[Folda] Friday Seminar - today 12:30 - Jessica Till: "Are iron-reducing bacteria responsible for magnetic enhancement in soils?"

[Maria H. Janebo]

Dear all,

the Friday seminar series continues today (21 April) at 12:30 in the seminar room on the 3rd floor with a presentation given by:

Jessica Till: "Are iron-reducing bacteria responsible for magnetic enhancement in soils?"

Well-drained soils in temperate climates consistently have higher magnetic susceptibility than the underlying parent materials. Research in environmental magnetism over the past 20 years has determined that these enhanced magnetic signatures are carried by nanoscale particles of pedogenic magnetic Fe-oxides and that the degree of magnetic enhancement strongly correlates with climatic factors such as precipitation. Despite the widespread use of magnetic susceptibility as a paleoclimate proxy in paleosol sequences, there is no consensus about the mechanism of pedogenic magnetite production during soil formation. Some researchers have proposed a soil magnetic enhancement pathway from biologically induced magnetite formation due to the activity of iron-reducing bacteria (IRB) in soils. To better understand the formation of secondary magnetic minerals by bioreduction, we incubated samples of lepidocrocite, goethite, ferrihydrite and loess with the dissimilatory iron-reducing bacterium Shewanella putrefaciens. Rapid iron reduction and secondary magnetite formation occurred during experiments containing lepidocrocite and ferrihydrite, however the goethite and loess experiments displayed limited overall iron reduction and no magnetite formation. Slight but distinct differences in the grain size and morphology of secondary magnetite formed from different precursors were also identified as a result of different transformation pathways. Given the conditions necessary for magnetite formation by IRB, there is currently little conclusive evidence to support a bacterially mediated pathway of soil magnetic enhancement. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 675219.



Maren & Maria




_____________________________
Maria H. Janebo
Postdoctoral Research Fellow

Nordic Volcanological Center
Institute of Earth Sciences
University of Iceland, Askja 223
Sturlugata 7, 101 Reykjavik, Iceland

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