MECHANISMS OF SORPTION OF PHARMACEUTICAL AND PERSONAL CARE PRODUCTS TO MICROPLASTICS
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Microplastics (MPs) are found in almost every ecosystem and in many commercially important seafood species. MPs have been found to be physically harmful to marine organisms, but also may act as vectors for organic pollutants and together have been shown to cause toxic effects in a variety of species. Wastewater effluent is a significant source of MPs to aquatic systems, as well as pharmaceutical and personal care product compounds (PPCPs). The first research contribution was to create a reference material for secondary fragment type microplastics of the polymer’s high-density polyethylene (HDPE) and polypropylene (PP) that is standardized by surface area (SA) for use in sorption and toxicity studies. Standardization for both polymers was successful, with a SA coefficient of variation of ~3%. PP MPs had greater SA due to it being a less crystalline polymer than HDPE. This reference material may act as a more realistic material than purchased powders or beads, as well as provide a more readily comparable material for fragment type MPs. The second research contribution used the reference material to create an extraction methodology for measuring semi-polar PPCPs associated with MPs. Acetone was chosen as the best solvent for extraction and extraction efficiency for both polymers was ~88% (first extraction). This methodology was then used to measure the equilibrium of the antimicrobial triclocarban with PP and PE of different MP particle sizes. Smaller particles with greater SA sorbed more triclocarban, rather than larger particles. PP had greater sorption of triclocarban than PE. This was due to PP MPs having greater SA due to being a less crystalline polymer. The third contribution created a framework for prioritizing study compounds based on environmental relevance for MP sorption using polyethylene as a model polymer, water solubility, and a correlation with the octanol water-distribution ratio, DOW, rather than the octanol-water partition coefficient, KOW. A possible threshold for polyethylene sorption was found for compounds with water solubility ~20-60mg/L and DOW ~3.7. This dissertation advances the understanding of MP reference materials, extraction methodology, sorption mechanisms, and modeling of sorption data of PPCPs.