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Studies of Soil Mineral-Organic Matter Associations and Plant Nutrient Fixation Using Synchrotron X-ray Methods
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  • Tamas Varga,
  • Ravi Kukkadapu,
  • Alice Dohnalkova,
  • Libor Kovarik,
  • Matthew Marcus,
  • Amir Ahkami,
  • Rosalie Chu,
  • Kim Hixson,
  • Carrie Nicora,
  • Tanya Winkler,
  • Loren Reno,
  • Anil Battu,
  • Morgan Barnes,
  • Olga Antipova,
  • Sirine Fakra,
  • Dilworth Parkinson,
  • Sharon Doty
Tamas Varga
Pacific Northwest National Laboratory

Corresponding Author:tamas.varga@pnnl.gov

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Ravi Kukkadapu
Pacific Northwest National Lab
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Alice Dohnalkova
Pacific Northwest National Laboratory
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Libor Kovarik
Pacific Northwest National Laboratory
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Matthew Marcus
Lawrence Berkeley National Laboratory
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Amir Ahkami
Pacific Northwest National Laboratory
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Rosalie Chu
Pacific Northwest National Laboratory
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Kim Hixson
Pacific Northwest National Laboratory
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Carrie Nicora
Pacific Northwest National Laboratory
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Tanya Winkler
Pacific Northwest National Laboratory
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Loren Reno
Pacific Northwest National Laboratory
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Anil Battu
Pacific Northwest National Laboratory
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Morgan Barnes
University of California Merced
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Olga Antipova
Argonne National Laboratory
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Sirine Fakra
Lawrence Berkeley National Laboratory
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Dilworth Parkinson
Lawrence Berkeley National Laboratory
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Sharon Doty
University of Washington Seattle Campus
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Abstract

To address some challenging biological and environmental problems, scientists at the Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory (PNNL) have been pairing scientific capabilities at their home institution with the bright, tunable energy x-rays and high-resolution instruments at several national synchrotron user facilities. Synchrotron techniques can help answer a variety questions, and two examples featuring synchrotron-based structural and chemical imaging in bio/geochemical systems will be presented. In the first example, x-ray fluorescence spectromicroscopy and microtomography were used to visualize and better understand phosphorous uptake in poplar trees. Endophyte-promoted phosphorous uptake was seen inside poplar roots, where the fixated phosphorous appeared to be in the form of an organic phosphate. Analysis of the tomography data showing increased root mass for the plants inoculated with the endophytes supported the picture of increased nutrient uptake in those plants. These results along with in-house proteomics characterization point to the biological relevance of the symbiosis between endophytes and the host plant. In the second example, scanning transmission x-ray microscopy (STXM) combined with x-ray absorption near edge structure (XANES) helped us investigate soil mineral – soil organic matter (SOM) interactions in an alkaline soil from Washington state. Ca mineral–organic associations were found to be predominant which may play a critical role in the stabilization/degradation of SOM and mineral. Micro- and nanoscale characterization of the chemical state of both Ca from the mineral and C from the organic matter are crucial for understanding such stabilization mechanisms as well as soil nutrient dynamics.