Dosing, Not the Dose: Comparing Chronic and Pulsed Silver Nanoparticle Exposures

Benjamin P. Colman, Leanne F. Baker, Ryan S. King, Cole W. Matson, Jason M. Unrine, Stella M. Marinakos, Danielle E. Gorka, Emily S. Bernhardt

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


The environmental impacts of manufactured nanoparticles are often studied using high-concentration pulse-additions of freshly synthesized nanoparticles, while predicted releases are characterized by chronic low-concentration additions of weathered particles. To test the effects in wetlands of addition rate and nanoparticle speciation on water column silver concentrations, ecosystem impacts, and silver accumulation by biota, we conducted a year-long mesocosm experiment. We compared a pulse addition of Ag0-NPs to chronic weekly additions of either Ag0-NPs or sulfidized silver nanoparticles. The initially high water column silver concentrations in the pulse treatment declined such that after 4 weeks it was lower on average than in the two chronic treatments. While the pulse caused a marked increase in dissolved methane in the first week of the experiment, the chronic treatments had smaller increases in methane concentration that were more prolonged between weeks 28-45. Much like water column silver, most organisms in chronic treatments had comparable silver concentrations to the pulse treatment after only 4 weeks, and all but one organism had similar or higher concentrations than the pulse treatment after one year. Pulse exposures thus both overestimate the intensity of short-term exposures and effects and underestimate the more realistic long-term exposure, ecosystem effects, and accumulation seen in chronic exposures.

Original languageEnglish
Pages (from-to)10048-10056
Number of pages9
JournalEnvironmental Science and Technology
Issue number17
StatePublished - Sep 4 2018

Bibliographical note

Funding Information:
We thank Anna Fedders for her tireless efforts in the field and in the lab which made this work possible. We also thank Benjamin Espinasse for his capable help in getting the experiment set up and helping during emergencies that arose during the year-long experiment. Finally, we thank Brooke Hassett, Medora Burke-Scoll, Mathieu Therezien, Chris Ward, Carly Gwin, Fabienne Schwab, and Steven Anderson for their many contributions in the lab and in the field, and Shristi Shrestha for her ICP-MS analyses of water samples. 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). Any opinions, findings, conclusions, or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF or the EPA. This work has not been subjected to EPA review and no official endorsement should be inferred.

Publisher Copyright:
© 2018 American Chemical Society.

ASJC Scopus subject areas

  • Chemistry (all)
  • Environmental Chemistry


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