| 161. |
- Krecl, Patricia, et al.
(författare)
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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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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 165, s. 155-168
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Tidskriftsartikel (refereegranskat)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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| 162. |
- Kristensson, Adam, et al.
(författare)
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Real-world traffic emission factors of gases and particles measured in a road tunnel in Stockholm, Sweden
- 2004
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 38:5, s. 657-673
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Tidskriftsartikel (refereegranskat)abstract
- Measurements in a road tunnel in Stockholm, Sweden give the real-world traffic emission factors for a number of gaseous and particle pollutants. These include 49 different polycyclic aromatic hydrocarbons (PAH), CO, NOX, benzene, toluene, xylenes, aldehydes, elements and inorganic/organic carbon contained in particles, the sub-micrometer aerosol number size distribution, PM2.5 and PM10. The exhaust pipe emission factors are divided with the help of automated traffic counts into the two pollutant sources, the heavy-duty vehicles (HDV) and light-duty vehicles (LDV). The LDV fleet contains 95% petrol cars and the total fleet contains about 5% HDV. When data permitted, the emission factors were further calculated at different vehicle speeds. The current work shows that average CO, NOX and benzene emission factors amounted to 5.3, 1.4 and 0.017 g veh(-1) km(-1), respectively. Since the mid-90s CO and benzene decreased by about 15%, carbonyls by about a factor 2, whereas NOX did not change much. PAR emission factors were 2-15 times higher than found during dynamometer tests. Most particles are distributed around 20 nm diameter and the LDV fleet contributes to about 65% of both PM and particle number. In general, the gaseous emissions are higher in Sweden than in USA and Switzerland, foremost due to the lower fraction catalytic converters in Sweden. The PM and number emissions of particles are also slightly higher in the Swedish tunnel. (C) 2003 Elsevier Ltd. All rights reserved.
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| 163. |
- Kudzotsa, Innocent, et al.
(författare)
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Modeled aerosol-cloud indirect effects and processes based on an observed partially glaciated marine deep convective cloud case
- 2019
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 204, s. 12-21
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Tidskriftsartikel (refereegranskat)abstract
- A tropical maritime case of deep convective clouds was studied using a state-of-the-art aerosol-cloud model in order to evaluate the microphysical mechanisms of aerosol indirect effects (AIE). The aerosol-cloud scheme used is a hybrid bin/bulk model, which treats all phases of clouds and precipitation allowing a detailed analysis of process-level aerosol indirect effects on targeted cloud types. From the simulations, a substantially huge total AIE on maritime clouds of −17.44 ± 6.1 Wm −2 was predicted primarily because maritime clouds are highly sensitive to perturbations in aerosol concentrations because of their low background aerosol concentrations. This was evidenced by the conspicuous increases in droplet and ice number concentrations and the subsequent reductions in particle mean sizes in the present-day. Both the water-only (−9.08 ± 3.18 Wm −2 ) and the partially glaciated clouds (−8.36 ± 2.93 Wm −2 ) contributed equally to the net AIE of these maritime clouds. As for the partially glaciated clouds, the mixed-phase component (−14.12 ± 4.94 Wm −2 ) of partially glaciated clouds was dominant, whilst the ice-only component (5.76 ± 1.84 Wm −2 ) actually exhibited a positive radiative forcing at the top of the atmosphere (TOA). This was primarily because ice water contents aloft were diminished significantly owing to increased snow production in the present-day.
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| 164. |
- Kulan, Abdulhadi, et al.
(författare)
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Distribution of 7Be in surface air of Europe
- 2006
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 40:21, s. 3855-3868
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Tidskriftsartikel (refereegranskat)abstract
- This study deals with long-term (span over three decades, 1972-2003) distribution of the cosmogenic isotope Be-7 in surface air at 5 stations in Europe, extending from latitude 47 degrees N to 68 degrees N. The results suggest annual variability in all the data sets as well as a decrease in average Be-7 activity with increasing latitude. Furthermore, a 9-10-year cyclical pattern is observed in the Be-7 distribution, which is anticorrelated with the solar activity cycle. Our data also indicate a dynamic range of Be-7 activity for each solar cycle and phase (maximum or minimum) which is higher at the middle compared to high-latitude regions. Additionally, about 10-20% relative deviation is observed in Be-7 activity during solar maxima and minima compared to the total average Be-7. This feature indicates that some deviation in the worldwide Be-7 activity data may relate to their acquisition, with respect to which part of a solar cycle they have been collected in (time span) and at which latitudinal spread. Estimate of Be-7 flux onto European surface boundary layer vary from 0.4 to 0.9 x 10(10) atoms m(-2) yr(-1) which is strongly latitude dependent and our average value is comparable to the similar to 0.7-0.8 x 10(10) atoms m(-2) yr(-1) across ocean and land.
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| 165. |
- Laj, P., et al.
(författare)
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Measuring Atmospheric Composition Change
- 2009
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1873-2844 .- 1352-2310. ; 43:33, s. 5351-5414
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Tidskriftsartikel (refereegranskat)abstract
- Scientific findings from the last decades have clearly highlighted the need for a more comprehensive approach to atmospheric change processes. In fact, observation of atmospheric composition variables has been an important activity of atmospheric research that has developed instrumental tools (advanced analytical techniques) and platforms (instrumented passenger aircrafts, ground-based in-situ and remote sensing stations, earth observation satellite instruments) providing essential information on the composition of the atmosphere. The variability of the atmospheric system and the extreme complexity of the atmospheric cycles for short-lived gaseous and aerosol species have led to the development of complex models to interpret observations, test our theoretical understanding of atmospheric chemistry and predict future atmospheric composition. The validation of numerical models requires accurate information concerning the variability of atmospheric composition for targeted species via comparison with observations and measurements. In this paper, we provide an overview of recent advances in instrumentation and methodologies for measuring atmospheric composition changes from space, aircraft and the surface as well as recent improvements in laboratory techniques that permitted scientific advance in the field of atmospheric chemistry. Emphasis is given to the most promising and innovative technologies that will become operational in the near future to improve knowledge of atmospheric composition. Our current observation capacity, however, is not satisfactory to understand and predict future atmospheric composition changes, in relation to predicted climate warming. Based on the limitation of the current European observing system, we address the major gaps in a second part of the paper to explain why further developments in current observation strategies are still needed to strengthen and optimise an observing system not only capable of responding to the requirements of atmospheric services but also to newly open scientific questions.
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| 166. |
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| 167. |
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| 168. |
- Larsen, B. R., et al.
(författare)
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Sources for PM air pollution in the Po Plain, Italy: II. Probabilistic uncertainty characterization and sensitivity analysis of secondary and primary sources
- 2012
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 50, s. 203-213
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Tidskriftsartikel (refereegranskat)abstract
- Very high levels of ambient particulate matter (PM) are frequently encountered in the north of Italy and air quality limits are regularly exceeded. To obtain quantitative information on the pollution sources and to gain understanding of the dynamics of pollution episodes in this populated area PM10 and/or PM2.5 samples were collected daily at nine urban to regional sites distributed over the central Po Plain and one site in the Valtelline Valley. In total, 23 five-week winter campaigns and one comparative summer/ autumn campaign (2007-2009) were organized. The PM was analyzed for 61 chemical constituents and a data-base was built up consisting of approx. 70000 records of the concentrations and their associated uncertainty. In addition C-14/C-12 ratios were determined in PM10 from four sites. Primary and secondary sources were quantified using macro-tracer methods in combination with chemical mass balance modelling and positive matrix factorization and the combined results were computed by probability-and sensitivity analysis. Monte Carlo simulations yielded probability distributions for seven source categories contributing to the carbonaceous fraction of PM and five major source categories contributing to the PM10 and PM2.5 mass. Despite large uncertainties in the combined source contribution estimates the paper demonstrates that secondary aerosol formed simultaneously over the Po Plain is the main responsible for the typical, rapid build-up of air pollution after clean-air episodes. Next to secondary sources, the most important sources are primary emissions from road transport followed by biomass burning (BB). In the Valtelline Valley, higher contributions from BB and lower contributions from secondary sources were observed. (C) 2012 Elsevier Ltd. All rights reserved.
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| 169. |
- Larsson, Per
(författare)
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Atmospheric deposition of persistent pollutants governs uptake in freshwater zooplankton
- 1989
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844 .- 0004-6981. ; 23:10, s. 2151-2158
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Tidskriftsartikel (refereegranskat)abstract
- The atmospheric fallout of PCBs, ∑DDT and γ-HCH (lindane) to a pond in southern Sweden was studied in relation to uptake by freshwater Zooplankton. The extent of the atmospheric deposition of PCBs and lindane was reflected in the uptake by the Zooplankton; high deposition in the spring and autumn resulted in high uptake by the organisms while a lower uptake during summer was a result of lower deposition. The atmospheric deposition of ∑DDT was dominated by p,p-DDT, p,p-DDE and o,p-DDT, while p,p-DDE and p,p-DDD were dominant in Zooplankton. These differences in ∑DDT composition are probably attributed to microbial conversion; as a result, levels in the Zooplankton appeared not to be governed by atmospheric deposition. The availability of the previously airborne, persistent pollutants to Zooplankton was a function of the compounds chemical properties, e.g. water solubility, and the form of deposition. The results show that atmospheric deposition is an important route by which persistent pollutants are transported to Holarctic, aquatic ecosystems.
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| 170. |
- Larsson, Per, et al.
(författare)
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Atmospheric transport of chlorinated hydrocarbons to Sweden 1985 compared to 1973
- 1989
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844 .- 0004-6981. ; 23:8, s. 1699-1711
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Tidskriftsartikel (refereegranskat)abstract
- The atmospheric fallout of DDT and DDE (ΣDDT) over Sweden has decreased during the last decade. Today long-range transport from southern sources outside the country dominates the inflow. This was reflected in a decreasing south-to-north gradient of the compounds in atmospheric deposition and in the lower atomosphere. The fallout of PCBs was similar in 1984–1985 and 1972–1973, and today local contamination by combustion is more prominent than it was 10 years ago, even though PCB restrictions have been in force during the interim. Since PCB deposition is higher in the coastal areas than in the inland regions, other sources, such as volatilization from the seas and long-range transport also contribute to PCBs in fallout. The levels of PCB and ΣDDT in the lower atmosphere were positively correlated with temperature. Consequently, the compounds tended to be in the gas phase during the warmer summer period whereas during winter they were more liable to be adsorbed to particles, partition to airborne water and contribute in fallout. From each sampling station a chromatographic 'fingerprint' of pollutants in airborne fallout and in the lower atmosphere was obtained. The fingerprint was the combined result of the station's location and climate. The results show that considerable amounts of chlorinated pollutants are being transported to and within Sweden via the atmosphere.
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