Trace and rare earth element dispersal downstream of the Ajka red mud spill, Hungary

Between 600,000—700,000m³ of caustic (pH>13) red mud suspension were released from the Ajkai Timfoldgyar Zrt alumina plant on the 4th October 2010. This study highlights the dispersal of key red mudderived contaminants in downstream fluvial sediments from surveys undertaken within two months of the spill. Source samples contain abundant V (>1000mg/kg), Cr (>800mg/kg), Ni (>250mg/kg) and As (>80mg/kg). Red mud-affected samples are also particularly enriched above reference sites in rare earth elements which include Ce (>400mg/kg), La, Nd and Pr (all >100mg/kg). The combined signal of these provides a useful tracer of red mud dispersion in the 3076km² Marcal catchment. A comparison of the bulk physico-chemical properties of the spill material at Ajka is made with other notable tailings failures elsewhere. The implications for system management and recovery along with the effects of emergency management (e.g. gypsum dosing) on metal availability downstream of the site are also discussed.