review of Sea spray aerosol organic enrichment, water uptake and surface tension effects

Abstract. The aerosol driven radiative effects on marine low-level cloud represent a large uncertainty in climate simulations, in particular over the Southern Ocean, which is also an important region for sea spray aerosol production. Observations of sea spray aerosol organic enrichment and the resulting impact on water uptake over the remote southern hemisphere are scarce, and are therefore the region is under-represented in existing parameterisations. The Surface Ocean Aerosol Production (SOAP) voyage was a 23 day voyage which sampled three phytoplankton blooms in the highly productive water of the Chatham Rise, east of New Zealand. In this study we examined the enrichment of organics to nascent sea spray aerosol and the modifications to sea spray aerosol water uptake using in-situ chamber measurements of seawater samples taken during the SOAP voyage. Primary marine organics contributed up to 23 % of the sea spray mass for particles with diameter less than approximately 1 μm, and up to 87 % of the particle volume in the Aitken mode. The composition of the organic fraction was consistent throughout the voyage and was largely comprised of a polysaccharide-like component, characterised by very low alkane to hydroxyl concentration ratios of approximately 0.1–0.2. The enrichment of organics was compared to the output from the chlorophyll-a based sea spray aerosol parameterisation suggested by Gantt et al. (2011) and the OCEANFILMS models. OCEANFILMS improved on the representation of the organic fraction predicted using chlorophyll-a, in particular when the co-adsoprtion of polysaccharides was included, however the model still under predicted the proportion of polysaccharides by an average of 33 %. Nascent sea spray aerosol hygroscopic growth factors averaged 1.93 ± 0.08, and did not decrease with increasing sea spray aerosol organic fractions. The observed hygroscopicity was greater than expected from the assumption of full solubility, particularly during the most productive phytoplankton bloom (B1), during which organic fractions were greater than approximately 0.4. The water uptake behaviour observed in this study is consistent with that observed for other measurements of phytoplankton blooms, and was attributed to the surface partitioning of the organic components which leads to a decrease in particle surface tension and an increase in hygroscopicity. The compressed film model was used to estimate the influence of surface partitioning and the error in the modelled hygroscopicity was low only when the entire organic fraction was available to partition to the particle surface. The modelled sea spray aerosol hygroscopicity at high organic fractions was underestimated when only a portion of the organic component was available to be partitioned to the surface. The findings from the SOAP voyage highlight the influence of biologically-sourced organics on sea spray aerosol composition, these data improve the capacity to parameterise sea spray aerosol organic enrichment and water uptake.

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Sea spray aerosol organic enrichment, water uptake and surface tension effects

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-7955-2020 ◽

2020 ◽

Vol 20 (13) ◽

pp. 7955-7977 ◽

Cited By ~ 2

Author(s):

Luke T. Cravigan ◽

Marc D. Mallet ◽

Petri Vaattovaara ◽

Mike J. Harvey ◽

Cliff S. Law ◽

...

Keyword(s):

Surface Tension ◽

Chlorophyll A ◽

Water Uptake ◽

Organic Enrichment ◽

Sea Spray ◽

Organic Fraction ◽

Phytoplankton Blooms ◽

Aerosol Composition ◽

Sea Spray Aerosol ◽

Organic Fractions

Abstract. The aerosol-driven radiative effects on marine low-level cloud represent a large uncertainty in climate simulations, in particular over the Southern Ocean, which is also an important region for sea spray aerosol production. Observations of sea spray aerosol organic enrichment and the resulting impact on water uptake over the remote Southern Hemisphere are scarce, and therefore the region is under-represented in existing parameterisations. The Surface Ocean Aerosol Production (SOAP) voyage was a 23 d voyage which sampled three phytoplankton blooms in the highly productive water of the Chatham Rise, east of New Zealand. In this study we examined the enrichment of organics to nascent sea spray aerosol and the modifications to sea spray aerosol water uptake using in situ chamber measurements of seawater samples taken during the SOAP voyage. Primary marine organics contributed up to 23 % of the sea spray mass for particles with diameter less than approximately 1 µm and up to 79 % of the particle volume for 50 nm diameter sea spray. The composition of the submicron organic fraction was consistent throughout the voyage and was largely composed of a polysaccharide-like component, characterised by very low alkane-to-hydroxyl-concentration ratios of approximately 0.1–0.2. The enrichment of organics was compared to the output from the chlorophyll-a-based sea spray aerosol parameterisation suggested by Gantt et al. (2011) and the OCEANFILMS (Organic Compounds from Ecosystems to Aerosols: Natural Films and Interfaces via Langmuir Molecular Surfactants) models. OCEANFILMS improved on the representation of the organic fraction predicted using chlorophyll a, in particular when the co-adsorption of polysaccharides was included; however, the model still under-predicted the proportion of polysaccharides by an average of 33 %. Nascent 50 nm diameter sea spray aerosol hygroscopic growth factors measured at 90 % relative humidity averaged 1.93±0.08 and did not decrease with increasing sea spray aerosol organic fractions. The observed hygroscopicity was greater than expected from the assumption of full solubility, particularly during the most productive phytoplankton bloom (B1), during which organic fractions were greater than approximately 0.4. The water uptake behaviour observed in this study is consistent with that observed for other measurements of phytoplankton blooms and can be partially attributed to the presence of sea salt hydrates, which lowers the sea spray aerosol hygroscopicity when the organic enrichment is low. The inclusion of surface tension effects only marginally improved the modelled hygroscopicity, and a significant discrepancy between the observed and modelled hygroscopicity at high organic volume fractions remained. The findings from the SOAP voyage highlight the influence of biologically sourced organics on sea spray aerosol composition; these data improve the capacity to parameterise sea spray aerosol organic enrichment and water uptake.

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Effect of primary organic sea spray emissions on cloud condensation nuclei concentrations

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-89-2012 ◽

2012 ◽

Vol 12 (1) ◽

pp. 89-101 ◽

Cited By ~ 46

Author(s):

D. M. Westervelt ◽

R. H. Moore ◽

A. Nenes ◽

P. J. Adams

Keyword(s):

Surface Tension ◽

Southern Ocean ◽

Source Function ◽

Cloud Condensation Nuclei ◽

Organic Aerosol ◽

Sea Salt ◽

Sea Spray ◽

Aerosol Emission ◽

Sea Spray Aerosol ◽

Surfactant Effects

Abstract. This work estimates the primary marine organic aerosol global emission source and its impact on cloud condensation nuclei (CCN) concentrations by implementing an organic sea spray source function into a series of global aerosol simulations. The source function assumes that a fraction of the sea spray emissions, depending on the local chlorophyll concentration, is organic matter in place of sea salt. Effect on CCN concentrations (at 0.2% supersaturation) is modeled using the Two-Moment Aerosol Sectional (TOMAS) microphysics algorithm coupled to the GISS II-prime general circulation model. The presence of organics affects CCN activity in competing ways: by reducing the amount of solute available in the particle and decreasing surface tension of CCN. To model surfactant effects, surface tension depression data from seawater samples taken near the Georgia coast were applied as a function of carbon concentrations. A global marine organic aerosol emission rate of 17.7 Tg C yr−1 is estimated from the simulations. Marine organics exert a localized influence on CCN(0.2%) concentrations, decreasing regional concentrations by no more than 5% and by less than 0.5% over most of the globe, assuming direct replacement of sea salt aerosol with organic aerosol. The decrease in CCN concentrations results from the fact that the decrease in particle solute concentration outweighs the organic surfactant effects. The low sensitivity of CCN(0.2%) to the marine organic emissions is likely due to the small compositional changes: the mass fraction of OA in accumulation mode aerosol increases by only ~15% in a biologically active region of the Southern Ocean. To test the sensitivity to uncertainty in the sea spray emissions process, we relax the assumption that sea spray aerosol number and mass remain fixed and instead can add to sea spray emissions rather than replace existing sea salt. In these simulations, we find that marine organic aerosol can increase CCN by up to 50% in the Southern Ocean and 3.7% globally during the austral summer. This vast difference in CCN impact highlights the need for further observational exploration of the sea spray aerosol emission process as well as evaluation and development of model parameterizations.

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Global scale emission and distribution of sea-spray aerosol: Sea-salt and organic enrichment

Atmospheric Environment ◽

10.1016/j.atmosenv.2009.11.013 ◽

2010 ◽

Vol 44 (5) ◽

pp. 670-677 ◽

Cited By ~ 148

Author(s):

E. Vignati ◽

M.C. Facchini ◽

M. Rinaldi ◽

C. Scannell ◽

D. Ceburnis ◽

...

Keyword(s):

Global Scale ◽

Sea Salt ◽

Organic Enrichment ◽

Sea Spray ◽

Sea Spray Aerosol

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Linking hygroscopicity and the surface microstructure of model inorganic salts, simple and complex carbohydrates, and authentic sea spray aerosol particles

Physical Chemistry Chemical Physics ◽

10.1039/c7cp04051b ◽

2017 ◽

Vol 19 (31) ◽

pp. 21101-21111 ◽

Cited By ~ 29

Author(s):

Armando D. Estillore ◽

Holly S. Morris ◽

Victor W. Or ◽

Hansol D. Lee ◽

Michael R. Alves ◽

...

Keyword(s):

Water Uptake ◽

Aerosol Particles ◽

Inorganic Salts ◽

Surface Microstructure ◽

Sea Spray ◽

Sea Spray Aerosol ◽

Complex Carbohydrates

Sea spray aerosol (SSA) particles are mixtures of organics and salts that show diversity in their morphologies and water uptake properties.

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Phase State and Water Uptake Study of Individual Sea Spray Aerosol Particles Using Atomic Force Microscopy

Microscopy and Microanalysis ◽

10.1017/s1431927620021807 ◽

2020 ◽

Vol 26 (S2) ◽

pp. 2500-2502

Author(s):

Chathuri Kaluarachchi ◽

Hansol Lee ◽

Alexei Tivanski

Keyword(s):

Atomic Force Microscopy ◽

Water Uptake ◽

Phase State ◽

Aerosol Particles ◽

Sea Spray ◽

Uptake Study ◽

Force Microscopy ◽

Atomic Force ◽

Sea Spray Aerosol

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Organic Enrichment, Physical Phase State, and Surface Tension Depression of Nascent Core–Shell Sea Spray Aerosols during Two Phytoplankton Blooms

ACS Earth and Space Chemistry ◽

10.1021/acsearthspacechem.0c00032 ◽

2020 ◽

Vol 4 (4) ◽

pp. 650-660 ◽

Cited By ~ 2

Author(s):

Hansol D. Lee ◽

Holly S. Morris ◽

Olga Laskina ◽

Camille M. Sultana ◽

Christopher Lee ◽

...

Keyword(s):

Surface Tension ◽

Phase State ◽

Organic Enrichment ◽

Sea Spray ◽

Core Shell ◽

Phytoplankton Blooms

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Establishing the Impact of Model Surfactants on Cloud Condensation Nuclei Activity of Sea Spray Aerosols

10.5194/acp-2018-207 ◽

2018 ◽

Cited By ~ 1

Author(s):

Sara D. Forestieri ◽

Sean M. Staudt ◽

Thomas M. Kuborn ◽

Katharine Faber ◽

Christopher R. Ruehl ◽

...

Keyword(s):

Surface Tension ◽

Oleic Acid ◽

Palmitic Acid ◽

Water Uptake ◽

Myristic Acid ◽

Cloud Condensation Nuclei ◽

Sea Spray ◽

Condensation Nuclei ◽

Molecular Area ◽

The Impact

Abstract. Surface active compounds present in aerosols can increase their cloud condensation nuclei (CCN) activation efficiency by reducing the surface tension (σ) in the growing droplets. However, the importance of this effect is poorly constrained by measurements. Here we present estimates of droplet surface tension near the point of activation derived from direct measurement of droplet diameters using a continuous flow stream-wise thermal gradient chamber (CFSTGC). The experiments used sea spray aerosol mimics composed of NaCl coated by varying amounts of (i) oleic acid, palmitic acid or myristic acid, (ii) mixtures of palmitic acid and oleic acid, and (iii) oxidized oleic acid. Significant reductions in σ relative to that for pure water were observed for these mimics at relative humidity (RH) near activation (~ 99.9 %) when the coating was sufficiently thick. The calculated surface pressure (π = σH2O − σobserved) values for a given organic compound or mixture collapse onto one curve when plotted as a function of molecular area for different NaCl seed sizes and measured RH. The observed critical molecular area (A0) for oleic acid determined from droplet growth was similar to that from bulk experiments conducted in a Langmuir trough. However, the observations presented here suggest that oleic acid in microscopic droplets may exhibit larger π values during monolayer compression. For myristic acid, the observed A0 compared well to bulk experiments on a fresh subphase, for which dissolution has an important impact. A significant kinetic limitation to water uptake was observed for NaCl particles coated with pure palmitic acid, likely as a result of palmitic acid being able to form a solid film. However, for binary palmitic acid-oleic acid mixtures there was no evidence of a kinetic limitation to water uptake. Oxidation of oleic acid had a minor impact on the magnitude of the surface tension reductions observed, potentially leading to a slight reduction in the effect compared to pure oleic acid. A cloud condensation nuclei (CCN) counter was also used to assess the impact on critical supersaturations of the substantial σ reductions observed at very high RH. For the fatty acid-coated NaCl particles, when the organic fraction (εorg) was > 0.90 small depressions in critical supersaturation were observed. However, when εorg

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