Urban Background Stations Research Articles

Analysis of concentrations trends and origins of PM10in selected European cities

Particulate matter is generated in many natural and anthropogenic processes and, therefore, taking part in chemical reactions and physical processes in the atmosphere could affect human health, climate, and natural environment. The dust, after emission to the atmosphere, remains there in a floating state to form an atmospheric aerosol with different properties – depending on the morphology, the fraction, shape, surface, and chemical composition of the particles. The chemical composition of particulate matter is heterogeneous and depends on the type of emission sources and the time of residence in the atmosphere. The contribution of individual types of sources in the total dust emission is different in European countries. The aim of the study was to analyze the concentrations of PM10 at urban background and traffic stations in the chosen 17 European cities. For this purpose, the data from the database of the European Environment Agency and Chief Inspectorate of Environmental Protection was used. The annual average concentrations of 10 and daily average concentrations of PM10 in 2014 will be presented to confirm that in the European cities there is a problem about high 10 concentrations, especially in Poland and other eastern countries. In the case of daily average 10 concentration, the highest concentrations of pollutants in the winter season suggests that for the low air quality in these cities the phenomenon of so- called low-stack-emissions from the municipal sector is responsible.

Antimony speciation as geochemical tracer for anthropogenic emissions of atmospheric particulate matter

The chemical composition of atmospheric particulate matter (PM) has been studied at the cities of Cordoba and Granada (South of Spain) between 2007 and 2013, considering urban background, traffic and industrial monitoring stations. The results of Principal Component Analysis (PCA) indicated that geochemical anomalies observed in the ambient air of Cordoba (mainly Cu, Zn, Pb and Cd) are closely related to the geochemical profile obtained from fugitive metallurgy emissions of brass industries. These findings have been confirmed performing an Sb speciation analysis of PM10 samples, which allowed to distinguish between Sb(III) and Sb(V). The percentage of Sb(V) in PM10 found in the traffic station of Granada was 64–69%. At Cordoba, the percentage of Sb(V) was found to be higher (73–77%) at both urban background and traffic stations, indicating a possible second source of Sb in the PM of this city. The PM10 samples from the industrial station of Cordoba showed a 85–86% of Sb(V). A similar percentage (84–88%) of Sb(V) was found for the fugitive emissions of the brass industries, confirming this industrial source of Sb. These results show that Sb speciation can be a useful geochemical tracer to identify anthropogenic sources (traffic and industrial) emissions of PM.

Characterization of hydrocarbons in aerosols at a Mediterranean city with a high density of palm groves.

Samples of PM1 and PM10 were collected for 1year at an urban background station in the city of Elche (southeastern Spain) and analyzed to determine the content of n-alkanes and polycyclic aromatic hydrocarbons (PAHs). A few samples were also gathered at a second sampling point established at one of the several palm tree gardens of the city in order to evaluate the influence of biogenic emissions on the urban levels of n-alkanes. Diagnostic parameters obtained for aliphatic hydrocarbons (carbon maximum number (C max), carbon preference index (CPI), and wax n-alkane content (%WNA)) revealed a higher contribution of biogenic n-alkanes in PM10 than in PM1. Moreover, the values of %WNA indicated that the levels of n-alkanes in Elche were more affected by emissions from terrestrial vegetation than in other urban areas, particularly in the palm tree grove location (%WNA=29 for PM10). PAH diagnostic ratios pointed to traffic as the main anthropogenic source of hydrocarbons in Elche, with predominance of diesel versus gasoline vehicle emissions. The average levels of total PAHs (~1ngm(-3)) were noticeably lower than the values registered at other urban areas in Europe, most likely because emissions from other sources are scarce. Both aliphatic and aromatic hydrocarbons showed higher levels in the cold season due to the lower atmospheric dispersion conditions, the increase in traffic exhaust emissions, and the lower ambient temperatures that reduce the evaporation of semivolatile species.

Impact of WRF model PBL schemes on air quality simulations over Catalonia, Spain

Here we analyze the impact of four planetary boundary-layer (PBL) parametrization schemes from the Weather Research and Forecasting (WRF) numerical weather prediction model on simulations of meteorological variables and predicted pollutant concentrations from an air quality forecast system (AQFS). The current setup of the Spanish operational AQFS, CALIOPE, is composed of the WRF-ARW V3.5.1 meteorological model tied to the Yonsei University (YSU) PBL scheme, HERMES v2 emissions model, CMAQ V5.0.2 chemical transport model, and dust outputs from BSC-DREAM8bv2. We test the performance of the YSU scheme against the Assymetric Convective Model Version 2 (ACM2), Mellor-Yamada-Janjic (MYJ), and Bougeault-Lacarrère (BouLac) schemes. The one-day diagnostic case study is selected to represent the most frequent synoptic condition in the northeast Iberian Peninsula during spring 2015; regional recirculations. It is shown that the ACM2 PBL scheme performs well with daytime PBL height, as validated against estimates retrieved using a micro-pulse lidar system (mean bias=−0.11km). In turn, the BouLac scheme showed WRF-simulated air and dew point temperature closer to METAR surface meteorological observations. Results are more ambiguous when simulated pollutant concentrations from CMAQ are validated against network urban, suburban, and rural background stations. The ACM2 scheme showed the lowest mean bias (−0.96μgm−3) with respect to surface ozone at urban stations, while the YSU scheme performed best with simulated nitrogen dioxide (−6.48μgm−3). The poorest results were with simulated particulate matter, with similar results found with all schemes tested.

Evaluation of an urban modelling system against three measurement campaigns in London and Birmingham

The results of three measurement campaigns are presented in this study. The campaigns have been undertaken at an urban roadside site in London, for more than a year and three months in 2003–2004 and for a year in 2008, and at an urban background site in Birmingham, U.K, for about four months in 2002. The concentrations of PM2.5, PM10, NOx and NO2 were predicted using the roadside dispersion model CAR-FMI, combined with a national U.K. emission model, a meteorological pre-processor, and measured values at urban background stations. The agreement of the predicted and measured hourly and daily time-series has been assessed statistically for all of the campaigns and pollutants. For instance, the Indices of Agreement (IA) in all the campaigns ranged from 0.68 to 0.78, 0.87, from 0.70 to 0.80, and from 0.61 to 0.83 for PM2.5, PM10, NOx and NO2, respectively. However, in case of the campaigns in London, both the PM fractions and the nitrogen oxide concentrations were under-predicted. The model performance in terms of atmospheric stability, wind speeds and other factors was analysed, and reasons for the disagreement of predictions and measurements have been discussed. It is useful to consider the model performance statistics for several measurement campaigns simultaneously as some of the results were found to be specific only to one or two campaigns. The spatial concentration distribution of NOx in London for 2008 has also been presented.

BAERLIN2014 – the influence of land surface types on and the horizontal heterogeneity of air pollutant levels in Berlin

Abstract. Urban air quality and human health are among the key aspects of future urban planning. In order to address pollutants such as ozone and particulate matter, efforts need to be made to quantify and reduce their concentrations. One important aspect in understanding urban air quality is the influence of urban vegetation which may act as both emitter and sink for trace gases and aerosol particles. In this context, the "Berlin Air quality and Ecosystem Research: Local and long-range Impact of anthropogenic and Natural hydrocarbons 2014" (BAERLIN2014) campaign was conducted between 2 June and 29 August in the metropolitan area of Berlin and Brandenburg, Germany. The predominant goals of the campaign were (1) the characterization of urban gaseous and particulate pollution and its attribution to anthropogenic and natural sources in the region of interest, especially considering the connection between biogenic volatile organic compounds and particulates and ozone; (2) the quantification of the impact of urban vegetation on organic trace gas levels and the presence of oxidants such as ozone; and (3) to explain the local heterogeneity of pollutants by defining the distribution of sources and sinks relevant for the interpretation of model simulations. In order to do so, the campaign included stationary measurements at urban background station and mobile observations carried out from bicycle, van and airborne platforms. This paper provides an overview of the mobile measurements (Mobile BAERLIN2014) and general conclusions drawn from the analysis. Bicycle measurements showed micro-scale variations of temperature and particulate matter, displaying a substantial reduction of mean temperatures and particulate levels in the proximity of vegetated areas compared to typical urban residential area (background) measurements. Van measurements extended the area covered by bicycle observations and included continuous measurements of O3, NOx, CO, CO2 and point-wise measurement of volatile organic compounds (VOCs) at representative sites for traffic- and vegetation-affected sites. The quantification displayed notable horizontal heterogeneity of the short-lived gases and particle number concentrations. For example, baseline concentrations of the traffic-related chemical species CO and NO varied on average by up to ±22.2 and ±63.5 %, respectively, on the scale of 100 m around any measurement location. Airborne observations revealed the dominant source of elevated urban particulate number and mass concentrations being local, i.e., not being caused by long-range transport. Surface-based observations related these two parameters predominantly to traffic sources. Vegetated areas lowered the pollutant concentrations substantially with ozone being reduced most by coniferous forests, which is most likely caused by their reactive biogenic VOC emissions. With respect to the overall potential to reduce air pollutant levels, forests were found to result in the largest decrease, followed by parks and facilities for sports and leisure. Surface temperature was generally 0.6–2.1 °C lower in vegetated regions, which in turn will have an impact on tropospheric chemical processes. Based on our findings, effective future mitigation activities to provide a more sustainable and healthier urban environment should focus predominantly on reducing fossil-fuel emissions from traffic as well as on increasing vegetated areas.

Nucleation events at a coastal city during the warm period: Kerbside versus urban background measurements

Number size distributions of atmospheric aerosol particles were simultaneously measured at a kerbside and an urban background site in the city of Thessaloniki, Greece, from June to October 2009. New particle formation events were observed ca. 27% of the days at the urban kerbside site and 29% of the days at the urban background site. In almost all the cases the events started between 10:00 and 12:00, and continued for several hours. The total number concentration (TNC) of the particles having diameters from 10 to ca. 500 nm during the events increased from 1.4 × 104 to 6.5 × 104 #/cm3 at the urban kerbside site, and from 0.2 × 104 to 2.4 × 104 #/cm3 at the urban background site. At the urban kerbside site, 9% of the days exhibited class I events (i.e., events followed by a clear growth of the newly formed particles), 10% class II (i.e., events during which the concentration of nucleation mode particles were high but their growth was not continuous), 67% were characterised as non-event days, and 14% of the days exhibited no clear particle formation pattern (undefined). At the urban background site, 15% of the days were classified as class I, 5% as class II, 75% of the days showed no nucleation, whereas only 5% of the days were undefined. While the fraction of event days (both class I and class II) at both sites was similar (ca. 20%), the higher fraction of class I events observed at Eptapyrgio can be attributed to the cleaner environment of the urban background site that allows better identification of the particle concentration increase. The nucleation bursts show a similar pattern at both sites, with the newly formed particles reaching a final size of ca. 80–100 nm. A distinct difference between the two stations was that the smallest particles observed during the new-particle formation events had a diameter of ca. 10 nm (i.e., the smallest particles we could observe) at the kerbside site and ca. 20 nm at the urban background site. This is an indication that the new particles observed at the urban background station are formed elsewhere and are transported to the site. Estimated concentrations of H2SO4 using a proxy model, suggest that these are high enough to explain the nucleation events despite that the available aerosol surface was high, especially at the urban kerbside site.

Air pollution is associated with primary health care visits for asthma in Sweden: A case-crossover design with a distributed lag non-linear model

BackgroundAir pollution can increase the symptoms of asthma and has an acute effect on the number of emergency room visits and hospital admissions because of asthma, but little is known about the effect of air pollution on the number of primary health care (PHC) visits for asthma. ObjectiveTo investigate the association between air pollution and the number of PHC visits for asthma in Scania, southern Sweden. MethodsData on daily PHC visits for asthma were obtained from a regional healthcare database in Scania, which covers approximately half a million people. Air pollution data from 2005 to 2010 were obtained from six urban background stations. We used a case-crossover study design and a distributed lag non-linear model in the analysis. ResultsThe air pollution levels were generally within the EU air quality guidelines. The mean number of daily PHC visits for asthma was 34. The number of PHC visits increased by 5% (95% confidence interval (CI): 3.91–6.25%) with every 10µg m−3 increase in daily mean NO2 lag (0–15), suggesting that daily air pollution levels are associated with PHC visits for asthma. ConclusionEven though the air quality in Scania between 2005 and 2010 was within EU's guidelines, the number of PHC visits for asthma increased with increasing levels of air pollution. This suggests that as well as increasing hospital and emergency room visits, air pollution increases the burden on PHC due to milder symptoms of asthma.

A wavelet-based approach applied to suspended particulate matter time series in Portugal

This study intends to analyse the particulate matter (PM) levels in Portugal (mainland and islands) throughout a 3-year period. Although a decreasing trend has been observed, the WHO guidelines for the PM10 and PM2.5 annual mean concentrations have been exceeded in all monitoring stations. Most inland urban, rural and suburban sites follow a pronounced seasonal variation with much higher values in winter than in summer. Lower levels and a weak seasonal variability were registered in the two urban background stations of Madeira Island, which are permanently under the influence of clean air masses over the Atlantic. Receiving long-range transported pollution, rural stations located in mountain sites presented an opposite seasonal pattern, with higher levels in summer. Diurnal profiles were also analysed and compared between stations. A mining process was also carried out, consisting in the application of multi-scale wavelet transforms, data pattern identification using cluster analysis and examination of the contribution to the total variance/covariance of the time series per wavelet scale for all stations. Groups of stations exhibiting similar variance/covariance profiles were identified. One group contains urban and rural stations with diurnal and daily time scales. Urban background stations located in the island of Madeira constitute another cluster, corresponding to higher wavelet scales (lower periodicity phenomena). One traffic station in the Oporto metropolitan area was grouped with a suburban/industrial station of central Portugal, suggesting the need for reclassification in what concerns the type of environmental influence.

OZONE AND OZONE PRECURSORS IN URBAN ATMOSPHERE

Monitoring of atmospheric air at an urban background station in the city of Varna, Bulgaria between 2007 and 2014 to evaluate the levels of the secondary pollutants О3 and its precursors – NO, NO2, NMHC and CO. Annual, monthly and diurnal variations were studied. The results show that О3 and the precursors do not exceed the norms that threaten human health. As compared with the start of the monitoring, the О3 concentrations have risen from 32.22 to 52.04 µg/m3 and the differences have high statistical significance (0.025 ≤ Р ≤ 0.05). The maximum concentrations of the secondary pollutant О3 are achieved several hours after the peak precursor levels. Measures are proposed for reduction of the emissions of the О3 precursors with the aim to reduce the concentrations of the secondary pollutant in the lower atmosphere.

Performance comparison of two thermodenuders in Volatility Tandem DMA measurements

Volatility Tandem Differential Mobility Analysers (VTDMAs) are widely used for determining the volatile and refractory fractions and thus the mixing state of aerosols particles. A three-channel VTDMA consisting of two thermodenuders (TDs) with distinct designs (i.e., the NanoTD, having a straight tube design, and a coiled TD; cTD) and a by-pass line was built and fully characterized. Both TDs were tested using laboratory-generated aerosol particles (single compound and core–shell particles) as well as atmospheric aerosols observed at an urban background station. The NanoTD exhibited high particle penetration efficiency and negligible thermophoretic losses, making it advantageous for ultrafine particle analysis, especially in environments with low particle concentration. The cTD allows longer particle residence time for the same flow rate, resulting in higher particle volatilization in some cases. Higher particle losses in this TD, both thermophoretic and diffusional, pose a limitation when dealing with low particle concentrations.The difference in the performance between the thermodenuders was only noticed at intermediate temperatures, at which particle volume loss becomes more pronounced. These temperatures vary among aerosols, since the volatilization rate depends on the chemical complexity and size of the particles sampled. Differences in the aerosol volume fraction remaining after heating with the two TD designs exhibited a maximum of 20% for single-compound particles and 12% for urban background aerosols. Measurements using core–shell particles yielded differences of up to 21% in particle volatilization, independently of particle size, when comparing the system using either of the two TD designs. Similar results were obtained with the two TD designs at higher operating temperatures (e.g., 230°C), indicating that at this temperature most of the material on the particles was evaporated.

Daily and seasonal variation of traffic related aerosol pollution in Thessaloniki, Greece, during the financial crisis

Airborne urban particulate and gaseous pollutants measurements were conducted at the kerbside of a busy road and at a nearby urban background site of Thessaloniki, Greece, during a winter and a summer period. The main objective was to observe how the financial crisis has affected the air quality in the city, compared to previous measurements. Compared to a study conducted in 2006, the current work suggests that although average concentrations at the traffic affected site remain higher that in the urban background station, the differences are much smaller than in the past. A number of observations suggest a scenario of decrease in traffic activity and increase in biomass burning for residential heating. On this basis, the results suggest that traffic may be less important as an air quality contributor in a financially hit city. On the contrary, domestic heating appears as a significant contributor and affects areas of the city that were earlier not being of environmental concern. Because of the impact of biomass burning in residential areas, exposure calculations are required to estimate whether traffic or biomass burning is the overall highest contributors to daily PM dosages that citizens of the city are exposed to.

Enhancements in nocturnal surface ozone at urban sites in the UK.

Analysis of diurnal patterns of surface ozone (O3) at multiple urban sites in the UK shows the occurrence of prominent nocturnal enhancements during the winter months (November-March). Whilst nocturnal surface ozone (NSO) enhancement events have been observed at other locations, this is the first time that such features have been demonstrated to occur in the UK and the second location globally. The observed NSO enhancement events in the UK were found to be so prevalent that they are clearly discernible in monthly diurnal cycles averaged over several years of data. Long-term (2000-2010) analysis of hourly surface ozone data from 18 urban background stations shows a bimodal diurnal variation during the winter months with a secondary nighttime peak around 0300 hours along with the primary daytime peak. For all but one site, the daily maxima NSO concentrations during the winter months exceeded 60 μg/m(3) on >20 % of the nights. The highest NSO value recorded was 118 μg/m(3). During the months of November, December, and January, the monthly averaged O3 concentrations observed at night (0300 h) even exceeded those observed in the daytime (1300 h). The analysis also shows that these NSO enhancements can last for several hours and were regional in scale, extending across several stations simultaneously. Interestingly, the urban sites in the north of the UK exhibited higher NSO than the sites in the south of the UK, despite their daily maxima being similar. In part, this seems to be related to the sites in the north typically having lower concentrations of nitrogen oxides.

Spatial outlier detection in the PM10 monitoring network of Normandy (France)

We consider hourly PM10 measurements from 22 monitoring stations located in Basse–Normandie and Haute–Normandie regions (France) and also in the neighboring regions. All considered monitoring stations are either urban background stations or rural ones. The paper focuses on the statistical detection of outliers of the hourly PM10 concentrations from a spatial point of view. The general strategy uses a jackknife type approach and is based on the comparison of the actual measurement with some robust spatial prediction. Two spatial predictions are considered: the first one is based on the median of the concentrations of the closest neighboring stations which directly consider weighted concentrations while the second one is based on kriging increments, instead of more traditional pseudo–innovations. The two methods are applied to the PM10 monitoring network in Normandy and are fully implemented by Air Normand (the official association for air quality monitoring in Haute–Normandie) in the Measurements Quality Control process. Some numerical results are provided on recent data from January 1, 2013 to May 31, 2013 to illustrate and compare the two methods.

Elemental composition and radical formation potency of PM10 at an urban background station in Germany in relation to origin of air masses

At an urban background station in Mülheim-Styrum, North Rhine Westphalia, Germany, a set of 75 PM10 samples was collected over a one year period, followed by analyses for mass, chemical composition and hydroxyl radical (OH) formation potency. Additionally, the origin of air masses for the sampling days was calculated by 48-h backward trajectories, subdivided into the four cardinal sectors. Significant lower PM10 mass concentrations were observed for summertime air masses from the west compared to the other seasons and cardinal sectors. For the OH formation potency higher values were detected if air masses originate from east and south, thus predominantly being of continental origin. From the elevated OH formation potencies in fall and winter a seasonal trend with low potencies in summers is assumed. Furthermore, source apportionment was performed by a positive matrix factor analysis, separating seven plausible factors which could be attributed to mineral dust, secondary nitrate, industry, non-exhaust traffic, fossil fuel combustion, marine aerosol and secondary aerosol factors. The intrinsic OH formation potency was found to be associated mainly with the fossil fuel combustion factor (45%) and industry factor (22%).

High-resolution air quality simulation over Europe with the chemistry transport model CHIMERE

Abstract. A modified version of CHIMERE 2009, including new methodologies in emissions modelling and an urban correction, is used to perform a simulation at high resolution (0.125° × 0.0625°) over Europe for the year 2009. The model reproduces the temporal variability of NO2, O3, PM10, PM2.5 better at rural (RB) than urban (UB) background stations, with yearly correlation values for the different pollutants ranging between 0.62 and 0.77 at RB sites and between 0.52 and 0.73 at UB sites. Also, the fractional biases (FBs) show that the model performs slightly better at RB sites than at UB sites for NO2 (RB = −33.9%, UB = −53.6%), O3 (RB = 20.1%, UB = 25.2%) and PM10 (RB = −5.50%, UB = −20.1%). The difficulties for the model in reproducing NO2 concentrations can be attributed to the general underestimation of NOx emissions as well as to the adopted horizontal resolution, which represents only partially the spatial gradient of the emissions over medium-size and small cities. The overestimation of O3 by the model is related to the NO2 underestimation and the overestimated O3 concentrations of the lateral boundary conditions. At UB sites, CHIMERE reproduces PM2.5 better than PM10. This is primarily the result of an underestimation of coarse particulate matter (PM) associated with uncertainties in secondary organic aerosol (SOA) chemistry and its precursor emissions (Po valley and Mediterranean basin), dust (south of Spain) and sea salt (western Europe). The results suggest that future work should focus on the development of national bottom-up emission inventories including a better account for semi-volatile organic compounds and their conversion to SOA, the improvement of the CHIMERE urban parameterization, the introduction into CHIMERE of the coarse nitrate chemistry and an advanced parameterization accounting for windblown dust emissions.

Shrinkage of Newly Formed Particles in an Urban Environment

New particle formation (NPF) significantly influences the number concentrations and size distributions of an atmospheric aerosol and is often followed by the rapid growth of the newly formed particles. Recently a reversal process leading to particle shrinkage was reported and was found to occur under specific atmospheric conditions, which are unfavourable for the growth of nucleated particles. In this study we present an analysis of particle shrinkage events following prior NPF at an urban background station in Prague, Czech Republic. The study is based on two-year measurements of particle number size distributions using Scanning Mobility Particle Size (SMPS). A total of 22 shrinkage events were identified and the vast majority of the events was observed in the spring and summer seasons. The determined shrinkage rates span the range from -2.5 to -12.5nm/h. During the most intensive events, the grown particles shrank back to the smallest measurable size of 10nm. The particle shrinkage was attributed to the evaporation of previously condensed volatile and semi-volatile species from the particulate phase to the gas phase. When analysing the dependence on meteorological conditions, the particle shrinkage was found to occur under peak global radiance intensity, which was gradually decreasing, or under a sharp drop of global radiance intensity. The shrinkage events were also related to high ambient temperature and low relative humidity. The occurrence of atmospheric mixing was found to promote particle shrinkage very effectively, because the decrease of vapour concentration due to changing atmospheric conditions is more rapid than the decrease of vapour concentration caused by lower photochemical activity due to a drop in solar radiation intensity.

Representativeness of air quality monitoring networks

The suitability of European networks to check compliance with air quality standards and to assess exposure of the population was investigated. An air quality model (URBIS) was applied to estimate and compare the spatial distribution of the concentration of nitrogen dioxide (NO2) in ambient air in four large cities. The concentrations calculated at the location of the monitoring stations, compared well with the concentrations measured at the stations indicating that the models worked well. Therefore the calculated concentration distributions were used as a proxy for the actual concentration distributions across the cities. The distributions of these proxy concentrations across the city populations was determined and cumulative population distribution curves were estimated. The calculated annual mean values at the monitoring network stations were located on the population distribution curves to estimate the fractions of the populations that the monitoring network stations represent. This macro scale procedure is used to evaluate which subgroups of the monitoring stations can be reliably used to decide on compliance or to estimate the concentration the population is exposed to. In addition, the CAR model and Computational Fluid Dynamics (CFD) models are used to investigate the effect of micro scale siting of the monitoring stations within the streets.The following observations were made:- Berlin and London networks cover the distribution of concentrations to which the population is exposed rather well, while Stuttgart and Barcelona have stations at sites with mainly the higher concentrations and the exposure is covered less well.- The networks in London and Berlin, with a substantial number of urban background stations, seem fit to monitor the average population exposure, contrary to those in Stuttgart and Barcelona with only a limited number of these stations.- The concentrations measured at street stations hardly reflect the calculated differences in street pollution between the cities. In Stuttgart the stations are, in line with the EU directive, placed in the most polluted streets, while in other cities there are no stations in the streets with the highest pollution levels.- The concentrations measured at street stations – particularly where buildings inhibit ventilation – are very sensitive to the exact location within the street. Different siting choices may have an effect that for NO2 could reach up to 10 μg/m3 in realistic conditions. Street stations, representing only a small urban area, are not suitable for characterising the exposure of the general population.It is important to note that epidemiological studies whether investigating short term-effects or those studying long-term effects are potentially affected by the issues raised in the paper. Long-term cumulative exposure estimates that are based rather uncritically on monitoring data may be biased if the stations are not representative. It is recommended to use models to support the interpretation and spatial extrapolation of the results of measurements in existing networks. The use of models also relaxes the need for station relocation in inadequate networks, which often would compromise trend analysis. It also relaxes the importance of exact or detailed, comprehensive, station classifications since all stations can be used in exposure assessments.

A quantitative estimation of the exhaust, abrasion and resuspension components of particulate traffic emissions using electron microscopy

The contribution of the three traffic-related components exhaust, abrasion, and resuspension to kerbside and urban background PM10 and PM1 levels was quantified based on the analysis of individual particles by scanning electron microscopy. A total of 160 samples was collected on 38 days between February and September 2009 at a kerbside and an urban background station in the urban/industrial Ruhr area (Germany). Based on size, morphology, chemical composition and stability under electron bombardment, the 111,003 particles studied in detail were classified into the following 14 particle classes: traffic/exhaust, traffic/abrasion, traffic/resuspension, carbonaceous/organic, industry/metallurgy, industry/power plants, secondary particles, (aged) sea salt, silicates, Ca sulfates, carbonates, Fe oxides/hydroxides, biological particles, and other particles. The traffic/exhaust component consists predominantly of externally mixed soot particles and soot internally mixed with secondary particles. The traffic/abrasion component contains all particles with characteristic tracer elements (Fe, Cu, Ba, Sb, Zn) for brake and tire abrasion. The traffic/resuspension component is defined by the mixing state and comprises all internally mixed particles with a high proportion of silicates or Fe oxides/hydroxides which contain soot or abrasion particles as minor constituent. In addition, silicates and Fe oxides/hydroxides internally mixed with chlorine and sulphur containing particles were also assigned to the traffic/resuspension component. The total contribution of traffic to PM10 was found to be 27% at the urban background station and 48% at the kerbside station, the corresponding values for PM1 are 15% and 39%. These values lie within the range reported in previous literature. The relative share of the different traffic components for PM10 at the kerbside station was 27% exhaust, 15% abrasion, and 58% resuspension (38%, 8%, 54% for PM1). For the urban background, the following relative shares were obtained for PM10: 22% exhaust, 22% abrasion and 56% resuspension (40%, 27%, 33% for PM1). Compared to previous publications we have observed a significantly lower portion of exhaust particles and a significantly higher portion of resuspension particles. The high abundance of resuspension particles underlines their significance for the observed adverse health effects of traffic emissions and for mitigation measures.

Cardiovascular and lung function in relation to outdoor and indoor exposure to fine and ultrafine particulate matter in middle-aged subjects

This cross-sectional study investigated the relationship between exposure to airborne indoor and outdoor particulate matter (PM) and cardiovascular and respiratory health in a population-based sample of 58 residences in Copenhagen, Denmark. Over a 2-day period indoor particle number concentrations (PNC, 10–300nm) and PM2.5 (aerodynamic diameter<2.5μm) were monitored for each of the residences in the living room, and outdoor PNC (10–280nm), PM2.5 and PM10 (aerodynamic diameter<10μm) were monitored at an urban background station in Copenhagen. In the morning, after the 2-day monitoring period, we measured microvascular function (MVF) and lung function and collected blood samples for biomarkers related to inflammation, in 78 middle-aged residents. Bacteria, endotoxin and fungi were analyzed in material from electrostatic dust fall collectors placed in the residences for 4weeks. Data were analyzed using linear regression with the generalized estimating equation approach. Statistically significant associations were found between indoor PNC, dominated by indoor use of candles, and lower lung function, the prediabetic marker HbA1c and systemic inflammatory markers observed as changes in leukocyte differential count and expression of adhesion markers on monocytes, whereas C-reactive protein was significantly associated with indoor PM2.5. The presence of indoor endotoxin was associated with lower lung function and expression of adhesion markers on monocytes. An inverse association between outdoor PNC and MVF was also statistically significant. The study suggests that PNC in the outdoor environment may be associated with decreased MVF, while PNC, mainly driven by candle burning, and bioaerosols in the indoor environment may have a negative effect on lung function and markers of systemic inflammation and diabetes.