Search

The Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) is employed as an intercomparison tool for validating TROPOspheric Monitoring Instrument (TROPOMI) satellite NO2 retrievals against high-resolution Airborne Prism EXperiment (APEX) remote sensing observations performed in June 2019 in the region of Antwerp, a major hotspot of NO2 pollution in Europe. The model is first evaluated using meteorological and chemical observations in this area. Sensitivity simulations varying the model planetary layer boundary (PBL) parameterization were conducted for a 3 d period in June 2019, indicating a generally good performance of most parameterizations against meteorological data (namely ceilometer, surface meteorology, and balloon measurements), except for a moderate overestimation (∼ 1 m s−1) of near-surface wind speed. On average, all but one of the PBL schemes reproduce the surface NO2 measurements at stations of the Belgian Interregional Environmental Agency fairly well, although surface NO2 is generally underestimated during the day (between −4.3 % and −25.1 % on average) and overestimated at night (8.2 %–77.3 %). This discrepancy in the diurnal evolution arises despite (1) implementing a detailed representation of the diurnal cycle of emissions (Crippa et al., 2020) and (2) correcting the modeled concentrations to account for measurement interferences due to NOy reservoir species, which increases NO2 concentrations by about 20 % during the day. The model is further evaluated by comparing a 15 d simulation with surface NO2, NO, CO, and O3 data in the Antwerp region. The modeled daytime NO2 concentrations are more negatively biased during weekdays than during weekends, indicating a misrepresentation of the weekly temporal profile applied to the emissions obtained from Crippa et al. (2020). Using a mass balance approach, we determined a new weekly profile of NOx emissions, leading to a homogenization of the relative bias among the different weekdays. The ratio of weekend to weekday emissions is significantly lower in this updated profile (0.6) than in the profile based on Crippa et al. (2020; 0.84). Comparisons with remote sensing observations generally show a good reproduction of the spatial patterns of NO2 columns by the model. The model underestimated both APEX (by ca. −37 %) and TROPOMI columns (ca. −25 %) on 27 June, whereas no significant bias is found on 29 June. The two datasets are intercompared by using the model as an intermediate platform to account for differences in vertical sensitivity through the application of averaging kernels. The derived bias of TROPOMI v1.3.1 NO2 with respect to APEX is about −10 % for columns between (6–12) × 1015 molec. cm−2. The obtained bias for TROPOMI v1.3.1 increases with the NO2 column, following CAPEX=1.217Cv1.3-0.783 × 1015 molec. cm−2, in line with previous validation campaigns. The bias is slightly lower for the reprocessed TROPOMI v2.3.1, with CAPEX=1.055CPAL-0.437 × 1015 molec. cm−2 (PAL). Finally, a mass balance approach was used to perform a crude inversion of NOx emissions based on 15 d averaged TROPOMI columns. The emission correction is conducted only in regions with high columns and high sensitivity to emission changes in order to minimize the errors due to wind transport. The results suggest that emissions increase over Brussels–Antwerp (+20 %), the Ruhr Valley (13 %), and especially Paris (+39 %), and emissions decrease above a cluster of power plants in western Germany.

We present retrieval results of tropospheric nitrogen dioxide (NO2) vertical column densities (VCDs), mapped at high spatial resolution over three Belgian cities, based on the DOAS analysis of Airborne Prism EXperiment (APEX) observations. APEX, developed by a Swiss-Belgian consortium on behalf of ESA (European Space Agency), is a pushbroom hyperspectral imager characterised by a high spatial resolution and high spectral performance. APEX data have been acquired under clear-sky conditions over the two largest and most heavily polluted Belgian cities, i.e. Antwerp and Brussels on 15 April and 30 June 2015. Additionally, a number of background sites have been covered for the reference spectra. The APEX instrument was mounted in a Dornier DO-228 aeroplane, operated by Deutsches Zentrum für Luft- und Raumfahrt (DLR). NO2 VCDs were retrieved from spatially aggregated radiance spectra allowing urban plumes to be resolved at the resolution of 60 × 80 m2. The main sources in the Antwerp area appear to be related to the (petro)chemical industry while traffic-related emissions dominate in Brussels. The NO2 levels observed in Antwerp range between 3 and 35 × 1015 molec cm−2, with a mean VCD of 17.4 ± 3.7 × 1015 molec cm−2. In the Brussels area, smaller levels are found, ranging between 1 and 20 × 1015 molec cm−2 and a mean VCD of 7.7 ± 2.1 × 1015 molec cm−2. The overall errors on the retrieved NO2 VCDs are on average 21 and 28 % for the Antwerp and Brussels data sets. Low VCD retrievals are mainly limited by noise (1σ slant error), while high retrievals are mainly limited by systematic errors. Compared to coincident car mobile-DOAS measurements taken in Antwerp and Brussels, both data sets are in good agreement with correlation coefficients around 0.85 and slopes close to unity. APEX retrievals tend to be, on average, 12 and 6 % higher for Antwerp and Brussels, respectively. Results demonstrate that the NO2 distribution in an urban environment, and its fine-scale variability, can be mapped accurately with high spatial resolution and in a relatively short time frame, and the contributing emission sources can be resolved. High-resolution quantitative information about the atmospheric NO2 horizontal variability is currently rare, but can be very valuable for (air quality) studies at the urban scale.

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.

The effects of four regional emission scenarios on the concentrations of PM10, PM2.5, NO2 and EC (elementary carbon) in the North-West European (NWE) Hot Spot region have been studied. The emission estimates were provided by TNO, regional calculations were carried out for the years 2009 and 2020 using the BelEUROS model (Deutsch et al. 2009) on a 15 × 15 km2 grid. The effect of a highway speed limit reduction to 90 km/h on all highways in the NWE region (Belgium, France, Germany, Luxemburg, the Netherlands and the UK) showed up to 4.4% lower concentrations of EC and up to 3.5% reduction of NO2 concentrations (mean over Belgium). The introduction of low emission zones (LEZ) in all cities in the NWE region with more than 50.000 inhabitants and more than 700 inhabitants/km2 resulted in a reduction of 1.8% of the EC-concentrations (mean over Belgium). However, in the areas that actually make part of a LEZ the EC concentration is reduced by 19% and hence this scenario could be more effective in terms of population exposure. In the healthy diet scenario, 75% less meat production in Europe was assumed, leading basically to lower ammonia emissions (reduction of approximately 30%). This scenario results in significant reductions (4.2% as a mean over Belgium) in particulate matter (PM2.5) concentrations due to a reduction of secondary aerosol formation. EC-concentrations are not affected by this scenario. Finally, a pellet stoves scenario was calculated in which 20% of the non-wood energy consumption (gas, oil) in the residential combustion sector had been converted to pellet stoves. This scenario resulted in considerable increases in emissions and in an increase of EC-concentrations by up to 21% as a mean value over Belgium. PM2.5-concentrations increase by up to 4%. Results for all scenarios are available for the whole NWE region.

Agriculture can influence air quality via emissions of ammonia, soil dust and soot. These can be emitted into the atmosphere during farming practices, and contribute in different amounts to the total emissions and concentrations of air particulate matter (PM). The exact contribution of Flemish agricultural emissions to total air PM concentrations and to negative health effects are not well known. In this paper, agricultural emissions in Flanders and the processes leading to secondary PM are reviewed, together with their associated health effects. Agricultural ammonia emissions are a major contributor to local formation of secondary PM, and can increase above normal levels during some smog episodes. From a health perspective, secondary PM formed by ammonia is considered less important. Epidemiological studies suggest that combustion-related particles are the cause of negative health effects, although a reduction in ammonia emissions would reduce acidification and eutrophication of ecosystems. The World Health Organization currently considers PM2.5 as the best indicator for assessing human health effects. Setting an additional limit value for combustion-related particles would target potentially more harmful particles.

We present retrieval results of tropospheric nitrogen dioxide (NO2) vertical column densities (VCDs), mapped at high spatial resolution over three Belgian cities, based on the DOAS analysis of Airborne Prism EXperiment (APEX) observations. APEX, developed by a Swiss-Belgian consortium on behalf of ESA (European Space Agency), is a pushbroom hyperspectral imager characterised by a high spatial resolution and high spectral performance. APEX data have been acquired under clear sky conditions over the three largest and most heavily polluted Belgian cities, i.e. Brussels, Antwerp and Liège on 15 April and 30 June 2015. Additionally, a number of background sites have been covered for the reference spectra. The APEX instrument was mounted in a Dornier DO-228 airplane, operated by Deutsches Zentrum für Luft- und Raumfahrt (DLR). NO2 VCDs were retrieved from spatially aggregated radiance spectra allowing to resolve urban plumes at the resolution of 60 x 80 m2. Main sources in the Antwerp area appear to be related to (petro)chemical industry while traffic-related emissions dominate in Brussels. The NO2 levels observed in Antwerp range between 3 and 35 x 1015 molec m−2, with a mean VCD of 17.4 ± 3.7 x 1015 molec cm−2. In the Brussels area, smaller levels are found, ranging between 1 and 20 x 1015 molec cm−2 and a mean VCD of 7.7 ± 2.1 x 1015 molec cm−2. The overall error on the retrieved N2 VCDs is on average 21 % and 28 % for the Antwerp and Brussels data set, respectively. Low VCD retrievals are mainly limited by noise (1-sigma slant error), while high retrievals are mainly limited by systematic errors. Compared to coincident car mobile-DOAS measurements performed in Antwerp and Brussels, both data sets are in good agreement with correlation coefficients around 0.85 and slopes close to unity. APEX retrievals tend to be on average 12 % and 6 % higher for Antwerp and Brussels, respectively. Results demonstrate that the NO2 distribution in an urban environment, and its fine scale variability, can be mapped accurately with high spatial resolution and in a relatively short time frame, and the contributing emission sources can be resolved. High resolution quantitative information about the atmospheric NO2 horizontal variability is currently rare, but can be very valuable for (air quality) studies at the urban scale.

This article employs an optimized impact pathway approach to marginal external health costs that relies on high-resolution dispersion models calibrated for Belgium and the surrounding areas. Per tonne, the MEHCPM2.5 is found to be many times larger than MEHCNOx, which is currently negative. Further, the impact of Belgian PM2.5 emissions in the immediate area of generation is significantly larger than the impact on more distant areas; the opposite is true for NOx. The MEHCs of both pollutants are predicted to increase in the coming years. Further analysis of the impacts of PM2.5 and NOx reveals that, on average, modern gasoline vehicles outperform their diesel counterparts as far as future emissions are concerned. This contrasts with findings for 2007, which suggested that Euro 5 diesels had fewer associated health costs because of the potential for ozone reduction offered by their NOx emissions.

The spatial representativeness of air quality monitoring stations is a crucial parameter when the observed concentration levels are used in an air quality assessment. Spatial representativeness defines to what extent the monitoring data is meaningful and useful in a spatial context. Within this paper a generic and robust methodology is presented for the assessment of the spatial representativeness of air pollution monitoring sites. The methodology relies on a statistical approach that links annual averaged concentration levels with land use characteristics. The methodology is demonstrated for the monitoring sites in the Belgian telemetric air quality network and then applied to define a set of zones with a given confidence level. Within such a zone the concentrations deviate to a maximum percentage from the measured values at the monitoring sites. Furthermore, the relevance of spatial representativeness for model validation is addressed and the technique is illustrated for the validation of the results of the regional air quality model BelEUROS. In general, the overall improvement of the model validation by taking into account spatial representativeness can be quantified as in the order of 20%.

A combined mathematical model was developed for the regional-scale dynamics of gaseous admixtures and aerosols in the atmosphere. The model incorporates the following modules: thermo-hydrodynamic equations for meso-scale atmospheric processes in the non-hydrostatic approximation; transport of gaseous admixtures and aerosols, with allowance for photochemical transformation and binary homogeneous nucleation; and kinetic processes of condensation/evaporation and coagulation. Particular emphasis is given to the mechanisms of new-particle formation through binary homogeneous nucleation of drops of sulfuric acid and water vapor. By using this model, numerical experiments were performed to investigate spatio-temporal variations in the concentrations of gaseous admixtures and aerosols, as well as the formation of fine aerosol clusters in the Lake Baikal (Russia) and Antwerp (Belgium) areas due to strong industrial emission sources. The results of the numerical experiments are analyzed.

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 μg m −3 and a RMSE of 0.32 μg 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.

Ion chromatographic (IC) methods have been compared in order to achieve an optimal separation of fluoride, acetate and formate under various elution conditions on two formerly introduced analytical columns (i and ii) and a novel one (iii): (i) an IonPac AS14 (250 mm × 4 mm I.D.), (ii) Allsep A-2 (150 mm × 4.6 mm I.D.), and (iii) an IC SI-50 4E (250 mm (length) × 4 mm (internal diameter - I.D.)). The IC conditions for the separation of the anions concerned were optimized on the IC SI-50 4E column. A near baseline separation of these anions was attained on the IonPac AS14, whereas the peaks of fluoride and acetate could not be resolved on the Allsep A-2. A baseline separation for the three anions was achieved on the IC SI-50 4E column, when applying an eluent mixture of 3.2 mmol/L Na2CO3 and 1.0 mmol/L NaHCO3 with a flow rate of 1.0 mL/min. The highest precision of 1.7, 3.0 and 2.8% and the best limits of detection (LODs) of 0.014, 0.22 and 0.17 mg/L for fluoride, acetate and formate, respectively, were obtained with the IC SI-50 4E column. Hence, this column was applied for the determination of the acetic and formic acid contents of air samples taken by means of passive gaseous sampling at the Metropolitan Museum of Art in New York, USA. Atmospheric concentrations of acetic and formic acid up to 1050 and 450 μg/m3, respectively, were found in non-aerated showcases of the museum. In galleries and outdoors, rather low levels of acetic and formic acid were detected with average concentrations of 50 and 10 μg/m3, respectively. The LOD data of acetate and formate on the IC SI-50 4E column correspond to around 0.5 μg/m3 for both acetic and formic acid in air samples.

Between 2002 and 2006, various exceedances of air quality directive 1999/30/EC were reported in a number of PM10 monitoring stations in Flanders. A study was carried out with the objectives: i) to identify and quantify the sources that have caused or have contributed to the exceedances over this period; and ii) to propose suitable emission reduction measures to comply with the current air quality standards (2010). We followed an integrated multi-disciplinary approach consisting of a detailed analysis of the PM10 data series, specific air quality measuring campaigns, air quality modelling and expertise on emission reduction measures (including current BAT and BREF studies). The data analysis was based on 5 steps: 1) The pollution roses of the individual monitoring stations were analyzed. 2) The variation of the PM10 concentration in function of wind speed was assessed to determine whether we were dealing with a fugitive source of primary particles (e.g. mineral dust) or a source of smaller secondary particles taken up and dispersed by the ambient air flow (e.g. industrial combustion sources or traffic sources). 3) The temporal patterns of the potential sources were analyzed. 4) Specific measurement campaigns were organized in the neighbourhood of the potential sources. This included mapping of PM10 concentrations and a detailed analysis of the chemical composition. 5) The (fugitive) PM10 sources were quantified by means of reversed modelling. After deduction of a high background concentration, observed in all monitoring stations in Flanders, results for the individual monitoring stations show that in almost all cases the peak concentrations can be attributed to local fugitive PM10 emissions. Thus for most of the analysed cases it could be concluded that the cause of the exceedances or nearly exceedances is the combination of high background concentrations and local contributions from diffuse or fugitive sources. The total contribution of these non-registered diffuse sources was estimated to be 9–16% of the measured annual averaged PM10 concentrations.

Despite the scarce effect of speed limit reduction measures on total mass PM10 and PM2.5 concentrations, it is shown that the effect on the probably more hazardous component elemental carbon (EC) is more important which means that, from the viewpoint of health benefit, speed reductions during smog episodes may well be justified. Especially in the very dense highway network in Flanders with a 60% share of diesel cars (the highest in Europe) a speed limit reduction from 120 to 90 km/h during winter smog episodes on selected sections of Flemish highways leads to a significant decrease of the EC concentrations near those highways. Key findings are that the decrease in EC depends on the distance from the highways. In the direct vicinity of the highways, a decrease compared to the base-line scenario where no speed limit changes were implemented of up to 30% of the EC concentrations is modeled. Within a distance of 1500 m of the concerned highway sections there is an average decrease in EC of 0.18 μg m−3 affecting about 1 million people living in these areas. When the speed limit reduction measure is in force, the EC exposure of about 300,000 people decreases by at least 5% and 7500 people experience a decrease of 15% or more.

Daily and seasonal variation in the total elemental, organic carbon (OC) and elemental carbon (EC) content and mass of PM2.5 were studied at industrial, urban, suburban and agricultural/rural areas. Continuous (optical Dustscan, standard tapered element oscillating micro-balance (TEOM), TEOM with filter dynamics measurement system), semi-continuous (Partisol filter-sampling) and non-continuous (Dekati-impactor sampling and gravimetry) methods of PM2.5 mass monitoring were critically evaluated. The average elemental fraction accounted for 26% of the PM2.5 mass measured by gravimetry. Metals, like K, Mn, Fe, Cu, Zn and Pb were strongly inter-correlated, also frequently with non-metallic elements (P, S, Cl and/or Br) and EC/OC. A high OC/EC ratio (29) was generally observed. The total carbon content of PM2.5 ranged between 3 and 77% (averages: 1232%), peaking near industrial/heavy trafficked sites. Principal component analysis identified heavy oil burning, ferrous/non-ferrous industry and vehicular emissions as the main sources of metal pollution. This work compares various aerosol monitoring methods to characterize PM2.5 over six locations of different anthropogenic activities over Northern Belgium.

Air quality modeling can help to improve understanding of scale interactions related to meteorology, transport, emissions, formation, removal, and other processes taking place at local, urban, and regional scales. For the local scale, we used the coupling of a street canyon model with a Gaussian dispersion model to study the interactions of emissions and concentrations in urban streets and surrounding urban neighborhoods. The model combination was applied to a city quarter in Ghent, Belgium, and showed that up to 40% of the PM2.5 concentrations inside street canyons were caused by emissions from the surrounding streets. For the urban scale, the AURORA model has been used successfully in assessments of urban air quality for entire cities or urbanized areas. It has been applied to the Ruhr area in Germany to evaluate the impact of compact or polycentric cities versus the impact of urban sprawl developments. Results for ozone and PM10 showed that compact city structures may have more adverse effects in terms of air pollution exposure. For the regional scale, the EUROS model was used to study the urban and regional-scale interactions that are important in simulating concentrations of ozone, PM2.5, and PM10. It has been applied to study seasonal changes in aerosol concentrations in Flanders. High secondary aerosol concentrations were found during summer. This contribution was related to large contributions from outside the region, showing the importance of the continental scale when studying regional air quality problems.

PM10 and PM2.5 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 PM10 concentrations in an urban background station in Brussels. Results show that the trends in the PM10 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 PM10 emissions. The geographical pattern of PM10 as observed over Belgium is well reproduced by the model.

The influence of a protective double glazing system in the preservation of ancient stained glass windows in the Basilica Saint-Urbain, Troyes (France) was evaluated. In order to study the levels of gaseous and particulate pollutants, sampling was performed at protected and unprotected windows, as well as indoor, in the interspace and outdoor of the Basilica. Measurements were carried out for a period of one year. The concentration of NO2 was found to be higher inside of the church than in the interspace and outside of the church in contrast to O3 and SO2, which showed higher concentrations outdoor. In the case of CO2, an average concentration of 412 µg g−1 inside the Basilica was detected. However, during special ceremonies quite high, but only short-term lasting CO2-levels were observed. For the bulk analysis and for the studies of the chemical composition and abundance of individual particles, energy dispersive X-ray fluorescence (EDXRF) and electron probe micro analysis (EPMA) were applied. The average concentrations in bulk particles of the elements Al, Si, S, Cl, K, Ca, Ti, Mn, Fe, Cu, Zn, and Pb were comparably high indoors and outdoors. The composition of single particles was found to be more aggressive inside the church than outside. The fine fraction consisted mostly of soil dust, organic particles, ammonium nitrate and Ca–O–C-rich particles. In the coarse fraction, Ca–O–C-rich and organic particles showed the highest abundances. In the interspace also ammonium sulfate was detected. The results show that the installation of the protective glazing in the Basilica Saint-Urbain is from the gases’ point of view predominantly advantageous, but from the particles’ point of view it is only fairly good.

Since 2010, new estimations of the particulate matter emissions in Flanders have been made by using a tier-II approach. By means of a survey, the quantity of the wood by households, buildings (services sector), industry and agricultural sector consumption in Flanders has been estimated. A survey is necessary as not all consumed wood is purchased, e.g. some of the wood is sourced locally or waste wood is used. These surveys also provided data on the installation stock in Flanders, such as the type (fireplaces, pellet stoves, …) and age of the heating installation. Besides the wood consumption and use patterns, emission factors of particulate matter per type of wood and per type and age of heating installation were also updated based on international, recent literature on emission factors. Both new estimations resulted in an actualization of the particulate matter emissions of the residential wood burning in Flanders. Overall, the estimations were a factor 13 higher than the old estimations. This factor 13 is due to a factor 4 increase in the average emission factor and a factor of 3.4 in the wood consumption. As a result, heating in residential sector is estimated to be the most important emission source for primary particulate matter (37 % of all primary emissions) in Flanders. To confirm these results a comparison was carried out with the estimates of the contribution of wood burning to ambient PM10 concentrations based on measurements of levoglucosan. It was shown that about 10 % of the particulate matter concentrations in winter were due to wood burning, while in summer this amounted only 2–3 %. In the next step, a dispersion model has been used in order to check the consistency of both results. It is shown that the increased emissions are consistent with the measured particulate matter concentrations due to wood burning. Indeed, the increase in emissions by a factor 13 is needed to understand the high levoglucosan concentrations in ambient air in Flanders. Finally, the large changes that have been made to the Belgian SNAP-2 emission inventory due to the results of this study, raise questions about the homogeneity (both spatial and temporal) of the European emission inventory for this sector. Adjustments to this sector could possibly decrease the modelled PM-gap quite substantially.

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).

Indoor and outdoor atmospheres of the ‘Koninklijk Museum voor Schone Kunsten’ (KMSK, Royal Museum of Fine Arts) in Antwerp, Belgium, were thoroughly characterised to determine the air quality inside the museum and the factors controlling it. During a winter and a summer campaign aerosol particles, pollutant gases, bacteria and fungi were sampled and different indoors microclimatic parameters were measured. The chemical composition of particulates suspended in indoor and outdoor air was analysed, both with reference to bulk aerosol matter and to individual particles. Outdoor sources largely determined the composition of indoor aerosol. The main particle types identified in winter were Ca-rich, Ca–Si and sea salt particles. In summer, S-rich particles were most abundant. Dry deposition was sampled in order to determine the amount of particulate matter that could potentially deposit onto the works of art. The concentrations of NO2 and SO2 amounted to 12 and 5–6 ppb, respectively, both in winter and in the summer. The microclimates inside the exhibition rooms were affected by poorly balanced heating and air-conditioning, free-standing humidifiers, ventilating and lighting systems and the daily flux of visitors, which produced rapid changes and marked thermo-hygrometric gradients. Based on these results, suggestions for the improvement of the heating and air-conditioning system could be made. Microbial loads were higher in summer than in winter. However, the proportion of microorganisms capable of degrading proteins or hydrolysing fats, and thus pernicious to works of art, was not significantly increased inside the museum.

The results of a study of the elemental and ionic composition of the ambient aerosol in and around Antwerp are presented. Four sampling campaigns were performed, covering all seasons. The samples were obtained by filtration and impaction methods. Subsequently, the filters were analyzed by X-ray fluorescence spectrometry for elements, and the impactor substrates were leached with water and analyzed by ion chromatography for ions. When comparing the results of the chemical analysis with the meteorological information, it was found that the concentration of certain elements and ions in aerosol samples was affected considerably by the location of the sampling site and by the meteorological conditions. In relatively less polluted places like small towns and rural regions around Antwerp, the concentrations of some elements and ions showed qualitatively a positive or negative correlation in their time variations with the amount of precipitation. Hence, we suppose that in the first case these elements and ions are contained mainly in the more hygroscopic fraction (the most apparent is the behavior of Na and Cl), and that in the second case, the elements are mainly present in the less hygroscopic fraction of the ambient aerosol. However, this behavior of the elements and ions may be different for various particle size ranges. In the highly urbanized and industrial sites close to the central and industrial parts of Antwerp, these correlations were not found. This could be connected with the high and variable local aerosol generation rate, when only heavy rains are able to provide a sufficient removal of the aerosols from the atmosphere.

We studied and compared different operational modeling techniques that are used to generate regional scale concentration maps for PM10, PM2,5, NO2 and O3 over Belgium. The various techniques and resulting maps were analyzed, validated and compared aiming at identifying the best possible regional scale concentration map for each pollutant. A distinction was made between a temporal and a spatial validation. The temporal analysis revealed that an intelligent interpolation technique based on land use characteristics in general performs best in capturing the temporal aspects of air quality in Belgium for the investigated pollutants. For PM10 and PM2.5 this technique also performs best in generating the spatial pattern of the observed annually averaged concentrations. A deterministic model combined with a corrective ‘Optimal Interpolation’ data assimilation technique performs best in reproducing the spatial pattern of O3. For NO2 the interpolation technique manages best in explaining the spatial pattern of the observed annually averaged concentrations in Belgium, but when restricted to the region of Flanders, it competes with a thoroughly calibrated Lagrangian type of modeling.

The water-solubility differentiates atmospheric particles into cloud condensation nuclei (CCN) and interstitial aerosol. This interaction between aerosol and cloud influences the climate in different known and hypothetical ways [Hansson et al. (1994) In Proceedings of EUROTRAC Symposium' 94, (edited by Borrell P. M.), p. 984. SPB Academic Publishing, The Hague; Schwartz et al. (1995) In Aerosol Forcing of Climate (edited by Charlson R. J. and Heintzanberg J.), p. 251. Wiley, London]. Some authors studied the fraction of water-soluble amounts with particle size [Meszaros (1968) Tellus 20, 443; Winkler (1974) Meteorol. Rdsch. 27, 129; Fuzzi et al. (1988) Journal of geophysics Research 93, 11141; Svenningsson et al. (1992) Tellus 44B, 556; (1994) Journal of Atmospheric Chemistry 19, 129). As the water-solubility (or hygroscopicity) is a property of chemical compounds it is of great interest to identify the chemical composition of aerosols and of the dissolved fraction. Using an optimal combination of analytical methods, the elemental and species concentrations were determined in the original aerosol as well as in the resulting solutions. The fraction of soluble species were calculated from the measured values and three groups were found: with high (50–73%), medium (20–26%), and low (2%) dissolved fraction. In a further series of experiments the rate constants of dissolution of various species were determined. These can be arranged in the order of decreasing rate of dissolution: the alkaline and alkaline earth elements K+ ≈ Mg2+ > NH4+ > Na+ > Ca2+ the anions NO3− ≈ SO42− Cl–, and for the iron oxidation states Fe3+ ⪢ Fe2+. A photolytic reduction of Fe3+ to Fe2+ was also observed. For Mg2+, Ca2+, and SO42− a dependance of the rate constants for dissolution on time was discovered. This can be explained by the presence of different chemical compounds in the aerosol. The discussion of the results with regard to the time scale of the formation of cloud or fog droplets shows that the slightly soluble inventory of a solid aerosol of the alkaline and alkaline earth elements, as well as of the anions, is dissolved into the aqueous phase in a relatively short time interval of 10–700s. On the other hand, Fe3+ is dissolved in a time period of 3000-4500s, whereas Fe2+ appears in the solution in a time period of up to 7000s.

Seven rain and 2 snow samples collected in October and November 1993 were analyzed by GFAAS. Manganese concentrations ranging from 0.3 to 11.3 μg/L were found. pH-values (4.04–4.89, mean 4.52) and redox potentials (528–665 mV, mean 581 mV) were additionally determined. This is important with respect to a qualified specification of Mn in atmospheric samples. A 0.45 μm-filtration of the samples prior to GFAAS-analysis showed the same manganese concentrations in the filtrate as in the unfiltered samples. Hence, the amount of solid Mn species in the investigated samples is negligible. For an examination of the oxidation state of Mn some investigations concerning the stability of Mn(III) were carried out. They indicated that Mn(III) is unstable under atmospheric conditions. For checking whether all the manganese in rainwater exists as Mn(II), a sensitive IC method for the detection of Mn(II) was developed. By adapting a photometric procedure based on the oxidation of Leucomalachite Green (LMG) to Malachite Green (MG) by permanganate (MnO-4) to the IC-flow-through-system, a limit of determination of 1 μg/L Mn(II) could be achieved. A comparison of the IC measurements with GFAAS-results of the filtered samples showed agreeing results. Thus, manganese in rainwater and snow exists entirely as soluble Mn(II).

The methodology of protecting the European stained glass windows against environmental risk (e.g. meteorological factors, air pollution, microorganisms) by means of an external glazing is not new. In spite of many scientific studies carried out in the last 20 years, some questions were still up for discussion. The European VIDRIO (2002–2005) project gave an answer to these questions. The research carried out by the different project partners established a new multidisciplinary approach aimed at evaluating the efficiency of the protective glazing systems and their effects on stained glass windows conservation, and finally at assessing the most appropriate strategy to preserve stained glass windows. Scientific results showed that the so-called isothermal glazing (i.e. ventilation by the air coming from the inside of the building) protected efficiently the ancient stained glass window from environmental attack (i.e. rain, pollutants, condensation, thermal shocks) with very limited secondary effects. The scientific research highlighted that its efficiency was strongly related to the technical design of the protective system. In particular, the ventilation and the size of the interspace had to be carefully considered. The research developed within the VIDRIO project was turned into general recommendations to the owners and practitioners on the best practice for the stained glass windows future conservation.

This chapter assesses the use of an Emission Trading Scheme (ETS) for the year 2020 to reduce the emissions from international ships entering European Community ports. Additional costs and benefits of including the maritime sector into a land-based ETS for NOx and SO2 are quantified.

Indoor and outdoor concentrations of atmospheric gaseous pollutants as well as composition, size, and morphology of particulate matter have been investigated at the monastery of San Jerónimo in Granada (Southern Spain). Complementary micro- and nano-analytical techniques were applied; elemental and mineralogical composition and morphological characteristics of particulate matter were investigated combining electron probe microanalysis at the single particle level, and bulk aerosol samples were analyzed using energy-dispersive X-ray fluorescence, X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray analyzer and transmission electron microscopy (TEM). Microclimatic conditions at the monastery were monitored, and gas concentrations were assessed by means of diffusion tubes subsequently analyzed with ion chromatography. Results revealed high abundances of soil dust particles (aluminosilicates, calcite, dolomite, quartz), salt aerosols (chlorides, sulfates and ammonium-rich salts), and NO2 and SO2 both outdoors and indoors. Amorphous black carbon particles had surprisingly high abundances for Granada, a non-industrialized city. The composition of indoor particles corresponds to severe weathering affecting the construction materials and artworks inside the church; moreover their composition promotes a feedback process that intensifies the deterioration. Chemical reactions between chloride-rich salts and pigments from paintings were confirmed by TEM analyses. Indoors, blackening of surface decorative materials is fostered by particle re-suspension due to cleaning habits in the monastery (i.e. dusting). This is the first air quality study performed in a monument in the city of Granada with the aim of developing a strategy for preventive conservation.

Levels of urban gaseous and particulate pollutants were investigated in the Cathedral of Cologne, Germany in the framework of the EU-project “VIDRIO”. The purpose of this study was to evaluate the influence of a protective double glazing system on the preservation of ancient stained glass windows by sampling at protected and unprotected windows (indoors, in the interspace and outdoor of the Cathedral). The interspace between the ancient stained glass window and the protective glazing is flushed in the Cathedral by indoor air, hence isolating the historic glass from the outdoor air and exposing it to indoor air on both sides of the glass panels. Concentrations of aggressive gaseous pollutants such as NO 2 , SO 2 , O 3 and CO 2 as well as elemental concentrations of bulk particles and relative abundances of single particles were surveyed at all sampling locations. Elemental concentrations in bulk particulate matter were found to be significantly lower inside the Cathedral in comparison to the outdoor air. This result is advantageous for the stained glass windows. Single particle analysis of the samples from Cologne showed also soil dust and organic particles as well as sulphates and nitrates, from which the latter two compounds are dangerous for the stained glass windows. On the base of the obtained results, it can be concluded that the protective glazing system in the Cathedral of Cologne can be considered as predominantly advantageous from both the gases' point of view (except for NO 2 -candles burning) and from the particles' point of view.

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 seeks to calculate marginal external costs from human health impacts of transport air pollution. We focus on PM2.5 and NOx emissions in Belgium. Our analysis builds upon the widely used impact pathway approach. The great novelty compared to previous work is that both future emissions and background concentrations are modelled now, taking into account different destinations of a tonne of emitted pollutant now versus in the future. Moreover, the model allows for demographic evolution. We find similar results from two separate exercises: one for Belgian and one for Flemish PM2.5 and NOx emissions.

CORINAIR atmospheric emission inventories are frequently used input data for air quality models with a domain situated in Europe. In CORINAIR emission inventories, sources are broken down over 11 major source categories. This paper presents spatial surrogates for the disaggregation of CORINAIR atmospheric emission inventories for input of air pollutants and particulate matter to grid or polygon based air quality model domains inside Europe. The basis for the disaggregation model was the CLC2000 land cover data to which statistical weights were added. Weights were population census data for residential emissions, employment statistics for agricultural and industrial area emissions, livestock statistics for ammonia emissions and annual aircraft movements for emissions realized by air transport. Additional road and offroad network information was used to disaggregate emissions realized by traffic. A comparison of top down produced emission estimates with spatially resolved national emission data for The Netherlands and the United Kingdom gave confidence in the present spatial surrogates as a tool for the top down production of atmospheric emission maps. Explained variance at a spatial resolution of 5 km was >70% for CO, NMVOC and NOx, >60% for PM10 and almost 50% for SO2., JRC.H.5-Rural, water and ecosystem resources

For the isocratic ion chromatography (IC) separation of low-molecular-mass organic acids and inorganic anions three different anion-exchange columns were studied: IonPac AS14 (9 microm particle size), Allsep A-2 (7 microm particle size), and IC SI-50 4E (5 microm particle size). A complete baseline separation for all analyzed anions (i.e., F(-), acetate, formate, Cl(-), NO(2)(-), Br(-), NO(3)(-), HPO(4)(2-) and SO(4)(2-)) in one analytical cycle of shorter than 17 min was achieved on the IC SI-50 4E column, using an eluent mixture of 3.2mM Na(2)CO(3) and 1.0mM NaHCO(3) with a flow rate of 1.0 mL min(-1). On the IonPac AS14 column, it was possible to separate acetate from inorganic anions in one run (i.e., less than 9 min), but not formate, under the following conditions: 3.5mM Na(2)CO(3) plus 1.0mM NaHCO(3) with a flow rate of 1.2 mL min(-1). Therefore, it was necessary to adapt a second run with a 2.0mM Na(2)B(4)O(7) solution as an eluent under a flow rate of 0.8 mL min(-1) for the separation of organic ions, which considerably enlarged the analysis time. For the Allsep A-2 column, using an eluent mixture of 1.2mM Na(2)CO(3) plus 1.5mM NaHCO(3) with a flow rate of 1.6 mL min(-1), it was possible to separate almost all anions in one run within 25 min, except the fluoride-acetate critical pair. A Certified Multianion Standard Solution PRIMUS for IC was used for the validation of the analytical methods. The lowest RSDs (less than 1%) and the best LODs (0.02, 0.2, 0.16, 0.11, 0.06, 0.05, 0.04, 0.14 and 0.09 mg L(-1) for F(-), Ac(-), For(-), Cl(-), NO(2)(-), Br(-), NO(3)(-), HPO(4)(2-) and SO(4)(2-), respectively) were achieved using the IC SI-50 4E column. This column was applied for the separation of concerned ions in environmental precipitation samples such as snow, hail and rainwater.

In this paper, we assess the status of the air quality in the Lake Baikal region which is strongly influenced by the presence of anthropogenic pollution sources. We combined the local data, with global databases, remote sensing imagery and modelling tools. This approach allows to inventorise the air-polluting sources and to quantify the air-quality concentration levels in the Lake Baikal region to a reasonable level, despite the fact that local data are scarcely available. In the simulations, we focus on the month of July 2003, as for this period, validation data are available for a number of ground-based measurement stations within the Lake Baikal region.

A methodology is presented for the assessment of the spatial representtativeness of air pollution monitoring data. The methodology relies on a statistical approach that links air quality expectation values with land use characteristics. The relevance of this issue for model validation is addressed and the technique is illustrated for the validation of BelEUROS model results.

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.

A method for the separation of acetate and formate anions by ion chromatography has been optimized under various measurement conditions (e.g. the composition of the mobile phase, and the flow rate of the eluent). For this purpose, two different analytical columns were examined: the IonPac AS14 (250 mm × 4 mm i.d.; designed mostly for the separation of inorganic anions) and the Allsep A-2 (150 mm × 4.6 mm i.d.; designed for the separation of low-molecular mass organic acids). However, nearly baseline separation of acetate and formate has been found on each column using the following conditions: (i) IonPac AS14 column and 2.0 mM Na 2 B 4 O 7 solution as an eluent with a flow rate of 1.0 ml/min, or (ii) Allsep A-2 column and an eluent containing a mixture of 1.2 mM Na 2 CO 3 plus 1.5 mM NaHCO 3 with a flow rate of 1.3 ml/min. Additionally, the separation of fluoride from acetate and formate on both columns was studied. On the IonPac AS14 column it was possible to separate all three investigated anions. However, on the Allsep A-2 column, when the concentration of fluoride was comparable to, or higher than acetate, it was impossible to achieve good separation of these two anions, even using the optimized elution procedure. Therefore, the measurements of real samples were carried out with the use of IonPac AS14 column. The concentrations of acetate and formate have been determined in the air samples of the Cathedral of Cologne (Germany), after sampling the corresponding acids by passive diffusion tubes. Average concentrations of 122 and 9 μg/m 3 for acetic and formic acids were found, respectively, inside the Cathedral and in a depot with medieval stained glass panels.

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 Smog model (EUROS) was extended with two special modular algorithms for atmospheric particles. The first module is the Caltech Atmospheric Chemistry Mechanism (CACM) which describes in a mechanistic way the formation of precursors of secondary organic aerosols. The second module is the Model of Aerosol Dynamics, Reaction, Ionization and Dissolution (MADRID 2), which describes the formation of secondary aerosols by means of an equilibrium between the gas phase and the aerosol phase. It includes inorganic as well as hydrophilic and hydrophobic organic compounds. Through this extension, the EUROS model was able to model mass and chemical composition of aerosols in two size fractions (PM 2.5 and PM 10-2.5 ). The model was validated for 3 seasonal episodes in 2002 and 2003. A comparison between modelled and observed aerosol concentrations showed that the trends in PM 10 concentrations are well captured. A strong seasonal dependency was found in the chemical composition of the aerosols. Large contributions of secondary inorganic components were found for summer episodes with high aerosol concentrations, whereas during autumn/winter episodes the concentrations of secondary aerosol were less abundant.