SEDIMENTARY PROFILES OF FE, MN, V, CR, AS AND MO AS INDICATORS OF BENTHIC REDOX CONDITIONS IN BALDEGGERSEE

Concentration profiles of Mg, K, La, Fe, Mn, V, Cr, As and Mo were det ermined in samples from a freeze core taken at the deepest site of Bal deggersee in 1993. The special coring technique allowed an exact datin g of the sediment samples and an annual resolution of the profiles. Lo ng term changes in benthic redox conditions produce diagnostic trends in several metal profiles. Fe, As and Mn enrichments trace the onset o f anoxia at the deepest site of the lake. High values of Mo concentrat ions 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 t o large seasonal variations of deep-water oxygen concentrations.