Microplastics are detected everywhere even in the tropical forest areas. Many investigations of microplastics in the marine environmen are done by researchers and they found some negative effects on the environment. However, those in the fresh water one such as river are rarely done. Moreover, to investigate the effect of microplastics is done under the 10% microplastic contained soil. This is the unrealistic value due to plastics are light and easy to flow away.
This research focuses on finding how much plastics are contained in the soil in the bottom of Nogawa river. Nogawa is 20.8 km length river in Mitaka, Tokyo and the plants’ revetment are installed in most of the place. I collected soil samples from 4 different places, Futako-Tamagawa, Irumagawa, Otozakabashi, and Nimaibashi and record the surroundings with sampling. Plastics are separated using the difference of specific gravity and weighed by precision balance. The concentration of plastics at each spot is 0.0022g/gsoil at Futako-Tamagawa, 0.0011g/gsoil at Iruma-gawa, 0.0034g/gsoil at Otozaka-bashi, and no plastics at Nimai-bashi. The percentage of contained plastics in soil is up to 0.34%. Moreover, to compare the plastic’s concentration and surroundings, the plants’ revetment may increase the plastic concentration due to the sticky mud.