[M-IS09] Ocean Plastics, an earth science perspective

[MIS09-06] Determination of the polyethylene terephthalate microplastics (PET-MPs) in the sediments of the Seto Inland Sea

Furura Shino², Takahshi Nobuhiro¹, Hirashima Soichiro¹, Yoko Iwamoto¹, *Takeda Kazuhiko¹ (1.Graduate School of Integrated Sciences for Life, Hiroshima University, 2.Faculty of Integrated Arts and Sciences, Hiroshima University)

Keywords:polyethylene terephthalate, microplastics , Seto Inland Sea, sediments

Plastics are rapidly becoming important participants in marine environments. Some plastic debris is washed up on coastal areas, transforming beautiful coastlines into undesirable debris storage. Plastic debris released into coastal marine environments floats and drifts at the sea surface, and is slowly physically, chemically, and biologically destroyed into small plastic pieces less than 5 mm, "microplastics (MPs)". These pieces sink to the ocean floor or drift at the water surface depending upon their densities. MPs are quantified mainly by counting under the microscope after complicated pre-separation by skillful operator. Unfortunately, they might have chance to lead unexpected errors. In this study, we determined the whole amount of polyethylene terephthalate microplastics (PET-MPs) in the sediments using depolymerization method. PET is an important plastic for food containers, drink bottles and polyester fibers. The PET released into the ocean is broken into small pieces and scraps of PET and sinks to the ocean floor due to their densities (1.37–1.41 g/cm³). In this study, PET-MPs were determined using the alkali-assisted thermal hydrolysis method, in which PET was depolymerized to terephthalate (TPA), and TPA from PET was determined using a hydrophilic interaction liquid chromatography (HILIC). Marine sediments were taken from the Seto Inland Sea using the Smith-Mcintyre grab sampler.
Recovery test was conducted using the high-purity-PET spiked marine sediments, and good-enough recoveries were obtained. Concentrations of PET-MPs in the sediments of the Seto Inland Sea were estimated to be 0.04~2.58 µg/g-DW. They were high in Osaka Bay and Hiroshima Bay, which are the typical semi-enclosed sea areas facing some large urban areas. In this presentation, we will present the results of the optimization of the methods and the total deposition of PET-MPs in the Seto Inland Sea.