title: Impact of organic carbon on the stability and toxicity of fresh and stored silver nanoparticles.
abstract: Studies investigating the impact of particle size and capping agents on nanosilver toxicity in pristine laboratory conditions are becoming available. However, the relative importance of known environmental mitigating factors for dissolved silver remains poorly characterized for nanosilver in context with existing predictive toxicity models. This study investigated the implications of freshly prepared versus stored 20 and 100 nm nanosilver stocks to freshwater zooplankton (Ceriodaphnia dubia) in presence and absence of dissolved organic carbon (DOC). Results indicated that while the acute toxicity of nanosilver decreased significantly with larger size and higher DOC, storage resulted in significant increases in toxicity and ion release. The most dramatic decrease in toxicity due to DOC was observed for the 20 nm particle (2.5-6.7 fold decrease), with more modest toxicity reductions observed for the 100 nm particle (2.0-2.4 fold) and dissolved silver (2.7-3.1 fold). While a surface area dosimetry presented an improvement over mass when DOC was absent, the presence of DOC confounded its efficacy. The fraction of dissolved silver in the nanosilver suspensions was most predictive of acute toxicity regardless of system complexity. Biotic Ligand Model (BLM) predictions based on the dissolved fraction in nanosilver suspensions were comparable to observed toxicity.
authors.affiliation: U.S. Army Engineer Research and Development Center, Environmental Laboratory, 3909 Halls Ferry Road, Vicksburg, Mississippi, United States. Alan.J.Kennedy@usace.army.mil
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Kennedy
authors.forename: Mark A
authors.initials: MA
authors.lastname: Chappell
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Bednar
authors.forename: Adam C
authors.initials: AC
authors.lastname: Ryan
authors.forename: Jennifer G
authors.initials: JG
authors.lastname: Laird
authors.forename: Jacob K
authors.initials: JK
authors.lastname: Stanley
authors.forename: Jeffery A
authors.initials: JA
authors.lastname: Steevens
mesh_terms: D000818:Animals; D002244:Carbon; D003621:Daphnia / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005618:Fresh Water; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000633:toxicity*; D008962:Models, Theoretical; D010316:Particle Size; D012834:Silver; D013535:Suspensions; D023382:Toxicity Tests, Acute; D015048:Zooplankton / Q000187:drug effects
chemical_list: D013535:Suspensions; D012834:Silver; D002244:Carbon