Iron mineral dissolution releases iron and associated organic carbon during permafrost thaw
Creators
- 1. Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Schnarrenbergstrasse 94-96, 72076 Tuebingen, Germany
- 2. Department of Geosciences and Natural Resource Management, University in Copenhagen, Øster Voldgade 10, 1350 København K, Denmark
- 3. Soil Science and Geomorphology, University of Tuebingen, Ruemelinstraße 19-23, 72070 Tuebingen, Germany
- 4. Lehrstuhl für Bodenkunde, Technische Universitaet Muenchen, Emil-Ramann Strasse 2, 85354, Freising, Germany
- 5. Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road BS8 1RJ, Bristol, UK
Description
It has been shown that reactive soil minerals, specifically iron(III) (oxyhydr)oxides, can trap organic carbon in soils overlying intact permafrost, and may limit carbon mobilization and degradation as it is observed in other environments. However, the use of iron(III)-bearing minerals as terminal electron acceptors in permafrost environments and thus their stability and capacity to prevent carbon mobilization during permafrost thaw is poorly understood. We have followed the dynamic interactions between iron and carbon, using a space for time-approach, across a thaw gradient in Abisko (Sweden), where wetlands are expanding rapidly due to permafrost thaw. We show through bulk (selective extractions, EXAFS) and nanoscale analysis (correlative SEM and nanoSIMS) that organic carbon is bound to reactive Fe primarily in the transition between organic and mineral horizons in palsa underlain by intact permafrost (41.8 ± 10.8 mg carbon per g soil, 9.9 to 14.8% of total soil organic carbon). During permafrost thaw, water-logging and O2 limitation lead to reducing conditions and an increase in abundance of Fe(III)-reducing bacteria which favor mineral dissolution and drive mobilization of both iron and carbon along the thaw gradient. By providing a terminal electron acceptor, this rusty carbon sink is effectively destroyed along the thaw gradient and cannot prevent carbon release with thaw.
Files
Files
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