Dariusz CISZEWSKI, Paweł BIJATA & Kazimierz KLIMEK
University of Science and Technology AGH, Mickiewicza St. 30, Kraków, Poland, ciszewski@geol.agh.edu.pl
Silesian University, Faculty of Earth Sciences, Będzińska 60, Sosnowiec, Poland, klimek@us.edu.pl

RECONSTRUCTION OF POST-MINING ATTENUATION OF HEAVY METAL POLLUTION IN SEDIMENT OF THE ZLATÝ POTOK, EASTERN SUDETY MTS

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The article presents investigations of heavy metal pollution in overbank and river bed sediments of the Zlatý Potok (Golden Brook) in Eastern Sudety Mts. northern slope and foreland. The region of former gold mining in Zlaté Hory (part of Eastern Sudetes), situated at the Czech-Polish border, was well known as one of the largest gold producers in the Czech lands since at least early medieval times. In the 20^th century production was extended to polymetallic ores. In 1965-1993 about 6.5 mln tons of Cu ores were extracted with average content of Cu of about 0.5 %. The region is drained by Zlatý Potok and its tributaries, which cross the Czech-Polish border. Estimation of the former sediment pollution and their post mining changes were attempted by analyses of heavy metals concentration in a series of 5 vertical profiles outcropped in the upper reach of this river and in 7 profiles of the meander bend in its lower reach as well as by analysis of channel bed sediments along the entire 40 km river course. Despite considerable efforts in restoration of the area of spoil heaps and a former settling pond, an increase in Zn pollution of the most recent overbank deposits in the upper reach was observed. A peak of these metals is preceded by lower lying peaks of Cu and Pb. Peaks are related to the largest extraction of Cu in 1960s and 1970s and its decline, which was accompanied by the increase in Zn production at the very end of the mine activity. High pollution of the river bed sediments in Zlatý Potok and its tributaries was identified as the main source of contemporary overbank Zn and Cd pollution in this channel reach. However, this pollution source is small considering the load of pollutants stored, because recently it has not affected lower channel reaches, where peaks of Cu, Zn and Cd decrease simultaneously toward the surface in most of the vertical profiles investigated there. This effect is confirmed by generally low pollution level of the channel bed sediments along the entire middle and lower reach of the Zlatý Potok.