Speciation and origin of PM10 and PM2.5 in Spain

Aerosol Science 35 (2004) 1151 – 1172 www.elsevier.com/locate/jaerosci

Speciation and origin of PM10 and PM2.5 in Spain X. Querola;∗ , A. Alastueya , M.M. Vianaa , S. Rodrigueza , B. Arti˜nanob , P. Salvadorb , S. Garcia do Santosc , R. Fernandez Patierc , C.R. Ruizd , J. de la Rosae , A. Sanchez de la Campae , M. Menendezf , J.I. Gilf a

Instituto de Ciencias de la Tierra del CSIC, C/Lluis Sole i Sabars s/n, 08028 Barcelona, Spain b CIEMAT, Avda. Complutense 22, 28040 Madrid, Spain c Instituto de Salud Carlos III, Ctra. Majadahonda-Pozuelo, km2, 28220 Majadahonda, Spain d Instituto de Carboqumica CSIC, C/Mara de Luna, 12, 50015 Zaragoza, Spain e Dpto. de Geologa, Univ. Huelva, Campus Universitario de la Rabida, La Rabida, 21819, Huelva, Spain f Dpto. Mineraloga y Petrologa, Universidad del Pas Vasco, Aptdo. 644, 48080 Bilbao, Spain Received 19 January 2004; received in revised form 19 April 2004; accepted 20 April 2004

Abstract This work summarizes the results of a series of comprehensive studies on particulate matter (PM) carried out in Spain from 1999 to 2001. Monitoring sites were selected in accordance with di8erent climatic and geographic conditions as well as anthropogenic in9uences, varying from rural background to urban curb-side sites. Measurements were carried out with gravimetric high-volume samplers and with automatic devices for di8erent PM grain sizes, focusing on PM10 and PM2.5. A simultaneous meteorology study was performed to assess the in9uence of air masses and to detect long-range transport processes, especially African dust outbreaks, a8ecting the PM levels in the Iberian Peninsula and the Canary Islands. Mean values, chemical compositions and source apportionment analyses were obtained and discussed as a function of the di8erent monitoring sites and during PM episodes. ? 2004 Elsevier Ltd. All rights reserved. Keywords: PM10; PM2.5; Chemical speciation; Source apportionment; Ambient air

1. Introduction Given the close relationship between particulate matter (PM) air pollution and the adverse effects on health reported in several epidemiological studies, the standards for this air pollutant were ∗

Corresponding author. CSIC, Environmental Geochemistry, C/Lluis Sole i Sabaris sn, 08028 Barcelona, Spain. Tel.: +34-934095410; fax: +34-934110012. E-mail address: [email protected] (X. Querol). 0021-8502/$ - see front matter ? 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaerosci.2004.04.002

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reviewed at the end of the 1990s in Europe (Directive 1999/30/EC). The resulting new standards established daily and annual limit values for PM10 (deFned as the mass of particulate matter which passes through a size selective impactor inlet with a 50% eHciency cut-o8 at 10 m aerodynamic diameter) levels, which will become progressively more restrictive from 2001 to 2010. The suitability of these criteria is under revision, and both the PM10 limit values and the PM pollution indicator may be subject to modiFcation. The monitoring of the airborne particulate matter pollution is fraught with diHculty given that PM is a complex mixture of substances in solid or liquid states with di8erent properties (e.g. size distribution, gas–solid/liquid partitioning, toxicity, etc.) and origins (including natural sources). The precise properties that need to be monitored for health protection are still open to discussion (WHO, 2003). To date, air quality standards have been deFned in terms of the bulk PM mass concentration below a given cut size (e.g. PM10 & PM2.5 in United States), and the chemical mass balance has been the most commonly used method for assessing PM source contributions (Wilson et al., 2002). In addition to the local emissions, there are several factors in9uencing PM levels and composition that undergo regional variations in Europe. Mineral dust may exert a considerable in9uence on PM levels in areas a8ected by natural dust resuspension, desert dust transport (RodrNOguez, Querol, Alastuey, Kallos, & Kakaliagou, 2001), or low-rainfall rates favoring dust accumulation (e.g. streets in urban areas). Moreover, long-range transport of pollutants could also have an in9uence on PM levels of a given area in the Northern EU (TarrasNon et al., 2003). Sea-spray may signiFcantly contribute to PM levels at coastal sites. Furthermore, temperature and humidity exert an in9uence on the gas-particle partitioning of low vapor pressure species (e.g. ammonium nitrate and semivolatile organic species), and consequently on the load of these species in the PM phase (MNeszNaros, 1999 and references therein). The decision taken by the European Commission to revise the standards for PM has led to a renewed interest in the characterization of PM in the di8erent regions of Europe (Putaud et al., 2004) and also to a better understanding of PM pollution problems. This paper presents a summary of the results obtained from a PM study carried out in di8erent geographical and climatic areas of Spain, focusing on the PM10 and PM2.5 compositional changes as a function of ambient conditions and of the type of monitoring site (from rural background to urban curb-side sites). A segregated chemical mass balance of PM10 & PM2.5 is performed. 2. Methodology 2.1. The study areas Six geographical zones in Spain were deFned and selected covering di8erent climatic conditions and anthropogenic activities. Five areas were located in the Iberian Peninsula: (1) Galicia in the Northwest is a humid and well-ventilated area frequently a8ected by westerly winds and frontal systems; (2) the Basque Country (Euskadi) adjacent to the Cantabrian coast in the North; (3) the Eastern area bordering the Mediterranean sea is dominated by the coastal circulations interacting with topography frequently resulting in atmospheric layering and recirculation of polluted air masses (Gangoiti, MillNan, Salvador, & Mantilla, 2001; MillNan, Salvador, Mantilla, & Kallos, 1997; MillNan et al., 2000); (4) the Central area in the plateau acts as the core of thermal low-pressure systems in

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Fig. 1. Geographical location of the measurement stations.

summer; and (5) AndalucNOa is the Southernmost region of the Peninsula in the Atlantic-Mediterranean interphase. Finally, the Canary Islands where the NE trade winds on the Atlantic Ocean and the proximity to the Sahara desert exert a decisive in9uence on the climate and particulate matter levels of this region. After deFning the six study areas, seven monitoring stations (Fig. 1 and Table 1) were selected for the experimental study. These were classiFed as rural background, urban background and curb-side sites according to the degree of anthropogenic in9uence. Some urban background sites also included remote industrial emissions. Curb-side sites were under the direct in9uence of intense traHc. 2.2. PM measurements and sampling Continuous measurements of PM10, PM2.5 and PM1 were performed using a GRIMM 1107 laser spectrometer and corrected when necessary with simultaneous 24 h gravimetric measurements. The measurement period was from January 2001 to March 2002 and the data coverage obtained was higher than 95% at most stations.

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Table 1 Location and characteristics of the 7 measurement stations selected for the study Longitude

Alcobendas Barcelona Bemantes Canary Islands Huelva Llodio Tarragona

03◦ 02◦ 08◦ 15◦ 05◦ 02◦ 01◦

37 11 10 24 56 57 14

39 47 50 49 24 44 52

Latitude

W E W W W W E

40◦ 41◦ 43◦ 28◦ 37◦ 43◦ 41◦

32 25 20 08 15 08 07

42 30 15 04 21 42 29

N N N N N N N

Altitude (m a.s.l.)

Station type

667 24 170 20 10 122 20

Urban background Curb-side Rural background Urban background Urban background Urban background Urban background

Sampling days PM10

PM2.5

111 119 123 98 129 108 119

58 85 85 80 87 74 85

At each station, 24 h sampling was carried out by means of a PM10 Graseby–Andersen high volume sampler (68 m3 =h), which is an EN12341 reference instrument, and a MCV high volume sampler (30 m3 =h) equipped with a PM2.5 inlet and quartz Fber Flters (QF20 Schleicher and Schuell). A total number of 1620 PM10 and 800 PM2.5 Flters were collected at the seven sampling stations at a rate of three PM10 and two PM2.5 Flters per week, from which two PM10 and one PM2.5 samples were selected for chemical analysis. Samples were treated and analyzed for determining the levels of major and trace components following the procedure of Querol et al. (2001a, b) and RodrNOguez, Querol, Alastuey, and Plana (2002). This is based on the daily sampling of PM and subsequent analysis of major and trace elements by ICP-AES and ICP-MS (of acidic digestions of a 12 fraction of each Flter), soluble anions and cations by Ion Chromatography, ammonium by Calorimetry-FIA and carbon by thermo-optical methods. Sampling started at 8:00 am LST and sample collection was performed immediately after Fnishing the sampling sequence to avoid the loss of semi-volatile compounds. We are aware of the possible sampling artifacts regarding the potential loss of certain reactive species as well as the positive artifact arising from the potential Fxation of volatile species that may take place using the EU reference PM10 sampling procedure. However, we carried out the study following this procedure to quantitatively determine the di8erent source contributions to PM levels with the measurement procedure used in the air quality monitoring networks in the EU. Blank Feld Flters were used for every stock purchased for sampling (at least Fve blank Flters for each 50 Flter stock). Fractions of the blank Flters were analyzed in the same batches of their respective Flter samples. The corresponding blank concentrations were subtracted for each sample. For analysis control, a few mg of the reference material NIST 1633b was added to a fraction of a blank Flter to check the accuracy of the analysis of the acidic digestions. For most elements, relative analytical errors were ¡ 10%, with exception of P and K for which a 15% error was determined. This methodology was successfully tested for the analysis of city dust in an IEA round robin exercise. 2.3. Data treatment The origin of air masses in9uencing the monitoring stations for each day of the sampling period was interpreted on the basis of daily computed 5-day isentropic back trajectories using the

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HYSPLIT model (Draxler & Hess, 1998a, b) and ECMWF synoptic charts (surface and upper levels). Furthermore, African dust outbreaks a8ecting the Iberian Peninsula were also detected with the aid of daily TOMS-NASA aerosol index maps, SKIRON (Athens University) and NAAPS (Naval Research Laboratory-Marine Meteorology Division) models dust concentration maps and SeaWIFS-NASA satellite imagery. Four groups of components were considered: OC+EC (organic plus elemental carbon), mineral dust (Al and Si oxides, CO23− , Ca, Mg, P, Fe, K and some other trace elements), marine (SO24−marine , Cl− and Na) and secondary inorganic phases (SO24−non-marine , NH+ 4 and NO3 ). As a Frst approach to the interpretation of the PM sources, we considered a heavy traHc site located at a major street-canyon. The PM load at such a site may be divided into three di8erent contributions: contribution from the local traHc from the road on which the site is located, the urban background contribution and that from the regional background. The addition of these three contributions results in the PM levels recorded at the traHc site (Lenschow et al., 2001). Thus, the PM levels and components (OC+EC, mineral, marine and secondary) measured at a roadside station may be broken down into the following contributions: (1) regional background; (2) city background (background levels of emissions such as traHc, construction, demolition and domestic heating); and (3) road traHc contribution (motor emissions and tire, pavement and brakes abrasion products) exclusively from the street-canyon where the station is located. A varimax rotated Factor Analysis was also performed to identify the main sources a8ecting the PM composition at each sampling site. The factors with eigenvalues greater than one were extracted and identiFed as particle sources, based on the interpretation of their loadings. After the identiFcation of the main sources, the respective quantitative contributions were derived using the methodology described by Thurston and Spengler (1985). Multilinear Regression Analysis was applied, using PM concentration values as the dependent variable and absolute factor scores as independent variables. Estimations of the daily source contributions were obtained as the product of the daily absolute factor scores and the multi-linear regression coeHcients.

3. Results and discussion 3.1. PM levels and components In addition to the 2001 data presented in this study for Tarragona, Barcelona, Bemantes (A Coru˜na), Llodio (Alava), Huelva, Las Palmas de Gran Canaria and Alcobendas (Madrid), Fndings from prior studies (mid-1999 to mid-2000), obtained by using the same sampling and analytical methodology, were also included in the discussion for a better spatial and sitting coverage. These additional data were collected at roadside sites from Madrid-Escuelas Aguirre (ArtNOn˜ ano, Salvador, Alonso, Querol, & Alastuey, 2003) and L’Hospitalet-Barcelona (Querol et al., 2001b) and at a rural background site (Monagrega, RodrNOguez et al., 2002). 3.1.1. PM levels Table 2 shows the annual mean of PM10 and PM2.5 levels and their components according to the type of station. Based on these data, on the aforementioned studies and on those from the 2001

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Table 2 PM10 and PM2.5 composition in di8erent sites from Spain Monagrega Bemantes Tarragona Huelva Alcobendas Llodio Canary Madrid Rural background Urban background stations Year

1999–2000 2001

L’Hospitalet Barcelona Curb-side sites

2001

2001

2001

2001

2001

1999–2000 1999–2000 2001

PM10 (g=m3 ) 20.7 N 132 OC+EC 2.1 Mineral 5.2 Marine 0.7 Unaccounted 5.2 Secondary 7.5 inorganic nmSO2− 3.7 4 NO− 2.5 3 NH+ 1.3 4

18.9 87 4.2 2.5 2.6 4.4 5.2

37.4 88 7.3 9.2 2.3 8.4 10.2

37.5 91 5.3 11.8 2.8 9.7 7.9

32.2 84 8.7 8.6 1.2 7.3 6.4

31.7 85 6.8 7.3 2.3 6.7 8.7

44.4 88 6.6 11.6 11.5 9.8 4.9

47.7 69 15.1 15.2 0.8 8.9 7.7

49.8 115 11.1 12.9 2.3 8.2 15.3

46.2 90 9.4 15.2 2.4 8.4 10.8

3 0.9 1.3

4.9 3.9 1.5

4.7 1.8 1.5

2.9 2 1.5

5.4 1.5 1.6

2.7 1.6 0.8

4.4 2.1 1.2

6.8 5.8 2.7

4.9 3.9 2

PM2,5 (g=m3 ) N OC+EC Mineral Marine Unaccounted Secondary inorganic nmSO2− 4 NO− 3 NH+ 4

ND ND ND ND ND

13.5 45 3.8 1.5 1 2.8 4.4

21.8 43 6.5 1.9 1 5.2 7.2

19.3 49 5.0 2.7 0.8 5.3 5.5

24.9 34 9.3 2.7 0.6 7.0 5.3

23.9 44 6.9 2.3 1.2 6.1 7.4

18.4 47 6.6 3 1.6 4.2 3

34.1 38 14.4 5.6 0.5 7.1 6.5

34.5 63 11.2 4.2 0.9 5.2 13

27.6 45 10.2 4.2 0.7 4.2 8.3

ND ND ND

2.9 0.4 1.2

3.9 1.9 1.4

3.6 0.5 1.4

2.7 1.3 1.4

4.9 0.8 1.7

1.9 0.4 0.7

3.8 1.3 1.4

5.8 4 3.2

4.2 2.3 2.0

ND

N , number of samples; OC+EC, organic + elemental carbon; nmSO2− 4 , non-marine sulfate, ND: no data.

regional background stations of the Spanish EMEP network, the ranges of PM10 and PM2.5 levels in Spain for the three station categories may be summarized as follows: • Regional background levels of PM are close to 15 g PM10=m3 in the Atlantic regions and 20 gPM10=m3 in the other regions, and 9–14 g PM2:5=m3 for the whole territory. • Urban background levels of PM10 and PM2.5 range from 30 to 40 and from 17 to 25 g=m3 , respectively. • At roadside stations, PM10 and PM2.5 levels range between 45 and 50, and 25 and 35 g=m3 , respectively. The results of this study clearly show that for 2001, the annual PM10 mean of 40 g=m3 and the number (n) of 35 annual exceedances of the daily limit value of 50 g=m3 Fxed for 2005 by the directive 1999/30/EC are not equivalent, and that the equivalent ‘n’ to this annual mean is 80–85 (Fig. 2). In other words, the percentile 90 equivalent to this annual PM10 mean is 60 g=m3

PM10 annual mean (µg/m3)

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60 y = 0.33x + 13.5 R2 = 0.90

50 40 30 20 10 0 10

30

50

70

90

110

PM10 annual mean (µg/m3)

'n'> 50 µgPM10/m3 60 y = 0.97x - 18.07 R2 = 0.81

50 40 30 20 10 0 30

40

50

PM10 annual mean (µg/m3)

PM10 90 percentile

60

70

(µg/m3)

60 50 40 30 y = 1.26x + 6.12 R2 = 0.79

20 10 0 10

15

20

25

30

35

40

PM2.5 annual mean (µg/m3)

Fig. 2. Cross-correlation plot between the annual mean of PM10, the number of annual daily exceedances of the 50 g=m3 limit value and the annual PM2.5 mean for the monitoring stations in 2001. The mean annual PM10 limit value for 2005 (40 g=m3 ) is highlighted to indicate the equivalent: top: number of exceedances of the daily limit value, middle: 90 percentile and bottom: PM2.5 annual limit value.

instead of 50 g=m3 . The annual PM10 mean equivalent to ‘n’=35 is around 25 g PM10=m3 . Consequently, it can be concluded that the daily and annual PM10 limit values for 1999/30/EC Directive are not equivalent, and that the daily limit value is much more restrictive than the annual one. Furthermore, Fig. 2 also demonstrates that the 40 g PM10/m3 annual limit value is equivalent to 27 g PM2:5=m3 .

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3.1.2. Major PM components The Flters collected during the study period were analyzed, and on average 75–85% of the PM mass was determined (Table 2). A fraction of around 4 and 9 g=m3 in PM10 and 2 and 6 g=m3 in PM2.5 was unaccounted mass in regional and urban sites, respectively. A fraction of this unaccounted mass is attributed to water since the Flter samples cannot be heated to avoid loss of volatile material, but also to unaccounted hetero-atoms, which are mainly derived from the organic constituents. The mineral fraction ( of CO23− , SiO2 , Al2 O3 , Ca, Mg, Fe, P and K) may reach 35% of the PM10 mass from the road side sites (Madrid, Sagrera-Barcelona), 22–32% at the urban and regional background sites in the Iberian Peninsula and the Canaries (Monagrega, Huelva, Alcobendas, Tarragona and Las Palmas), and 13–21% at urban and regional background sites in the Northern regions of the Iberian Peninsula (Bemantes and Llodio). The mineral contribution to PM2.5 is signiFcantly reduced, but still reaches 21% in the Canaries, 8–19% at urban background stations and 17% at roadside sites. It is evident that levels of mineral components in PM10 (Fig. 3) are very dependent on the traHc in9uence (mainly dust resuspension, erosion of road pavements and brakes). Thus, the highest levels were measured at the street-canyon stations (13–15 g=m3 ), followed by urban background sites (11–12 g=m3 in Southern Iberian Peninsula and the Canaries and 7–9 g=m3 in the rest of Spain) and by the regional background sites (2 and 5 g=m3 in Northern and Southern Iberian Peninsula, respectively). However, the crustal background contributions are higher in the Canaries and in the Southern and Eastern parts of the Iberian Peninsula than in the North. The spatial distribution of levels of mineral dust in PM2.5 shows a closer relationship with traHc activity than in PM10 with the result that the mineral dust levels are reduced to 2–3 g=m3 at background sites and 4–6 g=m3 at traHc sites. The marine components (Fig. 3) attain very high levels in PM10 in the Canary Islands (11:5 g=m3 or the equivalent 25%, as an annual mean). In the Iberian Peninsula, levels of marine contribution range from 2.3 to 2:8 g=m3 for PM10 at coastal sites (4–9% of PM10 load in Barcelona, L’Hospitalet, Tarragona y Huelva) and at the stations located in the Atlantic regions (Bemantes and Llodio, 16% of the PM10 bulk levels), whereas the levels measured at inland stations (Madrid and Monagrega) reach only 0.7–1:2 g=m3 . In PM2.5 the di8erence between the Canaries and the Iberian Peninsula in levels of marine components is reduced, with mean levels of 1.6 and 0.5–1:2 g=m3 , respectively (or the equivalent 6% and 2%). In the Iberian Peninsula, Na+ and Cl− exhibited slightly higher levels in summer (Fig. 3) as a consequence of the higher intensity of sea breeze dynamics, but also a lower Cl− =Na+ ratio. The latter may be attributed to the reaction of nitric acid (released by the thermal instability of ammonium nitrate in summer) with sodium chloride resulting in NaNO3 (particle) and HCl (gas) formation. In the Canaries, Na+ and Cl− did not exhibit a seasonal cycle. The spatial distribution of non-marine sulfate (¿ 90% as (NH4 )2 SO4 ) levels in PM10 (Fig. 3) was found to depend mostly on the degree of industrialization of the regions. Thus, non-marine sulfate levels ranged from 4 to 6 g=m3 in highly industrialized areas (e.g. Barcelona, Tarragona, L’Hospitalet, Llodio and Huelva), whereas they ranged from 2 to 4 g=m3 at urban and regional background sites without industrial in9uence. In the Iberian Peninsula, non-marine sulfate exhibited a seasonal evolution with a summer maximum because of the higher SO2 oxidation velocity under high insolation conditions (Hidy, 1994 and Querol et al., 1999). This seasonal pattern is not observed in the Canaries owing to the main role of long-range transport from Europe (McGovern, Nunes, Raes, & Gonzales-Jorge, 2002). Moreover, ambient conditions (e.g. temperature and radiation) show little seasonal variation in the Islands with respect to the Peninsula.

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2− Fig. 3. Mean levels and seasonal patterns for mineral matter and marine aerosols in PM10 and PM2.5 and NO− 3 , SO4 , + organic + elemental carbon (OC+EC) and NH4 in PM10 in 10 stations from Spain (data from 1999 to 2001).

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A clear spatial gradient was observed for the levels of nitrate in PM10 (Fig. 3), with no signiFcant relationship with the distribution of emission sources. Thus, the mean annual levels of nitrate measured range from 0.9 to 1:8 g=m3 for the Atlantic (Las Palmas, Bemantes, Huelva, and Llodio), from 2.0 to 2:5 g=m3 for Central (Monagrega, Madrid, Alcobendas) and from 3.9 to 5:8 g=m3 for the Mediterranean (Barcelona, L’Hospitalet and Tarragona) regions. This spatial distribution shows a low relationship with road traHc or industrial density given that sites with similar industrial development (Huelva and Tarragona) have very di8erent nitrate levels. The above spatial gradient may be related to one or both for the following reasons: (a) The relatively low dispersive atmospheric conditions prevailing in the Mediterranean basin (MillNan et al., 1997) compared with those in the Atlantic regions (the latter characterized by frequent Atlantic advection). (b) Higher ammonia (NH3 ) emissions in the Eastern regions. The presence of this gas has been cited as the major cause for high ammonium nitrate levels in central Europe. Ambient air NH3 levels were not measured, but it should be pointed out that the highest mean annual concentrations 3 of NH+ 4 were measured at the Barcelona and L’Hospitalet sites (2.0–2:7 g=m with respect to 3 0.8–1:6 g=m at the other sites). Nitrate exhibited a marked seasonal evolution characterized by a summer minimum at all sites with the exception of the Canaries and Llodio (Fig. 3). This seasonal trend is attributed to the low thermal stability of ammonium nitrate in the warm season (Stelson, Friedlender, & Seinfeld, 1979; MNeszNaros and HorvNath, 1984; Willison, Clarke, & Zeki, 1985; Seidl et al., 1996). Higher nitrate levels in winter are favored by the higher stability of ammonium nitrate (in cool conditions) and the reduced dispersive conditions in the boundary layer. In the Canaries the lower seasonal temperature contrast reduces the changes in nitrate levels to a minimum. At Llodio, the seasonal trend of nitrate is less abrupt probably as a consequence of the signiFcant summer breeze transport of atmospheric pollutants from the coastal industrial zones along the NerviNon valley. Levels of organic and elemental carbon (OC+EC, Fig. 3) are higher (10–15 g=m3 ) at streetcanyon stations (Madrid, Barcelona and L’Hospitalet), intermediate at urban background stations (5–9 g=m3 ; Llodio, Tarragona, Huelva, Las Palmas and Alcobendas), and lower at the regional background sites (2–4 g=m3 ). The seasonal trend of levels of OC+EC presents a winter maximum as a consequence of the lower atmospheric dispersion in the Iberian Peninsula and in the Canaries. The above described spatial variation for OC+EC and secondary inorganic species in PM10 also applies to PM2.5. However, it should be pointed out that lower NO− 3 levels were recorded in PM2.5 than in PM10, mainly in summer. This is mainly because of the occurrence of NaNO3 and/or Ca(NO3 )2 in the 2.5–10 m fraction. The proportion of sodium and calcium nitrate over bulk nitrate levels is higher in summer due to the lower thermal stability of ammonium nitrate, and the consequent prevalence of nitric acid. Most of the nitrate in PM10 occurs as sodium nitrate owing to the high Na+ concentrations in the Canaries. As a result of the PM compositional di8erences, the loads of PM1, PM1.0–2.5 and PM2.5–10 in PM10 undergo signiFcant variations throughout Spain. The PM2.5–10 load in the PM10 mass ranges from ¿ 55% in the Canaries, 41–47% in Southern to Eastern regions, to 26–36% in Central and Northern Spain (Fig. 4). These values are very close to the marine plus crustal contributions to PM10. Conversely, the PM1 load in PM10 varies as follows: 52–62% in the Central and Northern regions, ∼ 40% in the Southern and Eastern regions, and only 21% in the Canaries. Thus, in the

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Fig. 4. Annual (2001) mass contributions of PM1, PM1–2.5 and PM2.5–10 in PM10, (January to December 2001) recorded in seven measurement sites of Spain.

Northern regions, the PM1/PM10 ratios are 50% higher than those in Southern and Eastern regions, and up to three times higher than those in the Canaries. Slightly higher concentrations of ammonium were obtained in PM2.5 than in PM10 (simultaneous sampling) because of losses of NH4 Cl (gas) from the PM10 Flter during the sampling (NH4 NO3 + NaCl → NaNO3 (particle) + NH4 Cl (gas)). This negative artifact is much less pronounced in the PM2.5 Flter given the major coarse mode of occurrence of NaCl (mostly retained by the impactor inlet). 3.1.3. Trace elements Levels of trace elements were relatively low at all sites (Tables 3 and 4). Pb levels in PM10 were in the range 20–100 ng=m3 at urban and industrial sites and 8 ng=m3 at the Bemantes rural background site (¡ 500 ng=m3 , the EU limit value for 2010). The highest levels of Sn, Zn, Mn, Ni, Cr and Mo were recorded at Llodio (4–20 times higher than at the other sites) probably because of the emissions from steel and paint plants located near this site. Similarly, the highest levels of Cu and As were recorded at Huelva (3–5 times higher than at the other sites), probably because of the emissions from the nearby metallurgical industry. Levels of V measured in Barcelona are three times higher with respect to the other sites probably because of the in9uence of the emissions of a nearby fuel-oil power plant.

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Table 3 Mean levels (ng=m3 ) of trace elements in PM10 from the seven sampling stations PM10

Li Sc Ti V Cr Mn Co Ni Cu Zn Ga Ge As Se Rb Sr Zr Mo Cd Sn Sb Cs Ba La Ce Pr Nd Sm Gd Dy Er Yb Hf Ta W Tl Pb Bi Th U

Sagrera

Llodio

Bemantes

Alcobendas

Huelva

Canaries

Tarragona

0.7 0.2 84 15 8 23 0.4 7 49 98 0.3 0.3 1.5 1.1 1.8 6 4 4 0.7 4 10 0.1 41 0.58 1.31 0.14 0.55 0.09 0.12 0.10 0.08 0.06 0.2 0.2 0.3 0.3 57 0.4 0.3 0.2

0.4 0.1 25 8 25 87 0.5 33 33 420 0.4 0.2 1.8 2.8 1.1 3 3 16 1.2 38 2 0.1 14 0.28 0.39 0.06 0.15 0.03 0.09 0.04 0.04 0.05 0.2 0.05 0.7 0.4 103 0.5 0.1 0.3

0.1 0.1 7 5 1 5 0.1 3 8 16 0.2 0.2 0.4 0.5 0.6 1 3 3 0.2 1 1 0.04 7 0.14 0.24 0.06 0.18 0.04 0.05 0.04 0.06 0.05 0.2 0.05 0.04 0.1 9 0.1 0.1 0.2

0.4 0.3 34 4 2 10 0.2 2 31 84 0.3 0.2 0.7 0.5 1.4 4 4 3 0.3 2 7 0.1 29 0.29 0.66 0.07 0.29 0.07 0.10 0.06 0.04 0.05 0.2 0.1 0.4 0.1 24 0.1 0.3 0.4

0.3 0.2 60 7 2 11 0.4 4 70 51 0.3 0.2 5.4 1.8 1.5 4 3 5 0.8 2 4 0.1 16 0.47 0.89 0.11 0.47 0.10 0.15 0.12 0.10 0.11 0.2 0.2 0.1 0.2 37 1.7 0.4 0.5

0.3 0.2 52 8 2 11 0.3 4 23 14 0.2 0.1 0.3 0.3 0.8 6 3 2 0.2 0.5 3 0.1 18 0.51 1.05 0.13 0.47 0.08 0.11 0.09 0.04 0.04 0.1 0.1 0.1 0.1 15 0.1 0.3 0.3

0.4 0.3 23 8 3 9 0.2 4 33 35 0.2 0.1 0.8 0.5 0.8 5 2 2 0.3 2 7 0.1 12 0.20 0.62 0.11 0.29 0.06 0.12 0.08 0.05 0.07 0.2 0.1 0.2 0.3 26 0.2 0.2 0.3

Measurements from January to December 2001, based on the analysis of 84 to 90 samples per site, distributed along the year with a moving sampling strategy.

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Table 4 Results from the source contribution analysis (g=m3 and % of PM10 mass) carried out at 10 selected sites

PM10 N TraHc Industriala External Marine Crustal Undet.

TraHc Industriala External Marine Crustal Undet.

Mon (g=m3 )

Bem (g=m3 )

Hue (g=m3 )

Alc (g=m3 )

Llo (g=m3 )

Tarr (g=m3 )

Can (g=m3 )

Madrid (g=m3 )

L’Ho (g=m3 )

Barce (g=m3 )

22.0 132

18.9 87

38.0 91

32.2 84

31.7 85

37.4

43.9 88

47.7 69

49.5 115

46.2 90

2.9 5.7

4.8 3.3

12.9 11.9

10.7 8.9

6.9 10.8

11.2 10.5

22.9 8.6

16.5 9.5

14.8 14.0

0.7 5.8 6.6

2.6 6.7b 1.5

1.7 10.0 1.1

1.8 9.6 0.3

2.3 8.2 3.3

3.4 11.5 0.4

2.3 4.5 4.5 15.8 14.7 2.9

1.4 12.4 2.4

2.0 13.0 8.5

2.2 14.6 0.3

%

%

%

%

%

%

%

%

13 26

25 17

33 32

34 28

22 34

30 28

5 26 30

14 36 8

5 27 3

6 31 1

7 26 11

9 32 1

5 10 10 35 33 7

%

%

48 18

33 20

32 30

3 26 5

4 26 17

5 32 1

a

The industrial factor may include di8erent industrial contributions as well as the “combustion” factor. At Bemantes station an important fraction of the crustal contribution is due to the contribution of a nearby power plant. b

The averaged trace element levels (at seven sites) in PM2.5 vs PM10 were determined for 2001. Although signiFcant site-to-site variations were observed, around 80% of Cu, Ni, As, Cd, Bi, Ge, Se, Th and U in PM10 was present in the PM2.5 fraction. This proportion decreased down to 65–80% for Mo, Li, Zr, Cs, Pb, Zn and V, and down to ¡ 65% for Sr, Sb, Mn, Ti, Rare Earth Elements, Ba, Ga, Cr, Sc and Co. 3.2. PM sources Using the approach of Lenschow et al. (2001) discussed above, Fig. 5 shows the results of the decomposition of the PM10 and PM2.5 components in the contributions from the regional background, the city background (background levels of emissions such as traHc, construction, demolition and domestic heating) and road traHc (motor emissions and tire, pavement and brake abrasion products) from the street-canyon where the station is located. These contributions to the bulk PM10 and PM2.5 levels are summarized below as a function of the area and type of site. 3.2.1. Regional and rural background sites As shown in Fig. 5, background secondary inorganic phases (sulfate ammonium and nitrate) account for only 20% of PM10 (5 g=m3 ) in the Canary Islands, 30% (5 g=m3 ) in the Atlantic regions of the Iberian Peninsula and for 35% (7:5 g=m3 ) in the rest of the Peninsula. Conversely, the mineral background fraction increases from only 13% (2:5 g=m3 ) in the Atlantic regions, to

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Fig. 5. Summary of the segregated PM10 and PM2.5 chemical mass balance obtained for urban curb-side sites, urban-background and rural background sites from Spain in 1999–2001.

25–30% (5–7 g=m3 ) in the rest of the Iberian Peninsula and the Canary Islands. The marine aerosol contribution to PM10 may be estimated from around 5% (1 g=m3 ) in the Central areas to 15% (2:5 g=m3 ) in the coastal areas of the Iberian Peninsula, but it reaches around 35–40% (11 g=m3 ) in the Canary Islands. Finally, the organic and elemental carbon concentrations account for 10–25% (2.5–4:5 g=m3 ) of the PM10 levels from the Mediterranean to the Atlantic regions. Given the coarse distribution of the marine aerosol and mineral elements, fewer variations of these components were detected in PM2.5 at the di8erent sites with respect to PM10. Thus, as shown in Fig. 5, the fraction of background secondary inorganic phases accounts for 35–45% of PM2.5 (4–6 g=m3 ), the mineral background for around 10–20% (1.5–3 g=m3 ), the marine aerosol contribution for 5–10% (0.5–1:5 g=m3 ) and the organic and elemental carbon for 20% (2–3:5 g=m3 ). 3.2.2. Urban background sites As shown in Fig. 5, around 60% (20 g=m3 ) of the PM10 mass is attributed to regional background particulate matter in urban background areas of Spain. The additional 40% (12–14 g=m3 ) is made up of the city background contribution of which one-third (4–5 g=m3 ) is mineral dust (mainly road erosion, construction and demolition dust). Another third is carbonaceous material mainly arising from traHc emission, heating/air conditioning and other urban sources, and the remaining third is ascribed to unaccounted mass (a large fraction of which is water).

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In the case of PM2.5 (Fig. 5), the regional background accounts for 60–70% (11–13 g=m3 ) of the urban background levels. The additional 30–40% (8–10 g=m3 ) is attributed to the city background input of which 20% (1:5 g=m3 ) is made of city mineral dust, 50% (4 g=m3 ) of carbonaceous material and the remaining 30% (3 g=m3 ) to unaccounted mass. It should be pointed out that around 20–35% of the PM10 city background mineral dust input is present in PM2.5, whereas 80–90% of carbonaceous particle input is also present in PM2.5. 3.2.3. Curb-side sites At curb-side sites the regional and urban background particulate inputs are estimated to reach 33–50 and 25–30% of the PM10 mass, respectively. The additional 20–30% (10–12 g=m3 ) is supplied by local traHc from the monitored street. As shown in Fig. 5, at least 85% of this curb contribution is made up of road dust (6:5 g=m3 ) and carbonaceous particles from exhaust emissions and tire abrasion (6 g=m3 ). As for the urban background sites, 30–35% of the PM10 local road dust input at curb-side sites is present in PM2.5, whereas ¿ 90% of the curb PM10 carbonaceous particle input at these sites is also present in PM2.5. In the case of PM2.5 (Fig. 5) contributions of regional, urban background and local curb emissions are similar to those reported for PM10 (35–50/25–35/25–33%, 10–13/7–11/7–10 g=m3 ). At least 65% (5:5 g=m3 ) of this curb contribution is ascribed to carbonaceous particles from exhaust emissions and to tire abrasion, and 25% (2 g=m3 ) to road dust from the monitored street. 3.2.4. Industrial contribution Data listed in Table 2 show that at some urban background and curb-side sites, a signiFcant fraction of PM10 and PM2.5 is made up of secondary inorganic species, which is much higher than those determined at regional and at most urban background sites. This is probably an artifact introduced by the fact that two of the three curb-side sites and one urban background site investigated are located in highly industrialized areas in the Mediterranean region (Barcelona and Tarragona) where higher levels of sulfate, and especially of nitrate are usually recorded. Bearing in mind the di8erences in the levels of secondary inorganic species, it may be concluded that the surplus mass of inorganic secondary material ranges from 3 to 8 g PM10=m3 and 1–6 g PM2.5 in highly industrialized areas. The carbonaceous fraction is only slightly in9uenced by industrial emissions since the ratio of organic and elemental carbon to inorganic secondary species ranges from 1.2 to 1.9 in PM10 and 1.3–2.2 in PM2.5 in Madrid, Alcobendas and in the Canaries, whereas this ratio is constant in the range 0.7–0.8 in PM10 and 0.7–1.1 in PM2.5 at the aforementioned industrialized urban sites. 3.3. Source apportionment Bearing in mind all the above PM10 and PM2.5 contributions reported for regional background, urban background and curb-side sites (Figs. 5 and 6), it becomes evident that the natural contribution accounts for 15–20, 20–25 and 30–40% of PM10 (7–9 g=m3 ) in the Iberian Peninsula, respectively. In the Canary Islands, this natural fraction increases markedly up to 45–65% (18–19 g=m3 , Fig. 5) of the PM10 mass measured at urban and regional background sites. The natural input in PM2.5 is considerably reduced but is still present in around 11–25% of the bulk PM2.5 mass

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Fig. 6. Source contribution analysis (% of PM10 mass) at the selected monitoring stations.

(3–4 g=m3 ), depending on the type of site. These should be considered as minimum values given that the natural organic contribution is not included. Following the source apportionment analysis strategy described by Thurston and Spengler (1985), the di8erent sources which contribute to the levels of PM10 and PM2.5 were identiFed, and their contributions have been quantiFed on a daily and annual basis for PM10. The lower number of PM2.5 samples and the narrower range of sources which contribute to this fraction prevented the analysis from being suHciently accurate to quantify the PM2.5 sources. Between 4 and 6 PM10 sources were identiFed by means of the source contribution analysis (Table 4 and Fig. 6). The majority of the sources such as the crustal, industrial (with di8erent chemical proFles according to the site), marine and traHc factors were common to all stations (Table 4). The crustal and traHc sources account for the same type of emissions at the di8erent sites, whereas the industrial sources at Llodio and Huelva depend on the di8erent industrial activities (Fig. 6). Furthermore, at three sites (A Coru˜na, Barcelona and Las Palmas) a “combustion” factor was deFned, which accounts for the emissions from power plants. At the Llodio and Las Palmas stations, a factor deFned as “external” was determined, which includes emissions which are not emitted locally and is mainly characterized by the presence of ammonium sulfate (tracer of regional and long-range transport). As expected, the contribution of the di8erent sources is highly variable according to the type of sampling station. The results obtained at the sites in the Iberian Peninsula are also very di8erent

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from those obtained in the Canary Islands. TraHc contributions to PM10 levels at urban background stations in the Peninsula vary from 22 to 34% (7–15 g=m3 ), but may reach 48% (23 g=m3 ) at traHc sites (Table 4, Fig. 6). This contribution reaches only 5% (2 g=m3 ) at the urban background site in the Canaries. TraHc contributions attain 11–25% of the PM10 levels (3–5 g=m3 ) at the rural stations in the Iberian Peninsula. The industrial factor also exhibits important variations as a function of the study area. In the Peninsula, this contribution at urban background stations under industrial in9uence ranges from 20 to 34% (9–12 g=m3 ). At rural sites with industrial in9uence, these contributions account for 15–25% of the PM10 mass (3–6 g=m3 ). It should be noted that the highest industrial contribution to rural sites is registered at Monagrega. In this particular case, these contributions were mainly composed of SO24− and NO− 3 , which are related to summer regional episodes, and therefore comprise both local and regional industrial contributions (26% of the PM10 mass, 6 g=m3 ). In the Canaries, industrial emissions only account for 10% of the PM10 mass (4:5 g=m3 ). This contribution is similar to that determined for the external anthropogenic emissions (10%). Natural sources have a much higher in9uence on PM10 levels in the Canary Islands than in the Peninsula. The marine source represents 35% of the PM10 mass in the Canaries (12 g=m3 ), but only 3–15% in the Peninsula (0.7–3:4 g=m3 ). In the Central regions (Madrid and Monagrega), this fraction contributes with only 0.5–1:0 g=m3 whereas in the coastal areas it reaches 2–3 g=m3 . Finally, the crustal load in PM10 ranges from 24–36% at all sites, including the one in the Canary Islands (33%). However, in absolute values, the contribution of the crustal factor is maximal in the Canary Islands 11–15 g=m3 . In this case, a high proportion of the crustal contribution has an African origin (mean daily dust loads reaching 100–600 g PM10=m3 are often recorded during the frequent African episodes, known locally as “calima”). The crustal component at the Barcelona station attained similar values (15 g=m3 ). However, this is due to road dust resuspension and other urban mineral emissions rather than to African contributions. Moreover, crustal contributions at urban stations (Escuelas Aguirre, Huelva, Tarragona, Llodio, L’Hospitalet) are high (8–12 g=m3 ). If we subtract the 5:5 g=m3 crustal contribution detected at the Monagrega rural station from the urban background levels of crustal material, it may be concluded that there is a crustal contribution of 2–7 g=m3 at urban sites. This contribution is therefore related to the mineral city background arising from anthropogenic activities (demolition, construction, road works, traHc). If we subtract the levels of crustal components recorded at urban background from those attained at roadside sites, it can be concluded that the local pavement erosion of the monitored road accounts for 3–5 g=m3 of crustal input to the annual PM10 mean levels. Thus, an important proportion of the crustal load quantiFed with the receptor modeling may be attributed to urban anthropogenic sources such as traHc. Road dust may be deposited onto the pavement and, in the absence of rain episodes, the resuspension of this dust could increase the crustal load of PM10. The source receptor model will not always associate this dust with traHc tracers such as nitrate or carbonaceous aerosols. The same emission sources found to be responsible for major variations of PM10 levels were identiFed for PM2.5 using the factor analysis. However, as discussed above, the marine and the crustal factor contributions were markedly reduced with respect to PM10. However, in relative values, the crustal contribution may still account for around 20% of the PM2.5 mass, especially at curb-side sites.

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3.4. Chemical speciation of peak PM10 and PM2.5 episodes In order to determine the major causes of the exceedances of the limit value for 2005 and 2010 (EU Directive 1999/30/EC, 50 g=m3 ), the mean levels of PM10 components for days with PM10 ¿ 50 g=m3 at the following sites are shown in Fig. 7: Barcelona (curb-side site with industrial in9uence, data from 2001), Madrid (curb-side site, data from 1999 to 2000), Llodio (industrial urban background station, data from 2001) and the Canary Islands (urban background station, data from 2001). The results show the prevalence of three PM10 fractions at the sites studied: mineral dust, secondary inorganic phases and carbonaceous components. In the Canary Islands, the mineral fraction and the marine aerosol are clearly dominant during the days that exceed the limit value, with mean levels of 33 and 18 g=m3 (42 and 23% of the bulk PM10 levels), respectively. The proximity of the African continent and the Atlantic in9uence account for the very high natural contribution measured during these days at this site. At the industrial sites (Llodio and Barcelona), the secondary inorganic species account for 14–26 g=m3 (22–44%) of the bulk PM10 load on the days exceeding the limit value. The high traHc in9uence in Barcelona also accounts for a large contribution of mineral dust (24 g=m3 , 37% of PM10 mass) and carbonaceous matter (14 g=m3 , 21%). Finally, the carbonaceous (21 g=m3 ) and mineral (22 g=m3 ) fractions constitute 63% of PM10 on the days exceeding the limit value at the curb-side site in Madrid given that traHc is the main contributor to PM on those days. On the days exceeding 35 g PM2:5=m3 (8–15 days at curb-side sites and from 1 to 6 days at urban background sites over around 50 days per site, Fig. 7), the anthropogenic local contribution is still dominant at all sites with the exception of the Canary Islands. Thus, at Las Palmas 64% of PM2.5 mass is attributed to mineral dust on those days, whereas secondary inorganic species and organic and elemental carbon only account for 15%. These proportions are inverted at the urban background and traHc sites in the Iberian Peninsula, where secondary inorganic and carbonaceous material accounts for 62–72% of the PM2.5 mass on the days exceeding 35 g PM2:5=m3 . It should be pointed out that mineral matter accounts for around 20% of the PM2.5 mass on those days at curb-side sites. Sporadically, African dust outbreaks over Spain may induce very high PM10 and PM2.5 levels. In the Canary Islands, daily PM10 and PM2.5 levels may reach up to 400 and 80 g=m3 , respectively, during these events, with ¿ 80% of the PM mass being composed of mineral dust. Typical PM2.5/PM10 ratios registered during African dust outbreaks reach 0.4 in the Canary Islands and Huelva, 0.5 in Barcelona and Alcobendas and 0.7 in Llodio and Bemantes. Consequently, the simultaneous measurement of PM10 and PM2.5 levels is not suHcient to detect dust outbreaks since the PM2.5/PM10 ratio varies regionally. The dust outbreaks also in9uence levels of PM2.5 and PM1. Mean daily PM10 and PM2.5 levels up to 199 and 74 g=m3 were recorded in the Canary Islands. The di8erence in PM2.5/PM10 ratios is probably attributed to the fact that the dust outbreaks a8ecting Northern Spain occur mainly in winter following anticyclone trajectories over the Atlantic (Viana, Querol, Alastuey, Cuevas, & RodrNOguez, 2002). Thus, the air masses are transported over considerable distances with the result that important grain size segregation takes place. Furthermore, recent studies have demonstrated that in February–March, the dust plume is made up of a mixture of carbonaceous aerosols from biomass combustion and dust (Kaufman et al., 2003). However, in Eastern and Southern Spain, the dust outbreaks also occur in spring and summer with direct and shorter transport from the Sahara.

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Fig. 7. Chemical speciation of days exceeding the PM10 daily limit value (50 g=m3 ) and 35 at urban background, curb-side and industrial sites. SIA: secondary inorganic aerosols.

4. Conclusions Wide variations in PM levels were found among the di8erent geographical areas in Spain. These variations also depend on the type of monitoring site, i.e. rural background, sub-urban or industrial

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background, and curb-side or street-canyon stations. PM levels range from 15–20 g PM10=m3 in rural areas, to 45–50 g PM10=m3 at curb-side stations. The variation of PM2.5 ranges from 9–14 g PM2:5=m3 at rural background stations to 25–35 g PM10=m3 at curb-side sites. The chemical composition of PM10 and PM2.5 exhibits geographical variations as well as seasonal patterns. The carbonaceous aerosol is the major contribution to PM10 and PM2.5 size fractions, presenting a clear winter maximum. The mineral contribution is the second major component of PM10 although it is reduced in PM2.5. There is a marked traHc in9uence on levels of mineral components, the highest levels being recorded at curb-side or street-canyon sites. A considerable in9uence of the geographical features on the mineral levels in PM10 and PM2.5 was detected. The highest urban background levels were recorded in the Canaries. Secondary inorganic compounds constitute the second major component of PM2.5. NO− 3 levels exhibit a winter maximum. Moreover, this component shows a distinct trend, increasing towards the Eastern part of the Peninsula. Atmospheric characteristics such as higher photoreactivity and regional dynamics contribute to this e8ect. Based on a source apportionment study, traHc, industry and natural sources were found to account for 30–50, 15–35 and 15–30% of PM10 mass in most urban areas. Nevertheless, contribution from di8erent sources is highly dependent on the type of location. From the point of view of daily limit value, the mineral contribution is dominant in the Canary Islands on the days of PM10 exceedance because of their proximity to the African continent. This contribution also accounts for a large part of the PM10 mass at traHc sites although carbonaceous aerosol may account for the major part (62%) of the PM10 mass at curb-side sites. Secondary inorganic compounds are however more signiFcant in PM2.5 and at industrial and heavy traHc sites. Acknowledgements This study has been partially Fnanced by the Spanish Ministry of the Environment, the Ministry of Science and Technology (REN2001-0659-C03-03) and the Department of Environment of the Autonomous Government of Catalunya (Generalitat de Catalunya). The authors would like to thank the regional Governments of the Xunta de Galicia, Comunidad AutNonoma de Madrid, Junta de AndaluciNa, Generalitat de Valencia, Generalitat de Catalunya, Gobierno AutNonomo de Canarias and PaNOs Vasco (Euskadi) for their support and collaboration. NASA /Goddard Space Flight Center, SeaWIFS-NASA Project SKIRON-University of Athens and Navy Research Laboratory-USA are also acknowledged for their contribution with TOMS, satellite images, SKIRON dust maps and NAAPs aerosol maps, respectively. Meteorological analyses were provided by the NOAA-Cires Climatic Diagnostic Center Boulder (CO), from their Web site http://www/cdc.noaa.gov/. The authors gratefully acknowledge the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model and/or READY website (http://www.arl.noaa.gov/ready.html) used in this publication. References ArtNOn˜ ano, B., Salvador, P., Alonso, D. G., Querol, X., & Alastuey, A. (2003). Anthropogenic and natural in9uence on the PM10 and PM2.5 aerosol in Madrid (Spain). Analysis of high concentration episodes. Environmental Pollution, 125, 453–465.

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