During the last 15 years, the official assessment maps in Flanders have improved from a map consisting of only measured data points to a high resolution assessment which covers the complete area and takes into account several types of sources and street canyons. In order to improve this level of detail, multiple steps were taken. First of all, a land use regression model was introduced at an hourly scale at 4 × 4 km2 resolution. Secondly, a Gaussian model was added for both point and line sources, correcting for emission double counting. Finally, a street canyon model was added to the chain, leading to improved resolution in these street canyons. In this work, we will discuss the problems encountered in these years such as how to account for double counting of emissions, how to correct the locations of the simplified road network and how to determine when street canyon calculations must be performed and how we solved them.

This paper quantifies the effect of a number of input parameters on the emission levels of road transport emissions calculated by means of a bottom-up methodology. The input parameters considered cover small diesel cars, calculation of additional fuel consumption due to the use of mobile air conditioning in passenger cars and light commercial vehicles, fine-tuning of trip lengths and definition of road types for Belgium in 2010. The effect is significant for CO2, and even more pronounced for other pollutants such as NOx, PM2.5, and VOCs. (C) 2014 Elsevier Ltd. All rights reserved.

Assessing local air quality can be a challenging task. Indeed, local air quality is strongly dependent on local factors but also regional and in some cases even global effects have to be taken into account when assessing local air pollution concentrations. Furthermore, large gradients in pollutant concentrations can be present in the urban environment. In order to assess the local air quality for the city of Antwerp, a combination of an Eulerian dispersion model, a measurement interpolation tool, a Gaussian plume model and a simplified version of the OSPM street canyon model have been coupled to each other, taking into account double counting effects of local emissions. The coupled model which combines the regional, urban and street canyon scale has been applied for the city centre of Antwerp and its harbour. This results in detailed maps with a resolution up to 30 m for four pollutants: PM10, PM2.5, EC (elementary carbon) and NO2. Furthermore, several abatement measures have been assessed in order to improve the urban air quality. It has been shown that local (traffic) measures only have a small effect on total mass PM10 and PM2.5 concentrations, but exhibit a larger effect on EC and NO2-concentrations.

It is well known that computational fluid dynamics (CFD) models require significant amounts of processing time. Producing annual statistics, which are often required for policy support and EU directive compliance testing, is therefore unfeasible with current typical computing infrastructures. In this contribution, we will describe the application of a meteo-averaging methodology as described in Parra et al, (2010) and similarly Sollazo et al, (2011) for two test cases in Antwerp, partly in the frame of the ATMOSYS (http://www.life-atmosys.be) project cofinanced by the European LIFE+ program. Normalised NOx concentrations for 18 wind directions were simulated as a passive tracer in the ENVI-met model (Bruse et al, 1998) for each of 5 different major line sources in the domain. In-situ measurements were used to parameterize the local NO2/NOx ratio. The simulation results were compared on an hourly basis to the NO2 concentration difference of a curb-side station and a station which is located some 30 m further away from the road. In addition, we will illustrate the approach for an urban development project in the city of Antwerp near the busy ring road. Here, the effect of a row of shielding-houses on the annual averaged NO2 concentrations in the area as calculated by the CFD meteostatistics approach, was estimated and superimposed onto an earlier street-level air quality assessment (Lefebvre et al, 2012).

Vegetation is often quoted as an effective measure to mitigate urban air quality problems. In this work we demonstrate by the use of computer models that the air quality effect of urban vegetation is more complex than implied by such general assumptions. By modelling a variety of real-life examples we show that roadside urban vegetation rather leads to increased pollutant concentrations than it improves the air quality, at least locally. This can be explained by the fact that trees and other types of vegetation reduce the ventilation that is responsible for diluting the traffic emitted pollutants. This aerodynamic effect is shown to be much stronger than the pollutant removal capacity of vegetation. Although the modelling results may be subject to a certain level of uncertainty, our results strongly indicate that the use of urban vegetation for alleviating a local air pollution hotspot is not expected to be a viable solution.

Using the MOBILEE methodology, we performed a detailed air quality assessment for three scenarios for the ring road around Antwerp, a major city in Belgium, using PM10 and NOx emission inventories for 2003 (reference) and 2015 (projected future situation), followed by an assessment of the exposure of the population living in the vicinity of the planned constructions. PM10 turned out to be the dominant parameter in exposure assessment. Compared with the impact of the viaduct, a tunnel with an exhaust at a height of 5 or 30 m shows respectively a 40% increase or a 5% decrease in total exposure.

The ability of a complex model chain to simulate elemental carbon (EC) concentrations was examined. The results of the model chain were compared to EC concentration measurements made at several locations, every sixth day. Two measurement campaigns were taken into account, one in 2006-2007 and one in 2008-2009. The model results compare very well for both periods, with an R-2 of 0.74, a bias of 0.02 mu g m(-3) and a RMSE of 0.32 mu g m(-3). Sensitivity analyses to different meteorology inputs and changing emissions from year to year were performed. The differences between the two measurement periods were also investigated. It is shown that somewhat more than half of these differences is due to meteorology. However, emission changes also play an important role. (C) 2011 Elsevier Ltd. All rights reserved.

Using a combination of models, high resolution air quality maps for Flanders (Belgium) have been made. First of all, the Eulerian air quality model AURORA has simulated for a complete year the air pollutant concentrations over the region on a 3 × 3 km² resolution. These results are calibrated using the RIO-interpolation model on air quality station data. Thereafter, an extra simulation using the bi-Gaussian IFDM model is made on a resolution of 1 × 1 km², with a finer resolution (up to 25 m) close to the major roads. The nesting methodology of IFDM in AURORA is designed to avoid double counting of the roads. The results are highly detailed PM10, PM2.5, NO2 and EC maps for Flanders. Using station data and data from several measurement campaigns, the maps have been validated and it has been shown that the maps show indeed a highly detailed picture of the air quality in Flanders. These data will be used in assessing the air quality and human exposure to it in Flanders, and in assessing policy scenarios designed to improve the air quality.

This paper presents the results of two recent case studies which were evaluated with the CFD model ENVI-met. In a first case, the impact of a vegetation barrier along a highway on the local air quality is studied. In a second case, the dispersion of total UFP concentrations within a street canyon is examined. In both cases, ENVI-met model output is compared with measurements resulting in an overall acceptable agreement of the model performance.

In this paper a CFD-based micro scale air quality model called ENVI-met is presented. ENVI-met distinguishes itself from other CM-models due the implementation of a detailed vegetation model which describes the interaction of local vegetation, not only on the wind field, but also on the thermodynamic processes and the diffusion and deposition of gases and particulate matter. This makes the model particularly suitable for a recent research programme initiated by the Air Quality Innovation Programme (IPL), founded by the Dutch Ministry for Transport, Public Works and Water Management (Rijkswaterstaat) and the Ministry of Housing, Spatial Planning and the Environment (Ministry of VROM). One of the seven branches of the IPL-programme is to investigate both by measurements and modelling the effect of line vegetation along a motorway on local air quality. Recently the model results have been compared to a first measurement campaign.

Owing to the richer set of concepts which are involved in activity-based transportation models, the potential advantages of an activity-based approach for air quality purposes have been recognized for a long time. However, models that have been developed along these lines are still scarce. In this research the activity-based model ALBATROSS was used in combination with the emission model MIMOSA to assess the travelled distances and the mobile source emissions produced by passenger cars in the Netherlands. The fact that this approach is based on hourly travel and emission values, rather than on aggregated results or peak hour values, a common practice within other traditional models, is an important added value. The predicted values seem to correspond well with the reported values from the Dutch Scientific Statistical Agency. Predictions for travelled distances overestimated the reported values by approximately 8%. Predictions for emissions of nitrogen oxide, carbon dioxide, volatile organic compounds, and particular matter differed by 16%, 11%, 9%, and 3%, respectively, from the officially reported values. This paper is novel in the sense that it both reports on the applied methodology and presents the practical results from a case study of the activity-based emission modelling approach.

In the paper a CFD-based micro scale air quality model called ENVI-met will be presented. ENVI-met distinguishes itself from other CFD-models due the implementation of a detailed vegetation model which describes the interaction of local vegetation, not only on the wind field, but also on the thermodynamic processes and the diffusion and deposition of gases and particulate matter. This makes the model particularly suitable for a recent research programme initiated by the Air Quality Innovation Project (IPL), founded by the Dutch Ministry for Transport, Public Works and Water Management (Rijkswaterstaat) and the Ministry of Housing, Spatial Planning & the Environment (Ministry of VROM). One of the seven branches of the IPL-project is to investigate both by measurements and modelling the effect of line vegetation along a motorway on local air quality. Recently the model results have been compared to a first measurement campaign.

BACKGROUND:Radioadaptation is a phenomenon whereby cells exposed to a low dose of ionizing radiation are more resistant to a much higher dose delivered some time thereafter. This phenomenon could result from the activation of damage repair and/or antioxidant defense systems by the low dose.MATERIALS AND METHODS:The existence of a cytogenetic adaptive response in female germ cells was investigated using a recently developed in vitro system. Mouse ovarian follicles were cultured from an early preantral stage up to ovulation. The follicles were X-irradiated with either 2 or 4 Gy ("challenge dose") preceded or not by 50 mGy ("conditioning dose", 5 h earlier), on days 0 or 12 of the culture. Ovulated oocytes were collected on day 13, fixed and analyzed for the presence of chromosome aberrations.RESULTS:Irradiation with 2 or 4 Gy on days 0 or 12 did not influence ovulation but had dose-dependent effects on the germinal vesicle breakdown of the oocytes. It also caused dose-dependent chromosome damage, with a greater sensitivity of oocytes to this effect when irradiation occurred on day 12 than on day 0. Prior irradiation of oocytes with the dose of 50 mGy led to a reduction in the yield of chromosome aberrations when irradiation occurred on day 12 but not on day 0.CONCLUSION:These results suggest that pre-irradiation of mouse pre-ovulatory oocytes with a low conditioning dose could confer on them some protection against radiation-induced chromosomal damage by a subsequent challenge dose of a few Gy.

PM 10 and PM 2.5 concentration in Belgium and its surrounding countries were simulated for 2002 by means of the air quality model EUROS. The EUROS model simulates the transport and chemistry of gaseous species as well as the formation of fine particles. The paper describes the mathematical formulation of the partial differential equations used in the model and briefly discusses the main numerical solution techniques. The extension of the model with two modules for the calculation of atmospheric aerosol particles is lined out. The modelled concentrations for 2002 are compared with measured PM 10 concentrations in an urban background station in Brussels. Results show that the trends in the PM 10 time series are well represented. However, the model substantially underestimates the actual measured concentrations due to the fact that the emission inventories do not include all of the known sources of primary PM 10 emissions. The geographical pattern of PM 10 as observed over Belgium is well reproduced by the model.

Seasonal changes in aerosol compositions over Belgium and Europe are simulated with an extended version of the EUROS model. EUROS is capable of modelling mass and chemical composition of aerosols in two size fractions (PM2.5 and PM10-2.2). The chemical composition is expressed in terms of seven components: ammonium, nitrate, sulphate, primary inorganic compounds, elementary carbon, primary organic compounds and Secondary Organic Compounds (SOA). A comparison of modelled and measured aerosol concentrations showed that modelled concentrations are generally consistent with observed concentrations. The chemical composition of the aerosol showed a strong dependence on the season. High aerosol concentrations during the summer were mainly due to high concentrations of the secondary components nitrate, ammonium, sulphate and SOA in the size fraction PM2.5. In contrast, during autumn and winter, increased PM-concentrations were mainly due to higher concentrations of primary components, especially in the size fraction PM10-2.5.

We applied the extended version of the EUROS model to evaluate the impact of emission reductions on PM10 and PM2.5 concentrations in Flanders and Belgium for 2015. Individual sector contributions were assessed and the current and future changes in aerosol concentrations and compositions over Belgium and Europe were investigated. Contributions from anthropogenic sources in Flanders were found to be responsible for 34.3% of the annual averaged PM10 concentrations in Flanders in 2003. In 2015 this contribution is estimated to be 35.0%. For PM2.5 these contributions are 29.1% in 2003 and 27.8% in 2015 respectively. Results show that non-linear effects can not be neglected. Because of the non-linear processes that take place when secondary aerosols are formed, a small reduction in a gaseous compound (e.g. SO2) does not necessarily lead to the same amount of reduction of the secondary compound (e.g. sulphate). Another "non-linear" aspect is the formation of aerosols by contributions from two compounds that are delivered by two individual sectors. The synergetic effect of these "non-linear" contributions was found to be an additional 2.1% for PM10 and 3.7% for PM2.5, representing an increase of 6–13%, which is not negligible and might become relevant in abatement policies.

We used the Eulerian Chemistry-Transport Model EUROS to simulate the concentrations of airborne fine particulate matter above Europe. Special attention was paid to both primary as well as secondary particulate matter in the respirable size range up to 10 μm diameter. Especially the small particles with diameters up to 2.5 μm are often formed in the atmosphere from gaseous precursor compounds. Comprehensive computer codes for the calculation of gas phase chemical reactions and thermodynamic equilibria between the compounds in the gas phase and those ones in the solid phase had been implemented into the EUROS-model. Obtained concentrations of PM 10 for the year 2003 are compared to measurements. Additionally, calculations were carried out to assess the contribution of emissions derived from the sector agriculture in Flanders, the northern part of Belgium. The obtained results demonstrate the importance of ammonia emissions in the formation of secondary particulate matter. Hence, future abatement policy should consider more the role of ammonia in the formation of secondary particles.

The Eulerian Chemistry-Transport Model BelEUROS was used to calculate the concentrations of airborne PM10 and PM2.5 over Europe. Both primary as well as secondary particulate matter in the respirable size-range was taken into account. Especially PM2.5 aerosols are often formed in the atmosphere from gaseous precursor compounds. Comprehensive computer codes for the calculation of gas phase chemical reactions and thermodynamic equilibria between compounds in the gas-phase and the particulate phase had been implemented into the BelEUROS-model. Calculated concentrations of PM10 and PM2.5 are compared to observations, including both the spatial and daily, temporal distribution of particulate matter in Belgium for certain monitoring locations and periods. The concentrations of the secondary compounds ammonium, nitrate and sulfate have also been compared to observed values. BelEUROS was found to reproduce the observed concentrations rather well. The model was applied to assess the contribution of emissions derived from the sector agriculture in Flanders, the northern part of Belgium, to PM10- and PM2.5-concentrations. The results demonstrate the importance of ammonia emissions in the formation of secondary particulate matter. Hence, future European emission abatement policy should consider more the role of ammonia in the formation of secondary particles.

The European Operational Smog (EUROS) integrated air quality modelling system has been extended to model fine particulate matter (PM). From an extended literature study, the Caltech Atmospheric Chemistry Mechanism and the Model of Aerosol Dynamics, Reaction, Ionisation and Dissolution were selected and recently coupled to EUROS. Currently, modelling of mass and chemical composition of aerosols in two size fractions (PM2.5 and PM10–2.5) is possible. The chemical composition is expressed in terms of seven components: ammonium, nitrate, sulphate, elementary carbon, primary inorganic compounds, primary organic compounds and secondary organic compounds. Calculated PM10 concentrations and chemical composition are presented for two summer months of the year 2003 (1 July to 31 August).