Meteorological variability in NO2 and PM10 concentrations in the Netherlands and its relation with EU limit values

The extent of the exceedance of the EU limit values for nitrogen dioxide (NO₂) and particulate matter (PM₁₀) concentrations within the Netherlands is expected to decrease significantly, in the coming years. Whether limit values will actually be exceeded, in the next decade, depends not only on European, national and local policies, but also on the effects of inevitable interannual meteorological fluctuations. An analysis of model calculations and measurements yields variations (1 sigma) in the annual average concentration of about 5% for NO₂ and 9% for PM₁₀, due to meteorological fluctuations. These deviations from long-term average concentrations affect assessments of future levels, set against limit values. For instance, an NO₂ concentration of 39 μg m^?3, estimated for a given year with long-term average meteorology, indicates that it is likely (chance >66%) that the limit value of 40 μg m^?3 will not be exceeded in that particular year. At the same time, the estimation also indicates, for example, that this situation is unlikely (change <33%) to continue for three years in a row. However, with an estimated concentration of 38 μg m^?3, it is likely that the limit value will not be exceeded for three years in a row. The limit value for the daily average PM₁₀ concentration is equivalent to an annual average of about 32 μg m^?3. This threshold is unlikely to be exceeded for three years in a row, when an annual average concentration of 29 μg m^?3 is estimated. Interannual variations in concentrations of NO₂ and PM₁₀ are linked to large-scale meteorological fluctuations. Therefore, similar results can be expected for other European countries.     

Testing model accuracy measures according to the EU directives—examples using the chemical transport model REM-CALGRID

The paper presents a comprehensive model evaluation focusing on the meaning and shortcomings of accuracy measures used to determine model quality according to European Union (EU) directives on air quality. European wide simulations employing the chemical transport model REM-CALGRID for the year 2002 were compared with O₃, NO₂, SO₂ and PM₁₀ observations of the German measurement network.The EU model quality objective, which is based on maximum relative errors, tends to penalise (i) the overestimation of very low measured concentrations in the case of annual averages and (ii) the underestimation of extremely high measured concentrations in the case of short-term values. As a more robust alternative, a model accuracy measure is presented, which corresponds to the allowed number of exceedances of the corresponding short-term air quality limit values.The influence of the spatial heterogeneity of the observations in relation to the spatial resolution of the model is investigated by spatial averaging of observation data. Because of this heterogeneity, any model with a 25 km resolution would fail to simulate about 20% of all NO₂ and SO₂ stations and 5–10% of all O₃ and PM₁₀ stations in Germany according to the EU model quality objectives for short-term averages.     

What are the sources and conditions responsible for exceedences of the 24 h PM10 limit value (50 μg m−3) at a heavily trafficked London site?

The European Union has set limit values for PM₁₀ to be met in 2005. At Marylebone Road, London, where the traffic is heavy, the daily limit value of 50 μg m⁻³ is exceeded more than 35 times a year. A total of 185 days with daily PM₁₀ concentrations exceeding the limit value of 50 μg m⁻³ measured between January 2002 and December 2004 (data capture of 89.5%) are discussed in this paper. These exceedences were more frequent in early spring and in autumn. Concentrations have been disaggregated into regional, urban (background) and local (street) contributions. Most of the episodes of gravimetric PM₁₀ above the limit value were associated with a high regional background and very often the regional contribution dominated the PM₁₀ mass. The secondary aerosol (especially the particulate nitrate) made a major contribution to the PM₁₀ load. These situations were frequently observed when air masses came from the European mainland (showing that both emissions from the UK and other EU countries contributed to the exceedences), and less frequently with maritime air masses that have stagnated over the UK (showing that emissions from the UK alone less frequently contributed to the high regional background). However, the higher frequency of episodes breaching the limit value at the roadside site than at the rural site and the higher frequency of PM₁₀ concentrations above the limit value on weekdays show that the high regional contributions are additional to local and urban emissions. Local emissions mainly due to traffic were the second important contributor to the exceedences, while the contribution of the urban background of London was less important than the local emissions and the regional background. Applying the pragmatic mass closure model of Harrison et al. [2003. A pragmatic mass closure model for airborne particulate matter at urban background and roadside sites. Atmospheric Environment 37, 4927–4933], revealed that the regional aerosol is comprised very largely of ammonium nitrate and sulphate and secondary organic aerosol. Findings suggest that international abatement of secondary aerosol precursors may be the most effective measure to fulfil the requirements of the European Directive 1999/30/CE by lowering the regional background.     

Elemental composition of airborne particulate matter in the multi-impacted urban area of Thessaloniki,Greece

Ambient concentrations of PM₁₀ and their elemental composition in the multi-impacted area of Thessaloniki, N. Greece is presented in this study. High concentrations of PM₁₀ were observed, with 80% exceedances of the proposed daily limit of 50 μg m⁻³. The elemental concentrations were similar to the levels observed in moderately polluted urban areas. Spatial and temporal variation of particle mass and elemental concentrations as well as the influence of meteorological conditions were examined. The examined elements were characterised with respect to their origin from natural or anthropogenic emissions on the basis of crustal and marine enrichment factors. Factor analysis of elemental composition pattern and elemental ratios in PM₁₀ were also used to identify possible pollution source-types.     

PM10 concentration levels at an urban and background site in Cyprus: The impact of urban sources and dust storms

Air quality in Cyprus is influenced by both local and transported pollution, including desert dust storms. We examined PM₁₀ concentration data collected in Nicosia (urban representative) from April 1, 1993, through December 11, 2008, and in Ayia Marina (rural background representative) from January 1, 1999, through December 31, 2008. Measurements were conducted using a Tapered Element Oscillating Micro-balance (TEOM). PM₁₀ concentrations, meteorological records, and satellite data were used to identify dust storm days. We investigated long-term trends using a Generalized Additive Model (GAM) after controlling for day of week, month, temperature, wind speed, and relative humidity. In Nicosia, annual PM₁₀ concentrations ranged from 50.4 to 63.8 μg/m³ and exceeded the EU annual standard limit enacted in 2005 of 40 μg/m³ every year. A large, statistically significant impact of urban sources (defined as the difference between urban and background levels) was seen in Nicosia over the period 2000–2008, and was highest during traffic hours, weekdays, cold months, and low wind conditions. Our estimate of the mean (standard error) contribution of urban sources to the daily ambient PM₁₀ was 24.0 (0.4) μg/m³. The study of yearly trends showed that PM₁₀ levels in Nicosia decreased from 59.4 μg/m³ in 1993 to 49.0 μg/m³ in 2008, probably in part as a result of traffic emission control policies in Cyprus. In Ayia Marina, annual concentrations ranged from 27.3 to 35.6 μg/m³, and no obvious time trends were observed. The levels measured at the Cyprus background site are comparable to background concentrations reported in other Eastern Mediterranean countries. Average daily PM₁₀ concentrations during desert dust storms were around 100 μg/m³ since 2000 and much higher in earlier years. Despite the large impact of dust storms and their increasing frequency over time, dust storms were responsible for a small fraction of the exceedances of the daily PM₁₀ limit.

ImplicationsThis paper examines PM₁₀ concentrations in Nicosia, Cyprus, from 1993 to 2008. The decrease in PM₁₀ levels in Nicosia suggests that the implementation of traffic emission control policies in Cyprus has been effective. However, particle levels still exceeded the European Union annual standard, and dust storms were responsible for a small fraction of the daily PM₁₀ limit exceedances. Other natural particles that are not assessed in this study, such as resuspended soil and sea salt, may be responsible in part for the high particle levels.     

Study on ambient concentrations of PM10, PM10–2.5, PM2.5 and gaseous pollutants. Trace elements and chemical speciation of atmospheric particulates

This study provides the first comprehensive report on mass concentrations of particulate matter of various sizes, inorganic and organic gas concentrations monitored at three sampling sites in the city of Palermo (Sicily, Italy). It also provides information on the water-soluble species and trace elements. A total of 2054 PM₁₀ (1333) and PM_2.5 (721) daily measurements were collected from November 2006 to February 2008. The highest mass concentrations were observed at the urban stations, average values being about two times higher than those at the suburban (control) site. Time variations in PM₁₀ and also PM_10–2.5 were observed at the urban stations, the highest concentrations being measured in autumn and winter. CO, NOx, NO₂, benzene, toluene and o-xylene concentrations peaked in autumn and winter, a pattern similar to those recorded for PM₁₀ and PM_10–2.5 mass levels, indicating the importance of traffic emissions in urban air pollution. 91% and 51% of the benzene measurements exceeded the limit of 5 μg m^?3 at the two urban monitoring sites. Trace elements (As, Ba, Cr, Cu, Mo, Pb, Sb) suspected of being introduced into the atmosphere mainly by anthropogenic activities, were highly enriched with respect to local soil. Results indicate that a large fraction of PM₁₀ (31–47% in weight) and PM_2.5 (29% in weight) is made up of water-soluble ions. Ammonium sulphate and nitrate particles accounted for 14–29 wt% of particulate matter mass concentrations. Crustal and marine components, combined, account for 41% and 49% in PM_2.5 and PM₁₀, respectively. The calculated deficits in Cl^- and NH₄⁺ ions suggest that a proportion of these ions are lost, via the formation of gaseous NH₄Cl or HCl and NH₃.     

An empirical model for predicting urban roadside nitrogen dioxide concentrations in the UK

An annual mean concentration of 40 μg m⁻³ has been proposed as a limit value within the European Union Air Quality Directives and as a provisional objective within the UK National Air Quality Strategy for 2010 and 2005, respectively. Emissions reduction measures resulting from current national and international policies are likely to deliver significant reductions in emissions of oxides of nitrogen from road traffic in the near future. It is likely that there will still be exceedances of this target value in 2005 and in 2009 if national measures are considered in isolation, particularly at the roadside. It is envisaged that this `policy gap’ will be addressed by implementing local air quality management to reduce concentrations in locations that are at risk of exceeding the objective. Maps of estimated annual mean NO₂ concentrations in both urban background and roadside locations are a valuable resource for the development of UK air quality policy and for the identification of locations at which local air quality management measures may be required. Maps of annual mean NO₂ concentrations at both background and roadside locations for 1998 have been calculated using modelling methods, which make use of four mathematically straightforward, empirically derived linear relationships. Maps of projected concentrations in 2005 and 2009 have also been calculated using an illustrative emissions scenario. For this emissions scenario, annual mean urban background NO₂ concentrations in 2005 are likely to be below 40 μg m⁻³, in all areas except for inner London, where current national and international policies are expected to lead to concentrations in the range 40–41 μg m⁻³. Reductions in NO_x emissions between 2005 and 2009 are expected to reduce background concentrations to the extent that our modelling results indicate that 40 μg m⁻³ is unlikely to be exceeded in background locations by 2009. Roadside NO₂ concentrations in urban areas in 2005 and 2009 are expected to be significantly higher than in background locations. 21% of urban major road links are expected to have roadside NO₂ greater than or equal to 40 μg m⁻³ in 2005 for our illustrative emissions scenario. The continuing downward trend in traffic emissions is likely to further reduce the number of links exceeding this value by 2009, with about 6% of urban major road links predicted to have concentrations higher than 40 μg m⁻³. The majority of these links are in the London area. The remaining links are generally confined to the most heavily trafficked roads in other big cities.     

Assessment of ambient air quality in the port of Naples

Two experimental monitoring campaigns were carried out in 2012 to investigate the air quality in the port of Naples, the most important in southern Italy for traffic of passengers and one of the most important for goods. Therefore, it represents an important air pollution source located close to the city of Naples. The concentrations of sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and BTEX (benzene, toluene, ethylbenzene, and xylenes) in the air were measured at 15 points inside the Naples port area through the use of passive samplers. In addition, a mobile laboratory was positioned in a fixed point inside the port area to measure continuous concentration of pollutants together with particulate matter, ambient parameters, and wind direction and intensity. The pollution levels monitored were compared with those observed in the urban area of Naples and in other Mediterranean ports. Even though the observation time was limited, measured concentrations were also compared with limit values established by European legislation. All the measured pollutants were below the limits with the exception of nitrogen dioxide: its average concentration during the exposition time exceeded the yearly limit value. A spatial analysis of data, according to the measured wind direction and intensity, provided information about the effects that ship emissions have on ambient air quality in the port area. The main evidence indicates that ship emissions influence sulfur dioxide concentration more than any other pollutants analyzed.

Implications: Two monitoring campaigns were carried out to measure BTEX, SO₂, NO₂, and PM₁₀ (particulate matter with an aerodynamic diameter <10 μm) air concentrations in the port of Naples. NO₂ hourly average and PM₁₀ daily average comply with European legislative standards. Spatial variation of pollutants long the axis corresponding to the prevailing wind direction seems to indicate a certain influence of ship emissions for SO₂. For NO₂ and PM₁₀, a correlation between concentrations in the harbor and those measured by the air quality monitoring stations sited in the urban area of Naples was observed, indicating a possible contribution of the near road traffic to the air pollution in the port of Naples.     

Characterization of summertime coarse particulate matter in the Desert Southwest—Arizona,USA

A year-long study was conducted in Pinal County, AZ, to characterize coarse (2.5 – 10 μm aerodynamic diameter, AD) and fine (< 2.5 μm AD) particulate matter (PMc and PMf, respectively) to further understand spatial and temporal variations in ambient PM concentrations and composition in rural, arid environments. Measurements of PMc and PMf mass, ions, elements, and carbon concentrations at one-in-six day resolution were obtained at three sites within the region. Results from the summer of 2009 and specifically the local monsoon period are presented.

The summer monsoon season (July – September) and associated rain and/or high wind events, has historically had the largest number of PM₁₀ NAAQS exceedances within a year. Rain events served to clean the atmosphere, decreasing PMc concentrations resulting in a more uniform spatial gradient among the sites. The monsoon period also is characterized by high wind events, increasing PMc mass concentrations, possibly due to increased local wind-driven soil erosion or transport. Two PM₁₀ NAAQS exceedances at the urban monitoring site were explained by high wind events and can likely be excluded from PM₁₀ compliance calculations as exceptional events. At the more rural Cowtown site, PM₁₀ NAAQS exceedances were more frequent, likely due to the impact from local dust sources.

PM mass concentrations at the Cowtown site were typically higher than at the Pinal County Housing and Casa Grande sites. Crustal material was equal to 52-63% of the PMc mass concentration on average. High concentrations of phosphate and organic carbon found at the rural Cowtown were associated with local cattle feeding operations. A relatively high correlation between PMc and PMf (R²?=?0.63) indicated that the lower tail of the coarse particle fraction often impacts the fine particle fraction, increasing the PMf concentrations. Therefore, reductions in PMc sources will likely also reduce PMf concentrations, which also are near the value of the 24-hr PM_2.5 NAAQS.

Implications: In the desert southwest, summer monsoons are often associated with above average PM₁₀ (<10 μm AD) mass concentrations. Competing influences of monsoon rain and wind events showed that rain suppresses ambient concentrations while high wind increase them. In this region, the PMc fraction dominates PM₁₀ and crustal sources contribute 52-63% to local PMc mass concentrations on average. Cattle feedlot emissions are also an important source and a unique chemical signature was identified for this source. Observations suggest monsoon wind events alone cannot explain PM₁₀ NAAQS exceedances, thus requiring these values to remain in compliance calculations rather than being removed as exceptional wind events.     

A method to estimate the distribution of various fractions of PM10 in ambient air in the Netherlands

Eight rules based on measurements, model calculations, additional deductions and expert judgement have been devised for use in estimating the distribution and sources of various fractions of PM₁₀ in the Netherlands. As some of the underlying assumptions to these rules are debatable, they can be best characterized as “rules of thumb”. A brief rationale is given for each rule. Using these rules it is concluded that a previous expert judgement of a contribution of 20% from Dutch sources to PM₁₀ levels in the Netherlands is probably too low. Different values for the national contribution to the ambient PM₁₀ levels in the Netherlands have been evaluated. A contribution of 40–45% to PM₁₀ levels from Dutch sources is shown to meet two decisive criteria: (1) a reasonable ratio of PM₁₀ originating from national and foreign sources and (2) a reasonable ratio of the fine and coarse fractions of PM₁₀. Such a contribution also agrees with available data. This study shows that a higher national contribution to the ambient PM₁₀ levels implies a larger share of local emissions of coarse particles >2.5 μm than previously estimated. It appears that the original concept of a “blanket” of homogeneous PM₁₀ concentrations covering the Netherlands, a useful concept to describe the occurrence of shallow concentration gradients on geographical scales smaller than the country as a whole, has turned out to be more of a “patchwork quilt”. Although the measured concentration gradients are low (<20%), probably because the distribution of emission sources in a densely populated country like the Netherlands is fairly homogeneous, the chemical composition of PM₁₀ may differ spatially due to the contribution of local sources emitting aerosols in the coarser fraction of PM₁₀.     

The effects of congestions tax on air quality and health

The “Stockholm Trial” involved a road pricing system to improve the air quality and reduce traffic congestion. The test period of the trial was January 3–July 31, 2006. Vehicles travelling into and out of the charge cordon were charged for every passage during weekdays. The amount due varied during the day and was highest during rush hours (20 SEK = 2.2 EUR, maximum 60 SEK per day). Based on measured and modelled changes in road traffic it was estimated that this system resulted in a 15% reduction in total road use within the charged cordon. Total traffic emissions in this area of NO_x and PM10 fell by 8.5% and 13%, respectively. Air quality dispersion modelling was applied to assess the effect of the emission reductions on ambient concentrations and population exposure. For the situations with and without the trial, meteorological conditions and other emissions than from road traffic were kept the same. The calculations show that, with a permanent congestion tax system like the Stockholm Trial, the annual average NO_x concentrations would be lower by up to 12% along the most densely trafficked streets. PM10 concentrations would be up to 7% lower. The limit values for both PM10 and NO₂ would still be exceeded along the most densely trafficked streets. The total population exposure of NO_x in Greater Stockholm (35 × 35 km with 1.44 million people) is estimated to decrease with a rather modest 0.23 μg m^?3. However, based on a long-term epidemiological study, that found an increased mortality risk of 8% per 10 μg m^?3 NO_x, it is estimated that 27 premature deaths would be avoided every year. According to life-table analysis this would correspond to 206 years of life gained over 10 years per 100 000 people following the trial if the effects on exposures would persist. The effect on mortality is attributed to road traffic emissions (likely vehicle exhaust particles); NO_x is merely regarded as an indicator of traffic exposure. This is only the tip of the ice-berg since reductions are expected in both respiratory and cardiovascular morbidity. This study demonstrates the importance of not only assessing the effects on air quality limit values, but also to make quantitative estimates of health impacts, in order to justify actions to reduce air pollution.     

An empirical approach for the prediction of daily mean PM10 concentrations

An empirical model has been devised to predict concentrations of PM₁₀ at background and roadside locations in London. Factors to calculate primary PM₁₀ and PM_2.5 concentrations are derived from annual mean NO_X, PM_2.5 and PM₁₀ measurements across London and south east England. These factors are used to calculate daily means for the primary and non-primary PM₁₀ fractions for the London area. The model accurately predicts daily mean PM₁₀ and EU Directive Limit values across a range of sites from kerbside to rural. Predictions of future PM₁₀ can be made using the expected reductions in secondary PM₁₀ and site specific annual mean NO_X predicted from emission inventories and dispersion modelling. The model suggests that the EU Directive Limit values will be exceeded close to many of London's busiest roads, and perhaps at central background sites should there be a repeat of 1996 meteorological conditions during 2005. A repeat of 1997 meteorology conditions during 2005 would lead to the EU Limit Value being exceeded alongside the busiest central London roads only. The model is applicable for London and south east England but the methodology could be applied elsewhere at a city or regional level. The model relies on the currently observed ratio between NO_X and PM₁₀. This ratio has remained constant over the last 4 years but might change in the future. The NO_X:PM₁₀ ratio derived from measurements and used in this model, implies that emission inventories might over estimate primary PM₁₀ by more than 50%.     

Quantification of Saharan dust contribution to PM10 concentrations over Italy during 2003–2005

Italy is frequently affected by Saharan dust intrusions, which result in high PM₁₀ concentrations in the atmosphere and can cause the exceedances of the PM₁₀ daily limits (50 μg m^?3) set by the European Union (EU/2008/50). The estimate of African dust contribution to PM₁₀ concentrations is therefore a key issue in air quality assessment and policy formulation. This study presents a first identification of Saharan dust outbreaks as well as an estimate of the African dust contribution to PM₁₀ concentrations during the period 2003–2005 over Italy. The identification of dust events has been carried out by looking at different sources of information such as monitoring network observations, satellite images, ground measurements of aerosol optical properties, dust model simulations and air mass backward trajectory analysis. The contribution of Saharan dust to PM₁₀ monthly concentrations has been estimated at seven Italian locations. The results are both spatially (with station) and temporally (with month and year) variable, as a consequence of the variability of the meteorological conditions. However, excluding the contribution of severe dust events (21st February 2004, 25th–28th September 2003, 23rd–27th March 2005), the monthly contribution of dust varies approximately between 1 μg m^?3 and 10 μg m^?3 throughout year 2005 and between 1 μg m^?3 and 8 μg m^?3 throughout year 2003. In 2004 the dust concentration is lower than 2003 and 2005 (<5 μg m^?3 at all sites). The reduction in the number of daily exceedances of the limit value (50 μg m^?3) after subtraction of the dust contribution is also calculated at each station: it varies with station between 20% and 50% in 2005 and between 5% and 25% in 2003 and 2004.     

Monitoring of dust emission on gravel roads: Development of a mobile methodology and examination of horizontal diffusion

Traffic-generated fugitive dust on gravel roads impairs visibility and deposits on the adjacent environment. Particulate matter smaller than 10 μm in diameter (PM₁₀) is also associated with human health problems. Dust emission strength depends on the composition of granular material, road moisture, relative humidity, local climate (precipitation, wind velocity, etc.), and vehicle characteristics.The objectives of this study were to develop a reliable and rapid mobile methodology to measure dust concentrations on gravel roads, evaluate the precision and repeatability of the methodology and correspondence with the currently used visual assessment technique. Downwind horizontal diffusion was studied to evaluate the risk of exceeding the maximum allowed particulate matter concentration in ambient air near gravel roads according to European Council Directive [European Council Directive 1999/30/EC of 22 April 1999 relating to limit values for sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter and lead in ambient air. Official Journal of the European Communities. L163/41.].A TSI DustTrak Aerosol Monitor was mounted on an estate car travelling along test sections treated with various dust suppressants. Measured PM₁₀ concentrations were compared to visual assessments performed at the same time. Airborne particles were collected in filters mounted behind the vehicle to compare the whole dust fraction with the PM₁₀ concentration. For measuring the horizontal diffusion, DustTraks were placed at various distances downwind of a dusty road section.The mobile methodology was vehicle and speed dependent but not driver dependent with pre-specified driving behaviours. A high linear correlation between PM₁₀ of different vehicles makes relative measurements of dust concentrations possible. The methodology gives continuous data series, mobility, and easy handling and provides fast, reliable and inexpensive measurements for estimating road conditions to make road maintenance more efficient.Good correlations between measured PM₁₀-values, visually assessed dust generation and dust collected in filters were obtained. PM₁₀ seems to be correlated to the whole dust fraction that impairs visibility on gravel roads.A decay in PM₁₀ concentration as a function of distance from the road was observed. Measured particles principally did not travel further than 45 m from the road. The risk of exceeding the PM₁₀ concentration stated in the EC-directive seems small.     

Extended effects of air pollution on cardiopulmonary mortality in Vienna

BackgroundCurrent standards for fine particulates and nitrogen dioxide are under revision. Patients with cardiovascular disease have been identified as the largest group which need to be protected from effects of urban air pollution.MethodsWe sought to estimate associations between indicators of urban air pollution and daily mortality using time series of daily TSP, PM₁₀, PM_2.5, NO₂, SO₂, O₃ and nontrauma deaths in Vienna (Austria) 2000–2004. We used polynomial distributed lag analysis adjusted for seasonality, daily temperature, relative humidity, atmospheric pressure and incidence of influenza as registered by sentinels.ResultsAll three particulate measures and NO₂ were associated with mortality from all causes and from ischemic heart disease and COPD at all ages and in the elderly. The magnitude of the effect was largest for PM_2.5 and NO₂. Best predictor of mortality increase lagged 0–7 days was PM_2.5 (for ischemic heart disease and COPD) and NO₂ (for other heart disease and all causes). Total mortality increase, lagged 0–14 days, per 10 μg m⁻³ was 2.6% for PM_2.5 and 2.9% for NO₂, mainly due to cardiopulmonary and cerebrovascular causes.ConclusionAcute and subacute lethal effects of urban air pollution are predicted by PM_2.5 and NO₂ increase even at relatively low levels of these pollutants. This is consistent with results on hospital admissions and the lack of a threshold. While harvesting (reduction of mortality after short increase due to premature deaths of most sensitive persons) seems to be of minor importance, deaths accumulate during 14 days after an increase of air pollutants. The limit values for PM_2.5 and NO₂ proposed for 2010 in the European Union are unable to prevent serious health effects.     

PM10 and PM2.5 concentrations in Central and Eastern Europe:: results from the Cesar study

Between November 1995 and October 1996, particulate matter concentrations (PM₁₀ and PM_2.5) were measured in 25 study areas in six Central and Eastern European countries: Bulgaria, Czech Republic, Hungary, Poland, Romania and Slovak Republic. To assess annual mean concentration levels, 24-h averaged concentrations were measured every sixth day on a fixed urban background site using Harvard impactors with a 2.5 and 10 μm cut-point. The concentration of the coarse fraction of PM₁₀ (PM_10−2.5) was calculated as the difference between the PM₁₀ and the PM_2.5 concentration. Spatial variation within study areas was assessed by additional sampling on one or two urban background sites within each study area for two periods of 1 month. QA/QC procedures were implemented to ensure comparability of results between study areas. A two to threefold concentration range was found between study areas, ranging from an annual mean of 41 to 98 μg m⁻³ for PM₁₀, from 29 to 68 μg m⁻³ for PM_2.5 and from 12 to 40 μg m⁻³ for PM_10−2.5. The lowest concentrations were found in the Slovak Republic, the highest concentrations in Bulgaria and Poland. The variation in PM₁₀ and PM_2.5 concentrations between study areas was about 4 times greater than the spatial variation within study areas suggesting that measurements at a single sampling site sufficiently characterise the exposure of the population in the study areas. PM₁₀ concentrations increased considerably during the heating season, ranging from an average increase of 18 μg m⁻³ in the Slovak Republic to 45 μg m⁻³ in Poland. The increase of PM₁₀ was mainly driven by increases in PM_2.5; PM_10−2.5 concentrations changed only marginally or even decreased. Overall, the results indicate high levels of particulate air pollution in Central and Eastern Europe with large changes between seasons, likely caused by local heating.     

Influence of boundary conditions on CMAQ simulations over the Iberian Peninsula

The influence of chemical boundary conditions (BC) on the response of the Community Multiscale Air Quality (CMAQ) model over the Iberian Peninsula was investigated in this study. Three strategies to supply boundary conditions in the context of the Integrated Assessment Modelling System for the Iberian Peninsula (SIMCA) were tested. Alternative methods consist in providing BC from (1) fixed, time-independent, concentration profiles, (2) concentrations predicted in a CMAQ mother domain (48 km, 1 h resolution) and (3) concentration values from the GEOS-Chem chemical-transport global model (2 × 2.5°, 3 h resolution). High resolution (3 km) simulated concentrations of the main pollutants (NO₂, NO, SO₂, O₃, PM₁₀ and PM_2.5) were compared through a comprehensive statistical analysis including observational data from 165 monitoring stations all over the Iberian Peninsula. It was found that model sensitivity to BC for nitrogen and sulphur oxides was limited, being restricted to the vicinity of model boundaries. However, significant domain-wide differences were found when modelling ozone and PM depending on the BC provided to run the tests. Although model performance was affected by spatial and seasonal factors, the results indicate that model-derived, dynamic BC improved CMAQ predictions when compared to those based on static concentrations prescribed in the boundaries. Aggregated statistics suggest that the GEOS-Chem produced the best results for O₃ and PM_2.5 while NO₂ and PM₁₀ were slightly better predicted under the CMAQ nesting approach. Besides the statistical evaluation some other relevant issues in the context of Integrated Assessment Modelling (IAM) are discussed to gain a better insight into the suitability of the methods analyzed and limitations of downscaling methods. Despite being useful to get a better understanding of the role of BC in SIMCA, this study contributed to highlight model deficiencies and therefore to point out future research needs to improve IAM activities in the Iberian Peninsula.     

Air pollution at the Bily Kriz mountains in the Czech Republic

An evaluation of air pollution at the Bily Kriz mountains in the Czech Republic is given. Annual daily concentrations of sulphur dioxide (SO₂), nitrogen oxides (NO_x), particulate matter of size 10 mm (PM₁₀) and ozone (O₃) measured in the years 1994–2000 are presented. Air pollution at Bily Kriz is assessed with the reference to the European Union Directives and the standards adopted by the Czech Republic. In general, the concentrations of air pollutants were lower in 1996 for ozone and decreased for SO₂, NO_x and PM₁₀ from 1994. The daily values of SO₂ and PM₁₀ exceeded the European Union limits in approximately 0.0% and 5.5% of cases, respectively. The values of ozone exceeded the limits for the considered period.     

Speciation and diurnal variation of thoracic,fine thoracic and sub-micrometer airborne particulate matter at naturally ventilated office environments

Thoracic (PM₁₀), fine thoracic (PM_2.5) and sub-micrometer (PM₁) airborne particulate matter was sampled during day and night. In total, about 100 indoor and outdoor samples were collected for each fraction at ten different office environments. Energy-dispersive X-ray fluorescence spectrometry and ion chromatography were applied for the quantification of some major and minor elements and ions in the collected aerosols. During daytime, mass concentrations were in the ranges: 11–29, 8.1–24, and 6.6–18 μg m^?3, with averages of 20 ± 1, 15.0 ± 0.9, and 11.0 ± 0.8 μg m^?3, respectively. At night, mass concentrations were found to be significantly lower for all fractions. Indoor PM₁ concentrations exceeded the corresponding outdoor levels during office hours and were thought to be elevated by office printers. Particles with diameters between 1 and 2.5 μm and 2.5 and 10 μm were mainly associated with soil dust elements and were clearly subjected to distinct periods of settling/resuspension. Indoor NO₃^? levels were found to follow specific microclimatic conditions at the office environments, while daytime levels of sub-micrometer Cl^? were possibly elevated by the use of Cl-containing cleaning products. Indoor carbon black concentrations were sometimes as high as 22 μg m^?3 and were strongly correlated with outdoor traffic conditions.     

A semi-empirical model for urban PM10 concentrations,and its evaluation against data from an urban measurement network

We have developed a model for evaluating the mass-based concentrations of urban particulate matter. The basic model assumption is that local vehicular traffic is responsible for a substantial fraction of the street-level concentrations of both PM₁₀ and NO_x, either due to primary emissions or resuspension from street surfaces. The modelling system utilises the data from an air quality monitoring network in the Helsinki Metropolitan Area. We have determined linear relationships between the measured urban PM₁₀ data against those of NO_x in various urban surroundings, based on continuously measured hourly concentration values. The data was obtained from two stations in central Helsinki and one suburban station in the Helsinki Metropolitan Area during a period of 3 yr, from 1996 to 1998. The model also includes a treatment of the regional background concentrations, and resuspended particulate matter. The model performance was evaluated against the measured PM₁₀ data from the above-mentioned three stations and from two other stations, using data that was measured in 1999. We used two alternative model versions, one based on separate correlation parameters (PM₁₀ vs. NO_x) for each station, and another based on parameters averaged over the stations considered. We analysed the agreement between the measured and predicted hourly concentration time series, utilising the values of the fractional bias (FB) and the so-called index of agreement (IA). As expected, the model predicts relatively well the yearly mean concentrations of PM₁₀: the FB values range from −0.05 to +0.09. Model performance is also relatively good when predicting the yearly mean values that are classified separately for each hour of the day: the corresponding IA values range from 0.85 to 0.96. However, model performance is substantially worse in predicting the hourly time series of the year: the IA values using the station-specific parameters range from 0.46 to 0.65. The model was applied in evaluating the yearly average spatial concentration distribution of PM₁₀ in central Helsinki, based on the corresponding modelled NO_x concentrations. With re-evaluation of a few parameters that can be determined empirically, the model could be evaluated, and most probably applied, in other urban areas as well.