Size-segregated particulate air samples were collected during the
austral summer of 2016–2017 at Palmer Station on Anvers Island, western Antarctic Peninsula,
to characterize trace elements in aerosols. Trace
elements in aerosol samples – including Al, P, Ca, Ti, V, Mn, Ni, Cu, Zn, Ce,
and Pb – were determined by total digestion and a sector field inductively
coupled plasma mass spectrometer (SF-ICP-MS). The crustal enrichment factors
(EFcrust) and k-means clustering results of particle-size distributions
show that these elements are derived primarily from three sources: (1) regional crustal emissions, including possible resuspension of soils
containing biogenic P, (2) long-range transport, and (3) sea salt. Elements
derived from crustal sources (Al, P, Ti, V, Mn, Ce) with
EFcrust<10 were dominated by the coarse-mode particles
(>1.8µm) and peaked around 4.4 µm in diameter,
reflecting the regional contributions. Non-crustal elements (Ca, Ni, Cu, Zn,
Pb) showed EFcrust>10. Aerosol Pb was primarily dominated
by fine-mode particles, peaking at 0.14–0.25 µm, and likely was
impacted by air masses from southern South America based on air mass back
trajectories. However, Ni, Cu, and Zn were not detectable in most size
fractions and did not present clear size patterns. Sea-salt elements (Ca,
Na+, K+) showed a single-mode distribution and peaked at 2.5–4.4 µm. The estimated dry deposition fluxes of mineral dust for the
austral summer, based on the particle-size distributions of Al measured at
Palmer Station, ranged from 0.65 to 28 mg m-2 yr-1 with a mean of
5.5±5.0 mg m-2 yr-1. The estimated dry deposition fluxes
of the target trace elements in this study were lower than most fluxes
reported previously for coastal Antarctica and suggest that atmospheric
input of trace elements through dry deposition processes may play a minor
role in determining trace element concentrations in surface seawater over
the continental shelf of the western Antarctic Peninsula.
Introduction
Aerosols affect the climate through direct and indirect radiative forcing
(Kaufman et al., 2002). The extent of such forcing depends on both
physical and chemical properties of aerosols, including particle size and
chemical composition (Pilinis et al., 1995). Size and chemical
composition of aerosols influence aerosol optical properties as well as
cloud formation and development (Weinzierl et al., 2017), and such
information is critically needed in a climate model for better estimating
aerosol climate effects (Adebiyi and Kok, 2020). In the atmosphere, the
removal of aerosols involves gravitational settling, impaction, diffusion,
hygroscopic growth, and scavenging by precipitation, and the rates of all
these processes are dependent on the aerosol particle size (Saltzman,
2009). Over the Southern Ocean and Antarctica, aerosol particle-size
distributions have been studied (Gras, 1995; Järvinen et al., 2013;
Xu et al., 2013; Kim et al., 2017; Herenz et al., 2019; Lachlan-Cope et al.,
2020). Seasonal variations of the particle number concentrations were
observed at King Sejong Station, Antarctic Peninsula, and Halley
Research Station on the Brunt Ice Shelf. The maximum and minimum of the
particle number concentrations at two sites were found in the austral summer
and austral winter, respectively (Kim et al., 2017; Lachlan-Cope et al.,
2020). Due to the low background concentrations of aerosol particles, new
particle formation has been suggested to substantially affect the annual
aerosol concentration cycles (Lachlan-Cope et al., 2020). However, most
of these studies focused on the physical characteristics of aerosol particle
size; the size distributions of aerosol trace elements are still poorly
understood, and at present only aerosol Fe has been characterized for
particle-size distributions around Antarctica (Gao et al., 2013, 2020).
Atmospheric aerosol deposition delivers nutrient elements to the open ocean,
playing an essential role in maintaining marine primary production
(Jickells and Moore, 2015; Jickells et al., 2016; Mahowald et al., 2018).
A significant source of atmospheric trace elements in the remote oceans is
continental dust derived from arid and unvegetated regions (Duce and
Tindale, 1991). In addition, sea-salt emission, volcanic eruptions, biomass
burning, anthropogenic activities, and even glacial processes contribute
trace elements to the atmosphere (Pacyna and Pacyna, 2001; Chuang et al.,
2005; Guieu et al., 2005; Crusius et al., 2011; Baker et al., 2020). The
surface concentrations of the trace elements Al, Fe, Mn, Zn, and Pb in
several open-ocean regions depend strongly on atmospheric inputs (Duce et
al., 1991; Prospero et al., 1996; Wu and Boyle, 1997; Measures and Vink,
2000; Moore et al., 2013; Bridgestock et al., 2016).
Atmospheric trace elements over the Southern Ocean and Antarctica may derive
from distant continental sources through long-range transport (Li et
al., 2008) and local dust sources in certain areas (Kavan et al.,
2018; Delmonte et al., 2020). A wide range of aerosol studies have been
carried out in Antarctica, with the intention of understanding the processes
affecting aerosols and the background level of trace elements in the
atmosphere (Zoller et al., 1974; Dick and Peel, 1985; Tuncel et al.,
1989; Artaxo et al., 1990; Lambert et al., 1990; Dick, 1991; Artaxo et al.,
1992; Loureiro et al., 1992; Mouri et al., 1997; Mishra et al., 2004;
Arimoto et al., 2008; Gao et al., 2013; Xu and Gao, 2014; Winton et al.,
2016). In the Antarctic Peninsula, the concentrations of aerosol trace
elements were measured at several sites (Dick, 1991; Artaxo et al., 1992;
Mishra et al., 2004; Préndez et al., 2009). Total dust deposition in
this region was also estimated based on the ice-core record (McConnell
et al., 2007). However, the measurement of particle-size distribution of
aerosol trace elements in the Antarctic Peninsula is missing and there is no
direct measurement that evaluated the importance of atmospheric deposition
as a source of nutrients for primary producers in western Antarctic Peninsula
shelf waters. Over the past several decades, one of the most dramatically
warming regions in the Southern Hemisphere has been the Antarctic Peninsula
(Vaughan et al., 2003; Bromwich et al., 2013; Turner et al., 2014).
Warming ocean waters have caused most glaciers on the peninsula to retreat
(Cook et al., 2016), and small increases in air temperature are
contributing to rapid summer melting and ice loss in this region (Abram
et al., 2013).
Under conditions of low precipitation (Van Lipzig et al., 2004) and high
wind speed (Orr et al., 2008), several ice-free areas on James Ross
Island, off the east coast of the northern peninsula, could serve as local
dust sources (Kavan et al., 2018), and such sources may contribute to
the atmospheric loading of certain trace elements such as Fe (Winton et
al., 2014; Gao et al., 2020). Similar ice-free areas were found on King
George Island, Livingston Island, Anvers Island, etc. in the Antarctic
Peninsula region (Bockheim et al., 2013) and may act as potential
sources of eolian dust. As part of the current study, the particle-size
distribution of aerosol Fe measured at Palmer Station showed single-mode
distribution and was dominated by coarse particles, suggesting that local
regional dust emission dominated the concentration of Fe in this region
(Gao et al., 2020). Under the current warming trend, ice core data show
that lithogenic dust deposition more than doubled during the 20th century in
the Antarctic Peninsula (McConnell et al., 2007). In addition, the
rapid-warming condition may enhance the emission of other sources. For example,
the Antarctic Peninsula has been suggested as one of the sites that have the
highest P excretions contributed by seabird colonies globally (Otero
et al., 2018). The enhanced local dust emission may thus cause an increased
P emission as well. Consequently, dust emissions induced by regional warming
may have impacted the concentrations of aerosol trace elements in the marine
atmosphere over the Antarctic Peninsula, affecting atmospheric deposition of
trace elements to coastal waters off the Antarctic Peninsula and adjacent
pelagic waters of the Southern Ocean (Wagener et al., 2008). However,
aerosol trace elements are still undersampled around coastal Antarctica,
and thus quantification of the chemical and physical properties of aerosols
and accurate estimation of the atmospheric deposition of trace elements to
the region are inadequate.
This study presents multi-element results from an in situ measurement of
size-segregated aerosol particles at Palmer Station, Antarctic Peninsula, in
the austral summer of 2016–2017. The objectives are to (1) measure the
concentrations and size distributions of a suite of aerosol trace elements,
(2) determine potential sources of the elements, and (3) estimate dry
deposition fluxes of the elements based on the concentrations in 10 size
classes of aerosols. Results from this study fill a data gap critically
needed for characterization of aerosol properties and for improving
quantification of the fluxes that contribute to regional biogeochemical
cycles. The new observational data also provide insight into sources of
aerosol trace elements, as influenced recently by warming, which exposes a
greater area of ice-free land, and by the impact of human activities in this
region. A full discussion of atmospheric Fe in this sample set was published
recently (Gao et al., 2020); this paper extends that study by
investigating the concentrations, size distributions, and dry deposition
fluxes of a suite of additional aerosol trace elements.
Sampling site at Palmer Station (red dot) with inset photograph of
sampling platform (Gao et al., 2020) (satellite image credits:
NASA).
MethodsSampling and sample treatment
Size-segregated aerosol samples were collected during austral summer from
19 November 2016 to 30 January 2017 at Palmer Station (64.77∘ S,
64.05∘ W, Fig. 1), located on the southwestern coast of Anvers
Island off the Antarctica Peninsula. A detailed description of the aerosol
sampling, including the protocols for mitigating contamination in the
pristine environment, can be found in Gao et al. (2020). Briefly, sampling
was conducted using a 10-stage Micro-Orifice Uniform Deposit
Impactor™ (MOUDI, MSP Corp., MN, USA) with a 30 L min-1 flow
rate. The 50 % cut-off aerodynamic diameters of MOUDI are 0.056, 0.10,
0.18, 0.32, 0.56, 1.0, 1.8, 3.2, 5.6, 10, and 18 µm. In this study,
size fractions ≤1.0µm were summed to operationally define
fine-mode particles, and those ≥1.8µm were summed to define
coarse-mode particles, similar to previous studies which operationally
divided aerosol particles into fine and coarse fractions using a cut-off
size of 1.0–3.0 µm (Siefert et al., 1999; Chen and Siefert, 2004;
Buck et al., 2010; Gao et al., 2019). The aerosol sampler was placed on a
sampling platform which was ∼300 m east from the station
center and ∼3 m above the ground (∼20 m
above sea level) in “Palmer's backyard” (Gao et al., 2020). To
avoid local contamination from the research station, a wind control system
was set up to pause aerosol sampling when the wind direction was inside the
sector ±60∘ from the direction of the station buildings or
when wind speed was <2 m s-1. The active sampling time was about
71–98 % of the total sampling time (Table 1). Due to extremely low
concentrations of aerosol trace elements over Antarctica, the duration of
each sampling event was approximately 1 week (Table 1).
Sampling periods and meteorological conditions for individual samples (Gao et al., 2020).
SampleSampling period%ActualSamplingWindAirRelativeAirPrecip.SolarIDsampling time*volumespeedtemperaturehumiditypressureintensity(%)(m3)(m s-1)(∘C)(%)(hPa)(mm d-1)(W m-2)M119–26 Nov 2016782255.7 (0.7–22)0.1 (-2.2–4.3)87 (52–100)990 (976–1011)4.19166 (0–675)M226 Nov–4 Dec 2016712334.9 (0.4–21)0.7 (-2.2–5.8)82 (45–100)982 (959–997)1.37191 (0–847)M49–17 Dec 2016802663.5 (0.1–15)0.7 (-3.3–5.6)83 (53–100)985 (969–998)0.37207 (1–854)M517–24 Dec 2016882642.5 (0.3–9.8)2.0 (-0.7–5.5)77 (49–100)988 (972–996)0.05195 (1–723)M71–8 Jan 2017852444.1 (0.2–13)1.8 (-0.7–3.8)72 (49–99)987 (972–997)0.09272 (0–857)M88–15 Jan 2017942835.4 (0.7–16)2.6 (0.3–5.5)64 (46–95)982 (973–991)0225 (0–792)M915–23 Jan 2017872855.0 (0.2–15)2.1 (-1.0–5.3)65 (42–86)987 (981–997)0.15260 (0–829)M1023–30 Jan 2017982798.9 (0.7–21)4.1 (1.7–7.1)79 (65–90)981 (969–997)3.7110 (0–594)
* Actual sampling time / total sampling time ×100 %.
After each sampling, the MOUDI sampler was carried back to the lab in the
research station for sample filter changing and sampler cleaning in a Class
100 clean-room flow bench. Aerosol samples were stored frozen in pre-cleaned
Petri dishes at -20∘ before analyses. A total of eight sets of
size-segregated aerosol samples were collected on Teflon filters (1 µm pore size, 47 mm diameter, Pall Corp., NY, USA). A full set of blank
filters (n=11) was mounted on the sampler, carried to the sampling
platform without running the sampler, and thus defined as field blanks.
Meteorological conditions were recorded in situ by a weather station (Campbell
Scientific, UT, USA) installed on the same platform (Table 1).
Chemical analysesTrace elements in aerosols
Aerosol samples were analyzed for the concentrations of trace elements by an
Element-1 sector field inductively coupled plasma mass spectrometer
(SF-ICP-MS, Thermo-Finnigan, Bremen, Germany) at the Department of Marine
and Coastal Sciences of Rutgers University, following a strong acid
digestion method described in Gao et al. (2020). Elemental
concentrations were determined for Al, P, Ca, Ti, V, Mn, Ni, Cu, Zn, Ce, and
Pb. Briefly, a quarter of each sample filter was digested in a closed 15 mL
Teflon vial (Savillex, MN, USA) with Optima grade HF (0.1 mL) and HNO3
(0.8 mL) (Fisher Scientific, NJ, USA). Sample digestion was performed on a
uniform-heating HPX-200 (Savillex, MN, USA) hot plate for 4 h at 165∘ followed by complete evaporation of acids. Then, 2.0 mL of 3 %
HNO3 with 1 ppb indium (In) solution was added to re-dissolve the
sample, with the In used as an internal standard to correct instrument drift in
the ICP-MS analyses. All the digestion processes were carried out in a HEPA-filter-controlled Class 100 clean hood in the Atmospheric Chemistry Laboratory at Rutgers University. The Teflon vials and test tubes used in
this study were thoroughly acid-cleaned. To ensure the data quality, for
each batch of samples, at least two procedural blanks were processed in the
same way as the samples to monitor for possible contamination. During the
ICP-MS analysis, duplicate injections of sample solutions were made every
10 samples to check the instrument precision (Table S1 in Supplement). The recovery of
this analytical protocol was estimated by seven separate digestions of the
Standard Reference Material (SRM) 1648a urban particulate matter (National
Institute of Standard and Technology, MD, USA) (Table S1). The method limits
of detection (LOD) were calculated as 3 times the standard deviation of
11 field blanks and a 200 m3 representative sampling volume (Table S1).
The medians of the percentage of blanks in samples for detectable trace elements were
calculated for quality control (Table S1). The concentrations below LOD were
given a concentration of 0 for the purposes of this study. Elements with
all concentrations lower than the LOD – including Cr, Co, Cd and Sb – were
measured but are not reported or discussed. The aerosol Fe concentrations
were reported in Gao et al. (2020) and are not included in this paper.
Although the fractional solubility of Fe was obtained, the solubilities for
the other trace elements are not measured or discussed in this study.
Ionic tracers in aerosols
The concentrations of water-soluble Na+ and K+ in aerosols were
analyzed by ion chromatography (IC) (ICS-2000, Dionex, CA, USA) with an
IonPac CS12A (2×250 mm2) analytical column at the
Atmospheric Chemistry Laboratory at Rutgers University. The cations Na+
and K+ were used as tracers to estimate the portion of aerosols derived
from seawater and biomass burning, respectively. The non-sea-salt K+
(nss-K+) was estimated using the equation [nss-K+] = [K+] - 0.037[Na+]. Sample processing for IC analysis was similar to the
method used by Zhao and Gao (2008) and Xu et al. (2013). Briefly, a
quarter of the sample filter was transferred to a plastic test tube and
leached with 5.0 mL Milli-Q water in an ultrasonic bath for 20 min at
room temperature. Before being injected into the IC, the leachate was
filtered through a PTFE syringe filter (0.45 µm pore size, VWR, PA,
USA). The method LOD for Na+ and K+ based on seven blanks and a 200 m3 representative sampling volume was 2 and 1 ng m-3,
respectively. The precision of the analytical procedures based on seven
spiked samples was <±1 %.
Data analysesEnrichment factors
To achieve an initial estimate of the possible sources for trace elements,
enrichment factors relative to the upper continental crust (EFcrust) were
calculated, using the equation
EFcrust=(Xi/XAl)sample(Xi/XAl)crust,
where (Xi/XAl)sample is the mass concentration ratio of element i
to the crustal reference element, Al, in aerosol samples, and
(Xi/XAl)crust is the abundance ratio of element i to Al in the
upper continental crust (Taylor and McLennan, 1995). The crustal
reference element Al has been widely used to calculate crustal enrichment
factors in the Southern Ocean and Antarctica (Zoller et al., 1974; Dick,
1991; Lowenthal et al., 2000; Xu and Gao, 2014). When the EFcrust is
greater than 10, the element likely has additional contributions from other
sources (Weller et al., 2008).
Particle-size distribution and k-means clustering
The aerosol particle-size distributions were converted to normalized
concentrations, which are defined as the concentration of trace elements in a
size bin divided by the width of the bin (Warneck, 1988):
dCdlog(Dp)=dClog(Dp,u)-log(Dp,l).
In the equation, dC is the mass concentration of trace elements in a size
bin, and dlog(Dp) is the difference in the log of the bin width.
The dlog(Dp) is calculated by subtracting the log of the lower
bin boundary (log(Dp,u)) from the log of the upper bin boundary
(log(Dp,l)). The k-means clustering algorithm was used to cluster
the average particle-size distribution of each trace element. The optimal
number of clusters (k) was selected by choosing the k with the highest
Caliński–Harabasz index (Caliński and Harabasz, 1974).
Atmospheric dry deposition flux estimation
Dry deposition flux (Fd, mg m-2 yr-1) of each element in
aerosols was calculated from the concentration (Ce, ng m-3) of the
trace element in the air and dry deposition velocity (Vd, cm s-1):
Fd=0.315×Vd×Ce,
where 0.315 is a unit conversion factor (Gao et al., 2013). The
Vd for each trace element was computed by dry deposition rates
(Vdi, cm s-1) and particle distribution ratios (Pdri, %)
following the equation
∑i=110Vdi×Pdri.
The Pdri was derived from the concentrations of trace elements in
different size fractions i, and Vdi was estimated using a combination
model of Williams (1982) and Quinn and Ondov (1998). This model
includes the effects of wind speed, air–water temperature difference, sea
surface roughness, spray formation at high wind speed, and relative humidity.
Meteorological parameters used for estimating dry deposition rates were
measured in situ by the weather station with 1 min temporal resolution that was
converted to 1 h averages. Sea surface temperature data were obtained
from the Palmer Station Long-Term Ecological Research (LTER) study
(https://oceaninformatics.ucsd.edu/datazoo/catalogs/pallter/datasets/28, last access: 29 January 2021).
Dry deposition rates of coarse-mode particles were dominated by
gravitational settling, whereas the dry deposition rates of smaller
particles were controlled by environmental factors, including wind speed,
relative humidity, air temperature, and sea surface temperature (Fig. 2).
Therefore, the uncertainties of the dry deposition velocity estimation for
the elements that were dominated by coarse particles were about ±30–60 %, and the uncertainty of the fine-particle-dominated element (Pb) was
about ±100 %. The overall estimation of dry deposition flux usually
carries substantial uncertainty (a factor of 2 to 4) due to the limited
sampling volume and the assumptions inherent to the Vdi estimation
(Duce et al., 1991; Gao et al., 2020). The dry deposition velocities
determined for each element are reported in Table 3. Dry deposition fluxes
were calculated for the trace elements showing clear particle-size
distribution patterns: Al, P, Ca, Ti, V, Mn, Ce, and Pb. For Ni, Cu, and Zn,
which did not show clear size distributions, the ranges of their dry
deposition fluxes were also estimated by applying their mean concentrations
to the lowest (Pb, 0.11±0.12 cm s-1) and highest (Al, 0.49±0.28 cm s-1) dry deposition velocities. The dry deposition
fluxes of dust were estimated based on the concentrations and particle-size
distributions of Al in aerosols, assuming that Al accounted for 8 % of
dust mass (Taylor and McLennan, 1995).
Median dry deposition rates of each size class of aerosol
particles for samples M1–M10, collected between November 2016 and January 2017. The
dry deposition rate is not only a function of aerosol particle size (Dp) but also
depends on meteorological conditions (see text).
Air mass back trajectories
To explore possible source regions of air masses affecting trace elements in
aerosols collected at Palmer Station, the NOAA Hybrid Single-Particle
Lagrangian Integrated Trajectory Model (HYSPLIT) was used to calculate
72 h air mass back trajectories for each sampling duration (Rolph et
al., 2017). In this study, the HYSPLIT model was driven by the
meteorological data from the Global Data Assimilation System (GDAS) with a
0.5∘ resolution. Each air mass back trajectory was calculated at
3 h intervals and started from one-half mixed boundary layer height. The
back trajectories during each sampling period were used to calculate
trajectory frequencies, which were defined by the following equation:
trajectory frequencies=100×number of
endpoints per grid squarenumber of trajectories.
Results and discussionEnrichment factors of trace elements
Crustal enrichment factors of trace elements in aerosols were calculated as
the first step of source identification (Fig. 3). Two major EF groups were
found, representing crustal and non-crustal elements as follows.
Box plots of EFcrust for trace elements in aerosols collected
at Palmer Station between November 2016 and January 2017. The central horizontal line
is the mean value, and the bottom and the top of each box are the 25th and
75th percentiles. The upper and lower horizontal bars indicate the 5th and
95th percentiles of the data.
Crustal elements (P, Ti, V, Mn, Ce)
The values of EFcrust for Ti, V, Mn, and Ce in aerosol samples were
less than 10, indicating that a crustal source is the dominant source for
those elements (Fig. 3). As typical lithogenic elements (Boës et
al., 2011), Ti and Mn in aerosols over oceanic regions are usually derived
from natural dust emissions (Shelley et al., 2015; Marsay et al., 2018;
Buck et al., 2019). Likewise, V and Ce in aerosols over the South Pole were
reportedly dominated by crustal weathering (Zoller et al., 1974). In
addition to crustal emissions, long-range transport may deliver some portion
of these trace elements from remote sources to Antarctica (Wagener et
al., 2008). For example, aerosol Ce and Mn derived from anthropogenic
emissions were thought to be contributed by additives in vehicle fuels
(Fomba et al., 2013; Gantt et al., 2014), and V in aerosols was found
associated with ship emissions due to the use of heavy-oil fuel (Keywood
et al., 2020). However, the EFcrust results from this study suggest
that nearby fuel combustion did not cause significant enrichment of V in
aerosols at Palmer Station. Similarly, unenriched V was observed at McMurdo
Station, where lightweight-fuel oil was used that was not a significant
source of V (Lowenthal et al., 2000). We conclude that Ti, Mn, V, and Ce
observed at Palmer Station were derived primarily from crustal sources.
The range of EFcrust for P was between 2 and 8, relatively higher than
that of the other crustal elements. In Antarctic soils, P has been widely
studied (Campbell and Claridge, 1987; Blecker et al., 2006; Prietzel et
al., 2019). Around the Antarctic coast, including the northern end of the
Antarctic Peninsula, high P inputs to the surface soil were found in seabird
colonies (Otero et al., 2018), and a high enrichment of P (EFcrust=33) was reported previously at King George Island (Artaxo et al.,
1990). The closest potential source, the penguin colony on Torgersen Island,
is only about 1 km from Palmer Station. Given that regional wind-induced
dust likely affects aerosol composition over the Antarctic Peninsula
(Asmi et al., 2018; Gao et al., 2020), soil-derived P is likely to be
emitted to the atmosphere. In addition, biogenic activities in Antarctica
also produce abundant gaseous P, such as phosphine, through anaerobic
microbial processes in soils and animal digestives, and phosphine gas can be
transformed to other low-volatility P-containing compounds in the atmosphere
or soils (Zhu et al., 2006). Primary biogenic aerosols, sea-salt
aerosols, and volcanic emissions could also contribute P to the atmosphere,
causing an elevated EFcrust for P (Zhao et al., 2015; Trabelsi
et al., 2016).
Non-crustal elements (Ca, Ni, Cu, Zn, Pb)
The enrichment factors of atmospheric Ni, Cu, Zn, and Pb relative to the
crustal element Al were found to be greater than 10 in some samples,
suggesting contributions from non-crustal sources during the corresponding
sampling periods in this study (Fig. 3). High enrichments of these
elements in Antarctica have commonly been associated with long-range
transport derived from anthropogenic emission (Boutron and Lorius, 1979;
Maenhaut et al., 1979; Dick, 1991; Artaxo et al., 1992; McConnell et al.,
2014; Xu and Gao, 2014). Aerosol Cu, Zn, and Pb are contributed primarily by
combustion or industrial activities (Pacyna and Pacyna, 2001). Strong
variations of the EFcrust of Cu, Zn, and Pb observed in snow samples at
Dome C, Antarctica, over the 20th century were attributed to volcanic
activities (Boutron and Lorius, 1979). On the other hand, heavy-oil
combustion was found to be a major source of aerosol Ni and V, and V/Ni
ratios are usually used to identify shipping emissions (Keywood et al.,
2020). Nevertheless, the V/Ni measured at Palmer Station ranged from 0.01 to
0.2, much lower than the V/Ni=3.2±0.8 characteristic of the
discharge from ship engines (Viana et al., 2009, 2014; Celo
et al., 2015). Hence, despite the recent increase in tourist ship traffic
(Lynch et al., 2010), it seems that Palmer Station was barely impacted
by ship emissions, which is consistent with the EFcrust of V. As a
common crustal element, Ca accounts for about 3.5 % of the weight of
Earth's crust (Taylor and McLennan, 1995), while Ca is also a
conservative major ion in seawater (Millero, 2016). The high EFcrust
for Ca at Palmer Station suggests that aerosol Ca was mainly derived from
sea salt.
Concentrations of trace elements
The concentrations of Ca and Al, the two major elements measured in this
study, were 1 to several orders of magnitude higher than other elements
(Table 1). To place all of the results of this study into the context of
past investigations, we provide a visual comparison of measured
concentrations of aerosol trace elements over Antarctica (Fig. 4).
Comparison of the concentrations of aerosol trace elements (ng m-3) over Antarctica at coastal land-based sites. The cruise from
Zhongshan Station to Casey Station was used to represent coastal East
Antarctica. All concentrations are sorted in descending order from left to
right. The left y axis shows concentrations for the black bars, whereas the
right y axis corresponds to the striped and white bars. Some extremely low
values are multiplied by 10 or 100 for display purposes, as marked above the
corresponding white bars. Error bars show the standard derivation of the
trace element concentrations in each study if available. Data are from
observations conducted at the South Pole (SP) (Zoller et al., 1974); Hut
Point site (MS1, PM10) and Radar Sat Dome site (MS2, PM10) at
McMurdo Station (Mazzera et al., 2001); on a cruise between Zhongshan
Station and Casey Station in coastal East Antarctica (CEA) (Xu and
Gao, 2014); at Neumayer Station (NS) (Weller et al., 2008); and at five
sites on the Antarctic Peninsula (AP), including Comandante Ferraz Antarctic
Station (KG1) (Artaxo et al., 1990, 1992) and King
Sejong Station (KG2) (Mishra et al., 2004) at King George Island,
Bernardo O'Higgins Station (OS, PM2.5) (Préndez et al.,
2009), Larsen Ice Shelf (LIS) (Dick, 1991), and Palmer Station (PS, this
study, marked by red arrow) at Anvers Island. Artaxo et al. (1990, 1992), Mazzera et al. (2001), and Préndez et al. (2009) used
X-ray fluorescence to measure the total concentrations of trace elements.
All the other studies applied acid digestion methods. Our study at Palmer
Station is marked in red.
Mineral dust (Al, P, Ti, V, Mn, Ce)
The concentrations of Al in aerosols varied from 1.2 to 7.9 ng m-3 with
an average of 4.3 ng m-3 during the 2016–2017 austral summer in this study.
These concentrations are lower than the 4-year mean Al values of
∼13 ng m-3 at King George Island (62∘ S,
58∘ W), at the northern end of the Antarctic Peninsula (Artaxo
et al., 1992), but were slightly higher than the 2-year mean Al
concentrations of 1.9 ng m-3 observed at King Sejong Station
(62∘ S, 59∘ W) (Mishra et al., 2004), the summer
mean of 0.194 ng m-3 at the Larsen Ice Shelf to the southeast of Palmer
Station (Dick et al., 1991), the 5-year summer mean of 1.3 ng m-3 in
East Antarctica (Weller et al., 2008), and the summer average of 0.57 ng m-3 measured at the South Pole (Zoller et al., 1974; Maenhaut et
al., 1979) (Fig. 4b). All these results, including ours, were much lower
than the average Al concentrations of 180 and 250 ng m-3
observed at the two sites at McMurdo Station (Mazzera et al., 2001) due
to the impact of the McMurdo Dry Valleys (Fig. 4b). The nearby McMurdo
Sound was reported as the dustiest site in Antarctica (Winton et al.,
2016). These aerosol Al concentrations are also lower than the average Al
concentration of 190 ng m-3 observed in coastal East Antarctica, where the
samples were also impacted by air masses passing over McMurdo regions
(Xu and Gao, 2014) (Fig. 4b). The concentrations of Ti ranged from
140 to 800 pg m-3 with an average of 250 pg m-3, while the
concentration of Mn ranged from 17 to 44 pg m-3 with an average of 30 pg m-3. Both Ti and Mn concentrations at Palmer Station were lower than
yearly mean concentrations at King George Island (average Ti: 1600 pg m-3; average Mn: 660 pg m-3) (Artaxo et al., 1992), and they
were also lower than the summer mean PM10 concentrations at McMurdo
Station (Ti: 26 000 pg m-3; Mn: 3000 pg m-3) (Mazzera et al.,
2001). However, these Ti and Mn values observed at Palmer Station were of
the same magnitude with the PM2.5 concentrations during the austral
summer near the Chilean base Bernardo O'Higgins, located on the northwest coast
of the Antarctic Peninsula (Préndez et al., 2009), and
with the concentrations in bulk aerosols over coastal East Antarctica in
austral summer (Mn: 450–1200 pg m-3 with an average of 700 pg m-3) (Xu and Gao, 2014) (Fig. 4e and g). The concentrations of
V ranged from 2.7 to 6.1 pg m-3 with a mean value of 4.2 pg m-3,
which is higher than the numbers reported at the South Pole (average
∼1.5 pg m-3) (Zoller et al., 1974; Maenhaut et al.,
1979) (Fig. 4f). However, the V concentration observed at Palmer Station
was much lower than previous observations in the North Atlantic Ocean (50–3170 pg m-3) (Fomba et al., 2013) and eastern Pacific Ocean (average 150 pg m-3) (Buck et al., 2019). On the other hand, Ce demonstrated
an average concentration of 1.3±0.69 pg m-3, which is
consistent with the Ce concentrations reported at Neumayer Station,
Antarctica (Weller et al., 2008) (Fig. 4k). The low concentrations of
aerosol V and Ce suggest that Palmer Station was not significantly
influenced by fossil fuel combustion. The P concentrations in aerosols
during this study ranged from 85 to 250 pg m-3 with an average of 150 ng m-3. The concentrations of aerosol P at Palmer Station were lower
than that at King George Island (3820 pg m-3) (Artaxo et al.,
1990). Comparing global aerosol P concentrations, we find that P
concentrations over the Antarctic Peninsula are in the same range as those
over the central Pacific Ocean (Chen, 2004). In this study, nss-K+
was used as a tracer of biomass burning (Winton et al.,
2015). The calculated nss-K+ was indistinguishable from 0,
suggesting that K+ in aerosol at Palmer Station was primarily
derived from seawater, not from biomass burning through long-range
transport. These results agree well with the air mass back trajectories,
which indicate that most samples collected during this study were barely
affected by South America (Fig. 5). In addition, for most of the 72 h
air mass back trajectories, the highest frequencies were found around the
northern Antarctic Peninsula, suggesting that aerosol crustal elements
observed at Palmer Station were impacted by sources in that region (Fig. 5).
Frequencies of 72 h air mass back trajectories for samples
collected at Palmer Station: M1 (19–26 November 2016), M2 (26 November–4 December 2016), M4 (9–17 December 2016), M5 (17–24 December 2016), M7 (1–8 January 2017), M8 (8–15 January 2017), M9 (15–23 January 2017),
and M10 (23–30 January 2017).
Concentrations of trace elements and ions in aerosols over Palmer Station, western Antarctic Peninsula.
The concentrations of Ni, Cu, Zn, and Pb were more variable than the
crustal elements. High levels of these elements would suggest an effect of a
polluted air mass derived from long-transport or regional air pollution
(Artaxo et al., 1992). The highest concentration of Ni observed during
this study was 320 pg m-3, with an average of 75 pg m-3, while the
lowest Ni concentration was below LOD (<20 pg m-3). Samples M2
and M10 showed relatively high values of Ni of 320 and 200 pg m-3,
respectively, while the concentrations of Ni in M1, M5, and M6 were much
lower, ranging from 17 to 37 pg m-3. The concentrations of Cu varied
from <20–480 pg m-3 (average 150 pg m-3), while Zn
ranged from <30–710 pg m-3 (average 200 pg m-3). These
results indicate that the concentrations of these elements in aerosols
varied dramatically throughout the study period, likely affected by the
source strength and meteorological conditions. From the air mass back
trajectories, the samples with high Ni (M2, M10), Cu (M1, M2, M4, M10), and
Zn (M5) all were impacted by a significant amount of air masses from the South
Pacific Ocean and South America (Fig. 5). The back trajectories of air
masses of M7 did not touch South America, but the concentration of Zn in this
sample was high. Given the fact that aerosol Zn was found in both fine- and
coarse-mode fractions (Table 2), both local sources and long-range transport
may contribute to this element in the air. Artaxo et al. (1992)
collected aerosol samples using a two-stage size-segregated sampler and
observed high concentrations of Ni, Cu, and Zn – with averages of 240, 790, and
7200 pg m-3, respectively – at King George Island in summertime (Fig. 4h, i and j),
much higher than the results from this study. The high concentrations may
have resulted from local polluted dust emissions around their sampling site
(Hong et al., 1999). In addition, their sampling site was considerably
north of Palmer Station and may be more likely to be impacted by air masses
from South America (Chambers et al., 2014). In South America, high
enrichment of Ni, Cu, Zn, and Pb in fine-mode particles was reported to be
primarily associated with vehicle emission, soil dust, and oil combustion
(Artaxo et al., 1999; Jasan et al., 2009). Moreover, miming activities
were suggested as an important source, especially at remote sites in South
America (Carrasco and Préndez, 1991; Klumpp et al., 2000). On the
other hand, the concentrations of Ni, Cu, and Zn at Palmer Station were
lower than at some other sites in Antarctica. At McMurdo Station, the average
concentrations of Cu and Zn in PM10 samples were 200 and 1200 pg m-3 (Mazzera et al., 2001) (Fig. 4i and j). Over coastal East
Antarctica, the Ni concentrations in aerosols ranged from <3 to
2200 pg m-3 with an average of 750 pg m-3 (Xu and Gao, 2014)
(Fig. 4h).
The concentrations of aerosol Pb observed at Palmer Station ranged from 5.0
to 60 pg m-3 with an average of 19 pg m-3, higher than the average
concentration of 4.7 pg m-3 previously observed on the east coast of
the Antarctic Peninsula in austral summer (Dick, 1991) (Fig. 4l) and
the annual average concentration of 11 pg m-3 in Tasmania
(Bollhöfer et al., 2005). However, the average
Pb concentration reported at King George Island was about 800 pg m-3
(Artaxo et al., 1992), considerably higher than observed in this study
(Fig. 4l). The two highest Pb concentrations observed during this study
were in M4 (60 pg m-3) and M5 (30 pg m-3). The results of air mass
back trajectories for M4 and M5 show that the air masses were derived in
part from South America, which suggests additional contribution from
long-range transport (Fig. 5b and c). However, when the 72 h air mass
back trajectories did not intersect the South American continent, the
concentrations of Pb in those samples were significantly lower (Fig. 5a
and d). The low concentrations of Pb observed in samples associated with air
masses that did not pass over southern South America suggest that local
anthropogenic emissions were negligible. Thus the major source of
non-crustal elements in aerosols over the study region may be long-range
transport of aerosols from southern hemispheric continental regions
containing a mixture of anthropogenic and crustal emissions.
Sea-salt aerosol (Ca, Na+, K+)
The concentrations of sea-salt species were much higher than the other trace
elements (Table 1). The concentrations of aerosol Ca were the highest among
all elements measured in this study (range of 16–53 ng m-3 and mean value
of 30 ng m-3). The mean value of Ca is close to the mean Ca
concentrations observed previously in coastal regions of the Antarctic
Peninsula (Artaxo et al., 1992; Weller et al., 2008) (Fig. 4d). In
addition, Na+, as a tracer of sea salt, and K+, as a tracer of
biomass burning (Zhu et al., 2015), were used to further evaluate the
contribution of trace elements from other sources. The concentrations of
Na+ and K+ showed average concentrations of 890±310 and 28±11 ng m-3, respectively. Thus, the Na+/K+ (32±3.5) ratios were close to the average Na/K mass ratio in seawater (27) and
the Na+/Ca ratios (31±5.5) were close to the average
Na+/Ca ratio in seawater (26) as well (Millero, 2016). Such results
agree well with the Na/K (29.7) and Na/Ca (39.9) ratios measured in snow
samples collected at James Ross Island (Aristarain et al., 1982).
Therefore, the Ca and K+ in aerosols were derived primarily from sea
salt at Palmer Station.
The results of k-means clustering on the normalized mean aerosol
particle-size distributions. The crustal cluster includes Ti, V, Mn, and Ce;
the sea-salt cluster includes Na+, K+, and Ca.
Aerosol particle-size distributions of trace elements
The concentrations of trace elements in aerosols observed during this study
varied as a function of particle size. We applied k-means clustering to the
full data set, and the results indicate that aerosol trace elements in the
austral summer at Palmer Station can be classified into five groups based on
their normalized particle-size distributions (Fig. 6), with each group
showing a unique size distribution pattern: (1) crustal elements from
crustal weathering and wind-induced resuspension of soil particles, (2) Al
dominated by local minerals, (3) Pb from anthropogenic sources as a result
of long-range transport, (4) sea-salt elements from the ocean through
bursting bubbles of seawater, and (5) P from local biogenic and soil
resuspension. The particle-size distribution of each element can be
classified as single mode, bimodal, or trimodal, which hints that the
elements derived from distinct sources or experienced different processes
during the transport to the sampling site.
Particle-size distributions of the trace elements showing
single-mode distribution in aerosols during November 2016–January 2017 austral
summer over Palmer Station. dC/dlog(Dp) is the normalized
concentration.
Single-mode distribution
The particle-size distributions of Na+, P, K+, Ca, Ti, and Ce
showed a clear single coarse-mode distribution (Fig. 7). As conservative
species in seawater, Na+, K+, and Ca were likely dominated by
sea-salt aerosols and all had a coarse primary mode at approximately 2.5–4.4 µm. Such a pattern agrees well with the particle-size distributions
of sea-salt aerosols measured in coastal East Antarctica (Xu et al.,
2013). Similarly, Ti and Ce derived from crustal emission were dominated by
coarse-mode particles, peaking at around 4.4 µm. The aerosol P had a
slightly shifted single-mode distribution and peaked between the coarse-mode
crustal aerosol and the sea-salt aerosol at around 2.5–4.4 µm.
Consequently, P was likely controlled by a regional emission source, such as
soil resuspension. Given that gravitational settling greatly limits the
residence time of coarse-mode particles compared with fine-mode particles,
the elements with single coarse-mode distribution are likely to have a
relatively proximal dominant source, such as the ice-free areas in the
Antarctic Peninsula during austral summer.
Particle-size distributions of the trace elements showing bimodal
and trimodal distribution in aerosols during November 2016–January 2017 austral
summer over Palmer Station. dC/dlog(Dp) is the normalized
concentration.
Bimodal distribution
Although V and Mn also had a single-mode distribution in most samples,
bimodal distribution was found in a few samples, hinting at contributions
from multiple sources (Fig. 8). The particle-size distribution of V and Mn
primarily peaked around 4.4 µm, while a small fine-mode peak could be
seen around 0.14–0.25 µm in sample M2 and M4 for V, and a similar
fine-mode peak is also present in M4 for Mn. A different Mn particle-size
distribution was dominated by particles larger than 18 µm, which is
similar to Al and will be discussed below in Sect. 3.3.3. As we concluded
above, V and Mn were dominated by crustal emission, and the coarse primary
mode indicates regional crustal sources. As the size of dust particles
decreases with distance away from the sources due to the higher deposition
rates of coarse particles (Duce et al., 1991; Baker and Jickells, 2006),
the fine-mode peaks are likely caused by additional input from long-range
transport. The particle-size distribution of V in M2 showed a unique peak in
the fine-mode range. In addition, M2 had the highest concentrations of Ni
and Cu among all the samples. The air mass back trajectories suggested a
contribution from the South Pacific Ocean and coastal South America. This
suggests that the fine-mode particles in M2 might be influenced by the
remote anthropogenic emissions. By contrast, the air mass back trajectories
for M4 directly passed the South American continent. An elevated Pb
concentration and fine-mode peaks in Al and Pb size distributions were
observed also in M4. Such results suggest M4 may have received polluted dust
derived from South America.
Trimodal distribution
Aerosol Pb showed bimodal and trimodal distributions in this study (Fig. 8). Compared with the other elements, the primary mode of Pb was much finer
and peaked at around 0.14–0.25 µm. The primary fine-mode fractions
of aerosol Pb in some samples suggest that aerosol Pb at Palmer Station was
occasionally dominated by anthropogenic sources as Pb is usually
concentrated in fine particles from industrial or traffic emissions
(Mamun et al., 2020). Air mass back trajectories also suggest the high
Pb samples (M4, M5) received air mass derived from southern South America
through long-range transport. The secondary mode of Pb was found around the
same size as the crustal elements (approximately 4.4 µm), indicating
a possible regional emission, including both crustal sources and local
contaminated soil (Santos et al., 2005). In addition, a tertiary mode
was observed in M4 and peaked around 0.78–1.4 µm. Considering M4
was influenced by long-range transport, Pb in this size range may be
dominated by distinct remote sources. Thus Pb at Palmer Station was largely
controlled by remote sources in South America. Because Pb was dominated by
fine particles, an extremely small dry deposition velocity would be expected
(Table 2). This might explain why previous studies in the Antarctic
Peninsula suggested aerosol Pb was contributed by remote anthropogenic
emission (Dick, 1991), whereas Pb in snow appeared to be associated with
natural aerosols (Suttie and Wolff, 1992).
The average Al particle-size distribution showed trimodal distribution with
a primary mode at particle size larger than 18 µm, a secondary mode
around 4.4 µm, and a tertiary mode around 0.14–0.25 µm
(Fig. 8). A single-mode Al particle-size distribution peaked at around 4.4 µm, which shared the same size with the primary mode of Ti, V, Mn, and
Ce in samples M8 and M9, indicating the regional crustal emissions.
An additional high peak (>18µm) was found in M1, M2, and M7
that contributed to bimodal distribution. A similar distribution can be seen
in the Mn distribution of M2. We speculate that high Al concentrations
associated with large particles might be caused by local soil resuspension
around the sampling site, introducing large Al-containing particles that may
come from aluminosilicate minerals. Such large Al-containing particles may
not be unusual, as large-size dust particles were found in Antarctic snow
(Winton et al., 2016). Trimodal distribution involved another mode in
fine particles, approximately 0.14–0.25 µm, in M4 and M5. The high
fine-mode Al of M4 and M5 likely derives from long-range transport from
South America, which matches with the two highest Pb concentrations in this
study.
Particle-size distribution of mineral dust in Antarctica
Although the particle-size distributions of crustal elements (Al, Ti, V, Mn,
Ce) have been reported only rarely for Antarctica, the particle-size
distributions of mineral dust in aerosols, snow, and ice core samples were
studied at several sites. The crustal aerosols sampled at Aboa research
station, East Antarctica, had a single-mode distribution peaking at a particle
size larger than 8.5 µm (Virkkula et al., 2006). In addition, the
grain size distribution of dust particles in snow collected at Berkner
Island was largely dominated by particles larger than 5 µm,
suggesting a significantly higher proportion of dust was in coarse mode than
the previous size distribution observed at Kohnen Station, East Antarctic
Plateau (Bory et al., 2010). Similarly, at Roosevelt Island, the particle-size
distributions of dust particles in snow were primarily dominated by
coarse particles, possibly larger than 9 µm (Winton et al.,
2016). Likewise, the dust particle-size distribution at Dome C during the
Last Glacial Maximum and the Holocene showed single mode and peaked at
approximately 2–3 µm in ice core samples (∼3233 m
above sea level) (Delmonte et al., 2002; Potenza et al., 2016).
Therefore, the dust particle-size distributions measured in coastal
Antarctic regions are usually concentrated in coarse particles, whereas the
dust particle-size distributions of inland Antarctic regions, with longer
pathways from the sources, show peaks in relatively finer particles.
Estimates of dry deposition velocities and dry deposition fluxes of trace elements in aerosols over Palmer Station, western Antarctic Peninsula.
* The range of dry deposition fluxes of Ni, Cu, and Zn was estimated based on Pb and Al dry deposition velocities, discussed in the text.
Atmospheric dry deposition fluxes
Aerosol particle-size distributions have been used to estimate atmospheric
dry deposition fluxes of aerosol Fe to the Southern Ocean and coastal
Antarctica (Gao et al., 2013, 2020). Similarly, the dry deposition fluxes
of aerosol trace elements were estimated in this study (Table 3). Given that
the sea-salt elements were the most abundant, Ca showed the highest dry
deposition flux, which varied from 0.59 to 6.6 mg m-2 yr-1 with an
average of 1.2±0.7 mg m-2 yr-1. At the other extreme, due
to low concentration and fine-mode particle dominance, aerosol Pb showed
∼5000-fold lower dry deposition fluxes with a mean of 0.30±0.23µgm-2yr-1. The rough estimates of the dry
deposition fluxes of Ni and Zn at Palmer Station are close to the median
deposition fluxes found in the western North Atlantic Ocean (Ni: 18 µgm-2yr-1; Zn: 16 µgm-2yr-1), whereas the dry
deposition flux of Cu is slightly higher than the median Zn dry deposition
flux (2.8 µgm-2yr-1) in the western North Atlantic Ocean
(Shelley et al., 2017). However, the dry deposition flux of Cu at
Palmer Station is in the lower range of that observed in the eastern North
Atlantic Ocean, 3.97–194 µgm-2yr-1 (Buck et al.,
2019). The estimated dry deposition fluxes of total continental dust at
Palmer station ranged from 0.65 to 28 mg m-2 yr-1 with a mean of
5.5±5.1 mg m-2 yr-1, and this flux is only around 10 %
of the mean global dust deposition flux at remote sites (Lawrence and
Neff, 2009). Previous modeling studies estimated that wet deposition of
dust through precipitation scavenging accounted for about 40–60 % of the total deposition in the coastal and open oceans in the mid- and
low-latitude oceans (Gao et al., 2003), and a similar wet deposition
fraction was found in the Southern Ocean and coastal East Antarctica
(Gao et al., 2013). Although precipitation varies in different
regions, this is the best estimate we have for Antarctic regions. Assuming
this wet deposition fraction (0.4–0.6) applies to the Antarctic Peninsula
region, we approximate roughly a total dust flux of 10±10 mg m-2 yr-1. This value is at the lower end of the dust flux range,
∼5 to ∼50 mg m-2 yr-1, estimated
from ice core measurements at James Ross Island on the Antarctic Peninsula
over the 20th century (McConnell et al., 2007), but it is higher than
dust deposition flux at Dome C (0.2–0.6 mg m-2 yr-1) (Lambert
et al., 2012) and at Talos Dome (0.70–7.24 mg m-2 yr-1)
(Albani et al., 2012) as well as the model estimate for this region (1.8–3.7 mg m-2 yr-1) (Wagener et al., 2008). Considering active dust
sources were reported at James Ross Island (Kavan et al., 2018), sites
close to James Ross Island are likely to receive higher dust deposition
fluxes. In addition, without measurements of wet deposition, the total dust
deposition flux in our study could be underestimated. Compared with the
global data, the dust deposition flux at Palmer Station is far lower than
the total dust deposition fluxes in the North and South Atlantic Ocean
(minimum of 270 and 150 mg m-2 yr-1, respectively) (Menzel Barraqueta et
al., 2019), South Pacific Ocean (230 mg m-2 yr-1)
(Prospero, 1989), South Indian Ocean (240 mg m-2 yr-1)
(Heimburger et al., 2012), and McMurdo Dry Valleys (490 mg m-2 yr-1) (Lancaster, 2002), while it is close to the estimated total
dust deposition fluxes for the 63∘ S region (between 62∘53′ S and 63∘53′ S, along 170∘6′ W; 33 mg m-2 yr-1) (Measures and Vink, 2000). Accordingly, the other crustal
elements (P, Ti, V, Mn, Ce) were proportional to the dust dry deposition
flux and showed extremely low values.
To examine the potential importance of atmospheric dust input to the
particulate elemental concentrations in surface waters of the western Antarctic
Peninsula shelf region, the maximum possible suspended particulate Al
concentrations in surface seawater contributed by dust were estimated. We
used the maximum Al dry deposition flux of 2300 µgm-2yr-1
(Table 3), assumed that dry deposition accounted for 40 % of total
deposition (Gao et al., 2003), and assumed no settling loss from the
mixed layer of mean depth 24 m (Eveleth et al., 2017) over a 4-month
summer season. By this calculation, the accumulated concentration of
suspended particulate Al contributed by total atmospheric deposition over
this period is 3 nmol kg-1. While suspended Al reaches 135 nmol kg-1 in coastal surface waters close to the peninsula, outer shelf and
off-shelf surface waters generally have concentrations <5 nmol kg-1 (Annett et al., 2017), suggesting that this upper-limit-estimated dust flux could account for a substantial portion of observed
surface ocean lithogenic particle concentration. While the mean Al flux is
just 20 % of this maximum, and settling loss from the mixed layer over the
course of the summer may be significant, it is also possible that the
residence time of particulate Al in the surface layer exceeds the summer
season, by analogy to the North Atlantic (Jickells, 1999), allowing
greater accumulation and concentrations than our simple calculation
indicates. This rough estimate suggests that atmospheric dust deposition,
possibly dominated by regional sources on the Antarctic continent itself,
may contribute a significant fraction of suspended particulate
concentrations of lithogenic elements in the surface waters of the outer
shelf and the proximal pelagic Southern Ocean.
Conclusions and implications
Results from this study indicate that trace elements in aerosols over Palmer
Station during the austral summer were primarily derived from (1) the
regional crustal sources, which includes P-enriched soil resuspension; (2) remote anthropogenic emissions in South America; and (3) seawater. Remote
crustal sources and local contaminated soil may also contribute to aerosol
trace elements at Palmer Station. The particle-size distributions of crustal
elements – including Al, P, Ti, V, Mn, and Ce – were all concentrated in
coarse mode, suggesting strong regional emissions likely from ice-free areas
on the Antarctic Peninsula and its associated islands. In some samples, Al,
V, and Mn also had a secondary peak in the fine-mode fraction, likely
derived from a distinct source through long-range transport. We speculate
that the modest enrichment of aerosol P over its crustal ratio to Al was
caused by the resuspension of regional soils that are P-enriched as a result
of the impact of nearby bird colonies. The elements Ca, Na+, and
K+ had a single coarse-mode distribution, likely derived from
sea salt. Conversely, the size distribution of Pb occurred primarily in
fine mode. The air mass back trajectories show that samples with high
concentrations of Ni, Cu, Zn, and Pb were influenced by air masses passing
through southern South America and the South Pacific Ocean. The total dust
deposition flux (∼10 mg m-2 yr-1) during austral
summer, estimated from the Al concentrations obtained in this study and an
assumption of relative wet deposition, suggests that dust deposition plays a
minor role in the concentrations of trace elements in coastal seawater
around the western Antarctic Peninsula but may be more important in offshore
regions. As the role of wet deposition is unquantified at present and
remains poorly constrained for this region, the total deposition fluxes of
trace elements during the austral summer could exceed the dry deposition
fluxes reported here. Therefore, the importance of atmospheric deposition of
trace elements to the coastal western Antarctic Peninsula may need to be
re-evaluated with additional observations of wet deposition. The Antarctic
Peninsula is experiencing rapid climate change, with the expansion of
ice-free areas and more frequent shipboard tourism with unknown impacts on
aerosol chemistry in this region. To quantify future changes in the
atmospheric position and the impact in this region, long-term atmospheric
observations of aerosol chemical and physical properties along with coupled
studies of the ocean–atmosphere interactions would be needed.
Data availability
The data used in this paper have been submitted to the US Antarctic
Program Data Center (10.15784/601370, Gao, 2020).
The supplement related to this article is available online at: https://doi.org/10.5194/acp-21-2105-2021-supplement.
Author contributions
YG conceived the research. YG and SY prepared field sampling and collected
aerosol samples. SF and YG digested samples. KB and RMS conducted sample
analyses. SF wrote the first draft of the manuscript. YG and RMS edited the
drafts. All authors contributed to writing and approved the submission.
Competing interests
The authors declare that they have no conflict of interest.
Acknowledgements
We thank Hugh Ducklow for encouragement of this research; Rafael Jusino-Atresino, Pami Mukherjee, and Guojie Xu for participating in fieldwork
preparation; and Jianqiong Zhan for assisting with meteorological data
analyses. This work would not have become possible without the dedication
and support from the staff of Palmer Station and the US Antarctic Program. We also appreciate the constructive comments from Holly Winton and an anonymous reviewer.
Financial support
This research was supported by the US National Science Foundation (grant no. OPP1341494 to Yuan Gao).
Review statement
This paper was edited by Leiming Zhang and reviewed by Holly Winton and one anonymous referee.
ReferencesAbram, N. J., Mulvaney, R., Wolff, E. W., Triest, J., Kipfstuhl, S.,
Trusel, L. D., Vimeux, F., Fleet, L., and Arrowsmith, C.: Acceleration of
snow melt in an Antarctic Peninsula ice core during the twentieth century,
Nat. Geosci., 6, 404–411, 10.1038/ngeo1787, 2013.Adebiyi, A. A. and Kok, J. F.: Climate models miss most of the coarse dust
in the atmosphere, Sci. Adv., 6, eaaz9507, 10.1126/sciadv.aaz9507, 2020.Albani, S., Delmonte, B., Maggi, V., Baroni, C., Petit, J.-R., Stenni, B., Mazzola, C., and Frezzotti, M.: Interpreting last glacial to Holocene dust changes at Talos Dome (East Antarctica): implications for atmospheric variations from regional to hemispheric scales, Clim. Past, 8, 741–750, 10.5194/cp-8-741-2012, 2012.
Annett, A. L., Fitzsimmons, J. N., Séguret, M. J., Lagerström, M.,
Meredith, M. P., Schofield, O., and Sherrell, R. M.: Controls on dissolved
and particulate iron distributions in surface waters of the Western
Antarctic Peninsula shelf, Mar. Chem., 196, 81–97, 2017.
Arimoto, R., Zeng, T., Davis, D., Wang, Y., Khaing, H., Nesbit, C., and
Huey, G.: Concentrations and sources of aerosol ions and trace elements
during ANTCI-2003, Atmos. Environ., 42, 2864–2876, 2008.
Aristarain, A. J., Delmas, R. J., and Briat, M.: Snow chemistry on James
Ross Island (Antarctic Peninsula), J. Geophys. Res.-Ocean.,
87, 11004–11012, 1982.
Artaxo, P., Andrade, F., and Maenhaut, W.: Trace elements and receptor
modelling of aerosols in the Antarctic Peninsula, Nucl. Instrum. Meth. B, 49, 383–387, 1990.
Artaxo, P., Rabello, M. L., Maenhaut, W., and Grieken, R. V.: Trace elements
and individual particle analysis of atmospheric aerosols from the Antarctic
Peninsula, Tellus B, 44, 318–334, 1992.
Artaxo, P., Oyola, P., and Martinez, R.: Aerosol composition and source
apportionment in Santiago de Chile, Nucl. Instrum. Meth. B, 150,
409–416, 1999.
Asmi, E., Neitola, K., Teinilä, K., Rodriguez, E., Virkkula, A.,
Backman, J., Bloss, M., Jokela, J., Lihavainen, H., and De Leeuw, G.:
Primary sources control the variability of aerosol optical properties in the
Antarctic Peninsula, Tellus B, 70, 1–16, 2018.Baker, A. and Jickells, T.: Mineral particle size as a control on aerosol
iron solubility, Geophys. Res. Lett., 33, L17608, 10.1029/2006GL026557, 2006.Baker, A. R., Li, M., and Chance, R.: Trace metal fractional solubility in
size-segregated aerosols from the tropical eastern Atlantic Ocean, Glob.
Biogeochem. Cy., 34, e2019GB006510, 10.1029/2019GB006510, 2020.
Blecker, S., Ippolito, J., Barrett, J., Wall, D., Virginia, R., and Norvell,
K.: Phosphorus fractions in soils of Taylor Valley, Antarctica, Soil Sci.
Soc. Am. J., 70, 806–815, 2006.
Bockheim, J., Vieira, G., Ramos, M., López-Martínez, J., Serrano,
E., Guglielmin, M., Wilhelm, K., and Nieuwendam, A.: Climate warming and
permafrost dynamics in the Antarctic Peninsula region, Glob. Planet.
Change, 100, 215–223, 2013.
Boës, X., Rydberg, J., Martinez-Cortizas, A., Bindler, R., and Renberg,
I.: Evaluation of conservative lithogenic elements (Ti, Zr, Al, and Rb) to
study anthropogenic element enrichments in lake sediments, J.
Paleolimnol., 46, 75–87, 2011.Bollhöfer, A. F., Rosman, K. J. R., Dick, A. L., Chisholm, W., Burton,
G. R., Loss, R. D., and Zahorowski, W.: Concentration, isotopic composition,
and sources of lead in Southern Ocean air during 1999/2000, measured at the
Cape Grim Baseline Air Pollution Station, Tasmania, Geochim.
Cosmochim. Ac., 69, 4747–4757,
10.1016/j.gca.2005.06.024, 2005.
Bory, A., Wolff, E., Mulvaney, R., Jagoutz, E., Wegner, A., Ruth, U., and
Elderfield, H.: Multiple sources supply eolian mineral dust to the Atlantic
sector of coastal Antarctica: Evidence from recent snow layers at the top of
Berkner Island ice sheet, Earth Planet. Sci. Lett., 291, 138–148,
2010.Boutron, C. and Lorius, C.: Trace metals in Antarctic snows since 1914,
Nature, 277, 551–554, 10.1038/277551a0, 1979.
Bridgestock, L., Van De Flierdt, T., Rehkämper, M., Paul, M., Middag,
R., Milne, A., Lohan, M. C., Baker, A. R., Chance, R., and Khondoker, R.:
Return of naturally sourced Pb to Atlantic surface waters, Nat.
Commun., 7, 1–12, 2016.Bromwich, D. H., Nicolas, J. P., Monaghan, A. J., Lazzara, M. A., Keller, L.
M., Weidner, G. A., and Wilson, A. B.: Central West Antarctica among the
most rapidly warming regions on Earth, Nat. Geosci., 6, 139–145, 10.1038/ngeo1671, 2013.
Buck, C. S., Landing, W. M., and Resing, J. A.: Particle size and aerosol
iron solubility: A high-resolution analysis of Atlantic aerosols, Mar.
Chem., 120, 14–24, 2010.
Buck, C. S., Aguilar-Islas, A., Marsay, C., Kadko, D., and Landing, W. M.:
Trace element concentrations, elemental ratios, and enrichment factors
observed in aerosol samples collected during the US GEOTRACES eastern
Pacific Ocean transect (GP16), Chem. Geol., 511, 212–224, 2019.
Caliński, T. and Harabasz, J.: A dendrite method for cluster analysis,
Commun. Stat. Theor. M., 3, 1–27, 1974.
Campbell, I. B. and Claridge, G.: Antarctica: soils, weathering processes
and environment, Elsevier, Amsterdam, 1987.
Carrasco, M. A. and Préndez, M.: Element distribution of some soils of
continental Chile and the Antarctic peninsula. Projection to atmospheric
pollution, Water Air Soil Pollut., 57, 713–722, 1991.
Celo, V., Dabek-Zlotorzynska, E., and McCurdy, M.: Chemical characterization
of exhaust emissions from selected Canadian marine vessels: the case of
trace metals and lanthanoids, Environ. Sci. Technol., 49,
5220–5226, 2015.Chambers, S. D., Hong, S.-B., Williams, A. G., Crawford, J., Griffiths, A. D., and Park, S.-J.: Characterising terrestrial influences on Antarctic air masses using Radon-222 measurements at King George Island, Atmos. Chem. Phys., 14, 9903–9916, 10.5194/acp-14-9903-2014, 2014.Chen, Y.: Sources and fate of atmospheric nutrients over the remote oceans
and their role on controlling marine diazotrophic microorganisms, Doctoral dissertation, available at: https://drum.lib.umd.edu/handle/1903/1967 (last access: 29 January 2021), 2004.Chen, Y. and Siefert, R. L.: Seasonal and spatial distributions and dry
deposition fluxes of atmospheric total and labile iron over the tropical and
subtropical North Atlantic Ocean, J. Geophys. Res.-Atmos., 109, D09305, 10.1029/2003JD003958, 2004.Chuang, P., Duvall, R., Shafer, M., and Schauer, J.: The origin of water
soluble particulate iron in the Asian atmospheric outflow, Geophys.
Res. Lett., 32, L07813, 10.1029/2004GL021946, 2005.
Cook, A. J., Holland, P., Meredith, M., Murray, T., Luckman, A., and
Vaughan, D. G.: Ocean forcing of glacier retreat in the western Antarctic
Peninsula, Science, 353, 283–286, 2016.Crusius, J., Schroth, A. W., Gasso, S., Moy, C. M., Levy, R. C., and Gatica,
M.: Glacial flour dust storms in the Gulf of Alaska: Hydrologic and
meteorological controls and their importance as a source of bioavailable
iron, Geophys. Res. Lett., 38, L06602, 10.1029/2010GL046573, 2011.
Delmonte, B., Petit, J., and Maggi, V.: Glacial to Holocene implications of
the new 27 000-year dust record from the EPICA Dome C (East Antarctica) ice
core, Clim. Dynam., 18, 647–660, 2002.Delmonte, B., Winton, H., Baroni, M., Baccolo, G., Hansson, M., Andersson,
P., Baroni, C., Salvatore, M. C., Lanci, L., and Maggi, V.: Holocene dust in
East Antarctica: Provenance and variability in time and space, Holocene,
30, 546–558, 10.1177/0959683619875188, 2020.
Dick, A.: Concentrations and sources of metals in the Antarctic Peninsula
aerosol, Geochim. Cosmochim. Ac., 55, 1827–1836, 1991.
Dick, A. and Peel, D.: Trace elements in Antarctic air and snowfall, Ann.
Glaciol., 7, 12–19, 1985.
Duce, R., Liss, P., Merrill, J., Atlas, E., Buat-Menard, P., Hicks, B.,
Miller, J., Prospero, J., Arimoto, R., and Church, T.: The atmospheric input
of trace species to the world ocean, Glob. Biogeochem. Cy., 5,
193–259, 1991.
Duce, R. A. and Tindale, N. W.: Atmospheric transport of iron and its
deposition in the ocean, Limnol. Oceanogr., 36, 1715–1726, 1991.
Eveleth, R., Cassar, N., Sherrell, R., Ducklow, H., Meredith, M., Venables,
H., Lin, Y., and Li, Z.: Ice melt influence on summertime net community
production along the Western Antarctic Peninsula, Deep-Sea Res. Pt. II, 139, 89–102, 2017.Fomba, K. W., Müller, K., van Pinxteren, D., and Herrmann, H.: Aerosol size-resolved trace metal composition in remote northern tropical Atlantic marine environment: case study Cape Verde islands, Atmos. Chem. Phys., 13, 4801–4814, 10.5194/acp-13-4801-2013, 2013.
Gantt, B., Hoque, S., Willis, R. D., Fahey, K. M., Delgado-Saborit, J. M.,
Harrison, R. M., Erdakos, G. B., Bhave, P. V., Zhang, K. M., and Kovalcik,
K.: Near-road modeling and measurement of cerium-containing particles
generated by nanoparticle diesel fuel additive use, Environ. Sci. Technol., 48, 10607–10613, 2014.Gao, Y.: Concentrations and Particle Size Distributions of Aerosol Trace Elements, U.S. Antarctic Program (USAP) Data Center, 10.15784/601370, 2020.Gao, Y., Fan, S., and Sarmiento, J.: Aeolian iron input to the ocean through
precipitation scavenging: A modeling perspective and its implication for
natural iron fertilization in the ocean, J. Geophys. Res.-Atmos., 108, 4221, 10.1029/2002JD002420, 2003.Gao, Y., Xu, G., Zhan, J., Zhang, J., Li, W., Lin, Q., Chen, L., and Lin,
H.: Spatial and particle size distributions of atmospheric dissolvable iron
in aerosols and its input to the Southern Ocean and coastal East Antarctica,
J. Geophys. Res.-Atmos., 118, 12634–12648,
10.1002/2013jd020367, 2013.
Gao, Y., Marsay, C. M., Yu, S., Fan, S., Mukherjee, P., Buck, C. S., and
Landing, W. M.: Particle-Size Variability of Aerosol Iron and Impact on Iron Solubility and Dry Deposition Fluxes to the Arctic Ocean, Sci. Rep.-UK,
9, 1–11, 2019.Gao, Y., Yu, S., Sherrell, R. M., Fan, S., Bu, K., and Anderson, J. R.:
Particle-Size Distributions and Solubility of Aerosol Iron Over the
Antarctic Peninsula During Austral Summer, J. Geophys. Res.-Atmos., 125, e2019JD032082, 10.1029/2019jd032082, 2020.
Gras, J.: CN, CCN and particle size in Southern Ocean air at Cape Grim,
Atmos. Res., 35, 233–251, 1995.Guieu, C., Bonnet, S., Wagener, T., and Loÿe-Pilot, M. D.: Biomass
burning as a source of dissolved iron to the open ocean?, Geophys.
Res. Lett., 32, L19608, 10.1029/2005GL022962, 2005.Heimburger, A., Losno, R., Triquet, S., Dulac, F., and Mahowald, N.: Direct
measurements of atmospheric iron, cobalt, and aluminum-derived dust
deposition at Kerguelen Islands, Glob. Biogeochem. Cy., 26, GB4016, 10.1029/2012GB004301, 2012.Herenz, P., Wex, H., Mangold, A., Laffineur, Q., Gorodetskaya, I. V., Fleming, Z. L., Panagi, M., and Stratmann, F.: CCN measurements at the Princess Elisabeth Antarctica research station during three austral summers, Atmos. Chem. Phys., 19, 275–294, 10.5194/acp-19-275-2019, 2019.
Hong, S., Kang, C. Y., and Kang, J.: Lichen Biomonitoring for the Detection
of Local Heavy Metal Pollution around King Sejong Station, King George
Island, Antarctica, Korean J. Polar Res., 10, 17–24, 1999.Järvinen, E., Virkkula, A., Nieminen, T., Aalto, P. P., Asmi, E., Lanconelli, C., Busetto, M., Lupi, A., Schioppo, R., Vitale, V., Mazzola, M., Petäjä, T., Kerminen, V.-M., and Kulmala, M.: Seasonal cycle and modal structure of particle number size distribution at Dome C, Antarctica, Atmos. Chem. Phys., 13, 7473–7487, 10.5194/acp-13-7473-2013, 2013.
Jasan, R., Plá, R., Invernizzi, R., and Dos Santos, M.: Characterization
of atmospheric aerosol in Buenos Aires, Argentina, J.
Radioanal. Nucl. Ch., 281, 101–105, 2009.
Jickells, T. D.: The inputs of dust derived elements to the Sargasso Sea; a synthesis, Marine Chem., 68, 5–14, 1999.
Jickells, T. and Moore, C. M.: The importance of atmospheric deposition for
ocean productivity, Annu. Rev. Ecol. Evol. S., 46, 481–501, 2015.Jickells, T., Baker, A., and Chance, R.: Atmospheric transport of trace
elements and nutrients to the oceans, Philos. T.
R. Soc. A., 374, 20150286, 10.1098/rsta.2015.0286, 2016.
Kaufman, Y. J., Tanré, D., and Boucher, O.: A satellite view of aerosols
in the climate system, Nature, 419, 215–223, 2002.Kavan, J., Dagsson-Waldhauserova, P., Renard, J.-B., Laska, K., and
Ambrožová, K.: Aerosol concentrations in relationship to local
atmospheric conditions on James Ross Island, Antarctica, Front. Earth Sci., 6, 10.3389/feart.2018.00207, 2018.Keywood, M., Hibberd, M. F., Selleck, P. W., Desservettaz, M., Cohen, D. D.,
Stelcer, E., Atanacio, A. J., Scorgie, Y., and Tzu-Chi Chang, L.: Sources of
Particulate Matter in the Hunter Valley, New South Wales, Australia,
Atmosphere-Basel, 11, 4, 10.3390/atmos11010004, 2020.Kim, J., Yoon, Y. J., Gim, Y., Kang, H. J., Choi, J. H., Park, K.-T., and Lee, B. Y.: Seasonal variations in physical characteristics of aerosol particles at the King Sejong Station, Antarctic Peninsula, Atmos. Chem. Phys., 17, 12985–12999, 10.5194/acp-17-12985-2017, 2017.
Klumpp, A., Domingos, M., and Pignata, M. L.: Air pollution and vegetation
damage in South America–state of knowledge and perspectives, CRC Press
LLC, USA, 2000.Lachlan-Cope, T., Beddows, D. C. S., Brough, N., Jones, A. E., Harrison, R. M., Lupi, A., Yoon, Y. J., Virkkula, A., and Dall'Osto, M.: On the annual variability of Antarctic aerosol size distributions at Halley Research Station, Atmos. Chem. Phys., 20, 4461–4476, 10.5194/acp-20-4461-2020, 2020.Lambert, F., Bigler, M., Steffensen, J. P., Hutterli, M., and Fischer, H.: Centennial mineral dust variability in high-resolution ice core data from Dome C, Antarctica, Clim. Past, 8, 609–623, 10.5194/cp-8-609-2012, 2012.
Lambert, G., Ardouin, B., and Sanak, J.: Atmospheric transport of trace
elements toward Antarctica, Tellus B, 42, 76–82, 1990.
Lancaster, N.: Flux of eolian sediment in the McMurdo Dry Valleys,
Antarctica: a preliminary assessment, Arct. Antarct. Alp. Res., 34, 318–323, 2002.
Lawrence, C. R. and Neff, J. C.: The contemporary physical and chemical
flux of aeolian dust: A synthesis of direct measurements of dust deposition,
Chem. Geol., 267, 46–63, 2009.Li, F., Ginoux, P., and Ramaswamy, V.: Distribution, transport, and
deposition of mineral dust in the Southern Ocean and Antarctica:
Contribution of major sources, J. Geophys. Res., 113, D18217, 10.1029/2007jd009190, 2008.
Loureiro, A., Vasconcellos, M., and Pereira, E.: Trace element determination
in aerosols from the Antarctic Peninsula by neutron activation analysis,
J. Radioanal. Nucl. Ch., 159, 21–28, 1992.
Lowenthal, D. H., Chow, J. C., Mazzera, D. M., Watson, J. G., and Mosher, B.
W.: Aerosol vanadium at McMurdo Station, Antarctica:: implications for Dye
3, Greenland, Atmos. Environ., 34, 677–679, 2000.
Lynch, H., Crosbie, K., Fagan, W., and Naveen, R.: Spatial patterns of tour
ship traffic in the Antarctic Peninsula region, Antarct. Sci., 22,
123–130, 2010.
Maenhaut, W., Zoller, W. H., Duce, R. A., and Hoffman, G. L.: Concentration
and size distribution of particulate trace elements in the south polar
atmosphere, J. Geophys. Res.-Ocean., 84, 2421–2431, 1979.Mahowald, N. M., Hamilton, D. S., Mackey, K. R., Moore, J. K., Baker, A. R.,
Scanza, R. A., and Zhang, Y.: Aerosol trace metal leaching and impacts on
marine microorganisms, Nat. Commun., 9, 2614, 10.1038/s41467-018-04970-7, 2018.
Mamun, A. A., Cheng, I., Zhang, L., Dabek-Zlotorzynska, E., and Charland,
J.-P.: Overview of size distribution, concentration, and dry deposition of
airborne particulate elements measured worldwide, Environ. Rev., 28,
77–88, 2020.
Marsay, C. M., Kadko, D., Landing, W. M., Morton, P. L., Summers, B. A., and
Buck, C. S.: Concentrations, provenance and flux of aerosol trace elements
during US GEOTRACES Western Arctic cruise GN01, Chem. Geol., 502, 1–14,
2018.Mazzera, D. M., Lowenthal, D. H., Chow, J. C., Watson, J. G., and Grub\ĭsíc, V.: PM10 measurements at McMurdo station, Antarctica,
Atmos. Environ., 35, 1891–1902, 2001.
McConnell, J. R., Aristarain, A. J., Banta, J. R., Edwards, P. R., and
Simões, J. C.: 20th-Century doubling in dust archived in an Antarctic
Peninsula ice core parallels climate change and desertification in South
America, P. Natl. Acad. Sci. USA, 104, 5743–5748, 2007.McConnell, J. R., Maselli, O. J., Sigl, M., Vallelonga, P., Neumann, T.,
Anschütz, H., Bales, R. C., Curran, M. A. J., Das, S. B., Edwards, R.,
Kipfstuhl, S., Layman, L., and Thomas, E. R.: Antarctic-wide array of
high-resolution ice core records reveals pervasive lead pollution began in
1889 and persists today, Sci. Rep.-UK, 4, 5848, 10.1038/srep05848,
2014.
Measures, C. and Vink, S.: On the use of dissolved aluminum in surface
waters to estimate dust deposition to the ocean, Glob. Biogeochem.
Cy., 14, 317–327, 2000.Menzel Barraqueta, J.-L., Klar, J. K., Gledhill, M., Schlosser, C., Shelley, R., Planquette, H. F., Wenzel, B., Sarthou, G., and Achterberg, E. P.: Atmospheric deposition fluxes over the Atlantic Ocean: a GEOTRACES case study, Biogeosciences, 16, 1525–1542, 10.5194/bg-16-1525-2019, 2019.
Millero, F. J.: Chemical oceanography, CRC Press, Boca Raton, FL, 2016.
Mishra, V. K., Kim, K.-H., Hong, S., and Lee, K.: Aerosol composition and
its sources at the King Sejong Station, Antarctic peninsula, Atmos.
Environ., 38, 4069–4084, 2004.Moore, C. M., Mills, M. M., Arrigo, K. R., Berman-Frank, I., Bopp, L., Boyd,
P. W., Galbraith, E. D., Geider, R. J., Guieu, C., Jaccard, S. L., Jickells,
T. D., La Roche, J., Lenton, T. M., Mahowald, N. M., Marañón, E.,
Marinov, I., Moore, J. K., Nakatsuka, T., Oschlies, A., Saito, M. A.,
Thingstad, T. F., Tsuda, A., and Ulloa, O.: Processes and patterns of
oceanic nutrient limitation, Nat. Geosci., 6, 701–710,
10.1038/ngeo1765, 2013.
Mouri, H., Nagao, I., Okada, K., Koga, S., and Tanaka, H.: Elemental
compositions of individual aerosol particles collected over the Southern
Ocean: A case study, Atmos. Res., 43, 183–195, 1997.
Orr, A., Marshall, G. J., Hunt, J. C., Sommeria, J., Wang, C.-G., Van
Lipzig, N. P., Cresswell, D., and King, J. C.: Characteristics of summer
airflow over the Antarctic Peninsula in response to recent strengthening of
westerly circumpolar winds, J. Atmos. Sci., 65, 1396–1413, 2008.Otero, X. L., De La Peña-Lastra, S., Pérez-Alberti, A., Ferreira, T.
O., and Huerta-Diaz, M. A.: Seabird colonies as important global drivers in
the nitrogen and phosphorus cycles, Nat. Commun., 9, 246,
10.1038/s41467-017-02446-8, 2018.
Pacyna, J. M. and Pacyna, E. G.: An assessment of global and regional
emissions of trace metals to the atmosphere from anthropogenic sources
worldwide, Environ. Rev., 9, 269–298, 2001.
Pilinis, C., Pandis, S. N., and Seinfeld, J. H.: Sensitivity of direct
climate forcing by atmospheric aerosols to aerosol size and composition,
J. Geophys. Res.-Atmos., 100, 18739–18754, 1995.
Potenza, M., Albani, S., Delmonte, B., Villa, S., Sanvito, T., Paroli, B.,
Pullia, A., Baccolo, G., Mahowald, N., and Maggi, V.: Shape and size
constraints on dust optical properties from the Dome C ice core, Antarctica,
Sci. Rep.-UK, 6, 1–9, 2016.Préndez, M., Wachter, J., Vega, C., Flocchini, R. G., Wakayabashi, P.,
and Morales, J. R.: PM2.5 aerosols collected in the Antarctic Peninsula with
a solar powered sampler during austral summer periods, Atmos.
Environ., 43, 5575–5578, 10.1016/j.atmosenv.2009.07.030, 2009.
Prietzel, J., Prater, I., Hurtarte, L. C. C., Hrbáček, F., Klysubun,
W., and Mueller, C. W.: Site conditions and vegetation determine phosphorus
and sulfur speciation in soils of Antarctica, Geochim. Cosmochim.
Ac., 246, 339–362, 2019.Prospero, J., Barrett, K., Church, T., Dentener, F., Duce, R., Galloway, J.,
Levy, H., Moody, J., and Quinn, P.: Atmospheric deposition of nutrients to the North Atlantic Basin, Biogeochemistry, 35, 27–73, 10.1007/BF02179824, 1996.
Prospero, J. M.: Mineral aerosol transport to the Pacific Ocean, Chem.
Oceanogr., 10, 188–218, 1989.
Quinn, T. and Ondov, J.: Influence of temporal changes in relative humidity
on dry deposition velocities and fluxes of aerosol particles bearing trace
elements, Atmos. Environ., 32, 3467–3479, 1998.
Rolph, G., Stein, A., and Stunder, B.: Real-time environmental applications
and display sYstem: READY, Environ. Model. Softw., 95, 210–228, 2017.
Saltzman, E. S.: Marine aerosols, Geoph. Monograph Series, 187, 17–35,
2009.
Santos, I. R., Silva-Filho, E. V., Schaefer, C. E., Albuquerque-Filho, M.
R., and Campos, L. S.: Heavy metal contamination in coastal sediments and
soils near the Brazilian Antarctic Station, King George Island, Mar.
Pollut. Bull., 50, 185–194, 2005.
Shelley, R. U., Morton, P. L., and Landing, W. M.: Elemental ratios and
enrichment factors in aerosols from the US-GEOTRACES North Atlantic
transects, Deep-Sea Res. Pt. II, 116, 262–272, 2015.
Shelley, R. U., Roca-Martí, M., Castrillejo, M., Sanial, V.,
Masqué, P., Landing, W. M., van Beek, P., Planquette, H., and Sarthou,
G.: Quantification of trace element atmospheric deposition fluxes to the
Atlantic Ocean (>40 N; GEOVIDE, GEOTRACES GA01) during spring
2014, Deep-Sea Res. Pt. I, 119, 34–49, 2017.
Siefert, R. L., Johansen, A. M., and Hoffmann, M. R.: Chemical
characterization of ambient aerosol collected during the southwest monsoon
and intermonsoon seasons over the Arabian Sea: Labile-Fe (II) and other
trace metals, J. Geophys. Res.-Atmos., 104, 3511–3526, 1999.Suttie, E. D. and Wolff, E. W.: Seasonal input of heavy metals to Antarctic snow, Tellus B, 44, 351–357, 10.1034/j.1600-0889.1992.00012.x, 1992.
Taylor, S. R. and McLennan, S. M.: The geochemical evolution of the
continental crust, Rev. Geophys., 33, 241–265, 1995.
Trabelsi, A., Masmoudi, M., Quisefit, J., and Alfaro, S.: Compositional
variability of the aerosols collected on Kerkennah Islands (central
Tunisia), Atmos. Res., 169, 292–300, 2016.
Tuncel, G., Aras, N. K., and Zoller, W. H.: Temporal variations and sources
of elements in the South Pole atmosphere: 1. Nonenriched and moderately
enriched elements, J. Geophys. Res.-Atmos., 94, 13025–13038, 1989.
Turner, J., Barrand, N. E., Bracegirdle, T. J., Convey, P., Hodgson, D. A.,
Jarvis, M., Jenkins, A., Marshall, G., Meredith, M. P., and Roscoe, H.:
Antarctic climate change and the environment: an update, Polar Rec., 50,
237–259, 2014.Van Lipzig, N., King, J., Lachlan-Cope, T., and Van den Broeke, M.:
Precipitation, sublimation, and snow drift in the Antarctic Peninsula region
from a regional atmospheric model, J. Geophys. Res.-Atmos., 109, D24106, 10.1029/2004JD004701, 2004.
Vaughan, D. G., Marshall, G. J., Connolley, W. M., Parkinson, C., Mulvaney,
R., Hodgson, D. A., King, J. C., Pudsey, C. J., and Turner, J.: Recent rapid
regional climate warming on the Antarctic Peninsula, Clim. Change, 60,
243–274, 2003.
Viana, M., Amato, F., Alastuey, A. s., Querol, X., Moreno, T., García Dos Santos, S. l., Herce, M. D., and Fernández-Patier, R.: Chemical tracers of particulate emissions from commercial shipping, Environ. Sci. Technol., 43, 7472–7477, 2009.
Viana, M., Hammingh, P., Colette, A., Querol, X., Degraeuwe, B., de Vlieger,
I., and Van Aardenne, J.: Impact of maritime transport emissions on coastal
air quality in Europe, Atmos. Environ., 90, 96–105, 2014.Virkkula, A., Teinilä, K., Hillamo, R., Kerminen, V. M., Saarikoski, S.,
Aurela, M., Koponen, I. K., and Kulmala, M.: Chemical size distributions of
boundary layer aerosol over the Atlantic Ocean and at an Antarctic site,
J. Geophys. Res.-Atmos., 111, D05306, 10.1029/2004JD004958, 2006.Wagener, T., Guieu, C., Losno, R., Bonnet, S., and Mahowald, N.: Revisiting
atmospheric dust export to the Southern Hemisphere ocean: Biogeochemical
implications, Glob. Biogeochem. Cy., 22, GB2006,
10.1029/2007gb002984, 2008.Warneck, P.: Chapter 7 The Atmospheric Aerosol, in: International
Geophysics, edited by: Warneck, P., Academic Press, Cambridge, MA, 278–373, 10.1016/S0074-6142(08)60634-8, 1988.
Weinzierl, B., Ansmann, A., Prospero, J., Althausen, D., Benker, N., Chouza,
F., Dollner, M., Farrell, D., Fomba, W., and Freudenthaler, V.: The Saharan
aerosol long-range transport and aerosol–cloud-interaction experiment:
overview and selected highlights, B. Am. Meteorol. Soc., 98, 1427–1451, 2017.
Weller, R., Wöltjen, J., Piel, C., Resenberg, R., Wagenbach, D.,
König-Langlo, G., and Kriews, M.: Seasonal variability of crustal and
marine trace elements in the aerosol at Neumayer station, Antarctica, Tellus
B, 60, 742–752, 2008.
Williams, R. M.: A model for the dry deposition of particles to natural
water surfaces, Atmos. Environ., 16, 1933–1938, 1982.
Winton, V., Dunbar, G., Bertler, N., Millet, M. A., Delmonte, B., Atkins,
C., Chewings, J., and Andersson, P.: The contribution of aeolian sand and
dust to iron fertilization of phytoplankton blooms in southwestern Ross Sea,
Antarctica, Glob. Biogeochem. Cy., 28, 423–436, 2014.
Winton, V., Edwards, R., Delmonte, B., Ellis, A., Andersson, P., Bowie, A.,
Bertler, N., Neff, P., and Tuohy, A.: Multiple sources of soluble
atmospheric iron to Antarctic waters, Glob. Biogeochem. Cy., 30,
421–437, 2016.Winton, V. H. L., Bowie, A. R., Edwards, R., Keywood, M., Townsend, A. T.,
van der Merwe, P., and Bollhöfer, A.: Fractional iron solubility of
atmospheric iron inputs to the Southern Ocean, Mar. Chem., 177, 20–32,
10.1016/j.marchem.2015.06.006, 2015.
Wu, J. and Boyle, E. A.: Lead in the western North Atlantic Ocean:
completed response to leaded gasoline phaseout, Geochim. Cosmochim.
Ac., 61, 3279–3283, 1997.Xu, G. and Gao, Y.: Atmospheric trace elements in aerosols observed over
the Southern Ocean and coastal East Antarctica, Polar Res., 33, 23973,
10.3402/polar.v33.23973, 2014.
Xu, G., Gao, Y., Lin, Q., Li, W., and Chen, L.: Characteristics of
water-soluble inorganic and organic ions in aerosols over the Southern Ocean
and coastal East Antarctica during austral summer, J. Geophys.
Res.-Atmos., 118, 13303–13318, 2013.
Zhao, R., Han, B., Lu, B., Zhang, N., Zhu, L., and Bai, Z.: Element
composition and source apportionment of atmospheric aerosols over the China
Sea, Atmos. Pollut. Res., 6, 191–201, 2015.
Zhao, Y. and Gao, Y.: Mass size distributions of water-soluble inorganic
and organic ions in size-segregated aerosols over metropolitan Newark in the
US east coast, Atmos. Environ., 42, 4063–4078, 2008.Zhu, C., Kawamura, K., and Kunwar, B.: Effect of biomass burning over the western North Pacific Rim: wintertime maxima of anhydrosugars in ambient aerosols from Okinawa, Atmos. Chem. Phys., 15, 1959–1973, 10.5194/acp-15-1959-2015, 2015.
Zhu, R., Kong, D., Sun, L., Geng, J., Wang, X., and Glindemann, D.:
Tropospheric phosphine and its sources in coastal Antarctica, Environ.
Scie. Technol., 40, 7656–7661, 2006.
Zoller, W. H., Gladney, E., and Duce, R. A.: Atmospheric concentrations and
sources of trace metals at the South Pole, Science, 183, 198–200, 1974.