2026-09-24 北京大学（PKU）
＜関連情報＞
- https://newsen.pku.edu.cn/news_events/news/research/15678.html
- https://www.science.org/doi/10.1126/science.aeb4487
水文気候によって引き起こされる一時的な富栄養化が、発展途上国における河川からのマイクロプラスチックの流出を増幅させる Hydroclimatic-driven pulse enrichment amplifies riverine microplastic export in developing countries
Hehao Qin, Maodian Liu, Yanxu Zhang, Qianru Zhang, […] , and Xuejun Wang
Science Published:10 Sep 2026
DOI:https://doi.org/10.1126/science.aeb4487
Structured Abstract
INTRODUCTION
Plastic pollution has become one of the fastest-growing and most difficult-to-reverse components of global change. Microplastics are now detected in nearly all natural environments, from mountain soils, rivers, and lakes to coastal waters and the deep ocean. Because they are tiny, extremely abundant, and difficult to remove, microplastics can persist in the environment for long periods. They can also be ingested by plankton, fish, and benthic organisms; disrupt food-web structure; release toxic additives; and carry other pollutants, posing persistent threats to ecosystem health and potential human exposure.
Yet one key question in this global plastic crisis remains unresolved: How much microplastic do rivers deliver to the ocean? Rivers do not export microplastics in a steady, continuous way. Instead, they accumulate plastic waste and degraded microplastics from cities, croplands, roads, and floodplains and then release them in pulses, rapidly polluting coastal environments and marine food webs over short periods. Understanding where these pulses come from, how large they are, and why they differ is critical for both pollution control and climate adaptation.
RATIONALE
Global estimates of riverine microplastic export to the ocean remain highly uncertain, mainly because observations are sparse, sampling methods are inconsistent, and most existing models are too coarse to capture real spatiotemporal variability. To address this, we compiled the largest riverine microplastic dataset assembled to date, harmonized differences among sampling methods, and developed a new global model that dynamically tracks the true upstream contributing area for each sampling location. This framework allowed us to answer two key questions: How much microplastic enters the ocean each day worldwide, and to what extent is this export amplified by rainfall-driven runoff processes?
RESULTS
Our model estimated that global rivers delivered about 263,000 metric tons of microplastics to the ocean in 2022. This export is highly uneven in space and strongly concentrated: 96% originates from rivers in developing countries, and Southeast and East Asia, despite covering only 14% of the global land area, contribute more than half of the total. Global export is further dominated by a small number of major rivers, with the Yangtze standing out as the single largest source.
This export is also highly uneven in time. In the world’s highest-export rivers, most annual export occurs during the rainy season. Across many regions, rainfall-driven high flows sharply increase riverine microplastic concentrations and fluxes, producing “pulse enrichment” rather than simple dilution.
These pulses are strongest where intense rainfall coincides with high plastic production and use, weak waste management, and efficient runoff generation. By contrast, more advanced municipal wastewater treatment and certain landscape characteristics weaken this enrichment effect. This shows that the largest plastic loads are released to the ocean not by any single factor, but by the combined action of human activity and hydroclimatic processes.
CONCLUSION
The ocean—a life-support system that sustains productive food webs exploited by humans—is receiving far more river-delivered microplastics than previously recognized, and under a warming climate, more frequent and intense rainfall and the high-flow events it triggers may further amplify this hidden but massive pollution pathway. This study highlights that unless plastic production is curbed more forcefully at the source and waste management is improved rapidly, increasingly frequent and intense extreme rainfall under climate change will continue to amplify the pulsed delivery of microplastics from rivers to the ocean, worsening marine pollution.
How much microplastic do rivers export to the ocean worldwide?
The Yangtze River, photographed at the Husutong Yangtze River Bridge near its estuary, is one of the world’s largest sources of microplastics to the ocean. PHOTO CREDIT: VCG/VISUAL CHINA GROUP
Abstract
Rivers are key conduits in the global microplastic cycle, but how much they export to ` ocean and what controls this export remain unresolved. Here, we present a global daily dataset of riverine microplastic concentrations and exports and find that rivers delivered far more microplastics to the ocean than most previous estimates suggest. Ninety-six percent of this export originated in the Global South, with Southeast and East Asia contributing >50% of the total flux. Furthermore, ~70% of global freshwater discharge exhibits “pulse enrichment,” whereby rainfall-driven high flows trigger spikes in microplastic concentrations and fluxes; 80% of these cases occur in developing countries. Without stronger upstream controls on plastic production and waste management, climate-driven increases in extreme rainfall may intensify these pulses, worsening marine microplastic pollution.
