Microplastics in water, sediment and fish from the Fengshan River system: Relationship to aquatic factors and accumulation of polycyclic aromatic hydrocarbons by fish

The occurrence of microplastics was investigated in water, sediment and fish from the Fengshan River system. All collected samples contained microplastics with 334–1058 items/m³ in the water samples, 508-3987 items/kg dry weight in the sediment samples and 14–94 items/fish in the fish samples. The spatial distribution of microplastics in water and sediments was attributed to anthropogenic discharges, flow dynamics, tidal exchanges and microplastic density. This was evidenced by significant correlations of microplastics with the river pollution index (RPI), chemical oxygen demand (COD), suspended solid (SS), flow velocity and the presence of different polymer types of microplastics in water and sediment. Microplastic abundance in fish was correlated to SS, pH and conductivity, indicating that these water quality variables might affect bioavailability of microplastics to fish. Concentrations of microplastics/cm length of demersal fish at a higher trophic level (Leiognathus equulus and Pomadasys argenteus) were higher than those of a benthopelagic fish (Oreochromis niloticus niloticus). The significant relationships observed suggest that collected fish might prefer to ingest long fibrous microplastics from sediments and large fragmented microplastics from water. The high levels of 3- and 4-ring polycyclic aromatic hydrocarbons (PAHs), particularly fluoranthene and pyrene, in fish muscle revealed that the collected fish species might have a high ability to accumulate these PAHs from food and the environment. Significant relationships between some PAHs in fish and microplastic abundances in water/sediments/fish suggested that these PAHs might be accumulated by fish from contaminated microplastics. This study provides unique information on the factors influencing the spatial distribution of microplastics and the role of microplastics on the accumulation of PAHs by fish.