PM10 speciation and determination of air quality target levels. A case study in a highly industrialized area of Spain

Science of the Total Environment 372 (2007) 382 – 396 www.elsevier.com/locate/scitotenv

PM10 speciation and determination of air quality target levels. A case study in a highly industrialized area of Spain M.C. Minguillón a,b, ⁎ , X. Querol a , A. Alastuey a , E. Monfort b , E. Mantilla c , M.J. Sanz c , F. Sanz c , A. Roig d , A. Renau d , C. Felis e , J.V. Miró e , B. Artíñano f Institute of Earth Sciences “Jaume Almera”, CSIC, Barcelona, Spain Instituto de Tecnología Cerámica, Universitat Jaume I, Castelló, Spain c Centro de Estudios Ambientales del Mediterráneo, CEAM, Valencia, Spain d Experimental Sciences Department, Universitat Jaume I, Castelló, Spain e Conselleria de Territori i Habitatge, Generalitat Valenciana, Spain f CIEMAT, Madrid, Spain a

b

Received 5 May 2006; received in revised form 9 October 2006; accepted 13 October 2006 Available online 30 November 2006

Abstract The paper shows how PM speciation studies allow the evaluation of the strategies to be followed to diminish PM pollution in highly industrialized areas with a large number of potential pollution sources. Evolution of levels and speciation of PM10 in the ceramic producing area of Castelló (East Spain) was studied from April 2002 until December 2005. PM10 levels were measured at one rural (Borriana-rural), two suburban (Almassora and Onda) and three urban (Borriana-urban, L'Alcora and Vila-real) sites, all influenced by the ceramics industry. Average PM10 levels varied between 27 and 36 μg/m3 for the study period. Evaluation of 1996–2005 PM data from Onda shows a clear decrease of PM levels since the beginning of 2002. Summer peak levels and winter minima occurred at both rural and suburban sites, whereas urban sites had no clear seasonal trend, with high PM10 episodes being due variously to local, regional, and African dust intrusion events. PM10 chemical analysis at four of the sites showed the dominant constituent to be mineral matter, exceeding by 5–12 μg/m3 the usual ranges of annual mineral loadings in PM10 at comparable Spanish urban or regional background sites with no industrial influence. Given current PM10 loadings, we recommend a lowering target of 3–5 μg/m3 of the annual mean at the urban sites, which should be achievable given available emission abatement techniques. © 2006 Elsevier B.V. All rights reserved. Keywords: PM; Primary emissions; Air quality; Ceramic industry; Speciation; Spain

1. Introduction The measurement of levels of atmospheric particulate matter (PM) is a key parameter in air quality monitoring ⁎ Corresponding author. Institute of Earth Sciences “Jaume Almera”, CSIC, Barcelona, Spain. Tel.: +34 93 409 54 10; fax: +34 93 411 00 12. E-mail address: [email protected] (M.C. Minguillón). 0048-9697/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2006.10.023

across the world owing to the cause/effect relationship between exposure PM levels and health impacts (WHO, 2003) and their influence on the Earth radiative balance (Sokolik and Toon, 1996). As a result of these health and environmental impacts, PM standards have been developed, especially for the PM fraction finer than 10 μm (PM10 or thoracic fraction) and 2.5 μm (PM2.5 or alveolar fraction). In the European Union (EU), the Air Quality

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Directive (1999/30/EC) established for 2005 an annual limit value of 40 μgPM10/m3 and a daily limit value of 50 μgPM10/m3 for the 90.4 percentile (equivalent to limiting the number of daily exceedances per year to 35 days when the data coverage is 100%). Furthermore, the new evaluation of the above directive suggests additional PM2.5 limit values (25 μg/m3 on an annual basis, including hotspots). The compliance of the above requirements on annual limit values at most urban background sites in the north of the EU should not pose a problem in the near future, but predictions are more pessimistic for hotspots (urban kerbside sites, canyon streets and industrial spots) in the east, centre and south of the EU (European Commission, 2004). Some studies have already pointed out that the daily PM10 limit value for 2005 is stricter than the annual one, and that many areas will have difficulty in meeting this air quality requirement (European Commission, 2004; Querol et al., 2004a,b). In addition to the PM mass limit values, also based on health impact criteria, recent EU standards set target (Cd, As, Ni) and limit (Pb) values for metals and PAH (Directives 2004/107/EC and 1999/30/EC). Environmental technologies may have to be adopted in specific industrial spots to reach the target values. Around 80% of the European Union ceramic tile and ceramic frit manufacturers are concentrated in two areas,

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forming the so-called ceramic clusters — in Modena (Italy) and in Castelló (Spain). Based on the studies in the literature (Alastuey et al., 2000; Querol et al., 2001) and on the data shown on Internet by the regional authorities (http://www.cma.gva.es/intro.htm, http://www.arpa.emr. it) derived from the air quality networks in these areas, it can be deduced that metals and PM10 are the two parameters of most concern regarding EU legal requirements. In this context this paper reports on PM10 levels and chemical compositions from an area surrounding Castelló, and comments on the reductions required to bring pollution levels down to more appropriate levels. 2. The study area 2.1. Industrial activities The ceramic producing area of Castelló extends along the Millars and Sec river basins from the coast to the interior of the province of Castelló in Eastern Spain (Fig. 1). This area is the largest ceramic producing zone in the EU, accounting for approximately 6.4 × 108 m2/year of ceramic tiles and 9 × 105 tonnes/year of ceramic frits, glazes and pigments (processed subproducts for tile manufacturing). This industry consumes a large supply of powdered clay (around 12 million tonnes/year) that comes from sources which include opencast quarries

Fig. 1. Location of the monitoring sites and mean PM10 values (μg/m3) for the study period.

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Table 1 Location, type and measuring method of measuring sites Station

Latitude

Longitude

Altitude (m.a.s.l.)

Type of site

Measuring method

Almassora (AM)

39° 56′ 01″ N

00° 03′ 20″ W

37 m

Beta attenuation

Borriana-rural (BOrural) Borriana-urban (BOurban) L'Alcora (LA)

39° 54' 32″ N

00° 03′ 54″ W

37 m

39° 53′ 38″ N

00° 05′ 10″ W

20 m

40° 04′ 07″ N

00° 12′ 43″ W

175 m

Onda (ON)

39° 57′ 46″ N

00° 14′ 00″ W

163 m

Vila-real (VR)

39° 56′ 30″ N

00° 06′ 21″ W

60 m

Rural-industrial background Rural-industrial background Urban-industrial background Urban-industrial background Suburban-industrial background Urban-industrial background

within the cluster area (Sant Joan de Moró and Mas Vell, Fig. 1). Other important starting materials used in the ceramic industry include a large variety of natural and synthetic products, such as feldspars, zircon or boracic components (Criado et al., 2004). The channelled (stack) emissions from tile manufacturing and the fugitive emissions from the storage, handling and transport of the body raw materials (clays, granulated product, etc.) probably account for the largest fraction of the local anthropogenic particulate emissions in the study area. However, PM emissions from the manufacture of pigments, frits and glazes have probably a greater impact on the levels of heavy metals than on PM mass. Other particulate emission sources such as intensive road transport, frequent biomass combustion from intensive orange tree cultivation, sea spray, as well as other important industrial activities in the area such as a fuel oilfired power station and a petrochemical industry (both located in El Grau, to the east of the ceramic cluster) also contribute to the total PM loadings. Finally, important sources of secondary PM include the precursor emissions of VOCs, NOx and SO2 from the high temperature ceramic processes, power generation, petrochemistry and biomass combustion. Notable improvements in the air quality associated with the Spanish ceramic cluster started in the late 1980s and early 1990s, when natural gas completely replaced oil as a fuel. Since the late 1990s, environmental technologies to abate the emissions of primary PM have been progressively implemented. In channeled emissions, the most popular technologies are bag filters or Venturi wet systems, whereas for fugitive emissions a variety of technologies have been introduced to reduce dust emissions in bulk storage (wetting, walling, partial or total enclose), in dusty operations (applying enclosure with air suction and a filter system) and in truck road transport (paving and load enclosure).

Beta attenuation Gravimetric Gravimetric Beta attenuation (TSP) Gravimetric (PM10) Gravimetric

2.2. Atmospheric dynamics The setting of this problematic focus for PM emission is located in a complex Mediterranean atmospheric environment. The intensive convective dynamics, the breeze circulation, the low rainfall, the soils with poor vegetal coverage and the frequent high particulate Sahara air-mass intrusions further complicate the monitoring of the impact of anthropogenic particulate emissions on air quality (Rodríguez et al., 2002). The study area (Fig. 1) includes the Castelló alluvial plain (La Plana) which is bounded in the north by the Palmes mountain chain (6–7 km from the coast), the highest peak of which is Mt. Bartolo (780 m.a.s.l.). The Viuda valley is located to the North of the Castelló alluvial plain and has a NE–SW direction defined by the prelittoral Esparraguera and Galcerán ranges. The Millars basin, with an approximate NW–SE direction, converges on the first range of mountains at a distance of 20 km from the coast. Most of the ceramic factories are located in this intra-basin, in a 200 km2 area between the coastal flat (mainly occupied by residential areas and orange tree plantations) and the mountain chain of La Cruz. In winter, a major NW atmospheric flow prevails, which is regionally and locally channeled by the NW– SE, W–E or N–S valleys crossing the Iberian range. Under this scenario the industrial emissions from the ceramic producing area are transported towards the coastal areas. In summer, the North Atlantic anticyclone is reinforced occupying the northern latitudes. Weak-gradient conditions over the Iberian Peninsula and intense ground heating give rise to the Iberian Thermal Low (ITL, Millán et al., 1997), owing to thermally induced local and meso-scale circulations. During the daytime, the sea breeze is channelled along the bottom of the valleys up to 60–80 km inland (Millán et al., 1996,

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1997, 2000; Martín et al., 1991), whereas at the top of the mountains and valley-slopes the atmospheric dynamics are governed by a combination of sea breeze and up-slope winds. During the evening and night a reversal in the breeze takes place. This circulation results in good ventilation in the valleys but hinders airmass renovation on a regional scale due to re-circulation of the air masses (Salvador et al., 1999), and so favors the build up of secondary air pollutants (Millán et al., 1991, 1992, 1997; Querol et al., 1999; Rodríguez, 2002; Rodríguez et al., 2002). 3. Methodology 3.1. Sites and PM sampling Fig. 1 and Table 1 show the location of 6 stations belonging to the air quality monitoring network of the Autonomous Government of Valencia (Generalitat Valenciana) selected for this study. Data on ambient air levels of TSP have been available at the Onda station since 1996. These levels were measured by means of

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real-time beta attenuation equipment. Since April 2002, data on PM10 have been available from all the stations, with the exception of Borriana-rural and Almassora (starting April 2003) and Borriana-urban (starting June 2004). PM10 levels were measured by means of a high volume sampler DIGITEL DH-80 at Onda (ON), Vilareal (VR), Borriana-urban (BO-urban) and L'Alcora (LA) and with real-time beta attenuation equipment at Borriana-rural (BO-rural) and Almassora (AM). These PM data were supplied by the Direcció General de Qualitat Ambiental, Conselleria de Territori i Habitatge. Furthermore, data on PM10 levels measured at Onda with the DH-80 equipment for 5 months in 1999 were obtained from Rodríguez (2002). Almassora (AM): rural-industrial background station with influence of industrial and road traffic emissions from the area between the towns of Vila-real and Castelló. The station is located in the Millars valley (5 km from the coastline) and therefore, in addition to immediately local emission sources, it is monitoring the atmospheric contributions received from the main valley in the study area.

Fig. 2. Wind speed and direction at LA and ON (2002); wind speed and direction and PM10 (showing diurnal minimum and nocturnal maximum) at BO-rural (2004).

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Borriana-rural (BO-rural): rural-industrial background station situated in an orange grove between AM and BO-urban. This site is indirectly influenced by the nearby industrial area, road traffic emissions and by the atmospheric flow of the Millars Valley. The following monitoring stations were selected for PM10 sampling and analysis: Vila-real (VR): urban background site located in the southern part of the town of the same name. This site is situated in the lower reaches of the Millars Valley, 10 km from the coastline, in the midst of a ceramic producing area. Borriana (BO-urban): urban background station located in the Riu Sec valley between VR and the coast. It is situated 4 km from the industrial town of Vila-real to the east of the ceramic cluster, from where it can receive pollutants, transported by the nocturnal land breeze and the NW wind flows (prevailing in winter–autumn, Fig. 2). Onda (ON): suburban industrial background station located in the Riu Sec valley near the town of Onda, 20 km from the coast and relatively isolated from the Millars valley flow, which governs the transport of PM emitted from the largest industrial hotspots of the area. The station is situated in an open area with no direct influence of industry or road traffic, on the leeward side of the nearby ceramic industries, from where it receives

the industrial emissions during sea breeze conditions (in addition to urban and traffic emissions). L'Alcora (LA): urban background station located in the town of L'Alcora in the western part of the ceramic producing zone of Castelló, upstream in the Millars Valley. Like Onda, this site will be more influenced by industrial emissions when the sea or slope breezes are active (diurnal periods from March to October, Fig. 2). Sampling of PM10 was carried out using circular filters of quartz glass fibre (15 cm, QF20 Schleicher and Schuell). Two daily (00:00 to 23:55) filters per week (including weekends) were selected for chemical characterization. After sampling, PM filters were placed for 24 h in a desiccator at room temperature and then PM10 levels were obtained by standard gravimetric methods. 3.2. Chemical analysis Samples were treated and analyzed to determine the levels of major components following the procedure of Querol et al. (2001). This was based on the analysis of major elements by ICP-AES (in a previously acid digested, with HNO3:HF:HClO4, 1/2 fraction of each filter), soluble anions by Ion Chromatography, ammonium

Table 2 Mean annual PM10 levels and number of exceedances of 50 μg/m3 measured at VR, LA and ON from April 2002 to December 2005, at BO-urban from June 2004 to December 2005 and at BO-rural and AM from April 2003 to December 2005, number of days of measurement per year (n), impact index (% of contribution to the annual mean) for days with Atlantic advection (ATL), North African advection (NAF), Mediterranean advection (MED), European advection (EU) or with no dominant advection (REG)

Vila-real

L'Alcora

Onda

Borriana-urban Borriana-rural

Almassora

2002 2003 2004 2005 2002 2003 2004 2005 2002 2003 2004 2005 2004 2005 2003 2004 2005 2003 2004 2005

Mean PM10 (μg/m3)

N of daily exceedances (N50 μg/m3)

n

35.6 36.4 36.7 35.5 36.4 32.9 33.3 32.7 24.6 26.5 28.7 26.6 35.1 36.3 32.2 32.1 36.7 35.2 38.1 35.6

19 40 46 28 43 33 39 24 7 17 16 9 11 32 7 22 49 25 61 36

205 341 283 236 265 313 283 254 257 306 191 191 123 309 244 359 354 249 353 334

Contribution (%) to the annual mean ATL

NAF

MED

EU

REG

69 52 50 49 62 49 52 49 60 47 43 41 54 52 47 49 49 48 51 52

17 27 30 15 20 27 27 15 22 29 34 22 21 14 31 28 17 31 27 15

2 3 1 1 5 3 1 1 4 3 b1 b1 7 1 2 3 b1 2 2 b1

7 8 8 3 7 10 7 3 8 9 10 b1 3 5 6 7 4 6 7 4

5 10 11 32 6 11 13 32 7 12 13 36 14 29 15 13 29 13 13 29

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were b10%, with the exception of P and K for which a 15% error was determined. In addition, experimental equations were used to indirectly determine the content in silica (SiO2 = 3*Al2O3; Dulac et al., 1992; Molinaroli et al., 1993; and our experimental data using nitrate cellulose filters in parallel), carbonate (CO32− = 1.5*Ca+2.5*Mg, based on stoichiometric relations) and organic matter + elemental carbon (OM + EC). The last concentration was calculated from the fraction of organic + elemental carbon (OC +EC), determined by subtracting the mineral carbon (deduced by stoichiometry from CO32− levels) from total carbon, i.e. OC + EC = total-C − carbonate-C. Then, to account for the mass of unmeasured hydrogen and oxygen in organic material, we applied the equation OM + EC = 1.2*(OC + EC) (Eatough et al., 1996; Putaud et al., 2000; Turpin et al., 2000). 3.3. Back-trajectory and meteorological analysis In order to classify each day with PM10 measurements in the period 2002–2005 in accordance with the atmospheric transport scenarios, 5 day back-trajectories (modeling the vertical velocity) were calculated daily for three different altitudes (500, 1500 and 2500 m.a.s.l.) with the HYSPLIT model (Draxler and Rolph, 2003), so that the different source regions of the air masses reaching the study area can be identified. African dust episodes were also identified by means of the evaluation of TOMS-NASA aerosol index maps (Herman et al., 1997), SKIRON aerosol maps (provided by the University of Athens, Kallos et al., 1997), DREAM aerosol maps (Euro-Mediterranean Centre of Insular Coastal Dynamics, http://www.icod.org.mt/modeling/forecasts/ dust_med.htm), NAAPs aerosol maps (Naval Research Laboratory, http://www.nrlmry.navy.mil/aerosol) and satellite imagery supplied by NASA SeaWIFS (McClain et al., 1998). Finally, meteorological data from the air quality network stations were used to support interpretation of results. Fig. 3. Monthly PM10 levels (μg/m3) at LA, VR, ON, AM, BO-urban and BO-rural for the study period.

by Colorimetry-FIA (the latter two techniques on water extractions of a 1/4 of each filter) and carbon by thermooptical methods. Fractions of blank filters were analyzed in the batches of their respective filter samples, and the corresponding blank concentrations were subtracted from each sample. A few mg of the reference material NIST 1633b were added to a fraction of a blank filter to check the accuracy of the analysis of the acidic digestions. For most elements relative analytical errors

4. Results and discussion 4.1. PM10 levels Average PM10 levels for the study period were 34, 27, 36, 36, 36 and 34 μg/m3 for LA, ON, VR, BO-urban, AM and BO-rural, respectively. The levels recorded annually for the study period meet the requirements of the annual (40 μgPM10/m3) and daily (50 μgPM10/m3) limit values considering the margins of tolerance for each year in accordance with 1999/30/CE standard and excluding the

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Fig. 4. TSP and PM10 monthly levels measured at ON, from June 1996 to December 2005.

exceedances coinciding with African dust outbreaks. Current PM monitoring data show that PM2.5/PM10 ratios are around 0.6–0.7 (LA, VR and ON). The mean PM10 levels measured at rural-regional background sites in Spain by Querol et al. (2004a) were 15 to 20 μg/m3, which was 7–12, 14–19 and 16–21 μg/m3 lower than those registered at ON, BOrural and AM, respectively. LA, VR and BO-urban registered PM10 levels of 34 to 36 μg/m3, values in the usual range of Spanish urban background sites (25– 40 μg/m3). However, given the small size of the towns (b45000 inhabitants) the annual levels should be compared with the lower values of the range, yielding a surplus of around 10 μg/m3. PM10 levels were similar or even higher at BO (coastal site, Fig. 1, Table 2) than in the ceramic producing zone owing to the dominant NW transport of pollutants down the Millars and Sec valleys. The industrial origin of the increased PM10 levels measured at BO is corroborated by the daily evolution, characterized by diurnal minima (due to the prevalence of sea breezes with relatively clean marine air masses) and by

nocturnal peak levels (due to the land breeze transport of pollutants from the inland industrial hotspots, Fig. 2). PM10 levels measured at ON are considerably lower than those measured at VR and LA (urban stations), probably because this site is a suburban station and located outside the major atmospheric flow regime of the Millars valley. The monthly levels of PM10 measured at the monitoring stations show that there has been no clear upward or downward trend of PM10 over the 4-year study period (Fig. 3). However, PM10 levels obtained in our study show a decrease of about 5–8 μgPM10/m3 with respect to data from 1999 (Rodríguez, 2002; Alastuey et al., 2000; Querol et al., 2001). Moreover, TSP levels registered since 1996 at ON show a reduction since the beginning of 2002 (Fig. 4, where estimated PM10 data were calculated from TSP data and from the ratio PM10/TSP (0.59), obtained from the periods when simultaneous measurements were available). This decrease can be attributed to the gradual implementation of PM emission abatement techniques in a significant number of ceramic factories.

Table 3 Mean levels of PM10 and number of exceedances considering and excluding exceedances of the 2005 daily limit value (DLV, 50 μg/m3) simultaneously recorded with African dust outbreaks (NAF), at ON, LA, VR, BO-rural, BO-urban and AM Period

ON

LA

VR

BO-rural

BO-urban

AM

April 2002–Dec April 2002–Dec April 2002–Dec April 2003–Dec June 2004–Dec April 2003–Dec 2005 2005 2005 2005 2005 2005 n 944 Mean PM10 27 Range of annual PM10 25–29 Mean PM10 excluding dust outbreaks 26 exceedances n N DLV/year* 14 n N DLV/year* excluding NAF 9 Percentile 90.4 (P90.4) 43 P90.4 excluding dust outbreaks 40 exceedances ⁎ mean of n for years with high availability.

1115 34 33–36 33

1065 36 35–37 35

957 34 32–37 33

432 36 35–36 35

936 36 35–38 35

32

38

36

32

49

21 53 49

23 53 49

22 49 47

22 51 49

32 53 49

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Fig. 5. Number of monthly exceedances of the daily PM10 limit value (50 μg/m3) at LA, VR, ON, BO-urban, BO-rural and AM.

As regards seasonal trends, summer peak levels and winter minima are clearly in evidence at ON, AM and BOrural (Fig. 3). This seasonal pattern is typical of regional background sites, where PM levels increase in summer due to the higher atmospheric mixing, favoring the transport of pollutants from urban or industrial hotspots towards rural areas. At LA, PM10 levels also increase in summer as a consequence of the inland transport of emissions by sea breezes up the Millars valley. At VR and BO-urban there is no clear seasonal trend but a high variation in the levels throughout the year because of the location of the sites. The former site is surrounded by different sources. The latter site is located on the coast, so

that it receives pollutants from inland industrial areas all the year (during summer nights and on most days in winter) and is influenced by local urban pollutants. Maximum PM10 levels were simultaneously measured at all monitoring sites during April 2002, March, June and July 2003 and February and March 2004. The maxima of April 2002, March 2003 and February 2004 (2nd to 16th) are attributable to typical anticyclonic scenarios with thermal inversion episodes, sometimes coupled with a high insolation and high humidity in the early morning, giving rise to the accumulation of locally and regionally emitted pollutants in a thin mixing layer and to the generation of high levels of secondary PM

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Fig. 6. Weekly evolution of PM10, crustal component and OM+EC at VR, LA, ON, BO-urban, BO-rural (only PM10) and AM (only PM10).

due to intensive photochemistry. On the other hand, peak levels of June and July 2003 are attributable to frequent African dust air mass intrusions as reported by MMA (2003, 21 days in June and 13 days in July 2003). If one excludes those days with African dust intrusions, mean PM10 levels during these 2 months actually reduce by up to 18%. Taking a broader view and considering the whole study period, if exceedances of the daily PM10 limit value for 2005 (50 μg/m3) caused by African dust outbreaks (MMA, 2002, 2003, 2004 and 2005) are excluded, the annual mean value decreases only by 1 μg/m3, whereas the 90.4 percentile values decrease by 2–4 μg/m3 and the annual number of exceedances decrease from 14, 32, 38, 36, 32 and 49 down to 9, 21, 23, 22, 22 and 32 at ON, LA, VR, BO-rural, BO-urban and AM (Table 3). The maximum number of exceedances (natural and/ or anthropogenic) of the PM10 daily limit value was frequently recorded from February to April (Fig. 5).

Consequently, it is mainly in this 3-month period when maximum attention should be paid to emission control in order to meet the EU air quality requirements on PM10. Following the methodology of Escudero et al. (2005), each day of the period 2002–2005 was classified in accordance with the air mass transport scenario determined by the back-trajectory analysis. Thus, the scenarios were: dominant Atlantic (ATL), North African (NAF), Mediterranean (MED) and European (EU) advection or with no dominant advection (REG). Percentages of contribution to the PM10 mean annual levels (Impact Index) were calculated for each scenario and each year according to the following equation: IIi ¼ 100⁎ðXi⁎ni =na Þ=Xa ; where IIi is the impact index in % of contribution to the annual PM10 mean of the atmospheric transport scenario ‘i’; Xi is the mean PM10 level for days when the ‘i’

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scenario prevailed; ni is the number of days when the ‘i’ scenario prevailed; na is the number of days with measurements of PM10 levels available, and Xa is the mean annual PM10 level. As shown in Table 2, days with ATL advection contributed from 41 to 69% of the annual PM10 levels. Under this scenario, the long range transport of PM is considerably reduced owing to the Atlantic origin of the air masses; so, most of the PM load has a local or regional origin. However, under the other scenarios (with the exception of REG) a large proportion of the PM load may be attributed to external contributions. Thus, NAF advection scenarios contributed from 14 to 34%, REG scenarios from 5 to 36%, EU scenarios up to 10% and MED scenarios up to 7% to the annual PM10. Contributions from NAF scenarios are higher at ON, BO-rural and AM than at BO-urban, VR and LA. The two latter sites are closer to the industrial emissions and therefore there are more local episodes, which are reflected on the contribution of ATL episodes. The relevance of the local contribution to PM levels is reflected on the weekly evolution. Thus, Fig. 6 shows that PM10 levels slightly decrease at weekends, probably

391

due to the lower road traffic and a reduction in some industrial activities. This pattern is more evident at LA. 4.2. PM10 speciation The analysis of major PM10 components showed that the major constituent in the study area is mineral matter (or crustal component, calculated as the addition of CO32−, SiO2, Al2O3, Ca, K, Mg, Fe, Ti and P) although there are significant differences between sites, specially LA and ON; it accounts for 43–51, 34–41, 37 and 28–39% (15–20, 13–16, 13–14 and 8–11 μg/m3 ) of the mean annual bulk PM10 mass at LA, VR, BO-urban and ON, respectively (Table 4). Secondary inorganic compounds (SIC = sulfate, nitrate and ammonium) levels slightly varied across the study area and period, they account for 16–19, 17–23, 19 and 19–28% (5–7, 6–9, 7 and 5–7 μg/m3 ) of the PM10 mass at LA, VR, BO-urban and ON, respectively. Levels of organic matter plus elemental carbon (OM + EC) were slightly higher at VR (6–7 μg/m3, 16–18% of PM10), where the road traffic influence was expected to be higher, than at LA, BOurban and ON (14–15, 13–14 and 15–20% of PM10; 5,

Table 4 Speciation of PM10 at ON, LA, VR and BO-urban. Annual mean levels, calculated from monthly mean levels ONDA n (days) μg/m Mean PM10** OM+EC CO2− 3 SiO2 Al2O3 Ca K Na Mg Fe Ti P Mn SO2− 4 NO−3 Cl− NH+4 % Crustal OM+EC SIC Sea spray Trace metals Unaccounted

3

L'ALCORA

VILA-REAL

BORRIANA

2002*

2003

2004*

2005

2002*

2003

2004

2005

2002*

2003

2004

2005

2004*

2005

78 26.2 5.2 1.9 3.2 1.1 1.0 0.5 0.7 0.2 0.3 0.03 0.03 0.01 4.5 1.7 0.2 1.0

72 28.4 4.2 2.2 4.9 1.6 1.1 0.6 0.8 0.2 0.4 0.04 0.03 0.01 4.2 0.7 0.2 0.5

58 29.0 4.6 1.8 3.4 1.1 0.9 0.4 0.6 0.2 0.3 0.03 0.02 b0.01 4.3 0.7 0.1 0.6

62 27.3 4.6 2.3 3.6 1.2 1.2 0.4 0.5 0.2 0.3 0.03 0.01 0.01 4.1 1.3 0.1 0.9

85 38.8 5.3 3.6 9.0 3.0 2.0 1.0 0.7 0.3 0.8 0.07 0.03 0.01 4.5 1.7 0.2 0.9

72 33.9 4.7 3.1 6.9 2.3 1.7 0.8 0.7 0.2 0.6 0.05 0.03 0.01 3.9 1.0 0.2 0.5

88 34.1 5.0 2.8 6.6 2.2 1.5 0.7 0.5 0.2 0.6 0.06 0.01 0.01 4.1 0.9 0.1 0.6

82 33.7 4.6 3.3 6.7 2.2 1.8 0.6 0.5 0.2 0.6 0.06 0.02 0.01 4.1 1.5 0.1 0.9

73 37.2 6.6 3.3 5.8 1.9 1.8 0.8 0.9 0.2 0.5 0.05 0.03 0.01 4.8 2.8 0.3 1.0

80 40.0 6.3 3.5 6.8 2.3 1.9 0.9 1.0 0.3 0.6 0.06 0.04 0.01 5.0 1.3 0.4 0.5

89 36.5 5.8 2.9 4.9 1.6 1.6 0.6 0.7 0.2 0.5 0.05 0.02 0.01 4.7 1.1 0.2 0.6

76 35.5 6.2 3.2 5.1 1.7 1.8 0.5 0.6 0.2 0.5 0.05 0.02 0.01 4.2 1.9 0.2 0.8

45 36.3 4.9 2.3 6.4 2.1 1.1 0.7 0.8 0.2 0.4 0.06 0.02 0.01 4.9 1.1 0.2 0.8

102 36.9 5.1 2.3 6.5 2.2 1.2 0.6 0.8 0.2 0.4 0.06 0.02 0.01 4.4 1.7 0.2 0.9

32 20 28 3 2 16

39 15 19 4 2 21

28 16 19 2 1 34

34 17 23 2 1 24

51 14 19 2 2 12

46 14 16 3 2 19

43 15 16 2 2 22

46 14 19 2 1 19

39 18 23 3 2 15

41 16 17 3 2 21

34 16 18 2 1 28

37 17 20 2 1 23

37 13 19 3 2 26

* non-complete years. **Mean PM10 for analyzed days.

37 14 19 3 1 27

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Table 5 Levels of major PM10 components measured at ON, LA, VR and BO-urban (annual means) compared with the usual ranges for regional background, urban background and road traffic and industrial hotspots in Spain reported by Querol et al. (in press)

Crustal Regional background Urban background Road traffic-industrial OM+EC Regional background Urban background Road traffic-industrial SIC Regional background Urban background Road traffic-industrial Sea spray Iberian Peninsula (inland) Iberian Peninsula (coastal) Canary islands

USUAL RANGES

LEVELS MEASURED

2–5 μg/m3 8–12 μg/m3 13–15 μg/m3

8–11 μg/m3 (ON) 15–20, 13–16 and 13–14 μg/m3 (LA, VR and BO-urban)

2–5 μg/m3 5–10 μg/m3 10–18 μg/m3

4–5 μg/m3 (ON) 5, 6–7 and 5 μg/m3 (LA, VR and BO-urban)

5–8 μg/m3 6–11 μg/m3 8–15 μg/m3

5–7 μg/m3 (ON) 5–7, 6–9 and 7 μg/m3 (LA, VR and BO-urban)

1 μg/m3 1–4 μg/m3 10–12 μg/m3

5 and 4–5 μg/m3, respectively). Sea spray (calculated as the addition of Na and Cl) accounts for around 1 μg/ m3 at all sites, representing only 2 to 4% of the bulk PM10 mass. Finally, the addition of all trace metals accounts for only 1 to 2% of the bulk PM10. A comparison of the levels of the above major PM10 components with typical ranges at other similar, but non-industrial, sites in Spain (Querol et al., in press, Table 5) reveals that the annual crustal load in PM10 measured at LA, VR, BO-urban, and ON exceeds by 7–12, 5–8, 5–6, and 6–9 μg/m3, respectively, the typical range of crustal load. In contrast, levels of OM + EC measured in the study area are within the usual range of regional background sites (2–5 μg/m3) and urban background sites (5–10 μg/m3). Likewise, levels

Around 1 μg/m3 (all sites)

of SIC also fall within the usual range of regional background sites (5–8 μg/m3) and urban background sites (6–11 μg/m3). Levels of the analyzed components do not show a marked upward or downward trend along the 4 years of study, nevertheless, crustal annual mean of 2002 at LA and VR is higher than the mean for 2004–2005 (Fig. 7). This could be explained by the implementation of abatement techniques in some ceramic factories that process crustal materials (mainly clays) since summer 2002. Crustal levels do not show a definite seasonal trend (Fig. 7) because they are influenced by the primary emissions from the ceramic industry, by soil dust resuspension and by African dust outbreaks, which results in episodic increases in the crustal components

Fig. 7. Monthly crustal components in PM10 levels (μg/m3) at VR, LA, ON and BO-urban for the study period.

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Fig. 8. Daily levels of crustal components in PM10 for the study period. Not all measurement days are simultaneous at the four monitoring sites.

randomly distributed along the year. At the industrial background site of ON, a large number of these events coincide with African dust outbreaks (MMA, 2002,

2003, 2004, 2005, Fig. 8), whereas at the industrial stations (LA and VR), most of the highest crustal peak events can be attributed to local or regional pollution

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due to the higher oxidation speed of SO2 into SO42 - in summer. This is also supported by the similar seasonal pattern described by monthly levels of Na (Fig. 9), with summer maxima, although Cl− levels do not show the same pattern. This difference can 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 (Querol et al., 2004a). The OM + EC levels are higher in winter than in summer, probably because of the accumulation of pollutants due to the lower dispersive conditions in winter (Rodríguez et al., 2003). This trend is more noticeable at VR and LA due to the higher influence of traffic emissions at these two sites (Fig. 9). At LA, levels of OM + EC clearly decrease during weekends (Fig. 6), reflecting the high influence of heavy traffic during weekdays in this industrialized area. 4.3. Target PM10 levels

Fig. 9. Monthly SO24 -, NO−3 , NH+4, Cl−, Na and OM + EC in PM10 levels (μg/m3) at VR, LA, ON and BO-urban for the study period.

(Fig. 8). The local origin of this component is confirmed by the decrease of crustal levels during weekends (Fig. 6) at LA, VR and BO-urban, probably related to a lower industrial activity and less traffic. On the other hand, sulphate levels vary simultaneously at VR, LA, ON and BO-urban (Fig. 9), with peak levels in summer and minima in winter due to the higher breeze transport of pollutants emitted from the power station located on the coast to LA, VR and ON in summer and

The extra values of crustal component (6–9 μg/m3 at regional sites and 5–12 μg/m3 at urban sites) account for most of the surplus of the bulk mass PM10 levels (7 at ON and around 10 μg/m3 at LA-VR-BO-urban). Given that the concentrations of the rest of components are within the usual ranges at similar sites with no industrial influence, the target component for reducing the bulk PM10 mass is the crustal load. So, knowing the main industrial activity in the area, it can be deduced that to reduce PM10 levels it is necessary to reduce emissions from ceramic activities (including mining and truck transport). Bearing in mind the efficiency of the best available emission abatement techniques applicable to these activities (IPTS, 2001, 2006), a realistic air quality target at medium-term with the current technologies would be a reduction of 3– 5 μg/m3 of the PM10 annual mean at the urban sites (currently recording 33–36 μgPM10/m3). Further reduction would require additional, complex and costly measures. Even if this target is achieved, the requirement on the number of the annual exceedances of the daily limit value will be difficult to meet, since recent studies (European Commission, 2004; Querol et al., 2004a,b) demonstrated that this requirement is equivalent to an annual PM10 limit value of 30 μgPM10/m3, much more restrictive than the current limit of 40 μgPM10/m3. 5. Conclusions PM10 levels measured in the ceramic producing area of Castelló, Spain, decreased in 2003–2005 with respect to previous data obtained at Onda in 1999, meeting the

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requirements of the annual limit value for 2005 according to the 1999/30/CE standard. Summer PM10 peaks and winter minima are evident at our regional background sites ON, AM, and BO-rural due to greater atmospheric mixing in summer favoring transport of pollutants from urban or industrial hotspots towards rural areas. With regard to our urban and industrial sites, whereas higher levels of PM10 would normally be expected in winter, in fact summer levels are held relatively high due to a number of factors such as the low rainfall, inland transport of pollutants by sea breezes, and African dust intrusions. Maximum PM10 levels simultaneously measured during April 2002, March 2003 and February 2004 are attributable to typical anticyclonic scenarios with thermal inversion episodes resulting in the accumulation of regionally emitted pollutants. Peak levels of June and July 2003 are ascribed to frequent African dust air mass intrusions. If exceedances of the daily PM10 limit value for 2005 (50 μg/m3) caused by dust outbreaks are not taken into account, the annual number of exceedances is diminished by 6–17 and the 90.4 percentile values decrease by 2–4 μg/m3 whereas the annual mean value is reduced by only 1 μg/m3. The major constituent of PM10 in the study area is mineral matter (crustal component) which accounts for 28–51% of the mean annual bulk PM10, being higher at LA, VR and BO-urban than at ON; SIC account for 16–28%; OM + EC for 14–20%; sea spray accounts for 2–4%; and the addition of all trace metals accounts for 1 to 2%. Regarding concentrations of individual components there was no clear upward or downward trend over the study period; nevertheless crustal levels of 2002 are higher than those of 2004–2005 at the industrial sites. Crustal components do not show a definite seasonal trend. Sulphate levels vary simultaneously at VR, ON and LA, registering peak levels in summer and low levels in winter as a consequence of the high SO2 summer conversion velocity. OM+ EC levels are higher in winter than in summer, probably because of the accumulation of pollutants due to the lower dispersive conditions in winter. The target component for reducing the bulk PM10 mass is the crustal load, which is recorded in levels higher than the usual ranges at similar sites with no industrial influence. Thus, it is necessary to reduce emissions from the ceramic activities (including mining and truck transport) to reduce PM10 levels. Bearing in mind the efficiency of the best available emission abatement techniques applicable to these activities, a realistic air quality target at medium-term with the current technologies would be a reduction of 3–5 μg/m3 of the PM10 annual mean at the urban sites (currently

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recording 33–36 μgPM10/m3). Nevertheless, to meet the requirement on the number of the annual exceedances of the daily limit value it would be necessary a higher reduction (achieving an annual mean of 30 μgPM10/m3, European Commission, 2004; Querol et al., 2004a,b). PM speciation studies allow the evaluation of the strategies to be followed to diminish PM pollution in highly industrialized areas with a large number of potential pollution sources. Thus, it is based on the comparison with similar non-industrial sites, identifying which component of PM10 is present in concentrations higher than the usual ranges. Afterwards, knowing the main industrial activities in the area and their emission profiles, the main pollution sources that should reduce their emissions can be identified. Then, taking into account the possible abatement technologies available, it is possible to fix reduction targets of PM10. Acknowledgements The present study was supported by the Conselleria de Territori i Habitatge de la Generalitat Valenciana and by the research project CGL2004-05984_C07-02/CLI from the Spanish Ministry of Education and Science. We would like to thank an anonymous reviewer for the valuable comments and suggestions. A grant from the Spanish Ministry of Education and Science was awarded to María Cruz Minguillón. References Alastuey A, Mantilla E, Querol X, RodrÍguez S. Study and evaluation of atmospheric pollution in Spain: necessary measures arising from the EC Directive on PM10 and PM2.5 in the ceramic industry. Bol Soc Esp Cerám Vidr 2000;39(1):141–8. Criado E, Sánchez E, Regueiro M. All tiled up. Spanish ceramics and glass. Ind. Miner. 2004;444:48–55. Directive 1999/30/EC of the European Parliament and of the Council of 22 April 1999 relating to limit values for sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter and lead in ambient air. Directive 2004/107/EC of the European Parliament and of the 15 December 2004 relating to arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in ambient air. Draxler RR, Rolph GD. HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) Model access via NOAA ARL READY Website(http://www.arl.noaa.gov/ready/hysplit4.html), NOAA Air Resources Laboratory, Silver Spring, MD, 2003. Dulac F, Tanré D, Bergametti G, Buat-Ménard P, Desbois M, Sutton D. Assessment of African airborne dust mass over the Western Mediterranean sea using meteosat data. J Geophys Res 1992;97:2489–506. Eatough DJ, Eatough DA, Lewis L, Lewis EA. Fine particulate chemical composition and light extinction at Canyonlands National Park. J Geophys Res 1996;101:19515–31.

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