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Title (Primary) Effect of fluctuating oxygen concentration on iron oxidation at the pelagic ferrocline of a meromictic lake
Author Bravidor, J.; Kreling, J.; Lorke, A.; Koschorreck, M.;
Journal Environmental Chemistry
Year 2015
Department SEEFO;
Volume 12
Issue 6
Language englisch;
POF III (all) T32;
Keywords ferrous iron; ferrous oxidation; oxycline; pelagic water
UFZ wide themes RU2;
Abstract In stratified iron-rich lakes, the interface between oxic and anoxic water bodies, the oxycline, is accompanied by a steep gradient of dissolved iron, the ferrocline. It is a hotspot of biogeochemical transformations, namely the cycling of iron (Fe). The rate of iron oxidation, both chemical and microbial, depends on pH, iron and oxygen concentration, and microbial activity. We investigated the ferrocline of the meromictic Lake Waldsee to find out how the ferrocline is influenced by fluctuating oxygen concentrations. We measured diurnal fluctuations of Fe2+, O2 and pH along vertical profiles during two campaigns in July and September 2011 as well as rates of iron oxidation in laboratory incubations. The oxygen content of the water column varied both between the campaigns and diurnally. We observed a diurnal intrusion of O2 into the ferrocline. The diurnal signal was visible in the iron profile in July but not in September. Iron oxidation rates determined in the laboratory demonstrate the importance of microbial iron reduction and the strong pH dependency. We related the reaction timescales for iron oxidation to the characteristic timescale of oxygen fluctuations by calculating non-dimensional numbers. This analysis showed that an oxygenation event had to last at least 10 h in order to affect the depth and vertical extent of the ferrocline, which was the case in July but not in September. Our results show that the duration of events can be an important parameter regulating biogeochemical interactions in pelagic redoxclines.
ID 16205
Persistent UFZ Identifier http://www.ufz.de/index.php?en=20939&ufzPublicationIdentifier=16205
Bravidor, J., Kreling, J., Lorke, A., Koschorreck, M. (2015):
Effect of fluctuating oxygen concentration on iron oxidation at the pelagic ferrocline of a meromictic lake
Environ. Chem. 12 (6), 723 - 730