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Using single particle ICP-MS to study occurrence and behavior of engineered, natural, and incidental nanoparticles in freshwater streams
Rand, Logan N.
Rand, Logan N.
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2019
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Abstract
The use of engineered nanoparticles (ENPs) in numerous industrial and consumer applications is steadily increasing, which has led to concern about their environmental release. However, the study of ENP fate and transport has been met with significant technical challenges. Low (parts per trillion) concentrations and the frequent complexity of environmental media makes accurate detection difficult, even without the added possibility of ENP alteration via aggregation, surface modification, and degradation (dissolution). Additionally, there are many mineral analogues to ENPs and these natural nanoparticles (NNPs) are not easy to distinguish from ENPs. Human activities also result in many incidental nanoparticle (INP) byproducts in the environment. The Ph.D. dissertation research described in this thesis contributes to the current attempts to improve environmental nanoparticle (NP) analysis and better understand NP behavior in natural systems, with the focus being on streams and the application of single particle inductively coupled plasma-mass spectrometry (spICP-MS) for NP measurement. Two field studies in this thesis demonstrate the utility and limitations of the technique for quantifying changes to NP populations in dynamic natural water systems, including semi-urban recreational streams and a mining-impacted stream. Total metal mass concentrations, oxybenzone, and NPs were examined during stream recreation in Clear Creek, Colorado, Truckee River, Nevada, and Salt River, Arizona and in some instances significant increases in Ti NP concentrations and sizes were observed by spICP-MS. The study on the mining-impacted system found a decrease in Fe INP concentration and size occurred that could be related via multiple linear regression to seasonal and remediation-related water chemistry changes in the North Fork of Clear Creek, Colorado. Additionally, the ability of spICP-MS to analyze aggregated NPs was examined and compared between instruments with magnetic sector versus time-of-flight mass analyzers. The results support the detectability of small (up to 200 nm) aggregates of CeO2, goethite, and kaolinite NPs based on changes to size distributions and signal pulse clumping, as well as simultaneous pulses of multiple elements, depending on the analytical capabilities of the instrument used. This dissertation advances the ability to measure ENPs, NNPs, and INPs in the environment and contributes to our understanding of anthropogenic effects on stream NPs.
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