| 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. |
- 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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| 3. |
- ter Schure, Arnout, et al.
(författare)
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Polybrominated diphenyl ethers in precipitation in Southern Sweden (Skane, Lund)
- 2002
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Ingår i: Atmospheric Environment. - 1352-2310. ; 36:25, s. 4015-4022
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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.
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| 4. |
- Fick, Jerker, et al.
(författare)
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A study of the gas-phase ozonolysis of terpenes: the impact of radicals formed during the reaction
- 2002
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Ingår i: Atmospheric Environment. - 1352-2310 .- 1873-2844. ; 36:20, s. 3299-3308
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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.
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| 5. |
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| 6. |
- Molnár, Peter, 1967, et al.
(författare)
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Roadside measurements of fine and ultrafine particles at a major road north of Gothenburg
- 2002
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Ingår i: Atmospheric Environment. - 1352-2310 .- 1873-2844. ; 36:25, s. 4115-4123
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Tidskriftsartikel (refereegranskat)abstract
- Particle measurements were conducted at a road site 15 km north of the city of Gothenburg for 3 weeks in June 2000. The size distribution between 10 and 368 nm was measured continuously by using a differential mobility particle sizer (DMPS) system. PM2.5 was sampled on a daily basis with subsequent elemental analysis using EDXRF-spectroscopy. The road is a straight four-lane road with a speed limit of 90 kph. The road passing the site is flat with no elevations where the vehicles run on a steady workload and with constant speed. The traffic intensity is about 20,000 cars per workday and 13,000 vehicles per day during weekends. The diesel fuel used in Sweden is low in sulphur content (< 10 ppm) and therefore the diesel vehicles passing the site contribute less to particle emissions in comparison with other studies. A correlation between PM2.5 and accumulation mode particles (100-368 nm) was observed. However, no significant correlation was found between number concentrations of ultrafine particles (10-100 nm) and PM2.5 or the accumulation mode number concentration. The particle distribution between 10 and 368 nm showed great dependency on wind speed and wind direction, where the wind speed was the dominant factor for ultrafine (10-100nm) particle concentrations. The difference in traffic intensity between workday and weekend together with wind data made it possible to single out the traffic contribution to particle emissions and measure the size distribution. The results presented in combination with previous studies show that both PM2.5 and the mass of accumulation mode particles are bad estimates for ultrafine particles. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 7. |
- Pommer, Linda, et al.
(författare)
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Development of a NO2 scrubber for accurate sampling of ambient levels of terpenes
- 2002
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Ingår i: Atmospheric Environment. - 1352-2310 .- 1873-2844. ; 36:9, s. 1443-1452
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Tidskriftsartikel (refereegranskat)abstract
- The result of pumping air containing 56 ppb NO2 through a terpene-spiked adsorbent (90–130 ng, 90–100 ml min−1), Tenax TA, for 20 min (1.8–2.0 l) was that 8% of α-pinene, 7% of β-pinene, 21% of Δ3-carene and 5% of limonene were oxidised. In similar experiments with air containing 56 ppb O3, 3% of α-pinene, 4% of β-pinene, 10% of Δ3-carene and 38% of limonene were oxidised. Sampling a mixture of a terpene and NO2 using Tenax TA can give unwanted overestimation of the amount of reaction products from the terpene–NO2 reaction or underestimation of the original terpene levels. A scrubber was needed to reduce the problems caused by interfering reactions on the adsorbent of NO2 and to reduce discrimination of reactive compounds due to their relatively fast decay on the adsorbent. Several chemicals have been tested for their ability of removing NO2 and our objective was to develop a well functioning, reusable, easy to handle, easy manufactured NO2 scrubber. The result of the experiments was a scrubber consisting of two glass fibre filters coated with Na2SO3 assembled in a dust collector. The recovery of the terpenes through the scrubber varied between 75% and 97% at 15–75% relative humidity, and the scrubber is a one-use scrubber due to memory effects. The Na2SO3 scrubber could be stored in room air for at least one month without loosing the capacity of removing NO2.
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