The spatial distribution and composition of microplastics in Placentia Bay, Newfoundland and Labrador

Abstract

As part of a baseline study for Placentia Bay, one of Newfoundland's prominent fishing regions, I investigated the spatial distribution and characteristics of microplastics. I collected water samples from the surface at nine open-water locations and sediment samples at six locations in the sediment layer. Microplastics were examined under a microscope, and a subset of samples underwent Raman microspectroscopy for chemical identification To tailor methods specifically to the water and sediment samples from Placentia Bay, I conducted method tests. Published methods proved unreliable, as a lack of standardized methodology was evident. Water column samples required an extended digestion time of 24 hours with hydrogen peroxide and acetic acid due to their POC-rich nature. In sediment samples, microplastics were isolated using a sodium tungstate dihydrate solution. . The highest concentrations of microplastics in the water column were identified on the eastern side of the bay, with fibers being the predominant shape and polyethylene as the dominant polymer type. Raman spectroscopy was employed to confirm microplastics and evaluate the reliability of visual identification. 50% of fragments and 21% of fibers were non-plastic, highlighting the limitations of relying solely on visual identification for characterizing microplastics.