927 1872-9134 https://hdl.handle.net/10481/111157 10.1016/j.apgeochem.2011.09.00 eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional Elsevier