Effects and Bioavailability of Single-walled Carbon Nanotubes in Estuarine Benthic Organisms
Monday, December 5, 2011
Ashley Parks is a CEINT graduate student.
Abstract: Single walled carbon nanotubes (SWNT) are highly ordered, filamentous nanocarbon structures. As their commercial and industrial use becomes more widespread, it is anticipated that SWNT will enter the environment through waste streams and product degradation. Previous studies in our laboratory and others have found that SWNT associate strongly with natural particulate matter in the aquatic environment. We utilized sediment and food exposure routes to assess the toxicity, bioaccumulation, and trophic transfer of structurally diverse SWNT (various chiral wrapping angles and diameters) in several ecologically-important marine invertebrate toxicity test species: the amphipods Ampelisca abdita and Leptocheirus plumulosus, the mysid shrimp Americamysis bahia, the filter-feeding clam Mercenaria mercenaria, and the clam worm Nereis virens. No significant mortality was observed in any organisms up to 1000 ppm. Uptake in organism tissues was detected using one of two methods. For pristine semiconducting SWNT, near infrared fluorescence (NIRF) spectroscopy was used to detect, characterize and quantify SWNT in tissues and sample matrices with a detection limit of 5 µg/g. Although NIRF spectroscopy provides more detailed characterization and can be used to analyze environmental samples, radiolabels were used as a second detection method as they offer a lower detection limit (0.044 µg/g) for laboratory-based bioaccumulation studies. In both the pristine SWNT and 14C-SWNT experiments, significant uptake was present in non-depurated amphipods followed by significant reduction after a 24 hour depuration period. The trophic transfer potential of SWNT was evaluated by feeding clams SWNT-amended algae, and then these clams were fed to worms. Of the samples analyzed thus far, no uptake was observed from algae to clam. Since no toxicity and minimal bioaccumulation were observed, we wanted to investigate the effect of SWNT on co-contaminants. Once SWNT enter the environment, they will co-occur with other contaminants. Our lab has shown that hydrophobic organic contaminants will sorb to SWNT, so we wanted to investigate this in environmentally relevant sediment. We amended New Bedford Harbor (NBH) sediment, which is contaminated with polychlorinated biphenyls (PCBs), with pristine SWNT to determine if the presence of SWNT would mitigate the toxicity and bioaccumulation of the contaminants. The results of this work do show a trend of increased survival in treatments amended with SWNT. Overall, SWNT do not lead to significant mortality or bioaccumulation in benthic invertebrates up to 1000 ppm through sediment and food exposure routes. They do however seem to mitigate the toxicity of PCBs present in NBH sediment."