路肩のプラスチック片堆積状況に対する近傍の発生源及び累積降雨量の影響

抄録

We investigated the side of parking lots, garbage collection points and house wall to understand the source of plastic pieces. The survey was conducted approximately monthly from Apr. 2020 to Feb. 2021 with the aim of clarifying detailed rainfall variation in the density of plastic pieces on the shoulder. The discharge coefficient of gravel is 0.30 to 0.70, lower than that of asphalt, 0.70 to 0.95. As the plastic pieces on the gravel surface could be hard to be washed away and easy to be accumulated, the mass of plastic pieces flowing into the side was larger than that flowing out. PE, PP, PS, PET and PVC were predominant among the found polymer materials (43-66%by mass). The size corresponding to the cumulative ratio of 50% the plastic pieces on the side of house wall was smaller than that on the others. On the sides of house wall that was not near the plastic source, the plastic pieces could be weathered to fragment into smaller pieces than on the others. The number density of plastic pieces scattered on the side of garbage collection point was affected by the structure. It was found that the behavior of plastic load was complicatedly influenced by land properties, uses and rainfall.