# Presentation: 885164

## Chemical and Biological Behavior of Carbon Nanotubes in Estuarine Sedimentary Systems

- P. Lee Ferguson1, G. Thomas Chandler2, and Wally A. Scrivens1
- 1Department of Chemistry and Biochemistry, 2Department of Environmental Health Sciences, University of South Carolina, Columbia, SC

## Carbon nanotubes as environmental toxicants

- As nanomaterials, including carbon nanotubes begin to find their way into commercial and industrial applications, they will inevitably find their way into the ambient environment
- Recently, aqueous C60 exposure has been found to induce oxidative stress (lipid peroxidation) in the brain of largemouth bass at 0.5 ppm concentration (E. Oberdörster, 2004 *Environmental Health Perspectives*)
- Carbon SWNTs are hydrophobic and will likely associate strongly with sediments upon entry into the aquatic environment
- In sediments, these materials may cause toxicity to benthic, sediment ingesting organisms and may impact the disposition of persistent and bioaccumulative organic contaminants such as PCBs and PAHs

## Study objectives

- Determine factors controlling the fate of SWNTs in estuarine seawater, sediment, and sediment-ingesting organisms
- Examine impact of SWNTs on the disposition of model organic contaminants in estuarine sediments
- Determine whether the presence of SWNTs in estuarine sediments affects the bioavailability of model organic contaminants to suspension- and deposit-feeding estuarine invertebrates
- Assess the toxicity of SWNTs to a model deposit-feeding estuarine invertebrate in seawater and /or in combination with estuarine sediments

## Synthesis and purification of 14C-SWNT materials

- Purified SWNTs

- Fluorescent impurities

- Nano rods

- Arc-discharge synthesis (14C electrode dopant)

- Oxidative treatment

- Electrophoretic purification

## Experimental approach

- Utilize radiolabeled SWNT material to track sorption to sediments, flocculation, colloid formation under simulated estuarine conditions (salinity, DOM)
- Track sediment-associated 14C-SWNTs through ingestion by deposit feeding organisms to assess bioaccumulation
- Use model hydrophobic organic contaminants to evaluate sorption potential of SWNTs and their impact on priority pollutant bioavailability in sediments
- Evaluate toxicity of SWNTs using a multiple-endpoint sediment toxicity bioassay developed in previous work for EPA

## Size distribution of SWNT clusters in simulated estuarine seawater

## Evaluating sorption of HOCs to SWNTs using common headspace partitioning

- Foil-lined cap

- Aqueous buffer

- SWNT suspension

- Shared headspace

- Model sorbates:
- 14C-hexachlorobenzene
- 14C-napthalene

## Confocal microscope image stack of a 6 m SWNT cluster stained with BODIPY 505/515

- Confocal microscope image stack of a 6 m SWNT cluster stained with BODIPY 505/515

## Sediment toxicity/bioaccumulation bioassay

## Slide 10

## Bioassay endpoint selection

## Expected benefits

- Fate tracking in estuarine sediments will inform about potential disposition of SWNTs discharged to the aquatic environment, useful in environmental exposure risk assessment
- Sorption and bioavailability studies will reveal the possible impact of SWNTs on the fate and effect of hydrophobic organic contaminants in estuarine sediments
- Toxicity studies will lead to increased understanding of the potential effects of SWNTs on trophically important estuarine invertebrates in sediments