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Dynamics of microplastics bedload transport in turbulent open channel flows over smooth and rough beds
Summary
Researchers developed novel empirical formulas for predicting bedload transport layer thickness and velocity of microplastics in turbulent open-channel flows using 80 controlled flume experiments across diverse particle types and flow conditions. The new formula for bedload layer thickness reduced prediction error by 75% compared to existing sediment-based formulas, demonstrating the critical role of particle density and bed characteristics in shaping MP transport dynamics.
Microplastics (MPs) in aquatic environments pose a growing ecological threat, yet their bedload transport dynamics remain poorly quantified. This study introduces a novel formulation to predict the bedload layer thickness δ and average bedload transport velocity u of MPs under turbulent open-channel flows. Using 80 controlled flume experiments covering a wide range of microplastic types, bed roughness configurations, and flow conditions, further supported by data from existing literature, new empirical models are developed. The proposed new empirical formula for δ based on the Shields number and relative density, reduces the prediction error by 75 % compared to the existing sediment-based formulas. Additionally, to explicitly quantify the u in the bedload layer, an empirical formula incorporating the relative roughness has been established, with a 14.05 % error, substantially outperforming the existing approaches. These findings demonstrate the critical role of particle density and bed characteristics in shaping the MP bedload transport dynamics and offer a robust framework for improving MPs transport models in riverine systems.
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