Prevalence of microplastic pollution in the Northwestern Pacific Ocean.

People are increasingly aware of ubiquitous microplastic (MP) pollution in the world's ocean due to its far-reaching harmful impacts on marine ecosystem and potential hazards to human health, yet surprisingly comparatively limited studies about the abundance, source, transport, and fate of MPs in the Northwestern Pacific Ocean are available. We conducted the field survey of MPs pollution at the surface of the Northwestern Pacific Ocean between August 25 and September 26, 2017. MPs were collected from 18 sampling stations in the Northwestern Pacific Ocean using a manta trawl net with a mesh size of ∼330 µm and a rectangular net opening of 0.45 × 1 m. The abundance, shape, color, size, chemical composition, and surface morphology were characterized using light microscopy, µ-Raman spectroscopy, and scanning electron microscopy (SEM). The results show surface MPs at concentrations ranging over two orders of magnitude (6.4 × 102 to 4.2 × 104 particles km-2) and a mean abundance of 1.0 × 104 particles km-2. The most concentrated MPs were found at XTJ3-9, which may be associated with the convergence of surface currents collectively affected by the Kuroshio and its extension, adjacent eddies, and flow regimes. Polyethylene accounts for 57.8% of enumerated MPs, followed by polypropylene (36.0%) and nylon (3.4%). Pellets, sheets, lines, and films are major forms which may be linked to the breakdown of larger particles, aging processes, and movement over long distances by prevailing currents. Four possible MPs migration pathways were proposed based on the source-specific distribution, chemical fingerprints, size distribution patterns, and the observed physical oceanographic parameters.

Microplastics in the Northwestern Pacific: Abundance, distribution, and characteristics.

Prevalence of microplastics (MPs) throughout the world's oceans has raised growing concerns due to its detrimental effects on the environment and living organisms. Most recent studies of MPs, however, have focused on the estuaries and coastal regions. There is a lack of study of MPs pollution in the open ocean. In the present study, we conducted field observations to investigate the abundance, spatial distribution, and characteristics (composite, size, color, shape and surface morphology) of MPs at the surface of the Northwestern Pacific Ocean. Samples of MPs were collected at 18 field stations in the Northwestern Pacific Ocean using a surface manta trawl with a mesh size of ~330 µm and width of 1 m from August 25 to September 26, 2017. The MPs were characterized using light microscopy, Micro-Raman spectroscopy, and scanning electron microscopy (SEM). Our field survey results indicate the ubiquity of MPs at all stations with an abundance from 6.4 × 102 items km-2 to 4.2 × 104 items km-2 and an average abundance of 1.0 × 104 items km-2. The Micro-Raman spectroscopic analysis of the MPs samples collected during our field survey indicates that the dominant MPs is polyethylene (57.8%), followed by polypropylene (36.0%) and nylon (3.4%). The individual chemical compositions of MPs from the stations within the latitude range 123-146°E are comparable with each other, with PE being the dominating composition. Similar chemical fingerprints were observed at these field stations, suggesting that the MPs originated from similar sources. In contrast, the major MPs at the field stations adjacent to Japan is polypropylene, which may originate from the nearby land along the coast of Japan. Physical oceanography parameters were also collected at these stations. The spatial distribution of MPs is largely attributed to the combined effects of flow pattern, adjacent ocean circulation eddies, the Kuroshio and Kuroshio Extension system.