Leakage of sludge from the tailings pond of the aluminum smelter in Ajka, Hungary – closed
In 2010, the red sludge dam broke in Hungary. This sludge contained a large amount of contaminants, especially heavy metals, and the sludge itself had a very high pH of around 13. Applying freshly mined Leonardite managed to reduce the pH of the soil to an acceptable 7.5, and the treated soil even started to germinate crops sown within days.