| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 4698972 | Chemical Geology | 2013 | 9 Pages |
•Seasonal resolved Mn and Fe records since 1895•Mn/Fe ratio correlated with oxygen monitoring data•Semi-quantitative bottom water O2 concentration reconstructions•Geochemical and sedimentological factors reduce applicability of this proxy
Redox dynamics of manganese (Mn) were studied in the sediment of Lake Zurich using precise sediment core age models, monthly long-term oxygen (O2) monitoring data of the water column (1936–2010) and high-resolution XRF core scanning. The age models were based on bi-annual lamination and calcite precipitation cycles. If present, Mn exhibits distinct maxima, which coincide with the annual maximum deep-water O2 concentrations in spring according to the monitoring data. In contrast, the iron (Fe) signal is mainly the result of calcite dilution, as indicated by a strong negative correlation between Fe and calcium (Ca) XRF data. The Mn/Fe ratio in the core from the maximum lake depth (ZH10-15, 137 m) revealed a moderate correlation with O2 measurements in the lake bottom water confirming the successful application of the Mn/Fe ratio to semi-quantitatively reconstruct bottom water oxygenation in the lake. Mostly low ratios were observed between 1895 and the mid-1960s as a result of eutrophication. However, geochemical focusing and sedimentological factors can reduce the applicability of the Mn/Fe ratio in reconstructing O2 concentrations in the bottom water of lakes.
