Sedimentary profiles of Fe, Mn, V, Cr, As and Mo as indicators of benthic redox conditions in Baldeggersee |
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| Authors: | Tobias Schaller H. Christoph Moor Bernhard Wehrli |
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| Affiliation: | (1) Limnological Research Center, Swiss Federal Institute for Environmental Sciences and Technology (EAWAG) and Swiss Federal Institute of Technology (ETH), CH-6047 Kastanienbaum, Switzerland;(2) Swiss Federal Laboratories for Materials Testing and Research (EMPA), CH-8600 Dübendorf, Switzerland |
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| Abstract: | Concentration profiles of Mg, K, La, Fe, Mn, V, Cr, As and Mo were determined in samples from a freeze core taken at the deepest site of Baldeggersee in 1993. The special coring technique allowed an exact dating of the sediment samples and an annual resolution of the profiles. Long term changes in benthic redox conditions produce diagnostic trends in several metal profiles. Fe, As and Mn enrichments trace the onset of anoxia at the deepest site of the lake. High values of Mo concentrations and Cr/V ratios indicate periods of stable anoxic conditions in a meromictic hypolimnion. A comparison of oxygen time series with metal profiles between 1950 and 1990 indicates that Mn reacts sensitively to large seasonal variations of deep-water oxygen concentrations. |
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| Keywords: | Lake sediments redox indicators trace metals iron manganese |
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