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Sökning: WFRF:(Becagli Silvia)

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1.
  • Dall'Osto, Manuel, et al. (författare)
  • Simultaneous measurements of aerosol size distributions at three sites in the European high Arctic
  • 2019
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:11, s. 7377-7395
  • Tidskriftsartikel (refereegranskat)abstract
    • Aerosols are an integral part of the Arctic climate system due to their direct interaction with radiation and indirect interaction through cloud formation. Understanding aerosol size distributions and their dynamics is crucial for the ability to predict these climate relevant effects. When of favourable size and composition, both long-rangetransported - and locally formed particles - may serve as cloud condensation nuclei (CCN). Small changes of composition or size may have a large impact on the low CCN concentrations currently characteristic of the Arctic environment. We present a cluster analysis of particle size distributions (PSDs; size range 8-500 nm) simultaneously collected from three high Arctic sites during a 3-year period (20132015). Two sites are located in the Svalbard archipelago: Zeppelin research station (ZEP; 474 m above ground) and the nearby Gruvebadet Observatory (GRU; about 2 km distance from Zeppelin, 67 m above ground). The third site (Villum Research Station at Station Nord, VRS; 30 m above ground) is 600 km west-northwest of Zeppelin, at the tip of northeastern Greenland. The GRU site is included in an inter-site comparison for the first time. K-means cluster analysis pro- vided eight specific aerosol categories, further combined into broad PSD classes with similar characteristics, namely pristine low concentrations (12 %-14 % occurrence), new particle formation (16 %-32 %), Aitken (21 %-35 %) and accumulation (20 %-50 %). Confined for longer time periods by consolidated pack sea ice regions, the Greenland site GRU shows PSDs with lower ultrafine-mode aerosol concentrations during summer but higher accumulation-mode aerosol concentrations during winter, relative to the Svalbard sites. By association with chemical composition and cloud condensation nuclei properties, further conclusions can be derived. Three distinct types of accumulation-mode aerosol are observed during winter months. These are associated with sea spray (largest detectable sizes, > 400 nm), Arctic haze (main mode at 150 nm) and aged accumulation-mode (main mode at 220 nm) aerosols. In contrast, locally produced particles, most likely of marine biogenic origin, exhibit size distributions dominated by the nucleation and Aitken mode during summer months. The obtained data and analysis point towards future studies, including apportioning the relative contribution of primary and secondary aerosol formation processes and elucidating anthropogenic aerosol dynamics and transport and removal processes across the Greenland Sea. In order to address important research questions in the Arctic on scales beyond a singular station or measurement events, it is imperative to continue strengthening international scientific cooperation.
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3.
  • Fischer, Hubertus, et al. (författare)
  • Reconstruction of millennial changes in dust emission, transport and regional sea ice coverage using the deep EPICA ice cores from the Atlantic and Indian Ocean sector of Antarctica
  • 2007
  • Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 0012-821X. ; 260, s. 340-354
  • Tidskriftsartikel (refereegranskat)abstract
    • Continuous sea salt and mineral dust aerosol records have been studied on the two EPICA (European Project for Ice Coring inAntarctica) deep ice cores. The joint use of these records from opposite sides of the East Antarctic plateau allows for an estimate ofchanges in dust transport and emission intensity as well as for the identification of regional differences in the sea salt aerosolsource. The mineral dust flux records at both sites show a strong coherency over the last 150 kyr related to dust emission changes inthe glacial Patagonian dust source with three times higher dust fluxes in the Atlantic compared to the Indian Ocean sector of theSouthern Ocean (SO). Using a simple conceptual transport model this indicates that transport can explain only 40% of theatmospheric dust concentration changes in Antarctica, while factor 5–10 changes occurred. Accordingly, the main cause for the strong glacial dust flux changes in Antarctica must lie in environmental changes in Patagonia. Dust emissions, hence environmentalconditions in Patagonia, were very similar during the last two glacials and interglacials, respectively, despite 2–4 °C warmertemperatures recorded in Antarctica during the penultimate interglacial than today. 2–3 times higher sea salt fluxes found in bothice cores in the glacial compared to the Holocene are difficult to reconcile with a largely unchanged transport intensity and thedistant open ocean source. The substantial glacial enhancements in sea salt aerosol fluxes can be readily explained assuming sea iceformation as the main sea salt aerosol source with a significantly larger expansion of (summer) sea ice in the Weddell Sea than inthe Indian Ocean sector. During the penultimate interglacial, our sea salt records point to a 50% reduction of winter sea icecoverage compared to the Holocene both in the Indian and Atlantic Ocean sector of the SO. However, from 20 to 80 ka beforepresent sea salt fluxes show only very subdued millennial changes despite pronounced temperature fluctuations, likely due to thelarge distance of the sea ice salt source to our drill sites.
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4.
  • Jang, Sehyun, et al. (författare)
  • Large seasonal and interannual variations of biogenic sulfur compounds in the Arctic atmosphere (Svalbard; 78.9° N, 11.9° E)
  • 2021
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 21:12, s. 9761-9777
  • Tidskriftsartikel (refereegranskat)abstract
    • Seasonal to interannual variations in the concentrations of sulfur aerosols (< 2.5 µm in diameter; non sea-salt sulfate: NSS-SO2−4; anthropogenic sulfate: Anth-SO2−4; biogenic sulfate: Bio-SO2−4; methanesulfonic acid: MSA) in the Arctic atmosphere were investigated using measurements of the chemical composition of aerosols collected at Ny-Ålesund, Svalbard (78.9∘ N, 11.9∘ E) from 2015 to 2019. In all measurement years the concentration of NSS-SO2−4 was highest during the pre-bloom period and rapidly decreased towards summer. During the pre-bloom period we found a strong correlation between NSS-SO2−4 (sum of Anth-SO2−4 and Bio-SO2−4) and Anth-SO2−4. This was because more than 50 % of the NSS-SO2−4 measured during this period was Anth-SO2−4, which originated in northern Europe and was subsequently transported to the Arctic in Arctic haze. Unexpected increases in the concentration of Bio-SO2−4 aerosols (an oxidation product of dimethylsulfide: DMS) were occasionally found during the pre-bloom period. These probably originated in regions to the south (the North Atlantic Ocean and the Norwegian Sea) rather than in ocean areas in the proximity of Ny-Ålesund. Another oxidation product of DMS is MSA, and the ratio of MSA to Bio-SO2−4 is extensively used to estimate the total amount of DMS-derived aerosol particles in remote marine environments. The concentration of MSA during the pre-bloom period remained low, primarily because of the greater loss of MSA relative to Bio-SO2−4 and the suppression of condensation of gaseous MSA onto particles already present in air masses being transported northwards from distant ocean source regions (existing particles). In addition, the low light intensity during the pre-bloom period resulted in a low concentration of photochemically activated oxidant species including OH radicals and BrO; these conditions favored the oxidation pathway of DMS to Bio-SO2−4 rather than to MSA, which acted to lower the MSA concentration at Ny-Ålesund. The concentration of MSA peaked in May or June and was positively correlated with phytoplankton biomass in the Greenland and Barents seas around Svalbard. As a result, the mean ratio of MSA to the DMS-derived aerosols was low (0.09 ± 0.07) in the pre-bloom period but high (0.32 ± 0.15) in the bloom and post-bloom periods. There was large interannual variability in the ratio of MSA to Bio-SO2−4 (i.e., 0.24 ± 0.11 in 2017, 0.40 ± 0.14 in 2018, and 0.36 ± 0.14 in 2019) during the bloom and post-bloom periods. This was probably associated with changes in the chemical properties of existing particles, biological activities surrounding the observation site, and air mass transport patterns. Our results indicate that MSA is not a conservative tracer for predicting DMS-derived particles, and the contribution of MSA to the growth of newly formed particles may be much larger during the bloom and post-bloom periods than during the pre-bloom period.
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5.
  • Lupi, Angelo, et al. (författare)
  • Multi-seasonal ultrafine aerosol particle number concentration measurements at the Gruvebadet observatory, Ny-lesund, Svalbard Islands
  • 2016
  • Ingår i: Rendiconti lincei scienze fisiche e naturali. - : Springer Science and Business Media LLC. - 2037-4631. ; 27, s. 59-71
  • Tidskriftsartikel (refereegranskat)abstract
    • The object of this study was to investigate the different modal behavior of ultrafine aerosol particles collected at the Gruvebadet observatory located in Ny-lesund (Svalbard Islands, 78A degrees 55'N, 11A degrees 56'E). Aerosol particle size distribution was measured in the size range from 10 to 470 nm typically from the beginning of spring to the beginning of fall during four (non-consecutive) years (2010, 2011, 2013 and 2014). The median concentration for the whole period taken into account was 214 particles cm(-3), oscillating between the median maximum in July with a concentration of 257 particles cm(-3) and a median minimum in April with 197 particles cm(-3). The median total number concentration did not present a well-defined seasonal behavior, as shown by contrast looking at the sub/modal number concentration, where distinct trends appeared in the predominant accumulation concentration recorded during April/May and the preponderant concentration of Aitken particles during the summer months. Lastly, the short side-by-side spring 2013 campaign performed at the Zeppelin observatory with a differential mobility particle sizer was characterized by an aerosol concentration mean steady difference between the two instruments of around 14 %, thereby supporting the reliability of the device located at Gruvebadet.
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6.
  • Park, Ki-Tae, et al. (författare)
  • Dimethyl Sulfide-Induced Increase in Cloud Condensation Nuclei in the Arctic Atmosphere
  • 2021
  • Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 35:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Oceanic dimethyl sulfide (DMS) emissions have been recognized as a biological regulator of climate by contributing to cloud formation. Despite decades of research, the climatic role of DMS remains ambiguous largely because of limited observational evidence for DMS-induced cloud condensation nuclei (CCN) enhancement. Here, we report concurrent measurement of DMS, physiochemical properties of aerosol particles, and CCN in the Arctic atmosphere during the phytoplankton bloom period of 2010. We encountered multiple episodes of new particle formation (NPF) and particle growth when DMS mixing ratios were both low and high. The growth of particles to sizes at which they can act as CCN accelerated in response to an increase in atmospheric DMS. Explicitly, the sequential increase in all relevant parameters (including the source rate of condensable vapor, the growth rate of particles, Aitken mode particles, hygroscopicity, and CCN) was pronounced at the DMS-derived NPF and particle growth events. This field study unequivocally demonstrates the previously unconfirmed roles of DMS in the growth of particles into climate-relevant size and eventual CCN activation.
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7.
  • Traversi, Rita, et al. (författare)
  • Sulfate spikes in the deep layers of EPICA-Dome C Ice Core: Evidence of glaciological artifacts
  • 2009
  • Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 43:23, s. 8737-8743
  • Tidskriftsartikel (refereegranskat)abstract
    • A detailed ionic component record was performed on EPICA Dome C ice core (East Antarctica) to a depth of 3190 m using Ion Chromatography and Fast Ion Chromatography (FIC). At depths greater than 2800 m, the sulfate profile shows intense, sharp spikes which are not expected due to the smoothing of sulfate peaks by diffusion processes. Moreover, these spikes show an "anomalous" chemical composition (e.g., unusually low acidity, high Mg2+ concentration and high Mg2+/Ca2+ ratio). These peaks and the surrounding layers also exhibit good Mg2+ vs SO42- and Cl- vs Na+ correlations through both glacial and interglacial periods. Furthermore, the high-resolution analysis of two horizontally contiguous ice sections showed that some fraction of the impurities are characterized by a heterogeneous distribution. Altogether, these results suggest the occurrence of long-term postdepositional processes involving a rearrangement of impurities via migration in the vein network, characterized by sulfuric acidity and leading to the formation of soluble particles of magnesium sulfate salts, along with ionic association of ions in the liquid films along boundaries. This evidence should be taken into consideration when inferring information on for rapid climatic and environmental changes from ice core chemical records at great depths. At Dome C, the depth threshold was found to be 2800 m.
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8.
  • Xavier, Carlton, et al. (författare)
  • Secondary aerosol formation in marine Arctic environments : a model measurement comparison at Ny-Ålesund
  • 2022
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 22:15, s. 10023-10043
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, we modeled the aerosol particle formation along air mass trajectories arriving at the remote Arctic research stations Gruvebadet (67 m a.s.l.) and Zeppelin (474 m a.s.l.), Ny-Ålesund, during May 2018. The aim of this study was to improve our understanding of processes governing secondary aerosol formation in remote Arctic marine environments. We run the Lagrangian chemistry transport model ADCHEM, along air mass trajectories generated with FLEXPART v10.4. The air masses arriving at Ny-Ålesund spent most of their time over the open ice-free ocean. In order to capture the secondary aerosol formation from the DMS emitted by phytoplankton from the ocean surface, we implemented a recently developed comprehensive DMS and halogen multi-phase oxidation chemistry scheme, coupled with the widely used Master Chemical Mechanism (MCM).The modeled median particle number size distributions are in close agreement with the observations in the marine-influenced boundary layer near-sea-surface Gruvebadet site. However, while the model reproduces the accumulation mode particle number concentrations at Zeppelin, it overestimates the Aitken mode particle number concentrations by a factor of ∼5.5. We attribute this to the deficiency of the model to capture the complex orographic effects on the boundary layer dynamics at Ny-Ålesund. However, the model reproduces the average vertical particle number concentration profiles within the boundary layer (0–600 m a.s.l.) above Gruvebadet, as measured with condensation particle counters (CPCs) on board an unmanned aircraft system (UAS).The model successfully reproduces the observed Hoppel minima, often seen in particle number size distributions at Ny-Ålesund. The model also supports the previous experimental findings that ion-mediated H2SO4–NH3 nucleation can explain the observed new particle formation in the marine Arctic boundary layer in the vicinity of Ny-Ålesund. Precursors resulting from gas- and aqueous-phase DMS chemistry contribute to the subsequent growth of the secondary aerosols. The growth of particles is primarily driven via H2SO4 condensation and formation of methane sulfonic acid (MSA) through the aqueous-phase ozonolysis of methane sulfinic acid (MSIA) in cloud and deliquescent droplets.
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