Surfactants and submicron sea spray generation

Abstract

[1] Laboratory experiments have been carried out to elucidate the role of surfactants on the primary marine aerosol production of submicron marine aerosols. A synthetic surfactant SDS was used in conjunction with artificially generated seawater, and the resultant bubble-mediated aerosol produced was observed. At 23°C, the aerosol distribution resulting from the use of surfactant-free seawater comprised three modes: (1) a dominant accumulation mode at 110 nm; (2) an Aitken mode at 45 nm; and (3) a third mode, at 300 nm, resulting from forced bursting of bubbles. The forced bursting occurs when bubbles fail to burst upon reaching the surface and are later shattered by splashing associated with breaking waves and/or wind pressure at the surface. At 4°C, the accumulation mode diameter was reduced to 85 nm, the Aitken mode diameter was reduced to <30 nm and the 300 nm mode diameter was reduced to 200 nm. With the addition of SDS, the relative importance of the mode resulting from forced bursting increased dramatically. The laboratory results were compared to the observed seasonality of North Atlantic marine aerosol where a progression from mode radii minima in winter to maxima in summer is seen. The bimodality and the seasonality in modal diameter can be mostly explained by a combination of the three modes observed in the laboratory and their variation as a function of sea-surface temperature and seawater surfactant concentration. These results indicate that submicron primary aerosol modes would on a first approximation result from bubble bursting processes, although evidences of additional secondary processes leading, during summer, to a higher amplitude of the Aitken mode and mode 2 smoothed into mode 3 still need to be investigated.

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

“…[48] The multimodal nature of the lower end of the sea spray aerosol size distribution has also been noted in recent group bubble experiments [Fuentes et al, 2010b;Sellegri et al, 2006]. The multiple modes provide further evidence that there may, in fact, be a number of different production Increasing bubble persistence Figure 6.…”

“…[5] However, the theory fails to account for the even smaller sea spray particles observed in many recent laboratory and ambient studies [Clarke et al, 2006;Fuentes et al, 2010a;Hultin et al, 2010;Keene et al, 2007;Martensson et al, 2003;Modini et al, 2010;Russell and Singh, 2006;Sellegri et al, 2006;Tyree et al, 2007]. Specifically, there is little explanation for the dominant SSA accumulation mode centered at~0.1-0.2 mm dry particle diameter.…”

“…In addition, Fuentes et al observed a corresponding shift in the submicrometer size distribution of the generated particles to smaller sizes. Sellegri et al [2006] also observed a size distribution downshift with the addition of sodium dodecyl sulfate (SDS) to seawater in a group bubble experiment, but their work did not quantify a change in the total number of particles produced (although they noted no measurable suppression).…”

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.…”

A Marine Aerosol Reference Tank system as a breaking wave analogue for the production of foam and sea-spray aerosols

“…Several different methods have been used to generate surrogate marine aerosols within enclosed tanks including pressurized atomizers (Svenningsson et al, 2006;Riziq et al, 2007;Saul et al, 2006;McNeill et al, 2006;Braban et al, 2007;Niedermeier et al, 2008;Taketani et al, 2009), forcing air through glass filters or sintered materials (Cloke et al, 1991;Martensson et al, 2003;Sellegri et al, 2006;Keene et al, 2007;Tyree et al, 2007;Wise et al, 2009;Hultin et al, 2010;Fuentes et al, 2010) and by a plunging water jet (Cipriano and Blanchard, 1981;Sellegri et al, 2006;Facchini et al, 2008;Fuentes et al, 2010).…”