| 1. |
- Burman, Jan, et al.
(author)
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Issues when linking computational fluid dynamics for urban modeling to toxic load models : The need for further research
- 2015
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 104, s. 112-124
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Journal article (peer-reviewed)abstract
- In order to predict casualties caused by chemical hazards in densely populated areas, state-of-the-art Computational Fluid Dynamic (CFD) techniques could be utilized together with toxic load models. In the current study, simulations of consequences of hypothetical releases of toxic gas in a city center are presented and discussed. CFD models that reproduce flow statistics would be most appropriate for this purpose since it could be expected that they will more realistically represent the environment. However, since concentration-peaks in the ever-present spatiotemporal fluctuations of airborne chemicals contribute so much to the toxic load, it is shown that straight-forward direct linking of a CFD model to a toxic load model is not a suitable approach for predicting consequences of a toxic release. Furthermore, it is demonstrated that the use of different turbulence models leads to different casualty assessments. Obviously, there is an urgent need to establish widely accepted methods, ideally with known uncertainty measures. Thus, further research in this area is of great importance.
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| 2. |
- Carlsen, Hanne Krage, et al.
(author)
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Indicators of residential traffic exposure: Modelled NOX, traffic proximity, and self-reported exposure in RHINE III
- 2017
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 167, s. 416-425
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Journal article (peer-reviewed)abstract
- Few studies have investigated associations between self-reported and modelled exposure to traffic pollution. The objective of this study was to examine correlations between self-reported traffic exposure and modelled (a) NOX and (b) traffic proximity in seven different northern European cities; Aarhus (Denmark), Bergen (Norway), Gothenburg, Umeå, and Uppsala (Sweden), Reykjavik (Iceland), and Tartu (Estonia). We analysed data from the RHINE III (Respiratory Health in Northern Europe, www.rhine.nu) cohorts of the seven study cities. Traffic proximity (distance to the nearest road with >10,000 vehicles per day) was calculated and vehicle exhaust (NOX) was modelled using dispersion models and land-use regression (LUR) data from 2011. Participants were asked a question about self-reported traffic intensity near bedroom window and another about traffic noise exposure at the residence. The data were analysed using rank correlation (Kendall's tau) and inter-rater agreement (Cohen's Kappa) between tertiles of modelled NOX and traffic proximity tertile and traffic proximity categories (0–150 metres (m), 150–200 m, >300 m) in each centre. Data on variables of interest were available for 50–99% of study participants per each cohort. Mean modelled NOX levels were between 6.5 and 16.0 μg/m3; median traffic intensity was between 303 and 10,750 m in each centre. In each centre, 7.7–18.7% of respondents reported exposure to high traffic intensity and 3.6–16.3% of respondents reported high exposure to traffic noise. Self-reported residential traffic exposure had low or no correlation with modelled exposure and traffic proximity in all centres, although results were statistically significant (tau = 0.057–0.305). Self-reported residential traffic noise correlated weakly (tau = 0.090–0.255), with modelled exposure in all centres except Reykjavik. Modelled NOX had the highest correlations between self-reported and modelled traffic exposure in five of seven centres, traffic noise exposure had the highest correlation with traffic proximity in tertiles in three centres. Self-reported exposure to high traffic intensity and traffic noise at each participant's residence had low or weak although statistically significant correlations with modelled vehicle exhaust pollution levels and traffic proximity. © 2017
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| 3. |
- Deng, Qihong, et al.
(author)
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Association between prenatal exposure to industrial air pollution and onset of early childhood ear infection in China
- 2017
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In: Atmospheric Environment. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1352-2310 .- 1873-2844. ; 157, s. 18-26
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Journal article (peer-reviewed)abstract
- Background: Otitis media (OM) is a common infection in early childhood with repeated attacks that lead to long-term complications and sequelae, but its etiology still remains unclear. Objective: To examine the association between early life exposure to air pollution and childhood OM, with the purpose of identifying critical windows of exposure and key components of air pollution in the development of OM. Methods: We conducted a prospective cohort study of 1617 children aged 3-4 years in Changsha, China (2011-2012). The prevalence of OM was assessed by a questionnaire administered by the parents. Individual exposures to nitrogen dioxide (NO2), sulfur dioxide (SO2) and particulate matter with an aerodynamic diameter <= 10 gm (PM10) during prenatal, postnatal, and current windows were estimated using the measured concentrations at monitoring stations. We used logistic regression model to examine the OM risk in terms of odds ratio (OR) and 95% confidence interval (CI) for exposure to different air pollutants during different timing windows, adjusting for covariates, multi-pollutants, and multi windows. Results: Life-time prevalence of doctor-diagnosed OM in preschool children in Changsha was 7.3%. Childhood OM was associated only with prenatal exposure to the industrial air pollution with adjusted OR (95% CI) = 1.44 (1.09-1.88) for a 27 g/m(3) increase in SO2, particularly during the first trimester of pregnancy. We further found that prenatal SO2 exposure was not associated with the repeated attacks but was associated with the onset of OM, adjusted OR (95% CI) = 1.47 (1.10-1.96). The association between prenatal SO2 exposure and early childhood OM was robust after adjusting for other pollutants and windows. Sensitivity analysis indicated that the association was stronger in females, children with parental atopy, and children living in houses with cockroaches, new redecoration, and condensation on window pane during winter. Conclusion: We provide new evidence that prenatal exposure to industrial air pollution is associated with early childhood OM in China and may contribute to the onset of childhood OM. Our findings are helpful in developing more effective preventative strategies for childhood OM. (C) 2017 Elsevier Ltd. All rights reserved.
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| 4. |
- Dingwell, Adam, et al.
(author)
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Seasonal and diurnal patterns in the dispersion of SO2 from Mt. Nyiragongo
- 2016
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In: Atmospheric Environment. - : Elsevier BV. - 1873-2844 .- 1352-2310. ; 132, s. 19-29
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Journal article (peer-reviewed)abstract
- Mt. Nyiragongo is an active volcano located in the Democratic Republic of Congo, close to the border of Rwanda and about 15 km north of the city of Goma (~ 1,000,000 inhabitants). Gases emitted from Nyiragongo might pose a persistent hazard to local inhabitants and the environment. While both ground- and satellite-based observations of the emissions exist, prior to this study, no detailed analysis of the dispersion of the emissions have been made. We have conducted a dispersion study, using a modelling system to determine the geographical distribution of SO2.A combination of a meteorological model (WRF), a Lagrangian particle dispersion model (FLEXPART-WRF) and flux data based on DOAS measurements from the NOVAC-network is used. Since observations can only be made during the day, we use random sampling of fluxes and ensemble modelling to estimate night-time emissions.Seasonal variations in the dispersion follows the migration of the Inter Tropical Convergence Zone. In June-August, the area with the highest surface concentrations is located to the northwest, and in December-February, to the southwest of the source. Diurnal variations in surface concentrations were determined by the development of the planetary boundary layer and the lake-/land breeze cycle around lake Kivu. Both processes contribute to low surface concentrations during the day and high concentrations during the night. However, the strong northerly trade winds in November-March weakened the lake breeze, contributing to higher daytime surface concentrations along the northern shore of Lake Kivu, including the city of Goma. For further analysis and measurements, it is important to include both seasonal and diurnal cycles in order to safely cover periods of high and potentially hazardous concentrations.
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| 5. |
- ENGER, L, et al.
(author)
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SIMULATIONS OF DISPERSION IN COMPLEX TERRAIN USING A HIGHER-ORDER CLOSURE-MODEL
- 1995
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In: ATMOSPHERIC ENVIRONMENT. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1352-2310. ; 29:18, s. 2449-2465
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Journal article (peer-reviewed)abstract
- A three-dimensional higher-order closure dispersion model is used to simulate dispersion from an elevated point source in an area with complex terrain in the Colorado River Valley (southwestern U.S.). The central part of the domain is characterized by th
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| 6. |
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| 7. |
- Isaxon, Christina, et al.
(author)
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Contribution of indoor-generated particles to residential exposure
- 2015
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 106, s. 458-466
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Journal article (peer-reviewed)abstract
- The majority of airborne particles in residences, when expressed as number concentrations, are generated by the residents themselves, through combustion/thermal related activities. These particles have a considerably smaller diameter than 2.5 mu m and, due to the combination of their small size, chemical composition (e.g. soot) and intermittently very high concentrations, should be regarded as having potential to cause adverse health effects. In this study, time resolved airborne particle measurements were conducted for seven consecutive days in 22 randomly selected homes in the urban area of Lund in southern Sweden. The main purpose of the study was to analyze the influence of human activities on the concentration of particles in indoor air. Focus was on number concentrations of particles with diameters <300 nm generated by indoor activities, and how these contribute to the integrated daily residential exposure. Correlations between these particles and soot mass concentration in total dust were also investigated. It was found that candle burning and activities related to cooking (using a frying pan, oven, toaster, and their combinations) were the major particle sources. The frequency of occurrence of a given concentration indoors and outdoors was compared for ultrafine particles. Indoor data was sorted into non-occupancy and occupancy time, and the occupancy time was further divided into non-activity and activity influenced time. It was found that high levels (above 10(4) cm(-3)) indoors mainly occur during active periods of occupancy, while the concentration during non-activity influenced time differs very little from non-occupancy time. Total integrated daily residential exposure of ultrafine particles was calculated for 22 homes, the contribution from known activities was 66%, from unknown activities 20%, and from background/non-activity 14%. The collected data also allowed for estimates of particle source strengths for specific activities, and for some activities it was possible to estimate correlations between the number concentration of ultrafine particles and the mass concentration of soot in total dust in 10 homes. Particle source strengths (for 7 specific activities) ranged from 1.6.10(12) to 4.5.10(12) min(-1). The correlation between ultrafine particles and mass concentration of soot in total dust varied between 0.37 and 0.85, with an average of 0.56 (Pearson correlation coefficient). This study clearly shows that due to the importance of indoor sources, residential exposure to ultrafine particles cannot be characterized by ambient measurements alone. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).
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| 8. |
- Jones, Stephanie H., et al.
(author)
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Are organic films from atmospheric aerosol and sea water inert to oxidation by ozone at the air-water interface?
- 2017
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In: Atmospheric Environment. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1352-2310 .- 1873-2844. ; 161, s. 274-287
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Journal article (peer-reviewed)abstract
- The heterogeneous oxidation of thin films of organic material extracted from real aerosol and sea-water samples was studied at the air-water interface using X-ray reflectivity. Oxidation of thin films of organic material extracted from real aerosol and sea-water is important in further understanding the impact of coated aerosols on the climate of the Earth. Surface active insoluble organic material extracted from the atmosphere was found to form stable films at the air-water interface (thickness measured as 10-14 nm). On exposure of the films to gas-phase ozone, no reaction (or change in the relative scattering length of the interface) was observed, indicating a potential lack of unsaturated organic material in the samples. Gas chromatography and electrospray ionization mass spectrometry showed the presence of saturated compounds in the samples. It is therefore proposed that the amount of unsaturated compounds as compared to saturated compounds in the atmospheric material is so low that the mass spectrometry analyses, as well as gas-phase oxidation are dominated by saturated material. A reaction was observed on exposure of the same films to aqueous phase hydroxyl and nitrate radicals and a film thinning mechanism is proposed to explain the change in scattering length of the film at the air-water interface. It can be suggested tentatively that oxidation by gas-phase ozone is not important in the atmosphere for organic films on aqueous atmospheric aerosol and that further studies should focus on radical induced oxidation of saturated organic material instead of unsaturated proxies that are typically studied.
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| 9. |
- King, M D, et al.
(author)
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Interaction of nitrogen dioxide (NO2) with a monolayer of oleic acid at the air-water interface - A simple proxy for atmospheric aerosol
- 2010
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 44:14, s. 1822-1825
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Journal article (peer-reviewed)abstract
- The reactions between atmospheric oxidants and organic amphiphiles at the air water interface of an aerosol droplet may affect the size and critical supersaturation required for cloud droplet formation. We demonstrate that no reaction occurs between gaseous nitrogen dioxide (1000 ppm in air) and a monolayer of an insoluble amphiphile, oleic acid (cis-9-octadecenoic acid), at the air water interface which removes material from the air water interface. We present evidence that the NO2 isomerises the cis-9-octadecenoic (oleic) acid to trans-9-octadecenoic (elaidic) acid. The study presented here is important for future and previous studies of (1) the reaction between the nitrate radical, NO3, and thin organic films as NO2 is usually present in high concentrations in these experimental systems and (2) the effect of NO2 air pollution on the unsaturated fatty acids and lipids found at the air liquid surface of human lung lining fluid.
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| 10. |
- Kulan, Abdulhadi, et al.
(author)
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Distribution of 7Be in surface air of Europe
- 2006
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 40:21, s. 3855-3868
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Journal article (peer-reviewed)abstract
- This study deals with long-term (span over three decades, 1972-2003) distribution of the cosmogenic isotope Be-7 in surface air at 5 stations in Europe, extending from latitude 47 degrees N to 68 degrees N. The results suggest annual variability in all the data sets as well as a decrease in average Be-7 activity with increasing latitude. Furthermore, a 9-10-year cyclical pattern is observed in the Be-7 distribution, which is anticorrelated with the solar activity cycle. Our data also indicate a dynamic range of Be-7 activity for each solar cycle and phase (maximum or minimum) which is higher at the middle compared to high-latitude regions. Additionally, about 10-20% relative deviation is observed in Be-7 activity during solar maxima and minima compared to the total average Be-7. This feature indicates that some deviation in the worldwide Be-7 activity data may relate to their acquisition, with respect to which part of a solar cycle they have been collected in (time span) and at which latitudinal spread. Estimate of Be-7 flux onto European surface boundary layer vary from 0.4 to 0.9 x 10(10) atoms m(-2) yr(-1) which is strongly latitude dependent and our average value is comparable to the similar to 0.7-0.8 x 10(10) atoms m(-2) yr(-1) across ocean and land.
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