eology 71 (2007) 122–128www.elsevier.com/locate/ijcoalgeo

International Journal of Coal G

The identification of metallic elements in airborne particulate matterderived from fossil fuels at Puertollano, Spain

Teresa Moreno a,⁎, Andrés Alastuey a, Xavier Querol a, Oriol Font a, Wes Gibbons b

a Institute of Earth Sciences “Jaume Almera”, CSIC, C/Lluis Solé i Sabarís s/n, Barcelona 08028, Spainb AP 23075, Barcelona 08080, Spain

Received 9 May 2006; received in revised form 31 July 2006; accepted 6 August 2006Available online 12 September 2006

Abstract

Puertollano is the largest industrial centre in central Spain, and includes fossil fuel burning power plants as well aspetrochemical and fertilizer complexes. The coal-fired power plants use locally mined coal from extensive coal deposits whichcontinue to be exploited and used locally. The coal deposits have a distinctive geochemistry, being particularly enriched in Sb andPb, as well as several other metals/metalloids that include Zn and As. ICP-AES and ICP-MS chemical analysis of particulate mattersamples (both PM10 and PM2.5) collected at Puertollano over a 57-week period in 2004–2005 reveals enhanced levels of severalmetallic trace elements, especially in the finer (PM2.5) aerosol fraction. Factor analysis applied to the data indicates that at leastsome of these metallic elements are likely to originate from hydrocarbon combustion: Sb and Pb are markers linked to the localcoals, whereas V and Ni are, at least in the finer (PM2.5) fraction, likely associated with other anthropogenic sources. Other factorsmeasured are related to natural sources such as crustal/mineral and sea spray particles. Our study provides an example of howchemical analysis of large numbers of ambient PM samples, combined with statistical factor analysis and coal geochemistry, canreveal airborne emissions from the combustion of specifically identifiable fuels.© 2006 Elsevier B.V. All rights reserved.

Keywords: PM10; PM2.5; Metals; Coal; Source apportionment; Puertollano

1. Introduction

Puertollano lies some 220km south of Madrid andhas been an important coal mining town since 1873,currently supplying coal to two local power stations.The town is these days equally well known for its majorpetrochemical complex (Repsol Petróleo and RepsolQuímica) and fertilizer works (Fertiberia). Theseindustrial plants lie south and east of the main town inrelatively low ground within the broad Alcudia Valley(Fig. 1), confined by a prominent line of hills to the

⁎ Corresponding author. Tel.: +34 934095410; fax: +34 934110012.E-mail address: tmoreno@ija.csic.es (T. Moreno).

0166-5162/$ - see front matter © 2006 Elsevier B.V. All rights reserved.doi:10.1016/j.coal.2006.08.001

north and the Sierra Morena to the south which renderthe area vulnerable to atmospheric inversions andrelated pollution episodes (Moreno et al., 2005).

The coal mine supplies raw materials to two nearbypower stations, one of which is the largest integratedgasification combined-cycle (IGCC) plant in the world,operated by Elcogas and utilising a 50:50 mixture oflocal high volatile bituminous coal and petcoke manu-factured at the nearby petrochemical plant. The otherplant, operated by Viesgo, uses conventional pulverisedcoal combustion (PCC), and is fed with only local coal.Other than heavy industry, additional sources of localemissions are provided by traffic (although there are nomajor roads nearby so these are relatively minor) and

Fig. 1. Location of Puertollano, the sampling site, and local industry (modified from Moreno et al., 2006a).

123T. Moreno et al. / International Journal of Coal Geology 71 (2007) 122–128

domestic heating (with wood, coal or oil). In this paperwe report on trace element chemical data from airborneparticulate matter <10 μm and <2.5 μm in size (PM10

and PM2.5) collected at Puertollano over a 57-weekperiod during 2004–2005. We illustrate how study of thetrace element chemistry of these airborne dusts, combinedwith factor analysis, reveals a recognisable signaturefrom fossil fuel combustion in a large industrial site.

2. Geological setting and coal geochemistry

The Puertollano coals occur in one of the youngest ofseveral late Variscan post-orogenic intermontane sedi-mentary basins in southern Iberia that were receiving

Fig. 2. Concentrations of trace elements in Puertollano coals (Alastuey etMcLennan, 1995), compared with values from a compositional range for wo

sediments during Stephanian to possibly Autunian times(Wallis, 1985; Wagner, 1985, 1989; Jiménez et al.,1999; Colmenero et al., 2002). The coal seams occurinterbedded with a mainly argillaceous successiondeposited within sedimentary environments that includ-ed coal swamp, lacustrine, deltaic, fluvial, and probablyat times transitional marine conditions (Soler-Gijón,1991; Jiménez et al., 1999). The sequence begins withalluvial fan breccias interlayered with rhyodaciticvolcaniclastic deposits and unconformably overlyingan Early Palaeozoic basement. The coarse grained basalsuccession grades upward into finer kaolinitic argilla-ceous rocks which contain three major oil shale bedsdeposited under oxygen-depleted conditions in a

al., 2001) normalised to upper continental crust values (Taylor andrldwide coals (Swaine, 1990).

124 T. Moreno et al. / International Journal of Coal Geology 71 (2007) 122–128

Stephanian lake (Kruge and Suarez-Ruiz, 1991; Borregoet al., 1992; del Río et al., 1993, 1994). The coal seamslie still higher in the sequence and, like the sedimentswithin which they lie, contain a relatively high volcanicash content. The remains of lycopsids are consistentwith a lake margin/low energy flood plain environment(DiMichele and Phillips, 1994).

The presence of significant amounts of volcanicmaterial, as well as weathered detritus from theunderlying and surrounding basement, and the isolatedsetting of this sedimentary basin, created a distinctivediagenetic environment which is reflected in the coalgeochemistry. In particular, as Alastuey et al. (2001)have demonstrated, the Puertollano coals are unusuallyrich in Si and several metallic elements. Fig. 2 illustratesthis by comparing trace element concentrations inPuertollano coals (Alastuey et al., 2001) againstconcentrations in upper continental crust (Taylor andMcLennan, 1995). The mean trace element concentra-tions (bulk coal dry basis) in Puertollano coals shownotable enrichments in Zn (234ppm), Ge (19ppm), As(25ppm), Sb (44ppm), Pb (185ppm) and Cs (16ppm).The same figure also plots the average range of traceelement compositions of coals worldwide (Swaine,1990), illustrating an enrichment in most trace elementsin Puertollano. The trace elements that really stand outas exceptionally enriched are Pb and Sb.

3. Methodology

The air pollution recording station used for this study(Campo de Fútbol de Repsol: 04°05′19″W, 38°41′64″N, 708m a.s.l.) is sited in the entrance of a formerfootball ground in suburbs to the SE of the Puertollanotown centre, WNW of the petrochemical works and theIGCC power station, and NNE of the coal mine and thePCC power station (Fig. 1). 24h sampling was carriedout by means of two MCV CAV-A high volumesamplers (30m3/h) equipped with PM10 and PM2.5

inlets and quartz fibre filters (QF20 Schleicher andSchuell). A total of 110 and 111 filters (PM10 and PM2.5

respectively) were collected from the 22nd of January2004 to the 1st of March 2005 for physicochemicalcharacterisation in Puertollano, at an average rate of 2samples per week. Filters were treated and analyzed fordetermining the levels of major and trace componentsfollowing the procedure of Querol et al. (2001) andRodríguez et al. (2002). This is based on the dailysampling of PM and subsequent analysis of major andtrace elements by ICP-AES and ICP-MS (of acidicdigestions of 1/2 of each filter), soluble anions andcations by ion chromatography, ammonium by color-

imetry-FIA and carbon by thermo-optical methods.Sample collection was performed immediately afterfinishing the sampling sequence to avoid the loss ofsemi-volatile compounds. We are aware of the possiblesampling artifacts regarding the potential loss of certainreactive species as well as the positive artifact arisingfrom the potential fixation of volatile species that maytake place using the EU reference PM10 samplingprocedure. However, we carried out the study followingthis procedure to quantitatively determine the differentsource contributions to PM levels with the measurementprocedure used in the air quality monitoring networks inthe EU. Blank field filters were used for every stockpurchased for sampling and analyzed in the samebatches of their respective filter samples. The cor-responding blank concentrations were subtracted foreach sample. For analysis control, reference materialNIST 1633b was added to a fraction of a blank filter tocheck the accuracy of the analysis of the acidicdigestions. For most elements, relative analytical errorswere 10%, with exception of P and K for which a 15%error was determined. This methodology was success-fully tested for the analysis of city dust in an IEA roundrobin exercise.

A varimax rotated factor analysis was also performedto identify the main sources affecting the PM compo-sition at each sampling site. Chemical species of knownorigin are frequently used as source tracers. Principalcomponent analysis (PCA) was applied to obtain suchemission sources (factors), in our analyses accountingfor at least 75% of the variance of the dataset. Thequantitative determinations of the source contributionswere based on multilinear regression analysis (MLRA),in which the bulk PM concentration was used as adependent variable, and the absolute factor score matrixcontained the independent variables. The factors witheigenvalues greater than one were extracted andidentified as particle sources, based on the interpretationof their loadings.

4. Results

Table 1 presents the maximum, minimum and meanconcentrations (in ng/m3) of 20 trace elements in thePM10 and PM2.5 samples collected over the study periodand Fig. 3 compares these concentrations with thoserecorded from five other towns in Spain (Burgos:suburban; Badajoz: urban; Huelva and Tarragona:urban–industrial; Barcelona: urban traffic) (Querol etal., 2004). It can be seen from this figure that averagelevels of airborne trace element-bearing particles atPuertollano mostly lay within the typical range for

Table 1Average, maximum and minimum values of specific trace elements in the PM10 and PM2.5 samples from Puertollano, indicating the PM2.5/PM10 ratiofor each element

ng/m3 PM10 PM2.5 PM2.5/PM10

Avg. Max. Min. Stdev Avg. Max. Min. Stdev Avg. Max. Stdev

Li 1.0 5.1 <0.01 0.9 0.3 0.9 <0.01 0.2 0.25 3.4 0.5P 32.6 104.8 <0.01 24.0 10.3 73.3 <0.01 13.1 0.32 9.5 1.4Ti 62.0 268.1 2.2 54.0 12.4 60.7 <0.01 12.8 0.20 0.5 0.1V 9.8 59.1 0.4 10.1 5.5 31.1 0.1 6.2 0.56 1.0 0.2Cr 3.5 11.0 <0.01 2.0 1.5 4.5 <0.01 1.2 0.44 2.9 0.6Mn 11.3 42.1 0.7 8.6 3.2 15.9 <0.01 2.8 0.28 1.5 0.2Co 0.8 5.3 0.1 0.8 0.3 1.8 <0.01 0.3 0.36 1.7 0.3Ni 4.1 17.5 <0.01 3.8 3.0 12.5 <0.01 2.3 0.72 6.7 1.2Cu 26.5 179.7 <0.01 23.0 12.2 91.8 <0.01 15.8 0.46 0.9 0.2Zn 53.9 457.5 8.0 71.6 30.1 184.6 5.5 27.1 0.56 1.9 0.4As 1.9 57.1 0.2 7.0 1.0 26.1 <0.01 3.4 0.53 1.3 0.2Se 0.6 2.3 <0.01 0.5 0.4 2.5 <0.01 0.6 0.74 9.5 1.5Rb 1.5 6.8 0.2 1.2 0.5 1.8 0.09 0.3 0.29 1.0 0.2Sr 4.6 37.4 0.3 4.5 0.8 7.1 <0.01 1.0 0.18 0.8 0.1Mo 3.0 23.7 <0.01 4.0 2.0 20.4 <0.01 3.6 0.67 2.6 0.6Cd 0.1 0.5 <0.01 0.1 0.1 0.4 <0.01 0.1 0.71 3.7 0.7Sb 4.2 123.9 0.3 12.8 3.2 114.0 0.1 12.3 0.76 0.9 0.2Ba 12.8 57.9 <0.01 9.2 5.0 29.0 <0.01 5.0 0.39 2.3 0.4La 0.9 4.8 0.1 0.8 0.3 1.5 <0.01 0.3 0.30 0.6 0.1Ce 1.2 5.1 0.1 1.0 0.3 1.2 <0.01 0.2 0.25 1.2 0.2Pb 12.0 121.9 1.3 14.0 9.3 109.1 0.8 13.2 0.78 1.0 0.2

Avg.: Average values; Max. and Min.: Maximum and Minimum values respectively; Stdev: Standard deviation.

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Spanish cities. Given the amount of heavy industrybased in Puertollano, a relatively small town (c.50000inhabitants), it is not surprising to note higher thanaverage levels of metals and metalloids such as Ti, V, Cr,Co, Ni, Zn, As, and Sb, although none of these elementsare present in exceptional amounts.

Results from the factor analysis indicate the presenceof five main element groupings in the PM10. Two of

Fig. 3. Concentrations (ng/m3) of selected trace elements in Puertollano comonitoring sites in five Spanish cities: Huelva, Badajoz, Burgos, Tarragona,

these are background populations of dusts (naturalsources), one being silicate-rich and derived from theerosion of rocks and soils, and the other of lessimportance being sea spray (Cl−, Na+ and Mg2+). Thethree remaining groups are shown in Table 2 and are allfrom anthropogenic sources, one being characterised byammonium sulphates and nitrates associated with VandNi (Source 2 in Table 2). The other two groups are

mpared with the range of these elements recorded from air pollutionand Barcelona (Querol et al., 2004).

Table 2Principal component analysis results for Puertollano PM10 samples

PM10 PM2.5

Source 1 Source 2 Source 3 Source 1 Source 2

Coal Industrial 1 Industrial 2 Coal Industrial 1

Sb 0.93 NH4+ 0.93 Ni 0.67 Sb 0.90 SO4

2− 0.90Pb 0.89 SO4

2− 0.84 V 0.67 Pb 0.87 NH4+ 0.80

As 0.70 NO3− 0.80 Co 0.62 Zn 0.79 Ni 0.77

Zn 0.62 PM10 0.74 Zn 0.56 Co 0.72 V 0.75Co 0.53 OM-EC 0.67 As 0.69 PM2.5 0.69

Ni 0.58 Cl 0.61 NO3− 0.50

V 0.52% Var.=9 % Var.=5 % Var.=4 % Var.=11 % Var.=35

Components with a loading factor<0.50 are excluded. OM-EC: organic matter and elemental carbon.

126 T. Moreno et al. / International Journal of Coal Geology 71 (2007) 122–128

metalliferous, one linking Sb with Pb (Source 1 in Table2), and the other again V with Ni but without the link tosulphates and nitrates (Source 3 in Table 2). Whereasboth Sources 1 and 2 are also clearly identifiable in thePM2.5 fraction, Source 3 is not, indicating the presenceof this association only within the coarser aerosolfraction.

Fig. 4 plots average concentrations of four represen-tative trace metals/metalloids (Sb, Pb, V, Rb) normalisedto upper continental crust (UCC) (Taylor and McLen-nan, 1995) to illustrate some of the similarities anddifferences in trace element groupings in airborne PM atPuertollano. On the same diagram we plot averagedconcentrations of these elements in the local coal andpetroleum coke (Alastuey et al., 2001), a by-productfrom the local refinery. Sb has been selected because of

Fig. 4. Sb, Pb, V and Rb concentrations normalised to upper continental crucompared with compositions of these elements in local coal and petcoke (Alaline (see right-hand scale).

all the trace elements analyzed it shows the mostextreme enrichment compared to UCC. With a PM2.5/10

ratio of 0.7, majority of the Sb is present in the finer PMfraction, an observation consistent with a derivationfrom combustion processes (Miravet et al., 2006). Incontrast to Sb, Pb is less enriched overall, with averagePb levels in Puertollano coals showing similar normal-ised UCC abundances to our PM samples. Whereas bothcoal and PM10 contain Pb concentrations only a littlelower than UCC, petcoke is strongly depleted. As withSb, Pb shows high PM2.5/10 ratios, again illustrating thestrong preference of this element for the finer fractionand a likely origin as combustion-related secondary orfine primary particles. Such preference has also beenobserved in other particles emitted from coal-firedpower plants (Goodarzi, 2006).

st (Taylor and McLennan, 1995) for the PM10 and PM2.5 samples andstuey et al., 2001, left scale). PM2.5/PM10 ratios are shown as thick grey

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The transition metal V show contrasting distributionpatterns to Pb: whereas it is relatively enriched in thepetcoke, which shows similar concentrations to thePM10, it is strongly depleted in the coal (Fig. 4). ThePM2.5/10 ratio is above 0.5, again showing a likelyanthropogenic source. Finally, in contrast to the otherthree metals, Rb is plotted in Fig. 4 to represent the largeion lithophile elements (cf. Sr and Ba) which in all casesshow strong depletion with respect to average UCC.Once exposed at the earth's surface LILEs tend to bemore soluble, and therefore more easily removed fromtheir host minerals, i.e. more mobile and susceptible tochemical weathering (Moreno et al., 2006b). The PM2.5/

10 ratio for Rb is low, (0.3), indicating preferentialaccumulation in the coarser PM10 fraction. Rb usuallyoccurs in nature as a trace element within rock formingminerals such as alkali feldspar, mica and clay minerals,and thus has an affinity for the silicate-rich “crustal”component of PM which is always more abundant in thecoarser dust fraction (e.g. Paoletti et al., 2002; Ho et al.,2003; Moreno et al., 2003).

5. Discussion and conclusions

The unusual nature of Puertollano coal geochemistryallows the detection of its chemical signature in thesamples of airborne particulate matter. The markedenrichment of the Puertollano coals in Pb and Sb makesthese two elements especially useful markers andpathfinders. As Table 2 illustrates, this likely “coalcomponent” is present in both PM10 and PM2.5

fractions, along with an association between theseelements and As and Zn which further emphasises thecommon nature of their origin.

In contrast, the association of V and Ni revealed bythe factor analysis appear to have little to do with thelocal coal (Fig. 4), and V is relatively depleted in thePuertollano coals. Petrochemical refineries, on the otherhand, are known sources of Vand Ni emissions (Kuik etal., 1993; Rodríguez et al., 2004; Bosco et al., 2005). Inthe case of the finer fraction (PM2.5), where these metalsare associated with ammonium sulphate and nitrate, alink with the refinery seems reasonable, although anorigin linked to the fertilizer plant is also plausible asammonium sulphate and nitrate are present in agricul-tural fertilizers. With respect to the PM10, however, sucha direct sourcing from refinery emissions is lessobvious: the two metals are statistically linked neitherto sulphate nor nitrate (see Source 3 in Table 2). Onepossibility is that the particles are derived possibly fromthe petcoke, which has the necessary prerequisiteelevated V and Ni content. However, the preference

for the coarser PM10 particle fraction and the cleanburnefficiency of the IGCC plant, which burns 50:50 coalmixed with petcoke, make a gasification origin fromheavy industry unlikely. A more feasible alternativemight be to look for sources of fugitive dust (such asfeed stocks) derived from the petcoke or some similarmaterial.

To conclude, the results of this study show that it ispossible to use elemental concentrations in feed coals asmarkers, along with the statistical analysis of thechemistry of inhalable PM bulk samples, to identifylikely atmospheric contamination sources. This isparticularly relevant for the more toxic elements suchas some trace metals and metalloids. At Puertollanoduring the 2004–2005 study period, atmospheric annualaverage concentrations of metals regulated by EuropeanUnion limit (500ng/m3 Pb, 1999/30/CE) and target (6,20 and 5ng/m3 for As, Ni and Cd, 2004/107/CE) valueswere significantly below those levels (Table 1). Withinthese low ranges the average levels of 12 and 4.2ng/m3

of Pb and Sb respectively in PM10, and 9.3 and 3.2ng/m3

of Pb and Sb in PM2.5 are mostly linked to thecombustion of local coals. Our results offer a steptowards identifying and reducing the primary sources ofsuch pollution.

Acknowledgements

This study has been financially supported by theSpanish Ministry of the Environment and by theMinistry of Education and Science (CGL2004–05984-C07–02/CLI). The authors are indebted to the Depart-ment of the Environment of the Castilla La ManchaGovernment for their collaboration, and thank the editorand two referees for their detailed comments on themanuscript.

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