Magnetic susceptibility as a proxy for investigating microbially mediated iron reduction

Farag M. Mewafy (1) , Estella A. Atekwana (1) , D. Dale Werkema Jr. (2) , Lee D. Slater (3) , Dimitrios Ntarlagiannis (3) , André Revil (4) , Magnus Skold (5) , Geoffrey N. Delin (6)

1 Boone Pickens School of Geology
2 EPA - US Environmental Protection Agency
3 Department of Earth and Environmental Science [Newark]
4 Géophysique des volcans & géothermie
5 Department of Geophysics [Golden CO]
6 USGS - United States Geological Survey [Reston]

We investigated magnetic susceptibility (MS) variations in hydrocarbon contaminated sediments. Our objective was to determine if MS can be used as an intrinsic bioremediation indicator due to the activity of iron-reducing bacteria. A contaminated and an uncontaminated core were retrieved from a site contaminated with crude oil near Bemidji, Minnesota and subsampled for MS measurements. The contaminated core revealed enriched MS zones within the hydrocarbon smear zone, which is related to iron-reduction coupled to oxidation of hydrocarbon compounds and the vadose zone, which is coincident with a zone of methane depletion suggesting aerobic or anaerobic oxidation of methane is coupled to iron-reduction. The latter has significant implications for methane cycling. We conclude that MS can serve as a proxy for intrinsic bioremediation due to the activity of iron-reducing bacteria iron-reducing bacteria and for the application of geophysics to iron cycling studies.

Keywords: bioremediation; iron reduction; magnetic susceptibility; methane cycling

Domains: Sciences of the Universe [physics]; Earth Sciences; Geomorphology

Farag M. Mewafy, Estella A. Atekwana, D. Dale Werkema Jr., Lee D. Slater, Dimitrios Ntarlagiannis, et al.. Magnetic susceptibility as a proxy for investigating microbially mediated iron reduction. Geophysical Research Letters, 2011, 38, pp.L21402. ⟨10.1029/2011GL049271⟩. ⟨insu-00681303⟩