Effects of Salinity Beyond Coalescence on Submicron Aerosol Distributions
Effects of Salinity Beyond Coalescence on Submicron Aerosol Distributions
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DOI：
10.1029/2022jd038222
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发表时间：
2023-05
期刊：
影响因子：
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通讯作者：
L. Dubitsky;M. D. Stokes;G. Deane;J. Bird
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文献类型：
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作者：
L. Dubitsky;M. D. Stokes;G. Deane;J. Bird
被海浪卷起的气泡上升到表面并破裂，产生大量水滴，从而形成海雾气溶胶。亚微米大小的水滴在全球气候大气过程中发挥着关键作用，其中约60%-80%来自破裂的气泡膜帽。然而，预测破裂气泡释放出的亚微米液滴的数量和大小的许多方面仍然是未知的。众所周知，较高的盐度会增加亚微米液滴的产量，这归因于盐在抑制气泡合并方面的作用。我们的实验表明，尽管使用了不影响气泡合并的盐，但亚微米液滴的产量随着盐度的增加而增加，这表明盐度在亚微米气溶胶形成的物理过程中起到了超越合并的作用。实验室实验是使用盐度S=0.001-0.1M的醋酸钠溶液，通过针头产生毫米大小的气泡。与以往的研究不同，测量的液滴尺寸分布被转换为地层直径，表明气溶胶形成的峰值直径随着盐度的增加而减小。将这个直径换算应用到过去的研究中，我们发现，对于各种盐类、气泡合并行为和气泡生成机制，峰值形成直径在盐度的三个数量级上呈现出∼S−0.32的标度。这一结果表明，盐度对产生气溶胶的破裂气泡膜的长度尺度有系统的影响。因此，盐度可能会影响海洋环境中亚微米气溶胶的产生，即使气泡合并可以忽略不计。
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 salinity S = 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 of Dform ∼ S−0.32 across 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.