Modeling the Concentration Enhancement and Selectivity of Plastic Particle Transport in Sea Spray Aerosols.

Bursting bubbles transport bacteria, viruses, and other marine particles across the air‐sea interface. This effect is enhanced when particles are hydrophobic and cling to the bubbles as they rise. Recent studies suggest that plastic particles, a major ocean pollutant, can also be transported by sea spray. However, estimates of plastic transport via this pathway have large uncertainties due to limited size detection techniques in field studies and few lab studies. An understanding of the number and size of particles carried in the smallest drops, which have the longest residence time in the atmosphere, is missing from current literature. Here, we develop a modeling framework to provide bounds on the number, area, and volume transport of non‐scavenged hydrophilic and fully‐scavenged hydrophobic particles of radii between 0.1 and 100 μm for a range of jet and film drops. For droplets containing plastic particulates, we predict particle enrichment is significantly higher in jet drops than film drops. For particles in these jet drops, our results suggest that in the absence of bubble scavenging, the number distribution is dominated by smaller plastics, the mass/volume distribution by larger plastics, and surface area distribution is balanced across plastic size. Whereas for hydrophobic particles, scavenging dramatically modifies these distributions, enhancing certain particle–droplet size combinations by over four orders of magnitude. Our predictions suggest critical effects of enrichment in air‐sea particle transport and highlight the variable dependencies on bubble and particle size, improving our theoretical understanding of plastic and marine particle transport and identifying modeling assumptions to refine with experimental measurements. Plain Language Summary: Plastic particles in the oceans are a topic of growing concern due to their spread throughout the environment. The oceans are a reservoir of plastics, however recent studies have found that bursting bubbles can eject the plastic into the atmosphere, where it has the potential to be transported much further. We create a first‐principles modeling framework to estimate the expected effects of particle and bubble size on the transport of hydrophobic and hydrophilic particles. We predict bounds on the extent that hydrophobic particles, like some plastics, may be highly selected to become airborne compared to hydrophilic particles. Selectivity effects are especially significant for the small airborne drops, which is important if it is the size of the drops rather than the size of the particle that influences the time they remain suspended in the atmosphere. This model provides a means to untangle the effects of bubble and particle size, as well as provide theoretical predictions to test against experimental data. This generic framework can be applied to the air‐sea transport of particles beyond plastics, with important implications to the selective aerosolization of other particles such as viruses or bacteria. Key Points: Modeling reveals how the air‐sea transfer of hydrophilic/phobic particles between 0.1 and 100 μm in radius varies with particle and bubble sizeParticle hydrophobicity may be key to air‐sea transport as particles are selectively aerosolized up to 300,000x under the conditions modeledFor drops containing plastic particulates, model predicts particle enrichment is significantly higher in jet drops than film drops [ABSTRACT FROM AUTHOR]

Copyright of Journal of Geophysical Research. Oceans is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)