Occurrence and characteristics of microplastics in surface road dust in Kusatsu (Japan), Da Nang (Vietnam), and Kathmandu (Nepal)

Satoru Yukioka; Shuhei Tanaka; Yoshiki Nabetani; Yuji Suzuki; Taishi Ushijima; Shigeo Fujii; Hideshige Takada; Quang Van Tran; Sangeeta Singh

doi:10.1016/j.envpol.2019.113447

Occurrence and characteristics of microplastics in surface road dust in Kusatsu (Japan), Da Nang (Vietnam), and Kathmandu (Nepal)

Environ Pollut. 2020 Jan:256:113447. doi: 10.1016/j.envpol.2019.113447. Epub 2019 Oct 25.

Authors

Satoru Yukioka¹, Shuhei Tanaka², Yoshiki Nabetani³, Yuji Suzuki⁴, Taishi Ushijima³, Shigeo Fujii², Hideshige Takada⁵, Quang Van Tran⁶, Sangeeta Singh⁷

Affiliations

¹ Graduate School of Global Environmental Studies, Kyoto University, Yoshida, Sakyo-Ku, Kyoto, Japan. Electronic address: yukioka@eden.env.kyoto-u.ac.jp.
² Graduate School of Global Environmental Studies, Kyoto University, Yoshida, Sakyo-Ku, Kyoto, Japan.
³ Graduate School of Engineering, Kyoto University, Yoshida, Sakyo-Ku, Kyoto, Japan.
⁴ Public Works Research Institute, Minamihara, Tsukuba-city, Ibaraki, Japan.
⁵ Laboratory of Organic Geochemistry (LOG), Tokyo University of Agriculture and Technology, Fuchu, Tokyo, Japan.
⁶ Faculty of Environment, Da Nang University of Science and Technology, Nguyen Luong Bang St, Da Nang, Viet Nam.
⁷ Institute of Engineering, Tribhuvan University, Kirtipur, Kathmandu, Nepal.

PMID: 31679875
DOI: 10.1016/j.envpol.2019.113447

Abstract

Microplastics (MPs, plastics < 5 mm) are a growing concern in ecosystems, being found in the soil and water environment. One of the primary sources of MPs has been suspected to be road dust in urban areas as it can flow into waters with runoff. To understand the occurrence of MPs (100 μm-5 mm) in surface road dust of three cities (Kusatsu, Shiga, Japan; Da Nang, Vietnam; and Kathmandu, Nepal), we collected surface road dust samples. The samples were pretreated (organic matter decomposition and gravity separation), and all MP candidates were individually observed by microscope for color, shape, and size; and analyzed their polymer types using fourier transform infrared spectrometry. The abundances of MPs 100 μm to 5 mm in size were 2.0 ± 1.6 pieces/m² (13 polymer types) in Kusatsu, 19.7 ± 13.7 pieces/m² in Da Nang (14 types), and 12.5 ± 10.1 pieces/m² in Kathmandu (15 types). We classified the MPs into two groups; containers/packaging-MPs and rubber-MPs. Among all MPs, the containers/packaging-MPs accounted for 55 ± 5% of the polymer types composition. In contrast, the rubber-MPs accounted for 16 ± 6% of all MPs which were higher than those previously published for environmental water and sediment samples. The containers/packaging-MPs were fragments of various colors while most of the rubber-MPs were fragments or granules in black. The number-size distributions of MPs showed that the mode of formation explains the differences between their polymer types (tearing for containers/packaging-MPs and abrasion for rubber-MPs). In Da Nang and Kathmandu, the abundance of containers/packaging-MPs and rubber-MPs were correlated so that those MPs might be micronized from the originated materials in the sources with the similar composition (e.g. dump points). It was indicated that the characteristics of MPs pollution in surface road dust might be different depending on waste management practices.

Keywords: Containers/packaging-MP; Microplastic (MP); Rubber-MP; Surface road dust; Urban area.

MeSH terms

Cities
Dust / analysis*
Ecosystem
Environmental Monitoring*
Environmental Pollution / analysis
Environmental Pollution / statistics & numerical data*
Japan
Microplastics / analysis*
Nepal
Plastics / analysis
Rubber
Vietnam

Substances

Dust
Microplastics
Plastics
Rubber