| 1. |
- 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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| 2. |
- 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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| 3. |
- Wingfors, Håkan, et al.
(författare)
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Characterisation and determination of profiles of polycyclic aromatic hydrocarbons in a traffic tunnel in Gothenburg, Sweden
- 2001
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Ingår i: Atmospheric Environment. - 1352-2310 .- 1873-2844. ; 35:36, s. 6361-6369
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Tidskriftsartikel (refereegranskat)abstract
- The concentrations of semi-volatile polycyclic aromatic hydrocarbons (PAHs), hydrocarbons (HCs), particulate matter (PM 1, 2.5 and 10 μm) and total suspended particles (TSPs) were measured in a traffic tunnel in Gothenburg, Sweden. Emission factors (EFs) were also calculated. These variables are assumed to provide good estimates of average vehicle emissions, since all types of vehicle, using all types of fuel, pass through this tunnel. It was shown that the majority of particle-associated PAHs were found on particles with an aerodynamic diameter of <1 μm. The concentrations of PAHs were one order higher in magnitude in air samples from the tunnel than in air samples at two urban locations. However, the PAH profiles of air samples from the tunnel and the urban sites were similar. This was demonstrated using principal component analysis (PCA). Finally, and notably, there was no significant change in the total emissions when the proportion of heavy-duty vehicles (HDVs) increased from 8% to 24%. Previously, diesel vehicles had been found to release larger quantities of PAHs and related substances. Advances in fuel quality, and HDV motor and exhaust system design during the last decade may have contributed to this promising result. However, it was shown, using partial least squares regression to latent structures (PLS), that some of the parameters measured displayed correlations with the proportions of HDVs and light-duty vehicles (LDVs). Concentrations of total HCs, TSPs, dibenzothiopene, phenantrene, anthracene and monomethyl-derivatives of phenantrene and anthracene were all correlated to the proportion of HDVs. The concentrations of naphthalene, some mono- and dimethylnaphthalenes and most large PAHs (with 5–7 fused rings) were correlated to the proportion of LDVs.
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| 4. |
- Fick, Jerker, et al.
(författare)
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Formation of oxidation products in a ventilation system
- 2004
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 38:35, s. 5895-9
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the formation of oxidation products from the ozonolysis of a monoterpene (α-pinene) in an authentic ventilation system. We observed ten products, norpinic acid, pinic acid, glyoxal, methyl glyoxal, norpinonic acid, pinonic acid, a C4 dicarbonyl (C4H6O2), a C5 dicarbonyl (C5H8O2), norpinon aldehyde, and pinon aldehyde. Experiments were conducted at a low (2.0 g m−3) and moderate (8 g m−3) humidity levels. All products but C4 dicarbonyl and norpinon aldehyde were detected at the low humidity level, but only glyoxal, methyl glyoxal, C4 dicarbonyl, norpinon aldehyde and pinon aldehyde were detected at a moderate humidity. Experiments were conducted at low ppb levels (75 ppb ozone and 4 and 10 ppb α-pinene) and with a short reaction time (75 s). Experiments showed that 5–6% of the α-pinene reacted, which was approximately 4–5 times more than predicted by theoretical calculations. This discrepancy suggests a significant contribution from heterogeneous reactions. These oxidation products were formed despite low reactant concentrations and a short reaction time, indicating that the formation of oxidation products likely occurs at ambient levels and in real settings.
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| 5. |
- Hazenkamp-Von Arx, M.E., et al.
(författare)
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PM2.5 and NO2 assessment in 21 European study centres of ECRHS II : annual means and seasonal differences
- 2004
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Ingår i: Atmospheric Environment. - : Elsevier. - 1352-2310 .- 1873-2844. ; 38:13, s. 1943-1953
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Tidskriftsartikel (refereegranskat)abstract
- The follow-up of cohorts of adults from more than 20 European centres of the former ECRHS I (1989-1992) investigates long-term effects of exposure to ambient air pollution on respiratory health, in particular asthma and change of pulmonary function. Since PM2.5 is not routinely monitored in Europe, we measured PM2.5 concentrations in 21 participating centres to estimate 'background' exposure in these cities. Winter (November-February), summer (May-August) and annual mean (all months) values of PM2.5 were determined from measuring periods between June 2000 and November 2001. Sampling was conducted for 7 days per month for a year. Annual and winter mean concentrations of PM2.5 vary substantially being lowest in Iceland and highest in centres in Northern Italy. Annual mean concentrations ranged from 3.7 to 44.9 mug m(-3), winter mean concentrations from 4.8 to 69.2 mug m(-3), and summer mean concentrations from 3.3 to 23.1 mugm(-3). Seasonal variability occurred but did not follow the same pattern across all centres. Therefore, ranking of centres varied from summer to winter. Simultaneously, NO2 concentrations were measured using passive sampling tubes. Annual mean NO2 concentrations range from 4.9 to 72.1 mug m(-3) with similar seasonal variations across centres and constant ranking of centres between seasons. The correlation between annual NO2 and PM2.5 concentrations is fair (Spearman correlation coefficient r(s) = 0.75), but when considered as monthly means the correlation is far less consistent and varies substantially between centres. The range of PM2.5 mass concentrations obtained in ECRHS II is larger than in other current cohort studies on long-term effects of air pollution. This substantial variation in PM2.5 exposure will improve statistical power in future multilevel health analyses and to some degree may compensate for the lack of information on within-city variability. Seasonal means may be used to indicate potential differences in the toxicity across the year. Across ECRHS cities annual NO2 might serve as a surrogate for PM2.5, especially for past exposure assessment, when PM2.5 is not available.
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