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Abstract: Introduction: An analysis of the hourly SO2 pollution patterns with time can be a useful tool for policy makers and stakeholders in developing more effective local policies in relation to air quality as it facilitates a deeper understanding of concentrations and potential source apportionment. A detailed analysis of hourly inter-annual, seasonal and weekday-specific SO2 concentration patterns using data obtained from 6 cities involved in the Aphekom project was conducted. This type of analysis has been done for other pollutants but less so for SO2, and not in a systematic fashion for a number of European cities. Methods: Individual diurnal SO2 profiles and working weekday versus weekend specific 24-hr plots were generated using hourly SO2 measurements from a roadside and an urban background monitoring sites for 1993, 2001 and 2009 for each of the 6 European cities (Athens, Barcelona, Brussels, London, Paris, and Vienna). This facilitated the assessment of city specific patterns and comparison of changes with time. Results: SO2 concentrations varied throughout the day and tended to be lower on the weekends. A general decreasing trend for SO2 levels with time was observable at all stations. Discussion & Conclusion: This study provides a useful European perspective on patterns of exposure. For the 6 EU cities examined, road traffic, heating, and shipping in port cities appeared to be important sources of SO2 emissions, and hence the driving components widely reflected in the diurnal profiles with lower levels on the weekend likely due to lower traffic volume and industry related emissions. Although ambient SO2 concentrations have fallen over the assessed study period at all measurement sites, the daily patterns remained relatively unchanged. [Copyright &y& Elsevier]

Abstract: Simultaneous measurements of the PM concentration levels and chemical composition of atmospheric aerosols at a regional background (RB) and an urban background (UB) site, located in the same geographic region, allowed for the determination of their urban and regional contributions. In the specific case of the North-Western region of the Mediterranean the RB amount has been quantified in 18, 13 and 12 μg m−3 for PM10, PM2.5 and PM1, respectively, whereas the UB contribution reached 22, 13 and 8 μg m−3, respectively. The UB contributions in the Western Mediterranean are much higher than those observed in other European regions; especially concerning the coarse fraction. The high loads of road dust in the urban areas across the Mediterranean may account for these large differences. The urban contributions are extremely enriched in Ca, Fe, Sb, Sn, Cu, Zn, being the main tracers of the road dust, with concentrations up to 6–8 times higher than those at the RB. Elemental carbon and nitrate are mainly derived from direct vehicular emissions. Some industrial tracers (Mn, Pb, Bi) are also enriched in the urban area. The evaluation of the Cu/Sb, Cu/Zn, Cu/Cd and Cu/Pb ratios and the high enrichment of these trace elements versus the Upper Crustal Composition average values corroborates the importance of the road-traffic emissions in the study area, also influencing the RB. The supplementary results from a suburban site in the Balearic Islands and the evaluation of the V/Ni ratios evidence the strong signature of fuel-oil combustion processes, which is a general characteristic of the Mediterranean aerosols. [Copyright &y& Elsevier]

Abstract: Despite their burden in urban particulate air pollution, road traffic non-exhaust emissions are often uncontrolled and information about the effectiveness of mitigation measures on paved roads is still scarce. The present study is aimed to evaluate the effectiveness of mechanical sweeping/water flushing treatments in mitigating urban road dust resuspension and to quantify the real benefit in terms of ambient PM10 concentrations. To this aim a specific campaign was carried out in a heavily trafficked central road of Barcelona (Spain), a Mediterranean city suffering from a traffic-related pollution, both for a high car density and a frequent lack of precipitation. Several street washings were performed by means of mechanical sweepers and pressure water during night in all traffic lanes and sidewalks. PM10 levels were simultaneously compared with four reference urban background air quality stations to interpret any meteorological variability. At the downwind measurement site, PM10 concentrations registered a mean daily decrease of 8.8μgm−3 during the 24h after street washing treatments. However 3.7–4.9μgm−3 of such decrease were due to the meteorological variability detected at the upwind site, as well as at two of the reference sites. This reveals that an effective decrease of 4–5μgm−3 (7–10%) can be related to street washing efficiency. Mitigation of road dust resuspension was confirmed by investigating the chemical composition of airborne-PM10 filters. Concentrations of Cu, Sb, Fe and mineral matter decrease significantly with respect to concentrations of elemental carbon, used as tracer for exhaust diesel emissions. High efficiency of street washing in reducing road dust loads was found by performing periodic samplings both on the treated and the untreated areas. [Copyright &y& Elsevier]

Abstract: Extensive measurements on particle number concentration and size distribution (13–800 nm), together with detailed chemical composition of PM2.5 have constituted the main inputs of the database used for a source apportionment analysis. Data were collected at an urban background site in Barcelona, Western Mediterranean. The source identification analysis helped us to distinguish five emission sources (vehicle exhausts, mineral dust, sea spray, industrial source and fuel-oil combustion) and two atmospheric processes (photochemical induced nucleation and regional/urban background particles derived from coagulation and condensation processes). After that, a multilinear regression analysis was applied in order to quantify the contribution of each factor. This study reveals that vehicle exhausts contribute dominantly to the number concentration in all the particle sizes (52–86%), but especially in the range 30–200 nm. This work also points out the importance of the regional and/or urban formed aerosols (secondary inorganic particles) on the total number concentration (around 25% of the total number), with a higher impact on the accumulation mode. The photo-chemically induced nucleation of aerosols only represents a small proportion of the total number as an annual mean (3%), but is very relevant when considering only the nucleation mode (13–20 nm) fraction (23%). The other sources recognized registered sporadic contributions to the total number, coinciding with specific meteorological scenarios. This study discloses the main sources and features affecting and controlling the fine and ultra-fine aerosols in a typical city in the Western Mediterranean coast. Whereas the road traffic appears to be the most important source of sub-micrometric aerosols, other sources may not be negligible under specific meteorological conditions. [Copyright &y& Elsevier]

Ambient PM10 and PM2.5 at Puertollano (central Spain) are derived mostly from local industrial emissions (including a refinery and power stations) and mineral (“crustal”) aerosols from fugitive dusts and African intrusions. Vanadium and the lanthanoid elements (La to Lu) can be used as geochemical markers to help identify these different contributions, especially when combined with atmospheric back-trajectory data. The total lanthanoid (∑Loid) content of PM is controlled primarily by the amount of coarse crustal material present, with the highest values being recorded in PM10 during an African dust intrusion (13ng m−3). In contrast, La/Ce and La/Sm ratios are controlled by fine refinery emissions, rising above natural crustal averages due to the release of La from fluid catalytic converters (FCC), and allowing the identification of La anomalies (La>Ce) when FCC emissions are prominent. Crustal La/Ce ratios are least common, and La anomalies most common, in PM2.5 measured during local pollution events. Increasing contamination of urban/industrial atmospheric PM samples away from crustal compositions may be tracked using a LaCeSm triangular plot, but this does not differentiate between FCC refinery and oil combustion emissions. Comparing lanthanoid and V concentrations does aid such differentiation, although given the likelihood of multiple PM sources in industrial locations, we recommend use of a LaCeV plot rather than simply La/V ratios. [Copyright &y& Elsevier]

The use of fireworks creates an unusual and distinctive anthropogenic atmospheric pollution event. We report on aerosol samples collected during Las Fallas in Valencia, a 6-day celebration famous for its firework displays, and add comparative data on firework-and bonfire-contaminated atmospheric aerosol samples collected from elsewhere in Spain (Barcelona, L’Alcora, and Borriana) and during the Guy Fawkes celebrations in London. Specific high-profile official firework events during Las Fallas included the afternoon Mascletà and the nightly aerial displays (especially in the climactic final 2 days of the fiesta) and were accompanied by pollution spikes in suspended particles, NO, SO2, and the creation and dispersal of an aerosol cloud enriched in a range of metallic elements. Notable metal aerosol concentration increases recorded during Las Fallas were potassium (from 500 to 5900ngm−3), aluminium (as Al2O3 from around 600 to 2200ngm−3), titanium (from 200 to 700ngm−3), magnesium (from 100 to 500ngm−3), lead (from 17 to 379ngm−3), barium (from 39 to 322ngm−3), strontium (from 3 to 112ngm−3), copper (from 12 to 71ngm−3), and antimony (from 1 to 52ngm−3). Firework-contaminated aerosols of similarly metalliferous composition were also identified at the other monitoring sites, although different sites show variations attributable to other sources such as bonfires and local industry. Unusual levels of the trace elements Ba, Sr and (to a lesser extent) Cu, always in proportions with Ba dominant, along with strongly enhanced K, Pb, and Sb, are identified as being particularly characteristic of firework aerosols. Although firework-related recreational pollution episodes are transient in nature, they are highly concentrated, contribute significantly to total annual metal emissions, and are on average fine enough to be easily inhaled and a health risk to susceptible individuals. [Copyright &y& Elsevier]

The origin of the daily exceedances of 50μg PM10m−3 (daily limit value or DLV of the EU air quality directive) and of an arbitrary daily value (DV) 35μg PM2. 5m−3 recorded in 2001–2003 in 13 regional background stations of the Iberian Peninsula were interpreted. This was carried out by means of back-trajectory analysis, available PM model outputs, satellite data and meteorological maps. This allows the detection of high PM episodes on a regional scale and the study of their seasonal and geographical variability. The number of exceedances of the PM10 DLV ranged in 2001–2003 from 6 to 41 depending on the monitoring site. For the selected PM2. 5DV, the range of daily exceedances was 0–10 in the study period. The majority of the PM10 (>70% in most stations) and PM2. 5 (17–55% in most stations) exceedances in regional background monitoring stations are caused by African dust outbreaks. These exceedances were less frequent in winter than in summer due to: (a) the frequent long range transport of dust in the warm seasons over Iberia, (b) the re-suspension associated with convective atmospheric dynamics, and (c) the relative low rainfall favouring re-suspension and high residence time of PM. Moreover, a regional contribution of secondary aerosols derived from the efficient photochemical transformation of gaseous precursors may coincide with African transport in summer. Episodes with lack of advective conditions caused 2–29% and 20–50% of the PM10 and PM2. 5 exceedances. These occurred mainly in summer due to poor renovation of air masses, increased convective re-suspension, dispersion of pollutants towards rural areas and regional re-circulation and aging of air masses which result in the proliferation of secondary inorganic species. Long-range transport of PM from continental Europe caused exceedances (9–40% and 18–38% of the PM10 and PM2. 5 exceedances, respectively), only in northern Iberia because, as the European air masses evolve towards the south, the pollutants suffer dispersion/dilution. Local exceedances are associated with the advection of the clean Atlantic air masses, which cannot increase PM levels to a great extent without the influence of a local source of PM. The proportion of local exceedances of PM10 and PM2. 5 ranged 6–33% and 17–40%, respectively. [Copyright &y& Elsevier]

Abstract: The majority of the Spanish urban population breathe air containing inhalable ambient airborne particles at average concentrations of 30–46μgm−3 (PM10) and 20–30μgm−3 (PM2.5). Even though the average weight of inhaled urban aerosol is commonly similar, however, there can be large chemical differences between the ambient dusts from different towns, including the more bioreactive elements such as some metals. In this context, we compare the source-apportioned trace metal content of airborne PM10 and PM2.5 collected daily over a 1-year period from six population centres in Spain: Barcelona, Alcobendas, Llodio, Huelva, Tarragona and Las Palmas de Gran Canaria. Total average trace metal (ΣTM) PM10 and PM2.5 contents vary by up to a factor of around 3, reaching a maximum of ΣTM10 811ngm−3 and ΣTM2.5 503ngm−3 at Llodio, an industrial but humid site with the lowest PM10 mass levels but high contamination by Zn, Pb, Mn, Sn, Ni and Cr. In contrast, pollution at Huelva, although another industrially influenced site, instead emphasises Cu and As, whereas Barcelona, where traffic emissions and resuspension contribute to some of the highest average PM10 levels in Spain, has unusually raised levels of Ti, V and Ba. Such variations in both daily and annual average PM bulk chemistry, particularly in potentially toxic trace metals concentrated in the finer aerosols (such as Cd, As, Pb, Hg and Ni), predict that PM health effects on resident populations from different towns are unlikely to be the same. [Copyright &y& Elsevier]

Abstract: A 12-month study of PM10 and gases in the industrial Spanish town of Puertollano reveals striking variations in pollutant concentrations. The normal daily pollution pattern is characterised by a daily double peak for NO x and CO and associated double trough for ozone (morning and evening), a midday atmospheric fumigation peak for SO2 and PM10 (1–2h later in winter), and a late morning through afternoon maximum for ozone (shorter and lower in winter). Superimposed upon this are: (1) seasonal variations, which accentuate the PM10 and SO2 mid-morning peaks in winter (when the peak occurs later than in summer), raise NO2, ozone and background particulate levels during the summer, and favour enhanced levels of NO during the winter; (2) local pollution spikes, particularly those associated with SO2 release from nearby industrial sources; (3) regional atmospheric stagnation episodes, which enhance concentrations of all pollutants and (4) intrusion of exotic pollutants, notably desert dust from North Africa. Given that air pollutants are known adversely to influence human health, understanding and predicting such diurnal variations in concentrations of inhalable pollutants is especially relevant to susceptible individuals such as asthmatics. [Copyright &y& Elsevier]

Abstract: The area of Castilla-La Mancha in central Spain is repeatedly visited by mineral dust incursions from the deserts of NW Africa. Such exotic atmospheric intrusions raise background PM10 levels, making urban areas much more likely to exceed daily limits of 50μgm−3 and become subject to fines under European environmental law. Data from a 3-year (2001–2003) study of hourly PM10 values demonstrate that average background dust levels in remote sites rise from 6–8μgm−3 when Atlantic-derived W/SW winds are blowing, to 24–7μgm−3 when African events take place. In four Castilla-La Mancha towns, numbers of exceedence days (ED: when PM10>50μgm−3) per year averaged 31 in Guadalajara (suburban site with annual daily PM10 average ADPM10=27μgm−3), 68 in Toledo (ADPM10=38μgm−3) and 139 in Albacete (ADPM10=47μgm−3; both urban sites), and 151 in Puertollano (industrial urban site with ADPM10=51μgm−3). Thirty-four percent of ED occurred during African dust incursions, and current law allows exclusion of such days from annual data (which also reduces the ADPM10 by 2–4μgm−3). Rather than simply excluding such days, a more scientifically satisfactory approach would be to allow subtraction of the estimated component of exotic background dust present daily at every urban monitoring station, and thus identify towns subject to high levels of locally derived anthropogenic PM10. Such an approach reduces ADPM10 values by the same amount as above (2–4μgm−3) if only African-derived PM10 values (as measured at remote background stations) are subtracted, although ΣED shows a relative increase. If, however, an attempt is made to estimate and subtract the total amount of exotic PM10 (i.e. not just African non-locally derived) at the four sites, this reduces the ADPM10 by 8–12μgm−3, and ΣED also drops significantly. Whichever approach is adopted, however, our data confirm that the legally allowable number of ED is far more strict than the annual limit value. This inconsistency will make it especially difficult for many southern European towns, with their abundant dry dust resuspension and regular incursions of African dust, to achieve PM exceedence targets in 2005. We argue that further refinement of aerosol pollution law is necessary to ensure that penalties for exceeding legally acceptable levels of atmospheric particulates are scientifically well founded and fair. [Copyright &y& Elsevier]

Abstract: A strong African dust outbreak episode affecting the Canary Islands from 28 to 31/07/02 has been characterised at the Izaña Observatory (IZO), located in the free troposphere (FT), and at Sta. Cruz de Tenerife (SCO), in the Marine Boundary Layer (MBL). The Saharan air mass intruded above the trade wind inversion layer resulting in daily mean PM levels of up to 616, 312, 98 and 26μgm−3 of TSP, PM10, PM2.5 and PM1, respectively, at IZO. As demonstrated by the vertical sounding profiles, the MBL is compressed during the Saharan intrusion, favouring the deposition of coarse dust particles to the MBL and giving rise to daily levels of up to 85, 52 and 30μgm−3 of PM10, PM2.5 and PM1, respectively, at SCO. A complete chemical and mineralogical characterisation has been performed for TSP and PM2.5 collected simultaneously at both sites. Levels of mineral elements increased during the Saharan episode at both sampling sites. In addition, at the MBL, the levels of the secondary inorganic aerosols registered during the Saharan episode were considerably higher than levels recorded during non-Saharan episodes. The partial formation of secondary coarse Ca and/or Na sulphates and nitrates by the reaction of gaseous pollutants (or derived oxidised phases), of a major local origin, with the natural aerosols has been deduced. These reactions may be favoured by the high concentration of coarse mineral and marine aerosols particles measured at SCO, the high relative humidity (RH) measured, as well as the strong compression of the MBL during the Saharan episode. [Copyright &y& Elsevier]

Abstract: The present work shows a straightforward procedure to indirectly estimate the chemical composition at a given site only from the determination of the PM concentrations, and the classification of the days according to the main meteorological scenarios. A previous study based on the mean chemical composition associated to the main meteorological scenarios is required. This experiment has been carried out with data from two monitoring sites in the North-Western Mediterranean, one regional and one suburban background. At both sites, one-year datasets on chemical PM10 composition were obtained. Based on these datasets, the mean PM10 compositions according to the most relevant meteorological situations were calculated for both locations. After that, the reconstruction of the chemical composition for all the days with available PM10 concentrations was completed. Subsequently, the estimated PM10 composition was compared with that determined experimentally. The comparison between the rebuilt and the experimental results was very satisfactory in the case of the regional background site, and relatively replaced in the other case. Furthermore, the validation of the method at the regional background site has been conducted from the reconstruction of a 4-year data base, and subsequent comparison with the experimental chemical composition. Our results show that it is possible to attain a good approach to the chemical composition at regional background sites, where local emission sources are negligible. Conversely, when the local sources rise in importance, i.e., at a suburban background site, the approach is suitable only for those components with a more regional origin and/or those from long range transport of air masses. [ABSTRACT FROM AUTHOR]

Abstract: Different monitoring parameters (PM mass concentrations, number–size distribution, black carbon, gaseous pollutants, and chemical composition, among others) are currently used in air quality studies. Urban aerosols are the result of several sources and atmospheric processes, which suggests that a single monitoring technique is insufficient to quantitatively evaluate all of them. This study assesses the suitability of a number of monitoring techniques (PM mass concentrations, number and size distribution of ultra-fine particles, levels of gaseous pollutants, and a complete chemical characterization of PM10 and PM2.5) by examining the response of those techniques to the different emission sources and/or atmospheric processes affecting an urban Mediterranean area (Barcelona, NE Spain). The results of this work reveal that the PM mass, the number concentration and the chemical composition give different, but complementary, information. Whereas the mineral matter, a key atmospheric aerosol component across the Mediterranean, is not properly quantitatively assessed by measuring sub-micrometric particles, the monitoring of the number concentration is indispensable to interpret the origin of specific aerosol episodes. Furthermore, the chemical composition yields very relevant information to deduce the causes of specific pollution episodes. The number concentration of ultra-fine particles in urban areas is strongly dependent upon vehicle exhaust emissions, which may cause adverse health impacts. Moreover, urban Mediterranean environments are favourable to produce nucleation-mode particles (<20 nm) with photochemical origin. In those cases, these particles are expected to be of high solubility and consequently their toxicity may differ from that of traffic-generated ultra-fine particles. Thus, the use of a single monitoring parameter to evaluate the health effects seems to be not enough. [ABSTRACT FROM AUTHOR]

Abstract: The geochemistry of PM10 filter samples collected at sea during the Scholar Ship Atlantic–Mediterranean 2008 research cruise reveals a constantly changing compositional mix of pollutants into the marine atmosphere. Source apportionment modelling using Positive Matrix Factorization identifies North African desert dust, sea spray, secondary inorganic aerosols, metalliferous carbon, and V–Ni-bearing combustion particles as the main PM10 factors/sources. The least contaminated samples show an upper continental crust composition (UCC)-normalised geochemistry influenced by seawater chemistry, with marked depletions in Rb, Th and the lighter lanthanoid elements, whereas the arrival of desert dust intrusions imposes a more upper crustal signature enriched in “geological” elements such as Si, Al, Ti, Rb, Li and Sc. Superimposed on these natural background aerosol loadings are anthropogenic metal aerosols (e.g. Cu, Zn, Pb, V, and Mn) which allow identification of pollution sources such as fossil fuel combustion, biomass burning, metalliferous industries, and urban–industrial ports. A particularly sensitive tracer is La/Ce, which rises in response to contamination from coastal FCC oil refineries. The Scholar Ship database allows us to recognise seaborne pollution sourced from NW Africa, the Cape Verde and Canary islands, and European cities and industrial complexes, plumes which in extreme cases can produce a downwind deterioration in marine air quality comparable to that seen in many cities, and can persist hundreds of kilometres from land. [Copyright &y& Elsevier]

Abstract: We report on ambient atmospheric aerosols present at sea during the Atlantic–Mediterranean voyage of Oceanic II (The Scholar Ship) in spring 2008. A record was obtained of hourly PM10, PM2.5, and PM1 particle size fraction concentrations and 24-h filter samples for chemical analysis which allowed for comparison between levels of crustal particles, sea spray, total carbon, and secondary inorganic aerosols. On-board monitoring was continuous from the equatorial Atlantic to the Straits of Gibraltar, across the Mediterranean to Istanbul, and back via Lisbon to the English Channel. Initially clean air in the open Atlantic registered PM10 levels <10 μg m−3 but became progressively polluted by increasingly coarse PM as the ship approached land. Away from major port cities, the main sources of atmospheric contamination identified were dust intrusions from North Africa (NAF), smoke plumes from biomass burning in sub-Saharan Africa and Russia, industrial sulphate clouds and other regional pollution sources transported from Europe, sea spray during rough seas, and plumes emanating from islands. Under dry NAF intrusions PM10 daily mean levels averaged 40–60 μg m−3 (30–40 μg m−3 PM2.5; c. 20 μg m−3 PM1), peaking briefly to >120 μg m−3 (hourly mean) when the ship passed through curtains of higher dust concentrations amassed at the frontal edge of the dust cloud. PM1/PM10 ratios ranged from very low during desert dust intrusions (0.3–0.4) to very high during anthropogenic pollution plume events (0.8–1). [Copyright &y& Elsevier]

Abstract: Average 21st century concentrations of urban air pollutants linked to cardiorespiratory disease are not declining, and commonly exceed legal limits. Even below such limits, health effects are being observed and may be related to transient daytime peaks in pollutant concentrations. With this in mind, we analyse >52,000 hourly urban background readings of PM10 and pollutant gases throughout 2007 at a European town with legal annual average concentrations of common pollutants, but with a documented air pollution-related cardiorespiratory health problem, and demonstrate the hourly variations in PM10, SO2, NOx, CO and O3. Back-trajectory analysis was applied to track the arrival of exotic PM10 intrusions, the main controls on air pollutants were identified, and the typical hourly pattern on ambient concentrations during 2007 was profiled. Emphasis was placed on “worst case” data (>90th percentile), when health effects are likely to be greatest. The data show marked daytime variations in pollutants result from rush-hour traffic-related pollution spikes, midday industrial SO2 maxima, and afternoon O3 peaks. African dust intrusions enhance PM10 levels at whatever hour, whereas European PM incursions produce pronounced evening peaks due to their transport direction (across an industrial traffic corridor). Transient peak profiling moves us closer to the reality of personal outdoor exposure to inhalable pollutants in a given urban area. We argue that such an approach to monitoring data potentially offers more to air pollution health effect studies than using only 24 h or annual averages. [Copyright &y& Elsevier]

Real time measurements of number concentrations (13–800 nm, N13–800) of size discriminated sub-micrometric aerosols and PM (0.3–10 μm) mass concentrations were carried out over a one-year-period at an urban site in Barcelona, North-eastern Spain. Annual mean levels of N13–800 were close to 17,000 cm−3, and strongly dependent on road traffic emissions. Annual mean PM10, PM2.5 and PM1 levels were 39, 25 and 18 μg/m3, being highly influenced not only by road traffic but also by industrial emissions as well as natural events such as African dust outbreaks. Variability of number concentrations and size distribution of sub-micrometric aerosols was strongly dependent on meteorology. Primary emissions exert a high influence on the variability of levels of ultrafine (<100 nm) particles under intense Atlantic advections (lowest PM levels), while coagulation and condensation processes are enhanced under urban pollution scenarios (highest levels of PM), and photochemical nucleation processes can be an important source of ultrafine particles at midday in summer (low PM levels). African dust episodes did not modify the total number but affected the N > 400 nm. This study allows us to compare aerosol number and mass concentrations in air quality monitoring of an urban environment. Ultrafine particles measurements are indicated to detect the variability of primary traffic emissions, as well as some atmospheric processes. Measurements of PM levels are necessary to monitor other important PM sources in the studied area such as dust resuspension from road traffic or African dust. [Copyright &y& Elsevier]

Abstract: This study applies a methodology for discriminating local and external contributions of atmospheric particulate matter (PM) at a rural background station in the North-western coast of Spain. The main inputs at the nearest scale have come from soil dust, marine aerosol and road traffic. At a larger scale, the highest contributions have come from fossil-fuel combustion sources, giving rise to relatively high ammonium sulphate background levels, mainly in summer. External contributions from long-range transport processes of African dust and nitrate have been detected. Morocco and Western Sahara have been identified as the main potential source regions of African dust, with a higher content of Al and Ti than other crustal components. Geographical areas from central and Eastern Europe have been identified as potential sources of particulate nitrate. The discrimination of the PM contribution from natural and anthropogenic sources at different geographical scales is a necessary information for establishing PM reduction strategies in specific areas. [Copyright &y& Elsevier]

Abstract: Particulate matter (PM) pollution in cities has severe impact on morbidity and mortality of their population. In these cities, road dust resuspension contributes largely to PM and airborne heavy metals concentrations. However, the short-term variation of emission through resuspension is not well described in the air quality models, hampering a reliable description of air pollution and related health effects. In this study we experimentally show that the emission strength of resuspension varies widely among road dust components/sources. Our results offer the first experimental evidence of different emission rates for mineral dust, heavy metals and carbon fractions due to traffic-induced resuspension. Also, the same component (or source) recovers differently in a road in Barcelona (Spain) and a road in Utrecht (The Netherlands). This finding has important implications on atmospheric pollution modelling, mostly for mineral dust, heavy metals and carbon species. After rain events, recoveries were generally faster in Barcelona rather than in Utrecht. The largest difference was found for the mineral dust (Al, Si, Ca). Tyre wear particles (organic carbon and zinc) recovered faster than other road dust particles in both cities. The source apportionment of road dust mass provides useful information for air quality management. [Copyright &y& Elsevier]