Modeling of microplastics fluxes using river flow and basin data

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H04937
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Hydraulic engineering
• Research Institution: Tokyo University of Science
• Principal Investigator: Kataoka Tomoya 東京理科大学, 理工学部土木工学科, 助教 (70553767)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 河川マイクロプラスチック / 輸送量 / 鉛直分布 / 横断分布 / マクロプラスチック / 画像解析

Outline of Final Research Achievements

In order to answer the academic question for global plastic pollution: how much microplastics is released from Japanese rivers to the oceans, three types of in-situ surveys (sampling in multiple Japanese rivers, sampling during the floods and sampling in river cross section) had been conducted in the research period. High-resolution map of microplastic emission was generated using the linear relationship between microplastic concentration and basin characteristics (population density and urban ratio) established from sampling in the 70 rivers. Based on the map, annual plastic emission from Japan was estimated, which was 210 to 4776 ton. Expectedly, the plastic emission from the three major metropolitan areas was predominant over other areas. To more accurately estimate the plastic emission, we will consider the temporal variability of microplastic concentration during floods and the spatial distribution of microplastic concentration in river cross section in near future.

Free Research Field

水工学

Academic Significance and Societal Importance of the Research Achievements

本研究は，国内河川におけるマイクロプラスチック（MicP）調査の先駆けであった．また，全国河川を対象にした研究例は世界的にも類を見ない研究成果であり，結果として人為的影響の大きい汚濁河川でMicP濃度が高いという重要な学術的知見が得られた．本研究成果は，沿岸地域だけでなく，内陸域でも河川を介して海洋へMicPを流出させていることを示しており，社会的にもインパクトのある研究成果が得られた．また，現地調査に基づいてMicP濃度の出水時における短期変化や河川横断面分布を明らかにしており，河川におけるMicPの流体力学的な挙動を明らかにするための学術的に重要なデータが得られた．