Occurrence and characterization of microplastic content in the digestive system of riverine fishes

In the present study, the occurrence and characterization of microplastics (MPs) content in the fishes of the river was studied. Therefore, six sampling stations were considered for fishing. Then, the entire stomach of fishes was investigated by visual stereomicroscope, FTIR, SEM, and EDX to analyze the content of the samples, by MPs type, shape, color, and size. The most frequency of MPs was observed in Ghazanchi (S_iii) and Kermanshah (S_iv) stations which were close to urban and industrial areas. Most types of detected MPs included polystyrene, polyethylene, and nylon with the highest frequency observed in Luciobarbus caspius and Alburnus chalcoides fishes. Overall, the frequency of detected MPs in the caught fishes was 93.8%. Indeed, MPs with a size of 0.025-1 mm (25-1000 μm) were the most frequency of MPs in fishes. The frequency of MPs shapes was fiber (85.12%), fragment (12.32%), foam (0.77%), film (1.21%), and microbead (0.56%), respectively. The highest and lowest percentage of MPs belonged to black and green with an abundance of 63% and 2%, respectively. The result implies that lots of riverine fishes are polluted with MPs, those which can move into the food chain.