Preliminary evaluation
A second pollution in the river Tisza was caused by the bursting of the dam of a sedimentation pond of the Romanian "Remin", a state owned mining company near Baia Borsa. As a result of this almost 20 000 tons of sludge/sediment containing heavy metals was spilled into the Vaser stream and along the river Viseu into the Tisza.
The catastrophe was caused by a heavy rainfall and melting of snow as well as because the dam of the tailings did not meet the technical requirements.
The Romanian party sent its formal message on the pollution incident via the Danube Valley Principal International Alert Centre (PIAC) to the Hungarian PIAC-05 Centre at 16.22 on 10 March 2000. According to that report the burst of the dam occurred 45 kms from the inflow of the river Viseu into the river Tisza, at 10 a.m. on 10 March.
The first Romanian measurement data were reported at 8.40 on 11 March. The measured concentration of metals and suspended solids were very high. The Romanian environmental and water authorities continuously informed the Hungarian partner authorities about the event and extent of the accident. This was also confirmed and complemented by Ukrainian information. According to the message arrived at 11.22 on 11 March the pollutant spill from the sedimentation pond was stopped, but the dam was not reconstructed at that time and the infiltration continued (based on the message received at 22.29 on 11 March).
The responsible environmental protection and water management authorities ordered water protection preparedness to minimise the detrimental effect of the pollution.
Water quality measurements during the time of the pollution transport across Hungary
An immediate sampling and measurement programme started to follow the change in the concentration and the spread of the pollutants, which lasted until the metal pollution left the Hungarian border. The sampling sites were designated in 20 sections of the Tisza and the Eastern Main Channel and more then 400 samples were taken. Sampling in the flood plains was not possible so far because of the flood; the pollutants deposited in the flood plains can be examined after passing of the flood.
Samples of the pollution plume were taken on average in every 2 hours while before and after its passing in every 4-6 hours.
To be able to follow the pollution transport the concentration of the dissolved and total lead, zinc and copper as well as the suspended solids have been measured in each sample. Furthermore, all parameters that are important from water quality point of view (pH, conductivity, COD, etc.) have also been measured in the laboratories.
Measurements have been carried out mainly in the laboratories of the environmental inspectorates, Institute for Water Pollution Control of VITUKI, University of Debrecen and the Institute of Environment Protection of the Institute for Environmental Management.
The samplings and measurements have been carried out in accordance with the requirements of the Hungarian National Standards.
Water samples were taken from the streamline near the surface by ladling technique in accordance with the requirements of the Hungarian National Standard MSZ ISO 5667-4.
Measurements of metal concentration were carried out by atomic absorbtion technique in accordance with the requirements of the Hungarian National Standards MSZ 4184-3 and MSZ 1484-3.
The compliance of the applied testing procedures and the subsequent control of the authenticity of the analytic results are presently in progress. For this purpose a mobile laboratory has been used at Tiszaf=FCred performing a continuous, 24 hour sampling (Disaster Response Team of the UN OCHA and UNEP) and analysis is under way (in Switzerland).
Detrimental effects of the pollutants
Heavy metals can have toxic effect on living organisms as a result of the bioaccumulation process. Limit values for the category of the heavily polluted surface water (category V) are as follows:
- Copper 0.100 mg/l
- Zinc 0.300 mg/l
- Lead 0.100 mg/l
Effect of the accidental pollution on the quality of the Tisza
The pollutant transport could be followed on the base of the concentration values of copper, zinc, lead and suspended solid. After the burst of the dam two more pollutant waves have been transported down the Tisza, but the data show significantly lower maximum values compared to the data of the first wave.
The pollutants reached Hungary in the afternoon of 10 March 2000 and the first pollution wave left the country at Tiszasziget (rkm 165) on 19 March.
Based on the numerous data it can be stated that the metal pollutants were rather attached to suspended solids than being in dissolved form.
The 50-70 km long pollution plume contained on the average a concentration of 1200-500 mg/l of suspended solid and concentrations of lead, copper and zinc which were above the limit values for the category of the heavily polluted surface water (category V).
The polluting suspended solid consists of minerals containing lead, copper, zinc and accompanying fine-grained detritus.
There is a close connection between the change in the quantity of the suspended solid and the concentration of metals. Downstream, in the front end of the pollution plume the concentration of the lower density zinc and copper fraction was higher while in the second part the concentration of the lead was prevailing in the suspended solid. This relation is characterised by the shifting in time of the maximum concentrations measured for the total lead, zinc and copper: the maximum concentrations of zinc and copper were followed by the maximum concentration of lead in the analysed pollution plume 4-6 hours later.
The table below shows the maximum and the average concentrations of the suspended solid and the total metal content (copper, lead and zinc):
Sampling sites | Suspended solid (mg/l) | Total metal (mg/l) | ||||||
copper | lead | zinc | ||||||
max. | average | max. | average | max. | average | max. | average | |
| Tiszabecs (744.2 rkm) | 1150 | 700-900 | 0.86 | 0.25-0.30 | 2.9 | 1.0 | 2.9 | 1.0 |
| Tokaj-Bodrog (545 rkm) | 1700 | 1100-1200 | 0.18 | 0.08-0.10 | 0.34 | 0.2-0.22 | [<br>] | [<br>] |
| Tiszalök (523.1 rkm) | 1900 | 1100-1200 | 0.16 | 0.08-0.10 | 0.34 | 0.2-0.22 | 0.74 | 0.4-0.45 |
| Szolnok (340.0 rkm) | 910 | 680-700 | 0.22 | 0.15 | 0.23 | 0.15 | 0.44 | 0.35 |
| Csongrád (247.0 rkm) | 700 | 400-450 | - | - | 0.19 | > 0.1 | 0.36 | 0.20-0.25 |
| Tiszasziget (165.0 rkm) | 560 | 400-450 | - | - | 0.046 | 0.03-0.04 | 0.26 | 0.2 |
On the basis of the data in the Table it can be stated that the measured maximum and average concentration values of copper, lead and zinc in the Tiszabecs-Tiszalök section of the river exceed (many times) the limit values set for the very polluted category in the classification system of surface waters. As a result of the advantageous backwater effect of the Lake Tisza, the concentration of the suspended solid decreased significantly (app. 30-40%). The concentration of metals also decreased, but the maximum and average concentrations measured for all analysed metals were higher than the limits set for the very polluted category.
In the Csongrád-Tiszasziget section the maximum concentration of the suspended solids was 600-700 mg/l, approximately 30% of the value measured in the upper course of the river. The measured maximum values for the total lead content were lower than 0.1 mg/l in all but one case where the maximum value exceeded the limit value (0.19 mg/l). The maximum value of the total zinc in the Csongrád section was slightly higher than the limit value, while the average was below that. (Concentrations measured for copper were not available at the time this assessment was being produced.)
In the Tiszasziget section the maximum and average values of the total zinc were below the limit value set for the very polluted category.
In the sections indicated in the Table the concentrations of dissolved metals (copper, lead, and zinc) were nearly constant. The concentration of dissolved lead exceeded the limit value only in the Tiszabecs section (0.1-0.15mg/l). The maximum values of the zinc in the Tiszabecs-Szolnok section were slightly higher than the limit value (0.35 mg/l). In the Szolnok-Tiszasziget section the concentrations of dissolved Pb and Zn were below the limits, data for copper are not available.
13 additional metals were analysed in the Tiszabecs and Vásárosnamény sections, but based on ICP assessment results none of them exceeded the limit values.
Due to the sedimentation of the suspended solid and the conscious water management activities concerning the Lake Tisza, the pollution caused no problem in the drinking water supply of the town of Szolnok.
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