Dispersal and Attenuation of Trace Contaminants Downstream of the Ajka Bauxite Residue (Red Mud) Depository Failure, Hungary

Abstract

This paper identifies the spatial extent of bauxite processing residue (red mud)-derived contaminants and modes of transport within the Marcal and Rába river systems after the dike failure at Ajka, western Hungary. The geochemical signature of the red mud is apparent throughout the 3076 km² Marcal system principally with elevated Al, V, As, and Mo. Elevated concentrations of Cr, Ga, and Ni are also observed within 2 km of the source areas in aqueous and particulate phases where hyperalkalinity (pH < 13.1) is apparent. Although the concentrations of some trace elements exceed aquatic life standards in waters (e.g., V, As) and fluvial sediments (As, Cr, Ni, V), the spatial extent of these is limited to the Torna Creek and part of the upper Marcal. Source samples show a bimodal particle size distribution (peaks at 0.7 and 1.3 μm) which lends the material to ready fluvial transport. Where elevated concentrations are found in fluvial sediments, sequential extraction suggests the bulk of the As, Cr, Ni, and V are associated with residual (aqua-regia/HF digest) phases and unlikely to be mobile in the environment. However, at some depositional hotspots, association of As, Cr, and V with weak acid-extractable phases is observed.

Red mud a byproduct of aluminum production contains soluble vanadium that causes genotoxic and cytotoxic effects in higher plants

“…The chemical composition of the control sample (S1) is consistent with unaffected 246 soils found in the region (see Table 2c) (Mayes et al, 2011b).…”

Gypsum addition to soils contaminated by red mud: implications for aluminium, arsenic, molybdenum and vanadium solubility

“…The waste inundated homes and land downstream causing 10 deaths and over 150 serious injuries. Approximately 40 km 2 of agricultural and urban land was affected and the red mud was transported over 120 km downstream (Mayes et al 2011;Reeves et al 2011). This was the largest recorded environmental release of red mud and, as such, studies on the after-effects of the spill have both improved the knowledge-base on risks associated with red mud ) and informed broader management strategies for stockpiled red mud.…”

“…This was the largest recorded environmental release of red mud and, as such, studies on the after-effects of the spill have both improved the knowledge-base on risks associated with red mud ) and informed broader management strategies for stockpiled red mud. At Ajka, Hungary, red mud samples contained elevated concentrations of potentially toxic trace elements such as Al (75000 mg kg ) and V (900 mg kg -1 ) (Mayes et al 2011;Ruyters et al 2011). Red mud leachates are also hyperalkaline (pH 13), and can be directly toxic to aquatic life (Wilkie and Wood 1996).…”

“…Acid dosing and gypsum addition to rivers were both effective in lowering pH values and metal(loid) concentrations in river waters downstream of the spill Mayes et al 2011;Renforth et al 2012). Lack of Ca 2+ in red mud leachate (Renforth et al 2012) limits the natural pH reduction mechanism (Equations 1 and 2).…”

Biogeochemical Reduction Processes in a Hyper-Alkaline Leachate Affected Soil Profile

“…Some are entirely natural, e.g., soda lakes, hot springs, oceanographic cold seeps, deep mine waters (Takai et al 2001;Takai et al 2005;Pollock et al 2007;McMillan et al 2009;Brazelton et al 2010), but many are also due to human activities. These anthropogenic sites occur as a result of the presence of residues from a range of industrial processes, e.g., lime production waste, steelworks slags, coal combustion residues, Solvay process waste, chromite ore processing residues, bauxite processing wastes, borax wastes and cementitious construction wastes (Effler et al 1991;Carlson and Adriano 1993;Townsend et al 1999;Deakin et al 2001;Ye et al 2004;Mayes et al 2006;Mayes et al 2008;Hartland et al 2009;Mayes et al 2011). Weathering of these wastes typically produces highly alkaline leachate (pH 10-13) due to the ubiquitous presence of Ca, Na and K oxides (primarily CaO) that hydrolyze in natural waters to produce soluble metal hydroxides.…”