The composition of fragments of bubbles bursting at the ocean surface (original) (raw)
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Journal of Geophysical Research, 2007
1] Breaking waves on the ocean surface produce bubbles that, upon bursting, inject seawater constituents into the atmosphere. Nascent aerosols were generated by bubbling zero-air through flowing seawater within an RH-controlled chamber deployed at Bermuda and analyzed for major chemical and physical characteristics. The composition of feed seawater was representative of the surrounding ocean. Relative size distributions of inorganic aerosol constituents were similar to those in ambient air. Ca 2+ was significantly enriched relative to seawater (median factor = 1.2). If in the form of CaCO 3 , these enrichments would have important implications for pH-dependent processes. Other inorganic constituents were present at ratios indistinguishable from those in seawater. Soluble organic carbon (OC) was highly enriched in all size fractions (median factor for all samples = 387). Number size distributions exhibited two lognormal modes. The number production flux of each mode was linearly correlated with bubble rate. At 80% RH, the larger mode exhibited a volume centroid of 5−mmdiameterandincluded5-mm diameter and included 5−mmdiameterandincluded95% of the inorganic sea-salt mass; water comprised 79% to 90% of volume. At 80% RH, the smaller mode exhibited a number centroid of 0.13-mm diameter; water comprised 87% to 90% of volume. The median mass ratio of organic matter to sea salt in the smallest size fraction (geometric mean diameter = 0.13 mm) was 4:1. These results support the hypothesis that bursting bubbles are an important global source of CN and CCN with climatic implications. Primary marine aerosols also influence radiative transfer via multiphase processing of sulfur and other climate-relevant species.
Marine Chemistry, 1991
A simple aerosol generation rig has been used to investigate the effect of marine organic material on the flux and inorganic particulate enrichment of marine aerosol. Aerosol was generated in the laboratory from UK coastal seawater samples collected on a monthly basis for 1 year, starting February 1988. Initial aerosol generation rates in the laboratory apparatus were typically between 0.3 and 1.0 ml mint , dropping to a baseline value of around 0.1 ml min-~ after a prolonged period of bubbling. Initial aerosol generation rates showed no significant seasonal trend, whereas the total amount of aerosol generated before the rate fell to the baseline reached a plateau at around 60 ml from March to October, a factor of six greater than earlier in the year. Dissolved organic carbon (DOC) and surfactant activity have been measured in seawater from February 1988 to June 1990. The measurements show evidence of seasonal cycles for both determinands. Surfactant activity (expressed in equivalent units of the non-ionic model surfactant Triton X-100) shows a broad peak in the late autumn (2.5-3.2 mg !-t). Peak DOC concentrations were seen in early summer (1.9-3.4 mg C 1-~). It was also found that the surfactant-to-DOC ratio varies seasonally, which suggests that the DOC pool changes through the year. Neither initial aerosol generation rate nor total aerosol generated can be correlated with surfactant activity or DOC, although high surfactant levels can dramatically reduce both. Particulate organic carbon (POC) is highly variable (0.1-14 rag C 1-~), the ratio of POC to particulate loading being more useful. This ratio ranged from 15 to 4000 mg C g-J. Peak values may indicate biological production. Laboratory experiments investigating the aerosol enrichment of 3, 5 and 10 #m diameter synthetic silica particles were carded out at various seawater particulate loadings and surfactant activities. The enrichment factor (EF) of the particles was found to increase approximately linearly with surfactant activity. Particulate loading increases produced only a small increase in the uptake of silica particles in the aerosol, with EF remaining essentially constant. Varying the particle size appeared to have no effect on EF.
Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates
Geophysical Research Letters, 2008
1] The chemical properties of sea-spray aerosol particles produced by artificially generated bubbles using oceanic waters were investigated during a phytoplankton bloom in the North Atlantic. Spray particles exhibited a progressive increase in the organic matter (OM) content from 3 ± 0.4% up to 77 ± 5% with decreasing particle diameter from 8 to 0.125 mm. Submicron OM was almost entirely water insoluble (WIOM) and consisted of colloids and aggregates exuded by phytoplankton. Our observations indicate that size dependent transfer of sea water organic material to primary marine particles is mainly controlled by the solubility and surface tension properties of marine OM. The pattern of WIOM and sea-salt content in the different size intervals observed in bubble bursting experiments is similar to that measured in atmospheric marine aerosol samples collected during periods of high biological activity. The results point to a WIOM/sea-salt fingerprint associated with submicron primary marine aerosol production in biologically rich waters. Citation: Facchini, M. C., et al. (2008), Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates, Geophys. Res. Lett., 35, L17814,
Marine liquid aerosol production from bursting of air bubbles
Journal of Geophysical Research, 1986
The action of wind stress upon the marine surface is responsible for producing air bubbles in seawater through wave breaking. After a given residence time in the sea, bubbles return to the surface, where they burst. The phenomenon of bursting produces two families of droplets: film drops and jet drops. The characteristics of jet drops are far better known than those of film drops. By means of an in-line holographic technique one can obtain experimental results through visualization. One can observe the successive stages of the bursting process of a single bubble in deionized fresh water and in seawater. One visualizes both film drops and jet drops generated by bubbles whose diameter may attain 10 mm. The onset of the bursting phenomenon is clearly shown. Film drop count and size are measurable and may be compared with other available estimates. 1. INTRODUCTION The phenomenon of air bubble bursting at the sea surface has been found to play a fundamental role in air-sea particulate exchanges [see Blanchard and Woodcock,
Distribution of bubbles near the ocean surface
Atmosphere-Ocean, 1986
A model is proposed for the number density of bubbles near the ocean surface when there is an active production of bubbles by entrainment in a breaking wind-wave field. It is argued that the total number density is directly proportional to the work done by the atmosphere on the ocean surface to cause the bubbling and inversely proportional to the volume of the largest cavities. A hypothesis that asserts that all possible configurations of bubble energy distributed with bubble size are equiprobable is shown to be equivalent to assuming that the bubble shattering rate is proportional to individual bubble area. The resulting Weibull distribution for bubble number density is shown to fit available data sets adequately. To account for the depth invariance of the observed maximum number density a scale-dependent but depth-invariant turbulent diffusivity is proposed. RESUME On propose un modèle pour le nombre de la densité des bulles formées près de la surface de l'océan quand elles sont vigoureusement générées par l'entraînement résultant d'un champ de freinage entre le vent et les ondes. On présente l'argument que le nombre total de la densité est directement proportionnel au travail qui résulte de l'action de l'atmosphère sur la surface de l'océan, cause de la formation des bulles, et que ce nombre est inversement proportionnel au volume des plus grandes cavités. On montre que l'hypothèse, voulant que toutes les configurations possibles de l'énergie des bulles réparties selon leurs dimensions soient équiprobables, est équivalente à celle voulant que le taux de désintégration des bulles soit proportionnel à leurs surfaces individuelles. On montre que la distribution de Weibull du nombre de densité des bulles qui en résulte représente adéquatement la série de données disponibles. Une diffusivité turbulente, fonction de l'échelle, mais constante avec la profondeur, est proposée pour expliquer le nombre de densité maximum observé qui demeure constant avec la profondeur.
Bubbles spray aerosols: Certitudes and mysteries
PNAS Nexus
Ocean spray aerosol formed by bubble bursting are at the core of a broad range of atmospheric processes: they are efficient cloud condensation nuclei and carry a variety of chemical, biological, and biomass material from the surface of the ocean to the atmosphere. The origin and composition of these aerosols is sensibly controlled by the detailed fluid mechanics of bubble bursting. This perspective summarizes our present-day knowledge on how bursting bubbles at the surface of a liquid pool contribute to its fragmentation, namely to the formation of droplets stripped from the pool, and associated mechanisms. In particular, we describe bounds and yields for each distinct mechanism, and the way they are sensitive to the bubble production and environmental conditions. We also underline the consequences of each mechanism on some of the many air-sea interactions phenomena identified to date. Attention is specifically payed at delimiting the known from the unknown and the certitudes from t...
Protein and Carbohydrate Exopolymer Particles in the Sea Surface Microlayer (SML)
Frontiers in Marine Science, 2016
Exchanges of matter and energy between ocean and atmosphere occur through the sea surface microlayer (SML). The SML is the thin surface layer of the ocean at the ocean-atmosphere interface that has distinctive physical, chemical and biological properties compared with the underlying water. We measured the concentration of two types of exopolymer particles in the SML and underlying water in the Pacific Ocean off the coast of Oregon (United States) during July 2011. Transparent exopolymer particles (TEP) are defined by their acidic polysaccharide content, whereas Coomassie staining particles (CSP) are composed of protein. TEP and CSP were ubiquitous in the SML. TEP were not significantly enriched in the SML compared with the underlying water. CSP were significantly enriched in the SML, with an enrichment factor (EF) of 1.4-2.4. The distribution of exopolymer particles in the water and microscopic imaging indicated that TEP and CSP are distinct populations of particles rather than different chemical components of the same particles. Dissolved polysaccharides were not enriched in the SML, whereas monosaccharides had an EF of 1.2-1.8. Sampling occurred during the collapse of a diatom bloom, and diatoms were found both in the water column and SML. While there were living diatoms in the samples, most of the diatoms were dead and there were abundant empty frustules covered in layer of TEP. The collapsing diatom bloom was probably the source of exopolymer particles to both the SML and underlying water. Exopolymer particles are a component of the SML that may play a significant role in the marine carbon and nitrogen cycles, and the exchange of material between ocean and atmosphere.
Scientific Reports
Surface ocean bubble-bursting generates aerosols composed of microscopic saltwater droplets, enriched in marine organic matter. The organic fraction profoundly influences aerosols' properties, by scattering solar radiations and nucleating water particles. Still little is known on the biochemical and microbiological composition of these organic particles. In the present study, we experimentally simulated the bursting of bubbles at the seawater surface of the NorthEastern Atlantic Ocean, analysing the organic materials and the diversity of the bacteria in the source-seawaters and in the produced aerosols. We show that, compared with seawater, the sub-micron aerosol particles were highly enriched in organic matter (up to 140,000x for lipids, 120,000x for proteins and 100,000x for carbohydrates). Also DNA, viruses and prokaryotes were significantly enriched (up to 30,000, 250 and 45x, respectively). The relative importance of the organic components in the aerosol did not reflect those in the seawater, suggesting their selective transfer. Molecular analyses indicate the presence of selective transfers also for bacterial genotypes, highlighting higher contribution of less abundant seawater bacterial taxa to the marine aerosol. Overall, our results open new perspectives in the study of microbial dispersal through marine aerosol and provide new insights for a better understanding of climate-regulating processes of global relevance. Marine aerosol is of primary importance for atmospheric processes from local to global scale. It influences the radiation balance of the earth, scattering and absorbing solar radiations either directly or by cloud-condensation nuclei (CCN) and ice-nucleating particles (INPs) formation 1-3. Consequently, changes in marine aerosol abundance and/or composition can significantly influence the global climate 4-7. Marine aerosol is composed of diverse inorganic species, but very complex mixtures of organic compounds also contribute to its overall mass 5, 6. The quantification and characterisation of these organic materials in marine aerosol is at present a largely unexplored issue and a technical challenge, with available information still very scant 8-11. Recent evidences suggest that marine primary aerosols produced by wind-induced bubble bursting in the ocean 12 can be highly enriched in organic matter 5, 11, 13-15 and microorganisms 16-19 , including prokaryotes and viruses 20-22. Microbes in the surface oceans are intermediary sources or sinks for inorganic and organic compounds. Surface marine waters typically display higher microbial abundances and concentrations of dissolved and particulate organic matter than in sub-surface waters (up to 3-orders of magnitude) 11, 20, 23. This material is cycled/ transferred through the food web, and microbes can significantly influence the exchange of organic compounds across the air/water interface and hence the production and composition of marine aerosols 3, 20, 24-27. However,
The organic fraction of bubble-generated, accumulation mode Sea Spray Aerosol (SSA)
Atmospheric Chemistry and Physics, 2010
Recent studies have detected a dominant accumulation mode (∼100 nm) in the Sea Spray Aerosol (SSA) number distribution. There is evidence to suggest that particles in this mode are composed primarily of organics. To investigate this hypothesis we conducted experiments on NaCl, artificial SSA and natural SSA particles with a Volatility-Hygroscopicity-Tandem-Differential-Mobility-Analyser (VH-TDMA). NaCl particles were atomiser generated and a bubble generator was constructed to produce artificial and natural SSA particles. Natural seawater samples for use in the bubble generator were collected from biologically active, terrestrially-affected coastal water in Moreton Bay, Australia. Differences in the VH-TDMAmeasured volatility curves of artificial and natural SSA particles were used to investigate and quantify the organic fraction of natural SSA particles. Hygroscopic Growth Factor (HGF) data, also obtained by the VH-TDMA, were used to confirm the conclusions drawn from the volatility data. Both datasets indicated that the organic fraction of our natural SSA particles evaporated in the VH-TDMA over the temperature range 170-200 • C. The organic volume fraction for 71-77 nm natural SSA particles was 8±6%. Organic volume fraction did not vary significantly with varying water residence time (40 s to 24 h) in the bubble generator or SSA particle diameter in the range 38-173 nm. At room temperature we measured shape-and Kelvin-corrected HGF at 90% RH of 2.46±0.02 for NaCl, 2.35±0.02 for artifical SSA and 2.26±0.02 for natural SSA particles. Overall, these results suggest that the natural accumulation mode SSA particles produced in these experiments contained only a minor organic fraction, which had little effect on hygroscopic growth. Our measurement Correspondence to: Z. D. Ristovski (z.ristovski@qut.edu.au) of 8±6% is an order of magnitude below two previous measurements of the organic fraction in SSA particles of comparable sizes. We stress that our results were obtained using coastal seawater and they can't necessarily be applied on a regional or global ocean scale. Nevertheless, considering the order of magnitude discrepancy between this and previous studies, further research with independent measurement techniques and a variety of different seawaters is required to better quantify how much organic material is present in accumulation mode SSA.
Journal of Geophysical Research: Atmospheres, 2019
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 L air L sw-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.