Laboratory-generated primary marine aerosol via bubble-bursting and atomization

Abstract

Abstract.A range of bubble and sea spray aerosol generators has been tested in the laboratory and compared with oceanic measurements from the literature. We have shown that the method of generation has a significant influence on the properties of the aerosol particles produced. Hence, the validity of a generation system to mimic atmospheric aerosol is dependent on its capacity for generating bubbles and particles in a realistic manner. A bubble-bursting aerosol generator which produces bubbles by water impingement was shown to best reproduce the oceanic bubble spectral shapes, which confirms previous findings.Two porous bubblers and a plunging-water jet system were tested as bubble-bursting aerosol generators for comparison with a standard nebulizer. The methods for aerosol production were evaluated by analysing the bubble spectrum generated by the bubble-bursting systems and the submicron size distribution, hygroscopicity and cloud condensation nucleus activity of the aerosols generated by the different techniques. Significant differences in the bubble spectrum and aerosol properties were observed when using different aerosol generators.The aerosols generated by the different methods exhibited similar hygroscopicity and cloud condensation nucleus activity behaviour when a sample of purely inorganic salts was used as a parent seawater solution; however, significant differences in the aerosol properties were found when using samples of filtered natural seawater enriched with biogenic organics. The presence of organics in the aerosol caused suppression of the growth factor at humidities above 75% RH and an increase in the critical supersaturation with respect Correspondence to: G. McFiggans (g.mcfiggans@manchester.ac.uk) to the generation from artificial seawater devoid of organics. The extent of the effect of organics on the aerosol properties varied depending on the method of particle production. The results of this work indicate that the aerosol generation mechanism affects the particles organic enrichment, thus the behaviour of the produced aerosols strongly depends on the laboratory aerosol generator employed.Comparison between bubble lifetimes in several laboratory simulations and the oceanic conditions indicated that it would require a considerable extension of the dimensions of the currently used bubble-bursting laboratory systems in order to replicate the characteristic oceanic bubble lifetimes. We analyzed the implications derived from the reduced bubble residence times in scaled systems, regarding marine surfactants adsorption on rising bubbles, and found that adsorption equilibrium is reached on a timescale much shorter than the bubble lifetime in small-scale laboratory generators. This implies that adsorption of marine surface-active material is not limited by surfactant transport to the bubble surface.

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

“…We do not believe that the deficit can be accounted for by the absence in this work of any particular type of particle potentially found in natural sea spray aerosols, such as small organic particles or microgels, since source fluxes measured above artificial seawaters are comparable to those measured above natural seawaters under similar bubbling conditions (OC = 0 mM curve in Figure 7) [Fuentes et al, 2010a;Martensson et al, 2003;Tyree et al, 2007].…”

“…[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.…”

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

“…The detailed investigations by Sellegri et al (2006) and Fuentes et al (2010) have shown that the best method for the laboratory generation of proxy marine aerosols is to create a bubble plume from a plunging jet of water. The method of generation used had a strong influence over the chemical and physical properties of the aerosols produced in including variation in organic enrichment, formation of condensation nuclei and variation in hygroscopicity (Fuentes et al, 2010) and bubbles generated by the plunging jet more closely approximated those from oceanic measurements.…”

“…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).…”

Stability of a bi-layer free film: simultaneous or individual rupture events?

“…Bursting of bubbles at interfaces is a familiar everyday occurrence, playing an important role in a spectrum of phenomena, including foam evolution (Neethling et al 2005), cell death (Cherry & Hulle 1992) and aerosol generation (Wu 1981;Fuentes et al 2010). For example, Lhuissier & Villermaux (2012) performed experiments characterizing the life cycle of a bursting bubble, examining the motion from the instant the bubble first deflects the liquid surface until the bursting dynamics that leads to dispersed drops in the air.…”