Upstream contamination in water pouring

TL;DR

This study observes how floating particles can be transported upstream during water pouring, potentially contaminating water sources through vortex and Marangoni effects.

Contribution

It reports a novel phenomenon of upstream particle transport during pouring and proposes a possible explanation involving vortices and Marangoni forces.

Findings

Particles can move upstream on water surface during pouring.

Upstream transport can lead to contamination of water sources.

Marangoni forces may play a role in particle movement.

Abstract

We report the observation of upstream transport of floating particles when clear water is poured on the surface of a flat water surface on which mate or chalk particles are sprinkled. As a result, particles originally located only at the surface of the lower container can contaminate the upper water source by "riding" on vorticial water currents. We speculate that Marangoni forces in combination with geometry-induced vortices may explain the observed phenomenon.