Distribution and ecological risks of microplastics in a tropical tourism island area in Hainan, China

Microplastics are a widely distributed pollutant that threatens the growth and health of marine organisms. Compared to the mainland, island ecosystems with unique characteristics are fragile and sensitive to natural and human interference. We investigated the characteristics and ecological risks of microplastics in the soils of Wuzhizhou Island, Hainan, China, and its surrounding nearshore sediments affected by human activities. Results show that the microplastic abundance in soil was 1 116.67 items/kg; the particles were fragmented in size of less than 2 mm, the main polymer types were polypropylene (PP), polyethylene (PE), and polybutylene (PB), in transparent, gray, green, or white. The microplastic abundances in nearshore sediments of Wuzhizhou Island and the surrounding Haitang Bay were 274.67 and 755.17 items/kg, respectively; the particles were mainly fibrous, less than 1 mm in size, the main polymer types were rayon and polyethylene terephthalate (PET), mostly transparent. The abundance of microplastics showed a decreasing trend from shore to sea. Microplastics in the supratidal and intertidal zones differed in mainly the abundance and size. The microplastics in land soil were from tourism activities and infrastructure while the those in nearshore sediments came from not only tourism but also domestic sewage and fishing activities. The ecological risk of microplastics in the terrestrial soils of Wuzhizhou Island was higher than that in its surrounding nearshore sediments. These findings help to gain a deeper understanding of microplastic pollution in the island subjected to intensive human activities, and provide a scientific basis for subsequent in-situ toxicology research on microplastics and plastic pollution control.