Date of Award
12-2014
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Legacy Department
Environmental Toxicology
Committee Member
Dr. Stephen Klaine, Committee Chair
Committee Member
Dr. Cindy Lee
Committee Member
Dr. Lisa Bain
Committee Member
Dr. Marie-Noele Croteau
Abstract
Monitoring the distribution and subsequent effects of nanoparticle (NP) contaminants in aquatic ecosystems will be pivotal to developing regulations that minimize their environmental footprint. Regulators are in a unique position to take a proactive role in shaping how we produce and consume nanomaterials as opposed to the reactive role they have had to adopt with other contaminants. Over the last few decades, researchers have made great strides in describing the fate, behavior, and toxicity of NPs in environmental systems. Recent initiatives have made the transition to scenarios with greater environmental relevance, yet important aspects of fate and behavior remain unexplored. The goal of this dissertation research was to fill in several of those gaps, emphasizing relationships between gold NP characteristics, water chemistry and biodynamic parameters that will contribute to development of robust fate and behavior models. Daphnia magna and Pimephales promelas were used as model organisms to differentiate the impact of characteristics and water chemistry on two unrelated species residing in a common aquatic habitat. Uptake and elimination rate constants were derived empirically for D. magna exposed to anionic spheres (4, 20 and 30 nm core diameter) anionic rods (18 x 58 nm) and cationic rods (18 x 58 nm) in moderately hard water (MHW). Size and surface charge greatly affected the uptake and elimination rate constant while shape had a relatively minor influence on accumulation. Multiple linear regression models revealed that D. magna favor accumulation of larger cationic NPs at high concentration exposures and larger anionic NPs at low concentration exposures. D. magna and P. promelas were then challenged with cationic and zwitterionic NPs in MHW and wastewater (WW) that represented a direct release scenario and a WWTP release scenario, respectively. Surface charge influenced not only the biodynamics in MHW exposures for both D. magna and P. promelas but also dictated the interactions between the NP and the wastewater components. Cationic NPs transformed in the presence of WW including an increase in size and a slight decrease in surface charge while zwitterionic NPs were unaffected. The influences of these transformations were species specific as D. magna experienced a significant decrease in the uptake rate constant while neither uptake nor elimination was affected in P. promelas. Finally, we exposed P. promelas to a nano-pharmaceutical (doxorubicin-NP) and the free pharmaceutical (doxorubicin) to determine if the NP altered the distribution and accumulation patterns of the pharmaceutical. The intestine was the primary site of doxorubicin accumulation and the total accumulated content was not significantly affected by the form of the pharmaceutical. Despite a lack of statistical significance, several trends in my data suggest that nano-medicines do not behave like a standard pharmaceutical and, therefore, warrant further investigation to define its environmental impact. Overall my data argue for prioritization of particle characteristics in risk assessment and inclusion of transformative pre-release processes in fate and behavior model development. At the moment releases of NPs into the environment are well below toxic thresholds. Yet as the popularity of nanotechnology further penetrates all aspects of society, engineered NPs will form a larger presence in environmental systems that could give rise to serious environmental consequences. Proactive regulation of NPs aided by comprehensive modeling initiatives are of paramount importance to making sure we use this technology responsibly or else we risk adding another name to the dubious pantheon of legacy contaminants.
Recommended Citation
Wray, Austin Thomas, "Physicocehmical Properties and Pre-Exposure Processes Govern Gold Nanoparticle Accumulation in Freshwater Species" (2014). All Dissertations. 1761.
https://open.clemson.edu/all_dissertations/1761