Within a short period of time two serious environmental disasters occurred in the river Tisza from February to March in 2000. First, cyanide containing dissolved and complexed copper, then heavy metal (Pb2+, Zn 2+, Cu2+) contaminated sludge were discharged into the river. As a consequence the suspended particulate material, SPM, became higher than 200 mg dm-3 (the maximum value was 1200 mg dm-3). SPM is defined as a fraction that is retained by a 0.45-0.6 micron membrane filter from water sample. The content and size distribution of SPM, was investigated in the river Tisza and in the tributary artificial channel Keleti Focsatorna (KFCS). The statistical data of the last thirty years show SPM content of 25-85 mg dm-3 at low and moderate, and up to 1000 mg/dm3 at high stream flow or floods. In the unfiltered water samples the average of peak values of diameter was 〈dmode〉(34 samples)= 24±21μm at low SPM while 〈dmode〉 (6samples)=76 ±1μm at higher SPM content. In the time of the second pollution the range of size of suspended particles was narrow, the average of the peak value was 〈dmode〉 (2 samples)=3 ±1μm in the unfiltered water samples indicating that the pollution came in size of silty clay. The analysis of heavy metal content showed that 60% of Zn2+, 75% of Cu2+ and 90% of Pb2+ ions were sorbed at moderate SPM content. Considering that the filtrate may contain suspended particles smaller than 0.6 μm the ratio of the adsorbed ions must have been even higher. The role of colloids in the adsorption was proved by analysis of the sludge from a backwater of the river done six months after the pollution incident. It turned out, that although the volume ratio of the colloidal fraction (d < 1μm) in the sludge was only 18%, this fraction held 66-85% of the heavy metals.
|Translated title of the contribution||The size of the suspended particulate material and its role in the transport of the heavy metal pollution of the river Tisza in 2000|
|Number of pages||8|
|Journal||Magyar Kemiai Folyoirat, Kemiai Kozlemenyek|
|Publication status||Published - Sep 1 2002|
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