While plastic pollution in marine and freshwater systems is an active area of research, there is not yet an in-depth understanding of the distributions, chemical compositions, and fates of plastics in aquatic environments. In this study, the magnitude, distribution, and common polymers of microplastic pollution in surface waters in western Lake Superior are determined. Analytical methodology, including estimates of ambient contamination during sample collection and processing, are described and employed. Microscopy, pyrolysis-gas chromatography/mass spectrometry (Pyr-GC/MS), and Fourier transform infrared spectroscopy (FTIR) were used to quantify and identify microplastic particles. In surface waters, fibers were the most frequently observed morphology, and, based upon PyGC/MS analysis, polyvinyl chloride was the most frequently observed polymer, followed by polypropylene and polyethylene. The most common polymer identified by FTIR was polyethylene. Despite the low human population in Lake Superior's watershed, microplastic particles (particularly fibers, fragments, and films) were identified in western-lake surface waters at levels comparable to average values reported in studies within Lake Michigan, the North Atlantic Ocean, and the South Pacific Ocean. This study provides insight into the magnitude of microplastic pollution in western Lake Superior, and describes in detail methodology to improve future microplastics studies in aquatic systems.
Bibliographical noteFunding Information:
We thank Sarah Grosshuesch, Julia Halbur, Noah Holden, and Roselynd Lin from the Large Lakes Observatory, University of Minnesota Duluth for analytical assistance, Melissa Maurer-Jones and John Evans of the Department of Chemistry and Biochemistry, University of Minnesota Duluth for comments on an early version of this manuscript, and the captain and crew of the R/V Blue Heron and the captain of the R/V Kingfisher for sampling assistance. ECM would like to acknowledge funding from the University of Minnesota Office of the Vice President for Research, Grant-in-Aid of Research, Artistry & Scholarship Program. K.M.S. acknowledges funding from the University of Minnesota Duluth EVCAA Research and Scholarship Grants Program.
© 2018 American Chemical Society.