The capture of airborne particulates by rain

Abstract

Rain cleans pollution out of the atmosphere, as droplets collide with airborne particles during free fall. Such particle–droplet collisions have been presumed to be capture events, but the details of such collisions lack thorough investigation. We show that rain droplets and pollution particles interact through multiple collision behaviours, including captures on the droplet surface, cavity-forming droplet entries and ricochets. Rain drop diameter and free fall velocity, in addition to pollution particle density, size, wettability and droplet impact location, determine which capture or escape behaviour occurs. Our findings reveal that rain does not capture all airborne pollutants equally even upon collision, and certain pollutants prove more difficult to remove from the air than others. Consequently, we must account for both rain and pollution characteristics to understand pollution capture mechanisms and pollution fluxes in the environment.

Bridging the gap: harnessing liquid nanomachine know-how for tackling harmful airborne particulates

“…Multiple capture methods have been reported, such as surface capture, cavity-forming entry, skid entry, and escape. 95…”

Microfluidic jet impacts on deep pools: transition from capillary-dominated cavity closure to gas-pressure-dominated closure at higher Weber numbers

“…The domain of interest for our work is in the micrometre regime, where collapse is driven by surface tension forces as Bo ∼ O(10 −3 ). This regime is relevant in emerging technologies such as three-dimensional printing (Antkowiak et al 2011), spray painting (Herczyński, Andrzej & Claude 2011), extreme-ultraviolet lithography (Klein et al 2015), environmental aspects (Speirs, Belden & Hellum 2023) and needle-free injection methods (Berrospe-Rodriguez et al 2016;Oyarte Galvez et al 2020;van der Ven et al 2023).…”

“…2011), spray painting (Herczyński, Andrzej & Claude 2011), extreme-ultraviolet lithography (Klein et al. 2015), environmental aspects (Speirs, Belden & Hellum 2023) and needle-free injection methods (Berrospe-Rodriguez et al. 2016; Oyarte Galvez et al.…”