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Iron (hydr)oxide formation in Andosols under extreme climate conditions

  • Redox-driven biogeochemical cycling of iron plays an integral role in the complex process network of ecosystems, such as carbon cycling, the fate of nutrients and greenhouse gas emissions. We investigate Fe-(hydr)oxide (trans)formation pathways from rhyolitic tephra in acidic topsoils of South Patagonian Andosols to evaluate the ecological relevance of terrestrial iron cycling for this sensitive fjord ecosystem. Using bulk geochemical analyses combined with micrometer-scale-measurements on individual soil aggregates and tephra pumice, we document biotic and abiotic pathways of Fe released from the glassy tephra matrix and titanomagnetite phenocrysts. During successive redox cycles that are controlled by frequent hydrological perturbations under hyper-humid climate, (trans)formations of ferrihydrite-organic matter coprecipitates, maghemite and hematite are closely linked to tephra weathering and organic matter turnover. These Fe-(hydr)oxides nucleate after glass dissolution and complexation with organic ligands, through maghemitization or dissolution-(re)crystallization processes from metastable precursors. Ultimately, hematite represents the most thermodynamically stable Fe-(hydr)oxide formed under these conditions and physically accumulates at redox interfaces, whereas the ferrihydrite coprecipitates represent a so far underappreciated terrestrial source of bio-available iron for fjord bioproductivity. The insights into Fe-(hydr)oxide (trans)formation in Andosols have implications for a better understanding of biogeochemical cycling of iron in this unique Patagonian fjord ecosystem.

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Author:Björn Klaes, Sören Thiele-Bruhn, Gerhard Wörner, Carmen Höschen, Mueller Carsten W., Philipp Marx, Helge Wolfgang Arz, Sonja Breuer, Rolf Kilian
Parent Title (English):Scientific Reports
Publisher:Nature Portfolio
Place of publication:London
Document Type:Article
Date of completion:2023/02/16
Date of publication:2023/02/16
Publishing institution:Universität Trier
Contributing corporation:The publication was funded by the Open Access Fund of Universität Trier and the German Research Foundation (DFG)
Release Date:2023/12/12
GND Keyword:Andosol; Biogeochemie; Eisenhydroxide; Eisenoxide; Patagonien Süd
Volume (for the year ...):2023
Issue / no.:Band 13
Number of pages:17
Institutes:Fachbereich 6 / Raum- und Umweltwissenschaften
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 55 Geowissenschaften, Geologie / 550 Geowissenschaften
Licence (German):License LogoCC BY: Creative-Commons-Lizenz 4.0 International

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