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Size-dependent reactivity of magnetite nanoparticles: a field-laboratory comparison

September 9, 2014

Logistic challenges make direct comparisons between laboratory- and field-based investigations into the size-dependent reactivity of nanomaterials difficult. This investigation sought to compare the size-dependent reactivity of nanoparticles in a field setting to a laboratory analog using the specific example of magnetite dissolution. Synthetic magnetite nanoparticles of three size intervals, ∼6 nm, ∼44 nm, and ∼90 nm were emplaced in the subsurface of the USGS research site at the Norman Landfill for up to 30 days using custom-made subsurface nanoparticle holders. Laboratory analog dissolution experiments were conducted using synthetic groundwater. Reaction products were analyzed via TEM and SEM and compared to initial particle characterizations. Field results indicated that an organic coating developed on the particle surfaces largely inhibiting reactivity. Limited dissolution occurred, with the amount of dissolution decreasing as particle size decreased. Conversely, the laboratory analogs without organics revealed greater dissolution of the smaller particles. These results showed that the presence of dissolved organics led to a nearly complete reversal in the size-dependent reactivity trends displayed between the field and laboratory experiments indicating that size-dependent trends observed in laboratory investigations may not be relevant in organic-rich natural systems.

Publication Year 2014
Title Size-dependent reactivity of magnetite nanoparticles: a field-laboratory comparison
DOI 10.1021/es500172p
Authors Andrew L. Swindle, Andrew S. Elwood Madden, Isabelle M. Cozzarelli, Mourad Benamara
Publication Type Article
Publication Subtype Journal Article
Series Title Environmental Science & Technology
Index ID 70126398
Record Source USGS Publications Warehouse
USGS Organization National Research Program; Toxic Substances Hydrology Program