| 11. |
- Ketzel, M, et al.
(författare)
-
Particle and trace gas emission factors under urban driving conditions in Copenhagen based on street and roof-level observations
- 2003
-
Ingår i: Atmospheric Environment. - 1352-2310. ; 37:20, s. 2735-2749
-
Tidskriftsartikel (refereegranskat)abstract
- Simultaneous measurements of particle size distribution (size/range 10-700 nm) inside an urban street canyon and a nearby urban background location in Copenhagen in May-November 2001 were used to separate the traffic source contribution in the street canyon from the background levels. The background concentrations are highly variable due to changing contributions from long-range transport and local sources showing a diurnal pattern with a shift to smaller particle sizes during midday hours. The average ratio background/street concentration is 0.26 for NOx and 0.35, 0.42, 0.60, 0.64, respectively, for CO, total particle number (ToN), surface and volume. The particle size distribution of the traffic source shows during daytime and evening hours (6-24) a maximum at particle sizes of 20-30 nm independent of the changing heavy-duty vehicle share during the same time interval. The particle number concentration highly correlated (R > 0.83) with NOx through a wide range of particle sizes. The method of inverse modelling was applied to estimate average fleet emission factors typical of urban conditions in Denmark. Emission factors per average vehicle were estimated as (2.8 +/- 0.5) x 10(14) particles/km, (1.3 +/- 0.2) g NOx/(veh km) and (11 +/- 2) g CO/(veh km). We observe two types of 'nanoparticle events' (a) in background, probably due to photochemistry and (b) in the night hours when traffic is dominated by diesel taxis. During night hours (0-5), the maximum in the emitted particle size distribution, is shifted to smaller sizes of about 15-18 nm. This shift to smaller particle sizes is related to an increase in the average NOx and ToN emission per vehicle by a factor of 2-3 and a reduced CO emission also by a factor of 2-3. (C) 2003 Elsevier Science Ltd. All rights reserved.
|
|
| 12. |
- Martinsson, B. G., et al.
(författare)
-
Experimental determination of the connection between cloud droplet size and its dry residue size
- 1997
-
Ingår i: Atmospheric Environment. - 1352-2310. ; 31:16, s. 2477-2490
-
Tidskriftsartikel (refereegranskat)abstract
- The droplet activation process and droplet growth was studied during early stages of the formation of orographically-induced clouds. The experimental results were compared with the results obtained with a closed parcel, adiabatic cloud model. Good agreement was in most cases found between model and measurements with respect to cloud droplet number concentration, cloud droplet solute concentration and particle sizes scavenged due to cloud droplet nucleation. The experimental results were mainly obtained with a new instrument, the droplet aerosol analyser (DAA), which allows the determination of ambient sizes of cloud droplets and interstitial aerosol particles directly connected with the size of its dry residue in a two-parameter data acquisition. The resulting three-dimensional data set (ambient size, dry size, number concentration) was utilised to determine several cloud/aerosol properties, whereof some unique.
|
|
| 13. |
- Svenningsson, Birgitta, et al.
(författare)
-
Cloud droplet nucleation scavenging in relation to the size and hygroscopic behaviour of aerosol particles
- 1997
-
Ingår i: Atmospheric Environment. - 1352-2310. ; 31:16, s. 2463-2475
-
Tidskriftsartikel (refereegranskat)abstract
- The size distributions and hygroscopic growth spectra of aerosol particles were measured during the GCE cloud experiment at Great Dun Fell in the Pennine Hills in northern England. Hygroscopic growth is defined as the particle diameter at 90% RH divided by the particle diameter at 10% RH. The fraction of the aerosol particles scavenged by cloud droplets as a function of particle size was also measured. The general aerosol type was a mixture of marine and aged anthropogenic aerosols. The Aitken and accumulation mode numbers (average ± 1 S.D.) were 1543 ± 1078 and 1023 ± 682 cm-3, respectively. The mean diameters were in the range 30-100 nm and 100-330 nm. The hygroscopic growth spectra were bimodal about half the time. The less-hygroscopic particles had average growth factors of 1.06, 1.06; 1.03, 1.03, and 1.03 for particle diameters of 50, 75, 110, 165, and 265 nm, respectively. For the more-hygroscopic particles of the same sizes, the average hygroscopic growth was 1.34, 1.37, 1.43, 1.47, and 1.53. The effects of ageing on the aerosol particle size distribution and on hygroscopic behaviour are discussed. The scavenged fraction of aerosol particles was a strong function of particle diameter. The diameter with 50% scavenging was in the range 90-220 nm. No tail of smaller particles activated to cloud drops was observed. A small tail of larger particles that remained in the interstitial aerosol can be explained by there being a small fraction of less-hygroscopic particles. A weak correlation between the integral dry particle diameter and the diameter with 50% scavenging was seen.
|
|
| 14. |
- Swietlicki, Erik, et al.
(författare)
-
Source identification during the Great Dun Fell Cloud Experiment 1993
- 1997
-
Ingår i: Atmospheric Environment. - 1352-2310. ; 31:16, s. 2441-2451
-
Tidskriftsartikel (refereegranskat)abstract
- A characterisation of the sources influencing the site for the final field campaign of the EUROTRAC subproject GCE (Ground-based Cloud Experiment) at Great Dun Fell, Cumbria, Great Britain in April-May 1993 is presented. The sources were characterised mainly by means of aerosol filter and cascade impactor data, single particle analysis, gas data, data on aromatic organic compounds, cloud water ionic composition, measurements of aerosol size distributions and hygroscopic properties and various meteorological information. Receptor models applied on the aerosol filter and impactor data sets separately revealed two major source types being a marine sea spray source and a long-range transported anthropogenic pollution source. The results of the receptor models were largely consistent with the other observations used in the source identification. Periods of considerable anthropogenic pollution as well as almost pure marine air masses were clearly identified during the course of the experiment.
|
|
| 15. |
- Swietlicki, Erik, et al.
(författare)
-
Urban air pollution source apportionment using a combination of aerosol and gas monitoring techniques
- 1996
-
Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 30:15, s. 2795-2809
-
Tidskriftsartikel (refereegranskat)abstract
- The dominating local and regional sources of gaseous and particulate air pollution in the city of Lund (69,000 inhabitants) in southern Sweden were characterized using a combination of aerosol and gas-phase monitoring techniques. Twelve-hour samples were taken at two stations of both fine and coarse fraction urban aerosols with a stacked filter unit during the four-week measurement campaign in March/April 1993. The aerosol samples were analysed with PIXE for 14 major and trace elements. In addition, gaseous species (SO2, NO2, O-3) were measured simultaneously with the DOAS technique over two stretches, crossing each other only 300 m from the downtown aerosol sampling site. The combined results obtained by the analytical techniques PIXE and DOAS for aerosol and gas measurements, respectively, were used in an absolute receptor model in order to identify the major sources affecting the measurement sites and to apportion the measured air pollutants to the identified sources. The gases (SO2, NO2, O-3) could also be attributed to specific sources by combining the trace elemental concentration data for the fine fraction aerosol with that of the gaseous species in the receptor model. According to the absolute principal component analysis (APCA) model, the dominant sources for the measured species were resuspended road dust, automobile and diesel emissions, combustion of oil and coal, ferrous and non-ferrous smelters and sea spray. Of these, the sources related to traffic are mainly local in character while the others constitute a regional background. For a small city in southern Scandinavia like Lund with only light industry, the long-range transported air pollutants make up a significant part of the fine fraction aerosol. (C) 1996 Elsevier Science Ltd
|
|
| 16. |
- ter Schure, Arnout, et al.
(författare)
-
Polybrominated diphenyl ethers in precipitation in Southern Sweden (Skane, Lund)
- 2002
-
Ingår i: Atmospheric Environment. - 1352-2310. ; 36:25, s. 4015-4022
-
Tidskriftsartikel (refereegranskat)abstract
- The presence of polybrominated diphenyl ether (PBDE) flame retardants in total deposition (wet + dry) was assessed with the simultaneous use of three bulk samplers during a 2 week period. The particle associated and the 'dissolved' phase were separated during sampling. Volume weighted mean (VWM) concentrations of SigmaPBDE (9 congeners) in rain were 209 pg l(-1). Total deposition rates were 2 +/- 1 ng SigmaPBDE m(-2) day(-1). The total PBDE deposition was dominated by decaBDE(209) and thereafter 2,2'4,4'-tetraBDE(47) and 2,2'4,4',5-pentaBDE(99). Concentrations of particle associated and 'dissolved' PBDEs in total deposition were used to calculate filter/adsorbent ratios (F/A). We found that 65 +/- 18% of the total PBDEs were particle associated. Low F/A ratios for higher brominated congeners (Br > 5) were observed. This is contradictory with predictions based on the PBDEs' physico-chemical properties and was attributed to sampling artefacts, such as particle size distribution, and/or non-equilibrium processes. There was a negative relationship between the particulate SigmaPBDE concentration and rain volume suggesting a dilution effect and the importance of particle scavenging for wet deposition of PBDEs. (C) 2002 Elsevier Science Ltd. All rights reserved.
|
|
| 17. |
|
|
| 18. |
- Ekberg, Lars, 1962
(författare)
-
Volatile organic compounds in office buildings
- 1993
-
Ingår i: Atmospheric Environment. - 1873-2844 .- 1352-2310. ; 28:22, s. 3571-3575
-
Tidskriftsartikel (refereegranskat)abstract
- This paper concerns field measurements of volatile organic compounds (VOCs) in five office buildings. The buildings were selected to represent buildings without obvious problems with regard to the indoor air quality. The total concentrations of VOCs (TVOC) were measured using two different detection principles. Both short-term measurements and continuous monitoring were carried out. The results show that the use of continuous TVOC monitoring can provide valuable information in addition to the results obtained by sampling. The indoor TVOC concentrations obtained by gas chromatography ranged from 0.16 to 0.35 mgm−3. The indoor-outdoor TVOC concentration difference obtained by photoacoustic spectroscopy was about twice as high during working hours as during the night time. Furthermore, it is indicated that VOCs in indoor environments do not only originate from construction materials and other internal sources. Outdoor sources can also have a substantial influence on the indoor VOC concentrations.
|
|
| 19. |
- 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 .- 1873-2844. ; 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.
|
|
| 20. |
|
|
