Unraveling Mechanisms of Complex Associations of Organic Carbon with Iron Oxide Minerals during Redox Transformations
EMSL Project ID
50536
Abstract
Fe(III)-oxide nanominerals are ubiquitous primary sorbents of organic carbon, organic acid exudates, and toxic metals in terrestrial, aquatic, and subsurface ecosystems. In soil ecosystems, particularly in the rhizosphere, this co-association has profound impacts on the form and bioavailability of iron to plants and organisms, carbon cycling and the uptake of coupled nutrients and contaminants. At a molecular level the nature of these associations, in particular how they evolve through redox transformation of the iron component, is poorly understood. In principle, this could range from complexation of carbon and metal species at specific sites on iron oxide surfaces, to physical incorporation within the iron oxide structure during co-precipitation or recrystallization. Such processes are often catalyzed by sorbed Fe(II)(aq) from microbially-mediated anaerobic conditions.We propose to capitalize on team momentum based on integrating EMSL capabilities, stable isotopic tracer studies, and high-performance computing, that together have elucidated mechanisms of redox-catalyzed recrystallization of hematite and goethite, to transition into the more complex hierarchical soil biogeochemistry problem of understanding i) Fe(II)-catalyzed transformation of ferrihydrite to goethite, ii) the influence and fate of natural organic matter (NOM). Ferrihydrite is one of the most bioavailable solid iron forms. Preliminary research by our team has established that spontaneous transformation of ferrihydrite anaerobically to less bioavailable phases such as goethite is accelerated almost 1000x by aqueous Fe(II). It has also established that though this nominally facile transformation is inhibited by sorbed NOM, while iron atom exchange between aqueous Fe(II) and ferrihydrite Fe(III) continues. We will approach the mechanistic complexity in this system by systematically evaluating the effects of NOM on the Fe(II)-catalyzed transformation of ferrihydrite, characterizing in molecular-detail the phase and speciation outcomes. We will exploit a diversity of EMSL capabilities, including high resolution electron microscopy and mass-spectrometric imaging and tomography, to tease apart transformation pathways traced by isotopic labeling of key species.
This project will lead to high-impact publications in science areas well-aligned with DOE OBER's stated priority science directions, such as Grand Challenge 4.4 which is to align and deepen connections among conceptual understanding, measurements, and models related to the roles of microbes in determining the rate of transformation, uptake, and loss of chemical elements from ecosystems. And the proposed work helps EMSL fulfill its primary mission as a national scientific user facility, which is to lead molecular-level discoveries for the DOE OBER that translate to predictive understanding and accelerated solutions for national energy and environmental challenges.
Project Details
Project type
Exploratory Research
Start Date
2018-10-21
End Date
2019-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members
Related Publications
Bagus P.S., M. Sassi, and K.M. Rosso. 2019. "Cluster Embedding of Ionic Systems: Point Charges and Extended Ions." Journal of Chemical Physics 151. PNNL-SA-147745. doi:10.1063/1.5108728
Notini L., D. Latta, A. Neumann, C.I. Pearce, M. Sassi, A.T. N'Diaye, and K.M. Rosso, et al. 2019. "A Closer Look at Fe(II) Passivation of Goethite." ACS Earth and Space Chemistry 3, no. 12:2717-2725. PNNL-SA-150749. doi:10.1021/acsearthspacechem.9b00224
Peng H., C.I. Pearce, A.T. N'Diaye, Z. Zhu, J. Ni, K.M. Rosso, and J. Liu. 2019. "Redistribution of Electron Equivalents between Magnetite and Aqueous Fe2+ Induced by a Model Quinone Compound AQDS." Environmental Science & Technology 53, no. 4:1863-1873. PNNL-SA-142677. doi:10.1021/acs.est.8b05098
Stoerzinger K.A., C.I. Pearce, T.C. Droubay, V. Shutthanandan, Z. Liu, E. Arenholz, and K.M. Rosso. 2019. "Structure, Magnetism, and the Interaction of Water with Ti-Doped Fe3O4 Surfaces." Langmuir 35, no. 43:13872-13879. PNNL-SA-145960. doi:10.1021/acs.langmuir.9b02468
Taylor S.D., L. Kovarik, J.B. Cliff, and K.M. Rosso. 2019. "Facet-Selective Adsorption of Fe(II) on Hematite Visualized by Nanoscale Secondary Ion Mass Spectrometry." Environmental Science Nano 6, no. 8:2429-2440. PNNL-SA-144858. doi:10.1039/C9EN00562E