| 1. |
- Beelen, Rob, et al.
(author)
-
Development of NO2 and NOx land use regression models for estimating air pollution exposure in 36 study areas in Europe : the ESCAPE project
- 2013
-
In: Atmospheric Environment. - : Elsevier. - 1352-2310 .- 1873-2844. ; 72, s. 10-23
-
Journal article (peer-reviewed)abstract
- Estimating within-city variability in air pollution concentrations is important. Land use regression (LUR) models are able to explain such small-scale within-city variations. Transparency in LUR model development methods is important to facilitate comparison of methods between different studies. We therefore developed LUR models in a standardized way in 36 study areas in Europe for the ESCAPE (European Study of Cohorts for Air Pollution Effects) project.Nitrogen dioxide (NO2) and nitrogen oxides (NOx) were measured with Ogawa passive samplers at 40 or 80 sites in each of the 36 study areas. The spatial variation in each area was explained by LUR modeling. Centrally and locally available Geographic Information System (GIS) variables were used as potential predictors. A leave-one out cross-validation procedure was used to evaluate the model performance.There was substantial contrast in annual average NO2 and NOx concentrations within the study areas. The model explained variances (R2) of the LUR models ranged from 55% to 92% (median 82%) for NO2 and from 49% to 91% (median 78%) for NOx. For most areas the cross-validation R2 was less than 10% lower than the model R2. Small-scale traffic and population/household density were the most common predictors. The magnitude of the explained variance depended on the contrast in measured concentrations as well as availability of GIS predictors, especially traffic intensity data were important. In an additional evaluation, models in which local traffic intensity was not offered had 10% lower R2 compared to models in the same areas in which these variables were offered.Within the ESCAPE project it was possible to develop LUR models that explained a large fraction of the spatial variance in measured annual average NO2 and NOx concentrations. These LUR models are being used to estimate outdoor concentrations at the home addresses of participants in over 30 cohort studies.
|
|
| 2. |
- Denby, Bruce Rolstad, et al.
(author)
-
A coupled road dust and surface moisture model to predict non-exhaust road traffic induced particle emissions (NORTRIP). Part 1 : Road dust loading and suspension modelling
- 2013
-
In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 77, s. 283-300
-
Journal article (peer-reviewed)abstract
- Non-exhaust traffic induced emissions are a major source of particle mass in most European countries. This is particularly important in Nordic and Alpine countries where winter time road traction maintenance occurs, e.g. salting and sanding, and where studded tyres are used. In this paper, Part 1, the road dust sub-model of a coupled road dust and surface moisture model (NORTRIP) is described. The model provides a generalised process based formulation of the non-exhaust emissions, with emphasis on the contribution of road wear, suspension, surface dust loading and the effect of road surface moisture (retention of wear particles and suspended emissions). The model is intended for use as a tool for air quality managers to help study the impact of mitigation measures and policies. We present a description of the road dust sub-model and apply the model to two sites in Stockholm and Copenhagen where seven years of data with surface moisture measurements are available. For the site in Stockholm, where studded tyres are in use, the model predicts the PM10 concentrations very well with correlations (R-2) in the range of R-2 = 0.76-0.91 for daily mean PM10. The model also reproduces well the impact of a reduction in studded tyres at this site. For the site in Copenhagen the correlation is lower, in the range 0.44-0.51. The addition of salt is described in the model and at both sites this leads to improved correlations due to additional salt emissions. For future use of the model a number of model parameters, e.g. wear factors and suspension rates, still need to be refined. The effect of sanding on PM10 emissions is also presented but more information will be required before this can be confidently applied for management applications. (C) 2013 Elsevier Ltd. All rights reserved.
|
|
| 3. |
- Denby, Bruce Rolstad, et al.
(author)
-
A coupled road dust and surface moisture model to predict non-exhaust road traffic induced particle emissions (NORTRIP). Part 2 : Surface moisture and salt impact modelling
- 2013
-
In: Atmospheric Environment. - : Elsevier. - 1352-2310 .- 1873-2844. ; 81, s. 485-503
-
Journal article (peer-reviewed)abstract
- Non-exhaust traffic induced emissions are a major source of airborne particulate matter in most European countries. This is particularly important in Nordic and Alpine countries where winter time road traction maintenance occurs, e.g. salting and sanding, and where studded tyres are used. Though the total mass generated by wear sources is a key factor in non-exhaust emissions, these emissions are also strongly controlled by surface moisture conditions. In this paper, Part 2, the road surface moisture submodel of a coupled road dust and surface moisture model (NORTRIP) is described.We present a description of the road surface moisture part of the model and apply the coupled model to seven sites in Stockholm, Oslo, Helsinki and Copenhagen over 18 separate periods, ranging from 3.5 to 24 months. At two sites surface moisture measurements are available and the moisture sub-model is compared directly to these observations. The model predicts the frequency of wet roads well at both sites, with an average fractional bias of -2.6%. The model is found to correctly predict the hourly surface state, wet or dry, 85% of the time. From the 18 periods modelled using the coupled model an average absolute fractional bias of 15% for PM10 concentrations was found. Similarly the model predicts the 90'th daily mean percentiles of PMio with an average absolute bias of 19% and an average correlation (R-2) of 0.49. When surface moisture is not included in the modelling then this average correlation is reduced to 0.16, demonstrating the importance of the surface moisture conditions. Tests have been carried out to assess the sensitivity of the model to model parameters and input data. The model provides a useful tool for air quality management and for improving our understanding of non-exhaust traffic emissions.
|
|
| 4. |
- Fischer, Andreas, et al.
(author)
-
Ozone removal by occupants in a classroom
- 2013
-
In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 81, s. 11-17
-
Journal article (peer-reviewed)abstract
- Ozone concentrations were measured in a classroom with and without occupants, with the purpose to quantify effects on indoor O3 concentrations. The teacher and 24 11-year old pupils each removed O3 at a rate, first order in O3, corresponding to a rate constant of (2.5±0.6)×10-5s-1 in the present locality and to a deposition velocity of 0.45cms-1. The O3-removal caused by the occupants was approximately 2.6 times larger than that of the available surfaces belonging to the classroom and its furniture. Observation of 6-methyl-5-hepten-2-one and 4-oxopentanal at maximum concentrations of 0.2ppb and 0.7ppb, respectively, suggested squalene from human skin oil as a reactive, ozone-consuming substance. There are indications of a source of 4-oxopentanal in the classroom, even some time after the pupils left for the day. The work presented is important for a proper description of indoor exposure, both to ozone itself and some of its reaction products when trying to quantify relations between exposure and health effects.
|
|
| 5. |
- Hung, Hayley, et al.
(author)
-
Toward the next generation of air quality monitoring : Persistent organic pollutants
- 2013
-
In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 80, s. 591-598
-
Journal article (peer-reviewed)abstract
- Persistent Organic Pollutants (POPs) are global pollutants that can migrate over long distances and bioaccumulate through food webs, posing health risks to wildlife and humans. Multilateral environmental agreements, such as the Stockholm Convention on POPs, were enacted to identify POPs and establish the conditions to control their release, production and use. A Global Monitoring Plan was initiated under the Stockholm Convention calling for POP monitoring in air as a core medium; however long temporal trends (>10 years) of atmospheric POPs are only available at a few selected sites. Spatial coverage of air monitoring for POPs has recently significantly improved with the introduction and advancement of passive air samplers. Here, we review the status of air monitoring and modeling activities and note major uncertainties in data comparability, deficiencies of air monitoring and modeling in urban and alpine areas, and lack of emission inventories for most POPs. A vision for an internationally-integrated strategic monitoring plan is proposed which could provide consistent and comparable monitoring data for POPs supported and supplemented by global and regional transport models. Key recommendations include developing expertise in all aspects of air monitoring to ensure data comparability and consistency; partnering with existing air quality and meteorological networks to leverage synergies; facilitating data sharing with international data archives; and expanding spatial coverage with passive air samplers. Enhancing research on the stability of particle-bound chemicals is needed to assess exposure and deposition in urban areas, and to elucidate long-range transport. Conducting targeted measurement campaigns in specific source areas would enhance regional models which can be extrapolated to similar regions to estimate emissions. Ultimately, reverse-modeling combined with air measurements can be used to derive “emission” as an indicator to assess environmental performance with respect to POPs on the country, region, or global level.
|
|
| 6. |
- Kierkegaard, Amelie, et al.
(author)
-
Determination of linear and cyclic volatile methylsiloxanes in air at a regional background site in Sweden
- 2013
-
In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 80, s. 322-329
-
Journal article (peer-reviewed)abstract
- A number of volatile methylsiloxanes have been identified as environmental contaminants and several are currently the subject of detailed risk assessments due to concerns that they may be persistent, bioaccumulative and toxic in the environment. Once emitted these chemicals reside primarily in the atmosphere. Consequently, knowledge of their concentrations in air is essential to understanding their fate in the environment and any potential adverse impacts. We developed a method to analyse 4 cyclic volatile methylsiloxanes (D3, D4, D5 and D6) and 4 linear volatile methylsiloxanes (L3, L4, L5 and L6) in air at regional background levels. The method showed good repeatability (median difference between sample pairs of 2-8%) and low limits of quantification (from 3.8 pg m(-3) for L3 to 320 pg m(-3) for D4). However, the analysis of D3 and D4 was confounded by the transformation of D5 to these analytes on the sampling cartridge. During a sampling campaign with a daily temporal resolution between November 4 and December 14 2011, all analytes with the exception of L5 and L6 could be quantified in all samples. It was hypothesized that the ratio of the concentrations of different VMS reflected the relative strength of their emissions to the airshed due to the slow phototransformation of the VMS at high latitudes in winter. This was supported by available emissions information.
|
|
| 7. |
- Lundin, Lisa, et al.
(author)
-
The effect of developing nations' municipal waste composition on PCDD/PCDF emissions from open burning
- 2013
-
In: Atmospheric Environment. - : Elsevier. - 1352-2310 .- 1873-2844. ; 79, s. 433-441
-
Journal article (peer-reviewed)abstract
- Open burning tests of municipal waste from two countries, Mexico and China, showed composition-related differences in emissions of polychlorinated dibenzodioxins and dibenzofurans (PCDDs/PCDFs). Twenty-six burn tests were conducted, comparing results from two laboratory combustion facilities. Waste was shredded to isolate composition-specific effects from those due to random waste orientation. Emissions ranged from 5 to 780 ng toxic equivalent/kg carbon burned (ng TEQ (kg C-b)(-1)) with an average of 140 ng TEQ (kg C-b)(-1) (stdev = 170). The waste from Mexico (17 ng TEQ (kg C-b)(-1)) had a statistically lower average emission factor than waste from China (240 ng TEQ (kg C-b)(-1). This difference was attributed primarily to waste composition differences, although one time-integrated combustion quality measure, Delta CO/Delta CO2, showed statistical significance between laboratories. However, waste composition differences were far more determinant than which laboratory conducted the tests, illustrated using both statistical techniques and comparison of cross-over samples (wastes tested at both facilities). Comparison of emissions from previous waste combustion tests in Sweden and the U.S.A, showed emission factors within the range of those determined for Mexico and China waste. For laboratory-scale combustion, existing emission factors and test methodologies are generally applicable to both developed and developing countries.
|
|
| 8. |
- Rivera, Claudia, 1976, et al.
(author)
-
NO2 fluxes from Tijuana using a mobile mini-DOAS during Cal-Mex 2010
- 2013
-
In: Atmospheric Environment. - : Elsevier BV. - 1873-2844 .- 1352-2310. ; 70, s. 532-539
-
Journal article (peer-reviewed)abstract
- NO2 fluxes were measured using a mobile mini-DOAS during Cal-Mex 2010 field study, between May 15 and June 30, 2010, from the urban area of Tijuana, Baja California as well as the Rosarito power plant The average calculated NO2 fluxes were 328 +/- 184 (269 +/- 201) g s(-1), and 23.4 +/- 4.9 (12.9 +/- 11.9) g s(-1) for Tijuana urban area and Rosarito power plant, respectively, using model based wind fields and onsite measurements (in parenthesis). Wind speed and wind direction data needed to estimate the fluxes were both modeled and obtained from radiosondes launched regularly during the field campaign, whereas the mixing layer height throughout the entire field campaign was measured using a ceilometer. Large variations in the NO2 fluxes from both the Tijuana urban area and Rosarito power plant were observed during Cal-Mex 2010; however, the variability was less when model based wind fields were used. Qualitative comparisons of modeled and measured plumes from the Tijuana urban area and Rosarito power plant showed good agreement.
|
|
| 9. |
- Heimdal Nilsson, Elna, et al.
(author)
-
Re-evaluation of the reaction rate coefficient of CH3Br + OH with implications for the atmospheric budget of methyl bromide
- 2013
-
In: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 80, s. 70-74
-
Journal article (peer-reviewed)abstract
- The reaction rate coefficient k(CH3Br + OH) has been determined in the temperature range 298-373 K, using pulse radiolysis/UV kinetic spectroscopy, and at 298 K using a relative rate method. The Arrhenius expression obtained from a fit to the experimental results is (2.9 +/- 0.9) x 10(-12) exp(-(1230 +/- 125)/T) cm(3) molecule(-1) s(-1), which is greater than the expression currently recommended. The relative rate experiments give k(298 K) = (4.13 +/- 0.63) x 10(-14) cm(3) molecule(-1) s(-1). The results of the absolute and relative rate experiments indicate that the source budget of atmospheric CH3Br should be reinvestigated, as was recently done for CH3Cl. (C) 2013 Elsevier Ltd. All rights reserved.
|
|
| 10. |
- Hertel, Ole, et al.
(author)
-
Assessing atmospheric nitrogen deposition to natural and semi-natural ecosystems - Experience from Danish studies using the DAMOS
- 2013
-
In: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 66, s. 151-160
-
Journal article (peer-reviewed)abstract
- Local agricultural emissions contribute significantly to the atmospheric reactive nitrogen loads of Danish terrestrial ecosystems. In the vicinity of the sources this may be up to 6-8 kg N ha(-1) yr(-1) depending on location and ecosystem type. This contribution arises from dry deposition of gas phase ammonia derived from local livestock production. Long-range transport, however, often constitutes the largest contribution to the overall atmospheric terrestrial reactive nitrogen loadings in Denmark. This is often in the range 10-15 kg N ha(-1) yr(-1) and consists mainly of aerosol phase nitrate and ammonium (reaction products of nitrogen oxides and ammonia), but also dry deposition of other reactive nitrogen compounds (mainly nitrogen oxides in the form of gas phase nitric acid and nitrogen dioxide). In Denmark's environmental management of the sensitive terrestrial ecosystems modelling tools are required that account for both the local and the long-range transported contributions. This motivated development of the Danish Ammonia MOdelling System (DAMOS) that has been successfully applied to the assessment of atmospheric nitrogen loadings to sensitive Danish ecosystems. We present here three different examples of such assessments. Our results show that ecosystems located in Western Denmark (Case 1) receive the highest loads of atmospheric nitrogen depositions which generally exceed the critical load. This part of the country has the highest livestock density. In the Eastern part of the country, the atmospheric loadings are often below or close to the lower end of the interval for critical load values. These lower loads in Eastern Denmark (Case 2) are due to lower density of agricultural activities, as well as, lower precipitation rates, which leads to less wet deposition of reactive nitrogen. In general there is a gradient in atmospheric deposition over the country, with the highest depositions in the South-Western part of Denmark (Case 3) due to long-range transport contributions from North-Western Europe, but also due to local ammonia deposition associated with the high local emission from the high density livestock farming in this area. (c) 2012 Elsevier Ltd. All rights reserved.
|
|
