| 1. |
- Agrell, Cecilia, et al.
(författare)
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PCB congeners in precipitation, wash out ratios and depositional fluxes within the Baltic Sea region, Europe
- 2002
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Ingår i: Atmospheric Environment. - 1352-2310. ; 36:2, s. 371-383
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Tidskriftsartikel (refereegranskat)abstract
- Concentrations of PCB congeners were determined in precipitation and the annual and seasonal depositional fluxes were calculated for 16 (mostly rural) stations around the Baltic Sea during 1990-1993. The concentrations of individual congeners in precipitation were found to be influenced by atmospheric concentrations of PCBs, ambient temperature, precipitation volume and physico-chemical properties of the compounds. Median levels of PCBs in precipitation differed one order of magnitude between stations. When analyzing all data together to obtain regional trends, concentrations of PCBs in precipitation decreased with increasing temperature. This relationship was the same for all stations but differed in the magnitude of the slope for individual congeners. Low chlorinated PCB congeners showed steeper slopes for the temperature relationship than did high chlorinated congeners, a result explained by high atmospheric concentrations of the low chlorinated congeners during low temperatures. Annual wash out ratios were between 31 and 72 x 103 and tended to be higher for the high chlorinated congeners. Wash out ratios decreased with increasing temperature for all congeners except PCB-33. At snow scavenging events, the wash out ratio of PCBs increased with a factor of 2. Latitudinal trends for PCB concentrations in precipitation and deposition were generally not statistically significant. The calculated yearly deposition of PCBs to the Baltic Sea was 390 and 5-18 kg for individual congeners, with PCB-138 having the highest flux. Deposition of PCB congeners varied seasonally, with a factor between 2 and 3, and was generally highest during fall. Relatively higher deposition of low chlorinated congeners compared to high chlorinated congeners was found during winter. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 2. |
- Backe, Cecilia, et al.
(författare)
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Polychlorinated biphenyls in the air of southern Sweden - spatial and temporal variation
- 2000
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Ingår i: Atmospheric Environment. - 1352-2310. ; 34:9, s. 1481-1486
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Tidskriftsartikel (refereegranskat)abstract
- Polychlorinated biphenyls in the lower atmosphere were studied over a regional area covering approximately 11000 km(2) in southern Sweden. Sampling were performed in 1992-1993, continuously during one year, where samples from 11 sampling-sites (in all 260 samples) were analysed. PCB concentrations ranged over two order of magnitudes, 7-983 pg m(-3). Differences in PCB concentrations among the sampling sites revealed a large number of high-concentration outliers, mainly originating from one suburban site. Smaller differences in PCB concentrations between sites probably originated from varying geographical and meteorological conditions, that affected exchange processes between air and surfaces differently at the sampling sites. (C) 2000 Elsevier Science Ltd. All rights reserved.
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| 3. |
- Berglund, Johan, et al.
(författare)
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Manganese-Catalyzed Autoxidation of Dissolved Sulfur Dioxide in the Atmospheric Aqueous Phase
- 1995
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Ingår i: Atmospheric Environment. - 1352-2310. ; 29:12, s. 1379-1391
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Tidskriftsartikel (refereegranskat)abstract
- Autoxidation of SO2(aq) in the presence of manganese(II) is one of the important pathways for sulfuric acid formation in atmospheric clouds and fogs. Recent experimental results indicating that the catalyzed reaction takes place via a complex free-radical mechanism are discussed. Previous literature is reviewed in the light of this mechanism. Under atmospheric conditions of low total concentrations of manganese(II) ( < 2 × 10−5 M) and sulfur(IV) ( ≤ 10−5 M) and 2.5 < pH < 5, the rate law for conversion of SO2(aq) to SO3(aq) is reduced to d[S(IV)]/dt = k[Mn(II)][S(IV)], where [S(IV)] denotes the total concentration. A value of the overall rate constant k of 1.4 × 103 M−1s−1 is recommended for use in atmospheric model calculations.
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| 4. |
- Brandt, Christian, et al.
(författare)
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Role of Chromium and Vanadium in the Atmospheric Oxidation of Sulfur(IV)
- 1998
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Ingår i: Atmospheric Environment. - 1352-2310. ; 32:4, s. 797-800
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Tidskriftsartikel (refereegranskat)abstract
- Oxidation of HSO3- in aqueous solution has been studied in the presence of vanadium(V), chromium(III) and chromium(VI). Based on spectrophotometric kinetics data and product analysis it is concluded that the autoxidation rate of sulfur(IV) in slightly acidic solution is unaffected by the presence of vanadium(V) and chromium(III). Chromate(VI), on the other hand, oxidizes sulfur(IV) in a direct redox process in acidic solution. The overall rate of this reaction decreases with increasing pH and it becomes relatively slow in the atmospherically relevant pH range 4-6. Moreover, chromium(III) dominates strongly over chromium(VI) in the atmospheric aqueous phase. Hence, it is concluded that cations of vanadium vanadium and chromium have no significant influence on the atmospheric aqueous-phase oxidation of sulfur(IV) under most ambient atmospheric conditions. Only in very acidic droplets, direct redox between chromium(VI) and sulfite might be of some importance.
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| 5. |
- Cederfelt, S. I., et al.
(författare)
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Field validation of the droplet aerosol analyser
- 1997
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Ingår i: Atmospheric Environment. - 1352-2310. ; 31:16, s. 2657-2670
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Tidskriftsartikel (refereegranskat)abstract
- A new instrument for the study of cloud droplets and its relation to aerosol particles, the droplet aerosol analyser (DAA), was for the first time used in a field campaign. The DAA has the unique feature of measuring the ambient size of cloud droplets or cloud interstitial aerosol particles together with the size of its dry residue. This is obtained with a two-parameter data acquisition technique which results in a three-dimensional data set (ambient size, dry residue size, number concentration). The principle and design of the DAA is briefly described. The DAA was intercompared with differential mobility particle sizers, particulate volume monitors and a forward scattering spectrometer probe with respect to interstitial and cloud droplet dry residue size distribution as well as particle-size-dependent scavenging due to cloud droplet nucleation and for cloud droplet number concentration and size distribution and cloud liquid water concentration. Overall, the DAA showed good agreement with respect to all these six aerosol/cloud properties.
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| 6. |
- Choularton, T. W., et al.
(författare)
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The Great Dun Fell Cloud Experiment 1993 : An overview
- 1997
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Ingår i: Atmospheric Environment. - 1352-2310. ; 31:16, s. 2393-2405
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Tidskriftsartikel (refereegranskat)abstract
- The 1993 Ground-based Cloud Experiment on Great Dun Fell used a wide range of measurements of trace gases, aerosol particles and cloud droplets at five sites to study their sources and sinks especially those in cloud. These measurements have been interpreted using a variety of models. The conclusions add to our knowledge of air pollution, acidification of the atmosphere and the ground, eutrophication and climate change. The experiment is designed to use the hill cap cloud as a flow-through reactor, and was conducted in varying levels of pollution typical of much of the rural temperate continental northern hemisphere in spring-time.
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| 7. |
- Ferrara, R, et al.
(författare)
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Atmospheric mercury concentrations and fluxes in the Almaden District (Spain)
- 1998
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Ingår i: Atmospheric Environment. - 1352-2310. ; 32:22, s. 3897-3904
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric mercury levels around the world's largest mining and refining complex (Almaden, Spain) were determined during two field campaigns (September 1993 and February 1994) using both point monitors and lidar techniques. High mercury concentrations (0.1-5 mu g m(-3)) were measured over the village of Almaden in the prevailing wind direction. In the month of September the total mercury flux into the atmosphere was estimated to range from 600 to 1200 g h(-1). An attempt was made to measure the contribution from individual mercury sources. (C) 1998 Elsevier Science Ltd. All rights reserved.
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| 8. |
- Gidhagen, L, et al.
(författare)
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Model simulation of ultrafine particles inside a road tunnel
- 2003
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Ingår i: Atmospheric Environment. - 1352-2310. ; 37:15, s. 2023-2036
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Tidskriftsartikel (refereegranskat)abstract
- A monodispersive aerosol dynamic model, coupled to a 3D hydrodynamical grid model, has been used to study the dynamics of ultrafine particles inside a road tunnel in Stockholm, Sweden. The model results were compared to measured data of particle number concentrations, traffic intensity and tunnel ventilation rate. Coagulation and depositional losses to the tunnel walls were shown to be important processes during traffic peak hours, together contributing to losses of 77% of the particles smaller than 10nm and 41% of the particles of size 10-29nm. Particle growth due to water uptake or the presence of a micron-sized, resuspended particle fraction did not have any significant effect on the number of particles lost due to coagulation. Model simulation of particle number concentration response to temporal variations in traffic flow showed that constant emission factors could be used to reproduce the concentration variations of the particles larger than 29nm, while vehicle-speed-dependent factors are suggested to reproduce the variation of the smallest fractions. The emission factors for particle number concentrations estimated from the model simulation are in general higher and show a larger contribution from light-duty vehicles than what has been reported from a tunnel in California. The model study shows that combined measurements and model simulations in road tunnels can be used to improve the determinations of vehicle emission factors for ultrafine particles under realistic driving conditions. (C) 2003 Elsevier Science Ltd. All rights reserved.
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| 9. |
- Gieray, R., et al.
(författare)
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Phase partitioning of aerosol constituents in cloud based on single-particle and bulk analysis
- 1997
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Ingår i: Atmospheric Environment. - 1352-2310. ; 31:16, s. 2491-2502
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Tidskriftsartikel (refereegranskat)abstract
- Single-particle analysis, performed by laser microprobe mass spectrometry and bulk analytical techniques were used to study aerosol-cloud interactions within the third field campaign of the EUROTRAC subproject 'ground-based cloud experiments' at the Great Dun Fell, Cumbria, U.K. in spring 1993. The shape of the ridge made it possible for ground-based instrumentation to sample similar parcels of air before, during and after their transit through the cloud. A single jet five-stage minicascade impactor was used for sampling particles of the interstitial aerosol. A second impactor worked in tandem with a counter-flow virtual impactor and collected residues of cloud droplets. Considering marine conditions largest droplets nucleated on sea-salt particles, whereas smaller droplets were formed on sulphate and methane sulphonate containing particles. This clearly indicates chemical inhomogeneities in the droplet phase. Particles, which were disfavoured by droplet formation, often contained the highest amounts of water-insoluble carbonaceous matter. For the submicron size range we found that the carbonaceous matter was always internally mixed with sulphate. The fraction of carbonaceous matter increased with decreasing size. A detectable fraction of particles remained in the cloud interstitial air, although they were in size as well as in composition suitable to form cloud droplets. The findings confirm that nucleation is the most important process affecting phase partitioning in cloud, but that spatial and temporal variations of water vapour supersaturation have also an influence on the observed phase partitioning. Proton induced X-ray emission analysis and light absorption measurements of filter samples showed that the average scavenged fraction was 0.77 for sulphur and 0.57 for soot in clouds formed by continental influenced air and 0.62 and 0.44, respectively, for marine influenced clouds.
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| 10. |
- Hedberg, E, et al.
(författare)
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Chemical and physical characterization of emissions from birch wood combustion in a wood stove
- 2002
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Ingår i: Atmospheric Environment. - 1352-2310. ; 36:30, s. 4823-4837
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to characterize the emissions of a large number of chemical compounds emitted from birch wood combustion in a wood stove. Birch wood is widely used as fuel in Swedish household appliances. The fuel load was held constant during six experiments. Particles < 2.5 mum diameter were collected and the size distribution of the particles was measured. The results were compared to the size distribution in road traffic emissions. It could be seen that the number distribution differed between the sources. In traffic exhaust, the number of particles maximized at 20 nm, while the number distribution from wood burning ranged from 20 to 300 nm. The ratio K/Ca on particles was found. to be significantly different in wood burning compared to road dust, range 30-330 for the former and 0.8+/-0.15 for the latter. The source profile of common elements emitted from wood-burning differed from that found on particles at a street-level site or in long-distance transported particles. The ratio toluene/benzene in this study was found to be in the range 0.2-0.7, which is much lower than the ratio 3.6+/-0.5 in traffic exhaust emissions. Formaldehyde and acetone were the most abundant compounds among the volatile ketones and aldehydes. The emission factor varied between 180-710mg/kg wood for formaldehyde and 5-1300mg/kg wood for acetone. Of the organic acids analyzed (3,4,5)-trimethoxy benzoic acid was the most abundant compound. Of the PAHs reported, fluorene, phenanthrene, anthracene, fluoranthene and pyrene contribute to more than 70% of the mass of PAH. Of the elements analyzed, K and Si were the most abundant elements, having emission factors of 27 and 9mg/kg wood, respectively. Although fluoranthene has a toxic equivalence factor of 5% of benzo(a)pyrene (B(a)P), it can be seen that the toxic potency of fluoranthene in wood burning emissions is of the same size as B(a)P. This indicates that the relative carcinogenic potency contribution of fluoranthene in wood smoke would be about 40% of B(a)P. (C) 2002 Elsevier Science Ltd. All rights reserved.
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