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Monitoring of PM10 and PM2.5 around primary particulate anthropogenic emission sources
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Atmospheric Environment 35 (2001) 845}858
Monitoring of PM10 and PM2.5 around primary particulate anthropogenic emission sources Xavier Querol *, AndreH s Alastuey , Sergio Rodriguez , Felicia` Plana , Enrique Mantilla, Carmen R. Ruiz Instituto de Ciencias de la Tierra **Jaume Almera++, CSIC, C/Lluis Sole& Sabarn& s, s/n, 08028 Barcelona, Spain Centro de Estudios Ambientales del Mediterra& neo, CEAM. Parque tecnolo& gico, C-4, sector oeste, 46980 Paterna (Valencia), Spain Instituto de Carboqun& mica, CSIC, C/Marn& a de Luna 12, 50015 Zaragoza, Spain Received 29 February 2000; accepted 18 July 2000
Abstract Investigations on the monitoring of ambient air levels of atmospheric particulates were developed around a large source of primary anthropogenic particulate emissions: the industrial ceramic area in the province of CastelloH (Eastern Spain). Although these primary particulate emissions have a coarse grain-size distribution, the atmospheric transport dominated by the breeze circulation accounts for a grain-size segregation, which results in ambient air particles occurring mainly in the 2.5}10 lm range. The chemical composition of the ceramic particulate emissions is very similar to the crustal end-member but the use of high Al, Ti and Fe as tracer elements as well as a peculiar grain-size distribution in the insoluble major phases allow us to identify the ceramic input in the bulk particulate matter. PM2.5 instead of PM10 monitoring may avoid the interference of crustal particles without a major reduction in the secondary anthropogenic load, with the exception of nitrate. However, a methodology based in PM2.5 measurement alone is not adequate for monitoring the impact of primary particulate emissions (such as ceramic emissions) on air quality, since the major ambient air particles derived from these emissions are mainly in the range of 2.5}10 lm. Consequently, in areas characterised by major secondary particulate emissions, PM2.5 monitoring should detect anthropogenic particulate pollutants without crustal particulate interference, whereas PM10 measurements should be used in areas with major primary anthropogenic particulate emissions. 2001 Elsevier Science Ltd. All rights reserved. Keywords: Atmospheric particles; PM10; PM2.5; Ceramic emissions; Ambient air quality monitoring; Primary particles; Mediterranean basin
1. Introduction Atmospheric particulates, especially secondary anthropogenic "ne particles, have been proven to have a major impact on human health (Dockery and Pope, 1996). For many years, the atmospheric particulate standards of many countries were based on the mass concentration measurement of the total suspended particles
* Corresponding author. Tel.: #34-93-4095410; fax: #3493-4110012. E-mail address: [email protected] (X. Querol).
(TSP). Since an important mass fraction of TSP is made of non-inhalable particles with a lower impact on respiratory and cardiovascular diseases, the relationship between health e!ects and TSP levels was found to be much lower than the levels of atmospheric particulates "ner than 10, 2.5 or 1 lm (PM10, PM2.5 and PM1, respectively), on comparison. This was the reason for the application of PM10 and PM2.5 measurements to the US ambient air quality standards (US-EPA, 1987 for PM10; US-EPA, 1996 for PM2.5). Although a decade later, the European Union (EU) countries have followed the same trend of replacing ambient air standards based on TSP by PM10 standards. Currently, the incorporation of ambient air standards based on PM2.5 is also
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being considered in the EU (EU Directive 1999/30/EC, 1999) Another important pattern of atmospheric particulates, which is still not considered in ambient air standards, is the chemical composition of TSP, PM10, PM2.5 and PM1. Major secondary acidic aerosols and hazardous organic particulates are "ne-grained. Generally, inorganic secondary aerosols are in the (0.5 lm (sulphate and nitrate) and 0.5}5.0 lm (a fraction of nitrate) size range (Mildford and Davidson, 1987), marine aerosol salts have a major fraction in the range of 1.0}5.0 lm, whereas, primary natural particles, mainly made of Al}Si minerals (clay minerals, quartz, feldspars) and calcium and magnesium carbonates, have a major proportion in the 5}25 lm range. The carbon contents of atmospheric particulates have a bimodal grain-size distribution with a mode in the (2.5 lm (corresponding to anthropogenic organic particles) and '10 lm (corresponding to mineral carbonates). Primary anthropogenic particulate emissions are also usually in the '2.5 lm range. At a global scale, the anthropogenic emissions do not exceed the 10% of the global particulate emissions, whereas the natural primary emissions reach the 84% (2.9;10 t yr\, after Kiehl and Rhode, 1995; IPCC, 1996). Concerning the global anthropogenic particulate emissions, the secondary aerosols exceed the primary particulate emissions (0.26;10 and 0.11;10 t yr\). Consequently, the global emissions of natural particulates are mainly primary, whereas, the anthropogenic emissions are predominantly secondary. Future trends for particulate monitoring strategies tend to monitor PM2.5 rather than PM10 because of its more direct relationship with health e!ects and to avoid natural particulate interference. However, industrial activities with high primary particulate emissions, such as cement, concrete, ceramics or the mining sectors, may have a great impact on the ambient air quality due to their intensive particulate emissions in the 2.5}10 lm range. Moreover, these emissions usually have a chemical composition similar to that of natural crustal emissions (high Ca, Al, Si, Fe, K proportions), which impedes the appropriate monitoring of ambient air particulate levels. This paper introduces the results obtained from a research project supported by the Spanish Ministry of the Environment and the CICYT (ComisioH n Interministerial de Ciencia y TecnologmH a) to develop source apportionment analyses of PM10 and PM2.5 focussed on the speci"c atmospheric and geographical characteristics of Spain. The present study focuses on the evaluation of the physico-chemical patterns of ambient air particulate matter in ceramic industrial zones. In these areas, although high levels of secondary particulates may be emitted, the largest source contribution in high particulate events is due to primary emissions of mineral matter from atomiser plants and fugitive emissions from piling stock. Continuous grain-size analysis of TSP from
di!erent sources and simultaneous PM2.5 and PM10 sampling and analysis were carried out to de"ne the best parameter for monitoring the impact of ceramic industrial emissions on ambient air quality.
2. The study area The ceramic industrial areas of L'Alcora, Onda and Vilareal spread along the Millars river basin from the coast to the interior of the CastelloH Province in Eastern Spain (Fig. 1). The CastelloH industrial area is the second largest ceramic-producing zone in the world, accounting for 17% of the world's basic ceramic production (600;10 m yr\). The supply of clays for the industry comes mainly from an open-pit mine at a Triassic red kaolinite-rich clay deposit in Sant Joan de MoroH (east of the city of L'Alcora, Fig. 1) and from the Cretaceous kaolinite-rich deposits in the province of Teruel. In a minor proportion, a large variety of other natural and synthetic products, such as feldspars, melting phases and
Fig. 1. Location of major ceramic production areas and "xed sampling stations for PM10/PM2.5 measurements.
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colourants, are also broadly consumed. The kaoliniterich material is "nely ground in the atomisers, which produces a homogeneous "ne powder ((63 lm). This process coupled with the large clay consumption (20;10 t in 1998) and the large fugitive emissions from the storage, handling and transport of the clay, probably accounts for the largest fraction of the local anthropogenic particulate emissions. Secondary particulate emissions from the manufacturing of glass and enamel may account more for the emission of hazardous atmospheric trace pollutants than for their signi"cant contribution to the bulk particulate emissions. Other particulate emission sources such as intensive road transport, frequent biomass combustion from intensive orange tree cropping, and marine aerosols, must also be considered. This puzzling particulate-emission setting is placed in a complex Mediterranean atmospheric environment. The intensive convective dynamics, the breeze circulation, the low rainfall rate, the highly mineralised soils and the frequent occurrence of high particulate Sahara air-mass intrusions further complicate the monitoring of the anthropogenic particulate emissions impact on ambient air quality. The study was made in July because of the large impact of some of the previously mentioned atmospheric environmental factors on the particulate levels. In summer, the North Atlantic anticyclone becomes reinforced over the northern latitudes. Weak-gradient conditions on the Iberian Peninsula and strong ground heating give rise to the development of the Iberian thermal low (ITL), due to thermally induced local and mesoscale circulations, such as sea breeze, up-slope winds and convective cells (MillaH n et al., 1991). The study area (Fig. 1) includes the CastelloH alluvial plain (La Plana) which is limited on the north by the Palmes mountain chain (6}7 km from the coast) and includes Mt. Bartolo as its highest peak (780 m.a.s.l.). The Millars basin, with an approximate E}W direction, converges with the "rst range of mountains at 20 km from the coast. The movement of the air masses over the eastern Coast of the Iberian Peninsula as well as the evolution of the boundary layer are strongly linked to its complex topography. During the daytime the sea breeze is channelled
847
along the bottom of the valleys up to 60}80 km inland, whereas at the top of the mountains and valley slopes a combination of sea breeze and up-slope winds gives rise to a chimney e!ect, injecting air from low levels to altitudes ranging from a few hundred meters up to 2}3 km. The anticyclonic subsidence and the dynamics formation of the sea breeze cells favour the formation of reservoir layers of secondary pollutants (thermally separated between themselves by inversions) in the return #ow moving toward the Mediterranean Sea. A compensatory sinking over the sea, due to thermal buoyancy over the warmed terrain and anticyclonic subsidence, reinforces the sea-breeze circulation and prepares the reservoir layers over the sea for re-entrance a few days later. During the evening and night, the solar-activated circulations cease, and a reversal in the breeze takes place. Thus, the sea-breeze circulation in summer favours good ventilation conditions in the valleys but scarce air-mass renovation, due to the above-described re-circulations of the air masses (MillaH n et al., 1997), resulting in a potential atmospheric reservoir e!ect for secondary air pollutants in the Western Mediterranean.
3. Methodology 3.1. Sampling sites The following sampling and measurement sites (Fig. 1 and Table 1) were selected based on the distribution of the major emission sources (marine, rural, urban and industrial sites) and on the atmospheric-circulation peculiarities of the study area: The Grau station is located in a rural or semi-urban area, which is sporadically in#uenced by the industrial and urban plumes, especially the plume from CastelloH in night-breeze conditions. The station of the Villareal city is an urban site in the lower watercourse of the Millars, situated 10 km from the coastline, in the centre of a zone of a large ceramicindustrial activity. This station is under the in#uence of both urban (mainly tra$c) and industrial emissions. During the daytime period this location is situated leeward of the city and the ceramic emissions with respect to the
Table 1 Location of the "xed monitoring and sampling stations Sampling site
Location
Latitude
Longitude
Mt. Bartolo Onda Vilareal Grau L'Alcora
Telecom antenna peak Monitoring station (urban background station) Post o$ce (urban background station) Monitoring station (urban background station) Council house (urban background station)
40305 09 N 39357 43 N 39356 34 N 39358 59 N 40305 09 N
00301 53 W 00315 43 W 00306 25 W 00300 31 W 00301 53 W
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characteristic breeze #ow. For this reason, the contributions due to tra$c emissions should be equal or more important than the industrial emissions. On the other hand, the in#uence of the ceramic emissions are expected to predominate during the nocturnal breeze period. The Onda station is a suburban background station near the city of Onda, situated in an open area, 20 km from the coastline, without direct in#uence from urban or road tra$c activities. It is situated on the leeward of the nearby ceramic industries, and in sea-breeze conditions it is also in#uenced by the coastal industrial emissions. The L+Alcora station is located in an urban background site in the municipality of L'Alcora, in the most productive ceramic zone of CastelloH . In the daytime the breeze drags the atmospheric emissions with a northwestern transport, whereas in the nocturnal breeze phase the previously emitted particulates travel seawards towards L'Alcora. Finally, the Mt. Bartolo station is located at the top of the Mt. Bartolo peak. Possible anthropogenic emissions could come from a nearby residential area and from various roadways concentrated on the coastal fringe. The objective of using this emplacement was to provide a vertical gradient for discriminating possible high-altitude contributions not present at lower levels. Lastly, meteorological data from the air quality network cabins of Ermita and Penyeta and the meteorological towers of Cirat, Rambla of the Viuda and Borriana were also used to carry out the interpretations. 3.2. Sampling and measurements
Fig. 2. Correlation of PM10 and PM2.5 measurements between the GRIMM laser spectrometer and the high-volume sampler. Solid lines indicate 1:1, dashed line is the correlation line. In PM10, correlation was performed at the following sites: (1) Solid circles, suburban Onda station; (2) Solid triangles, rural Monagrega station; (3) Triangles, urban Barcelona station; (4) Squares, urban L'Hospitalet station. PM2.5 correlation was performed at Onda (2 samples) and L'Hospitalet.
The sampling of atmospheric particulate matter was carried out by means of high-volume samplers (DH-80 and MCV-CAF, 30 m h\) equipped with PM10 and PM2.5 DIGITEL and MCV cut-o! inlets and quartz glass "lters (QF20 Schleicher and Schuell). Daily sampling was made from 12 to 23 July 1999 at the "ve "xed monitoring stations (Table 1). Furthermore, sampling of TSP grain-size fractions (seven stages from 0.3 to '20 lm) was performed for 4 days (from 11 to 23 July 1999) at the Onda station by means of a Retsch PI-1 cascade impactor. Once the levels of bulk particulates were obtained by weighting the "lters using standard procedures, one-half of each of them (PM10 and PM2.5) plus the insoluble fractions of the di!erent stages of the cascade impactor (previously "ltered with MQ cellulose membrane "lters) and blank "lters were digested following the method of Querol et al. (1998). The soluble fraction of 1/4 of each "lter and the di!erent grain-size stages obtained with the cascade impactor were extracted with distilled water at 803C. The last 1/4 of each "lter was used to directly determine the total C content by LECO methodology.
The solutions obtained were analysed by: (a) inductively coupled plasma-atomic emission spectrometry (ICP-AES) for major elements, (b) capillary electrophoresis (CEF) for anions, and (c) colorimetry-#ow injection analysis (FIA) for NH>. The digestion of blank "lters with 2}3 mg of NBS-1633a reference material was used to ensure analysis quality for the same levels of the sample digestion concentrations. Relative analytical errors were between 3 and 10% for the elements studied. Automatic measurements of atmospheric particulate levels and grain-size distribution were performed with the laser spectrometer dust monitor GRIMM 1108 (Labortechnik GmbH & Co. KG) at the "xed and mobile stations. This dust monitor permits the determination of particulate levels in 15 di!erent grain-size channels from 0.3 to '20 lm. The accuracy of the GRIMM-1108 measurements was checked, before, during and after the "eld campaigns, by comparing the levels of simultaneous daily PM10 and PM2.5 measurements obtained with the standard gravimetric methodology. Fig. 2 shows good agreement between the PM10 measurements obtained
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Table 2 Location of mobile station for grain-size analysis of TSP with the GRIMM laser spectrometer around the major emission sources (E) and ambient air measurements (A) No.
Measurement description
Longitude
Latitude
E-1 E-2 E-3 E-4 E-4b E-5 E-6 E-7 E-8 E-9 E-10 E-11 E-12 E-12b E-13 E-14 E-15 E-16 E-17 E-18 E-19 E-20 E-20b A-1 A-2 A-3 A-4 A-5 A-6 A-7 A-8 A-9
Fugitive emissions from a clay mine Fugitive emissions from clay transport at L'Alcora Atomiser, Onda Atomiser L'Alcora Atomiser L'Alcora second measurement Around stack emissions PA factory Around stack emissions SA factory Around stack emissions VE factory Around stack emissions JM factory Around stack emissions JM factory second measure Around stack emissions EG factory Around stack emissions NA factory Around stack emissions POR factory Emission plume measurement POR factory Emission plume measurement PA factory Dense tra$c crossroad at CastelloH Dense tra$c crossroad at CastelloH Emission plume from petrochemical plant Biomass "ring around orange tree plantations Marine aerosols Borriana harbour (Morro) Marine aerosols Millars delta Marine aerosols Ben Afali beach Marine aerosols Ben Afali beach on the shoreline Northern background levels around the ceramic zone Middle background levels in orange plantations Coastal background levels leeward of ceramic emissions Urban background levels L'Alcora Semi-urban background levels L'Alcora (St. Salvador) Urban background levels L'Alcora Semi-urban background levels L'Alcora}Onda Semi-urban background levels Millars bridge Rural-remote background levels Mt. Bartolo
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
40 40 39 40 40 39 40 39 39 39 39 39 40 40 39 39 39 39 39 39 39 39 39 39 39 39 40 40 40 39 39 40
with the high-volume sampler and the GRIMM-1108 laser spectrometer. Although good agreement was also obtained in the two simultaneous PM2.5 measurements during the "eld campaign, a longer inter-comparison demonstrated that the GRIMM 1108 measurements were 15% lower than those obtained by the gravimetric method (Fig. 2). The measurements of particulate-matter levels and grain-size distribution with the laser spectrometer were carried out in the vicinities of the following emission sources (Table 2 and Fig. 3): 1. Di!erent types of ceramic emission plumes including those from enamel (white to yellow plumes) and tile (reddish plumes) factories and atomiser centres. Fugitive emissions were measured at a certain distance of a number of sources including the stockpiles in the atomiser centres, the largest open-pit mine in the area,
2.
3.
4.
5.
06 10 14 10 10 04 09 14 04 04 09 13 05 05 04 02 03 01 01 04 00 00 00 16 09 04 11 11 12 10 07 01
31 08 35 29 29 50 11 49 21 20 35 07 38 38 41 14 19 06 03 13 49 15 15 10 44 03 20 49 30 46 11 53
W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W
04 03 58 03 03 57 02 58 57 57 56 57 01 01 57 59 58 57 59 51 54 55 55 59 59 54 04 05 04 59 57 05
39 00 18 29 29 38 36 11 51 56 41 41 21 21 22 22 19 06 36 32 22 20 20 10 09 45 02 11 10 29 54 09
N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N
and a crossroad where high emissions from the short road transport between the clay-mining area and the tiling and atomising centres were evident. The tra$c emissions in the vicinity of a crossroad with high tra$c density (mainly cars) at two di!erent sites inside the city of CastelloH . The marine aerosol at three di!erent coastal sites (a few metres from the shoreline) in the in-land breeze circulation stage. The biomass combustion emissions were measured at di!erent distances from the "res in extensive orangetree plantations located upwind from the ceramic emissions in the Grau area. The emission plume from the petrochemical plant was detected with the help of the SO analysers in a COS PEC unit and, subsequently, grain-size measurements were obtained without interference of the ceramic emissions in the in-land breeze stage.
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4.1. PM10 and PM2.5 levels
Fig. 3. Location of mobile measurement stations for grain-size analysis of TSP with the GRIMM laser spectrometer around the major emission sources (E) and ambient air measurements (A). See detailed data of location in Table 2.
In addition to the emission measurements, short (1}2 h) measurements were performed in background areas up- and down-wind of the emission plumes from the ceramic zones (Table 2 and Fig. 3). The measurements were performed in the in-land breeze stage following a cross-section from the shoreline (backwards to the petrochemical and ceramic emissions), downwind of the petrochemical emission and "nally downwind of the ceramic emission plumes. Short measurements were also carried out at di!erent background sites in#uenced by di!erent ceramic emission sources. Longer measurements (24 h) were carried out at the Grau, L'Alcora and Onda stations to study the grain size range of atmospheric particulates in#uenced by the ceramic emissions transported by the breeze circulation.
4. Results and discussions During the measurement campaign typical summer meteorological conditions predominated with a localcirculation dominance in the measuring zone, in spite of the fact that a smooth perturbation aloft took place at the end of the "rst week. Thus, the scenario consisting of a daytime inland and a nocturnal seaward #ow was repeated daily in the Millars Valley during the measurement campaign. The typical summer thermal vertical structure with subsidence inversions was also observed.
As expected, the lowest PM10 mean values were obtained at the Mt. Bartolo background station (18 lg m\). The highest PM10 values were registered at the L'Alcora and Vilareal stations (56 and 44 lg m\, respectively) which are located in the most productive ceramic areas. The Grau and Onda stations, located in rural or suburban areas, which are temporarily in#uenced by the emission plumes, have intermediate PM10 values of approx. 30 lg m\. The mean PM2.5 fraction of PM10 in the study area was approx. 50%wt, whereas the mean PM10 fraction of total suspended particles (TSP) was found to be approx. 65%, with extreme mean daily values from 50 to 80 wt%. The levels of marine aerosols were homogeneously distributed in the study area as deduced from the narrow variations in the concentrations of Na>, Cl\ and Mg> observed among the di!erent sampling sites (Table 3). A similar homogeneous pattern was observed for levels of sulphate and ammonium (Table 3). The background, the suburban and the industrial stations showed mean levels ranging only from 7 to 9 lg m\ for anthropogenic sulphate and 2.1}2.8 lg m\ for ammonium. The ionic balance between ammonium and sulphate demonstrates that around 80% of the anthropogenic sulphate is present as ammonium sulphate. The occurrence of ammonium sulphate, sodium chloride and magnesium probably in discrete background aerosols probably accounts for the homogeneous levels of these phases in PM10 across the study area. Conversely, the nitrate levels were considerably higher at the Vilareal site (with the highest tra$c density) and lower, by a factor of 4}5, at the rural background site of Mt. Bartolo (Table 3). A similar pattern was also observed for the distribution of levels of organic carbon and phosphor. The other stations registered intermediate values for nitrate and organic carbon with the exception of the suburban Grau station. The frequent uncontrolled biomass combustion from intensive orange tree cropping around this station probably accounted for the high levels of organic carbon, phosphor and nitrate, similar to those recorded at the heavily polluted Vilareal site. The levels of the major elements emitted by the ceramic industry (clay-related elements such as Si, Al, Fe, K and Ti) were one order-of-magnitude higher at the L'Alcora and Vilareal stations than at the Bartolo site, with the Onda and Grau stations having intermediate levels (Table 3). Levels of Ca and Mg, mainly from soil emissions with a low proportion from the ceramic industry, also increased in the ceramic zone with respect to the background site but in a lower rate than the ceramicrelated elements. On an average, the addition of all the constituents determined reached 90% of the bulk PM10 or PM2.5
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Table 3 Mean daily major elements, carbonates, ammonium, organic#elemental carbon and bulk PM10 levels obtained at Mt. Bartolo, Grau, Onda, Vilareal and L'Alcora sampling sites Location
Bartolo
Grau
N
5
9
CO\(lg m\) Org#Elem C (lg m\) SiO (lg m\) Al O (lg m\) Ca (lg m\) K (lg m\) Mg (lg m\) Fe (lg m\) NO\ (lg m\) NH> (lg m\) SO\ no marine (lg m\) SO\ marine (lg m\) Na (lg m\) Cl\ (lg m\)
0.7 2.9 1.1 0.4 0.5 0.2 0.2 0.2 0.9 1.9 7.0 0.2 0.8 0.2
2.0 6.1 2.7 1.1 1.3 0.5 0.3 0.4 2.9 2.5 8.4 0.3 1.2 0.8
Onda 11 1.6 3.9 3.6 1.4 1.0 0.5 0.2 0.4 1.8 2.3 8.7 0.2 1.0 0.4
Vilareal 9 3.5 6.8 6.0 2.4 2.3 0.8 0.4 0.7 3.5 2.1 9.0 0.4 1.4 0.9
L'Alcora 2 4.3 5.5 12.0 4.8 2.9 1.5 0.4 1.2 1.8 1.9 8.4 0.2 0.9 0.5
R major elements (lg m\) PM10 gravimetry (lg m\) Determined (%)
17 19 91
31 36 85
27 32 85
41 44 94
48 56 86
Crustal (%) Secondary (%) Org#Elem C (%) Marine A (%)
19 57 17 7
27 45 20 8
33 47 14 6
40 37 17 7
58 27 12 4
N, number of daily samples. The results of the source apportionment analysis including crustal sources, secondary particulates (ammonium sulphate and nitrate), organic#elemental carbon, and marine aerosols are also reported as the percentage of contribution of each source with respect to the bulk PM10 levels.
levels obtained by the gravimetric method. The results indicate that the mean marine aerosol input represents between 4 (L'Alcora) and 8 (Grau) wt% of the bulk PM10 levels (Table 3). The proportion of organic and elemental carbon, mainly proceeding from combustion processes, is relatively homogeneously distributed across the study area with values from 12 to 20% wt of bulk PM10, with the highest values being recorded for the Grau and Vilareal sites (Table 3). The PM10 proportion from the crustal input (both soil and ceramic emissions) ranged from 18% of bulk PM10 at the Bartolo site, up to 40}55 wt% in the ceramic productive area. The Onda and Grau sites have intermediate proportions (around 30 wt%). Finally, the proportion of secondary inorganic aerosols (ammonium, sulphate and nitrate) is very high at the background site (near by 60% of bulk PM10 levels) and the Onda and Grau sites (45}50 wt%), whereas in the ceramic zone (Vilareal and L'Alcora) it is much lower (approx. 30 wt%), the background origin of ammonium sulphate in the study area. Thus, in the rural background site, these external phases account for most of the particulate fraction, whereas this proportion is drastically
reduced in the ceramic zone, where local input predominates. Levels of Pb and Zn also reached high values in the ceramic zone (around 0.4 lg m\) but very low levels at the rural background site (0.05 lg m\, Table 4). Although the levels of the other elements were relatively low, with the exception of As (up to 25 ng m\) and Cr (up to 7 ng m\) at L'Alcora and Vilareal, the spatial variation of levels of As, Cr, Cs, Pb, Rb, Sr, Ti, V, Zn and Zr suggests a chie#y ceramic origin for these elements (Table 4). However, Ba, Cd, Co, Cu, Ga, Hf, Mn, Mo, Nb, Ni, Sb, Sc, Sn, Th, U and Y do not show any relationship with ceramic emissions (Table 4). The last conclusion demonstrates that the well-known relationship between some ceramic activities and the high levels of Hf, U and Th in atmospheric particles has a very local incidence. Analysis of simultaneous samples of PM10 and PM2.5 has evidenced that the crustal and marine loads are strongly reduced in the PM2.5 with respect to the PM10 (Table 5) measurements. In contrast, most of the secondary anthropogenic phases are trapped by the PM2.5 sampling, with the exception of nitrate which registers
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Table 4 Mean daily trace element levels in PM10 obtained at Mt. Bartolo, Grau, Onda, Vilareal and L'Alcora sampling sites (N, number of daily samples)
Table 5 Comparison between levels of major and trace elements, carbonates, ammonium, organic#elemental carbon in PM10 and PM2.5, simultaneously sampled at Onda
Location
Onda
N As (ng m\) Ba (ng m\) Cd (ng m\) Co (ng m\) Cr (ng m\) Cs (ng m\) Cu (ng m\) Ga (ng m\) Hf (ng m\) Mn (ng m\) Mo (ng m\) Nb (ng m\) Ni (ng m\) P (ng m\) Pb (ng m\) Rb (ng m\) Sb (ng m\) Sc (ng m\) Sn (ng m\) Sr (ng m\) Th (ng m\) Ti (ng m\) U (ng m\) V (ng m\) Y (ng m\) Zn (ng m\) Zr (ng m\) La (ng m\) Ce (ng m\) Tb (ng m\) Tm (ng m\) Yb (ng m\)
Bartolo
Grau
Onda
Vilareal
5
9
11
9
2
1 1 0.1 0.4 0.6 0.1 77 0.1 0.2 5 0.6 0.1 5 15 45 1 1 0.1 1 2 0.7 12 (0.1 8 0.1 54 3 0.2 0.2 0.03 0.03 0.02
5 11 0.7 0.3 1.7 0.3 36 0.1 0.4 7 0.6 0.1 3 50 199 1 2 0.1 2 4 0.6 29 0.2 7 0.2 132 8 0.3 0.7 0.03 0.03 0.04
11 16 0.6 0.6 3.6 0.5 39 0.2 0.5 11 2.9 0.2 7 52 346 3 2 0.2 2 6 0.9 65 (0.1 10 0.3 264 12 0.6 1.3 0.03 0.03 0.04
25 21 0.9 1.1 6.9 1.2 88 0.5 0.4 13 2.2 0.3 9 42 341 6 2 0.3 2 10 0.2 111 (0.1 14 0.4 699 21 1.1 2.2 0.03 0.02 0.06
8 6 0.4 0.6 2.2 0.4 6 0.2 0.4 7 0.8 0.1 4 32 285 2 1 0.1 1 4 0.2 34 0.6 7 0.1 178 11 0.4 0.9 0.03 0.02 0.05
L'Alcora
only 40% of the PM10 nitrate levels. As it will be demonstrated later, the occurrence of calcium and sodium nitrate in the 2.5}5.0 lm range probably accounts for the lower nitrate measurements in the PM2.5 "lters. 4.2. Cascade impactor Ammonium and ammonium}calcium sulphates are mainly concentrated in the "nest fractions (0.3}0.7 and 0.7}1.0 lm, respectively). These two "ne fractions account for 80% of the bulk anthropogenic sulphate (Fig. 4). The coarser sulphate is mostly present as calcium and sodium sulphates. The marine aerosol phases are mainly concentrated in the 3}10 lm fraction as inferred from the Na> distribution (Fig. 4). However, there is a clear grain-size segregation between the occurrence of NaCl (6}10 and '10 lm fractions) and the NaNO ((6 lm fraction). This is due to the well-known Na>}NO\}Cl\}NH> interaction (Harrison and Pio, 1983; Wall et al., 1988). Ammonium
CO\ (lg m\) Org#Elem C (lg m\) SiO (lg m\) Al O (lg m\) Ca (lg m\) K (lg m\) Mg (lg m\) Fe (lg m\) NO\ (lg m\) NH> (lg m\) SO\ no marine (lg m\) SO\ marine (lg m\) Na (lg m\) Cl\ (lg m\)
21}22/07/1999
22}23/07/1999
PM10
PM2.5
PM10
PM2.5
4.6 2.1 5.1 2.0 1.4 0.6 0.3 0.5 1.3 1.9 6.8 0.2 0.8 0.3
4.4 1.2 2.3 1.2 0.8 0.5 0.1 0.3 0.5 1.8 6.1 0.1 0.3 0.2
5.7 2.2 4.9 2.1 1.4 0.7 0.3 0.6 1.4 2.1 7.1 0.2 0.8 0.5
4.6 0.4 0.7 0.5 0.2 0.4 0.1 0.2 0.4 2.0 6.7 0.1 0.2 0.2
R major elements (lg m\) PM10/2.5 gravimetry (lg m\) Determined (%)
28 33 87
20 23 90
31 37 84
17 17 100
Crustal (%) Secondary (%) Org C (%) Marine A (%)
43 36 16 5
33 42 22 3
41 35 19 5
16 54 27 3
10 8 0.6 0.5 2.0 0.5 10 0.3 7 0.3 0.2 3 33 354 3 1 1 5 (0.1 48 (0.1 6 197 8
10 3 0.5 0.2 1.5 0.4 9 0.1 5 0.2 0.1 3 22 330 2 1 1 2 (0.1 28 (0.1 5 186 4
10 9 0.6 0.5 2.1 0.5 10 0.1 8 (0.1 0.2 3 32 368 3 1 1 6 0.5 51 (0.1 7 204 8
7 2 0.4 0.1 1.0 0.3 10 0.3 3 (0.1 0.1 3 12 245 1 1 1 1 (0.1 14 (0.1 7 170 5
As (ng m) Ba (ng m) Cd (ng m) Co (ng m) Cr (ng m) Cs (ng m) Cu (ng m) Hf (ng m) Mn (ng m) Mo (ng m) Nb (ng m) Ni (ng m) P (ng m) Pb (ng m) Rb (ng m) Sb (ng m) Sn (ng m) Sr (ng m) Th (ng m) Ti (ng m) U (ng m) V (ng m) Zn (ng m) Zr (ng m)
The results of the source apportionment analysis including crustal sources, secondary particulates (ammonium sulphate and nitrate), organic#elemental carbon, and marine aerosols are also reported as the percentage of contribution of each source with respect to the bulk PM10/2.5 levels.
nitrate (originally present in the (6 lm fraction) reacts with sodium chloride to give rise to ammonium chloride (gas) and sodium nitrate. The ionic balance also indicates the occurrence of Ca(NO ) in the '6 lm
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Fig. 4. Grain-size distribution of weekly levels of the soluble fraction of major species (neq m\) and selected trace metals (ng m\) in total suspended particles obtained at Onda from 12 to 23 July 1999.
fraction probably due to nitri"cation of soil particles (Harrison and Kito, 1990) and NH NO in the (1.5 lm fraction (Fig. 4). As expected, SO\, NO\, Cl\, NH>, Ca, Mg, Mn, Pb, V and Zn have a major soluble fraction (Fig. 4), and Al, K, Sr, Ba, Cr, Cu, Ni, Ti and Fe are mainly present in insoluble phases (Fig. 5). Insoluble soil and ceramic particulates such as clay minerals, calcium carbonate and feldspars (crustal phases) showed a bi-modal grain-size distribution with modes occurring in the 1.5}6.0 and '25 lm fractions as deduced from the grain-size distribution of insoluble levels of Ca, Al, K and Fe (Fig. 5). Soluble fractions of Mn, Fe, V and Cr, probably occurring in di!erent oxide phases with an anthropogenic origin, are mostly in the 6}10 lm range (Figs. 4 and 5). However, Pb and Zn mainly occur in the soluble very "ne grain-size fraction, '85% of bulk Pb levels occurring in the PM2.5 fraction (Fig. 4).
853
Fig. 5. Comparison of the grain-size distributions of weekly levels of the insoluble fraction of major elements and selected trace metals in total suspended particles obtained at Onda in this study with that of a typical urban distribution obtained in Barcelona. Levels in ng m\.
Unusually high proportions of insoluble levels of Al, Ca, Na, Sr, S, P and Fe were found in the "ne grain-size modes ((1.5 lm) when compared with a normal urban or industrial grain-size distribution (Fig. 5). This atypical occurrence of "ne grain sizes for these elements and the unusually high proportion of insoluble Na levels (up to 30% of bulk Na) are probably the result of the condensation of volatile emissions from high temperature processes developed in the enamel manufacture. These peculiar patterns may be a good tool for tracing the input of ceramic emissions on bulk PM10 levels, since the bulk chemical patterns, characterised by high Al, Si, Fe and Ca levels, are similar to the soil end-member. 4.3. Grain-size distribution of atmospheric particulates around the emission sources The fugitive emissions from the largest open-pit clay mine in the area induced very high ambient air PM10
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Table 6 Mean daily major elements, carbonates, ammonium, organic#elemental carbon and bulk PM10 levels obtained at Mt. Bartolo, Grau, Onda, Vilareal and L'Alcora sampling sites. N, number of daily samples . Levels in lg m\
Ceramic emissions Fugitive emissions Clay mine E-1 Transport E-2 Atomiser-ATESA E-3 Atomiser-L'A E-4 Atomiser-L'A2 E-4b Around stack emissions PA E-5 SA E-6 VE E-7 JM E-8 JM-2 E-9 EG E-10 NA E-11 POR E-12 Direct measurements of plume emissions POR E-12b PA E-13
TSP
PM10
PM7.5
PM5
PM2.5
823 1770 387 420 532
PM1.0
PM0.8
337 704 113 128 214
266 560 97 108 187
163 340 75 78 137
61 185 43 40 74
9 21 11 10 16
7 15 9 8 12
349 127 353 78 83 135 267 483
251 56 170 38 44 64 84 218
223 49 158 35 40 59 75 188
159 38 157 30 38 49 68 142
83 22 150 24 35 33 57 84
21 6 126 12 24 12 22 21
16 5 120 11 23 10 17 16
855 2485
385 1018
330 867
247 610
144 289
33 47
25 34
Tra$c emissions CastelloH -1 CastelloH -2
E-14 E-15
62 47
42 27
35 26
26 23
17 19
8 9
7 8
Combustion emissions Petrochemical Biomass
E-16 E-17
25 149
22 73
21 58
19 43
15 28
7 13
6 12
Marine aerosols Borriana Millars Ben Afeli-1 Ben Afeli-2
E-18 E-19 E-20 E-20b
36 53 86 31
31 44 49 28
29 42 43 27
24 33 35 25
17 20 24 19
7 7 8 7
6 6 7 6
Ambient air measurements at background sites Cross-section North-ceramic A-1 55 Middle A-2 39 Coastal A-3 28
35 24 24
32 23 23
28 22 21
22 21 17
12 11 9
12 10 8
L'Alcora-1 L'Alcora-2 L'Alcora-3 L'Alcora}Onda Millars bridge Mt. Bartolo
46 41 43 24 43 25
42 36 37 22 40 24
33 29 27 18 34 21
22 20 16 15 27 16
8 9 7 8 14 8
8 8 6 7 13 7
A-4 A-5 A-6 A-7 A-8 A-9
91 62 66 33 62 32
The results of the source apportionment analysis including crustal sources, secondary particulates (ammonium sulphate and nitrate), anthropogenic organic#elemental carbon, and marine aerosols are also reported as the percentage of contribution of each source with respect to the bulk PM10 levels.
levels around the mining area (approx. 300 lg m\ were recorded on an hourly basis, Table 6 and Fig. 6), but the PM2.5 fraction was relatively low (22 wt% of the PM10). The PM10 fraction also represented a low TSP fraction
(40 wt%). As expected, this coarse grain-size distribution (high and low modes of '20 and 4}15 lm, respectively) was similar to that previously described for the clayrelated elements (Al, K, Fe) obtained from the cascade
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Fig. 6. Selected cases of grain-size distribution of hourly levels of total suspended particles measured in the vicinities of the major ceramic emission sources. Levels in lg m\. See codes in Table 6 and Fig. 3 for location of measurement sites.
impactor measurements. The grain-size distribution of ambient air particulates around di!erent clay atomisers and from several crossroads with high densities of clay road-based transport was also very similar (Fig. 6 and Table 6), with a major proportion in the '20 lm and two secondary modes occurring in the 4}7.5 and 10}15 lm fractions. The PM10 levels around these sites also reached very high levels (from 120 to 700 lg m\ on an hourly basis). The percentages of PM10 over TSP and PM2.5 over PM10 were constantly low (from 30 to 45 wt% and from 40 to 45 wt%, respectively) around the four atomisers. Although the TSP grain size pattern was slightly "ner around the atomisers when compared with the fugitive emissions from clay mining and transport, the similarity of these grain-size distributions suggests that the major emission source from these activities is the fugitive emissions from the large clay stockpiles and transport. PM10 levels around 10 ceramic factories including tiling and enamel factories were signi"cantly lower than around the mining, atomiser and clay-transport sources (Table 6 and Fig. 6). Levels ranging from 40 to 250 lg m\ of PM10 on an hourly basis were obtained around these ceramic factories which emit particulate matter mainly through small-stacks. The percentage of PM10 over TSP and PM2.5 over PM10 increased considerably with respect to the previous emission sources. Although a similar percentages of PM10 over TSP was determined for both tiling and enamel factories (from 50 to 65 wt%), the enamel sources were characterised by a higher proportion of "ne particles (from 80 to 95 wt% of PM10 were in the PM2.5 range) with respect to the tiling factories (60}70 wt% of PM10 were in the PM2.5 range). The grain-size distribution of tra$c particulate emissions was measured at di!erent places of the study area including major crossroads in the ceramic zone and in
the city of CastelloH . Under typical summer conditions, direct tra$c emissions did not give rise to high PM10 ambient air levels. PM10 levels of 30}40 lg m\ on an hourly basis were obtained around major crossroads inside the city of CastelloH (Table 6). The percentage of PM10 over TSP ranged between 60 and 65 wt%, whereas the PM2.5 fraction over PM10 ranged from 45 to 70 wt% (Fig. 7). Intermediate PM10 ambient air levels (around 70 lg m\ of PM10 for a 1/2 h basis) were obtained in areas with intensive biomass combustion activities around large orange-tree plantations. However, the high density of biomass "res could make this emission type a very important source for PM10 in the study area. In the vicinity of the "res the percentage of PM10 over TSP was approx. 50 wt%, whereas the PM2.5 fraction over PM10 reached only 40 wt% (Table 6 and Fig. 7). Measurements of the marine aerosols obtained at different sites of the shoreline in periods with a dominant daytime in-land breeze #ow, showed PM10 levels from 25 to 50 lg m\ of PM10 (on an hourly basis). The percentage of PM10 over TSP was constantly around 85 wt% and the PM2.5 fraction over PM10 ranged from 45 to 75 wt%. Constant levels of 5}8 lg m\ were measured for fractions (0.8 lm (Table 6 and Fig. 7) which coincide with the levels and the grain size distribution obtained for ammonium sulphate phases with the cascade impactor. Measurements were also made in the plume of the petrochemical plant located on a coastal site at the south of the city of CastelloH . PM10 levels were relatively low (approx. 20 lg m\ hourly PM10) compared with the other anthropogenic source. The grain-size distribution was very similar to that of the marine aerosols, with levels of "ne secondary particles similar to those of the background marine measurements (Fig. 7).
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Fig. 7. Selected cases of grain-size distribution of hourly levels of total suspended particles measured in the vicinities of non-ceramic emission sources. Levels in lg m\. See codes in Table 6 and Fig. 3 for location of measurement sites.
Fig. 8. Grain-size distribution of hourly levels of total suspended particles measured in rural-remote (Bartolo Mt.) and semi-urban (Alcora, Onda) background areas. Levels in lg m\. See codes in Table 6 and Fig. 3 for location of measurement sites.
4.4. Grain-size distribution of atmospheric particulates: ambient air measurements One set of measurements was performed following a cross-section from the coastal area towards the ceramic-producing zones during the daytime in-land breeze circulation stage (Table 6). The measurements were performed in background rural and suburban areas and showed a clear trend of an increase in the particulate levels from the coastal area (20 lg PM10 m\ and 15 lg PM2.5 m\) towards the ceramic area (36 lg PM10 m\ and 25 lg PM2.5 m\). The "nest fraction (mainly (0.8 lm sulphate) also followed the same trend (from 8 to 12 lg m\). All the measurements of this crosssection also showed two grain-size modes of around 1.6}3.0 and 5.0}7.5 lm, corresponding to marine aerosols. However, there is a marked trend to increase progressively the 5.0}7.5 lm mode (Fig. 8), probably due to the increase in nitrate levels and primary ceramic particulates towards the ceramic zone. In addition to these
modes, two additional coarse particulate inputs are evident (in the 10}15 and '20 lm) as the ceramic area is approached (Fig. 8). These grain size patterns and levels were also constantly recorded by a number of additional measurements performed at ceramic background sites around L'Alcora and Onda (Table 6 and Fig. 8). The results of the measurements performed on the rural background station of Mt. Bartolo evidenced levels of PM10 around 25 lg m\, of which 1/3 proceed from the ammonium sulphate phases (8 lg m\ in the (0.8 lm fraction). In addition to other possible particulate inputs such as nitrates and crustal particles, the two other modes (2}3 and 5}7.5 lm) identi"ed were coincident with the bi-modal distribution of the marine aerosol (Fig. 8). The presence of relatively high levels of ammonium sulphate at this site during the daytime breeze stage supports the high re-circulation of this secondary phase. In summer, the emission plumes from the ceramic zones are dragged by the nocturnal seaward breeze which
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857
the seaward transport of pollutants from the ceramic area (Fig. 9). However, the levels of PM1 and PM2.5 did not exhibit major changes during the daily cycle, with the 2.5}10 lm fractions being responsible for the increase in PM10 levels (Fig. 9). Because of the longer transport of pollutants, the increase in the '10 lm fraction registered close to the ceramic emission sources (Onda) was not recorded at the Grau station. The high impact of 2.5}10 lm particles on bulk PM10 levels is also evidenced by the measurements performed at L'Alcora. At this site, high levels of PM25 and PM10 are reached during the daytime stage, when local ceramic emissions are relatively high. At this stage the emission plumes are dragged towards the northwestern areas by the inland breeze circulation. Subsequently, in the nocturnal period, these high particulate air masses travel back to the emission-source area due to the seaward breeze. These processes account for the higher PM10 levels reached during the nocturnal stage with respect to the daytime stage (Fig. 9). Because of the breeze transport and consequent grain-size segregation, nocturnal levels of '10 lm particles are low when compared with the daytime stage. Once more it becomes very evident that the grain-size range which detects the impact of these polluted air masses on the ambient air quality is that of 2.5}10 lm (Fig. 9). The two major PM10 peaks registered between 21}22 and 7}8 h (both local time, see Fig. 9) probably mark the calm periods produced during the change in wind direction between the breeze stages. A similar situation was found at the Onda station where the impact of emission plumes from the nearby ceramic emission sources is not as important as in L'Alcora, but the nocturnal breeze circulation also accounts for high 2.5}10 and '10 lm particulate levels. The PM2.5 levels did not evidence the impact of these plumes at all (Fig. 9). The calm periods between breeze stages are also evidenced in the late evening and early morning by high particulate events (Fig. 9).
Fig. 9. Time evolution of levels of di!erent grain-size fractions of atmospheric particulates in the daily breeze cycle at the Grau, Onda and L'Alcora monitoring stations. Levels in lg m\. The simultaneous wind speed and direction measurements are also included to show the breeze dynamics observed during the measuring period.
accounts for a rise of the nighttime coastal particulate levels. 24 h measurements with semi-hourly particulate levels performed at the Grau station demonstrated that in the daytime stage all grain-size fractions remained at relatively low levels due to the relatively clean marine air mass #ows (see levels of particles and wind velocity and direction in Fig. 9). Later, in the nocturnal stage (21}7 h) the PM10 levels increased drastically as a consequence of
5. Conclusions Although the ceramic primary particulate emissions from the CastelloH area have a coarse grain-size distribution, the particulate transport dominated by the breeze circulation accounts for a subsequent grain-size segregation. Thus, major impacts on the ambient air quality of the coastal area induced by the particulate ceramic emissions occur in the nocturnal period due to the seaward transport of polluted air masses. Levels of ambient air particles increase mainly in the 2.5}10 lm range due to grain-size segregation by transport. The chemical composition of the ceramic particulate emissions is very similar to the crustal end-member but high Al, Fe and Ti levels coupled with a peculiar grain-size distribution in the major insoluble phases
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allows us to identify the ceramic input in the particulate matter. Although replacement of PM10 by PM2.5 measurements in ambient air quality monitoring standards is a likely trend for the future, the PM2.5 is not an adequate parameter for monitoring the impact of primary particulate emissions (such as ceramic emissions) on air quality, since the major particulate ambient air levels are in the range of 2.5}10 lm. As demonstrated from the analysis of major and trace elements in simultaneous PM10 and PM2.5 sampling and cascade impactor and from the Grimm measurements, PM2.5 measurement avoids the interference of crustal particulates without major reduction in the secondary anthropogenic load with the exception of nitrate. However, occasionally industrial primary particulate emissions may have the crustal particulate grain-size, and consequently these emissions will not be detected by PM2.5 measurements. From a technical point of view, the measurement of atmospheric particulates has to be speci"c for monitoring areas with major secondary or primary particulate emissions. In areas characterised by major secondary particulate emissions, PM2.5 monitoring should detect anthropogenic particulate pollutants without crustal particulate interference, whereas PM10 measurements should be used in areas with major primary anthropogenic particulate emissions. Acknowledgements The present study has been supported by the Plan Nacional de I#D of the Spanish CICYT, project AMB98-1044, and by the Spanish Ministry of the Environment. We would like to express our gratitude to the DireccioH General de EducacioH i Qualitat Ambiental of the Generalitat Valenciana for supplying the data from the monitoring stations and for their interest in the development of this study. References Dockery, D., Pope, A., 1996. Epidemiology of acute health e!ects: summary of time-series studies. In: Wilson, R.,
Spengler, J.D. (Eds.), Particles in Air: Concentration and Health E!ects. Harvard University Press, Cambridge, USA, pp. 123}147. EU Directive 1999/30/EC, 1999. Council directive relating to limit values for sulphur dioxide, nitrogen dioxide and oxide of nitrogen, particulate matter and lead in ambient air. The Council of the European Union. Harrison, R.M., Pio, C., 1983. Size di!erentiated composition of inorganic aerosol of both marine and polluted continental origin. Atmospheric Environment 17, 1733}1738. Harrison, R.M., Kito, A.M.N., 1990. Field inter-comparison of "lter pack and denuder sampling methods for reactive gaseous and particulate pollutants. Atmospheric Environment 24A, 2633}2640. IPCC, 1996. Climate change. In: Houghton, J.T., Meira Filho, L.G., Callander, B.A., Harris, N., Kattenberg, A., Maskell, K. (Eds.), The Science of Climate Change. Cambridge University Press, Cambridge, UK, 584pp. Kiehl, J.T., Rhode, H., 1995. Modelling geographical and seasonal forcing due to aerosols. In: Charlson, R.J., Heintzenberg, J. (Eds.), Aerosol Forcing of Climate. Wiley, New York, pp. 281}296. Mildford, J.B., Davidson, C.I., 1987. The sizes of particulate sulphate and nitrate in the atmosphere: a review. Journal of Air Pollution Control Association 37 (2), 125}134. MillaH n, M.M., Artin ano, B., Alonso, L., Navazo, M., 1991. The e!ect of meso-scale #ows on regional and long-range atmospheric transport in the Western Mediterranean area. Atmospheric Environment 25A (5/6), 949}963. MillaH n, M.M., Salvador, R., Mantilla, E., 1997. Photooxidant dynamics in the Mediterranean basin in summer: results from European research projects. Journal of Geophysical Research 102 (D7), 8811}8823. Querol, X., Alastuey, A., Puicercus, J.A., Mantilla, E., Ruiz, C.R., LoH pez-Soler, A., Plana, F., Juan, R., 1998. Seasonal evolution of suspended particles around a large coal-"red power station: chemical characterisation. Atmospheric Environment 32 (11), 719}731. US-EPA, 1987. Second addendum to air quality criteria for particulate matter and sulfur oxides (1982): assessment of newly available health e!ects information. Research Triangle Park, EPA Report 600/8-86-020F, NTIS PB87-176574. US-EPA, 1996. Air quality criteria for particulate matter. EPA/600/P-95/001F, US Environmental Protection Agency, Washington, DC. Wall, S.M., John, W., Ondo, J.L., 1988. Measurement of aerosol size distribution for nitrate and major ionic species. Atmospheric Environment 22, 1649}1656.
Atmospheric Environment 35 (2001) 845}858
Monitoring of PM10 and PM2.5 around primary particulate anthropogenic emission sources Xavier Querol *, AndreH s Alastuey , Sergio Rodriguez , Felicia` Plana , Enrique Mantilla, Carmen R. Ruiz Instituto de Ciencias de la Tierra **Jaume Almera++, CSIC, C/Lluis Sole& Sabarn& s, s/n, 08028 Barcelona, Spain Centro de Estudios Ambientales del Mediterra& neo, CEAM. Parque tecnolo& gico, C-4, sector oeste, 46980 Paterna (Valencia), Spain Instituto de Carboqun& mica, CSIC, C/Marn& a de Luna 12, 50015 Zaragoza, Spain Received 29 February 2000; accepted 18 July 2000
Abstract Investigations on the monitoring of ambient air levels of atmospheric particulates were developed around a large source of primary anthropogenic particulate emissions: the industrial ceramic area in the province of CastelloH (Eastern Spain). Although these primary particulate emissions have a coarse grain-size distribution, the atmospheric transport dominated by the breeze circulation accounts for a grain-size segregation, which results in ambient air particles occurring mainly in the 2.5}10 lm range. The chemical composition of the ceramic particulate emissions is very similar to the crustal end-member but the use of high Al, Ti and Fe as tracer elements as well as a peculiar grain-size distribution in the insoluble major phases allow us to identify the ceramic input in the bulk particulate matter. PM2.5 instead of PM10 monitoring may avoid the interference of crustal particles without a major reduction in the secondary anthropogenic load, with the exception of nitrate. However, a methodology based in PM2.5 measurement alone is not adequate for monitoring the impact of primary particulate emissions (such as ceramic emissions) on air quality, since the major ambient air particles derived from these emissions are mainly in the range of 2.5}10 lm. Consequently, in areas characterised by major secondary particulate emissions, PM2.5 monitoring should detect anthropogenic particulate pollutants without crustal particulate interference, whereas PM10 measurements should be used in areas with major primary anthropogenic particulate emissions. 2001 Elsevier Science Ltd. All rights reserved. Keywords: Atmospheric particles; PM10; PM2.5; Ceramic emissions; Ambient air quality monitoring; Primary particles; Mediterranean basin
1. Introduction Atmospheric particulates, especially secondary anthropogenic "ne particles, have been proven to have a major impact on human health (Dockery and Pope, 1996). For many years, the atmospheric particulate standards of many countries were based on the mass concentration measurement of the total suspended particles
* Corresponding author. Tel.: #34-93-4095410; fax: #3493-4110012. E-mail address: [email protected] (X. Querol).
(TSP). Since an important mass fraction of TSP is made of non-inhalable particles with a lower impact on respiratory and cardiovascular diseases, the relationship between health e!ects and TSP levels was found to be much lower than the levels of atmospheric particulates "ner than 10, 2.5 or 1 lm (PM10, PM2.5 and PM1, respectively), on comparison. This was the reason for the application of PM10 and PM2.5 measurements to the US ambient air quality standards (US-EPA, 1987 for PM10; US-EPA, 1996 for PM2.5). Although a decade later, the European Union (EU) countries have followed the same trend of replacing ambient air standards based on TSP by PM10 standards. Currently, the incorporation of ambient air standards based on PM2.5 is also
1352-2310/01/$ - see front matter 2001 Elsevier Science Ltd. All rights reserved. PII: S 1 3 5 2 - 2 3 1 0 ( 0 0 ) 0 0 3 8 7 - 3
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being considered in the EU (EU Directive 1999/30/EC, 1999) Another important pattern of atmospheric particulates, which is still not considered in ambient air standards, is the chemical composition of TSP, PM10, PM2.5 and PM1. Major secondary acidic aerosols and hazardous organic particulates are "ne-grained. Generally, inorganic secondary aerosols are in the (0.5 lm (sulphate and nitrate) and 0.5}5.0 lm (a fraction of nitrate) size range (Mildford and Davidson, 1987), marine aerosol salts have a major fraction in the range of 1.0}5.0 lm, whereas, primary natural particles, mainly made of Al}Si minerals (clay minerals, quartz, feldspars) and calcium and magnesium carbonates, have a major proportion in the 5}25 lm range. The carbon contents of atmospheric particulates have a bimodal grain-size distribution with a mode in the (2.5 lm (corresponding to anthropogenic organic particles) and '10 lm (corresponding to mineral carbonates). Primary anthropogenic particulate emissions are also usually in the '2.5 lm range. At a global scale, the anthropogenic emissions do not exceed the 10% of the global particulate emissions, whereas the natural primary emissions reach the 84% (2.9;10 t yr\, after Kiehl and Rhode, 1995; IPCC, 1996). Concerning the global anthropogenic particulate emissions, the secondary aerosols exceed the primary particulate emissions (0.26;10 and 0.11;10 t yr\). Consequently, the global emissions of natural particulates are mainly primary, whereas, the anthropogenic emissions are predominantly secondary. Future trends for particulate monitoring strategies tend to monitor PM2.5 rather than PM10 because of its more direct relationship with health e!ects and to avoid natural particulate interference. However, industrial activities with high primary particulate emissions, such as cement, concrete, ceramics or the mining sectors, may have a great impact on the ambient air quality due to their intensive particulate emissions in the 2.5}10 lm range. Moreover, these emissions usually have a chemical composition similar to that of natural crustal emissions (high Ca, Al, Si, Fe, K proportions), which impedes the appropriate monitoring of ambient air particulate levels. This paper introduces the results obtained from a research project supported by the Spanish Ministry of the Environment and the CICYT (ComisioH n Interministerial de Ciencia y TecnologmH a) to develop source apportionment analyses of PM10 and PM2.5 focussed on the speci"c atmospheric and geographical characteristics of Spain. The present study focuses on the evaluation of the physico-chemical patterns of ambient air particulate matter in ceramic industrial zones. In these areas, although high levels of secondary particulates may be emitted, the largest source contribution in high particulate events is due to primary emissions of mineral matter from atomiser plants and fugitive emissions from piling stock. Continuous grain-size analysis of TSP from
di!erent sources and simultaneous PM2.5 and PM10 sampling and analysis were carried out to de"ne the best parameter for monitoring the impact of ceramic industrial emissions on ambient air quality.
2. The study area The ceramic industrial areas of L'Alcora, Onda and Vilareal spread along the Millars river basin from the coast to the interior of the CastelloH Province in Eastern Spain (Fig. 1). The CastelloH industrial area is the second largest ceramic-producing zone in the world, accounting for 17% of the world's basic ceramic production (600;10 m yr\). The supply of clays for the industry comes mainly from an open-pit mine at a Triassic red kaolinite-rich clay deposit in Sant Joan de MoroH (east of the city of L'Alcora, Fig. 1) and from the Cretaceous kaolinite-rich deposits in the province of Teruel. In a minor proportion, a large variety of other natural and synthetic products, such as feldspars, melting phases and
Fig. 1. Location of major ceramic production areas and "xed sampling stations for PM10/PM2.5 measurements.
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colourants, are also broadly consumed. The kaoliniterich material is "nely ground in the atomisers, which produces a homogeneous "ne powder ((63 lm). This process coupled with the large clay consumption (20;10 t in 1998) and the large fugitive emissions from the storage, handling and transport of the clay, probably accounts for the largest fraction of the local anthropogenic particulate emissions. Secondary particulate emissions from the manufacturing of glass and enamel may account more for the emission of hazardous atmospheric trace pollutants than for their signi"cant contribution to the bulk particulate emissions. Other particulate emission sources such as intensive road transport, frequent biomass combustion from intensive orange tree cropping, and marine aerosols, must also be considered. This puzzling particulate-emission setting is placed in a complex Mediterranean atmospheric environment. The intensive convective dynamics, the breeze circulation, the low rainfall rate, the highly mineralised soils and the frequent occurrence of high particulate Sahara air-mass intrusions further complicate the monitoring of the anthropogenic particulate emissions impact on ambient air quality. The study was made in July because of the large impact of some of the previously mentioned atmospheric environmental factors on the particulate levels. In summer, the North Atlantic anticyclone becomes reinforced over the northern latitudes. Weak-gradient conditions on the Iberian Peninsula and strong ground heating give rise to the development of the Iberian thermal low (ITL), due to thermally induced local and mesoscale circulations, such as sea breeze, up-slope winds and convective cells (MillaH n et al., 1991). The study area (Fig. 1) includes the CastelloH alluvial plain (La Plana) which is limited on the north by the Palmes mountain chain (6}7 km from the coast) and includes Mt. Bartolo as its highest peak (780 m.a.s.l.). The Millars basin, with an approximate E}W direction, converges with the "rst range of mountains at 20 km from the coast. The movement of the air masses over the eastern Coast of the Iberian Peninsula as well as the evolution of the boundary layer are strongly linked to its complex topography. During the daytime the sea breeze is channelled
847
along the bottom of the valleys up to 60}80 km inland, whereas at the top of the mountains and valley slopes a combination of sea breeze and up-slope winds gives rise to a chimney e!ect, injecting air from low levels to altitudes ranging from a few hundred meters up to 2}3 km. The anticyclonic subsidence and the dynamics formation of the sea breeze cells favour the formation of reservoir layers of secondary pollutants (thermally separated between themselves by inversions) in the return #ow moving toward the Mediterranean Sea. A compensatory sinking over the sea, due to thermal buoyancy over the warmed terrain and anticyclonic subsidence, reinforces the sea-breeze circulation and prepares the reservoir layers over the sea for re-entrance a few days later. During the evening and night, the solar-activated circulations cease, and a reversal in the breeze takes place. Thus, the sea-breeze circulation in summer favours good ventilation conditions in the valleys but scarce air-mass renovation, due to the above-described re-circulations of the air masses (MillaH n et al., 1997), resulting in a potential atmospheric reservoir e!ect for secondary air pollutants in the Western Mediterranean.
3. Methodology 3.1. Sampling sites The following sampling and measurement sites (Fig. 1 and Table 1) were selected based on the distribution of the major emission sources (marine, rural, urban and industrial sites) and on the atmospheric-circulation peculiarities of the study area: The Grau station is located in a rural or semi-urban area, which is sporadically in#uenced by the industrial and urban plumes, especially the plume from CastelloH in night-breeze conditions. The station of the Villareal city is an urban site in the lower watercourse of the Millars, situated 10 km from the coastline, in the centre of a zone of a large ceramicindustrial activity. This station is under the in#uence of both urban (mainly tra$c) and industrial emissions. During the daytime period this location is situated leeward of the city and the ceramic emissions with respect to the
Table 1 Location of the "xed monitoring and sampling stations Sampling site
Location
Latitude
Longitude
Mt. Bartolo Onda Vilareal Grau L'Alcora
Telecom antenna peak Monitoring station (urban background station) Post o$ce (urban background station) Monitoring station (urban background station) Council house (urban background station)
40305 09 N 39357 43 N 39356 34 N 39358 59 N 40305 09 N
00301 53 W 00315 43 W 00306 25 W 00300 31 W 00301 53 W
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characteristic breeze #ow. For this reason, the contributions due to tra$c emissions should be equal or more important than the industrial emissions. On the other hand, the in#uence of the ceramic emissions are expected to predominate during the nocturnal breeze period. The Onda station is a suburban background station near the city of Onda, situated in an open area, 20 km from the coastline, without direct in#uence from urban or road tra$c activities. It is situated on the leeward of the nearby ceramic industries, and in sea-breeze conditions it is also in#uenced by the coastal industrial emissions. The L+Alcora station is located in an urban background site in the municipality of L'Alcora, in the most productive ceramic zone of CastelloH . In the daytime the breeze drags the atmospheric emissions with a northwestern transport, whereas in the nocturnal breeze phase the previously emitted particulates travel seawards towards L'Alcora. Finally, the Mt. Bartolo station is located at the top of the Mt. Bartolo peak. Possible anthropogenic emissions could come from a nearby residential area and from various roadways concentrated on the coastal fringe. The objective of using this emplacement was to provide a vertical gradient for discriminating possible high-altitude contributions not present at lower levels. Lastly, meteorological data from the air quality network cabins of Ermita and Penyeta and the meteorological towers of Cirat, Rambla of the Viuda and Borriana were also used to carry out the interpretations. 3.2. Sampling and measurements
Fig. 2. Correlation of PM10 and PM2.5 measurements between the GRIMM laser spectrometer and the high-volume sampler. Solid lines indicate 1:1, dashed line is the correlation line. In PM10, correlation was performed at the following sites: (1) Solid circles, suburban Onda station; (2) Solid triangles, rural Monagrega station; (3) Triangles, urban Barcelona station; (4) Squares, urban L'Hospitalet station. PM2.5 correlation was performed at Onda (2 samples) and L'Hospitalet.
The sampling of atmospheric particulate matter was carried out by means of high-volume samplers (DH-80 and MCV-CAF, 30 m h\) equipped with PM10 and PM2.5 DIGITEL and MCV cut-o! inlets and quartz glass "lters (QF20 Schleicher and Schuell). Daily sampling was made from 12 to 23 July 1999 at the "ve "xed monitoring stations (Table 1). Furthermore, sampling of TSP grain-size fractions (seven stages from 0.3 to '20 lm) was performed for 4 days (from 11 to 23 July 1999) at the Onda station by means of a Retsch PI-1 cascade impactor. Once the levels of bulk particulates were obtained by weighting the "lters using standard procedures, one-half of each of them (PM10 and PM2.5) plus the insoluble fractions of the di!erent stages of the cascade impactor (previously "ltered with MQ cellulose membrane "lters) and blank "lters were digested following the method of Querol et al. (1998). The soluble fraction of 1/4 of each "lter and the di!erent grain-size stages obtained with the cascade impactor were extracted with distilled water at 803C. The last 1/4 of each "lter was used to directly determine the total C content by LECO methodology.
The solutions obtained were analysed by: (a) inductively coupled plasma-atomic emission spectrometry (ICP-AES) for major elements, (b) capillary electrophoresis (CEF) for anions, and (c) colorimetry-#ow injection analysis (FIA) for NH>. The digestion of blank "lters with 2}3 mg of NBS-1633a reference material was used to ensure analysis quality for the same levels of the sample digestion concentrations. Relative analytical errors were between 3 and 10% for the elements studied. Automatic measurements of atmospheric particulate levels and grain-size distribution were performed with the laser spectrometer dust monitor GRIMM 1108 (Labortechnik GmbH & Co. KG) at the "xed and mobile stations. This dust monitor permits the determination of particulate levels in 15 di!erent grain-size channels from 0.3 to '20 lm. The accuracy of the GRIMM-1108 measurements was checked, before, during and after the "eld campaigns, by comparing the levels of simultaneous daily PM10 and PM2.5 measurements obtained with the standard gravimetric methodology. Fig. 2 shows good agreement between the PM10 measurements obtained
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Table 2 Location of mobile station for grain-size analysis of TSP with the GRIMM laser spectrometer around the major emission sources (E) and ambient air measurements (A) No.
Measurement description
Longitude
Latitude
E-1 E-2 E-3 E-4 E-4b E-5 E-6 E-7 E-8 E-9 E-10 E-11 E-12 E-12b E-13 E-14 E-15 E-16 E-17 E-18 E-19 E-20 E-20b A-1 A-2 A-3 A-4 A-5 A-6 A-7 A-8 A-9
Fugitive emissions from a clay mine Fugitive emissions from clay transport at L'Alcora Atomiser, Onda Atomiser L'Alcora Atomiser L'Alcora second measurement Around stack emissions PA factory Around stack emissions SA factory Around stack emissions VE factory Around stack emissions JM factory Around stack emissions JM factory second measure Around stack emissions EG factory Around stack emissions NA factory Around stack emissions POR factory Emission plume measurement POR factory Emission plume measurement PA factory Dense tra$c crossroad at CastelloH Dense tra$c crossroad at CastelloH Emission plume from petrochemical plant Biomass "ring around orange tree plantations Marine aerosols Borriana harbour (Morro) Marine aerosols Millars delta Marine aerosols Ben Afali beach Marine aerosols Ben Afali beach on the shoreline Northern background levels around the ceramic zone Middle background levels in orange plantations Coastal background levels leeward of ceramic emissions Urban background levels L'Alcora Semi-urban background levels L'Alcora (St. Salvador) Urban background levels L'Alcora Semi-urban background levels L'Alcora}Onda Semi-urban background levels Millars bridge Rural-remote background levels Mt. Bartolo
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
40 40 39 40 40 39 40 39 39 39 39 39 40 40 39 39 39 39 39 39 39 39 39 39 39 39 40 40 40 39 39 40
with the high-volume sampler and the GRIMM-1108 laser spectrometer. Although good agreement was also obtained in the two simultaneous PM2.5 measurements during the "eld campaign, a longer inter-comparison demonstrated that the GRIMM 1108 measurements were 15% lower than those obtained by the gravimetric method (Fig. 2). The measurements of particulate-matter levels and grain-size distribution with the laser spectrometer were carried out in the vicinities of the following emission sources (Table 2 and Fig. 3): 1. Di!erent types of ceramic emission plumes including those from enamel (white to yellow plumes) and tile (reddish plumes) factories and atomiser centres. Fugitive emissions were measured at a certain distance of a number of sources including the stockpiles in the atomiser centres, the largest open-pit mine in the area,
2.
3.
4.
5.
06 10 14 10 10 04 09 14 04 04 09 13 05 05 04 02 03 01 01 04 00 00 00 16 09 04 11 11 12 10 07 01
31 08 35 29 29 50 11 49 21 20 35 07 38 38 41 14 19 06 03 13 49 15 15 10 44 03 20 49 30 46 11 53
W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W
04 03 58 03 03 57 02 58 57 57 56 57 01 01 57 59 58 57 59 51 54 55 55 59 59 54 04 05 04 59 57 05
39 00 18 29 29 38 36 11 51 56 41 41 21 21 22 22 19 06 36 32 22 20 20 10 09 45 02 11 10 29 54 09
N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N
and a crossroad where high emissions from the short road transport between the clay-mining area and the tiling and atomising centres were evident. The tra$c emissions in the vicinity of a crossroad with high tra$c density (mainly cars) at two di!erent sites inside the city of CastelloH . The marine aerosol at three di!erent coastal sites (a few metres from the shoreline) in the in-land breeze circulation stage. The biomass combustion emissions were measured at di!erent distances from the "res in extensive orangetree plantations located upwind from the ceramic emissions in the Grau area. The emission plume from the petrochemical plant was detected with the help of the SO analysers in a COS PEC unit and, subsequently, grain-size measurements were obtained without interference of the ceramic emissions in the in-land breeze stage.
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4.1. PM10 and PM2.5 levels
Fig. 3. Location of mobile measurement stations for grain-size analysis of TSP with the GRIMM laser spectrometer around the major emission sources (E) and ambient air measurements (A). See detailed data of location in Table 2.
In addition to the emission measurements, short (1}2 h) measurements were performed in background areas up- and down-wind of the emission plumes from the ceramic zones (Table 2 and Fig. 3). The measurements were performed in the in-land breeze stage following a cross-section from the shoreline (backwards to the petrochemical and ceramic emissions), downwind of the petrochemical emission and "nally downwind of the ceramic emission plumes. Short measurements were also carried out at di!erent background sites in#uenced by di!erent ceramic emission sources. Longer measurements (24 h) were carried out at the Grau, L'Alcora and Onda stations to study the grain size range of atmospheric particulates in#uenced by the ceramic emissions transported by the breeze circulation.
4. Results and discussions During the measurement campaign typical summer meteorological conditions predominated with a localcirculation dominance in the measuring zone, in spite of the fact that a smooth perturbation aloft took place at the end of the "rst week. Thus, the scenario consisting of a daytime inland and a nocturnal seaward #ow was repeated daily in the Millars Valley during the measurement campaign. The typical summer thermal vertical structure with subsidence inversions was also observed.
As expected, the lowest PM10 mean values were obtained at the Mt. Bartolo background station (18 lg m\). The highest PM10 values were registered at the L'Alcora and Vilareal stations (56 and 44 lg m\, respectively) which are located in the most productive ceramic areas. The Grau and Onda stations, located in rural or suburban areas, which are temporarily in#uenced by the emission plumes, have intermediate PM10 values of approx. 30 lg m\. The mean PM2.5 fraction of PM10 in the study area was approx. 50%wt, whereas the mean PM10 fraction of total suspended particles (TSP) was found to be approx. 65%, with extreme mean daily values from 50 to 80 wt%. The levels of marine aerosols were homogeneously distributed in the study area as deduced from the narrow variations in the concentrations of Na>, Cl\ and Mg> observed among the di!erent sampling sites (Table 3). A similar homogeneous pattern was observed for levels of sulphate and ammonium (Table 3). The background, the suburban and the industrial stations showed mean levels ranging only from 7 to 9 lg m\ for anthropogenic sulphate and 2.1}2.8 lg m\ for ammonium. The ionic balance between ammonium and sulphate demonstrates that around 80% of the anthropogenic sulphate is present as ammonium sulphate. The occurrence of ammonium sulphate, sodium chloride and magnesium probably in discrete background aerosols probably accounts for the homogeneous levels of these phases in PM10 across the study area. Conversely, the nitrate levels were considerably higher at the Vilareal site (with the highest tra$c density) and lower, by a factor of 4}5, at the rural background site of Mt. Bartolo (Table 3). A similar pattern was also observed for the distribution of levels of organic carbon and phosphor. The other stations registered intermediate values for nitrate and organic carbon with the exception of the suburban Grau station. The frequent uncontrolled biomass combustion from intensive orange tree cropping around this station probably accounted for the high levels of organic carbon, phosphor and nitrate, similar to those recorded at the heavily polluted Vilareal site. The levels of the major elements emitted by the ceramic industry (clay-related elements such as Si, Al, Fe, K and Ti) were one order-of-magnitude higher at the L'Alcora and Vilareal stations than at the Bartolo site, with the Onda and Grau stations having intermediate levels (Table 3). Levels of Ca and Mg, mainly from soil emissions with a low proportion from the ceramic industry, also increased in the ceramic zone with respect to the background site but in a lower rate than the ceramicrelated elements. On an average, the addition of all the constituents determined reached 90% of the bulk PM10 or PM2.5
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851
Table 3 Mean daily major elements, carbonates, ammonium, organic#elemental carbon and bulk PM10 levels obtained at Mt. Bartolo, Grau, Onda, Vilareal and L'Alcora sampling sites Location
Bartolo
Grau
N
5
9
CO\(lg m\) Org#Elem C (lg m\) SiO (lg m\) Al O (lg m\) Ca (lg m\) K (lg m\) Mg (lg m\) Fe (lg m\) NO\ (lg m\) NH> (lg m\) SO\ no marine (lg m\) SO\ marine (lg m\) Na (lg m\) Cl\ (lg m\)
0.7 2.9 1.1 0.4 0.5 0.2 0.2 0.2 0.9 1.9 7.0 0.2 0.8 0.2
2.0 6.1 2.7 1.1 1.3 0.5 0.3 0.4 2.9 2.5 8.4 0.3 1.2 0.8
Onda 11 1.6 3.9 3.6 1.4 1.0 0.5 0.2 0.4 1.8 2.3 8.7 0.2 1.0 0.4
Vilareal 9 3.5 6.8 6.0 2.4 2.3 0.8 0.4 0.7 3.5 2.1 9.0 0.4 1.4 0.9
L'Alcora 2 4.3 5.5 12.0 4.8 2.9 1.5 0.4 1.2 1.8 1.9 8.4 0.2 0.9 0.5
R major elements (lg m\) PM10 gravimetry (lg m\) Determined (%)
17 19 91
31 36 85
27 32 85
41 44 94
48 56 86
Crustal (%) Secondary (%) Org#Elem C (%) Marine A (%)
19 57 17 7
27 45 20 8
33 47 14 6
40 37 17 7
58 27 12 4
N, number of daily samples. The results of the source apportionment analysis including crustal sources, secondary particulates (ammonium sulphate and nitrate), organic#elemental carbon, and marine aerosols are also reported as the percentage of contribution of each source with respect to the bulk PM10 levels.
levels obtained by the gravimetric method. The results indicate that the mean marine aerosol input represents between 4 (L'Alcora) and 8 (Grau) wt% of the bulk PM10 levels (Table 3). The proportion of organic and elemental carbon, mainly proceeding from combustion processes, is relatively homogeneously distributed across the study area with values from 12 to 20% wt of bulk PM10, with the highest values being recorded for the Grau and Vilareal sites (Table 3). The PM10 proportion from the crustal input (both soil and ceramic emissions) ranged from 18% of bulk PM10 at the Bartolo site, up to 40}55 wt% in the ceramic productive area. The Onda and Grau sites have intermediate proportions (around 30 wt%). Finally, the proportion of secondary inorganic aerosols (ammonium, sulphate and nitrate) is very high at the background site (near by 60% of bulk PM10 levels) and the Onda and Grau sites (45}50 wt%), whereas in the ceramic zone (Vilareal and L'Alcora) it is much lower (approx. 30 wt%), the background origin of ammonium sulphate in the study area. Thus, in the rural background site, these external phases account for most of the particulate fraction, whereas this proportion is drastically
reduced in the ceramic zone, where local input predominates. Levels of Pb and Zn also reached high values in the ceramic zone (around 0.4 lg m\) but very low levels at the rural background site (0.05 lg m\, Table 4). Although the levels of the other elements were relatively low, with the exception of As (up to 25 ng m\) and Cr (up to 7 ng m\) at L'Alcora and Vilareal, the spatial variation of levels of As, Cr, Cs, Pb, Rb, Sr, Ti, V, Zn and Zr suggests a chie#y ceramic origin for these elements (Table 4). However, Ba, Cd, Co, Cu, Ga, Hf, Mn, Mo, Nb, Ni, Sb, Sc, Sn, Th, U and Y do not show any relationship with ceramic emissions (Table 4). The last conclusion demonstrates that the well-known relationship between some ceramic activities and the high levels of Hf, U and Th in atmospheric particles has a very local incidence. Analysis of simultaneous samples of PM10 and PM2.5 has evidenced that the crustal and marine loads are strongly reduced in the PM2.5 with respect to the PM10 (Table 5) measurements. In contrast, most of the secondary anthropogenic phases are trapped by the PM2.5 sampling, with the exception of nitrate which registers
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Table 4 Mean daily trace element levels in PM10 obtained at Mt. Bartolo, Grau, Onda, Vilareal and L'Alcora sampling sites (N, number of daily samples)
Table 5 Comparison between levels of major and trace elements, carbonates, ammonium, organic#elemental carbon in PM10 and PM2.5, simultaneously sampled at Onda
Location
Onda
N As (ng m\) Ba (ng m\) Cd (ng m\) Co (ng m\) Cr (ng m\) Cs (ng m\) Cu (ng m\) Ga (ng m\) Hf (ng m\) Mn (ng m\) Mo (ng m\) Nb (ng m\) Ni (ng m\) P (ng m\) Pb (ng m\) Rb (ng m\) Sb (ng m\) Sc (ng m\) Sn (ng m\) Sr (ng m\) Th (ng m\) Ti (ng m\) U (ng m\) V (ng m\) Y (ng m\) Zn (ng m\) Zr (ng m\) La (ng m\) Ce (ng m\) Tb (ng m\) Tm (ng m\) Yb (ng m\)
Bartolo
Grau
Onda
Vilareal
5
9
11
9
2
1 1 0.1 0.4 0.6 0.1 77 0.1 0.2 5 0.6 0.1 5 15 45 1 1 0.1 1 2 0.7 12 (0.1 8 0.1 54 3 0.2 0.2 0.03 0.03 0.02
5 11 0.7 0.3 1.7 0.3 36 0.1 0.4 7 0.6 0.1 3 50 199 1 2 0.1 2 4 0.6 29 0.2 7 0.2 132 8 0.3 0.7 0.03 0.03 0.04
11 16 0.6 0.6 3.6 0.5 39 0.2 0.5 11 2.9 0.2 7 52 346 3 2 0.2 2 6 0.9 65 (0.1 10 0.3 264 12 0.6 1.3 0.03 0.03 0.04
25 21 0.9 1.1 6.9 1.2 88 0.5 0.4 13 2.2 0.3 9 42 341 6 2 0.3 2 10 0.2 111 (0.1 14 0.4 699 21 1.1 2.2 0.03 0.02 0.06
8 6 0.4 0.6 2.2 0.4 6 0.2 0.4 7 0.8 0.1 4 32 285 2 1 0.1 1 4 0.2 34 0.6 7 0.1 178 11 0.4 0.9 0.03 0.02 0.05
L'Alcora
only 40% of the PM10 nitrate levels. As it will be demonstrated later, the occurrence of calcium and sodium nitrate in the 2.5}5.0 lm range probably accounts for the lower nitrate measurements in the PM2.5 "lters. 4.2. Cascade impactor Ammonium and ammonium}calcium sulphates are mainly concentrated in the "nest fractions (0.3}0.7 and 0.7}1.0 lm, respectively). These two "ne fractions account for 80% of the bulk anthropogenic sulphate (Fig. 4). The coarser sulphate is mostly present as calcium and sodium sulphates. The marine aerosol phases are mainly concentrated in the 3}10 lm fraction as inferred from the Na> distribution (Fig. 4). However, there is a clear grain-size segregation between the occurrence of NaCl (6}10 and '10 lm fractions) and the NaNO ((6 lm fraction). This is due to the well-known Na>}NO\}Cl\}NH> interaction (Harrison and Pio, 1983; Wall et al., 1988). Ammonium
CO\ (lg m\) Org#Elem C (lg m\) SiO (lg m\) Al O (lg m\) Ca (lg m\) K (lg m\) Mg (lg m\) Fe (lg m\) NO\ (lg m\) NH> (lg m\) SO\ no marine (lg m\) SO\ marine (lg m\) Na (lg m\) Cl\ (lg m\)
21}22/07/1999
22}23/07/1999
PM10
PM2.5
PM10
PM2.5
4.6 2.1 5.1 2.0 1.4 0.6 0.3 0.5 1.3 1.9 6.8 0.2 0.8 0.3
4.4 1.2 2.3 1.2 0.8 0.5 0.1 0.3 0.5 1.8 6.1 0.1 0.3 0.2
5.7 2.2 4.9 2.1 1.4 0.7 0.3 0.6 1.4 2.1 7.1 0.2 0.8 0.5
4.6 0.4 0.7 0.5 0.2 0.4 0.1 0.2 0.4 2.0 6.7 0.1 0.2 0.2
R major elements (lg m\) PM10/2.5 gravimetry (lg m\) Determined (%)
28 33 87
20 23 90
31 37 84
17 17 100
Crustal (%) Secondary (%) Org C (%) Marine A (%)
43 36 16 5
33 42 22 3
41 35 19 5
16 54 27 3
10 8 0.6 0.5 2.0 0.5 10 0.3 7 0.3 0.2 3 33 354 3 1 1 5 (0.1 48 (0.1 6 197 8
10 3 0.5 0.2 1.5 0.4 9 0.1 5 0.2 0.1 3 22 330 2 1 1 2 (0.1 28 (0.1 5 186 4
10 9 0.6 0.5 2.1 0.5 10 0.1 8 (0.1 0.2 3 32 368 3 1 1 6 0.5 51 (0.1 7 204 8
7 2 0.4 0.1 1.0 0.3 10 0.3 3 (0.1 0.1 3 12 245 1 1 1 1 (0.1 14 (0.1 7 170 5
As (ng m) Ba (ng m) Cd (ng m) Co (ng m) Cr (ng m) Cs (ng m) Cu (ng m) Hf (ng m) Mn (ng m) Mo (ng m) Nb (ng m) Ni (ng m) P (ng m) Pb (ng m) Rb (ng m) Sb (ng m) Sn (ng m) Sr (ng m) Th (ng m) Ti (ng m) U (ng m) V (ng m) Zn (ng m) Zr (ng m)
The results of the source apportionment analysis including crustal sources, secondary particulates (ammonium sulphate and nitrate), organic#elemental carbon, and marine aerosols are also reported as the percentage of contribution of each source with respect to the bulk PM10/2.5 levels.
nitrate (originally present in the (6 lm fraction) reacts with sodium chloride to give rise to ammonium chloride (gas) and sodium nitrate. The ionic balance also indicates the occurrence of Ca(NO ) in the '6 lm
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Fig. 4. Grain-size distribution of weekly levels of the soluble fraction of major species (neq m\) and selected trace metals (ng m\) in total suspended particles obtained at Onda from 12 to 23 July 1999.
fraction probably due to nitri"cation of soil particles (Harrison and Kito, 1990) and NH NO in the (1.5 lm fraction (Fig. 4). As expected, SO\, NO\, Cl\, NH>, Ca, Mg, Mn, Pb, V and Zn have a major soluble fraction (Fig. 4), and Al, K, Sr, Ba, Cr, Cu, Ni, Ti and Fe are mainly present in insoluble phases (Fig. 5). Insoluble soil and ceramic particulates such as clay minerals, calcium carbonate and feldspars (crustal phases) showed a bi-modal grain-size distribution with modes occurring in the 1.5}6.0 and '25 lm fractions as deduced from the grain-size distribution of insoluble levels of Ca, Al, K and Fe (Fig. 5). Soluble fractions of Mn, Fe, V and Cr, probably occurring in di!erent oxide phases with an anthropogenic origin, are mostly in the 6}10 lm range (Figs. 4 and 5). However, Pb and Zn mainly occur in the soluble very "ne grain-size fraction, '85% of bulk Pb levels occurring in the PM2.5 fraction (Fig. 4).
853
Fig. 5. Comparison of the grain-size distributions of weekly levels of the insoluble fraction of major elements and selected trace metals in total suspended particles obtained at Onda in this study with that of a typical urban distribution obtained in Barcelona. Levels in ng m\.
Unusually high proportions of insoluble levels of Al, Ca, Na, Sr, S, P and Fe were found in the "ne grain-size modes ((1.5 lm) when compared with a normal urban or industrial grain-size distribution (Fig. 5). This atypical occurrence of "ne grain sizes for these elements and the unusually high proportion of insoluble Na levels (up to 30% of bulk Na) are probably the result of the condensation of volatile emissions from high temperature processes developed in the enamel manufacture. These peculiar patterns may be a good tool for tracing the input of ceramic emissions on bulk PM10 levels, since the bulk chemical patterns, characterised by high Al, Si, Fe and Ca levels, are similar to the soil end-member. 4.3. Grain-size distribution of atmospheric particulates around the emission sources The fugitive emissions from the largest open-pit clay mine in the area induced very high ambient air PM10
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Table 6 Mean daily major elements, carbonates, ammonium, organic#elemental carbon and bulk PM10 levels obtained at Mt. Bartolo, Grau, Onda, Vilareal and L'Alcora sampling sites. N, number of daily samples . Levels in lg m\
Ceramic emissions Fugitive emissions Clay mine E-1 Transport E-2 Atomiser-ATESA E-3 Atomiser-L'A E-4 Atomiser-L'A2 E-4b Around stack emissions PA E-5 SA E-6 VE E-7 JM E-8 JM-2 E-9 EG E-10 NA E-11 POR E-12 Direct measurements of plume emissions POR E-12b PA E-13
TSP
PM10
PM7.5
PM5
PM2.5
823 1770 387 420 532
PM1.0
PM0.8
337 704 113 128 214
266 560 97 108 187
163 340 75 78 137
61 185 43 40 74
9 21 11 10 16
7 15 9 8 12
349 127 353 78 83 135 267 483
251 56 170 38 44 64 84 218
223 49 158 35 40 59 75 188
159 38 157 30 38 49 68 142
83 22 150 24 35 33 57 84
21 6 126 12 24 12 22 21
16 5 120 11 23 10 17 16
855 2485
385 1018
330 867
247 610
144 289
33 47
25 34
Tra$c emissions CastelloH -1 CastelloH -2
E-14 E-15
62 47
42 27
35 26
26 23
17 19
8 9
7 8
Combustion emissions Petrochemical Biomass
E-16 E-17
25 149
22 73
21 58
19 43
15 28
7 13
6 12
Marine aerosols Borriana Millars Ben Afeli-1 Ben Afeli-2
E-18 E-19 E-20 E-20b
36 53 86 31
31 44 49 28
29 42 43 27
24 33 35 25
17 20 24 19
7 7 8 7
6 6 7 6
Ambient air measurements at background sites Cross-section North-ceramic A-1 55 Middle A-2 39 Coastal A-3 28
35 24 24
32 23 23
28 22 21
22 21 17
12 11 9
12 10 8
L'Alcora-1 L'Alcora-2 L'Alcora-3 L'Alcora}Onda Millars bridge Mt. Bartolo
46 41 43 24 43 25
42 36 37 22 40 24
33 29 27 18 34 21
22 20 16 15 27 16
8 9 7 8 14 8
8 8 6 7 13 7
A-4 A-5 A-6 A-7 A-8 A-9
91 62 66 33 62 32
The results of the source apportionment analysis including crustal sources, secondary particulates (ammonium sulphate and nitrate), anthropogenic organic#elemental carbon, and marine aerosols are also reported as the percentage of contribution of each source with respect to the bulk PM10 levels.
levels around the mining area (approx. 300 lg m\ were recorded on an hourly basis, Table 6 and Fig. 6), but the PM2.5 fraction was relatively low (22 wt% of the PM10). The PM10 fraction also represented a low TSP fraction
(40 wt%). As expected, this coarse grain-size distribution (high and low modes of '20 and 4}15 lm, respectively) was similar to that previously described for the clayrelated elements (Al, K, Fe) obtained from the cascade
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Fig. 6. Selected cases of grain-size distribution of hourly levels of total suspended particles measured in the vicinities of the major ceramic emission sources. Levels in lg m\. See codes in Table 6 and Fig. 3 for location of measurement sites.
impactor measurements. The grain-size distribution of ambient air particulates around di!erent clay atomisers and from several crossroads with high densities of clay road-based transport was also very similar (Fig. 6 and Table 6), with a major proportion in the '20 lm and two secondary modes occurring in the 4}7.5 and 10}15 lm fractions. The PM10 levels around these sites also reached very high levels (from 120 to 700 lg m\ on an hourly basis). The percentages of PM10 over TSP and PM2.5 over PM10 were constantly low (from 30 to 45 wt% and from 40 to 45 wt%, respectively) around the four atomisers. Although the TSP grain size pattern was slightly "ner around the atomisers when compared with the fugitive emissions from clay mining and transport, the similarity of these grain-size distributions suggests that the major emission source from these activities is the fugitive emissions from the large clay stockpiles and transport. PM10 levels around 10 ceramic factories including tiling and enamel factories were signi"cantly lower than around the mining, atomiser and clay-transport sources (Table 6 and Fig. 6). Levels ranging from 40 to 250 lg m\ of PM10 on an hourly basis were obtained around these ceramic factories which emit particulate matter mainly through small-stacks. The percentage of PM10 over TSP and PM2.5 over PM10 increased considerably with respect to the previous emission sources. Although a similar percentages of PM10 over TSP was determined for both tiling and enamel factories (from 50 to 65 wt%), the enamel sources were characterised by a higher proportion of "ne particles (from 80 to 95 wt% of PM10 were in the PM2.5 range) with respect to the tiling factories (60}70 wt% of PM10 were in the PM2.5 range). The grain-size distribution of tra$c particulate emissions was measured at di!erent places of the study area including major crossroads in the ceramic zone and in
the city of CastelloH . Under typical summer conditions, direct tra$c emissions did not give rise to high PM10 ambient air levels. PM10 levels of 30}40 lg m\ on an hourly basis were obtained around major crossroads inside the city of CastelloH (Table 6). The percentage of PM10 over TSP ranged between 60 and 65 wt%, whereas the PM2.5 fraction over PM10 ranged from 45 to 70 wt% (Fig. 7). Intermediate PM10 ambient air levels (around 70 lg m\ of PM10 for a 1/2 h basis) were obtained in areas with intensive biomass combustion activities around large orange-tree plantations. However, the high density of biomass "res could make this emission type a very important source for PM10 in the study area. In the vicinity of the "res the percentage of PM10 over TSP was approx. 50 wt%, whereas the PM2.5 fraction over PM10 reached only 40 wt% (Table 6 and Fig. 7). Measurements of the marine aerosols obtained at different sites of the shoreline in periods with a dominant daytime in-land breeze #ow, showed PM10 levels from 25 to 50 lg m\ of PM10 (on an hourly basis). The percentage of PM10 over TSP was constantly around 85 wt% and the PM2.5 fraction over PM10 ranged from 45 to 75 wt%. Constant levels of 5}8 lg m\ were measured for fractions (0.8 lm (Table 6 and Fig. 7) which coincide with the levels and the grain size distribution obtained for ammonium sulphate phases with the cascade impactor. Measurements were also made in the plume of the petrochemical plant located on a coastal site at the south of the city of CastelloH . PM10 levels were relatively low (approx. 20 lg m\ hourly PM10) compared with the other anthropogenic source. The grain-size distribution was very similar to that of the marine aerosols, with levels of "ne secondary particles similar to those of the background marine measurements (Fig. 7).
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Fig. 7. Selected cases of grain-size distribution of hourly levels of total suspended particles measured in the vicinities of non-ceramic emission sources. Levels in lg m\. See codes in Table 6 and Fig. 3 for location of measurement sites.
Fig. 8. Grain-size distribution of hourly levels of total suspended particles measured in rural-remote (Bartolo Mt.) and semi-urban (Alcora, Onda) background areas. Levels in lg m\. See codes in Table 6 and Fig. 3 for location of measurement sites.
4.4. Grain-size distribution of atmospheric particulates: ambient air measurements One set of measurements was performed following a cross-section from the coastal area towards the ceramic-producing zones during the daytime in-land breeze circulation stage (Table 6). The measurements were performed in background rural and suburban areas and showed a clear trend of an increase in the particulate levels from the coastal area (20 lg PM10 m\ and 15 lg PM2.5 m\) towards the ceramic area (36 lg PM10 m\ and 25 lg PM2.5 m\). The "nest fraction (mainly (0.8 lm sulphate) also followed the same trend (from 8 to 12 lg m\). All the measurements of this crosssection also showed two grain-size modes of around 1.6}3.0 and 5.0}7.5 lm, corresponding to marine aerosols. However, there is a marked trend to increase progressively the 5.0}7.5 lm mode (Fig. 8), probably due to the increase in nitrate levels and primary ceramic particulates towards the ceramic zone. In addition to these
modes, two additional coarse particulate inputs are evident (in the 10}15 and '20 lm) as the ceramic area is approached (Fig. 8). These grain size patterns and levels were also constantly recorded by a number of additional measurements performed at ceramic background sites around L'Alcora and Onda (Table 6 and Fig. 8). The results of the measurements performed on the rural background station of Mt. Bartolo evidenced levels of PM10 around 25 lg m\, of which 1/3 proceed from the ammonium sulphate phases (8 lg m\ in the (0.8 lm fraction). In addition to other possible particulate inputs such as nitrates and crustal particles, the two other modes (2}3 and 5}7.5 lm) identi"ed were coincident with the bi-modal distribution of the marine aerosol (Fig. 8). The presence of relatively high levels of ammonium sulphate at this site during the daytime breeze stage supports the high re-circulation of this secondary phase. In summer, the emission plumes from the ceramic zones are dragged by the nocturnal seaward breeze which
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the seaward transport of pollutants from the ceramic area (Fig. 9). However, the levels of PM1 and PM2.5 did not exhibit major changes during the daily cycle, with the 2.5}10 lm fractions being responsible for the increase in PM10 levels (Fig. 9). Because of the longer transport of pollutants, the increase in the '10 lm fraction registered close to the ceramic emission sources (Onda) was not recorded at the Grau station. The high impact of 2.5}10 lm particles on bulk PM10 levels is also evidenced by the measurements performed at L'Alcora. At this site, high levels of PM25 and PM10 are reached during the daytime stage, when local ceramic emissions are relatively high. At this stage the emission plumes are dragged towards the northwestern areas by the inland breeze circulation. Subsequently, in the nocturnal period, these high particulate air masses travel back to the emission-source area due to the seaward breeze. These processes account for the higher PM10 levels reached during the nocturnal stage with respect to the daytime stage (Fig. 9). Because of the breeze transport and consequent grain-size segregation, nocturnal levels of '10 lm particles are low when compared with the daytime stage. Once more it becomes very evident that the grain-size range which detects the impact of these polluted air masses on the ambient air quality is that of 2.5}10 lm (Fig. 9). The two major PM10 peaks registered between 21}22 and 7}8 h (both local time, see Fig. 9) probably mark the calm periods produced during the change in wind direction between the breeze stages. A similar situation was found at the Onda station where the impact of emission plumes from the nearby ceramic emission sources is not as important as in L'Alcora, but the nocturnal breeze circulation also accounts for high 2.5}10 and '10 lm particulate levels. The PM2.5 levels did not evidence the impact of these plumes at all (Fig. 9). The calm periods between breeze stages are also evidenced in the late evening and early morning by high particulate events (Fig. 9).
Fig. 9. Time evolution of levels of di!erent grain-size fractions of atmospheric particulates in the daily breeze cycle at the Grau, Onda and L'Alcora monitoring stations. Levels in lg m\. The simultaneous wind speed and direction measurements are also included to show the breeze dynamics observed during the measuring period.
accounts for a rise of the nighttime coastal particulate levels. 24 h measurements with semi-hourly particulate levels performed at the Grau station demonstrated that in the daytime stage all grain-size fractions remained at relatively low levels due to the relatively clean marine air mass #ows (see levels of particles and wind velocity and direction in Fig. 9). Later, in the nocturnal stage (21}7 h) the PM10 levels increased drastically as a consequence of
5. Conclusions Although the ceramic primary particulate emissions from the CastelloH area have a coarse grain-size distribution, the particulate transport dominated by the breeze circulation accounts for a subsequent grain-size segregation. Thus, major impacts on the ambient air quality of the coastal area induced by the particulate ceramic emissions occur in the nocturnal period due to the seaward transport of polluted air masses. Levels of ambient air particles increase mainly in the 2.5}10 lm range due to grain-size segregation by transport. The chemical composition of the ceramic particulate emissions is very similar to the crustal end-member but high Al, Fe and Ti levels coupled with a peculiar grain-size distribution in the major insoluble phases
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allows us to identify the ceramic input in the particulate matter. Although replacement of PM10 by PM2.5 measurements in ambient air quality monitoring standards is a likely trend for the future, the PM2.5 is not an adequate parameter for monitoring the impact of primary particulate emissions (such as ceramic emissions) on air quality, since the major particulate ambient air levels are in the range of 2.5}10 lm. As demonstrated from the analysis of major and trace elements in simultaneous PM10 and PM2.5 sampling and cascade impactor and from the Grimm measurements, PM2.5 measurement avoids the interference of crustal particulates without major reduction in the secondary anthropogenic load with the exception of nitrate. However, occasionally industrial primary particulate emissions may have the crustal particulate grain-size, and consequently these emissions will not be detected by PM2.5 measurements. From a technical point of view, the measurement of atmospheric particulates has to be speci"c for monitoring areas with major secondary or primary particulate emissions. In areas characterised by major secondary particulate emissions, PM2.5 monitoring should detect anthropogenic particulate pollutants without crustal particulate interference, whereas PM10 measurements should be used in areas with major primary anthropogenic particulate emissions. Acknowledgements The present study has been supported by the Plan Nacional de I#D of the Spanish CICYT, project AMB98-1044, and by the Spanish Ministry of the Environment. We would like to express our gratitude to the DireccioH General de EducacioH i Qualitat Ambiental of the Generalitat Valenciana for supplying the data from the monitoring stations and for their interest in the development of this study. References Dockery, D., Pope, A., 1996. Epidemiology of acute health e!ects: summary of time-series studies. In: Wilson, R.,
Spengler, J.D. (Eds.), Particles in Air: Concentration and Health E!ects. Harvard University Press, Cambridge, USA, pp. 123}147. EU Directive 1999/30/EC, 1999. Council directive relating to limit values for sulphur dioxide, nitrogen dioxide and oxide of nitrogen, particulate matter and lead in ambient air. The Council of the European Union. Harrison, R.M., Pio, C., 1983. Size di!erentiated composition of inorganic aerosol of both marine and polluted continental origin. Atmospheric Environment 17, 1733}1738. Harrison, R.M., Kito, A.M.N., 1990. Field inter-comparison of "lter pack and denuder sampling methods for reactive gaseous and particulate pollutants. Atmospheric Environment 24A, 2633}2640. IPCC, 1996. Climate change. In: Houghton, J.T., Meira Filho, L.G., Callander, B.A., Harris, N., Kattenberg, A., Maskell, K. (Eds.), The Science of Climate Change. Cambridge University Press, Cambridge, UK, 584pp. Kiehl, J.T., Rhode, H., 1995. Modelling geographical and seasonal forcing due to aerosols. In: Charlson, R.J., Heintzenberg, J. (Eds.), Aerosol Forcing of Climate. Wiley, New York, pp. 281}296. Mildford, J.B., Davidson, C.I., 1987. The sizes of particulate sulphate and nitrate in the atmosphere: a review. Journal of Air Pollution Control Association 37 (2), 125}134. MillaH n, M.M., Artin ano, B., Alonso, L., Navazo, M., 1991. The e!ect of meso-scale #ows on regional and long-range atmospheric transport in the Western Mediterranean area. Atmospheric Environment 25A (5/6), 949}963. MillaH n, M.M., Salvador, R., Mantilla, E., 1997. Photooxidant dynamics in the Mediterranean basin in summer: results from European research projects. Journal of Geophysical Research 102 (D7), 8811}8823. Querol, X., Alastuey, A., Puicercus, J.A., Mantilla, E., Ruiz, C.R., LoH pez-Soler, A., Plana, F., Juan, R., 1998. Seasonal evolution of suspended particles around a large coal-"red power station: chemical characterisation. Atmospheric Environment 32 (11), 719}731. US-EPA, 1987. Second addendum to air quality criteria for particulate matter and sulfur oxides (1982): assessment of newly available health e!ects information. Research Triangle Park, EPA Report 600/8-86-020F, NTIS PB87-176574. US-EPA, 1996. Air quality criteria for particulate matter. EPA/600/P-95/001F, US Environmental Protection Agency, Washington, DC. Wall, S.M., John, W., Ondo, J.L., 1988. Measurement of aerosol size distribution for nitrate and major ionic species. Atmospheric Environment 22, 1649}1656.