Date of Award

12-2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Environmental Toxicology

Advisor

Klaine, Stephen J

Committee Member

Roberts , Aaron P

Committee Member

Bain , Lisa J

Committee Member

Mount , Andrew

Committee Member

Carraway , Elizabeth

Abstract

A particle is classified as nano in size if it has at least one dimension less than 100 nm which gives them chemical and physical characteristics that are different from the bulk material. Over the last twenty years nanotechnology has exploded as an industry. It has been estimated that there are 1000 consumer products on the market today that contain nanomaterials and 2 million jobs worldwide will be devoted directly to nanotechnology research, development, and product manufacturing by 2015. Carbon nanotubes (CNTs) can be visualized as sheets of graphene rolled into a cylinder. Carbon nanotubes small diameter (nanometer scale) and long length (micron scale) give CNTs the unique characteristic of a large aspect ratio, high tensile strength, and high electron conductance which has made them a commonly used nanomaterials in the industry. Despite environmental regulations imposing industrial safeguards chemical contaminants from manufacturing process are often deposited into the aquatic environment. The overall objective of this research was to determine the toxicity and biodistribution of carbon nanotubes to Daphnia magna. Multi-walled nanotubes (MWNTs) suspended in NOM were acutely toxic to D. magna and the average 96 h LC50 value for all the tests with SR-NOM (2.0-18.5 mg/L DOC) was approximately 2 mg/L. However, the MWNT-Edisto River NOM complex was less toxic (LC50 4 mg/L) than MWNT-NOM complexes produced from the other two NOM sources (Black River LC50 2 mg/L and Suwannee River LC50 2mg/L) and this difference in toxicity could not be explained from results of either the particle suspension characterization or the NOM characterization. This study suggested MWNTs were to large to absorb across the gut tract of D. magna, but single-walled nanotubes (SWNTs) have to potential due to their smaller diameter. D. magna were exposed for 96 h to hydroxylated, silca dioxide, poly aminobenzenesulfonic acid, and polyethylene glycol functionalized SWNTs in static renewal bioassays. Using transmission electron microscopy (TEM), high-resolution TEM, selective area diffraction, and electron emission loss spectroscopy we were unable to definitively detect absorption of SWNTs across the gut tract of D. magna for the several different surface modified tubes tested. This suggests that, while there is no absorbance of CNTs, the material may interfere with normal gut processes. Daphnia magna were exposed to MWNTs and SWNTs and resource gene transcription was compared to a control and a starved treatment. An adverse outcome pathway was formed using the changes in resource genes to describe effects to nutrition, energy, growth, and molting that leads to an apical endpoint of reduced reproduction. These studies suggest that suspended CNT exposure has the potential to cause some adverse effects to exposed D. magna. More research needs to be done to adequately determine potential effects at lower concentrations to mimic possible environmental conditions.

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