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- Ahn, Seo H., et al.
(author)
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Relationship between cloud condensation nuclei (CCN) concentration and aerosol optical depth in the Arctic region
- 2021
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 267
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Journal article (peer-reviewed)abstract
- To determine the direct and indirect effects of aerosols on climate, it is important to know the spatial and temporal variations in cloud condensation nuclei (CCN) concentrations. Although many types of CCN measurements are available, extensive CCN measurements are challenging because of the complexity and high operating cost, especially in remote areas. As aerosol optical depth (AOD) can be readily observed by remote sensing, many attempts have been made to estimate CCN concentrations from AOD. In this study, the CCN-AOD relationship is parameterized based on CCN ground measurements from the Zeppelin Observatory (78.91 degrees N, 11.89 degrees E, 474 m asl) in the Arctic region. The AOD measurements were obtained from the Ny-Alesund site (78.923 degrees N, 11.928 degrees E) and Modern-Era Retrospective Analysis for Research and Applications, Version 2 reanalysis. Our results show a CCN-AOD correlation with a coefficient of determination R-2 of 0.59. Three additional estimation models for CCN were presented based on the following data: (i) in situ aerosol chemical composition, (ii) in situ aerosol optical properties, and (iii) chemical composition of AOD obtained from reanalysis data. The results from the model using in situ aerosol optical properties reproduced the observed CCN concentration most efficiently, suggesting that the contribution of BC to CCN concentration should be considered along with that of sulfate.
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| 4. |
- Krecl, Patricia, et al.
(author)
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Diurnal variation of atmospheric aerosol during the wood combustion season in Northern Sweden
- 2008
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 42:18, s. 4113-4125
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Journal article (peer-reviewed)abstract
- A set of aerosol measurements was conducted in the residential area of Forsdala in Lycksele, Northern Sweden, during winter 2005/2006. This article describes the temporal and diurnal variation of the aerosol physical properties (concentrations of PM10, PM1, light-absorbing carbon, and particle number, and number size distributions), and the relationship among aerosol concentrations and meteorological variables. A large day-to-day and hour-to-hour variability in aerosol concentrations was observed during the intensive study period. Evening aerosol concentrations were statistically significantly higher on weekends than on weekdays. On weekdays, particle size distribution and concentrations varied diurnally with small particles (diameter <30 nm) associated mainly with morning motor vehicle emissions. The results suggest that a combination of emissions from residential wood combustion and traffic sources might explain the high evening concentrations of PM10, PM1, particle number, and light-absorbing carbon as well as large geometric mean diameters observed during weekdays and weekends. Strong correlations of PM10 and PM1 with particle size distributions are found in the diameter range 130–500 nm and are remarkably high on weekend evenings when larger particles are sampled. The correlation between light-absorbing carbon mass concentration and particle size distribution is high regarding both particle number and mass for particle diameters >95 nm. High aerosol concentrations were associated with low air temperatures and very stable atmospheric conditions close to the ground.
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| 5. |
- Krecl, Patricia, et al.
(author)
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Trends in black carbon and size-resolved particle number concentrations and vehicle emission factors under real-world conditions
- 2017
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 165, s. 155-168
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Journal article (peer-reviewed)abstract
- 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 EFBC 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 EFBC 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.
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| 7. |
- Weinbruch, Stephan, et al.
(author)
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Chemical composition and sources of aerosol particles at Zeppelin Mountain (Ny Alesund, Svalbard) : An electron microscopy study
- 2012
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 49, s. 142-150
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Journal article (peer-reviewed)abstract
- Aerosol particles were collected at the Zeppelin Mountain Atmospheric Research Station (474 m asl) near Ny Alesund (Svalbard, Norway) on 27 different days between July 2007 and December 2008. The size, morphology and chemical composition of 57,617 individual particles were studied by high-resolution scanning electron microscopy and energy-dispersive X-ray microanalysis. Based on chemical composition, morphology, mixing state and stability under electron bombardment, the particles were assigned to one of the following groups: sea salt, aged sea salt, Ca sulphates, Na sulphates, carbonates, soot, silicates, fly ashes, secondary aerosol, secondary aerosol plus sodium, secondary aerosol plus soot, mixed particles and others. Sea salt, aged sea salt, silicates and mixed particles (mixtures of sea salt, silicates and Ca sulphates) are the most abundant groups for particles with aerodynamic diameters > 0.5 mu m, secondary aerosol, mixed particles and secondary aerosol with soot inclusions below 0.5 mu m. Silicate fly ashes (major source coal burning) and metal fly ashes (from metallurgical high temperature processes) occur only at very low number concentrations. In contrast to previous work, the fly ash abundance is not correlated with air masses that crossed industrialized regions in Central and Eastern Europe, Scandinavia or Russia. These observations indicate a significant reduction of long-range transport of heavy metals to Svalbard. Soot (external and internally mixed with secondary aerosol) shows a pronounced seasonal pattern with a much lower abundance during summer compared to spring, autumn and winter. The soot abundance is not correlated with the air mass back-trajectories. During summer (July and August), soot was only observed when cruise ships were present in the area around Ny Alesund (Kongsfjorden). Pronounced seasonal patterns were observed for the abundance of the mineral dust component which is generally lower in summer compared to the other seasons. The observed seasonal dependence of anthropogenic primary particles (soot, fly ashes) is in good agreement with the Arctic circulation pattern.
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