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  • Agrell, C, et al. (författare)
  • PCB congeners in precipitation, wash out ratios and depositional fluxes within the Baltic Sea region, Europe
  • 2002
  • Ingår i: Atmospheric Environment. - Elsevier. - 1352-2310. ; 36:2, s. 371-383
  • 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.
  • Backe, C, et al. (författare)
  • Polychlorinated biphenyls in the air of southern Sweden - spatial and temporal variation
  • 2000
  • Ingår i: Atmospheric Environment. - Elsevier. - 1352-2310. ; 34:9, s. 1481-1486
  • 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.
  • Berglund, Johan, et al. (författare)
  • Manganese-Catalyzed Autoxidation of Dissolved Sulfur Dioxide in the Atmospheric Aqueous Phase
  • 1995
  • Ingår i: Atmospheric Environment. - Elsevier. - 1352-2310. ; 29:12, s. 1379-1391
  • 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. Keywords Autoxidation; catalysis; manganese; sulfur dioxide; radicals; synergism; atmospheric droplets
  • Brandt, Christian, et al. (författare)
  • Role of Chromium and Vanadium in the Atmospheric Oxidation of Sulfur(IV)
  • 1998
  • Ingår i: Atmospheric Environment. - Elsevier. - 1352-2310. ; 32:4, s. 797-800
  • 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.
  • Draaijers, GPJ, et al. (författare)
  • The impact of canopy exchange on differences observed between atmospheric deposition and throughfall fluxes
  • 1997
  • Ingår i: Atmospheric Environment. - Elsevier. - 1352-2310. ; 31:3, s. 387-397
  • Tidskriftsartikel (refereegranskat)abstract
    • To study the impact of canopy exchange on differences observed between atmospheric deposition and throughfall fluxes, several-held experiments were performed at the Speulder forest in The Netherlands. Relevant information was obtained by (i) measuring open-field precipitation and throughfall fluxes with different time resolutions, using two canopy exchange models, (ii) by comparing results from surface wash experiments using real and artificial twigs, respectively, and (iii) by comparing throughfall flux estimates with atmospheric deposition estimates from micrometeorological measurements and inferential modelling. Canopy uptake of gases through stomata was estimated using measured air concentrations and a stomatal conductance model. Specific information on canopy leaching of soil-derived sulphate was provided by a S-35 tracer experiment. Sulphur was found to behave conservatively within the canopy, with SO2 uptake more or less balancing leaching of soil-derived SO42-. Significant stomatal uptake of NO2, HNO2 and NH3 was calculated as well as uptake of H+ and NH4+ from water layers covering the tree surface. Experiments did not indicate significant uptake of NO3- in solution. Canopy uptake of H+ and NH4+ was countered by leaching of K+, Ca2+ and Mg2+. Part of the leaching of K+, Ca2+ and Mg2+ (15%) took place along with weak organic acids. No significant canopy exchange was found for Na+ and Cl-. Differences observed between atmospheric deposition and throughfall fluxes could almost completely be explained by canopy exchange, the difference between NOy deposition and NO3- throughfall flux being the only exception. Copyright (C) 1996 Elsevier Science Ltd
  • Feliciano, MS, et al. (författare)
  • Evaluation of SO2 dry deposition over short vegetation in Portugal
  • 2001
  • Ingår i: Atmospheric Environment. - Elsevier. - 1352-2310. ; 35:21, s. 3633-3643
  • Tidskriftsartikel (refereegranskat)abstract
    • SO2 dry deposition was studied over short vegetation, in Portugal, by means of the concentration gradient method. The experimental study involved one first phase of long-term measurements carried out in a grassland and, subsequently, a second period of several 1997 intensive field campaigns performed in three places representing different climate and surface conditions. Temporal and spatial patterns of dry deposition parameters show that downward fluxes of SO2 are by some extent affected by surface processes. Median R-c varied from 140 s cm(-1) to values around 200 s cm(-1), in a wide range of environmental conditions. Stomatal uptake is an important sink when vegetation is biologically active, but its contribution is effectively low when compared with non-stomatal mechanisms, especially when the surface is wet. Under dry conditions R-c increases by a factor of two, but SO2 deposition rates then still are significant. The parameterisation of the surface resistance for SO2 proved to be difficult, but V-d derived with the Erisman parameterisation (Erisman et al., atmos. Environ. 28 (16) (1994) 2595) compared best with measured values, at low time resolution scale and especially under moisture conditions. (C) 2001 Published by Elsevier Science Ltd.
  • Ferrara, R, et al. (författare)
  • Atmospheric mercury concentrations and fluxes in the Almaden District (Spain)
  • 1998
  • Ingår i: Atmospheric Environment. - Elsevier. - 1352-2310. ; 32:22, s. 3897-3904
  • 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.
  • Fick, Jerker, et al. (författare)
  • A study of the gas-phase ozonolysis of terpenes: the impact of radicals formed during the reaction
  • 2002
  • Ingår i: Atmospheric Environment. - 1352-2310. ; 36:20, s. 3299-3308
  • Tidskriftsartikel (refereegranskat)abstract
    • The gas-phase ozonolysis of α-pinene, Δ3-carene and limonene was investigated at ppb levels and the impact of the ozone, relative air humidity (RH), and time was studied using experimental design. The amounts of terpene reacted varied in the different settings and were as high as 8.1% for α-pinene, 10.9% forΔ3-carene and 23.4% for limonene. The designs were able to describe almost all the variation in the experimental data and were also successful in predicting omitted values. The results described the effects of time and ozone and also showed that RH did not have a statistically significant effect on the ozonolysis. The results also showed that all three terpenes were affected by an additional oxidation of OH radicals and/or other reactive species. The results from the designs states that this additional oxidation was responsible for 40% of the total amount of α-pinene reacted, 33% of the total amount of Δ3-carene reacted and 41% of the total amount of limonene reacted at the settings 20 ppb terpene, 75 ppb ozone, 20% RH and a reaction time of 213 s. Additional experiments with 2-butanol as OH radical scavenger showed that the reaction with OH radicals was responsible for 37% of the total α-pinene reacted and 39% of the total Δ3-carene reacted at the same settings. The scavenger experiments also showed that there were no significant amounts of OH radicals formed during the ozonolysis of limonene. The results from the designs were also compared to a mathematical model in order to evaluate further the data.
  • Gidhagen, Lars, et al. (författare)
  • Model simulation of ultrafine particles inside a road tunnel
  • 2003
  • Ingår i: Atmospheric Environment. - Elsevier. - 1352-2310. ; 37:15, s. 2023-2036
  • 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.
  • Hedberg, Emma, et al. (författare)
  • Chemical and physical characterization of emissions from birch wood combustion in a wood stove
  • 2002
  • Ingår i: Atmospheric Environment. - Elsevier. - 1352-2310. ; 36:30, s. 4823-4837
  • 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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