Accumulative heavy metal patterns in the sediment and biotic compartments of the Tisza watershed.

The paper presents data on toxic heavy metals in sediments measured after two large chemical spills on the Tisza watershed area. On the basis of the results, it is concluded that significant volume, high concentration heavy metals reached the Upper Tisza and Szamos River sections. Based on the longitudinal distribution of the heavy metals in sediments, the primary sedimentation zones and concentration increase compared with reference site was determined. Results verified arrival of fresh spills of mining origin and superimposed pollution. Regarding to chronic ecotoxicological effects, degradation and bioaccumulation rates of heavy metals priority problems are associated with arsenic, lead, mercury and cadmium in the sediments of the Tisza and Szamos Rivers after the spills of Romanian origin in 2000. Results indicate that the biological availability of the various heavy metals significantly differ along the river, particularly upstream and downstream of the Tisza Lake. The recent investigation did not identify one single sample in which muscular metal concentration of pike (Esox lucius L.) exceeded the present Hungarian consumer guidelines. The investigated pike population on the Tisza River could be divided into characteristic subgroups based on muscular tissue metal concentrations (Cd, Hg, Pb, Cu and As), depending on the bioavailability of the metalloids at the different river sections. On the basis of the data evaluation, it is concluded that the present state of pollution on Tisza River indicates the potential for deterioration and need for further biomonitoring.

Ecotoxicological studies and risk assessment on the cyanide contamination in Tisza river.

As a result of the dam failure of January 30, 2000 in Rumania, water and a huge amount of sediment contaminated with cyanide and later heavy metals entered the Tisza river system. In order to determine the chronic consequences of the contamination, periphyton and sediment samples were collected from River Tisza and her tributaries over the next 2 years. After flooding periods, the sediment deposited in the foreshore was also sampled. Applying the ICP-AES analysis method, the amounts of major heavy metals in the periphyton and sediment samples were measured, and the related concentration factors were calculated. Attempts were also made to find a correlation with the toxicity data. Ecotoxicological analyses were performed on the sediment using the following test techniques: Daphnia test, static fish test, alga test (chlorophyll content measurements), seedling test (Sinapis) and Lemna test (increase in mass and measurements on the chlorophyll concentration). Examinations on the chronic effects of heavy metals deposited in the periphyton and sediment can be regarded as an important factor in assessing ecological-conservational disasters and in carrying out biomonitoring activities in the future.