Piotr Szwarczewski

The study area is located in the gorge section of the Upper Vistula river valley between Tyniec and Piekary near Kraków, where natural and industrial overbank alluvia with a different radionuclide activity, heavy metals content and grain size composition occur. Overbank deposits cover three levels of the floodplain where three cores of deposits were  collected. Alluvia of the lowest level along the channel are more heterogeneous and coarser than those on the middle and the highest level. Most of the overbank deposits were accumulated in the lower regime of water flow. On the basis of luminescence dating it was determined that the accumulation of overbank deposits on the first level started  200 years ago and on the highest level – 3,000 years ago.
All the three alluvium cores investigated in this study show a similar and regular vertical pattern of 137Cs and 210Pb activity. The vertical distribution of 137Cs in the profiles reflects its postdepositional migration and soil mixing due to ploughing. At the same time the vertical distribution of 210Pb seems not to be disturbed by this process. Moreover,  he peaks of 137Cs are concomitant with a decrease in heavy metal concentration in the top part of all profiles. This reflects the diminishing of industrial activity in Poland after the early 80’s of the 20th century. The vertical profile of 210Pb activity in the two cores from the upper levels of the floodplain wasused for the estimation of accumulation rates which occur to be approximately 0.4 cm/year. The vertical differentiation of heavy metals concentration in these profiles reflects both the economic changes in this region over the last century as well as the fluvial activity of the Vistula river. The higher pollution in the upper parts of the two profiles can be correlated with the industrial period which began at the end of the 19th century and lasted up to the middle of the 20th century in the upper Vistula river basin (Silesian Upland and Kraków Upland). The decrease of pollution at the top of all the profiles have results from economic recession and pro-ecological activities since the 1990’s.