Microplastics in Sediment Cores from Asia and Africa as Indicators of Temporal Trends in Plastic Pollution

Microplastics (<5 mm) were extracted from sediment cores collected in Japan, Thailand, Malaysia, and South Africa by density separation after hydrogen peroxide treatment to remove biofilms were and identified using FTIR. Carbonyl and vinyl indices were used to avoid counting biopolymers as plastics. Microplastics composed of variety of polymers, including polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethyleneterphthalates (PET), polyethylene-polypropylene copolymer (PEP), and polyacrylates (PAK), were identified in the sediment. We measured microplastics between 315 µm and 5 mm, most of which were in the range 315 µm–1 mm. The abundance of microplastics in surface sediment varied from 100 pieces/kg-dry sediment in a core collected in the Gulf of Thailand to 1900 pieces/kg-dry sediment in a core collected in a canal in Tokyo Bay. A far higher stock of PE and PP composed microplastics in sediment compared with surface water samples collected in a canal in Tokyo Bay suggests that sediment is an important sink for microplastics. In dated sediment cores from Japan, microplastic pollution started in 1950s, and their abundance increased markedly toward the surface layer (i.e., 2000s). In all sediment cores from Japan, Thailand, Malaysia, and South Africa, the abundance of microplastics increased toward the surface, suggesting the global occurrence of and an increase in microplastic pollution over time.

Yukari Matsuguma, Hideshige Takada, Hidetoshi Kumata and al., Archives of Environmental Contamination and Toxicology, pp 1–10, Special Issue: Indicators of Ocean Pollution, First Online 22 May 2017

The article

Fate of microplastics and mesoplastics carried by surface currents and wind waves: A numerical model approach in the Sea of Japan

A numerical model was established to reproduce the oceanic transport processes of microplastics and mesoplastics in the Sea of Japan. A particle tracking model, where surface ocean currents were given by a combination of a reanalysis ocean current product and Stokes drift computed separately by a wave model, simulated particle movement. The model results corresponded with the field survey. Modeled results indicated the micro- and mesoplastics are moved northeastward by the Tsushima Current. Subsequently, Stokes drift selectively moves mesoplastics during winter toward the Japanese coast, resulting in increased contributions of mesoplastics south of 39°N. Additionally, Stokes drift also transports micro- and mesoplastics out to the sea area south of the subpolar front where the northeastward Tsushima Current carries them into the open ocean via the Tsugaru and Soya straits. Average transit time of modeled particles in the Sea of Japan is drastically reduced when including Stokes drift in the model.

Shinsuke Iwasaki, Atsuhiko Isobe, Shin’ichiro Kako, Keiichi Uchida, Tadashi Tokai, Marine Pollution Bulletin, Available online 27 May 2017, In Press

The article

Percentage of microbeads in pelagic microplastics within Japanese coastal waters

To compare the quantity of microbeads with the quantity of pelagic microplastics potentially degraded in the marine environment, samples were collected in coastal waters of Japan using neuston nets. Pelagic spherical microbeads were collected in the size range below 0.8 mm at 9 of the 26 stations surveyed. The number of pelagic microbeads smaller than 0.8 mm accounted for 9.7% of all microplastics collected at these 9 stations. This relatively large percentage results from a decrease in the abundance of microplastics smaller than 0.8 mm in the upper ocean, as well as the regular loading of new microbeads from land areas, in this size range. In general, microbeads in personal care and cosmetic products are not always spherical, but rather are often a variety of irregular shapes. It is thus likely that this percentage is a conservative estimate, because of the irregular shapes of the remaining pelagic microbeads.

Atsuhiko Isobe, Marine Pollution Bulletin, Volume 110, Issue 1, 15 September 2016, Pages 432–437

The article

Microplastic litter found in digestive systems of Tokyo Bay fish

Nearly 80% of Japanese anchovy caught in a survey of Tokyo Bay had plastic waste inside their digestive systems, according to the research team who conducted the study.

Eating the fish is unlikely to cause major health problems, but the finding indicates worrying levels of pollution in the sea around Japan, according to the group led by Professor Hideshige Takada of the Tokyo University of Agriculture and Technology.

The team examined 64 Japanese anchovies caught in the bay in August last year and found 150 microplastic particles, or plastic pieces up to 5 millimeters, in the digestive tubes of 49 of them.

Of the 150 plastic pieces, about 80 percent were 0.1 to 1 millimeter in size, the team said. (…) (japantoday.com, 10/04/2016)

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