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concentrations of ice-nucleating particles (NINP) in the Arctic
were derived from ground-based filter samples. Examined samples had been
collected in Alert (Nunavut, northern Canadian ...archipelago on Ellesmere
Island), Utqiaġvik, formerly known as Barrow (Alaska), Ny-Ålesund
(Svalbard), and at the Villum Research Station (VRS; northern Greenland). For
the former two stations, examined filters span a full yearly cycle. For VRS,
10 weekly samples, mostly from different months of one year, were included.
Samples from Ny-Ålesund were collected during the months from March until
September of one year. At all four stations, highest concentrations were
found in the summer months from roughly June to September. For those stations
with sufficient data coverage, an annual cycle can be seen. The spectra of
NINP observed at the highest temperatures, i.e., those obtained
for summer months, showed the presence of INPs that nucleate ice up to
−5 ∘C. Although the nature of these highly ice-active INPs could
not be determined in this study, it often has been described in the
literature that ice activity observed at such high temperatures originates
from the presence of ice-active material of biogenic origin. Spectra observed
at the lowest temperatures, i.e., those derived for winter months, were on
the lower end of the respective values from the literature on Arctic INPs or
INPs from midlatitude continental sites, to which a comparison is presented
herein. An analysis concerning the origin of INPs that were ice active at
high temperatures was carried out using back trajectories and satellite
information. Both terrestrial locations in the Arctic and the adjacent sea
were found to be possible source areas for highly active INPs.
Recently, the increasing interest in the understanding of global climatic changes and on natural processes related to climate yielded the development and improvement of new analytical methods for the ...analysis of environmental samples. The determination of trace chemical species is a useful tool in paleoclimatology, and the techniques for the analysis of ice cores have evolved during the past few years from laborious measurements on discrete samples to continuous techniques allowing higher temporal resolution, higher sensitivity and, above all, higher throughput. Two fast ion chromatographic (FIC) methods are presented. The first method was able to measure Cl–, NO3 – and SO4 2– in a melter-based continuous flow system separating the three analytes in just 1 min. The second method (called Ultra-FIC) was able to perform a single chromatographic analysis in just 30 s and the resulting sampling resolution was 1.0 cm with a typical melting rate of 4.0 cm min–1. Both methods combine the accuracy, precision, and low detection limits of ion chromatography with the enhanced speed and high depth resolution of continuous melting systems. Both methods have been tested and validated with the analysis of several hundred meters of different ice cores. In particular, the Ultra-FIC method was used to reconstruct the high-resolution SO4 2– profile of the last 10 000 years for the EDML ice core, allowing the counting of the annual layers, which represents a key point in dating these kind of natural archives.
•Combustion of woody biomass in commercial stoves.•Chemical-physical characterization of UFPs (diameter <100nm).•Genotoxicological evaluation in A549cell line.•Correlation between with UFP ...characteristics, combustion conditions and toxicity.
In this paper, results on the potential toxicity of ultrafine particles (UFPs d<100nm) emitted by the combustion of logwood and pellet (hardwood and softwood) are reported. The data were collected during the TOBICUP (TOxicity of BIomass COmbustion generated Ultrafine Particles) project, carried out by a team composed of interdisciplinary research groups. The genotoxic evaluation was performed on A549 cells (human lung carcinomacells) using UFPs whose chemical composition was assessed by a suite of analytical techniques. Comet assay and γ-H2AX evaluation show a significant DNA damage after 24h treatment. The interpretation of the results is based on the correlation among toxicological results, chemical-physical properties of UFPs, and the type and efficiency conditions in residential pellet or logwood stoves.
In this study, we present atmospheric ice-nucleating particle (INP)
concentrations from the Gruvebadet (GVB) observatory in Ny-Ålesund
(Svalbard). All aerosol particle sampling activities were ...conducted in April–August 2018. Ambient INP concentrations (nINP) were measured for aerosol
particles collected on filter samples by means of two offline instruments:
the Dynamic Filter Processing Chamber (DFPC) and the West Texas Cryogenic
Refrigerator Applied to Freezing Test system (WT-CRAFT) to assess
condensation and immersion freezing, respectively. DFPC measured nINPs for a
set of filters collected through two size-segregated inlets: one for
transmitting particulate matter of less than 1 µm (PM1), the
other for particles with an aerodynamic diameter of less than 10 µm
aerodynamic diameter (PM10). Overall, nINPPM10 measured by DFPC at
a water saturation ratio of 1.02 ranged from 3 to 185 m−3 at
temperatures (Ts) of −15 to −22 ∘C. On average, the super-micrometer INP (nINPPM10-nINPPM1) accounted for
approximately 20 %–30 % of nINPPM10 in spring, increasing in summer to
45 % at −22 ∘C and 65 % at −15 ∘C. This increase in super-micrometer INP fraction towards summer suggests that super-micrometer
aerosol particles play an important role as the source of INPs in the
Arctic. For the same T range, WT-CRAFT measured 1 to 199 m−3. Although
the two nINP datasets were in general agreement, a notable nINP offset was
observed, particularly at −15 ∘C. Interestingly, the results of
both DFPC and WT-CRAFT measurements did not show a sharp increase in nINP
from spring to summer. While an increase was observed in a subset of our
data (WT-CRAFT, between −18 and −21 ∘C), the spring-to-summer
nINP enhancement ratios never exceeded a factor of 3. More evident seasonal variability was found, however, in our activated fraction (AF) data, calculated by scaling the measured nINP to the total aerosol particle
concentration. In 2018, AF increased from spring to summer. This seasonal AF
trend corresponds to the overall decrease in aerosol concentration towards
summer and a concomitant increase in the contribution of super-micrometer particles. Indeed, the AF of coarse particles resulted markedly higher than
that of sub-micrometer ones (2 orders of magnitude). Analysis of low-traveling back-trajectories and meteorological conditions at GVB matched to our INP data suggests that the summertime INP population is
influenced by both terrestrial (snow-free land) and marine sources. Our
spatiotemporal analyses of satellite-retrieved chlorophyll a, as well as spatial source attribution, indicate that the maritime INPs at GVB may come
from the seawaters surrounding the Svalbard archipelago and/or in proximity
to Greenland and Iceland during the observation period. Nevertheless,
further analyses, performed on larger datasets, would be necessary to reach
firmer and more general conclusions.
Particulate matter with aerodynamic diameters lower than 10 µm, (PM10) aerosol samples were collected during summer 2013 within the framework of the Chemistry and Aerosol Mediterranean ...Experiment (ChArMEx) at two sites located north (Capo Granitola) and south (Lampedusa Island), respectively, of the main Mediterranean shipping route in the Straight of Sicily. The PM10 samples were collected with 12 h time resolutions at both sites. Selected metals, main anions, cations and elemental and organic carbon were determined. The evolution of soluble V and Ni concentrations (typical markers of heavy fuel oil combustion) was related to meteorology and ship traffic intensity in the Straight of Sicily, using a high-resolution regional model for calculation of back trajectories. Elevated concentration of V and Ni at Capo Granitola and Lampedusa are found to correspond with air masses from the Straight of Sicily and coincidences between trajectories and positions of large ships; the vertical structure of the planetary boundary layer also appears to play a role, with high V values associated with strong inversions and a stable boundary layer. The V concentration was generally lower at Lampedusa than at Capo Granitola V, where it reached a peak value of 40 ng m−3. Concentrations of rare earth elements (REEs), La and Ce in particular, were used to identify possible contributions from refineries, whose emissions are also characterized by elevated V and Ni amounts; refinery emissions are expected to display high La ∕ Ce and La ∕ V ratios due to the use of La in the fluid catalytic converter systems. In general, low La ∕ Ce and La ∕ V ratios were observed in the PM samples. The combination of the analyses based on chemical markers, air mass trajectories and ship routes allows us to unambiguously identify the large role of the ship source in the Straight of Sicily. Based on the sampled aerosols, ratios of the main aerosol species arising from ship emission with respect to V were estimated with the aim of deriving a lower limit for the total ship contribution to PM10. The estimated minimum ship emission contributions to PM10 were 2.0 µg m−3 at Lampedusa and 3.0 µg m−3 at Capo Granitola, corresponding with 11 and 8.6 % of PM10, respectively.
We report on the existence and nature of Holocene solar and climatic variations on centennial to millennial timescales. We introduce a new solar activity proxy, based on nitrate (NO3−) concentration ...from the Talos Dome ice core, East Antarctica. We also use a new algorithm for computing multiple-cross wavelet spectra in time–frequency space that is generalized for multiple time series (beyond two). Our results provide a new interpretive framework for relating Holocene solar activity variations on centennial to millennial timescales to co-varying climate proxies drawn from a widespread area around the globe. Climatic proxies used represent variation in the North Atlantic Ocean, Western Pacific Warm Pool, Southern Ocean and the East Asian monsoon regions. Our wavelet analysis identifies fundamental solar modes at 2300-yr (Hallstattzeit), 1000-yr (Eddy), and 500-yr (unnamed) periodicities, leaves open the possibility that the 1500–1800-yrcycle may either be fundamental or derived, and identifies intermediary derived cycles at 700-yr and 300-yr that may mark rectified responses of the Atlantic thermohaline circulation to external solar modulation and pacing. Dating uncertainties suggest that the 1500-yr and 1800-yrcycles described in the literature may represent either the same or two separate cycles, but in either case, and irrespective too of whether it is a fundamental or derived mode in the sense of Dima and Lohmann (2009), the 1500–1800-yr periodicity is widely represented in a large number of paleoclimate proxy records. It is obviously premature to reject possible links between changing solar activity at these multiple scales and the variations that are commonly observed in paleoclimatic records.
Understanding aerosol–cloud–climate interactions in the Arctic is key to predicting the climate in this rapidly changing region. Whilst many studies have focused on submicrometer aerosol (diameter ...less than 1 µm), relatively little is known about the supermicrometer aerosol (diameter above 1 µm). Here, we present a cluster analysis of multiyear (2015–2019) aerodynamic volume size distributions, with diameter ranging from 0.5 to 20 µm, measured continuously at the Gruvebadet Observatory in the Svalbard archipelago. Together with aerosol chemical composition data from several online and offline measurements, we apportioned the occurrence of the coarse-mode aerosols during the study period (mainly from March to October) to anthropogenic (two sources, 27 %) and natural (three sources, 73 %) origins. Specifically, two clusters are related to Arctic haze with high levels of black carbon, sulfate and accumulation mode (0.1–1 µm) aerosol. The first cluster (9 %) is attributed to ammonium sulfate-rich Arctic haze particles, whereas the second one (18 %) is attributed to larger-mode aerosol mixed with sea salt. The three natural aerosol clusters were open-ocean sea spray aerosol (34 %), mineral dust (7 %) and an unidentified source of sea spray-related aerosol (32 %). The results suggest that sea-spray-related aerosol in polar regions may be more complex than previously thought due to short- and long-distance origins and mixtures with Arctic haze, biogenic and likely blowing snow aerosols. Studying supermicrometer natural aerosol in the Arctic is imperative for understanding the impacts of changing natural processes on Arctic aerosol.
A prolonged and exceptionally intense air mass advection event transporting biomass burning aerosols generated in Alaska affected Ny-Ålesund in the mid of July 2015. This paper reports the ...morphochemical characteristics and mixing state of individual aerosol particles collected during the event. To this aim aerosol samples were collected on nucleopore polycarbonate membrane filters using a DEKATI 12-stage low volume impactor and analyzed by scanning electron microscopy (SEM) techniques. Results of SEM investigations depict a complex aerosol characterized by an external mixing between a main part of carbonaceous organic particles (tar balls and organic particles), lower ammonium sulfate and minor potassium chloride and mineral dust amounts. The carbonaceous particles are spherical to slightly elongated and the organic particles show an internal mixing of low density organics and/or ammonium sulfate upon denser nuclei. Most particles are in the accumulation mode size range although the size and the morphology of the chloride and the sulfate salts evidence the growth of these species both in the air and upon the sampling membranes. Individual particle analyses were complemented by aerosol size distribution (Aerodynamic Particle Sizer, Scanning Mobility Particle Sizer) and optical (Particle Soot Absorption Photometer, nephelometer) measurements at ground level in order to retrieve the optical and radiative properties of the aerosol in the atmosphere and to predict the fate and behaviour of particles upon deposition at ground level. Individual particle analyses were also compared with bulk chemical analyses on daily sampling filters and back-trajectory analyses of the air mass movement in order to enucleate distinct sources of the aerosol during the long range transport.
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•Brown carbon (organic, tar ball) and ammonium sulfate particles dominate.•Black carbon is not directly observed in the samples.•Its presence in the samples is suggested by the absorption Ångström exponent values.•Little particle aging is documented despite the prolonged long range transport.•Particles tend to persist in the lower troposphere for a long time before deposition.
Boreal fires have increased during the last years and are projected to become more intense and frequent as a consequence of climate change. Wildfires produce a wide range of effects on the Arctic ...climate and ecosystem, and understanding these effects is crucial for predicting the future evolution of the Arctic region. This study focuses on the impact of the long-range transport of biomass-burning aerosol into the atmosphere and the corresponding radiative perturbation in the shortwave frequency range. As a case study, we investigate an intense biomass-burning (BB) event which took place in summer 2017 in Canada and subsequent northeastward transport of gases and particles in the plume leading to exceptionally high values (0.86) of Aerosol Optical Depth (AOD) at 500 nm measured in northwestern Greenland on 21 August 2017. This work characterizes the BB plume measured at the Thule High Arctic Atmospheric Observatory (THAAO; 76.53∘N, 68.74∘W) in August 2017 by assessing the associated shortwave aerosol direct radiative impact over the THAAO and extending this evaluation over the broader region (60∘N–80∘N, 110∘W–0∘E). The radiative transfer simulations with MODTRAN6.0 estimated an aerosol heating rate of up to 0.5 K/day in the upper aerosol layer (8–12 km). The direct aerosol radiative effect (ARE) vertical profile shows a maximum negative value of −45.4 Wm−2 for a 78∘ solar zenith angle above THAAO at 3 km altitude. A cumulative surface ARE of −127.5 TW is estimated to have occurred on 21 August 2017 over a portion (∼3.1×106 km2) of the considered domain (60∘N–80∘N, 110∘W–0∘E). ARE regional mean daily values over the same portion of the domain vary between −65 and −25 Wm−2. Although this is a limited temporal event, this effect can have significant influence on the Arctic radiative budget, especially in the anticipated scenario of increasing wildfires.
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