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A 20-year dataset of weekly precipitation observations in Ny-Ålesund, Svalbard, was analysed to assess atmospheric wet deposition of nitrogen. Mean annual total nitrogen deposition was 74 mg N/(m² yr) but exhibited large interannual variability and was dominated by highly episodic "strong" events, probably caused by rapid transport from European sources. The majority (90%) of precipitation samples were defined as "weak" (<2mgN/m²) and contributed an annual baseline of ∼17 mg N/(m² yr), whereas 10% of precipitation samples were defined as "strong" (>2mgN/m²) and additionally contributed up to 225 mg N/(m² yr). Nitrate deposition largely occurred in samples within the solid-precipitation season (16 September-2 June), and ammonium deposition occurred equally in both solid and liquid seasons. Trends of reactive nitrogen emissions from Europe are uncertain, and increasing cyclonic activity over the North Atlantic caused by a changing climate might lead to more strong deposition events in Svalbard. [ABSTRACT FROM AUTHOR]

The article focuses on a study which examined the chemistry of mercury (Hg) in the atmosphere and the formation of oxidized species, as well as the fate of mercury inside a sunlight-irradiated snow pack. Ny-Âlesund, Svalbard, Norway was the site chosen for this study. A Tekran 2537A analyzer was used to measure Gaseous Elemental Mercury (GEM) concentrations, while the chamber technique was used to measure Hg emission fluxes from the snow pack to the atmosphere. Results of the study showed that there were low Particulate Mercury (PM) and Reactive Gaseous Mercury (RGM) during the first Atmospheric Mercury Depletition Events (AMDEs). According to the study, apparent destruction rates can be attributed to advection of air masses already depleted in ozone.

Here we apply new analysis methods and approaches to existing long-term measurement series that provide additional insights into the atmospheric processes that control black carbon (BC) in the Arctic. Based on clustering size distribution data from Zeppelin Observatory for the years 2002–2010, observations classified as 'Polluted' were further investigated based on BC properties. The data were split into two subgroups, and while the microphysical and chemical fingerprints of the two subgroups are very similar, they show larger differences in BC concentration and correlation with the particle size distribution. Therefore, a source–receptor analysis was performed with HYSPLIT 10-days backward trajectories for both subsets. We demonstrate that within this 'Polluted' category, the airmasses that contributed to the largest BC signal at the Zeppelin station are not necessarily associated with traditional transport pathways from Eurasia. Instead, the strongest signal is from a region east of the Ural Mountains across the continent to the Kamchatka Peninsula. [ABSTRACT FROM AUTHOR]

The chemical composition of atmospheric particulate matter at Mt. Åreskutan, a mountaintop site in central Sweden, was analysed with a focus on its carbonaceous content. Filter samples taken during the Cloud and Aerosol Experiment at Åre (CAEsAR 2014) were analysed by means of a thermo-optical method and ion chromatography. Additionally, the particle light absorption and particle number size distribution measurements for the entire campaign were added to the analysis. Mean airborne concentrations of organic and elemental carbon during CAEsAR 2014 were OC = 0.85  0.80 g mand EC = 0.060.06 g m, respectively. Elemental to organic carbon ratios varied between EC/OC = 0.02 and 0.19. During the study a large wildfire occurred in Västmanland, Sweden, with the plume reaching our study site. This led to significant increases in OC and EC concentrations (OC = 3.04  0.03 g mand EC = 0.24  0.00 g m). The mean mass-specific absorption coefficient observed during the campaign was = 9.17.3 mg(at wavelength = 637 nm). In comparison to similarly remote European sites, Mt. Åreskutan experienced significantly lower carbonaceous aerosol loadings with a clear dominance of organic carbon. A mass closure study revealed a missing chemical mass fraction that likely originated from mineral dust. Potential regional source contributions of the carbonaceous aerosol were investigated using modelled air mass back trajectories. This source apportionment pointed to a correlation between high EC concentrations and air originating from continental Europe. Particles rich in organic carbon most often arrived from highly vegetated continental areas. However, marine regions were also a source of these aerosol particles. The source contributions derived during this study were compared to emission inventories of an Earth system model. This comparison highlighted a lack of OC and EC point-sources in the model’s emission inventory which could potentially lead to an underestimation of the carbonaceous aerosol reaching Mt. Åreskutan in the simulation of this Earth system model. [ABSTRACT FROM PUBLISHER]

The aim of this study was to explore particle size dependent properties by combining long-term observations of equivalent black carbon (eBC) and number size distributions to investigate their correlation as function of particle size. The work was conducted in two main parts. The first part consisted of a short laboratory experiment to compare observed total particle light absorption (σabs) with that observed according to particle size by using a combination of a Differential Mobility Analyzer (DMA) and a Particle Soot Absorption Photometer (PSAP). The laboratory study confirmed strong similarities between the observed and derived σabs. In the second part the statistical approach using correlation between the σabs and the dN of each bin of the number size distribution was tested on long-term data ranging from 2002 to 2010 observed at Zeppelin station, Ny-Ålesund Svalbard. The data was clustered according to the number size distribution and grouped in four major categories: Washout, Nucleation, Intermediate and Polluted. Each category presented different features with respect to the derived eBC mass distributions, the Intermediate category showed similarities to the few available Single Particle Soot Photometer (SP2) observations in the Arctic. Overall, the statistical distribution of eBC, according to particle size, presented a larger dynamical range in the location of the mode(s). To check for consistency, the eBC mass distributions were transformed into number based eBC size distribution and compared to the observed total number size distribution. Whereas the Washout, Nucleation and Intermediate categories presented plausible number distributions, the Polluted category displayed a mode at small sizes (about 50 nm) that was significantly exaggerated. [ABSTRACT FROM AUTHOR]

The size distribution, volatility and hygroscopicity of ambient aerosols and cloud residuals were measured with a differential mobility particle sizer (DMPS) and a volatility-hygroscopicity tandem differential mobility analyser (VHTDMA) coupled to a counterflow virtual impactor (CVI) inlet during the Cloud and Aerosol Experiment at Âre (CAEsAR) campaign at Mt. Âreskutan during summer 2014. The chemical composition of particulate matter (PM) and cloud water were analysed offline using thermo-optical OC/EC analysis and ion chromatography. The importance of aerosol particle size for cloud droplet activation and subsequent particle scavenging was clearly visible in the measured size distributions. Cloud residuals were shifted towards larger sizes compared to ambient aerosol, and the cloud events were followed by a size distribution dominated by smaller particles. Organics dominated both PM (62% organic mass fraction) and cloud water (63% organic mass fraction) composition. The volatility and hygroscopicity of the ambient aerosols were representative of homogeneous aged aerosol with contributions from biogenic secondary organics, with median volume fraction remaining (VFR) of 0.04-0.05, and median hygroscopicity parameter j of 0.16-0.24 for 100-300nm particles. The corresponding VFR and j for the cloud residuals were 0.03-0.04 and 0.18-0.20. The chemical composition, hygroscopicity and volatility measurements thus showed no major differences between the ambient aerosol particles and cloud residuals. The VFR and j values predicted based on the chemical composition measurements agreed well with the VHTDMA measurements, indicating the bulk chemical composition to be a reasonable approximation throughout the size distribution. There were indications, however, of some more subtle changes in time scales not achievable by the offline chemical analysis applied here. Further, online observations of aerosol and cloud residual chemical composition are therefore warranted. [ABSTRACT FROM AUTHOR]

While dry and rain deposition of nitrate (NO3-) and ammonium (NH4+) are regularly assessed, fog deposition is often overlooked. This work assesses summer fog events contribution to nitrogen deposition and availability for forest ecosystems. Rain and fog samples were collected at Mt Åreskutan, Sweden, during CAEsAR (Cloud and Aerosol Characterization Experiment), in 2014. NH4+ + NO3+ represent (31±25)% of total rain ion amount, and (31±42)% in fog. Based on ion concentrations and the nitrate stable isotope signatures δ(15N) and δ(18O), it was possible to detect the plume generated by the Västmanland forest fire; NOx emissions from oil rigs and Kola Peninsula; and the plume of Bardarbunga volcano, Iceland. Scavenging of ions by fog was more efficient than by rain. Rain NH4+ and NO3+ deposition was (26±36) µmolm-2 d-1 and (23±27) µmolm-2 d-1, respectively. Fog NH4+ and NO3- contributed (77±80)% to total wet deposition of these species. Upscaling rain deposition fluxes to 1 year gave an inorganic nitrogen deposition of (18±16) mmolm-2 a-1 ((252±224) mgm-2 a-1N equivalents), whereas fog deposition was estimated as (59±47) mmol m-2 a-1 ((826±658) mgm-2 a-1 N equivalents). Annual fog deposition was four times higher than previously reported for the area which only considered rain deposition. However, great uncertainty on the calculation of fog deposition need to be bear in mind. These findings suggest that fog should be considered in deposition estimates of inorganic nitrogen and major ions. If fog deposition is not accounted for, ion wet deposition may be greatly underestimated. Further sampling of wet and dry deposition is important for understanding the influence of nitrogen deposition on forest and vegetation development, as well as soil major ion loads. [ABSTRACT FROM AUTHOR]

Cloud Condensation Nuclei (CCN) concentration and aerosol size distributions in the Arctic were collected during the period 2007-2013 at the Zeppelin observatory (78.91° N, 11.89° E, 474 masl). Annual median CCN concentration at a supersaturation (SS) of 0.4% show the ranges of 45 ∼ 81 cm−3. The monthly median CCN number density varied between 17 cm−3 in October 2007 and 198 cm−3 in March, 2008. The CCN spectra parameters C (83 cm−3) and k (0.23) were derived. In addition, calculated annual median value of hygroscopicity parameter is 0.46 at SS of 0.4%. Particle number concentration of accumulation mode from aerosol size distribution measurements are well correlated with CCN concentration. The CCN to CN>10 nm (particle number concentration larger than 10nm in diameter) ratio shows a maximum during March and minimum during July. The springtime high CCN concentration is attributed to high load of accumulation mode aerosol transported from the mid-latitudes, known as Arctic Haze. CCN concentration remains high also during Arctic summer due to the source of new CCN through particle formation followed by consecutive aerosol growth. Lowest aerosol as well as CCN number densities were observed during Arctic autumn and early winter when aerosol formation in the Arctic and long-range transport into the Arctic are not effective. [ABSTRACT FROM AUTHOR]

Kerbside concentrations of NOx, black carbon (BC), total number of particles (diameter > 4 nm) and number size distribution (28–410 nm) were measured at a busy street canyon in Stockholm in 2006 and 2013. Over this period, there was an important change in the vehicle fleet due to a strong dieselisation process of light-duty vehicles and technological improvement of vehicle engines. This study assesses the impact of these changes on ambient concentrations and particle emission factors (EF). EF were calculated by using a novel approach which combines the NOx tracer method with positive matrix factorisation (PMF) applied to particle number size distributions. NOx concentrations remained rather constant between these two years, whereas a large decrease in particle concentrations was observed, being on average 60% for BC, 50% for total particle number, and 53% for particles in the range 28–100 nm. The PMF analysis yielded three factors that were identified as contributions from gasoline vehicles, diesel fleet, and urban background. This separation allowed the calculation of the average vehicle EF for each particle metric per fuel type. In general, gasoline EF were lower than diesel EF, and EF for 2013 were lower than the ones derived for 2006. The EF BC decreased 77% for both gasoline and diesel fleets, whereas the particle number EF reduction was higher for the gasoline (79%) than for the diesel (37%) fleet. Our EF are consistent with results from other on-road studies, which reinforces that the proposed methodology is suitable for EF determination and to assess the effectiveness of policies implemented to reduce vehicle exhaust emissions. However, our EF are much higher than EF simulated with traffic emission models (HBEFA and COPERT) that are based on dynamometer measurements, except for EF BC for diesel vehicles. This finding suggests that the EF from the two leading models in Europe should be revised for BC (gasoline vehicles) and particle number (all vehicles), since they are used to compile national inventories for the road transportation sector and also to assess their associated health effects. Using the calculated kerbside EF, we estimated that the traffic emissions were lower in 2013 compared to 2006 with a 61% reduction for BC (due to decreases in both gasoline and diesel emissions), and 34–45% for particle number (reduction only in gasoline emissions). Limitations of the application of these EF to other studies are also discussed. [ABSTRACT FROM AUTHOR]

A new, more physically based wet removal scheme for aerosols has been implemented in the Lagrangian particle dispersion model FLEXPART. It uses three-dimensional cloud water fields from the European Centre for Medium-Range Weather Forecasts (ECMWF) to determine cloud extent and distinguishes between in-cloud and below-cloud scavenging. The new in-cloud nucleation scavenging depends on cloud water phase (liquid, ice or mixed-phase), based on the aerosol's prescribed efficiency to serve as ice crystal nuclei and liquid water nuclei, respectively. The impaction scavenging scheme now parameterizes below-cloud removal as a function of aerosol particle size and precipitation type (snow or rain) and intensity. Sensitivity tests with the new scavenging scheme and comparisons with observational data were conducted for three distinct types of primary aerosols, which pose different challenges for modeling wet scavenging due to their differences in solubility, volatility and size distribution: (1) 137Cs released during the Fukushima nuclear accident attached mainly to highly soluble sulphate aerosol particles, (2) black carbon (BC) aerosol particles, and (3) mineral dust. Calculated e-folding lifetimes of accumulation mode aerosols for these three aerosol types were 11.7, 16.0, and 31.6 days respectively, when well mixed in the atmosphere. These are longer lifetimes than those obtained by the previous removal schem, and, for mineral dust in particular, primarily result from very slow in-cloud removal, which globally is the primary removal mechanism for these accumulation mode particles. Calculated e-folding lifetimes in FLEXPART also have a strong size dependence, with the longest lifetimes found for the accumulation-mode aerosols. For example, for dust particles emitted at the surface the lifetimes were 13.8 days for particles with 1 µm diameter and a few hours for 10 µm particles. A strong size dependence in below-cloud scavenging, combined with increased dry removal, is the primary reason for the shorter lifetimes of the larger particles. The most frequent removal is in-cloud scavenging (85% of all scavenging events) but it occurs primarily in the free troposphere, while below-cloud removal is more frequent below 1000m (52%of all events) and can be important for the initial fate of species emitted at the surface, such as those examined here. For assumed realistic in-cloud removal efficiencies, both BC and sulphate have a slight overestimation of observed atmospheric concentrations (a factor of 1.6 and 1.2 respectively). However, this overestimation is largest close to the sources and thus appears more related to overestimated emissions rather than underestimated removal. The new aerosol wet removal scheme of FLEXPART incorporates more realistic information about clouds and aerosol properties and it compares better with both observed lifetimes and concentration than the old scheme. [ABSTRACT FROM AUTHOR]

ABSTRACT Simultaneous measurements of aerosol black carbon (BC) in both fresh snow and in air on Svalbard are presented. From these, washout ratios for BC are calculated and compared to sparse previous measurements of this metric in the arctic. The current ratios are significantly higher than previously found measured values. We argue that the degree of snow riming within the accretion zone can explain most of this difference. Using an analytical model of the scavenging process, BC scavenging efficiencies are estimated to lie in the range 0.25-0.5, comparable to measured values. [ABSTRACT FROM AUTHOR]

BSTRACT The impact on snow pack albedo from local elemental carbon (EC) sources in Svalbard has been investigated for the winter of 2008. Highly elevated EC concentrations in the snow are observed around the settlements of Longyearbyen and Svea (locally >1000 ng g [ABSTRACT FROM AUTHOR]

Abstract: An international campaign involving six teams was organized in Ny-Ålesund, Svalbard, in order to understand better the origin of atmospheric mercury depletion events (AMDEs). Special emphasis was given to determining the source region of the observed events and the physical and chemical processes leading to AMDEs. Five AMDEs were recorded during a one-month field experiment (10 April–10 May, 2003). The different events presented various characteristics, especially in terms of mercury species formation, atmospheric particle variations and meteorological conditions. After careful examination of each event, we postulate that two were probably due to advection of already depleted air masses and three were a product of local or regional chemistry. The roles of different surfaces (frost flowers, snow, ice aerosol in clouds) involved in heterogeneous reactions leading to AMDEs are also discussed. We speculate that ice clouds may explain the particle variations observed during the three more local events. [Copyright &y& Elsevier]

Seasonal snow cover duration is the net result from many processes acting on snow fallen on the Earth's surface. Several of these processes feed back into the atmosphere-cryosphere system causing non-linear interactions. The timing of snow retreat is of essential importance, but the duration of snow cover has large spatiotemporal variabilities. However, from a large data set of observed snow depth changes in northern Finland, systematic similar evolutions are identified that allow for a considerable simplification and reduction of the complexity in snow depth changes. Here, a novel conceptual framework is designed based on dividing the season into two main periods (dark and bright period, based on solar irradiance), for which snow depth decrease is parameterized based on three variables, average temperature, incoming shortwave radiation, and light-absorbing particles (LAP) in the snow. The processes are simplified into two linear relations, and a new formulation for concentration enhancement of LAP, which is dependent on snow depth decrease, is given. The results show that the seasonal snow cover duration is shifted by about one day for every 10 mm snow water equivalent of precipitation. This effect is comparable in scale to that of doubling of the amount of LAP concentration in snow. We also found that the combined shift in snow cover duration from interannual variability in ambient temperature and shortwave radiation (warm and bright vs. cold and dark season) is large enough to explain the variability of a couple of weeks for a given precipitation amount in Northern Finland., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Aerosols have been associated with large uncertainties in estimates of the radiation budget and cloud formation processes in the Arctic. This paper reports the results of a study of in situ measurements of hygroscopicity, fraction of volatile species, mixing state, and off-line morphological and elemental analysis of Aitken and accumulation mode particles in the Arctic (Ny-Ålesund, Svalbard) in May and September 2012. The accumulation mode particles were more abundant in May than in September. This difference was due to more air mass flow from lower latitude continental areas, weaker vertical mixing, and less wet scavenging in May than in September, which may have led to a higher amount of long-range transport aerosols entering the Arctic in the spring. The Aitken mode particles observed intermittently in May were produced by nucleation, absent significant external mixing, whereas the accumulation mode particles displayed significant external mixing. The occurrence of an external mixing state was observed more often in May than in September and more often in accumulation mode particles than in Aitken mode particles, and it was associated more with continental air masses (Siberian) than with other air masses. The external mixing of the accumulation mode particles in May may have been caused by multiple sources (i.e., long-range transport aerosols with aging and marine aerosols). These groups of externally mixed particles were subdivided into different mixing structures (internal mixtures of predominantly sulfates and volatile organics without nonvolatile species and internal mixtures of sulfates and nonvolatile components, such as sea salts, minerals, and soot). The variations in the mixing states and chemical species of the Arctic aerosols in terms of their sizes, air masses, and seasons suggest that the continuous size-dependent measurements observed in this study are useful for obtaining better estimates of the effects of these aerosols on climate change.