受賞国：日本国

Deans Award for excellence in research awarded at Interdisciplinary Graduate School of Engineering Sciences

受賞区分：国際学会・会議・シンポジウム等の賞 

Charles James Moore Best Student Presentation Award for presentation in ocean plastics session

受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

Outstanding Student Presentation Award in Ocean plastic Session

記述言語：英語  

Southeast Asian countries are widely acknowledged as major sources of plastic waste entering the ocean. The seasonality of floating marine debris abundance in the Gulf of Thailand (GoT) was investigated through visual observations in situ and a particle tracking model (PTM). The observations documented the highest concentration of floating debris (3329 pieces) during the northeasterly monsoon (dry season), characterized by offshore-ward winds on the beaches along the eastern coast. A PTM representing riverine plastic debris was developed to reproduce these observations by incorporating ocean surface currents, horizontal diffusion, Stokes drift, windage, and beaching/re-drifting processes. Two re-drifting processes were examined in the PTM experiments: one where re-drifting occurs on a timescale assigned to each particle with an average of 200 days and another where modeled particles were re-drifting after the onset of offshore-ward winds above the beaches. The latter experiment successfully reproduced the seasonal patterns observed in reality, although re-drifting should occur after 10–60 days from the onset of offshore-ward winds, suggesting that plastic beach litter is prevented from re-drifting immediately due to various obstructions such as beach vegetation. The results indicate that the floating plastic debris observed visually in the GoT does not directly come from rivers but from the beaches where plastic debris accumulates during the onshore-ward winds. This information will support evidence-based measures, such as beach cleanup campaigns, to effectively reduce plastic debris impact in the GoT.

DOI： 10.1016/j.rsma.2025.104718

担当区分：筆頭著者   記述言語：英語  

Although the Indian Ocean receives a large amount of land-based plastic waste, the studies on pathways of riverine plastic debris are limited to date. Therefore, a particle tracking model that included ocean surface currents, horizontal diffusion, Stokes drift, windage, and beaching/re-drifting processes was developed to reproduce the behavior of riverine plastic debris in the Indian Ocean. The modeled particles were released in the model domain based on riverine plastic debris database. The maximum abundance of beached particles occurred during the southwesterly monsoon season, particularly in the Bay of Bengal. The particles released from the rivers were trapped in the northern Indian Ocean unless both Stokes drift and windage were excluded from transportation velocity. These results suggest that the riverine plastic debris was trapped in the northern Indian Ocean until it fragmented into less buoyant small microplastics drifting in the subsurface layer, free from windage and Stokes drift at increasing depths.

DOI： 10.1016/j.marpolbul.2023.115985

開催年月日： 2026年5月

国名：日本国  

Large amounts of mismanaged plastic wastes enter the world`s oceans every year. Indian Ocean also receives a large amount of mismanaged plastic waste from the countries bordering it coastlines. The previous study by Irfan et al. (2024, Mar. Pollut., Bull.) suggested the riverine macroplastic debris trapped in the northern Indian Ocean due to windage and Stokes drift. However, microplastics traveling in the subsurface layer, free from windage and Stokes drift, may be free from the trapping. To date, our knowledge is limited about the transport pathway of macro- and microplastics in the Indian Ocean. Therefore, this research aims to understand the transport pathway of both riverine macroplastics and fragmented microplastics concurrently in the Indian Ocean using a particle tracking model (PTM), after validating it with observation data. In PTM the macroplastic particles were input from river mouths based on the riverine debris database by Lebreton et al. (2017). The macroplastic particles were fragmented into microplastic particles over the timescales assigned to each particle at their generation. The macroplastics were carried by ocean surface currents from HYCOM, Stokes drift, and horizontal diffusivity in the same fashion as microplastics except including windage. The model incorporated the exchange processes between ocean and beaches as well as the removal processes of microplastic debris from the surface layer representing settling via biological processes such as biofouling. The modeling started in the ocean free of plastics and continued for 10 years during which the daily averaged HyCOM currents over 10 years (1993 to 2017) were repeatedly used in the computation. In the PTM experiments, we demonstrate that the microplastic particles, free from windage and Stokes drift, spread over Indian Ocean including the southern area unlike macroplastics. Nonetheless, a majority of microplastics remain in the Indian Ocean, but almost 5% of microplastic particle generated in the Indian Ocean escaped eastward to the South Pacific through the Ombai Strait and Timor Sea.

開催年月日： 2024年12月

記述言語：英語   会議種別：口頭発表（一般）  

国名：アメリカ合衆国  

Large amounts of mismanaged plastic wastes enter the world`s oceans every year. Indian Ocean also receives a large amount of mismanaged plastic waste from the countries bordering it coastlines. The previous study by Irfan et al. (2024, Mar. Pollut., Bull.) suggested the riverine macroplastic debris trapped in the northern Indian Ocean due to windage and Stokes drift. However, microplastics traveling in the subsurface layer, free from windage and Stokes drift, may be free from the trapping. To date, our knowledge is limited about the transport pathway of macro- and microplastics in the Indian Ocean. Therefore, this research aims to understand the transport pathway of both riverine macroplastics and fragmented microplastics concurrently in the Indian Ocean using a particle tracking model (PTM), after validating it with observation data. In PTM the macroplastic particles were input from river mouths based on the riverine debris database by Lebreton et al. (2017). The macroplastic particles were fragmented into microplastic particles over the timescales assigned to each particle at their generation. The macroplastics were carried by ocean surface currents from HYCOM, Stokes drift, and horizontal diffusivity in the same fashion as microplastics except including windage. The model incorporated the exchange processes between ocean and beaches as well as the removal processes of microplastic debris from the surface layer representing settling via biological processes such as biofouling. The modeling started in the ocean free of plastics and continued for 10 years during which the daily averaged HyCOM currents over 10 years (1993 to 2017) were repeatedly used in the computation. In the PTM experiments, we demonstrate that the microplastic particles, free from windage and Stokes drift, spread over Indian Ocean including the southern area unlike macroplastics. Nonetheless, a majority of microplastics remain in the Indian Ocean, but almost 5% of microplastic particle generated in the Indian Ocean escaped eastward to the South Pacific through the Ombai Strait and Timor Sea.

開催年月日： 2024年5月

記述言語：英語   会議種別：ポスター発表  

国名：日本国  

Large amounts of mismanaged plastic wastes enter the world`s oceans every year. Indian Ocean also receives a large amount of mismanaged plastic waste from the countries bordering it coastlines. The previous study by Irfan et al. (2024, Mar. Pollut., Bull.) suggested the riverine macroplastic debris trapped in the northern Indian Ocean due to windage and Stokes drift. However, microplastics traveling in the subsurface layer, free from windage and Stokes drift, may be free from the trapping. To date, our knowledge is limited about the transport pathway of macro- and microplastics in the Indian Ocean. Therefore, this research aims to understand the transport pathway of both riverine macroplastics and fragmented microplastics concurrently in the Indian Ocean using a particle tracking model (PTM), after validating it with observation data. In PTM the macroplastic particles were input from river mouths based on the riverine debris database by Lebreton et al. (2017). The macroplastic particles were fragmented into microplastic particles over the timescales assigned to each particle at their generation. The macroplastics were carried by ocean surface currents from HYCOM, Stokes drift, and horizontal diffusivity in the same fashion as microplastics except including windage. The model incorporated the exchange processes between ocean and beaches as well as the removal processes of microplastic debris from the surface layer representing settling via biological processes such as biofouling. The modeling started in the ocean free of plastics and continued for 10 years during which the daily averaged HyCOM currents over 10 years (1993 to 2017) were repeatedly used in the computation. In the PTM experiments, we demonstrate that the microplastic particles, free from windage and Stokes drift, spread over Indian Ocean including the southern area unlike macroplastics. Nonetheless, a majority of microplastics remain in the Indian Ocean, but almost 5% of microplastic particle generated in the Indian Ocean escaped eastward to the South Pacific through the Ombai Strait and Timor Sea.

海洋デブリの70％を占める適切に管理されていないプラスチック廃棄物は、分解や微小プラスチックへの断片化が進んでいても、海洋環境にしぶとく残り続けています。これまでのところ、地球の歴史上初めて登場したこの人為的で浮力があり、持続的な物質がどのように地球システムを汚染する（または取り込まれる）かについては、まだ十分に解明されていません。海洋プラスチックの研究には、海洋学、地質学、古生物学など、さまざまな地球科学の知見や方法論が必要です。陸地や大気から表層海域や底質へのプラスチックの循環に関する研究、「人新世」の指標としてのマイクロプラスチックに関する研究、そしてマクロ・マイクロプラスチックのモニタリングや分析手法を確立する研究などを歓迎します。

海洋ごみの70％を占める適切に管理されていないプラスチック廃棄物は、分解され微細なマイクロプラスチックに断片化されても、海洋環境に持続的に残ります。これまでのところ、この人為的で浮力を持ち、持続的な物質が地球史上初めて出現し、どのように地球システムを汚染（または組み込まれる）するのかについては、十分に解明されていません。海洋プラスチックの研究には、海洋学、地質学、古生物学など、多様な地球科学の洞察と方法論が求められます。陸地や大気から上層海洋や底質へのプラスチック循環に関する研究、マイクロプラスチックを「人新世」のプロキシとして用いた研究、マクロ/マイクロプラスチックのモニタリングと分析手順を確立するための研究を歓迎します。