The paper analyses dependence of water quality parameters on flow rates at several sites in the Vltava River catchment in the Czech Republic. The presented results indicate that at the monitored sites, concentrations of nitrates, suspended solids and dissolved oxygen are in direct relation to flow rate. Temperature has an inverse relationship to flow rate. Other parameters show various relationships to flow rate at individual monitored sites or do not show any statistically significant relations.
A significant amount of artificial radionuclides has been introduced into the environment in the last century during atmospheric nuclear weapons tests and the Chernobyl accident. In this study, we investigated the temporal changes of concentrations and amounts of these radionuclides ( 90 Sr and 137 Cs) in surface water and river bed sediments. In order to evaluate the artificial radionuclide contamination diminution, we used and compared two different approaches: using a kinetic equation of the first order and, if needed, dividing the monitored period into two intervals, and in addition expressing the whole process in one equation with a series of exponential functions. Effective ecological halflives were estimated as rates of decrease. In most cases, the ecological processes were proven to affect the radionuclide removal from the hydrosphere besides their radioactive decay. Furthermore, based on the assessment made, the 90 Sr and 137 Cs data were extrapolated and the radionuclide concentrations, which occurred in the hydrosphere after the fallout deposition in 1986, were estimated.
The concentrations of natural radionuclides, radium-226, radium-228, and potassium-40, and the artificial radionuclide caesium-137, in river bottom sediments and suspended matter were monitored in the Czech Republic by the Czech Hydrometeorological Institute during the period 2000-2010 and 2001-2010 respectively. The data were used to evaluate the natural background levels of these radionuclides and the impact of human activities on the water environment. For potassium-40 in sediments, the natural background level was estimated to be 570 Bq/kg. To evaluate the background level for radium-226, the river sites affected by human activities (mining and processing uranium ore, coal) were eliminated from the assessment. The average natural background values were 47.8 Bq/kg for radium-226 and 47.2 Bq/kg for radium-228 in sediments and 86.5 Bq/kg for radium-226 and 87.9 Bq/kg for radium-228 in suspended matter. The river sediments were identified as good indicators of radioactive contamination, especially radium-226, which recorded historic contamination due to former uranium mining and milling. The radium-226 contamination rate was assessed using the ratio of radium-226 to radium-228. This ratio was used to classify sediment according to the relative contamination from the uranium industry. The residual contamination of caesium-137 due to the Chernobyl accident in 1986 was also assessed. Average values of caesium-137 were 14.0 Bq/kg in sediments and 25.0 Bq/kg in suspended matter.
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