Regensburg 2022 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 34: Fluid Physics: Turbulence and Convection
DY 34.1: Vortrag
Mittwoch, 7. September 2022, 15:30–15:45, H19
Ejection of marine microplastics by raindrops: A computational and experimental study — •Moritz Lehmann1, Lisa Marie Oehlschlägel2, Fabian Häusl1, Andreas Held2, and Stephan Gekle1 — 1Biofluid Simulation and Modeling - Theorethische Physik VI, Universität Bayreuth — 2Umweltchemie und Luftreinhaltung, Technische Universität Berlin
Raindrops impacting water surfaces such as lakes or oceans produce myriads of tiny droplets which are ejected into the atmosphere at very high speeds. Here we combine computer simulations and experimental measurements to investigate whether these droplets can serve as transport vehicles for the transition of microplastic particles with diameters of a few tens of micrometers from ocean water to the atmosphere. Using the Volume-of-Fluid lattice Boltzmann method, extended by the immersed-boundary method, we performed more than 1600 raindrop impact simulations and provide a detailed statistical analysis on the ejected droplets. Using typical sizes and velocities of real-world raindrops, we simulate straight impacts with various raindrop diameters as well as oblique impacts. We find that a 4 mm diameter raindrop impact on average ejects more than 167 droplets. We show that these droplets indeed contain microplastic concentrations similar to the ocean water within a few millimeters below the surface. To further assess the plausibility of our simulation results, we conduct a series of laboratory experiments, where we find that microplastic particles are indeed contained in the spray. Based on our results and known data, we estimate the global relevance of this transport mechanism.