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Abstract Gas bubbles bursting at the sea surface produce drops, which contribute to marine aerosols. The contamination or enrichment of water by surface‐active agents, of biological or anthropogenic origin, has long been recognized as affecting the bubble bursting processes and the spray composition. However, despite an improved understanding of the physics of a single bursting event, a quantitative understanding of the role of the physico‐chemical conditions on assemblies of bursting bubbles remains elusive. We present experiments on the drop production by millimetric, collective bursting bubbles, under varying surfactant concentration and bubble density. We demonstrate that the production of supermicron droplets (with radius larger than 35 μm) is non‐monotonic as the surfactant concentration increases. The bursting efficiency is optimal for short‐lived, sparsely distributed and non‐coalescing bubbles. We identify the combined role of contamination on the surface bubble arrangement and the modification of the jet drop production process in the bursting efficiency.
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Effects of Salinity Beyond Coalescence on Submicron Aerosol Distributions
Abstract Bubbles entrained by ocean waves rise to the surface and burst, creating a shower of droplets which contribute to sea spray aerosols. Submicron‐sized droplets, of which an estimated 60%–80% come from a bursting bubble film cap, play a key role in global climate atmospheric processes. However, many aspects of predicting the number and size of submicron drops emitted from a bursting bubble remain unknown. It is well‐documented that higher salinity increases submicron droplet production, which has been attributed to the role of salt in the suppression of bubble coalescence. We experimentally show that submicron drop production increases with salinity despite using a salt that does not affect bubble coalescence, indicating that salinity plays a role in the physics of submicron aerosol formation beyond coalescence. Laboratory experiments are conducted using sodium acetate solutions of salinityS = 0.001–0.1 M with millimeter‐sized bubbles generated via a needle. Unlike previous studies, the measured droplet size distributions are converted to formation diameter, revealing that the peak aerosol formation diameter decreases with higher salinity. Applying this diameter conversion to past studies, we find the peak formation diameter exhibits a scaling ofDform ∼ S−0.32across three orders of magnitude in salinity and for a variety of salts, bubble coalescence behaviors, and bubble generation mechanisms. This result suggests that salinity has a systematic effect on the length scale of the rupturing bubble film which generates the aerosols. Consequently, salinity likely impacts the submicron aerosol production in oceanic environments even if bubble coalescence is negligible.
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- Award ID(s):
- 2114489
- PAR ID:
- 10415072
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 128
- Issue:
- 10
- ISSN:
- 2169-897X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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