Categorization of plastic debris on sixty-six beaches of the Laurentian Great Lakes, North America

Abstract The Laurentian Great Lakes system is a major global sink for plastic debris. An area of 10 m 2 on each of sixty-six Great Lakes beaches was sampled for large micro-, meso- and macroplastic items. A total of 21 592 plastic items were collected and categorized. Pre-production plastic pellets were the most abundant debris type, accounting for 58.3% of the total count. The remaining 42.7% of the debris items are the focus of this study. Detailed, multi-step characterization was performed with the plastics being categorized using physical identification, known usage, and Fourier transform infrared spectroscopy (FTIR). Values of 805.5 items m −2 at Baxter Beach in Sarnia, Ontario, Canada, and 688.1 items m −2 at Bronte Beach in Oakville, Ontario, Canada are the highest of all sampling locations. Sampling sites on only three beaches contained no plastic debris: Bay City in Michigan, U.S.A., Presque Isle State Park in Erie, Pennsylvania, U.S.A. and Pebble Beach in Marathon, Ontario, Canada. The plastic items sampled were mainly large microplastics (68.4% of total) with a total of 1477.5 items m −2 , followed by mesoplastics (27.3% of total) with 598.8 items m −2 , and macroplastics (4.3% of total) with 91.9 items m −2 . By mass, the microplastic fraction accounted for 25.61 g m 2 (14.1%), the mesoplastic for 47.06 g m 2 (25.9%), and macroplastic for 109.3 g m 2 (60.1%). A total of 3004 items were determined as specific polymers based on physical properties, known polymer usage, Resin Identification Code, and FTIR. A total of 1227 plastic items (40.8% of total) were identified as expanded polystyrene. The 49 most common items, excluding pellets, were scored using a matrix scoring technique to determine their potential general origin. It was determined that these items mostly originated from shoreline and urban sources, whereas pellets originated from the plastics industry.