Suzuki, Hayato; Abeynayaka, Amila; Fukunaga, Yuu; Kojima, Fujio; Itsubo, Norihiro

Mismanaged plastics from land-based sources create environmental issues. These plastics could eventually end up in the ocean, degrading the marine environment and affecting living organisms. In recent years, microplastics (MP), which are smaller than 5 mm in diameter, have been found in the environment and may have a negative impact on ecosystems due to the plastic taken into living organisms. According to a survey of MP collection conducted by PIRIKA Corporation at more than 100 rivers and harbors in Japan during 2018-2019, capsules of controlled-release fertilizers (CRF) was the second most common single microplastic identified. CRF, which are made by covering the fertilizer with a thin film of plastic, are most commonly used in rice farming in Japan. The research on plastic agriculture related plastic pollution covers various fields such as the distribution and fate of plastics in the oceans and the effects of adsorbed chemical substances on the ecosystem. However, most of the research is on MPs in the oceans and coastal areas, and there are few studies on in Japanese water environments on MP runoff. Moreover, very few studies on plastic litter derived from agriculture sector. In the evaluation of the environmental impact of rice farming, there are many studies on greenhouse gas emissions and eutrophication due to fertilizer content. Yet there are few studies that consider plastic pollution such as CRF. This study focused on the measurement of CRF in Japanese river. This result is expected to be a fundamental data of plastic pollution in rice farming. Rice is the staple food of Asia, and the assessment of paddy rice is necessary to prevent environmental impact in the future. Likewise, it is important to address the problem of plastic runoff into the ocean. The results of this study will be useful for the prevention of agricultural plastic emissions and the promotion of appropriate treatment.