Abundance and distribution of microplastics on sandy beaches of remote islands of Okinawa, southern Japan

Abstract

Microplastic levels of remote islands and regions often receive less attention than levels in urban and more accessible areas. This study investigated the abundance and typology of microplastics on beach sediments of four remote islands (Iriomote, Aka, Sesoko, Kouri) in Okinawa in southern Japan. Overall, microplastic concentrations in beach sediments in these remote islands ranged from 116.67 ± 0.75 particles/kg sediment to 522.22 ± 157.62 particles/kg across the islands. Concentrations at six beaches around Iriomote Island ranged from 213.33 ± 100.10 to 446.67 ± 267.39 particles/kg sediment, while concentrations in four Aka Island beach sediments were from 240.80 ± 88.88 to 522.22 ± 157.62 particles/kg. Concentrations in beach sediments of Sesoko and Kouri islands were 300 ± 41.23 and 116.67 ± 15.06 particles/kg sediments, respectively. Microplastic morphology and polymers detected with Raman spectroscopy were dominated by fibers and polyethylene, respectively, while the most abundant size was < 1 mm microplastic at all beaches. Pollution indices revealed a low level of microplastic pollution on these sandy beaches, providing baseline data for future assessments of microplastic pollution in other sandy beaches around remote islands in the East China Sea. We recommend migration to washing machines with filters, as well as adequate management of solid wastes in municipalities and harbours in order to reduce microplastic pollution of coastal areas in remote islands.