Marine Aerosol Production via Detrainment of Bubble Plumes Generated in Natural Seawater With a Forced‐Air Venturi

Abstract

During September–October 2016, a marine aerosol generator configured with forced‐air Venturis was deployed at two biologically productive and two oligotrophic regions of the western North Atlantic Ocean to investigate factors that modulate primary marine aerosol (PMA) production. The generator produced representative bubble size distributions with Hinze scales (0.32 to 0.95 mm radii) and void fractions (0.011 to 0.019 Lair Lsw‐1) that overlapped those of plumes produced in the surface ocean by breaking wind waves. Hinze scales and void fractions of bubble plumes varied among seawater hydrographic regions, whereas corresponding peaks and widths of bubble size distributions did not, suggesting that variability in seawater surfactants drove variability in plume dynamics. Peaks in size‐resolved number production efficiencies for model PMA (mPMA) emitted via bubble bursting in the generator were within a narrow range (0.059 to 0.069 μm geometric mean diameter) over wide ranges in subsurface bubble characteristics, suggesting that subsurface bubble size distributions were not the primary controlling factors as was suggested by previous work. Total mass production efficiencies for mPMA decreased with increasing air detrainment rates, supporting the hypothesis that surface bubble rafts attenuate mPMA mass production. Total mass and Na+ production efficiencies for mPMA from biologically productive seawater were significantly greater than those from oligotrophic seawater. Corresponding mPMA number distributions peaked at smaller sizes during daytime, suggesting that short‐lived surfactants of biological and/or photochemical origin modulated diel variability in marine aerosol production.

Atmospheric Research Over the Western North Atlantic Ocean Region and North American East Coast: A Review of Past Work and Challenges Ahead

“…A motivator for advancing understanding of primary marine aerosol production fluxes, and associated source function parameterizations, is that these generated particles impact a host of important reactive constituents such as halogens and organics, as well as impacting a number of processes linked to radiative transfer, cloud formation, precipitation, and biogeochemical cycles. Further characterization of the constituents enriched in these generated aerosols by bursting bubbles is important to continue learning about the enhancement of organics as was shown convincingly in several studies linked to the R/V Endeavor cruise between September and October 2016 over the WNAO (Beaupré et al, ; Frossard, Gérard, et al, ; Frossard, Long, et al, ).…”

“…The photic zone contains dissolved organic matter composed of carbohydrates and particles containing viruses, bacteria, algae, and organic dedritus that can bind together by exopolymer gels and contribute to the MBL aerosol budget after bubble bursting (Bigg et al, ; Facchini, Rinaldi, et al, ; Quinn & Bates, ). A large body of work for the WNAO region, including over the Sargasso Sea, provides consensus that primary marine aerosols ejected from the sea surface are highly enriched in marine‐derived organics relative to sea water (Beaupré et al, ; Frossard, Gérard, et al, ; Frossard, Long, et al, ; Keene, Maring, et al, ; Long, Keene, Kieber, et al, ; Quinn et al, ) and that these organic‐laden aerosols are both CCN‐active (Quinn et al, ) and reactive (Zhou et al, ).…”

“…Between September and October 2016, a research cruise with the R/V Endeavor over the WNAO was conducted to investigate marine aerosol production from bursting bubbles and the physicochemical properties of the generated primary marine aerosol (Beaupré et al, 2019;Frossard, Gérard, et al, 2019;Frossard, Long, et al, 2019). Results from this project have revealed that primarily produced marine aerosols are enriched with marine-derived organic constituents, including surfactants, relative to sea water (Frossard, Gérard, et al, 2019).…”

Collective bursting of free-surface bubbles, and the role of surface contamination

“…Sea spray generation is related to surface breaking waves, either directly during wave impact and atomization by wind shear (Veron et al 2012;Erinin et al 2019), or through bubble bursting following air entrainment by breaking (Deike, Melville & Popinet 2016;Deike, Lenain & Melville 2017;Deike & Melville 2018) so that the sea state modulates the droplet production , together with the precise ocean water temperature and composition (salinity, biological activity, etc.) which will impact interfacial phenomena (Wang et al 2017;Frossard et al 2019).…”

“…Multiple approaches have attempted to describe the role of the physicochemical parameters in bubble bursting and the subsequent droplet and aerosol production, with large variations in protocols and results sometimes contradicting each other. Frossard et al (2019) describe a bubble plume simulator, taken aboard a cruise to produce an abundant sea spray with real-time ocean conditions, and observe an increase in spray production with increased biological activity and inferred surfactant conditions. The laboratory experiment of Modini et al (2013), which investigates the effect of surfactant on saltwater single bubble bursting, yields the opposite conclusion that the aerosol production efficiency is decreased by the addition of surfactant.…”