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Heteroaggregation mechanisms of microplastics with suspended sediments in a reservoir system under variable hydraulic conditions using laboratory flume experiments
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Scientists studying a major Chinese reservoir found that microplastics stick to sediment particles and form clumps, with the type of plastic affecting how stable these clumps are. This matters because it helps explain where microplastics settle versus travel downstream in waterways, information that could improve pollution tracking and, eventually, efforts to reduce human exposure through drinking water sources.
In the Three Gorges Reservoir, interactions between microplastics (MPs) and sediments govern MP-sediment transport, but floc formation under varying flows remains unclear. Heterogeneous coagulation of polymethyl methacrylate (PMMA) and polystyrene (PS) with sediment was investigated using a custom water tank fitted with a continuously adjustable motor-driven agitating valve to generate shear rates (G = 10-160 s −1 ). The results indicated that the mean floc size initially increased and then leveled off with time under shear. At the end of the 180 min experiments, the floc sizes reached 107.03 μm (PMMA-sediment, G = 30 s −1 ), and 103.99 μm (PS-sediment) and 101.86 μm (sediment) at G = 40 s −1 . The fractal dimension first decreased and then increased with increasing G, ranging from 2.36 to 2.52. The floc size balance ranged from 60.53 to 105.36 μm across all shear conditions. XPS revealed electron transfer and chemical shifts, including C-O-C and O-C=O peak shifts, during PMMA and PS aggregation with sediment, forming unsaturated C=C bonds. PMMA showed larger binding energy changes than PS, indicating greater electron loss and stronger sediment adsorption. DLVO theory revealed a lower energy barrier for PMMA-sediment (4437.22 kT) than PS-sediment (4680.38 kT); AFM analyses showed higher adhesive force for PMMA-sediment (48.05 nN) than PS-sediment (30.27 nN), indicating weaker repulsion and stronger cohesion for PMMA, which facilitated more stable floc formation. These results indicate that PMMA-sediment are more stable than PS-sediment. This study elucidates MP-sediment flocculation under varying hydraulics, revealing hydrodynamic controls and providing a scientific basis for environmental pollution risk assessment and riverine MPs management.
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Aggregation characterization and mechanism of microplastics and suspended sand in the Three Gorges Reservoir
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Researchers conducted large-scale flume experiments to characterize aggregation between PMMA and PS microplastics and suspended sediment from the Three Gorges Reservoir under shear flow conditions, finding that heteroaggregation produced larger floc sizes than sediment alone and that PMMA formed aggregates more readily than PS due to greater electron transfer and surface charge changes.
[Research Progress on Environmental Behavior and Ecological Effects of Microplastics in Reservoirs in China].
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Analysis of microplastic research in Chinese reservoirs from 2013–2024 found average surface water abundances of 11,542 n/m³, with polyethylene, polypropylene, and polystyrene dominating, and smaller particles showing higher abundance — with biofilm formation and pollutant adsorption identified as key ecological risks. This systematic review of reservoir microplastic dynamics is directly relevant to drinking water safety, as reservoirs are major sources of human water supply in China.
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Researchers studied how microplastics clump together with soil and rock minerals in water, finding that positively charged minerals bound to plastic particles nearly three times more effectively than clay minerals, and that low pH and calcium ions dramatically accelerated aggregation. Understanding these dynamics helps predict where microplastics will settle or stay suspended in rivers, lakes, and aquifers.
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Microplastics across a full size range were found in a Chinese reservoir, with small-sized particles (less than 300 micrometers) dominating and showing seasonal variation linked to rainfall and runoff, highlighting reservoirs as underappreciated sinks and sources of fine microplastic pollution.
Fate and Distribution of Floating Microplastics in a Shallow Urban Lake: Field Sampling and Lagrangian Particle Tracking
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Scientists tracked how tiny plastic bits move and collect in a shallow urban lake in China, a source of drinking water for nearby communities. Understanding where these plastics accumulate helps identify hotspots that may need cleanup or filtering before water reaches our taps, since we still don't fully know the health effects of ingesting microplastics.
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