Microplastics (MPs), with a diameter of less than 5 mm, are of growing concern because of their enormous amounts and widespread existence in the rivers, beaches and oceans globally. MPs, a likely source of toxic chemicals added as ingredients during plastic manufacturing, could be ingested easily and thus potentially act as multiple stressors to the organisms. MPs also prone to adsorb various hydrophobic organic contaminants (HOCs), such as polycyclic aromatic hydrocarbons (PAHs), which can be introduced to the marine environment by land runoff or air transport and have toxic, mutagenic and carcinogenic potentials. Therefore, it is of great significance to study MPs associated with PAHs, and to further investigate the role of MPs as vectors for HOCs transfer in the environments.

Xiamen’s surrounding sea and Jiulong River Estuary are bound by the southeast of Mainland China and the Taiwan Strait. As one of the first “special economic zones”, Xiamen has experienced an extensive urban expansion at the cost of coastal environmental degradation. Rapid population growth and intense human activities have led to high huge pollutant emission. To assess the discharge of MPs and PAHs from the coast to the ocean, and explore the impact of urbanization and industrialization on marine environments, surface water and sediments sampling was conducted in the Xiamen Bay and Jiulong River Estuary, China in March 2017. MPs from water were collected by a manta net for tows, and their chemical compositions were identified by Fourier transform infrared spectroscopy (FTIR) and FTIR microscope system.

Our results showed that surface water near the sewage contained highest abundance of microplastics, suggesting a direct domestic input of MPs such as cosmetic beads and clothing fibers that pass through waste water treatment to the marine environment. The shapes of MPs were dominated by fragments, lines, fibers and pellets, which were mainly identified as polyethylene and polypropylene. Different physicochemical characteristics of MPs from sediments and surface waters were likely to be related to the surrounding industries. The spatial distribution pattern of PAHs was generally similar to that of MPs, indicating the influence of anthropogenic discharge. Attention should be paid to high levels and their risks of MPs existing in Xiamen coast, and their further control.