RESUMEN
In Hungary, the dam of a red mud reservoir breached shortly after noon on October 4, 2010. Approximately 0.7-1 million m(3) highly alkaline red mud with very low dry matter content flowed into the Torna Creek and the surrounding area, covering 1017 ha of agricultural land. Results of the risk assessment of the accident indicated that the red mud should be removed from the surface of fields where it formed a continuous layer of more than 5 cm. After the removal, samples were taken manually from depths of 0.0-0.2 m and 0.2-0.4 m in a sampling grid and background samples unaffected by red mud from the depth of 0.0-0.3 m. Total element contents (Ag, As, Ba, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Sn, Zn, and Na) and pH values were measured, and the results were analysed using correlation analysis and the Kruskal-Wallis probe. Dependence of the measured variables from elevation above sea level was studied using a 10 m by 10 m digital elevation model. Only â¼6.5% of the flooded area was temporarily designated as unsuitable for the production of food and fodder crops. In summary, the clean-up operation can be said to have been a success.
Asunto(s)
Desastres , Inundaciones , Contaminantes del Suelo/análisis , Agricultura , Monitoreo del Ambiente , Restauración y Remediación Ambiental , Hungría , Lagos , Medición de RiesgoRESUMEN
An integrated assessment of biological activity and ecotoxicity of fluvial sediments in the Marcal river catchment (3078 km(2)), western Hungary, is presented following the accidental spill of bauxite processing residue (red mud) in Ajka. Red mud contaminated sediments are characterised by elevated pH, elevated trace element concentrations (e.g. As, Co, Cr, V), high exchangeable Na, and induce an adverse effect on test species across a range of trophic levels. While background contamination of the river system is highlighted by adverse effects on some test species at sites unaffected by red mud, the most pronounced toxic effects apparent in Vibrio fischeri bioluminescence inhibition, Lemna minor bioassay and Sinapis alba root and shoot growth occur at red mud depositional hotspots in the lower Torna Creek and upper Marcal. Heterocypris incongruens bioassays show no clear patterns, although the most red mud-rich sites do exert an adverse effect. Red mud does however appear to induce an increase in the density of aerobic and facultative anaerobic bacterial communities when compared with unaffected sediments and reference sites. Given the volume of material released in the spill, it is encouraging that the signal of the red mud on aquatic biota is visible at a relatively small number of sites. Gypsum-affected samples appear to induce an adverse effect in some bioassays (Sinapis alba and Heterocypris incongruens), which may be a feature of fine grain size, limited nutrient supply and greater availability of trace contaminants in the channel reaches that are subject to intense gypsum dosing. Implications for monitoring and management of the spill are discussed.