Hungary + 3 more

Preliminary evaluation of the cyanide pollution in the rivers Szamos and Tisza


Ministry for Environment of the Republic of Hungary
Directorate for Environmental Protection
February 2000

Description of the events

The cyanide pollution of the rivers Szamos and Tisza was caused by the AURUL, an Australian-Romanian joint venture located in the area of the Romanian Baia Mare (Nagybánya). The company extracts non-ferrous metals from the waste rock piles of the mines of the area using metal enrichment technologies, which is carried out basically by extraction with cyanide after grinding the refuse ore.

The process of extraction needs a lot of water. Consequently, after storage the cyanide bearing water will be recycled into the technology. The environmental damage that spread over to Hungary was originated as the result of bursting of the dam of the tailings containing cyanide.

The first Romanian official written information on the pollution arrived to the Upper-Tisza Region Environmental Inspectorate from the Water Management Directorate of Cluj at 18.20 on 31 January 2000. According to this information the concentration of cyanide was 19.16 mg/l in the Lápos stream on 31 January 2000.

The Principal International Alert Centre-08 (PIAC) of the Danube Accident Emergency Warning System in Bucharest sent its first formal "alarm-incident" message to the Hungarian PIAC-05 centre at 20.55 on 31 January.

According to this official information the exceptional event took place at 10 p.m. on 30 January 2000, as a consequence of which almost 100 thousand m3 waste water with high concentration of cyanide was spilled into the Zazar and Lápos water courses that belong to the catchment area of river Szamos.

The renovation of the tailings dam took place on 31 January 2000, so the wastewater discharge into to the watercourses was halted.

The Romanian environmental and water authorities continuously informed the Hungarian authorities about the event and the degree of pollution.

The competent environmental protection and water management authorities ordered exceptional high level preparedness to minimise the detrimental effect of the pollution.

Water quality measurements during the time of the passing of the pollution

In order to measure the concentration and follow the transport of the pollutants, after ordering the exceptional emergency situation, a sampling and assessment programme started immediately focusing on the complete duration of the transport of the toxic pollution through Hungary. Using the results of the programme, the data and forecasts on the rate of water flows the passing of the pollutant could be followed from the border section of the incoming river Szamos down to the border section of the river Tisza at the Southern border.

From 12 a.m. on 1 February 2000 to 12 a.m. on 12 February more than 500 samples were taken from about 30 sampling sites from the polluted water body of the river Szamos, river Tisza, Eastern Main Canal and Western Main Canal, on average in every 2 hours. Beyond these, water from wells close to the water body were also contolled.

In order to trace the passing of the pollution the cyanide content of each sample - depending on the nature of pollution - was measured. The regional laboratories, however, beyond measuring the concentration of cyanide, also measured other important water quality parameters, such as metals from inorganic micropollutants accompanying the pollution. Furthermore, supplementary chemical, physical and hydrobiological tests have already been started during the time of the travel of the polluted section to provide more accurate information on the nature, degree and effect of the pollution. These tests and the evaluation of their results are still in progress.

The most measurements have been carried out by the laboratories of the competent regional Environment Protection Inspectorates and Water Management Directorates, the National Public Health and Medical Officers' Service, as well as the laboratories of the waterworks.

Sampling and measurements of water quality parameters have been conducted by the above laboratories in accordance with the applicable Hungarian and international standards.

With the exception of the frozen upper Tisza section, all samples were taken from the streamline of the river, by sampling close to the surface of the river, in compliance with the requirements of the MSZ (Hungarian Standard) ISO 5667-4 Standard.

Total concentration of cyanide has been measured in accordance with the requirements of the Hungarian Standard MSZ 260-30 (distillation followed by colorimetric determination). This method is substantially identical with the procedure described in the international standard ISO 6703.

The dissolved metal content was determined by applying atomic absorption procedure as defined in the Standard MSZ 1483-3, and that also meets the requirements of the appropriate international testing procedures.

The laboratories involved in the measurements have a status of being accredited nationally and take part in inter-calibration tests on a regular basis.

The compliance of the applied testing procedures and the subsequent control of the authenticity of the analytic results are presently in progress with the involvement of an international (Dutch) expert.

Damaging effect of the pollutant

The pollution consists mainly of metal complexes of cyanide. Preliminary measurements detected in addition to cyanide a significant amount of copper and zinc. These metal complexes of cyanide are easily soluble in water, while their decomposition or the degradation of the cyanide is limited.

Considering that both cyanide and metal complexes of cyanide cause direct acute toxicity in living organisms getting in contact with them, it is important to have thorough knowledge of the toxic effects of these substances on certain groups of living organisms and on their habitats. It also helps to determine the degree of damage in different groups of living organisms.

The toxic effect of the lowest concentrations of cyanides can be detected in the case of fishes, zooplanktons and benthic organisms. The toxic effect on the phytoplanktons (algae) is caused by 4-6 times higher concentrations than in case of the fishes, while in the case of certain benthic organisms this concentration is even higher. The issue of accumulation of pollutants in the living organisms and especially in fishes should also be taken into account.

Beyond the individuals of aquatic organisms other ecosystems having contact with the aquatic environment (birds, mammals, macro vegetation etc.) can also be damaged.

The limitation of the utilisation of the water resources depends on the level of pollution. This is primarily the drinking water supply and other water resources utilised in the region, e.g. bored wells are important from their aspect of their usage for human or animal consumption.

In Hungary, surface water quality is classified in a five-category evaluation system. With respect to cyanide concentration, any water containing cyanide with a concentration value exceeding 0.100 mg/l is classified as heavily polluted (category V). The maximum limit value permitted by the Hungarian standard on drinking water is also maximum 0.100 mg/l. In most cases the limit values of the European Union are more stringent than the Hungarian ones. Directive 75/440/EEC prohibits the water abstraction from surface water for drinking water supply above cyanide concentration of 0.05 mg/l. According to the directive 98/83/EEC the limit value of cyanide concentration of potable water is 0.05 mg/l.

Heavy metals have a toxic effect on living organisms primarily as a result of the bioaccumulation process. The category of heavily polluted water (category V) in the classification system of surface waters, contains the limit value 0.100 mg/l for copper and 0.300 mg/l for zinc. The degree of accumulation of heavy metals in the sediment can only be determined by further tests.

The effect of the exceptional pollution on the water quality of Szamos-Tisza water system

The transport of the pollutants in the water system can be followed by the values of cyanide concentration. The magnitude of the pollution is well represented by the maximum total cyanide values measured in the given period:

Water course Section
River km
Total cyanide
01. 02. -20.30 Szamos at Csenger
05. 02. - 08.00 Tisza at Balsa
07. 02. - 16.00 Tisza at Tiszafüred
08. 02. - 06.00 Tisza at Kisköre
09. 02. - 04.00 Tisza at Szolnok
10. 02. - 12.00 Tisza at Csongrád
11. 02. - 12.00 Tisza at Szeged
11. 02. - 12.00 Tisza at Tiszasziget

The maximum values measured in the river Szamos were 300 times higher than the limit value of the "heavily polluted water " category (category V), 100 times higher in the upper section of the river Tisza, and 20-30 times higher in the lower section of the river Tisza.

The polluted water body crossed the Hungarian border at Csenger around 4 p.m. on 1 February. The highest concentration here was 32.6 mg/l and the average concentration during the six hours' travel time was 18 mg/l, based on the measurements of the Hungarian environmental laboratories.

The critical state of the water quality was aggravated by the current meteorological situation (ice on the rivers, low flow rate) because no rapid dilution of the water body occurred. The length of the polluted water section was over 30-35 km.

The polluted water body reached the river Tisza at 4 a.m. on 3 February, where the concentration of cyanide decreased to 12.4 mg/l peak value as a result of natural dilution.

The polluted water arrived to Szolnok, one of the potentially threatened cities, where drinking water is directly abstracted from the river and then treated, at 6 p.m. on 8 February and the highest concentration during the flowing-through was 2.85 mg/l.

The complete flow through Hungary lasted basically 12 days and left the country border only in the early morning on 12 February polluting the Tisza and the Danube in Yugoslavia.

In certain examined sections of rivers Szamos and Tisza, in about 24-36 hours after the arrival of the polluted body, the cyanide concentration decreased to a 0.100 mg/l limit value.

In addition to cyanide pollution the concentration of dissolved heavy metals - primarily copper and zinc - in the rivers increased also significantly during the travel time of the of pollution. For example in the river Szamos, the peak value of the copper was 160 times higher than the limit value for heavily polluted water (category V.) and the concentration of zinc also exceeded the limit value set by this category. The maximum concentration of copper measured in the Tisza at Mindszent was 36 times higher than the limit value quoted above; for zinc it was 2.5 times higher. The quality of the water leaving the country at Tiszasziget did not exceed the limit values of the "tolerable" water quality of category III. This can be stated neither for copper nor for zinc (11 February).

The transport of the polluted water body through the rivers Szamos and Tisza caused devastating ecological damages the magnitude of which at present can only be estimated.

The biologists of the regional laboratories, parallel to chemical measurements conducted biological tests. Both in Szamos and Tisza the transport of the polluted water body was followed by massive death of fish. After the flowing-through of the pollution, the collection and disposal of dead fish had been started in the river Szamos and the river Tisza in accordance with the respective decrees.

Examination of the organisms serving as food for fish (macroscopic invertebrates) was carried out by the biologists of VITUKI (Water Research Institute) ascertaining the massive death of these organisms, as well. Only few living organisms could be found.

Experts of biology stated that the rate of death in terms of phyto- and zoo-plankton is almost 100% in the Szamos and the affected upper Tisza section, whereas in the lower Tisza section, due to dilution, the rate of death was smaller.

The pollution has also caused problems in securing the drinking water supplies of the city of Szolnok. The Szolnok Water Treatment Works based on surface water abstraction from river Tisza was not able to accept raw water of a cyanide concentration over 2.0 mg/l. As a consequence of this during the pollution flow abstraction of water from the Tisza was suspended on 9 February for 11 hours. (Water works representatives declared that they can provide drinking water of appropriate quality from the Tisza only at a cyanide concentration of 0.8 - 0.1 mg/l). The population was supplied with drinking water from the public artesian wells and distributed plastic bags filled with water.

The evaluation of the measurements and the further examinations are being continued.

Preliminary pollutant balance

The quantity of total dissolved cyanide affecting the Szamos-Tisza water system with significant consequences had already been estimated. The characteristic cyanide concentration data in the table below show the transport of the polluted water body in a few selected sections of the water system. The results obtained on the basis the informative material balance calculation made by using the data in the attached table can be summarised as follows:

Szamos at Csenger
45.4 river km
Tisza at Balsa
558 river km
Tisza at Kisköre
401.6 river km
Tisza at Tiszasziget
162.5 river km
point of time
1-2 February
4-6 February
7-9 February
11-12 February
flow rate (m3/s)
concentration of total dissolved cyanide (mg/l)
0.015 - 12.4
0.01 - 3.88
0.02 - 1.49
estimated cyanide quantity in tons

The effect of the pollution spreads to ecosystems more distant from the river through the food chain and different transmitters. The pollution affected several protected and strictly protected nature protection areas, like the protected area of Lake Tisza that is an important part of Hortobágy National Park and had recently become part of the World Heritage, also Ramsar site, more areas that fall under the scope of the Ramsar Convention and biosphere reserves that are parts of the MAB programme of the UNESCO.

At present no conclusion can be drawn neither regarding the damage in the rivers and in the ecological balance of their surrounding areas nor the nature and time needed for the regeneration. Conclusions can only be drawn after having the results of the environmental monitoring launched to assess the damage and to trace the impact of rehabilitation.

It can be expected that the restoration of the original state of the rivers will take years during which continuous monitoring will be required. To accomplish this, the present monitoring system must be developed into a system that monitors the state of environment and nature regularly. This activity has started with the definition of the detailed concept. At present, the details of the assessment programme are being defined. Parallel with this, the assessment of the post effects the pollution and the measurements and assessment of the change of the state of the environment are being continued.