DUGi

Shear-Induced infiltration of microplastics of bottom aquatic system floors

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Although the effects of microplastic sedimentation in bottom sediments of continental and marine aquatic systems have been widely studied, there is limited information available on the role of nearbed turbulence in the burial of microplastics within bottom sediments. To explore this phenomenon, a series of experiments was designed, considering four turbulence intensities, a single exposure duration, and one sediment consolidation period identified as key factors that may promote the incorporation of microplastics into the sediment through turbulent mixing processes. The aim is also to determine the dynamic infiltration that governs the presence of microplastics at different depths within the sediment. Eight different types of microfibres, previously deposited on a sediment bed, were subjected to turbulence generated by an oscillating grid. The experimental procedure consists of two main phases: first, the resuspension of sediment and microplastics; and then, once turbulence generation has ceased, the dynamic infiltration of the remobilized materials. This experimental process simulated the natural dynamics of the seabed in aquatic environments exposed to turbulent events, such as waves or wind. The results revealed that the burial depth of microplastics depended on variables such as the shear stress applied to the sediment, the physical characteristics of the microplastics (diameter and settling velocity), and the sediment consolidation time. To explain and predict this behaviour, a nondimensional variable model was developed to estimate the infiltration depth of microplastics into the sediments. This model is a useful tool for understanding the burial processes of microplastics in aquatic environments such as lakes, ponds, and oceans. The bottoms of aquatic systems can become highly contaminated with microplastics. This process had not been studied until now, and therefore this work provides fundamental knowledge for understanding microplastic pollution in the sediments of aquatic systems

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