Microplastic pollution in an urbanized river affected by water diversion: Combining with active biomonitoring

Microplastics as the most challenging environmental pollutants in ocean have raised increasing concerns, however, the understanding of microplastics in freshwater falls far behind. The main objective of this study is to assess the microplastic pollution in an urbanized river affected by water diversion. The active biomonitoring method with caged native crucian carp (Carassius auratus) was used to evaluate the microplastic risk for riverine fish. It found that microplastic abundance in water and sediment was 1467–20567 items/m³ and 1115–6380 items/kg, respectively. The operational water diversion did not alleviate the microplastic pollution in water. The abundance in sediment was not simply proportional to that in water. However, the main morphological profiles and polymer composition were similar in the water and sediment. Microplastic accumulation in caged fish intestine was higher than that in gill. Intestine seems to be an ideal tissue to reflect the microplastic pollution in water. Shapes may contribute to the accumulation in fish. Based on the pollution load index, all caged fish did not reach to high level risks. These findings not only improve the understanding on the impact of water diversion on microplastic pollution in urban river, but also shed an insight in the related risk for riverine fish. [Display omitted] •Active biomonitoring with caged fish is useful to assess microplastic pollution in river.•Water diversion did not alleviate the microplastic pollution in river.•The intestine may be an ideal tissue to reflect the microplastic pollution in water.•The shape of microplastics may contribute to the accumulation in caged fish.•Microplastic pollution did not pose high risks for riverine fish.