Plastics are contaminants of emerging concern that are accumulating at increasing rates in the marine and freshwater ecosystems. Some scientists refer to plastics as the next predator of wildlife. Because of the sun and the wave energy, the plastics tend to break down into smaller particles, called microplastics of grain size lower than 5 mm. Microplastics also enter aquatic environments directly from a variety of sources, including cosmetics, clothing, and industrial processes. Microplastics are a cause for concern because their size range overlaps with the preferred particle size ingested by the animals at the base of the aquatic food webs.
The prospective student will be provided an opportunity to learn how to characterize microplastic polymer types by using a novel method of pyrolysis gas chromatography-mass spectrometry (GC-MS). In this method, a small piece of the microplastic sample, less than 1 milligram in weight, is placed in a narrow quartz tube, which is then placed in a platinum coil and heated to 750 degrees C. The intense heat breaks down the large plastic polymer chain into smaller fragments. The pyrolytic fragmentation patterns are reproducible and unique to a given polymer type. These fragments are then transferred to, separated on a gas chromatographic column, and identified using a mass spectrometer. Plastic additives are also identified during this same analytical run.
As a part of the training, the student will analyze a few representative polymer standards to learn the operation of the instrument, the process of peak identification, and matching the peaks with the pyrolysis GC-MS library of different polymers we have created for some of the most commonly used plastics polymers. After learning the peak fingerprinting technique, the next step in this effort will be characterizing the unweathered plastic items and the weathered field samples from sea turtles.
Understanding the nature of microplastics is critical to the identification, and possibly the regulation and mitigation of sources of plastics that can impact the health and sustenance of bivalve, fish, sea turtles, sea birds, and marine mammal habitats, as well as that of the aquaculture facilities.
As different types of plastics exert different toxicities by themselves, and in addition, they adsorb different levels of chemical contaminants, the knowledge of polymer composition is important in the understanding of fisheries risk assessment. Depending upon the student's interest and availability, participation in other concurrent microplastics experiments is encouraged.