Comparative Analysis of Plastic Pieces in Basin, River and Coast: Case Study in the Hikiji River Basin, Kanagawa Prefecture

Research on plastic debris in the ocean and rivers is being vigorously conducted, but there is little research on the dynamics of plastic from the basin, which is one of the sources of plastic waste, to rivers and coasts. In this study, we conducted a field survey of basins （ roads ）, rivers, and coasts in the Hikichi River basin, Kanagawa Prefecture, with the aim of clarifying the dynamics of plastic pieces in the basin, river, and coast. From the results of the sample particle recovery test, the target size of the plastic piece in this study was set to be > 1 mm. The results indicated that the numerical and mass concentration of plastic pieces in the road dust between districts considered were significantly higher in the commercial and residential areas, respectively, mainly because of the difference in plastic piece size distribution. A comparison of plastic materials on roads, rivers, and coasts showed that polyethylene （ PE ）, polypropylene （ PP ）, and polystyrene （ PS ）, which have low specific gravity, were predominant in the river and materials washed up on the coast, but not significant in the road dust.