Lakes Bled and Bohinj Origin, Composition, and Pollution of Recent Sediments
Fifteen grab samples and two shallow cores were studied from Lake Bled. Their carbonate contents are in the range 55—79 %. Calcite prevails but dolomite may occasionally amount up to 38 % of the carbonate compound. The non-carbonates seem mostly to be diatoms besides some quartz and traces of feldspar and clay minerals. Chemical analysis of the core sediments revealed a general increase of the heavy metals Zn, Cd and Pb in the uppermost layer. The highest content of Zn (up to 970 ppm) and Pb (up to 160 ppm) were found within nearshore grab samples thus indicating sewage input. The increased eutrophication of Lake Bled is evident. Eight grab samples and one core from Lake Bohinj are also carbonate rich sandy silts and clays with total carbonate contents ranging from 53—91 %. Calcite prevails especially in the western part of the lake. Dolomite content is, in the average, higher than in Lake Bled. The noncarbonates seem essentially similar to the Bled sediments. The core samples contain an increase of the heavy metals Zn, Cu, and Pb within the uppermost 10 cms. In addition, Fe-, Mn-, Cr-, and Ni-contents are unusually high compared to Bled.