On 4th October 2010, a levee breach of the sludge reservoir of the Hungarian MAL Aluminium Co. Ltd. occurred in the west of Hungary, around 100 km from Budapest in the surrounding area of Ajka town. A large amount of industrial red sludge spill occurred and caused the loss and injury of human life and extreme environmental damage.
Red mud is a by-product of the bauxite refining process, and this highly alkaline product, deposited in the reservoir, entered into the Torna creek through which it got into the Marcal River – the two streams where the most severe environmental damages were caused. The pollution plume was then spilled further on to the Rába River proceeding towards the Mosoni-Danube and then entering the Danube.
The Accident Emergency Warning System (AEWS) of the International Commission for the Protection of the Danube River (ICPDR) was triggered in the morning of 5th October and downstream countries were notified about the accident.
There are two major threats stemming from the spill of the red mud into the environment – the acute effect of the elevated pH and acute and/or chronic effects by heavy metals.
pH values and mitigation measures
The mitigation measures taken by the Hungarian authorities helped to neutralize the hydroxides so that the initial pH of 12 in the Torna creek dropped to 8 -8.3 as it was reported as of 15th October.
According to the observations of the members of the Environmental Protection Security Force on 12 October the flow of dead fish in the Danube bend, originating from the polluted section on the river Marcal, had for the most part ceased, and the behavior of the local fish population had normalized. According to the Directive 2006/44/EC on the quality of fresh waters requiring protection or improvement in order to support fish life, the allowed value of pH ranges between 6 to 9.
First indication of extent of heavy metals
The content of heavy metals in the red sludge is posing an relatively low acute toxic risk as their concentrations are rather low. However, the chronic toxicity risk for the aquatic ecosystem is high, as the heavy metals can - under specific circumstances - be remobilized into the water, and thus affect flora and fauna. As a mitigation measure, Hungary has built under-water wears in the Marcal River to settle down the suspended solids which are possibly contaminated by heavy metals.
The exact assessment of possible future impacts has to be preceded by a thorough monitoring of the heavy metal content in water, suspended particulate matter and bottom sediments in the Marcal, Raba, Mosoni-Danube and the Danube rivers.
The total concentrations of mercuy and aliminium in the Hungarian Danube at Gönyu, one of the measured sites, is continously decreasing, but still is exceeding the limit values according to the specific regulations and directives of the European Union.
According to the latest results provided by the downstream countries the threshold values for the assessed substances, including several heavy metals, are not exceeded. The dilution of heavy metals downstream the Danube are resulting in a further decrease of their concentrations so that in the Romanian Danube at Bazias (km 1071), the concentrations of mercury and aluminium have been reported below the limit values until now. The Croatian Danube is still free from the toxic sludge that has devastated parts of Hungary, as the latest sample analysis near Batina (Osijek-Baranja County) has confirmed. The director of Croatian Waters (Hrvatske Vode) Zoran Djurkovic said on 10th October, that the quantity of metals measured in the river "does not exceed the maximum limits allowed for even drinking water."
In order to have a clear picture on the threats to human life and environment deriving from the heavy metal concentrations, more details are currently under assessment - based on the ongoing measurements.
The floating dust concentration translates into increased irritation proportionate with the level of drying, but as of 15th October the medical threshold has not been reached in the contaminated areas.
Disaster relief efforts on agricultural land have begun
Disaster relief efforts on agricultural land have begun, soil analysis is ongoing. According to the measurements of the Research Institute for Soil Science and Agricultural Chemistry of the Hungarian Academy of Sciences, the contamination did not permeate the soil at a depth in excess of 10 cm and the quantity of heavy metals in this layer also did not exceed the contamination threshold.