Single particle inductively coupled plasma spectroscopy (sp-ICP-MS) as a tool for identifying, quantifying and studying the transformation of anthropogenic nanomaterials

Abstract

Nanomaterials in the environment occupy a wide variety of roles in the environment due to their unique, size-dependent reactivity. Abundant, natural nanomaterials influence a wide variety of geochemical processes such the global transport of micronutrients through aeolian dust or the bioavailability of metal ions in aqueous systems. Furthermore, the expansion of human activity has caused newer, incidental and engineered nanomaterials to enter the environment in increasing concentrations with unknown effects. Characterization of these environmental nanomaterials is essential to understanding natural geochemical cycles and the effects that anthropogenic activity have upon them. Single Particle Inductively Coupled Plasma Mass Spectrometry (spICP-MS) is a technique of growing importance in the analysis of environmental materials. Nanoparticles are ablated, ionized and detected through this technique revealing their elemental content and size. Although in widespread use, environmentally sampled nanomaterials can confound this technique due to their broad and continuous distributions of particles of sizes ranging in orders of magnitude. The three chapters of original research presented herein attempt to lay out guideposts for the analysis of these environmental nanomaterials. The first chapter combines simple techniques such as settling and filtration to increase the depth of information obtained from a simple spICP-MS analysis and presents the results of combining spICP-MS with a time-of-flight detector for particle-specific, multi-element characterization. The second chapter lays out a method of modeling spICP-MS analysis using a power law model which provides a more accurate measurement of particle size and number concentration than a simple analysis of mean particle size and detected number. Lastly, we apply the lessons of the previous chapter to study the UV degradation of nanoplastics, a difficult to analyze and dangerous environmental contaminant. The lessons in spICP-MS data analysis and experimental design presented in this thesis will hopefully be of use to future environmental researchers.