| 11. |
- Eliasson, Ingegärd, 1961, et al.
(författare)
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Wind fields and turbulence statistics in an urban street canyon
- 2006
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 40:1, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- This is the first paper of a long-term measurement campaign to explore wind, temperature, radiation and energy fieldswithin an urban canyon. A canyon and a rooftop mast were installed in a canyon with an aspect ratio (Height/Width)of 2.1 in Goteborg, Sweden. A number of instruments including sonic anemometers, radiometers and thermocoupleswere mounted in vertical profiles and across the width of the canyon. The experimental set-up, the characteristics of thecanyon flow pattern and mean and turbulence statistics with respect to above canyon flow are examined using datacollected under clear-sky conditions in summer and autumn 2003. Results show that under cross-canyon (within 601 oforthogonal) flow, a single helical vortex exists. High temporal resolution analysis suggests that eddies frequentlypenetrate the shear stress layer at the canyon top disrupting established flow patterns. A combination of complexbuilding roof shapes and local topography may contribute to this effect by maintaining a high degree of turbulence. Theprofile of mean wind speed within the canyon and the relation with that above canyon depends on the ambient flowdirection in relation to the canyon long axis. Turbulence statistics show results similar to other field studies, withturbulence kinetic energy and vertical mixing greatest toward the windward wall.
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| 12. |
- Eneroth, Kristina, et al.
(författare)
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Springtime depletion of tropospheric ozone, gaseous elemental mercury and non-methane hydrocarbons in the European Arctic, and its relation to atmospheric transport
- 2007
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 41:38, s. 8511-8526
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Tidskriftsartikel (refereegranskat)abstract
- Using a trajectory climatology for the period 1992-2001 we have examined how seasonal changes in transport cause changes in the concentrations of tropospheric ozone (O-3), gaseous elemental mercury (GEM) and non-methane hydrocarbons (NMHCs) observed at the Mt. Zeppelin station, Ny-angstrom lesund (78.9 degrees N, 11.9 degrees E). During April-June O-3 depletion events were frequently observed in connection with air transport across the Arctic Basin. The O-3 loss was most pronounced in air masses advected close to the surface. This result supports the idea that the O-3 depletion reactions take place in the lowermost part of the atmosphere in the central Arctic Basin. A strong positive correlation between springtime O-3 depletion events and the oxidation of GEM to divalent mercury was found. During air mass advection from Siberia, the Barents Sea and the Norwegian Sea the strongest correlation was observed during April-May, whereas air masses originating from the Canadian Arctic and the central Arctic areas showed the highest O-3-GEM correlation in May-June. We suggest that this 1-month lag could either be due to the position of the marginal ice zone or temperature differences between the northwestern and northeastern air masses. In connection with springtime O-3 depletion events low concentrations of some NMHCs, especially ethane and ethyne, were observed, indicating that both bromine (ethyne oxidant) and chlorine radicals (ethane oxidant) are present in the Arctic atmosphere during spring. In winter, negative correlations between O-3 and NMHCs were found in connection with air transport from Europe and Siberia, which we interpret as O-3 destruction taking place in industrially contaminated plumes.
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| 13. |
- Fick, Jerker, et al.
(författare)
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Ozonolysis of monoterpenes in mechanical ventilation systems
- 2005
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Ingår i: ATMOSPHERIC ENVIRONMENT. - : Elsevier BV. - 1352-2310. ; 39:34, s. 6315-25
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Tidskriftsartikel (refereegranskat)abstract
- In this investigation the ozonolysis of of three monoterpenes (alpha-pinene, Delta(3)-carene and limonene) was studied was studied in authentic mechanical ventilation systems, that included either a cross flow or a rotary heat exchanger. The effects of varying three experimental parameters were investigated: the level of ozone (25 and 75 ppb), the reaction time (25 and 75s), and the surface area in the ventilation duct (14.8 and 29.5 m(2)). The initial concentration of each of the monoterpenes was 20 ppb in every experiment, and 1-16% of the alpha-pinene, < 0.5-13% of the Delta(3)-carene, and < 0.5-16% of the limonene reacted. The effects of humidity (g m(-3)) and temperature of the outdoor and supply air, and water losses in the ventilation duct, were also evaluated. Experiments were based on a chemometric statistical design. Comparison of the results to theoretically calculated values showed that theoretical calculations underestimated the amounts that reacted in the ventilation systems by factors of 2-13, depending on the monoterpene and experimental settings.
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| 14. |
- Fowler, D., et al.
(författare)
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Atmospheric composition change : Ecosystems-Atmosphere interactions
- 2009
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 43:33, s. 5193-5267
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Forskningsöversikt (refereegranskat)abstract
- Ecosystems and the atmosphere: This review describes the state of understanding the processes involved in the exchange of trace gases and aerosols between the earth's surface and the atmosphere. The gases covered include NO, NO2, HONO, HNO3, NH3, SO2, DMS, Biogenic VOC, O-3, CH4, N2O and particles in the size range 1 nm-10 mu m including organic and inorganic chemical species. The main focus of the review is on the exchange between terrestrial ecosystems, both managed and natural and the atmosphere, although some new developments in ocean-atmosphere exchange are included. The material presented is biased towards the last decade, but includes earlier work, where more recent developments are limited or absent. New methodologies and instrumentation have enabled, if not driven technical advances in measurement. These developments have advanced the process understanding and upscaling of fluxes, especially for particles, VOC and NH3. Examples of these applications include mass spectrometric methods, such as Aerosol Mass Spectrometry (AMS) adapted for field measurement of atmosphere-surface fluxes using micrometeorological methods for chemically resolved aerosols. Also briefly described are some advances in theory and techniques in micrometeorology. For some of the compounds there have been paradigm shifts in approach and application of both techniques and assessment. These include flux measurements over marine surfaces and urban areas using micrometeorological methods and the up-scaling of flux measurements using aircraft and satellite remote sensing. The application of a flux-based approach in assessment of O-3 effects on vegetation at regional scales is an important policy linked development secured through improved quantification of fluxes. The coupling of monitoring, modelling and intensive flux measurement at a continental scale within the NitroEurope network represents a quantum development in the application of research teams to address the underpinning science of reactive nitrogen in the cycling between ecosystems and the atmosphere in Europe. Some important developments of the science have been applied to assist in addressing policy questions, which have been the main driver of the research agenda, while other developments in understanding have not been applied to their wider field especially in chemistry-transport models through deficiencies in obtaining appropriate data to enable application or inertia within the modelling community. The paper identifies applications, gaps and research questions that have remained intractable at least since 2000 within the specialized sections of the paper, and where possible these have been focussed on research questions for the coming decade.
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| 15. |
- Glantz, Paul, et al.
(författare)
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Estimating PM2.5 over southern Sweden using space-borne optical measurements
- 2009
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 43:36, s. 5838-5846
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- in the present study Bremen aerosol retrieval (BAER) columnar aerosol optical thickness (ACT) data, according to moderate resolution imaging spectroradiometer (MODIS) and medium resolution imaging sensor (MERIS) level 1 calibrated satellite data, have been compared with ACT data obtained with the MODIS and MERIS retrieval algorithms (NASA and ESA, respectively) and by AErosol Robotic NETwork (AERONET). Relatively good agreement is found between these different instruments and algorithms. The R-2 and relative RMSD were 0.86 and 31% for MODIS when comparing with AERONET and 0.92 and 21% for MERIS. The aerosols investigated were influenced by low relative humidity. During this period, a relatively large range of aerosol loadings were detected; from continental background aerosol to particles emitted from agricultural fires. In this study, empirical relationships between BAER columnar AOT and ground-measured PM2.5 have been estimated. Linear relationships, with R-2 values of 0.58 and 0.59, were obtained according to MERIS and MODIS data, respectively. The slopes of the regression of ACT versus PM2.5 are lower than previous studies, but this could easily be explained by considering the effect of hygroscopic growth. The present AOT-PM2.5 relationship has been applied on MERIS full resolution data over the urban area of Stockholm and the results have been compared with particle mass concentrations from dispersion model calculations. it seems that the satellite data with the 300 m resolution can resolve the expected increased concentrations due to emissions along the main highways close to the city. Significant uncertainties in the spatial distribution of PM2.5 across land/ocean boundaries were particularly evident when analyzing the high resolution satellite data.
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| 16. |
- Grönlund, Rasmus, et al.
(författare)
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Elemental mercury emissions from chlor-alkali plants measured by lidar techniques
- 2005
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 39:39, s. 7474-7480
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Tidskriftsartikel (refereegranskat)abstract
- Differential absorption lidar (DIAL) techniques have been utilized to measure elemental gaseous mercury fluxes from mercury cell chlor-alkali (MCCA) plants as a part of the European Union funded European mercury emissions from chlor-alkali plants (EMECAP) project. Three plants have been selected as study objects and a total of six measurement campaigns have been performed, one intercalibration campaign and five flux evaluation campaigns, in both winter and summer. The measurements were carried out using the Swedish optical parametric oscillator-(OPO) based mobile lidar system developed at Lund Institute of Technology. The study shows large differences in the mercury emissions measured in winter or summer and at the different plants. The average values for the campaigns ranged from 6 g h(-1) in the winter campaign at the Swedish plant to 54 g h(-1) in the summer campaign at the Italian plant.
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| 17. |
- Grönlund, Rasmus, et al.
(författare)
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Mercury emissions from the Idrija mercury mine measured by differential absorption lidar techniques and a point monitoring absorption spectrometer
- 2005
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 39:22, s. 4067-4074
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Tidskriftsartikel (refereegranskat)abstract
- Mercury emission measurements from the ldrija mercury mine in Slovenia were performed during an early November 2003 campaign, where the differential lidar technique was used to map mercury concentrations and an attempt was made to quantify the total mercury flux from the most contaminated area, the abandoned cinnabar roasting oven complex. Lidar concentration data were compared with data recorded with a Zeeman modulated atomic absorption instrument, operated from a vehicle equipped with a GPS localization system. Concentrations and fluxes were comparatively low due to low temperature and rainfall. The average flux from the distillation plant was measured to approximately 2 g h(-1).
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| 18. |
- Gustafsson, Mats, et al.
(författare)
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Factors influencing PM10 emissions from road pavement wear
- 2009
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 43:31, s. 4699-4702
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Konferensbidrag (refereegranskat)abstract
- Accelerated pavement wear is one of the major environmental disadvantages of studded tyres in northern regions and results in increased levels of PM10. Measurements of PM10 in a road simulator hall have been used to study the influence of pavement properties, tyre type and vehicle speed on pavement wear. The test set-up included three different pavements (one granite and two quartzite with different aggregate sizes), three different tyre types (studded, non-studded, and summer tyres) and different speeds (30-70 km h(-1)). The results show that the granite pavement was more prone to PM10 production compared to the quartzite pavements. Studded winter tyres yield tens of times higher PM10 concentrations compared to non-studded winter tyres. Wear from summer tyres was negligible in comparison. It was also shown that wear is strongly dependent on speed; every 10 km h(-1) increase yielded an increase of the PM10 concentration of 680 mu g m(-3) in one of the simulator experiments. (C) 2008 Elsevier Ltd. All rights reserved.
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| 19. |
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| 20. |
- Götschi, Thomas, et al.
(författare)
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Elemental composition and reflectance of ambient fine particles at 21 European locations
- 2005
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Ingår i: Atmospheric Environment. - Oxford : Pergamon Press. - 1352-2310 .- 1873-2844. ; 39:32, s. 5947-5958
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Tidskriftsartikel (refereegranskat)abstract
- We sampled fine particles (PM2.5) over a 1-year period at 21 central urban monitoring sites in 20 cities of the European Community Respiratory Health Survey (ECRHS). Particle filters were then analysed for elemental composition using energy dispersive X-ray fluorescence spectrometry and reflectance (light absorption). Elemental analyses yielded valid results for 15 elements (Al, As, Br, Ca, Cl, Cu, Fe, K, Mn, Pb, S, Si, Ti, V, Zn). Annual and seasonal means Of PM2.5, reflectance, and elements show a wide range across Europe with the lowest levels found in Iceland and up to 80 times higher concentrations in Northern Italy. This pattern holds for most of the air pollution indicators. The mass concentration of S did constitute the largest fraction of the analysed elements Of PM2.5 in all locations. The crustal component varies from less than 10% up to 25% across these cities. Temporal correlations of daily values vary considerably from city to city, depending on the indicators compared. Nevertheless, correlations between estimates of long-term exposure, such as annual means, are generally high among indicators Of PM2.5 from anthropogenic sources, such as S, metals, and reflectance. This highlights the difficulty to disentangle effects of specific sources or PM constituents in future health effect analyses using annual averages.
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