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Ferrihydrite transformations in flooded paddy soils: rates, pathways, and product spatial distributions

Complex interactions between redox-driven element cycles in soils influence iron mineral transformation processes. The rates and pathways of iron mineral transformation processes have been studied intensely in model systems such as mixed suspensions, but transformation in complex heterogeneous porou...

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Autores principales: Grigg, Andrew R. C., ThomasArrigo, Laurel K., Schulz, Katrin, Rothwell, Katherine A., Kaegi, Ralf, Kretzschmar, Ruben
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Royal Society of Chemistry 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9580987/
https://www.ncbi.nlm.nih.gov/pubmed/36131682
http://dx.doi.org/10.1039/d2em00290f
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author Grigg, Andrew R. C.
ThomasArrigo, Laurel K.
Schulz, Katrin
Rothwell, Katherine A.
Kaegi, Ralf
Kretzschmar, Ruben
author_facet Grigg, Andrew R. C.
ThomasArrigo, Laurel K.
Schulz, Katrin
Rothwell, Katherine A.
Kaegi, Ralf
Kretzschmar, Ruben
author_sort Grigg, Andrew R. C.
collection PubMed
description Complex interactions between redox-driven element cycles in soils influence iron mineral transformation processes. The rates and pathways of iron mineral transformation processes have been studied intensely in model systems such as mixed suspensions, but transformation in complex heterogeneous porous media is not well understood. Here, mesh bags containing 0.5 g of ferrihydrite were incubated in five water-saturated paddy soils with contrasting microbial iron-reduction potential for up to twelve weeks. Using X-ray diffraction analysis, we show near-complete transformation of the ferrihydrite to lepidocrocite and goethite within six weeks in the soil with the highest iron(ii) release, and slower transformation with higher ratios of goethite to lepidocrocite in soils with lower iron(ii) release. In the least reduced soil, no mineral transformations were observed. In soils where ferrihydrite transformation occurred, the transformation rate was one to three orders of magnitude slower than transformation in comparable mixed-suspension studies. To interpret the spatial distribution of ferrihydrite and its transformation products, we developed a novel application of confocal micro-Raman spectroscopy in which we identified and mapped minerals on selected cross sections of mesh bag contents. After two weeks of flooded incubation, ferrihydrite was still abundant in the core of some mesh bags, and as a rim at the mineral–soil interface. The reacted outer core contained unevenly mixed ferrihydrite, goethite and lepidocrocite on the micrometre scale. The slower rate of transformation and uneven distribution of product minerals highlight the influence of biogeochemically complex matrices and diffusion processes on the transformation of minerals, and the importance of studying iron mineral transformation in environmental media.
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spelling pubmed-95809872022-10-31 Ferrihydrite transformations in flooded paddy soils: rates, pathways, and product spatial distributions Grigg, Andrew R. C. ThomasArrigo, Laurel K. Schulz, Katrin Rothwell, Katherine A. Kaegi, Ralf Kretzschmar, Ruben Environ Sci Process Impacts Chemistry Complex interactions between redox-driven element cycles in soils influence iron mineral transformation processes. The rates and pathways of iron mineral transformation processes have been studied intensely in model systems such as mixed suspensions, but transformation in complex heterogeneous porous media is not well understood. Here, mesh bags containing 0.5 g of ferrihydrite were incubated in five water-saturated paddy soils with contrasting microbial iron-reduction potential for up to twelve weeks. Using X-ray diffraction analysis, we show near-complete transformation of the ferrihydrite to lepidocrocite and goethite within six weeks in the soil with the highest iron(ii) release, and slower transformation with higher ratios of goethite to lepidocrocite in soils with lower iron(ii) release. In the least reduced soil, no mineral transformations were observed. In soils where ferrihydrite transformation occurred, the transformation rate was one to three orders of magnitude slower than transformation in comparable mixed-suspension studies. To interpret the spatial distribution of ferrihydrite and its transformation products, we developed a novel application of confocal micro-Raman spectroscopy in which we identified and mapped minerals on selected cross sections of mesh bag contents. After two weeks of flooded incubation, ferrihydrite was still abundant in the core of some mesh bags, and as a rim at the mineral–soil interface. The reacted outer core contained unevenly mixed ferrihydrite, goethite and lepidocrocite on the micrometre scale. The slower rate of transformation and uneven distribution of product minerals highlight the influence of biogeochemically complex matrices and diffusion processes on the transformation of minerals, and the importance of studying iron mineral transformation in environmental media. The Royal Society of Chemistry 2022-09-22 /pmc/articles/PMC9580987/ /pubmed/36131682 http://dx.doi.org/10.1039/d2em00290f Text en This journal is © The Royal Society of Chemistry https://creativecommons.org/licenses/by/3.0/
spellingShingle Chemistry
Grigg, Andrew R. C.
ThomasArrigo, Laurel K.
Schulz, Katrin
Rothwell, Katherine A.
Kaegi, Ralf
Kretzschmar, Ruben
Ferrihydrite transformations in flooded paddy soils: rates, pathways, and product spatial distributions
title Ferrihydrite transformations in flooded paddy soils: rates, pathways, and product spatial distributions
title_full Ferrihydrite transformations in flooded paddy soils: rates, pathways, and product spatial distributions
title_fullStr Ferrihydrite transformations in flooded paddy soils: rates, pathways, and product spatial distributions
title_full_unstemmed Ferrihydrite transformations in flooded paddy soils: rates, pathways, and product spatial distributions
title_short Ferrihydrite transformations in flooded paddy soils: rates, pathways, and product spatial distributions
title_sort ferrihydrite transformations in flooded paddy soils: rates, pathways, and product spatial distributions
topic Chemistry
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9580987/
https://www.ncbi.nlm.nih.gov/pubmed/36131682
http://dx.doi.org/10.1039/d2em00290f
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