Predicting nanoparticle fate in aquatic environments requires mimicking of ecosystem complexity to observe the geochemical processes affecting their behaviour. Here, 12 nm Au nanoparticles were added weekly to large-scale freshwater wetland mesocosms. After six months, ~70% of Au was associated with the macrophyte Egeria densa, where, despite the thermodynamic stability of Au0 in water, the pristine Au0 nanoparticles were fully oxidized and complexed to cyanide, hydroxyls or thiol ligands. Extracted biofilms growing on E. densa leaves were shown to dissolve Au nanoparticles within days. The Au biodissolution rate was highest for the biofilm with the lowest prevalence of metal-resistant taxa but the highest ability to release cyanide, known to promote Au0 oxidation and complexation. Macrophytes and the associated microbiome thus form a biologically active system that can be a major sink for nanoparticle accumulation and transformations. Nanoparticle biotransformation in these compartments should not be ignored, even for nanoparticles commonly considered to be stable in the environment.

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The authors thank S. M. Anderson and B. P. Colman for their help setting up, monitoring and collecting samples during the experiment, S. Marinakos for providing TEM characterization of the Au-NPs, A. Curinier for insights and B. Perrotta for analyses of Au concentrations on mesocosm biofilms. This work was supported by the National Science Foundation (NSF) and the Environmental Protection Agency (EPA) under NSF Cooperative Agreement EF-0830093 and DBI-1266252, Center for the Environmental Implications of NanoTechnology (CEINT). Funds for graduate student summer support was supplied by the Duke Wetland Center Endowment. Portions of this work were performed at the Stanford Synchrotron Radiation Lightsource (SSRL) on beamline 11-2, a Department of Energy supported facility.

Author information


  1. Center for the Environmental Implications of NanoTechnology (CEINT), Durham, NC, USA

    • Astrid Avellan
    • , Marie Simonin
    • , Eric McGivney
    • , Nathan Bossa
    • , Eleanor Spielman-Sun
    • , Emily S. Bernhardt
    • , Nicholas K. Geitner
    • , Jason M. Unrine
    • , Mark R. Wiesner
    •  & Gregory V. Lowry
  2. Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA, USA

    • Astrid Avellan
    • , Eric McGivney
    • , Eleanor Spielman-Sun
    •  & Gregory V. Lowry
  3. Department of Biology, Duke University, Durham, NC, USA

    • Marie Simonin
    • , Jennifer D. Rocca
    •  & Emily S. Bernhardt
  4. Civil & Environmental Engineering, Duke University, Durham, NC, USA

    • Nathan Bossa
    • , Nicholas K. Geitner
    •  & Mark R. Wiesner
  5. Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, USA

    • Jason M. Unrine


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A.A., M.S., E.M., N.B., E.S.-S. and J.D.R. performed experiments and/or data analysis. A.A., M.S., E.S.B., N.K.G., M.R.W., J.M.U. and G.V.L. were involved in experimental design and writing. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Gregory V. Lowry.

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  1. Supporting information

    Supplementary Figures 1–7, Supplementary Table 1

  2. Supplementary dataset

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  4. Supplementary dataset

    Sequence file 3

  5. Supplementary dataset

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