R1 PM Nanotechnology Environmental Remediation, Fate, and Transport
Thursday, 17 November 2005: 1:50 PM - 5:30 PM in Ballroom 1

(FER-1117-829068) Fate of single-walled carbon nanotubes in the estuarine environment.

Ferguson, P.¹, DeMarco, A.¹, Templeton, R.¹, Chandler, G.¹, ¹ University of South Carolina, Columbia, SC, USA

ABSTRACT- Single-walled carbon nanotubes (SWNTs) are filamentous manifestations of a repeating aromatic carbon structure formed into an open cylinder. These nanomaterials exhibit novel physical and chemical properties and much attention has been devoted to their commercialization in such applications as structural composites and microelectronics. Because of their unique physicochemical properties and potential for large-scale commercialization, recent concerns have emerged over the potential of nanomaterials such as SWNTs to elicit adverse effects in the aquatic environment. However, little information exists on the environmental fate of these materials in aquatic systems. In order to address the potential for SWNTs to enter, persist, and be transported within estuaries, we have systematically investigated the physicochemical behavior of these materials under simulated estuarine conditions. Specifically, we have utilized dynamic light-scattering analysis to examine the agglomeration of colloidal SWNT suspensions over a range of salinities. Results indicate that SWNTs exist as stable colloidal suspensions (average particle size 200 - 250 nm) in buffered (pH 7) solutions of low ionic strength (10 mM) but that relatively large (average particle size > 2 m) SWNT flocs formed over rapid (minute) timescales as salinity increased over 5 ppt. These results indicate that SWNTs are highly sensitive to changes in solution ionic strength, and that estuarine mixing may play an important role in determining the fate of SWNTs after entry into the aquatic environment (e.g. settling or association with suspended particulates). We will discuss the results of more comprehensive, multivariate experiments designed to test the combined effects of salinity, pH, SWNT concentration, and dissolved organic matter concentration on SWNT aggregation behavior as well as the use of ¹⁴C-labeled SWNTs for quantifying the association of these nanomaterials with estuarine sediments. Finally, we will report on progress in utilizing confocal Raman microspectroscopy to analyze distributions of SWNTs in estuarine sediments and in sediment-ingesting benthic invertebrates (copepods and polychaetes) exposed to SWNTs in a laboratory setting.

Key words: fullerene, nanoscience, estuary