Effect of soluble surfactant on bubble persistence and bubble‐produced aerosol particles

Abstract

[1] The effect of soluble surfactant on the persistence of salt-water bubbles and their ability to produce aerosol particles upon bursting was investigated. Ensembles of individual, millimetric bubbles were produced in NaCl solutions of varying surfactant concentration. Aerosol production efficiency-a fundamental property of single bubbles defined as the number of particles produced per bubble film cap area-decreased by 79% to 98% following the addition of surfactant and increase in solution film pressure from 1-2 to 7-27 mN m À1 . The generated particle size distributions (0.01-10 mm dry diameter) contained up to three modes and did not change much for film pressures up to 13.8 mN m À1 . The persistence of the bubbles at the water surface and the thickness of their film caps were investigated with high-speed videography. Addition of soluble surfactant increased average bubble persistence providing more time for the bubbles to drain and thin out with the aid of marginal regeneration flows. Bubble film cap thicknesses ranged from around 1 mm for relatively clean, short-lived bubbles to less than 0.1 mm for surfactant-stabilized, persistent bubbles. The suppression of aerosol production from the surfactant-stabilized bubbles may have resulted from the dramatic thinning of their caps or reduced surface forces at high film pressure. Previously reported Sea Spray Aerosol source functions were compared to measured aerosol production efficiencies and found to be significantly greater in magnitude, suggesting that there is a source of particles from whitecaps that was not captured in these single-bubble experiments.

Enriching particles on a bubble through drainage: Measuring and modeling the concentration of microbial particles in a bubble film at rupture

“…The thicknesses at rupture that we measured ranged from h = 5 µm to h = 60 µm. These values are larger than what might be expected in particulate-free bubble films (Spiel, 1998;Modini et al, 2013), and we suspect that the presence of particulates may act as nucleation sites that initiate rupture earlier in the drainage process. However, the physics that determine the thickness at which a water bubble spontaneous ruptures is currently unknown (Lhuissier and Villermaux, 2012).…”

“…In contrast, the film thickness at rupture h appeared to be independent of the bulk yeast concentration C b over the range of concentrations tested (Figure 2b). Here we used the standard technique to measure the film thickness at rupture h by measuring the speed at which the nearly uniform film retracted (Pandit and Davidson, 1990;Lhuissier and Villermaux, 2012;Modini et al, 2013). The surface tension-driven retraction is regulated by inertia and is well approximated by the Taylor-Culick velocity, 2 / h γ ρ , where γ is the surface tension and ρ is the liquid density (Taylor, 1959;Culick, 1960).…”

Global distribution and surface activity of macromolecules in offline simulations of marine organic chemistry

“…Only the February result is shown, but other seasons follow annual trends from 1 through 6. The quantity is dimensionless and is presented as the base 10 logarithm Biogeochemistry (2015) 126:25-56 45 Breaking bubbles and the nascent spray are thought to be similar in thickness at about one-tenth micron (Gong 2003;O'Dowd and De Leeuw 2007;Modini et al 2013;Burrows et al 2014). The spectrum of sea spray flux peaks near this value, so the original film may be thinner-surface tension reshaping follows closely upon bursting once the material enters the atmosphere.…”

Sea Spray Aerosol: The Chemical Link between the Oceans, Atmosphere, and Climate

“…2,5,6,14 Detailed studies of SSA production methods have shown that both breaking waves and plunging waterfall techniques replicate ambient SSA subpopulations of particles with the proper size and physical and chemical properties. 2,5 Other variables, such as temperature, 15 surfactant chemistry, 13,16 and white cap foam formation 5 are also critical factors in producing real world SSA populations. The development of these innovative laboratory-based methods has opened the doors for exploring the composition, reactivity, and properties of a globally abundant tropospheric aerosol, fresh SSA, under controlled conditions.…”