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Volume 11, issue 18
Biogeosciences, 11, 5259–5267, 2014
https://doi.org/10.5194/bg-11-5259-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 11, 5259–5267, 2014
https://doi.org/10.5194/bg-11-5259-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 30 Sep 2014

Research article | 30 Sep 2014

X-ray fluorescence mapping of mercury on suspended mineral particles and diatoms in a contaminated freshwater system

B. Gu1, B. Mishra2, C. Miller1, W. Wang1, B. Lai3, S. C. Brooks1, K. M. Kemner2, and L. Liang1 B. Gu et al.
  • 1Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
  • 2Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
  • 3X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA

Abstract. Mercury (Hg) bioavailability and geochemical cycling is affected by its partitioning between the aqueous and particulate phases. We applied a synchrotron-based X-ray fluorescence (XRF) microprobe to visualize and quantify directly the spatial localization of Hg and its correlations with other elements of interest on suspended particles from a Hg-contaminated freshwater system. Up to 175 μg g−1 Hg is found on suspended particles, but less than 0.01% is in the form of methylmercury. Mercury is heterogeneously distributed among phytoplankton (e.g., diatoms) and mineral particles that are rich in iron oxides and natural organic matter (NOM). The diatom-bound Hg is mostly found on outer surfaces of the cells, suggesting passive sorption of Hg on diatoms. Our results indicate that localized sorption of Hg onto suspended particles, including diatoms and NOM-coated oxide minerals, may play an important role in affecting the partitioning, reactivity, and biogeochemical cycling of Hg in natural aquatic environments.

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