The Accumulation of Microplastics in Craig Bay, British Columbia

Abstract

Microplastics originate from large plastic materials degraded by physical, chemical, or biological means. They are transported to marine environments by wind and water before deposition into sediment. Estuaries are microplastic sinks that can provide information about dominant plastic types and microplastic retention in marine environments. Large, heavy microplastics are expected to be deposited closer to their source than smaller particles. Samples were collected from Craig Bay to determine if depositional environments affect microplastic deposition. To determine grain size distributions and dominant grain size, 12.5g of each sample was sifted through various sieves (4000, 2000, 1000, 500, 250, 125, and 63µm, respectively). The amount of organic matter was determined by combusting 30g of each unsorted sample in a muffle furnace. Another portion (25g) of each unsorted sample was used to extract microplastics by density floatation and enzyme digestion. Microplastics were isolated onto stainless steel filters and underwent Raman spectroscopy to identify the chemical composition. Microplastics were quantified visually within three strips along each filter, and 10% of identified particles underwent Raman spectroscopy. Particles were classified as fiber, film, or fragment. Samples dominated by silt and clay contained the least amount of microplastics, but the most organic matter. Samples that were dominated by fine sand had the most microplastics, but the least organic matter. Polytetrafluoroethylene was found to be the most abundant microplastic among all the samples. The work is part of a new and emerging research area within sedimentology that focuses on the correlation between sediments and microplastics.

Faculty Mentor: Dr. Matthew Ross