Deposition of multiwalled carbon nanotubes (MWNTs) on model environmental surfaces was investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D). Deposition behaviors of MWNTs on positively and negatively charged surfaces were in good agreement with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, although hydrophobic interactions dominated MWNTs deposition on a hydrophobic polystyrene surface. Initial deposition rates (rf) and deposition attachment efficiencies (αD) depended on solution ionic strengths (IS) and surface electrostatic properties. Identical rf and αD values at constant IS on similar surfaces suggested that deposition was insensitive to surface morphology (i.e., bare crystal surface vs coated surface). The dissipation unit (D) was used with frequency (f) to investigate nanoparticle deposition: |ΔD/Δf| values varied for deposition on different surfaces, indicating that the nature of MWNT association with surfaces varied despite constant rf and αD values.

Colloidally stable C(60) suspensions produced via extended mixing in water (aq/nC(60)) are highly heterogeneous with respect to particle size and morphology. Ultraviolet-visible (UV-vis) absorption spectra of aq/nC(60) are often used as a supplemental tool to dynamic light scattering (DLS), transmission electron microscopy (TEM), and other analytical methods to characterize aq/nC(60). In the present study, the UV-vis spectra provide information about the average particle size and the interactions between C(60) and water. We report that the decrease in relative absorption in the 240-290 nm range is a function of magnetic stirring time, that the average size (Z(ave)) of an aq/nC(60) suspension determines the position of absorbance maximum of its 360 nm band, and that the methods used to prepare and fractionate nC(60) affect the extent of the blue shift in this band that occurs due to a decrease in Z(ave). We also confirm that the broad absorption band in the 400-600 nm region is a result of C(60) aggregation.

Under the Toxic Substances Control Act (TSCA), the Environmental Protection Agency (EPA) is required to perform new chemical reviews of nanomaterials identified in premanufacture notices. However, environmental fate models developed for traditional contaminants are limited in their ability to simulate nanomaterials' environmental behavior by incomplete understanding and representation of the processes governing nanomaterial distribution in the environment and by scarce empirical data quantifying the interaction of nanomaterials with environmental surfaces. In this study, the well-known Water Quality Analysis Simulation Program (WASP) was updated to incorporate particle collision rate and particle attachment efficiency to simulate multiwalled carbon nanotube (MWCNT) fate and transport in surface waters. Heteroaggregation attachment efficiencies (α) values derived from sediment attachment studies are used to parametrize WASP for simulation of MWCNTs transport in Brier Creek, a coastal plain river located in central eastern Georgia, and a tributary to the Savannah River. Simulations using a constant MWCNT load of 0.1 kg d in the uppermost Brier Creek water segment showed that MWCNTs were present predominantly in the Brier Creek water column, while downstream MWCNT surface and deep sediment concentrations exhibited a general increase with time and distance from the source, suggesting that MWCNT releases could have increasing ecological impacts in the benthic region over long time frames.

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