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PRIMARY MARINE AEROSOL PRODUCTION:
STUDIES USING BUBBLE-BURSTING EXPERIMENTS
Kim A. H. Hultin
Primary Marine Aerosol Production:
Studies using bubble-bursting experiments
Kim A. H. Hultin
©Kim Hultin, Stockholm 2010
Cover picture by Lotta Hultin
ISBN 978-91-7447-159-5
Printed in Sweden by US-AB, Stockholm 2010
Distributor: Department of Applied Environmental Science
List of papers
This thesis is based upon the following papers, referred to in the following text by their Roman numerals.
I.
Hultin, K. A. H., Nilsson, E. D., Krejci, R., Mårtensson,
E. M., Ehn, M., Hagström, Å., and G. de Leeuw (2010). In
situ laboratory sea spray during the Marine Aerosol Production 2006 cruise on the northeastern Atlantic Ocean, J.
Geophys. Res., D06201, doi:10.1029/2009JD012522. Reproduced with permission of American Geophysical Union.
II.
Hultin, K. A. H., Krejci, R., Pinhassi, J., GomezConsarnau, L., Mårtensson, E. M., Hagström. Å., and E. D.
Nilsson (2010). Aerosol and bacterial emissions from Baltic Sea water, Atmos. Res.,
doi: 10.1016/j.atmosres.2010.08.018. Reprinted with permission from Elsevier.
III.
Hultin, K. A. H., Zábori, J., Krejci., R., Ekman, A.,
Mårtensson, E. M., and E. D. Nilsson (2010). Volatility
properties and mixing state of submicron primary marine
aerosol from Arctic seawater near Svalbard. Manuscript.
IV.
Nilsson, E. D., Hultin, K. A. H., Mårtensson, E. M., Hagström, Å., Rosman, K., and R. Krejci (2010). Baltic sea
spray emissions: in situ eddy covariance fluxes v.s. simulated tank sea spray. Submitted to Journal of Geophysical
Research-Atmospheres.
Statement
I, Kim A. H. Hultin, made the following contributions to the papers
presented here:
Paper I
I was responsible for the laboratory aerosol measurements, analysis of
the aerosol data and was the main contributor to the writing. Bubble
spectra measurements were made by Leo Cohen, TNO, and ambient
aerosol measurements by Mikael Ehn, FMI, both analyzed by Douglas
Nilsson.
Paper II
I conducted most of the aerosol measurements, analyzed the aerosol
data and took the lead role in authoring the paper. Biological sampling
was made by Laura Gomez-Consarnau and Jarone Pinhassi.
Paper III
I analyzed the data and had the leading role in authoring the paper.
The measurements were made by Julia Zábori and Radovan Krejci.
Paper IV
Douglas Nilsson performed and analyzed the eddy covariance data,
while I made the laboratory aerosol measurements and analyses and
performed the aerosol back trajectories. I contributed to writing the
paper, although Douglas Nilsson had the leading role.
Contents
1
Introduction ....................................................................................... 11
2
Aerosol and climate ......................................................................... 12
3
4
5
2.1
Direct and semi-direct aerosol effects ...................................................... 13
2.2
Indirect aerosol effects ................................................................................ 13
Primary marine aerosol ................................................................... 15
3.1
Production mechanism................................................................................. 15
3.2
Source functions ........................................................................................... 17
3.3
Primary marine aerosol number size distribution ................................... 18
3.4
Composition ................................................................................................... 20
3.4.1
Sea salt ................................................................................................ 20
3.4.2
Organic compounds ........................................................................... 20
3.4.3
Bacteria ................................................................................................ 21
Aims of the thesis ............................................................................ 23
4.1
General aims.................................................................................................. 23
4.2
Specific aims .................................................................................................. 23
Methods .............................................................................................. 25
5.1
Aerosol size distributions .................................................................. 26
5.1.2
Volatility properties and mixing state ............................................ 27
5.1.3
Bacterial enumeration ....................................................................... 27
5.1.4
Bubble measurements ...................................................................... 27
5.2
6
Laboratory-made aerosol ............................................................................ 26
5.1.1
Ambient aerosol fluxes – eddy covariance ............................................... 28
Summary of papers in the thesis ................................................. 29
6.1
Paper I: northeastern Atlantic Ocean ....................................................... 29
6.2
Paper II: Baltic Sea ...................................................................................... 29
6.3
Paper III: Arctic Ocean ................................................................................ 30
6.4
Paper IV: Baltic Sea, eddy covariance method ....................................... 31
7
Concluding remarks and outlook .................................................. 32
8
Acknowledgements .......................................................................... 36
9
References ......................................................................................... 38
1 Introduction
This thesis is devoted to the atmospheric constituents known as aerosol, more specifically to marine aerosol. Aerosol is defined as liquid
or solid particles suspended in a gas, such as air. Atmospheric aerosol
can be of both natural (e.g., from volcanic eruptions, wind-blown soil
dust or sea spray from the world‟s oceans) and anthropogenic (e.g.,
from combustion of fossil fuels or biomass, or from agriculture) origins, and spans sizes from a few nanometers to tenths of micrometers.
The size of these particles strongly influences both their atmospheric
lifetime and their optical properties (Brasseur et al., 2003; Seinfeld
and Pandis, 2006).
Aerosol particles are defined as primary or secondary particles
depending on how they are produced. While primary aerosol particles
are emitted directly into the atmosphere (such as in the case of sea
spray or wind-blown dust), secondary aerosols are formed in the atmosphere via gas-to particle processes known as nucleation and new
particle formation (Kulmala et al., 2004). Atmospheric aerosols are
also transformed during their atmospheric lifetime by microphysical
processes such as condensation, coagulation and cloud processes, and
removed from the atmosphere via dry- or wet deposition mechanisms.
For example dry deposition by turbulent eddies or wet deposition by
precipitation (Seinfeld and Pandis, 2006).
The summary of the thesis is meant to give a background to the
subject of marine aerosol and their effect on the Earth‟s climate. In
addition, the summary serves the purpose of giving an overview on
how marine aerosol can be studied. The main findings of the four papers included in the thesis, and some thoughts regarding improvements in future investigations of this natural source of atmospheric
aerosol are also briefly presented.
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2 Aerosol and climate
In Figure 1, a summary of the present state of knowledge regarding
the factors underlying the radiative forcing of the Earth‟s climate is
presented. According to the IPCC report from 2007 the scientific consensus is that the observed global warming, with a high degree of
probability, is anthropogenically forced (IPCC, 2007).
Greenhouse gases warm the lower atmosphere since they are
nearly transparent to incoming solar radiation but absorb and re-emit
Figure 1. Global average radiative forcing (RF) estimates and ranges in 2005 for
anthropogenic carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and other
important agents and mechanisms, together with the typical geographical extent
(spatial scale) of the forcing and the assessed level of scientific understanding (LOSU). The net anthropogenic radiative forcing and its range are also shown. These
require summing asymmetric uncertainty estimates from the component terms, and
cannot be obtained by simple addition. Additional forcing factors not included here
are considered to have a very low LOSU. Volcanic aerosols contribute an additional
natural forcing but are not included in this figure due to their episodic nature. The
range for linear contrails does not include other possible effects of aviation on cloudiness (adopted from the fourth assessment report of the IPCC, Summary form policymakers 2007).
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outgoing long wave radiation. The anthropogenic aerosol on the other
hand, has a net cooling effect of almost the same magnitude as anthropogenic carbon dioxide, hence counteracting the warming induced
by the greenhouse gases. Atmospheric aerosols therefore have the
ability to mask part of the global warming signal. The effect is however limited; the longest lifetime of aerosol particles in the atmosphere
is on the order of weeks, while the effective lifetime of carbon dioxide
is on a century time scale (Seinfeld and Pandis, 2006). Aerosol affects
the climate system through radiative forcing in many ways, often categorized into direct and indirect effects.
2.1 Direct and semi-direct aerosol effects
Depending on their optical properties, aerosol can either directly scatter or absorb solar radiation, and thereby alter the radiative balance.
The aerosol direct effect is most efficient for particles with diameters
between 0.2 and 2 m, which correspond to the power peak in the
solar spectrum (Lewis & Schwartz, 2004).
Absorption of solar radiation by aerosol particles heats the air
mass, reduces relative humidity and increases the static stability relative to the surface. When absorbing aerosol is part of a cloud, their
presence may cause evaporation of cloud droplets and a reduced cloud
cover, an effect called the semi-direct effect. This leads to a positive
forcing, amplifying the warming influence of absorbing aerosol. Conversely, if a layer of absorbing aerosol particles is present above a
cloud, the increased static stability may lead to a lower entrainment
rate and a shallower and moister boundary layer. Absorbing aerosol
above clouds may thus lead to a negative forcing instead (Ackerman
et al., 2000; Johnson et al., 2004).
2.2 Indirect aerosol effects
The aerosol indirect effect regards the mechanisms by which aerosols
modify the microphysical properties of clouds, hence the amount, lifetime and radiative effects of clouds.
Aerosol particles have the potential to serve as cloud condensation nuclei (CCN). The brightness of a cloud is determined by available CCN, an effect known as the Twomey effect (Twomey, 1977). An
increase in CCN causes an increase in the droplet number concentra13
tion and a decrease of mean droplet size in a cloud of nearly constant
liquid water content. More droplets lead to an increased reflection of
solar radiation from the formed cloud, and thus lead to a climate cooling.
Assuming that the amount of water in the cloud is not altered by
the increase of CCN, the decrease in mean radius of the cloud droplets
and the more narrow cloud droplet size distribution results in lower
precipitation efficiency (Rosenfeld, 2006; Freud et al., 2008). Not only does this lead to suppression of precipitation in affected clouds, it
can also lead to an increased lifetime of the clouds (called the Albrecht effect, Albrecht (1989)) – and an increase in cloudiness. This
further increases the reflection of solar radiation back to space.
Aerosol particles can also act as ice nuclei. The glaciation effect
refers to an increase in ice nuclei resulting in rapid glaciation of a supercooled water cloud due to the difference in vapor pressure over ice
an water. The ice crystals quickly reaches precipitation size with the
potential of turning a non-precipitation cloud into a precipitation
cloud, decreasing the cloud lifetime which lead to a positive forcing
(Lohmann and Feichter, 2005).
Also included as aerosol indirect effects are the thermodynamic
effect, the riming indirect effect and the surface energy budget effect
(see Lohmann and Feichter (2005) for a review on the subject). The
first one refers to that the smaller cloud droplets induced by increased
aerosol concentration can delay the onset of freezing, the second that
the smaller cloud droplets can decrease the riming efficiency, while
the surface energy budget effect deals with the overall effect that an
increased amount of aerosol and increased cloud optical thickness
decreases the net surface solar radiation.
How efficiently aerosol particles form cloud droplets depend on
their size, chemical composition and on cloud dynamics, in particular
the water vapor super saturation in the cloud. Approximately the same
particle sizes of aerosol are important both for the direct and indirect
effects (Raes et al., 2000; McFiggans et al., 2006).
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3 Primary marine aerosol
About 70% of the Earth‟s surface is covered by oceans, and marine
aerosol represents a significant fraction of aerosols found in the atmosphere. In clean marine conditions, the marine aerosol number
concentration is about 100-400 particles cm-3. This is a low value
compared to for example rural sites (concentrations about 2000-10
000 cm-3), or polluted urban sites (up to 4×106 cm-3, Seinfeld and Pandis (2006)). Still, when considering aerosol mass, the flux of sea salt
particles is the largest natural aerosol source, with an estimated global
mass flux of around 1×1016 g yr-1 (Gong et al., 1997; Grini et al.,
2002).
Not only are sea salt particles the single most important factor
controlling the scattering of solar radiation near the surface over open
ocean (Haywood et al., 1999). Sea salt particles play a significant role
in cloud microphysics and chemistry, especially in marine stratocumulus clouds (O‟Dowd et al., 1999), and can also provide a substantial
sink for atmospheric trace gases, both natural and man-made
(O‟Dowd et al., 2000). However, primary marine aerosol does not
exclusively consist of sea salt. To refer to primary marine aerosol
without specifying its composition the term sea spray can also be
used.
3.1 Production mechanism
Primary marine aerosol particles mainly reach the atmosphere when
bubbles burst as a result of waves breaking at the ocean surface. Minor contributions can come from the impact of rain- or snowfall on a
water surface (Blanchard, 1983) or by supersaturation of oxygen
through extensive photosynthesis by marine algae (Wania et al.,
1998). The bubble-bursting process is in general assumed to result in
three different kinds of droplets. Film droplets are considered to be
fragments of the disintegrated film caps of the bursting bubble. Jet
droplets reaches the atmosphere from the collapsing bubble cavity
after the rupture of the bubble film (Blanchard, 1963), as illustrated in
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Figure 2. When the wind stress is sufficiently great, droplets called
spume droplets are torn directly from the wave crest (Monahan et al.,
1983). These droplets are projected nearly horizontally, and are
thought to be larger than most jet- and film droplets.
Figure 2. The bubble-bursting mechanism. a) An air bubble at an air-water interface. b) The production of jet and film droplets from a bursting bubble. From Blanchard (1983).
Primary film droplets are produced when the bubble film shatters, and
are ejected in all directions. Secondary film droplets appear to be produced from impaction of the larger, downward moving primary film
droplets (Spiel, 1998). Compared to film droplets, the number of the
vertically rising jet droplets is small and their size generally larger.
While aerosol from jet droplets is mainly found in the supermicrometer size range, the submicrometer aerosol is considered to be mainly
composed of film droplets (Cipriano and Blanchard, 1981; Afeti and
Resch, 1990; Reinke et al., 2001). The bubbles producing the majority
of the film droplets are expected to be rather large in this context;
larger than 2-2.5 mm in diameter (Blanchard and Syzdek, 1988; Resch
and Afeti, 1992). What is described above is the commonly accepted
picture, although it may not be the complete picture. For example,
Bird et al. (2010) found evidence that 5 mm-bubbles also can also
create numerous smaller daughter bubbles as the curved film of the
ruptured bubble can fold and entrap air as it retreats, which result in
jet droplets.
All droplets quickly undergo evaporation in the atmosphere as the
relative humidity is lower at higher altitudes than directly over seawater (the relative humidity is on average about 80% in the atmosphere,
compared to about 97% directly over seawater (O‟Dowd and de
Leeuw, 2007)). As a rule of thumb for oceanic conditions, the aerosol
radius at formation approximately equals two times the radius at
16
RH=80%, and 4 times the dry radius, which is what commonly is
measured during aerosol sampling: r02r804rdry (Lewis and Schwartz,
2004).
As bubbles rise to the surface, surface active material in the bulk
water aggregates to the walls of the bubbles (Scott, 1975; Hejkal et al.,
1980). The organic chemicals are formed within the water body or
from materials carried to the water surface by winds, air currents and
precipitation (Wotton and Preston, 2005). The bubble upwelling region causes an outflow of water and can result in the removal of the
surface microlayer above the rising bubble plume (Blanchard, 1983).
At rupture, the collected material from both the bulk water and the
surface microlayer is ejected into the air to form primary marine aerosol particles (Blanchard and Syzdek, 1982; Smith et al., 1993; Clarke
et al., 2003; Cavalli et al., 2004). The result is a wind driven source of
aerosol particles consisting largely of sea salt and organic compounds
(Monahan et al., 1983; O‟Dowd et al., 1997; Nilsson et al., 2001).
The different chemical compounds in the aerosol can either be internally mixed with sea salt (i.e. in the same particle), or externally
mixed (as separate particles).
3.2 Source functions
A source function attempts to describe the surface flux of sea spray
aerosol; the number, size and composition of particles produced per
unit surface area and time. It is a key component required for modeling of the marine aerosol. Available source functions have been determined using different methods and physical principles. Most of
them are derived using indirect methods to infer the rate of production
as a function of wind speed, for example the whitecap method used by
Mårtensson et al. (2003). The surface manifestation of a bubble plume
is a whitecap, which can be parameterized as a function of environmental parameters such as wind speed, atmospheric thermal stability
and water temperature (Monahan and O‟Muircheartaigh, 1986). In the
whitecap method, parameterizations of the fraction whitecap cover
from field experimental data are combined with laboratory measurements of sea spray production rates per whitecap area.
In recent years attempts have been made to improve the sea spray
source functions by direct flux measurements using the eddy covariance method (see section 5.2). This includes both size resolved aerosol fluxes and bulk divisions between non-volatile (presumably main17
ly sea salt) and volatile compounds by heating the aerosol (Nilsson et
al., 2001, 2007; Geever et al., 2005; Norris et al., 2008, Paper IV).
The advantage of using a direct method is that all particles within the
detectable size range can be measured, and hence there are no limitations resulting from bubble-mediated production (O‟Dowd and de
Leeuw, 2007). Some of the available submicrometer aerosol source
functions are displayed in Figure 3. The results from these modern
source functions are now approaching each other in the range 0.1-1
m, in good agreement compared to the variations of up to 8 orders of
magnitude seen in the comparison of Andreas (1998).
Figure 3. Aerosol number emission flux size distributions for sea salt applied to a
wind speed of 9.8 ms-1. From Nilsson et al. ( 2007).
3.3 Primary marine aerosol number size distribution
Aerosol particles in the marine boundary layer are usually grouped by
the diameters of the particles, and are characterized by four modes:
nucleation mode (Dp < 0.02 m), Aitken mode (Dp = 0.02 – 0.1 m),
accumulation mode (Dp = 0.1 – 0.6 m), and coarse mode (Dp > 0.6
m, Seinfeld and Pandis (2006)). While the coarse mode particles
typically represent up to 95% of the total mass of the aerosol particles,
it may only represent about 5-10% of the particle number. These
names are not commonly used regarding laboratory produced sea
18
spray, as they originate from ambient observations (accumulation
mode refers for example to those particle sizes that have the longest
lifetime in the atmosphere), and results partly from airborne
processing and aging of the aerosol.
Until a decade ago, primary marine aerosol studies were mainly
focused on supermicrometer aerosol particles due to their effect on
atmospheric transmission and the sea-air transfer of heat, mass and
water vapor (e.g., Andreas, 1998), for which aerosol mass is a key
parameter. With the realization of the role aerosols play in the climate
of the Earth (see section 2), focus shifted to studies of sea spray submicrometer particles over the size range from roughly 0.01 m to 1
m.
Several studies on laboratory-generated sea spray aerosol have
been conducted over the last few years (e.g., Mårtensson et al., 2003;
Sellegri et al., 2006; Keene et al., 2007; Tyree et al., 2007; Fuentes et
al., 2010; Papers I-IV), a few of which are presented in Figure 4. In
general, they point to a dominant mode around 0.1-0.2 m, a size
range that is climatically important because it means sea spray aerosol
can potentially account for a significant fraction of CCN, particularly
under high wind conditions (Figure 4).
Figure 4. Aerosol number size distribution generated from artificial bubbles: northeastern Atlantic (circles on thick line, Paper I), Bermuda Institute for Ocean
Sciences (thin line, Keene et al. (2007)), filtered seawater from Scripps Institute of
Oceanography Pier (dashed curve, Tyree et al. (2007)), artificial seawater
(dashed/dotted line, Mårtensson et al. (2003)), and artificial seawater from Sellegri
et al. (2006) (from the equation and parameters included in Table 1 in Sellegri et al.
(2006) and scaled by 105 for comparative purposes, dotted line). From Paper I.
19
Discrepancies between studies can relate to the use of different methods, different waters, and measurement artifacts. For example, diffusion losses in the sampling systems for the smallest particles (Paper
I).
3.4 Composition
3.4.1 Sea salt
By definition, salinity is a dimensionless number based on water conductivity. A typical value for the majority of the world oceans is 35
psu (practical salinity units), making sea salt a natural part of the primary marine aerosol. Most of the dissolved material in seawater consists only of a few ionic species together forming sea salt: Cl-, Na+,
Mg2+, SO42-, Ca2+, K+ and HCO3-. The ratios of these species are quite
constant throughout the oceans (Lewis and Schwartz, 2004; Seinfeld
and Pandis, 2006).
Marine aerosol in the Aitken, accumulation and coarse modes has
been observed to consist in part of sea salt (e.g., O‟Dowd and Smith,
1993; Murphy et al., 1998; Clarke et al., 2003), with the supermicrometer marine aerosols consisting almost exclusively of sea salt (Cavalli et al., 2004; O‟Dowd et al., 2004; Facchini et al., 2008).
3.4.2 Organic compounds
A large part of the oxygen in the atmosphere is produced by marine
organisms, mostly phytoplankton. All living organisms are made of
carbon and all cells are enclosed by thin plasma membranes. These
biological membranes are exceedingly complex structures composed
of a mixture of lipids, proteins, and carbohydrates. Both the lipids and
the proteins are amphipathic, they consist of a hydrophilic and a hydrophobic end. The lipid molecules spontaneously aggregate to bury
their hydrophobic tails in the interior and expose their hydrophilic
heads as bimolecular sheets, bi-layers. As cells die, they decompose
and the hydrophobic cellular constituents rise toward the ocean‟s surface where they accumulate (Karp, 1999; Alberts et al., 2002). Organic molecules that contain a polar group (in the case of lipids, the hydrophilic head) generally reduce the surface tension of water and are
commonly called “surface active” or “surfactants” (Gill et al., 1983).
20
Most of the organic matter in seawater originates from phytoplankton production (Biddanda and Benner, 1997). The concentrations
of dissolved and particulate organic matter, DOM and POM, vary
greatly with location, time and depth (Millero, 2005).
It is currently accepted that sea spray produced from biologically
active water not only include organics, the organic fraction can dominate over sea salt mainly toward smaller submicrometer particles. Previous studies have shown that the organic mass fraction increases with
decreasing sizes, both in ambient measurements (Cavalli et al., 2004;
O‟Dowd et al., 2004) and from laboratory investigations (Facchini et
al., 2008). The fraction of organic material has been shown to vary
between seasons and locations. In highly productive north Atlantic
waters, Facchini et al. (2008) found up to 77% of the total carbon by
mass in individual submicrometer diameter size fractions to be organic carbon, while Modini et al. (2010) found only about 4% by mass
in submicrometer aerosol coastal water east of Australia.
As many marine-derived organic compounds suppress surface
tension, their incorporation into marine aerosols may reduce the super
saturation required to activate particles into cloud droplets (e.g., Facchini et al., 2000; Decesari et al., 2005).
3.4.3 Bacteria
Marine bacteria play a vital role in marine surface waters. It has for
example been recognized that they consume up to 50% of the photosynthetically produced organic matter in the ocean (Azam et al., 1983;
Azam, 1998). The abundance of bacteria in surface waters ranges
from about 105 to 107 cm-3, and is significantly positively correlated
with chlorophyll concentrations, and thus with phytoplankton biomass
(Azam et al., 1983; Linley et al., 1983).
A recent study by Ceburnius et al. (2008) concluded that water insoluble organic carbon in submicrometer marine aerosol had a primary source at the sea surface, while water soluble organic carbon
pointed to a production via secondary processes. Bacteria in the marine atmosphere contribute to this insoluble organic aerosol component, and several studies support the conclusion that their main means
of conveyance to the atmosphere is via the bubble-bursting process
(e.g., Blanchard and Syzdek, 1970; Marks et al., 2001; Aller et al.,
2005; Paper II).
Some marine bacterial species have been found to be efficient ice
nuclei (e.g. Maki et al., 1974; Schnell, 1977). At sub-zero tempera21
tures warmer than -40 ºC, aerosol particles in clouds initiates freezing
through the heterogeneous nucleation of ice directly from water. The
most active naturally occurring ice nuclei (IN) are of biological origin
and have the capacity to catalyze freezing at temperatures as high as 2 ºC (Maki et al., 1974). This capacity and the formation of ice crystals in clouds can influence precipitation formation (e.g., Christner et
al., 2008; Pratt et al., 2009). Thus, these processes couple together
marine-derived organic material, cloud microphysics, and climate into
a complex feedback system.
22
4 Aims of the thesis
4.1 General aims
As seen in Figure 1, the level of scientific understanding regarding the
total effect aerosol have on climate is for the most part considered
low, and the uncertainty regarding the magnitude of the aerosol effect
is high. In order to acknowledge and understand the anthropogenic
impact on climate, we have to understand the underlying natural
processes and describe them as accurately as possible. Because of the
large extent of the world‟s oceans, marine aerosol is one of the most
important components of the climate system. Although sea salt is an
important part of marine aerosol with respect to mass, there is increasing evidence of a large organic fraction of the submicrometer marine
aerosol. This is likely to have significant impact on marine aerosol
optical properties and marine cloud formation. Climate models so far
include only sea salt, however typically not the entire submicrometer
size range. The general aims of this thesis were to characterize the
emission of primary marine aerosol particles down to about 0.02 m,
and to quantify the organic fraction.
4.2 Specific aims
To test if laboratory made bubble-bursting produces a realistic bubble
spectrum, and thus a realistic aerosol spectrum (Paper I).
To see if there are additional parameters affecting the aerosol production apart from wind speed (Papers I and II).
To investigate the link between surface water chlorophyll concentration and aerosol number concentration (Paper I).
To determine how effectively marine bacteria use the bubble-bursting
mechanism (Paper II).
23
To examine the possibility of a diurnal cycle in aerosol production
(Papers II and IV).
To investigate whether sea salt is externally or internally mixed with
organic material (Papers I, III and IV).
To combine laboratory- and flux measurements in order to improve
the sea spray source function down to submicrometer aerosol size
ranges (Paper IV).
24
5 Methods
Figure 5. The sites used to sample surface seawater in this thesis. A: northeastern
Atlantic, cruise with R/V Celtic Explorer (2006). B: Askö (2005), C: Garpen (2005),
and D: Kongsfjorden, Svalbard (2010). From Google Earth.
Although wind speed is the single dominating factor controlling the
production of sea spray aerosols, other variables such water temperature, oxygen saturation or the presence of surfactants may also be important, however their roles are poorly understood. In order to understand what affects the primary marine aerosol production, laboratory
experiments are necessary since generated fresh primary aerosols can
be analyzed without interference due to modification processes and
without secondary aerosol in the atmosphere involved. In addition,
during laboratory experiments the “wind speed” (bubble production
rate) can be held constant, a process that easily otherwise can obscure
the effects of other parameters. In an experimental container, the effects of the above mentioned parameters and the aerosol mixing state
were the subjects of interest during these studies.
In contrast to laboratory-made aerosol, the eddy covariance technique offers a direct way to measure the magnitude of aerosol net exchange between the surface and atmosphere. However, this method is
limited to size resolved fluxes above about 0.1 m due to slow re25
sponse times of the available instruments. Connecting the eddy covariance results to laboratory-made aerosol, which was here measured
down to 0.02 m, could allow a sea spray source function from 0.02-2
m to be determined.
Surface water from four different locations was investigated (Figure 5). While one site represents open ocean (A, Paper I), the two
Baltic and the Arctic sites are coastal (B and C, Paper II, C, Paper
IV, and D, Paper III). Below follow short descriptions of the principal methods used in this thesis, in addition to continuous measurements
of water properties such as salinity, temperature and dissolved oxygen.
5.1 Laboratory-made aerosol
Previous studies have investigated the primary marine aerosol by using wave tanks (Monahan et al., 1982; Bowyer et al., 1990) atomizers
(e.g., Taketani et al., 2009), aeration through glass frits or diffusers
(Mårtensson et al., 2003; Keene et al., 2007; Tyree et al., 2007), or
water jets (Cipriano and Blanchard, 1981; Facchini et al., 2008). Some
investigators have compared more than one method (Sellegri et al.,
2006; Russell and Singh, 2006; Fuentes et al., 2010). The advantage
of using an impinging jet of water as compared to atomizers or aerations through frits or diffusers is primarily that the air bubble size
spectrum is not monodisperse. Compared to the use of a wave tank,
the water jet apparatus can be of smaller size and still produce a high
number of particles due to large water flows, resulting in high bubble
densities. Here, this technique has successfully been used in a carefully sealed 50 L aquarium bowl or a 20 L polyethylene bottle, producing
only primary marine aerosol.
5.1.1 Aerosol size distributions
To obtain the aerosol size distribution a Differential Mobility Particle
Sizer (DMPS) system together with an Optical Particle Counter (OPC,
GRIMM GmbH 7.309) was used. Combining both instruments results
in a number size distribution of dry diameter Dp = 0.02 - 2.2 m. The
DMPS system consisted of a Differential Mobility Analyzer (DMA,
Stockholm University) and a Condensation Particle Counter (CPC,
TSI 3010) (Papers I-IV).
26
5.1.2 Volatility properties and mixing state
In order to obtain information about the mixing state of the particles, a
Volatility-Tandem Differential Mobility Analyzer (V-TDMA) was
used. Firstly, a DMA (Stockholm University) selected particles of a
specific size range. The particles were then heated in a thermodenuder
(Stockholm University), and the number size distribution of the remaining particles were measured using a second DMA (a copy of the
first one) in combination with a CPC (TSI 3010) with a cut-off of
0.006 m (Paper III).
5.1.3 Bacterial enumeration
Bacterial sampling took place both in seawater (total bacterial numbers and colony-forming bacteria) and in aerosol phase of the laboratory-made aerosol (colony-forming bacteria). While total bacterial
numbers include all bacteria (live or dead) present in the water, colony-forming units (CFU) is a measure of only living bacteria and those
that forms colonies growing on an agar plate. Compared to total bacterial numbers, the viable count is typically less than 0.1% for open
ocean (Kogure et al., 1979) (Paper II).
5.1.3.1
Total bacterial numbers
Seawater samples were fixed with 0.2 m pore-sized filtered formaldehyde (final concentration 4%), stained with Acridine Orange, filtered onto 0.2 m pore-size polycarbonate filters (Poretics, Osmonics
Inc.), and counted by epifluorescence microscopy within 48 hours.
5.1.3.2
Colony-forming units
For seawater samples, 100 ml of 10x and 100x diluted seawater samples on duplicate ZoBell agar plates made with Baltic seawater. CFUs
from the aerosol phase were obtained after filtering 1, 0.75 and 0.5 m3
air from the laboratory tank onto gelatin filters (Sartorius). These filters were transferred onto ZoBell agar plates, which were incubated at
room temperature until colonies were visible (5-10 days). Gelatine
filter controls were made from the tank after each experiment with the
water jet turned off and thus no aerosol production.
5.1.4 Bubble measurements
Subsurface bubble spectra in the size range from 30 to 1000 m were
measured using an optical bubble measurement system (a mini-BMS
27
developed at TNO, the Netherlands, described in Leifer et al. (2003)).
The sensor heads of the system was placed about 4 cm below the water surface, and as the bubbles entered the sample volume by natural
advection, they were imaged by a video camera. After image
processing, the bubble size distribution was calculated (Paper I).
5.2 Ambient aerosol fluxes – eddy covariance
The most direct way of determining the in-situ aerosol flux is the eddy
covariance method, where a net upward flux indicates that particle
emissions dominates over (dry deposition) sinks (Nilsson et al., 2001).
This method includes high-frequency measurements of vertical wind
speed and concentration of aerosol particles, and the calculation of
turbulent fluxes from these parameters (Paper IV).
To obtain size resolved aerosol concentrations, two OPCs were
used (prototypes corresponding to GRIMM model SVC-EDM 265)
sampling with 1 Hz time resolution, where one was heated to 300 °C
in order to separate sea salt from the more volatile species of the aerosol. The three-dimensional wind speed was measured using a Gill Ultrasonic anemometer R3, sampling with 20 Hz time resolution.
28
6 Summary of papers in the thesis
6.1 Paper I: northeastern Atlantic Ocean
This study was made during a cruise over the highly biologically active waters of the northeastern Atlantic in the summer of 2006. The
major scientific goal was to investigate, and possibly parameterize, the
effect of phytoplankton on sea spray production. Chlorophyll was
used as a proxy for this. No direct relation between the produced aerosol number concentration and the level of chlorophyll  in the surface
water was observed on the short time scales investigated during the
cruise (10 min averages). The aerosol number production was negatively correlated with dissolved oxygen in the water (r < -0.6 for particles of dry diameter Dp > 0.2 m). An increased surfactant concentration as a result of biological activity affecting the oxygen saturation
is thought to diminish the particle production.
The enhanced upward mixing of deeper ocean water as a result of
higher wind speed appears to affect the aerosol particle production,
indicating that wind speed influences aerosol production in more
complex ways than simply by increasing the amount of whitecaps.
The different properties of the deeper water masses reaching the surface at high wind speeds may also have the possibility to alter the
aerosol production and composition.
The bubble spectra produced by the jet of seawater was representative of breaking waves at open sea, and the particle number production was positively correlated with increasing bubble number concentration with a peak production of 40-50 particles per bubble.
6.2 Paper II: Baltic Sea
Two coastal sites in the Baltic Sea were used to investigate aerosol
and bacterial emissions from the bubble-bursting process. The aerosol
size distribution spectra from the two sites were similar and conservative in shape where the modes were centered at about 0.2 m dry diameter. A 0.6 m mode was also found, most clearly pronounced at
29
Garpen. This could be a coastal influence as the water at Garpen was
not only sampled near the coast, but also very close to the sea floor.
We found a distinct decrease in aerosol production with increasing water temperature. A clear diurnal cycle in sea spray aerosol production was found as well, anti-correlated both with water temperature
and dissolved oxygen, which to our knowledge has never been shown
before. A link between decreasing aerosol production in daytime and
phytoplankton activity is likely to be an important factor for these results.
Colony-forming bacteria were efficiently transferred to the atmosphere via the bubble-bursting process, with a linear relationship to
their seawater concentration.
6.3 Paper III: Arctic Ocean
Water from Kongsfjorden, Svalbard sampled during late winter was
used to obtain the volatile properties and mixing state of primary marine aerosol by the V-TDMA method. In addition, the effect of water
temperature on the aerosol concentration was investigated. The VTDMA was originally built for airborne measurements, and was for
the first time used to investigate sea spray aerosol.
Foremost external mixtures of non-volatile aerosol, presumably
sea salt and volatile organic aerosol were observed for all particle sizes investigated, ranging between 0.025-0.158 m. As much as 73% by
number of the aerosol up to Dp=0.100 m evaporated after heating to
300 °C, which corresponds to the organic fraction of the aerosol. The
smallest organic aerosol number fraction was observed for the largest
particle size (Dp=0.158 m).
All aerosol sizes were sensitive to changes in water temperature
with an inverse relationship to increasing water temperature. Water
temperature did however not influence the aerosol mixing state or
organic fraction, and should foremost be regarded as an important
controlling factor of the number concentration of primary marine
aerosol production.
The organic fraction was possibly underestimated due to already
evaporated material nucleating in the cooling section of the thermodenuder, and the use of an active carbon trap in the cooling section of
the thermodenuder to adsorb evaporated material is suggested to improve the results.
30
6.4 Paper IV: Baltic Sea, eddy covariance method
Size resolved sea spray fluxes derived using the eddy covariance method from one of the coastal sites in the Baltic Sea used in Paper II
were here compared to simultaneous laboratory-made sea spray. The
eddy covariance technique demands instruments with high frequency
sampling, which can be difficult for sizes below about 0.1 m. As the
laboratory-made aerosol was detected down to 0.02 m, combining
the two methods could yield a wider sea spray flux spectrum. In order
to examine only the non-volatile part of the sea spray, it was heated to
300 °C. The results presented are to our knowledge the first near
coastal sea spray fluxes with limited fetch.
The non-volatile aerosol flux correlated better with wind speed
than did the volatile aerosol flux (r=0.74 vs. r=0.23, respectively).
Anthropogenic influences from central and eastern Europe, according
to back trajectory analysis, frequently contaminated the aerosol fluxes,
and the downward mixing of these aerosol particles is thought as a
contributing factor to the lower wind speed correlation of the unheated
sea spray.
There was a clear diurnal cycle in sea spray flux per whitecap,
where both tank and in-situ data agreed on a midday minimum. This
supports the possible existence of a biologically driven diurnal cycle
in sea spray production as suggested in Paper II.
Aerosol flux size distributions and organic number fractions from
the wind sector with the longest fetch corresponded well with previous
studies at open ocean conditions, while it appeared to be less organic
sea spray produced from more fetch-limited wind directions. This may
be an artifact due to larger deposition fluxes of anthropogenic particles
embedded in the upward net flux as a result of the closeness to the
coast.
For the data most resembling open ocean conditions, tank- and
ambient aerosol fluxes were combined and compared to the Mårtensson et al. (2003) model for sea salt, and to the Ellison et al. (1999)
model for organic surfactants. The combined tank- and ambient fluxes
most resembled a simple organic surfactant model or displayed larger
fluxes than that model, which could suggest that there were more organic material present in the original droplets than what one monolayer accounts for. Another explanation is that water or water soluble
organic material still remained within the droplets/particles.
31
7 Concluding remarks and outlook
This study has focused on primary marine aerosol particles, and
processes controlling their production. Four sites in three different
waters have been investigated, and all showed similar spectral features: aerosol number size distributions were stably centered close to
0.2 m Dp with little variation apart from magnitude (Papers I-III).
The average organic number fractions of the aerosol encountered by
heating the aerosol to 300 °C though displayed larger variations. The
organic fractions originating from northeastern Atlantic Ocean ranged
between 5 and 33% with a peak at 140 nm Dp (Paper I). The Arctic
water ditto was 25-65%, with a peak at 63 nm Dp (Paper III). Estimations from eddy covariance fluxes from the Baltic Sea put the average
organic mass flux fraction in the range of 35-80%, peaking at the lowest size measured, close to 300 nm Dp (Paper IV). Other key findings
are:
32

Laboratory made bubble-bursting in the small experimental
tanks used here produced a realistic bubble spectrum well in
agreement with previous studies from both wind tanks and real
oceanic measurements (Paper I).

An elevated salinity increased the aerosol production (Paper
II), while water temperature exhibited an inverse relationship
with aerosol production (Papers II and III).

No scientifically significant correlation between aerosol production and chlorophyll  was found (Paper I).

The primary marine aerosol concentrations were observed to
decrease at times of increased phytoplankton activity; from
one week to another at Askö, and on a diurnal basis at Garpen
(Paper II).

There was a high tendency for colony-forming bacteria to be
efficiently transported to the atmosphere by bubble-bursting
(Paper II).

A clear diurnal variation in aerosol production with a daytime
minimum was observed at the Baltic Sea, both for laboratory
made aerosol (Paper II), and for ambient sea spray flux normalized to the whitecap area (Paper IV). The observed minimum coincided with the peak in dissolved oxygen in the water,
suggesting a biologically driven diurnal cycle.

Foremost external mixtures of sea salt and marine organics
have been observed (Papers I and III).

The combination of laboratory made sea spray with ambient
flux data into a continuous size spectrum from Dp=0.02-2 m
unfortunately did not yield a conclusive result (Paper IV).
No single parameter was identified as being the controlling factor of
primary marine aerosol production during laboratory conditions. Salinity, water temperature, dissolved oxygen as well as biological activity co-vary and their individual influences were difficult to separate
under the natural conditions chosen here. In order to distinguish the
dominant parameter, or rather find the cut-off point where one parameter takes the lead over another, more extensive data sets in space
and time are necessary. Thus, a full year is suggested to obtain a complete seasonal cycle.
Many results in this study points out phytoplankton activity as a
key player affecting the aerosol production negatively. Our results
showed no correlation between aerosol production and chlorophyll
which commonly is used as a proxy for biomass. The data presented here are though ten-minute averages, and perhaps a correlation
could have been found studying a longer time frame. The composition
of phytoplankton-derived organic matter and the time lag between
increased phytoplankton activity as measured by chlorophyll  and
the production of these exudates is highly relevant, and could possibly
be found using continuous measurements of larger periods of time.
The question arises, is the time lag between phytoplankton activity
and an altered aerosol production of hours or days?
33
Additional measurements of the surface water chemical composition should be prioritized as the transfer of organic material to the
aerosol phase most likely is controlled by the solubility and surface
tension properties of marine organic matter (Facchini et al., 2008).
This need is also emphasized by the wide range of results obtained
from laboratory-made investigations regarding the submicrometer
organic mass fraction (Papers I, III and IV).
The foremost external mixtures of sea salt and organics observed
here contradict many observations of ambient marine aerosol. As primary marine aerosol can interact with anthropogenic aerosol emissions and aerosol precursor gases at ambient conditions, our result
does not rule out the possibility of an external mixture at formation.
The mixing states of primary marine aerosol originating from water of
high and low phytoplankton activity could teach us more about the
role saturation of surfactants has. Do external mixtures of sea salt and
organic compounds mainly occur at times when bursting bubbles are
not completely covered by organics?
An important goal for this study was to connect the knowledge
gained from laboratory investigations to real sea spray production as a
first step to transfer our results from the small experimental scale to
the real world. Even though the method used here is acknowledged to
produce realistic bubble spectra, possibly the bubble production in the
experimental tank, our “wave”, occasionally is too small. To test if a
larger experimental tank with a higher water flow resulting in a deeper
water plume and longer bubble life as suggested by Fuentes et al.
(2010) connects better to the ambient fluxes, would answer that question.
The bubbles yielding the submicrometer marine aerosol particles
are traditionally considered to be large, over about 2 mm diameter
(e.g., Blanchard and Syzdek, 1982; Resch and Afeti, 1992). Although
the bubble size distribution was investigated in Paper I, the upper
instrumental limit was only 1 mm and there was no strong correlation
between submicrometer aerosol and bubbles of that size or smaller.
With the recently updated information about smaller daughter bubbles
resulting in numerous jet droplets also from large bubbles (Bird et al.,
2010), even bubbles smaller than our lower instrumental limit of 30
m should also be investigated further. In addition, the bubble spectra
and the bubble‟s lifetime on the sea surface respond to changes in parameters such as salinity, water temperature as well as the concentration and composition of organics (e.g., Weber et al., 1983; Slauenwhite and Johnson, 1999; Leifer et al., 2000; Tyree et al., 2007). To
34
fully understand the impact of different environmental parameters on
the marine aerosol load and composition, and in turn their effect on
climate, one needs to focus on the bubbles producing the aerosol.
Thus, only with thorough investigations of bubbles and their response
to environmental changes, can the knowledge on submicrometer primary marine aerosol improve.
35
8 Acknowledgements
During the work of this thesis, I have spent several weeks either on a
research ship or on small islands, in one case without stable electricity. I have spent endless hours in front of my computer trying to make
sense of the data I have collected. In the world of research it is easy to
despair, and quite impossible to reach the end of an education like this
without support. Many people have crossed my path and affected this
work in numerous ways, to which I owe my thanks. I would like to
extend special thanks to:
My supervisor Douglas Nilsson who made particles as small as
0.02 m so interesting, so vivid, so important and so clear that I felt I
almost could touch them individually. Thanks for letting me try my
own way –and for pushing me back to focus when needed. A large
thank you also goes to my co-supervisor Radek Krejci. Not only have
you taught me how to fix a broken CPC (did I tell you I dropped the
lens once? I probably didn‟t…), you have always found time to read,
and improve, my manuscripts no matter the hour of day. Ian Cousins
is thanked for his support, and Åke Hagström for very nice lab equipment solutions, great food and good laughs.
Johan Ström for teaching me about aerosol measurement techniques when I first arrived at ITM, only two weeks before my first
field campaign when these newly learned skills quickly was put to
their test.
I would like to thank my co-authors for your time, ideas and for
giving me necessary and constructive criticism. Especially I wish to
thank Monica Mårtensson for always having time for my questions no
matter how small, Jarone Pinhassi for giving me a crash-course over
the phone on how to write a scientific paper (and for sharing an anecdote starring a lifeboat, which I won‟t forget easily), and Gerrit de
Leeuw for his encouragement and support during the MAP-06 cruise.
All technicians who helped me in numerous ways during data
sampling: Kai Rosman, Juri Wahler and Leif Bäcklin.
I would like to thank HC Hansson for having a door open for me,
and Anki Andersson for solving endless administrate inquires and
36
making “fika” the best part of the day. I‟m also most obliged to Hamish Struthers for making sure my English was understandable.
All past and present PhD students. I sincerely thank you for
lunches, coffees, therapy, good laughs, chats and the occasional kick
in the butt when needed. Especially I wish to thank Anna (there is
never a wrong time for a „latte‟ or a vampire discussion), Patricia (…
or for banana bread), Gustavo (…or to relax and listen to some good
music), Emma (…or for laugh or for a discussion on feminism), Sanna
(…or to focus on the fun parts of life), and Camilla (the best officemate in the world!). I am of course grateful to all you others at ml. But
please, fix the heating and make the automatically controlled ceiling
lamps be turned on during daytime instead of during nighttime.
Thanks also to my friends and believers outside work, whom I
have forsaken lately when my head has been filled with thesis. Especially I wish to thank Sonja Löfmark for your support, relaxed attitude
and good taste in coffee. I will miss our morning walks!
Finally, I wish to thank my loving and supporting family; my
sharp and creative mother Lotta, my insightful and humorous father
Ingemar, my unusually sane and unusually smart wife Hanna and my
prankish and very sweet son Micha. This thesis would not have seen
the light of day without your support.
Thank you.
37
9 References
Ackerman, A.S., Toon, O.B., Stevens, D.E., Heymsfield, A.J., Ramanathan, V., and E.J. Welton (2000), Reduction of tropical cloudiness by soot, Science, 288, 1042-1046.
Afeti, G.M., and F.J. Resch (1990), Distribution of the liquid aerosol
produced from bursting bubbles in sea and distilled water., Tellus,
42B, 378-384.
Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., and P.
Walter (Ed.) (2002), Molecular Biology of the cell, 4th ed.,
Garland Science, New York.
Albrecht, B.A. (1989), Aerosol, cloud microphysics, and fractional
cloudiness, Science, 245, 1227-1230.
Aller, J.Y., Kuznetsova, M.R., Jahns, C. J., and P.F. Kemp (2005),
The sea surface microlayer as a source of viral and bacterial
enrichment in marine aerosols, J. Aerosol Sci., 36, 801-812.
Andreas, E.L. (1998), A New Sea Spray Generation Function for
Wind Speeds up to 32 ms-1, J. Phys. Oceanogr., 28, 2175-2184.
Azam, F. (1998), Microbal control of oceanic carbon flux: the plot
thickens, Science, 280(5364), 694-696.
Azam, F., Fenchel, T., Field, J.G., Gray, J.S., Meyer-Reil, L.A., and F.
Thingstad (1983), The ecological role of water-column microbes
in the sea, Marine Ecology - Progress series, 10, 257-263.
Biddanda, B., and R. Benner (1997), Carbon, nitrogen, and
carbohydrate fluxes during the production of particulate and
dissolved organic matter by marine phytoplankton, Limnol.
Oceanogr., 42(3), 506-518.
Bird, J.C., de Ruiter, R., Courbin, L., and H.A. Stone (2010),
Daughter bubble cascades produced by folding of ruptured thin
films, Nature (465), 759-762.
Blanchard, D.C. (1963), The electrification of the atmosphere by
particles from bubbles in the sea, Prog. Oceanog., 1, 73-202.
Blanchard, D.C. (1983), The production, distribution, and bacterial
enrichment of the sea-salt aerosol in Air-Sea Exchange of gases
and particles 407-454 pp.
38
Blanchard, D.C., and L.D. Syzdek (1988), Film Drop Production as a
Function of Bubble Size, J. Geophys. Res., 93(C4), 3649-3654.
Blanchard, D.C., and L.D. Syzdek (1970), Mechanism for the Waterto-Air Transfer and Concentration of Bacteria, Science, 170, 626628.
Blanchard, D C., and L.D. Syzdek (1982), Water-to-Air Transfer and
Enrichment of Bacteria in Drops from Bursting Bubbles, Appl.
Environ. Microb., 43(5), 1001-1005.
Bowyer, P.A., Woolf, D.K., and E.C. Monahan (1990), Temperature
Dependence of the Charge and Aerosol Production Associated
With a Breaking Wave in a Whitecap Simulation Tank, J.
Geophys. Res., 95(C4), 5313-5319.
Brasseur, G.P., Prinn, R.G., and A. A.P. Pszenny (Ed.) (2003),
Atmospheric chemistry in a changing world, 1st ed., SpringerVerlag.
Cavalli, F., Facchini, M.C., Decesari, S., Mircea, M., Emblico, L.,
Fuzzi, S., Ceburnis, D., Yoon, Y.J., O'Dowd, C.D., Putaud, J.-P.,
and A. Dell'Acqua (2004), Advances in characterization of sizeresolved organic matter in marine aerosol over the North Atlantic,
J. Geophys. Res., 109(D24215).
Ceburnius, D., O'Dowd, C.D., Jennings, G.S., Facchini, M.C.,
Emblico, L., Decesari, S., Fuzzi, S., and J. Sakalys (2008),
Marine aerosol chemistry gradients: Elucidating primary and
secondary processes and fluxes, Geophys. Res. Lett., 35(L07084).
Christner, B.C., Cai, R., Morris, C.E., McCarter, K.S., Foreman, C.M.,
Skidmore, M.L., Montross, S.N., and D.C Sands (2008),
Geographic, seasonal, and precipitation chemistry influence on
the abundance and activity of biological ice nucleators in rain and
snow, P. Natl. Acad. Sci. USA, 105(48), 18854-18859.
Cipriano, R.J., and D.C. Blanchard (1981), Bubble and Aerosol
Spectra Produced by a Laboratory 'Breaking Wave', J. Geophys.
Res., 86(C9), 8085-8092.
Clarke, A., Kapustin, V., Howell, S., and K. Moore (2003), Sea-Salt
Size Distributions from Breaking Waves: Implications for Marine
Aerosol Production and Optical Extinction Measurements during
SEAS*, J. Atmos. Ocean. Tech., 20, 1362-1374.
Decesari, S., Facchini, M.C., Fuzzi, S., McFiggans, G., Coe, H., and
K.N. Bower (2005), The water-solule organic component of sizesegregated aerosol, cloud water and wet depositions from Jeju
Island during ACE-Asia, Atmos. Environ., 39, 211-222.
39
Ellison, G. B., A.F. Tuck, and V. Vaida (1999), Atmospheric
processing of organic aerosols, J. Geophys. Res, 104(D9), 1163311641.
Facchini, M.C., Decesari, S., Mircea, M., Fuzzi, S., and G. Loglio
(2000), Surface tension of atmospheric wet aerosol and cloud/fog
droplets in relation to their organic carbon content and chemical
composition, Atmos. Environ., 34, 4853-4857.
Facchini, M.C., Rinaldi, M., Decesari, S., Carbone, C., Finessi, E.,
Mircea, M., Fuzzi, S., Ceburnis, D., Flanagan, R., Nilsson, E.D.,
de Leeuw, G., Martino, M., Woeltjen, J., and C.D O'Dowd
(2008), Primary submicron marine aerosol dominated by
insoluble organic colloids and aggregates, Geophys. Res. Lett.,
35(L17814).
Freud, E., Rosenfeld, D., Andreae, M.O., Costa, A.A., and P. Artaxo
(2008), Robust relations etween CCN and the vertical evolution
of cloud drops size distriution in deep concetive clouds, Atmos.
Chem. Phys., 8, 1661-1675.
Fuentes, E., Coe, H., Green, D., de Leeuw, G., and G. McFiggans
(2010), Laboratory-generated primary marine aerosol via bubblebursting and atomization, Atmos. Meas. Tech., 3, 141-162.
Geever, M., O'Dowd, C.D., van Ekeren, S., Flanagan, R., Nilsson,
E.D., de Leeuw, G., and Ü. Rannik (2005), Submicron sea spray
fluxes, Geophys. Res. Lett., 32(L15810).
Gill, P.S., Graedel, T.E., and C.J. Weschler (1983), Organic films on
atmospheric aerosol particles, fog droplets, cloud droplets,
raindrops, and snowflakes, Rev. Geophys. Space Phys., 21(4),
903-920.
Gong, S.L., Barrie, LA., Prospero, J. M., Savoie, D.L., Ayers, G.P,
Blanchet, J.-P., and L. Spacek (1997), Modeling sea-salt aerosols
in the atmosphere 2. Atmospheric concentrations and fluxes, J.
Geophys. Res., 102(D3), 3819-3830.
Grini, A., Myhre, G., Sundet, J.K., and I.S.A. Isaksen (2002),
Modeling the Annual Cycle of Sea Salt in the Global 3D Model
Oslo CTM2: Concentrations, Fluxes, and Radiative Impact, Am.
Met. Soc., 1717-1730.
Haywood, J.M., Ramaswamy, V., and B.J. Soden (1999),
Tropospheric aerosol climate forcing in clear-sky satellite
observations over the oceans, Science, 283, 1299-1303.
Hejkal, T.W., LaRock, P.A., and J.W. Winchester (1980), Water-toAir Fractionation of Bacteria, Appl. Environ.Microb., 39(2), 335338.
40
IPCC (2007), Climate Change 2007 : The Physical Science Basis.
Contribution of Working Group I to the Fourth Assesment Report
of the Intergovernmental Panel on Climate Change., Cambridge
University Press, Cambridge, United Kingdom and New York,
NY, USA.
Johnson, B.T., Shine, K.P., and P.M. Forster (2004), The semi-direct
aerosol effect: Impact of absorbing aerosols on marine
stratocumulus, Q. J. Roy. Meteor. Soc., 130(599), 1407-1422.
Karp, G. (Ed.) (1999), Cell and molecular biology, 2nd ed., John
Wiley & Sons.
Keene, W.C., Maring, H., Maben, J.R., Kieber, D.J., Pszenny, A.A. P.,
Dahl, E.E., Izaguirre, M.A., Davis, A.J., Long, M.S., Zhou, X.,
Smoydzin, L., and R. Sander (2007), Chemical and physical
characteristics of nascent aerosols produced by bursting bubbles
at a model air-sea interface, J. Geophys. Res., 112(D21202).
Kogure, K., Simidu, U., and N. Taga (1978), A tentative direct
microscopic method for counting living marine bacteria, Can. J.
Microb., 25(3), 415-420.
Kulmala, M., Vehkamäki, H., Petäjä, T., Dal Maso, M., Lauri, A.,
Kerminen, V.-M., Birmili, W., and P.H. McMurry (2004),
Formation and growth rates of ultrafine atmospheric particles: a
review of observations, J. Aerosol Sci., 143-176.
Leifer, I., Ranjan P.K., and P. Bowyer (2000), A Study on the
Temperature variation of Rise Velocity for Large Clean Bubbles,
J. Atmos. Ocean. Tech., 17, 1392-1402.
Leifer, I., de Leeuw, G., and L. H. Cohen (2003), Optical
measurement of bubbles: system design and application, Am. Met.
Soc.y, 20, 1317-1332.
Lewis, E.R., and S.E. Schwartz (2004), Sea Salt Aerosol Production:
Mechanisms, Methods, Measurements and Models, AGU,
Washington D.C.
Linley, E.A.S., Newell, R.C., and M.I. Lucas (1983), Qualitatilve
relationships between phytoplankton, bacteria and heterotrophic
microflagellates in shelf waters, Mar. Ecol. - Prog. Ser., 12, 7789.
Lohmann, U., and J. Freichter (2005), Gloal indirect aerosol effects: a
review, Atmos. Chem. Phys., 5, 715-737.
Maki, L.R., Galyan, E.L., Chang-Chien, M.-M., and D.R. Cladwell
(1974), Ice nucleation induced by Pseudomonas syringae, Appl.
Microb., 456-459.
41
Marks, R., Kruczalak, K., Jankowska, K., and M. Michalska (2001),
Bacteria and fungi in air over the Gulf of Gdánsk and Baltic sea,
J. Aerosol Sci. 32, 237-250.
McFiggans, G., Artaxo, P., Baltensperger, U., Coe, H., Facchini, M.
C., Feingold, G., Fuzzi, S., Gysel, M., Laaksonen, A., Lohmann,
U., Mentel, T.F., Murphy, D.M., O'Dowd, C.D., Snider, J.R., and
E. Weingartner (2006), The effect of physical and chemical
aerosol properties on warm cloud droplet activation, Atmos.
Chem. Phys., 6, 2593-2649.
Millero, F.J. (Ed.) (2005), Chemical oceanography, 3rd ed., Taylor &
Francis Group/ CRC Press.
Modini, R.L., Harris, B., and Z.D. Ristovski (2010), The organic
fraction of bubble-generated, accumulation mode Sea Spray
Aerosol (SSA), Atmos. Chem. Phys., 10, 2867-2877.
Monahan, E.C., and I.Ó Muircheartaigh (1986), Whitecaps and the
passive remote-sensing of the ocean surface, Int. J. Remote Sens.,
7(5): 627-642.
Monahan, E.C., Davidson, K. L., and D.E. Spiel (1982), Whitecap
Aerosol Productivity Deduced From Simulation Tank
Measurements, J. Geophys. Res, 87(C11), 8898-8904.
Monahan, E.C., Fairall, C.W., Davidson, K.L., and P. Jones Boyle
(1983), Observed inter-relations between 10m winds, ocean
whitecaps and marine aerosols, Q. J. Roy. Meteor. Soc., 109(460),
379-392.
Murphy, D.M., Anderson, J.R, Quinn, P. K, McInnes, L.M., Brechtel,
F.J, Kreidenweis, S.M., Middlebrook, A.M., Pósfai, M.,
Thomson, D.S, and P.R. Buseck (1998), Influence of sea-salt on
aerosol radiative properties in the Southern Ocean marine
boundary layer, Nature, 392, 62-65.
Mårtensson, E.M., Nilsson, E.D., de Leeuw, G., Cohen, L.H., and H.C. Hansson (2003), Laboratory simulations and parameterization
of the primary marine aerosol production, J. Geophys. Res,
108(D9)(4297).
Nilsson, E.D., Mårtensson, E.M., Van Eleren, J.S., de Leeuw, G.,
Moerman, M., and C. O'Dowd (2007), Primary marine aerosol
emissions: size resolved eddy covariance measurements with
estimates of sea salt and organic carbon fractions, Atmos. Chem.
Phys.- Discussions, 7, 13345-13400.
Nilsson, E. D., Rannik, Ü, Swietlicki, E., Leck, C., Aalto, P. P., Zhou,
J., and M. Norman (2001), Turbulent aerosol fluxes over the
42
Arctic Ocean 2. Wind-driven sources from the sea, J. Geophys.
Res, 106(D23),32,139-132,154.
Norris, S. J., Brooks, I. M., de Leeuw, G., Smith, M.H., Moerman, M.,
and J.J.N. Lingard (2008), Eddy covariance measurements of sea
spray particles over the Atlantic Ocean, Atmos. Chem. Phys., 8,
555-563.
O'Dowd, C.D., and G. de Leeuw (2007), Marine aerosol production: a
review of the current knowledge, Philos. T. Roy. Soc., 365, 17531774
O'Dowd, C.D., and M.H. Smith (1993), Physiochemical Properties of
Aerosols Over the Northeast Atlantic: Evidence for Wind-SpeedRelated Submicron Sea-Salt Aerosol Production, J. Geophys.
Res., 98(D1), 1137-1149.
O'Dowd, C.D., Facchini, M.C., Cavalli, F., Ceburnis, D., Mircea, M.,
Decesari, S., Fuzzi, S., Yoon, Y.J., and J.-P. Putaud (2004),
Biogenically driven organic contribution to marine aerosol,
Nature, 431, 676-680.
O'Dowd, C.D., Lowe, J.A., and M.H. Smith (1999), Observations and
modelling of aerosol growth in marine stratocumulus - case study,
Atmos. Environ., 33, 3053-3062.
O'Dowd, C.D., Lowe, J.A., Clegg, N., Smith, M.H., and S.L. Clegg
(2000), Modeling heterogeneous sulphate production in maritime
stratiform clouds, J. Geophys. Res 105(D6), 7143-7160.
O'Dowd, C.D., Smith, M.H., Consterdine I.E., and J.A. Lowe (1997),
Marine aerosol, sea-salt, and the marine sulphur cycle: A short
review, Atmos. Environ., 31(1), 73-80.
Pratt, K.A., DeMott, P.J., French, J.R., Wang, Z., Westphal, D.L.,
Heymsfield, A.J., Twohy, C.H., Prenni, A.J., and K.A. Prather
(2009), In situ detection of biological particles in cloud icecrystals, Nature Geosci., 2, 398-401.
Raes, F., Van Dingenen, R., Vignati, E., Wilson, J., Putaud, J.-P.,
Seinfeld, J.H., and P. Adams (2000), Formation and cycling of
aerools in the gloal troposphere, Atmos. Environ., 34, 4215-4240.
Reinke, N., Vossnacke, A., Schütz,W., Koch, M. K., and H. Unger
(2001), Aerosol generation by bubble collapse at ocean surfaces,
Water Air Soil Poll.: Focus, 1, 333-340.
Resch, F., and G. Afeti (1992), Submicron film drop production by
bubbles in seawater, J. Geophys. Res, 97(C3), 3679-3683.
Rosenfeld, D. (2006), Aerosol-cloud interactons control of Earth
radiation and latent heat release budgets, Space Sci. Rev..
43
Russell, L.M., and E.G. Singh (2006), Submicron Salt Particle
production in Bubble bursting, Aerosol Sci.Tech., 40, 664-671.
Schnell, R.C. (1977), Ice nuclei in seawater, fog water and marine air
off the coast of Nova Scotia: summer 1975, J. Atmos. Sci., 34,
1299-1305.
Scott, J.C. (1975), The role of salt in whitecap persistence, Deep-Sea
Res. I, 22, 653-657.
Seinfeld, J.H., and S.N. Pandis (2006), Atmospheric chemistry and
physics: from air pollution to climate change, 2nd ed., John
Wiley & Sons Inc., Hoboken, New Jersey, USA.
Sellegri, K., O'Dowd, C.D., Yoon, Y.J., Jennings, S.G., and G. de
Leeuw (2006), Surfactants and submicron sea spray generation, J.
Geophys. Res, 111(D22215).
Slauenwhite, D.E., and B.D. Johnson (1999), Bubble shattering:
differences in bubble formation in fresh water and seawater, J.
Geophys. Res, 104(C2), 3265-3275.
Smith, M.H., Park, P.M., and I.E. Consterdine (1993), Marine aerosol
concentrations and estimated fluxes over the sea, Q. J. Roy.
Meteor. Soc., 119, 809-824.
Spiel, D.E. (1998), On the births of film drops from bubbles bursting
on seawater surfaces, J. Geophys. Res, 103(C11), 24,907924,918.
Taketani, F., Kanaya, Y., and H. Akimoto (2008), Heterogeneous loss
of HO2 by KCl, synthetic sea salt, and natural seawater aerosol
particles, Atmos. Environ., 43, 1660-1665.
Twomey, S. (1977), The influence of pollution on the shortwave aledo
of clouds, J. Atmos. Sci., 34, 1149-1152.
Tyree, C.A., Hellion, V. M., Alexandrova, O.A., and J.O. Allen
(2007), Foam droplets generated from natural and artificial
seawaters, J. Geophys. Res, 112(D12204).
Wania, F., Axelman, J., and D. Broman (1998), A review of processes
involved in the exchange of persistent organic pollutants across
the air-sea interface, Environ. Poll., 102, 3-23.
Wotton, R.S., and T.M. Preston (2005), Surface Films: Areas of Water
Bodies That Are Often Overlooked, BioScience, 55(2), 137-145.
44