17:15 〜 19:15
[MIS21-P05] 市民科学を用いた廃プラ等の水域流入量の推定
キーワード：定量モデル、海洋プラスチック、散乱ごみ、流入経路
Objective
OECD estimates indicate that the amount of plastic waste leaking into the environment worldwide in 2019 will double to 44 million tons per year in 2060 [1]. Most marine plastic waste is known to be domestic waste that has flowed into the ocean through rivers from cities owing to improper management [2]. In Japan, 70-80% of marine waste flows out into the ocean through rivers; however much of the causes and mechanisms of outflow remain unknown [3]. Therefore, even globally, no method has been established for quantifying city plastic waste based on objective and efficient observation.
To that end, in this study, we first developed a model for quantifying the flow of waste plastic from land to water areas in collaboration with the Sustainable System Design Institute. Subsequently, we utilized citizen science through a smartphone app (Pirika) in collaboration with the Foundation for Environmental Rehabilitation and Redevelopment of Mizushima to analyze city waste images and measure the amount of inflow of city plastic waste into water bodies.
Measurement method
The equations for the material balance at a certain location L is that the inflow Q for a certain period t is obtained by the summation of inflow to waterfront (InB) and direct inflow (InW) for that period, followed by the subtraction of the amount cleaned up in the river and the increase in S left behind at the waterfront. The total inflow in that water area can be calculated by the summation of Q for the entire waterfront. In particular, if InBL and InW(L) (InW)(L) in a given location L, as well as the amount of waste plastic cleaned up are known, the total outflow can be estimated. Furthermore, InB, InW, and the amount of waste plastic cleaned up can be estimated by adding up their total values for the entire waterfront.
Measurements were conducted on waterways around Kurashiki Kojoike (circumference of 2.2 km), with the cooperation of the Foundation for Environmental Rehabilitation and Redevelopment of Mizushima.
Discussion of results
The total outflow can be estimated if the InB(L), InW(L), and amount of waste plastic cleaned up at a certain location L are known from the quantification model. City waste images were analyzed, and the outflow of city plastic waste into water areas was measured. The data from the third measurement after the clean up event were generally less than the difference data between the first and second measurements, which confirmed the effectiveness of waste collection events according to the broken window theory.
References
[1] OECD (2022), Global Plastics Outlook: Economic Drivers, Environmental Impacts and Policy Options, OECD Publishing, Paris. https://doi.org/10.1787/de747aef-en. (Accessed 15 Februay 2025)
[2] Lebreton, L., van der Zwet, J., Damsteeg, J.W. et al. (2017), “River plastic emissions to the world’s oceans.” Nat Commun 8, 15611. https://doi.org/10.1038/ncomms15611 (Accessed 15 Februay 2025)
[3] Nippon Foundation Journal (2020), “Continuously increasing ocean waste.” https://www.nippon-foundation.or.jp/journal/2020/46494/ocean_pollution/ (Accessed 15 Februay 2025)
OECD estimates indicate that the amount of plastic waste leaking into the environment worldwide in 2019 will double to 44 million tons per year in 2060 [1]. Most marine plastic waste is known to be domestic waste that has flowed into the ocean through rivers from cities owing to improper management [2]. In Japan, 70-80% of marine waste flows out into the ocean through rivers; however much of the causes and mechanisms of outflow remain unknown [3]. Therefore, even globally, no method has been established for quantifying city plastic waste based on objective and efficient observation.
To that end, in this study, we first developed a model for quantifying the flow of waste plastic from land to water areas in collaboration with the Sustainable System Design Institute. Subsequently, we utilized citizen science through a smartphone app (Pirika) in collaboration with the Foundation for Environmental Rehabilitation and Redevelopment of Mizushima to analyze city waste images and measure the amount of inflow of city plastic waste into water bodies.
Measurement method
The equations for the material balance at a certain location L is that the inflow Q for a certain period t is obtained by the summation of inflow to waterfront (InB) and direct inflow (InW) for that period, followed by the subtraction of the amount cleaned up in the river and the increase in S left behind at the waterfront. The total inflow in that water area can be calculated by the summation of Q for the entire waterfront. In particular, if InBL and InW(L) (InW)(L) in a given location L, as well as the amount of waste plastic cleaned up are known, the total outflow can be estimated. Furthermore, InB, InW, and the amount of waste plastic cleaned up can be estimated by adding up their total values for the entire waterfront.
Measurements were conducted on waterways around Kurashiki Kojoike (circumference of 2.2 km), with the cooperation of the Foundation for Environmental Rehabilitation and Redevelopment of Mizushima.
Discussion of results
The total outflow can be estimated if the InB(L), InW(L), and amount of waste plastic cleaned up at a certain location L are known from the quantification model. City waste images were analyzed, and the outflow of city plastic waste into water areas was measured. The data from the third measurement after the clean up event were generally less than the difference data between the first and second measurements, which confirmed the effectiveness of waste collection events according to the broken window theory.
References
[1] OECD (2022), Global Plastics Outlook: Economic Drivers, Environmental Impacts and Policy Options, OECD Publishing, Paris. https://doi.org/10.1787/de747aef-en. (Accessed 15 Februay 2025)
[2] Lebreton, L., van der Zwet, J., Damsteeg, J.W. et al. (2017), “River plastic emissions to the world’s oceans.” Nat Commun 8, 15611. https://doi.org/10.1038/ncomms15611 (Accessed 15 Februay 2025)
[3] Nippon Foundation Journal (2020), “Continuously increasing ocean waste.” https://www.nippon-foundation.or.jp/journal/2020/46494/ocean_pollution/ (Accessed 15 Februay 2025)