Quantification and characterization of plastics in near-shore surface waters of Atlantic Canada.

Plastics are a ubiquitous pollutant in the marine environment. Despite growing concerns, quantitative and qualitative data on microplastics in aquatic and marine environments of Atlantic Canada is just emerging. Surface water plastics were measured and categorized by morphology (thread, microfibre, fragment, foam, film, pellet, and microbead) in two locations in Nova Scotia and one in Newfoundland and Labrador, Canada. All sites within the three locations contained plastic with an average abundance of 9669 items/km2. Most plastics (68 %) were sized as microplastics (0.425-5 mm), and plastic fragments were the most common morphological type. Polyethylene accounted for a third (30 %) of all particles found across all three locations, followed by polypropylene (23 %). Results can inform future research for community-based environmental groups, government, and academia.

The Impact of Free Radical Stabilization Techniques on in vivo Mechanical Changes in Highly Cross-Linked Polyethylene Acetabular Liners.

INTRODUCTION: Numerous thermal free radical stabilization techniques are used in the production of highly cross-linked polyethylene (HXLPE) to improve oxidative stability. Little knowledge exists on the effects of in vivo time on the mechanical properties of HXLPE. The purpose of this study was to determine if free radical stabilization of HXLPE impacts mechanical properties as well as oxidative stability of acetabular liner rims after extended in vivo time. METHODS: Retrieved and control remelted, single annealed and sequentially annealed HXLPE liner rims were tested for mechanical properties. Oxidation was measured with FTIR spectroscopy and crystalline phase composition measured with Raman spectroscopy. RESULTS: No correlation was found between in vivo, ex vivo time and hardness for annealed groups. A statistically significant difference in hardness was identified between free radical stabilization groups. No correlation between maximum rim oxidation and in vivo time was found. Detectable levels of rim oxidation were present in 100% of single annealed, 75% of sequentially annealed, and 25% of remelted retrieved liners. Single and sequentially annealed liners demonstrated oxidation and increased crystallinity. Rim mechanical properties change in vivo for implant types. With in vivo time, retrieved remelted HXLPE demonstrated decreased mechanical properties, whereas retrieved single and sequentially annealed HXLPE properties remained stable. All liner cohorts demonstrated evidence of rim oxidation. Subsequent changes in crystallinity were only observed in oxidized annealed liners. CONCLUSION: HXLPE acetabular liner rims show evidence of in vivo mechanical property degradation, notably in remelted HXLPE, which may be a risk factor in rim fracture and catastrophic implant failure.

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.

Hidden plastics of Lake Ontario, Canada and their potential preservation in the sediment record.

Microplastics are a source of environmental pollution resulting from degradation of plastic products and spillage of resin pellets. We report the amounts of microplastics from various sites of Lake Ontario and evaluate their potential for preservation in the sediment record. A total of 4635 pellets were sampled from the Humber Bay shoreline on three sampling dates. Pellet colours were similar to those from the Humber River bank, suggesting that the river is a pathway for plastics transport into Lake Ontario. Once in the lake, high density microplastics, including mineral-polyethylene and mineral-polypropylene mixtures, sink to the bottom. The minerals may be fillers that were combined with plastics during production, or may have adsorbed to the surfaces of the polymers in the water column or on the lake bottom. Based on sediment depths and accumulation rates, microplastics have accumulated in the offshore region for less than 38 years. Their burial increases the chance of microplastics preservation. Shoreline pellets may not be preserved because they are mingled with organic debris that is reworked during storm events.