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Electron flow in an iron-rich acidic sedimant - evidence for an acidity-driven iron cycle

Title data

Peine, Ariane ; Küsel, Kirsten ; Tritschler, Andrea ; Peiffer, Stefan:
Electron flow in an iron-rich acidic sedimant - evidence for an acidity-driven iron cycle.
In: Limnology and Oceanography. Vol. 45 (2000) Issue 5 . - pp. 1077-1087.
ISSN 1939-5590
DOI: https://doi.org/10.4319/lo.2000.45.5.1077

Abstract in another language

The anoxic sediment of an acidic (pH similar to 3) iron- and sulfate-rich lake and its pore water was studied with respect to the turnover rates of solid and dissolved iron and sulfur species. High sedimentation rates of iron (570 g m-2 a-1) lead to an enrichment of the upper (0-5 cm) acidic sediment zone (pH < 4) with schwertmannite (Fe8O8)(OH)x(SO4)y (approximate to 350 g kg-1). Microbial iron-reduction rates measured by closed vessel incubation technique were highest close to the sediment-water interface (250 nmol cm-3) d-1), sulfate reduction measured by the 35S-tracer technique was not detectable in this zone. The absence of sulfide allowed complete reoxidation of dissolved Fe(II) diffusing into oxic parts of the lake water. Thus, an iron cycle is established where acidity generation through this process (1.0-4.7 mol m-2 a-1) balanced the alkalinity gain through microbial iron reduction in this zone (0.65-4.0 mol m-2 a-1). Predominance of iron over sulfate reduction under acidic conditions is further stabilized by the transformation of schwertmannite to goethite at a depth of 3-5 cm, which releases acidity at a rate of 3.5 mol m-2 a-1. Below, pore-water pH increased to values between 5 and 6, sulfate reduction occurred with a maximum rate of 14 nmol cm-3 d-1 at 9 cm depth. Release of Fe(II) and a short turnover time of reduced sulfur relative to the sediment age implies that most of the sulfide formed seemed to be recycled to sulfate at this depth, presumably coupled to the reduction of iron. Consequently, net alkalinity is generated at low rates only (0.12 mol m-2 a-1).

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER7225
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Biology > Chair Ecological Microbiology
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Biology > Chair Ecological Microbiology > Chair Ecological Microbiology - Univ.-Prof. Harold L. Drake, Ph.D.
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Chair Hydrology
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Chair Hydrology > Chair Hydrology - Univ.-Prof. Dr. Stefan Peiffer
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Biology
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences
Research Institutions
Research Institutions > Research Centres
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 22 Apr 2015 11:59
Last Modified: 27 Apr 2016 08:34
URI: https://eref.uni-bayreuth.de/id/eprint/10977