Continental impact on marine boundary layer coarse particles over the Atlantic Ocean between Europe and Antarctica

Aerosol samples were collected in the Atlantic marine boundary layer between the English Channel and Antarctica during November–December 1999. The composition of coarse (aerodynamic diameter 1–3 μm) individual aerosol particles was studied using the SEM/EDX method. The major particle types observed were fresh sea salt, sea-salt particles reacted partly or totally with sulphuric acid or nitric acid, Mg-sulphate, Ca-sulphate, mixed aluminosilicates and sea salt, aluminosilicates, Ca-rich particles and Fe-rich particles. The relative fractions of sea-salt particles with moderate or strong Cl depletion were high near the coasts of Europe (65–74%) and Northern Africa (44–87%), low far from the coast of Western Africa (10–20%) and very low in remote sea areas between Africa and Antarctica (1%). The Cl depletion was strongest when air masses arrived from the direction of anthropogenic pollution sources. The fractions of Mg-sulphate particles were high (18–25%) in 2 samples near Europe. The Mg-sulphate particles were probably formed as a result of fractional recrystallization of sea-salt particles in which Cl was substituted by sulphate. It remained unclear whether these particles were formed in the atmosphere or during and after sampling. The relative fractions of particles from continental sources were quite low (10–15%) near Europe, very high (25–78%) near the coast of Northwestern Africa and very low in the remote sea areas (0–2%). Most of the continental particles were aluminosilicates and some of them were internally mixed with sea salt. Near the coast of Northwestern Africa, the main source of aluminosilicates was Saharan dust, and near the Gulf of Guinea, emissions from biomass burning were also mixed with aluminosilicates and sea salt.     

Sulfate-coated dust particles in the free troposphere over Japan

Airborne aerosol collections were performed over Wakasa bay (36°00′N, 135°30′E) in March and Kumano open sea (34°00′N, 136°50′E) and Seto (35°10′N, 137°10′E) in July 2001 at altitudes between 1.0 and 5.8 km. The particles were individually analyzed using transmission electron microscopy (TEM). Relatively large mineral-dust (mostly clay) particles were abundant in the March samples. They also dominated in July in the mid-troposphere higher than 4 km altitude, whereas sea salt and ammonium sulfate were more abundant at lower altitudes. Ca-coated grid samples show many traces of aqueous sulfate droplets. The proportions of former sulfate droplets to the total collected particles apparently increased with increasing relative humidity at the time of sampling. TEM analysis revealed that a significant fraction of these former droplets enclose mineral-dust particles as well as sea salt, soot, and fly ash. Some enclose mixtures of mineral-dust, sea-salt, soot, and fly ash particles. The results provide evidence that mineral dust from the Asian continent could acquire coatings of sulfate while being transported in the free troposphere. The mineral-dust particles probably acquired the sulfate coatings either through heterogeneous uptake of gaseous SO₂ and subsequent oxidation or through coagulation with cloud or fog droplets. The presence of the mixed particles in sulfate droplets also indicates that aggregation of particles of different origins occurred through cloud processing. Such sulfate-coated dust particles would affect cloud formation, precipitation, and chemistry of the free troposphere.     

Sulfate-coated dust particles in the free troposphere over Japan

Airborne aerosol collections were performed over Wakasa bay (36°00′N, 135°30′E) in March and Kumano open sea (34°00′N, 136°50′E) and Seto (35°10′N, 137°10′E) in July 2001 at altitudes between 1.0 and 5.8 km. The particles were individually analyzed using transmission electron microscopy (TEM). Relatively large mineral-dust (mostly clay) particles were abundant in the March samples. They also dominated in July in the mid-troposphere higher than 4 km altitude, whereas sea salt and ammonium sulfate were more abundant at lower altitudes. Ca-coated grid samples show many traces of aqueous sulfate droplets. The proportions of former sulfate droplets to the total collected particles apparently increased with increasing relative humidity at the time of sampling. TEM analysis revealed that a significant fraction of these former droplets enclose mineral-dust particles as well as sea salt, soot, and fly ash. Some enclose mixtures of mineral-dust, sea-salt, soot, and fly ash particles. The results provide evidence that mineral dust from the Asian continent could acquire coatings of sulfate while being transported in the free troposphere. The mineral-dust particles probably acquired the sulfate coatings either through heterogeneous uptake of gaseous SO₂ and subsequent oxidation or through coagulation with cloud or fog droplets. The presence of the mixed particles in sulfate droplets also indicates that aggregation of particles of different origins occurred through cloud processing. Such sulfate-coated dust particles would affect cloud formation, precipitation, and chemistry of the free troposphere.     

Chloride and Bromide Loss from Sea-Salt Particles in Southern Ocean Air

Datasets on aerosol composition in Southern Ocean air at Cape Grim and Macquarie Island, and rainwater composition at Cape Grim, have been analysed for sea-salt components in order to test the validity of the multiphase autocatalytic halogen activation process proposed initially by Sander and Crutzen (1996) and developed fully for clean marine air by Vogt et al. (1996). Four distinct datasets from the two locations were analysed. All four datasets provided consistent evidence in support of three predictions of the autocatalytic model: (1) overall Cl- deficits in sea-salt aerosol were small, difficult to quantify against analytical uncertainty and at most a few percent; (2) Br- deficits were large, averaging –30% to –50% on an annual basis, with strong seasonality ranging from about –10% in some winter samples to –80% or more in some summer samples; and (3) the Br- and Cl- deficits were clearly linked to the availability of strong, S-acidity in the aerosol, confirming the importance of acid catalysis to the dehalogenation process.     

The formation of hollow sea-salt particles from the evaporation of drops of seawater

Some non-volatile materials dissolved in water drops will, upon evaporation of the water, produce a hollow shell of the material. Though known for years in the chemical engineering literature, this fact was not appreciated by those working with the marine sea-salt aerosol. Our laboratory experiments show that a majority of seawater drops in free fall in air with a relative humidity less than about 60% evaporate, become salt-saturated, and change phase to produce hollow sea-salt particles. Some hollow salt particles have been found in marine air, though further investigation is required to show the extent of this phenomenon.Expressions have been derived from which both the size of the original drop of seawater and its salt supersaturation at the time of phase change can be calculated from the inner and outer radii of the salt shell. If hollow particles are common in the marine aerosol, then instruments that measure particle size cannot be used to obtain particle mass.     

The size distribution of primary biological aerosol particles with radii > 0.2 μm in an urban/rural influenced region

Primary biological aerosol particles including pollen, spores, plant debris, epithelial cells, bacteria, algae, protozoa and viruses, are an ubiquitous component of the atmospheric aerosol, they are most probably present in all size ranges. Besides their effects on air hygiene and health, biological particles play an important role in cloud physics, for example some bacteria are able to accumulate water and act as ice nuclei. To sample aerosols a two-stage-slit-impactor and a wing-impactor are used to collect particles for a following single particle analysis. The coarse particles are sampled on dyed glycerine jelly. The biological particles become stained and can be distinguished in contrast to the non-dyed particles using a light microscope.The small particles are examined in a scanning-electron-microscope equipped with an energy dispersive X-ray spectrometer after sampling on graphitic foils. Three criteria were used to characterize the particles: the morphology, the elemental composition and the behaviour during the microanalysis.With this method the size distributions of the primary biological aerosol particles were determined in an urban/rural influenced region. Considering all measurements we calculated a mean number concentration of 1.9 cm⁻³ of biological aerosol particles ≈30% of the total aerosol particles. The mean volume concentration was about 15% of the total volume. A model size distribution for primary biological aerosol particles was obtained by performing a non-linear fitting procedure.     

The characterization and distribution of aerosol and gaseous species in the winter monsoon over the western pacific ocean

During the winters of 1981 and 1982, measurements were taken on two Japanese islands of the aerosol and gaseous species which had been carried by northwesterly monsoons over the Pacific Ocean. The aerosols were characterized as sea-salt particles; soil particles, and as particles of sulfate, nitrate, organics and elemental carbon. At Chichi-jima island, which is about 800 km away from the main islands of Japan, it was found that the level of the anthropogenic components of the aerosols was considerably higher than their background level. The mean concentrations of the species on the islands are given in tabular forms. According to a survey made on board a ferry boat, the aerosol and gaseous species were fairly uniformly distributed along the southern coast of the main Japanese islands.     

海盐气溶胶和硫酸盐气溶胶在云微物理过程中的作用

利用大气气溶胶和云分档模式研究海盐气溶胶和硫酸盐气溶胶在云微物理过程中的作用, 计算结果表明:云中液态水含量随高度的分布并不随海盐、硫酸盐的数目以及云团上升速度的变化而变化; 随着云滴数目的增加, 云滴的有效半径会减小; 硫酸盐对云滴数目影响起主导作用, 海盐在水汽相对充足情况下增加了云滴数目, 在水汽相对不足的情况下减少了云滴数目; 硫酸盐粒子浓度特别强的情况下 (人类活动污染比较严重时), 如果水汽相对不足, 云滴数目会明显小于硫酸盐粒子浓度; 而海盐粒子的存在, 加剧了水汽的供应不足, 从而可以在很大程度上进一步降低云滴数目。也就是说, 在有些情况下, 如果不考虑海盐气溶胶的作用, 硫酸盐气溶胶对云特性的影响会被过高估计。     

Nolan–Pollak type CN counters in the Vienna aerosol workshop

Three “standard” Nolan–Pollak (N–P) and a modified N–P design condensation nucleus (CN) counters were included in the Vienna Workshop on Intercomparison of Condensation Nuclei and Aerosol Particle counters. These counters came from diverse backgrounds, namely programs in USA, Europe and Australia. In this work, principles of the operation and previous history of calibration of the N–P expansion counter are briefly reviewed and comparisons between the particular counters used in the workshop are presented and discussed. Counting agreement was found to be very good between the N–P counters, typically better than ±12% for a range of aerosol sizes and compositions from a minimum diameter of 4 nm. The independently calibrated GIV CNC-440 (modified N–P type counter) also agreed well with the N–P counters. The minimum size sensitivity of the N–P counter was examined showing a lower detection limit for insoluble (Ag) particles of around 2.6±0.3 nm diameter.     

Sea-salt optical properties and GCM forcing at solar wavelengths

The single-scattering optical properties of sea-salt solution particles are parameterised as functions of relative humidity for various dry size distributions at solar wavelengths. The accuracy of the parameterisation is typically within 10% as compared to exact Mie calculations. In addition to the optical properties, the growth of the droplet mass ratio and the effective radius of the size distribution are also parameterised in terms of the relative humidity. Two-band models are presented: a four-band model for use in GCMs for climate studies and a 23-band model for use in higher spectral resolution models. The parameterisation is implemented in the Canadian General Circulation Model GCMIII, and an estimate of the first-order globally and yearly averaged solar direct radiative forcing due to sea-salt is estimated to be −0.15 W/m² (cooling). The northern hemisphere forcing is estimated to be −0.11 W/m² and the southern hemisphere is −0.19 W/m². The monthly trends in the forcing for the two hemispheres are presented and discussed. The sensitivity of the forcing to the treatment of the growth of aerosols in the hysteresis region, where aerosol particles are either dry or supersaturated, is investigated along with other sensitivities.     

Distribution of nitrate over sea-salt and soil derived particles — Implications from a field study

A method for determining the distribution of supermicrometer nitrate between size-segregated sea-salt and soil derived particles is presented. The analysis is based on field data from six measurements at a coastal site in southern Finland, and on a theoretical treatment taking into account the transfer of gaseous species onto particle surfaces and their subsequent reaction. Significant amounts of nitrate were found in both the particle types, with the fraction of nitrate associated with soil particles varying from 20–50% in the 1–2 m size to near 90% in particles larger than 10 m. Overall, the nitrate accumulation followed closely the relative abundances of these two particle types. Two overlapping modes in supermicron nitrate mass size distributions could be identified. The lower mode, associated with sea-salt, was located between the surface-area and volume distribution of sodium peaking at about 2–3 m of EAD. The upper mode peaked at 3–5 m and followed more closely the surface-area distribution of calcium in all samples. At our site, the accumulation of nitrate into both particle types was shown to be limited by an effective surface reaction rate rather than by gas-phase diffusion. This rate was estimated to be considerably larger for sea-salt particles. Strong evidence in support of the saturation of nitrate in sea-salt particles were obtained.     

Ceilometer observations of aerosol layer structure above the Petit Lubéron during ESCOMPTE's IOP 2

A modified ceilometer has been used during the second Intensive Observation Period (IOP) of the “Expérience sur Site pour COntraindre les Modèles de Pollution atmosphériques et de Transport d'Émission” (ESCOMPTE) to perform continuous remote observations of aerosol accumulations in the first 3 km of the atmosphere. These observations encompassed an episode of intense particulate and photochemical pollution. The submicronic particles density, measured at an altitude of 600 m, went from a very low point of a few tens of particles per cubic centimeter (at the end of a Mistral episode in the free atmosphere) to a high point of more than 4500 particles per cubic centimeter (when pollutants were trapped by thermal inversions).The main result is that this instrument enables a fine documentation of the mixing layer height and of aerosol particles stratifications and circulation. Airborne aerosol measurements have been made above the mountainous region of Mérindol in order to validate in situ the remote sensing measurements. Ozone measurements near the summit of the mountains as well as in the valley were performed in order to correlate aerosol accumulation and ozone concentration. As a notable example, the two-layer aerosol stratification seen in the first 2 days of IOP 2b in that part of the ESCOMPTE domain confirms the results of another team which used backtrajectories. The low-altitude pollution for this timeframe had a local origin (the Fos industrial area), whereas above 500 m, the air masses had undergone regional-scale transport (from north-eastern Spain).The second major result is the highlighting of a pattern, in sea breeze conditions and in this part of the ESCOMPTE experiment zone, of nocturnal aerosol accumulation at an altitude of between 500 and 2000 m, followed by high ozone concentration the next day.     

Role of the volatile fraction of submicron marine aerosol on its hygroscopic properties

The hygroscopic growth factor (HGF) of 85 nm and 20 nm marine aerosol particles was measured during January 2006 for a three-week period within the frame of the EU FP6 project MAP (Marine Aerosol Production) winter campaign at the coastal site of Mace Head, using the TDMA technique. The results are compared to aerosol particles produced in a simulation tank by bubbling air through sea water sampled near the station, and through synthetic sea water (inorganic salts). This simulation is assimilated to primary production. Aitken and mode particles (20 nm) and accumulation mode particles (85 nm) both show HGF of 1.92 and 2.01 for particles generated through bubbling in natural and artificial sea water respectively. In the Aitken mode, the marine particles sampled in the atmosphere shows a monomodal HGF slightly lower than the one measured for sea salt particles artificially produced by bubble bursting in natural sea water (HGF = 1.83). This is also the case for the more hygroscopic mode of accumulation mode particles. In addition, the HGF of 85 nm particles observed in the atmosphere during clean marine sectors exhibits half of its population with a 1.4 HGF. An external mixture of the accumulation mode marine particles indicates a secondary source of this size of particles, a partial processing during transport, or an inhomogeneity of the sea water composition. A gentle 90 °C thermo-desorption results in a significant decrease of the number fraction of moderately hygroscopic (HGF = 1.4) particles in the accumulation mode to the benefit of the seasalt mode, pointing to the presence of semi-volatile compounds with pronounced hydrophobic properties. The thermo-desorption has no effect on the HGF of bubble generated aerosols, neither for synthetic or natural sea water, nor on the atmospheric Aitken mode, indicating that these hydrophobic compounds are secondarily integrated in the particulate phase. No difference between night and day samples is observed on the natural marine aerosols regarding hygroscopicity, but a more pronounced sensitivity to volatilization of the 1.4 HGF mode in the accumulation mode is observed during the day.     

Climatic responses to the shortwave and longwave direct radiative effects of sea salt aerosol in present day and the last glacial maximum

We examine the climatic responses to the shortwave (SW) and longwave (LW) direct radiative effects (RE) of sea salt aerosol in present day and the last glacial maximum (LGM) using a general circulation model with online simulation of sea salt cycle. The 30-year control simulation predicts a present-day annual emission of sea salt of 4,253?Tg and a global burden of 8.1?Tg for the particles with dry radii smaller than 10?μm. Predicted annual and global mean SW and LW REs of sea salt are, respectively, ?1.06 and +0.14?W?m^?2 at the top of atmosphere (TOA), and ?1.10 and +0.54?W?m^?2 at the surface. The LW warming of sea salt is found to decrease with altitude, which leads to a stronger net sea salt cooling in the upper troposphere. The changes in global mean air temperature by the present-day sea salt are simulated to be ?0.55, ?0.63, ?0.86, and ?0.91°K at the surface, 850, 500a, and 200?hPa, respectively. The emission of sea salt at the LGM is estimated to be 4,075?Tg?year^?1. Relative to present day, the LGM sea salt emission is higher by about 18% over the tropical and subtropical oceans, and is lower by about 35% in the mid- and high-latitudes in both hemispheres because of the expansion of sea ice. As a result of the weakened LGM water cycle, the LGM annual and global mean burden of sea salt is predicted to be higher by 4% as compared to the present-day value. Compared with the climatic effect of sea salt in present day, the sea-salt-induced reductions in surface air temperature at the LGM have similar magnitude in the tropics but are weakened by about 0.18 and 0.14°K in the high latitudes of the Southern and Northern Hemispheres, respectively. We also perform a sensitivity study to explore the upper limit of the climatic effect of the LGM sea salt. We assume an across-the-board 30% increase in the glacial wind speed and consider sea salt emissions over sea ice, so that the model can reproduce the ratio of sea salt deposition between the LGM and present day in the high latitudes of the Southern Hemisphere as suggested by the ice core records. This sensitivity run predicts a global emission of sea salt of 11,941?Tg?year^?1 with a global burden of 20.9?Tg. With such a high loading, sea salt aerosol at the LGM can have a net RE of ?2.28?W?m^?2 at the TOA and lead to an annual and global mean cooling of 1.27°K at the surface.     

Influence of the Surf Zone on the Marine Aerosol Concentration in a Coastal Area

Sea-salt aerosol concentrations in the coastal zone are assessed with the numerical aerosol-transport model MACMod that applies separate aerosol source functions for open ocean and the surf zone near the sea–land transition. Numerical simulations of the aerosol concentration as a function of offshore distance from the surf zone compare favourably with experimental data obtained during a surf-zone aerosol experiment in Duck, North Carolina in autumn 2007. Based on numerical simulations, the effect of variations in aerosol production (source strength) and transport conditions (wind speed, air–sea temperature difference), we show that the surf-zone aerosols are replaced by aerosols generated over the open ocean as the airmass advects out to sea. The contribution from the surf-generated aerosol is significant during high wind speeds and high wave events, and is significant up to 30 km away from the production zone. At low wind speeds, the oceanic component dominates, except within 1–5 km of the surf zone. Similar results are obtained for onshore flow, where no further sea-salt aerosol production occurs as the airmass advects out over land. The oceanic aerosols that are well-mixed throughout the boundary layer are then more efficiently transported inland than are the surf-generated aerosols, which are confined to the first few tens of metres above the surface, and are therefore also more susceptible to the type of surface (trees or grass) that determines the deposition velocity.     

SEM-EDX Characterisation of Tropospheric Aerosols in the Negev Desert (Israel)

Individual aerosol particles collected in the Negev desert in Israel during a summer and winter campaign in 1996–1997 were analysed by scanning electron microscopy with energy-dispersive X-ray analysis. Hierarchical cluster analysis was performed to interpret the data on the basis of particle diameter and composition. Eleven particle classes (groups) provided clues on sources and/or particle formation. The summer samples were enriched in sulphates and mineral dusts; the winter samples contained more sea salts, aged sea salts, and industrial particles. The fine size fraction below 1 m diameter was enriched in secondary particles and showed evidence of atmospheric processing. The secondary sulphate particles were mainly attributed to long-range transport. A regional conversion from calcite to calcium sulphate occurred during summer. Industrial particles originating from local pollution appeared during winter.     

On the formation and growth of atmospheric nanoparticles

In this paper we summarize recent experimental, theoretical and observational results on the formation and growth of atmospheric nanoparticles. During the last years significant progress has occurred to explain atmospheric nucleation and initial steps of the growth. Due to climatic and health effects of fine and ultrafine particles the formation and growth of new aerosol particles is of growing interest. The question “How and under which conditions does the formation of new atmospheric aerosol particles take place?” has exercised the minds of scientists since the time of John Aitken, who in the late 1880s built the first apparatus to measure the number of dust and fog particles. However, only during the last 15–20 years has the measurement technology developed to such a level that size distributions of nanometer-size particles and concentrations of gases participating in particle formation can be measured in the atmosphere. Also from a theoretical point of view atmospheric nucleation mechanisms have not been resolved: several mechanisms such as ion-induced (or ion mediated) nucleation, ternary and kinetic (barrier-less) nucleation have been suggested. In the most recent theory, the activation of existing neutral and/or ion clusters has been suggested.     

Analytical electron microscope studies of size-segregated particles collected during AGASP-II,flights 201–203

Cascade impactor samples were collected over the Alaskan Arctic during the first three research flights of AGASP-II. These samples were analyzed using analytical electron microscopy to determine the morphology, mineralogy and elemental composition of individual particles. For analytical considerations, a typical impactor sample was run for approximately 20 min, thus giving excellent time resolution of discrete events.Samples collected during flights 201 and 202 consisted of stratospheric aerosol and lower-altitude haze samples. Stratospheric samples were characterized by moderate loadings of H₂SO₄ droplets with relatively few particles of other types. Samples collected in tropospheric haze layers generally exhibited light-to-moderate particle loadings. H₂SO₄ was again the most prevalent species, with crustal and anthropogenic particles also observed. One sample taken over south-central Alaska near the end of flight 203 showed high concentrations of solid crustal particles, with relatively little associated H₂SO₄. Giant particles larger than 5 m were occasionally observed in this aerosol. The composition of this material closely matches that of bulk ash from the Mt. Augustine volcano, which erupted 9–13 days before collection of this sample. This brings forth the possibility that pockets of ash-rich aerosol existed over parts of south and central Alska during the AGASP-II field mission. There is no evidence that these volcanic aerosols were present in the AGASP study area north of the Brooks Range.     

Single Particle Characterisation of the Aerosol in the Marine Boundary Layer and Free Troposphere over Tenerife, NE Atlantic, during ACE-2

In the framework of the 2nd Aerosol Characterization Experiment (ACE-2), in June and July 1997, size segregated samples were collected for single particle analysis on the island of Tenerife, in both the marine boundary layer (MBL) and the free troposphere (FT), to study the characteristics of the North Atlantic aerosol. A systematic assessment was made of the aerosol under background conditions and when the environment was perturbed by European emissions and/or Saharan dust. The aerosol particles were analysed by automated and manual SEM-EDX, followed by cluster analysis to identify the different particle types and their abundance. Basing on back trajectory calculations, particle numbers and volume concentrations, different periods can be identified regarding the origin of the sampled air masses. In the FT, the air masses were classified as clean Atlantic, Saharan dust from Africa or pollution from Europe. In the MBL, air masses were classified as clean, polluted or perturbed by emissions from Europe. For both the FT and MBL samples, the main changes in chemical composition were observed between the fine and coarse mode aerosol. The FT fine mode aerosol is dominated by S-poor aluminosilicates (62%) in the event of the dust samples or sulphates, carbonaceous particles (20%) and S-rich aluminosilicates (46%) in the polluted samples. For the larger fractions, a strong decreasing trend was observed for the sulphates (less than 20%) and carbonaceous particles (10%) in the polluted samples. The MBL fine mode was completely dominated by S-rich particles (polluted 55% and perturbed 59%), and to a lesser extent, carbonaceous and aged sea salt particles. In the coarse mode, the polluted air mass is dominated by sea salt particles (62%). Contrary to the fine fraction, the polluted air mass in the coarse fraction contained 5.3% of S-rich particles. The combined interpretation of the data from the analysis of size-fractioned particles and the calculated backward trajectories for air masses coming from Europe, Africa and the Atlantic, results in better insights on aerosol chemistry, especially for the comparison of the particle composition in the FT and the MBL.     

Microhydrodynamics of flotation processes in the sea surface layer

The uppermost surface of the ocean forms a peculiarly important ecosystem, the sea surface microlayer (SML). Comprising the top 1–1000 μm of the ocean surface, the SML concentrates many chemical substances, particularly those that are surface active. Important economically as a nursery for fish eggs and larvae, the SML unfortunately is also especially vulnerable to pollution. Contaminants that settle out from the air, have low solubility, or attach to floatable matter tend to accumulate in the SML.Bubbles contribute prominently to the dynamics of air–sea exchanges, playing an important role in geochemical cycling of material in the upper ocean and SML. In addition to the movement of bubbles, the development of a bubble cloud interrelates with the single particle dynamics of all other bubbles and particles. In the early sixties, several in situ oceanographic techniques revealed an “unbelievably immense” number of coastal bubbles of radius 15–300 μm. The spatial and temporal variation of bubble numbers were studied; acoustical oceanographers now use bubbles as tracers to determine ocean processes near the ocean surface. Sea state and rain noises have both been definitively ascribed to the radiation from huge numbers of infant micro bubbles [The Acoustic Bubble. Academic Press, San Diego].Our research programme aims at constructing a hydrodynamic model for particle transport processes occurring at the microscale, in multi-phase flotation suspensions. Current research addresses bubble and floc microhydrodynamics as building blocks for a microscale transport model. This paper reviews sea surface transport processes in the microlayer and the lower atmosphere, and identifies those amenable to microhydrodynamic modelling and simulation. It presents preliminary simulation results including the multi-body hydrodynamic mobility functions for the modelling of “dynamic bubble filters” and floc suspensions. Hydrodynamic interactions versus spatial anisotropy and size of particle clouds are investigated.