Major element geochemistry of recent sediments from the Fláje basin (Kruimagené hory–Erzgebirge, Czech Republic)

The weathering products of the granitic rocks (which are poor in base cations) and their sediments in the Fláje basin, in an environment that is strongly influenced by SO2 and NOx emissions have been studied. High deposition of SO2 and consequent acidification of the environment causes further depletion of base cations, mobilisation of Al and modification of the weathering reactions resulting in changes of the geochemical features of recent sediments. Depletion of the bottom sediments of the Fláje basin in base cations and Al and their enrichment in Si, compared to the fresh stream sediments and eluvium, suggests a mineralogical modification of the weathering product due to prolonged contact with basin water. Depletion of the non-silicate phase of the sediment in base cations which are replaced with Al on the other hand appears to be more effective in eluvium and those sediments which are exposed directly to the effect of acid deposition, i.e. which are not below water level for the major part of the year. The water of the basin appears to be the main factor influencing the composition of the recent sediments of the basin in the acidified catchment.