Occurrence, sources, transport, and fate of microplastics in the great lakes–st. lawrence river basin

Abstract

Microplastics, plastic particles less than five millimeters in size, are found in each of the five Laurentian Great Lakes, their tributary streams and rivers, and the St. Lawrence River carrying Great Lakes water to the Atlantic Ocean. Although standardized methodologies and reporting criteria are needed as varying size groupings, particle character categories, and reporting units have been used in Great Lakes studies, a picture of microplastic pollution across the lakes is emerging. Greater abundances of microplastics are found near urban centers where rivers and municipal wastewater deliver plastics to the lakes, with fragments of plastic and fibers/lines generally the dominant particle types found, depending on locations sampled. Microplastic morphologies, the shape and character of plastic particles, provide source-specific information and indicate contributions of microplastics to beaches, lake and river waters, and sediment from industries (pellets, deflashing material, etc.), microbeads from personal care products, fragments and film from litter and debris (single-use plastics, bags, and food wrappers), and foam (insulation board, consumer packaging, and take-out containers). The relative roles of stormwater run-off (directly and through streams) compared to wastewater effluents in delivering microplastics to the Great Lakes are not known, but both are expected to be major pathways. Sediments are a major repository of microplastics, and high abundances were found in the Great Lakes region near major urban centers, especially where there are greater numbers of plastic sector businesses in adjacent watersheds. Few studies have examined the occurrence and uptake of plastics in biota from the Great Lakes, and further research is needed to determine the levels of exposure and potential for harm in both aquatic and terrestrial organisms, given the levels and types of microplastics present in the Great Lakes environment.