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Lagrangian mean drift induced by acoustic waves in a horizontal porous layer with one permeable bounding plane
Summary
This is actually a physics/math paper, not a health study, but here's the connection: researchers built a mathematical model showing how sound waves traveling through the seafloor (like those from earthquakes) can create tiny water currents that pull material upward through the ocean floor's sediment layer. This suggests a previously overlooked way that microplastics buried in deep-sea mud could get stirred back up into ocean water, which matters because it's one more potential pathway for microplastics to re-enter the food chain that eventually reaches our plates. The paper is theoretical, so more research would be needed to confirm this actually happens at meaningful scales in real
We consider a horizontal porous layer of constant thickness with Darcy friction and derive the nonlinear Lagrangian equations for the mean drift of fluid due to plane acoustic waves propagating along the layer. One of the bounding planes is assumed to be impermeable to fluid motion, while the other is permeable. The porous lattice is taken to have the same acoustic impedance as the fluid in the pores. Because the Darcy friction is linear in velocity, the flow in the porous medium is irrotational. However, this friction introduces dissipation in the fluid, so that the Lagrangian drift velocity in irrotational acoustic waves can be uniquely determined. The divergent horizontal Lagrangian mean drift due to spatially damped acoustic waves induces a vertical flow through the permeable boundary which may transport accumulated material into the fluid. Of particular interest here is the possible vertical transport of microplastics from reservoirs in the deep-sea benthic sediments into the ocean water caused by seismic primary waves.