The validation and application of new methods in microplastics research

Abstract

Plastic products subjected to natural weathering and anthropogenic activities splinter into progressively finer particles throughout their entire lifecycle. Eight decades of this material’s continual degradation, combined with an ever-expanding global plastics market, results in the gradual accumulation of small (1 – 5,000 µm) synthetic particles known as microplastics. These fossil fuel-derived materials settle and flow between environmental matrices such as air, water, soil, and biota as fragments, fibers, foams, and films. While their presence is known and thoroughly documented, questions remain about the source, fate, and transport of microplastics, the human and ecological health implications, and the most effective means of constraining their planetary circulation. These questions persist, in part, because released contaminant particles are vastly heterogeneous. Their original fabrication involves an essential synthetic polymer or co-polymer resin merged with myriad chemical additives subjected to a unique set of degradative forces that may involve mechanical stress and/or distinct enzymatic and chemical conditions. In addition to these challenges, the methods applied to isolate, identify, and characterize contaminant particles are not fully standardized, making results difficult to replicate and leaving uncertainty about findings. This dissertation seeks to enhance sample processing methods for the detection, enumeration, and physical-chemical characterization of microplastic contamination for three applications: 1) fate and transport research, 2) consumer exposure research, and 3) efforts to enhance science literacy. While this work focuses on advancing laboratory processing methods for the extraction of microplastics from filtered lab water and potable tap water, they can easily extend to other environmental media such as air, raw water, and wastewater. Method enhancement centers on improving quality assurance and quality control measures and generating a comprehensive chemical and physical profile of contaminant particles. This validated method, applied to a 52-week examination of urban atmospheric fallout in a humid continental climate, elucidates particle fate and transport by comparing abundance, size, morphology, and chemical composition of microplastic contaminant particles in weather conditions that vary in terms of precipitation and temperature. Next, the improved methods are applied to a study involving the potential release of microplastics from reusable sports water bottles as they are used and cared for by members of a local cycling team over the course of 92 days. Once again, microplastic abundance, size, morphology, and chemical composition are examined to see if there are any changes linked to bottle composition and design, frequency of use, and washing habits. Finally, these verified methods are adapted for use by non-scientists in a statewide citizen science project that seeks to educate high school students about microplastic contaminants, improve overall science literacy, foster civic engagement, while generating rigorous data across a broad temporal and geographic expanse.