Results of the clean-up operation to reduce pollution on flooded agricultural fields after the red mud spill in Hungary

In Hungary, the dam of a red mud reservoir breached shortly after noon on October 4, 2010. Approximately 0.7–1 million m3 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 ∼6.5 % 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.