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Mobilisation of arsenic from bauxite residue (red mud) affected soils: Effect of pH and redox conditions

DOI: 10.1016/j.apgeochem.2014.10.009 DOI Help

Authors: Cindy Lockwood (School of Earth and Environment, University of Leeds, U.K.) , Roger Mortimer (School of Earth and Environment, University of Leeds, U.K.) , Douglas Stewart (School of Civil Engineering, University of Leeds, UK) , Will Mayes (Centre for Environmental and Marine Sciences) , Caroline Peacock (School of Earth and Environment, University of Leeds, U.K.) , David Polya (School of Earth, Atmospheric and Environmental Science and Williamson Research Centre for Molecular Environmental Science, University of Manchester, U.K.) , Paul R. Lythgoe (School of Earth, Atmospheric and Environmental Science and Williamson Research Centre for Molecular Environmental Science, University of Manchester, U.K.) , Alizée P. Lehoux (School of Earth and Environment, University of Leeds, U.K.) , Katalin Gruiz (Department of Applied Biotechnology and Food Science, Budapest University of Technology and Economics, Hungary) , Ian T. Burke (School of Earth and Environment, University of Leeds, U.K.)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Applied Geochemistry , VOL 51 , PAGES 268–277

State: Published (Approved)
Published: October 2014
Diamond Proposal Number(s): 7525

Open Access Open Access

Abstract: The tailings dam breach at the Ajka alumina plant, western Hungary in 2010 introduced about1 million m3 of red mud suspension into the surrounding area. Red mud (fine fraction bauxite residue) has a characteristically alkaline pH and contains several potentially toxic elements, including arsenic. Aerobic and anaerobic batch experiments were prepared using soils from near Ajka in order to investigate the effects of red mud addition on soil biogeochemistry and arsenic mobility in soil-water experiments representative of land affected by the red mud spill. XAS analysis showed that As was present in the red mud as As(V) in the form of arsenate. The remobilisation of red mud associated arsenate was highly pH dependant and the addition of phosphate to red mud suspensions greatly enhanced As release to solution. In aerobic batch experiments, where red mud was mixed with soils, As release to solution was highly dependent on pH. Carbonation of these alkaline solutions by dissolution of atmospheric CO2 reduced pH, which resulted in a decrease of aqueous As concentrations over time. However, this did not result in complete removal of aqueous As in any of the experiments. Carbonation did not occur in anaerobic experiments and pH remained high. Aqueous As concentrations initially increased in all the anaerobic red mud amended experiments, and then remained relatively constant as the systems became more reducing, both XANES and HPLC-ICP-MS showed that no As reduction processes occurred and that only As(V) species were present. These experiments show that there is the potential for increased As mobility in soil-water systems affected by red mud addition under both aerobic and anaerobic conditions.

Subject Areas: Environment, Chemistry, Earth Science


Instruments: I18-Microfocus Spectroscopy

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