Factors driving the spatial distribution of microplastics in nearshore and offshore sediment of Lake Huron, North America.

Offshore and nearshore sediment samples from Lake Huron, North America, were analysed for microplastics. Normalized abundances ranged from 59 to 335,714 particles per kg of dry weight sediment (p kg-1 dw). Of the four main basins of Lake Huron, the North Channel contained the greatest microplastic abundances, averaging 47,398 p kg-1 dw, followed by Georgian Bay (21,390 p kg-1 dw), the main basin (15,910 p kg-1 dw) and Saginaw Bay (1592 p kg-1 dw). Results indicate that greater lake depths (p = 0.004), associated with finer grained sediment (p = 0.048), are significant zones of deposition. Regression analysis reveals that source-driven factors generally do not account for microplastic abundances and distribution. Instead, process-driven hydrodynamic forces such as waves and surface currents could be driving distribution and deposition into the offshore environment. The findings suggest that these often overlooked processes should be considered when investigating microplastics quantity in bottom sediment of large lakes.

A comprehensive investigation of industrial plastic pellets on beaches across the Laurentian Great Lakes and the factors governing their distribution.

Industrial, pre-consumer pellets are a major type of plastics pollution found on shorelines worldwide. This study investigates the distribution and characteristics of plastic pellets accumulated on beaches of the Laurentian Great Lakes of North America and provides a "snapshot" of pellet distribution in a lake system that accounts for 21% of the world's freshwater reserves. We sampled pellets simultaneously from 10m2 quadrats on 66 beaches and characterized the 12,595 pellets collected (average of 19.1 pellets/m2). Forty-two beaches contained pellets and 86% of the pellets were found on three beaches: Rossport (Lake Superior), Baxter (Lake Huron), and Bronte (Lake Ontario). The number of pellets on each beach was compared with factors hypothesized to control their accumulation. In general, positive correlations were found between pellet abundance and watershed population, number of plastic-related industries, and proximity to a river mouth, although for Lake Superior, abundance was related to a train spill that took place over 10 years ago. Beach grain size appears to be related to pellet abundance, with very fine sand, fine sand and medium sand containing the greatest number of pellets. All pellets were visually characterized based on size, color, shape, weathering, and distinguishing traits. The predominant color was white, oblate shapes were most common, and the main distinguishing trait was a dimple. Most pellets showed little evidence of weathering, with the weathered samples mainly from Lakes Erie and Ontario. Lake Ontario pellets were the most varied, with 6/7 shapes, 35/40 colors, and 21/25 distinguishing traits, indicating a wider range of pellet sources compared to the other lakes. Polymer compositions were mainly polyethylene (PE) and polypropylene (PP). Our results will lead to increased recognition of regional pellet pollution in the Great Lakes watershed, thereby motivating change during their production, transport and use.

Factors Controlling the Distribution of Microplastic Particles in Benthic Sediment of the Thames River, Canada.

Investigations of microplastic abundances in freshwater environments have become more common in the past five years, but few studies concern the factors that control the distribution of microplastics in river systems. We sampled benthic sediment from 34 stations along the Thames River in Ontario, Canada, to determine the influence of land use, grain size, river morphology, and relative amount of organic debris on the distribution of microplastics. Once counted and characterized for shape, color, and size, microplastic abundances were normalized to the results from Fourier transform infrared spectroscopy on randomly selected particles. The results indicate that 78% of the fragments and only 33% of the fibers analyzed were plastic. The normalized microplastic quantities ranged from 6 to 2444 particles per kg of dry weight sediment (kg-1 dw). The greatest number of microplastics were identified in samples of the finest grain sizes and with the greatest amount of organic debris. Although there was no significant difference between microplastic abundances in urban versus rural locations, the average microplastic count for urban samples was greater (269 vs 195 kg-1 dw). In terms of river morphology, samples from along straight courses of the river contained fewer microplastics than samples from inner and outer bends. Overall abundances confirm how rivers contain a significant number of plastic particles and thus may be major conduits of microplastics to lake and ocean basins.

Embracing an interdisciplinary approach to plastics pollution awareness and action.

This paper considers how an interdisciplinary approach to the "wicked problem" of plastics pollution offers unique and important collaborative possibilities. Specially, the paper considers the approach of the Synthetic Collective, a group comprising artists, humanities scholars, and scientists. Considering first how artists and scientists might respond differently to tracking, mapping, understanding, and representing plastics pollution, we then look for potential points of commonality across disciplinary difference. In respect to the urgent and multifaceted problem of marine plastics pollution in the Great Lakes region, we ask what are some of the successes and pitfalls of bringing together diverse approaches and interests? The paper concludes with a clear strategy: a set of instructions geared towards building successful interdisciplinary collaborations. Ultimately, we conclude that a strong relationship amongst scientists and artists is possible, fruitful, and indeed warranted when shared goals are the driving principle of the group.