The Science of the Total Environment 300(2002) 229–243

0048-9697/02/$ - see front matter� 2002 Elsevier Science B.V. All rights reserved.PII: S0048-9697Ž02.00273-5

Heavy metals in urban soils: a case study from the city ofPalermo(Sicily), Italy

Daniela Salvagio Manta , Massimo Angelone , Adriana Bellanca *, Rodolfo Neri ,a b a, a

Mario Sprovieria

Dipartimento di Chimica e Fisica della Terra (C.F.T.A), Universita di Palermo, Via Archirafi 36, 90123-Palermo, Italya `ENEA, AMB TEIN CHIM, C.R. Casaccia, S.P. Anguillarese Km 1.200, 00060-Rome, Italyb

Received 25 January 2002; accepted 11 June 2002

Abstract

Concentrations of V, Mn, Cd, Zn, Ni, Cr, Co, Cu, Pb, Hg and Sb were measured on 70 topsoil samples collectedfrom green areas and parks in the city of Palermo(Sicily) in order to: (1) assess the distribution of these heavymetals in the urban environment;(2) discriminate natural and anthropic contributions; and(3) identify possiblesources of pollution. Mineralogy, physico-chemical parameters, and major element contents of the topsoils weredetermined to highlight the influence of ‘natural’ features on the heavy metal concentrations and their distribution.Medians of Pb, Zn, Cu and Hg concentrations of the investigated urban soils are 202, 138, 63 and 0.68 mg kg ,y1

respectively. These values are higher, in some case by different orders of size, than those of unpolluted soils in Sicilythat average 44, 122, 34 and 0.07 mg kg . An ensemble of basic and multivariate statistical analyses(clustery1

analysis and principal component analysis) was performed to reduce the multidimensional space of variables andsamples, thus defining two sets of heavy metals as tracers of natural and anthropic influences. Results demonstratethat Pb, Zn, Cu, Sb and Hg can be inferred to be tracers of anthropic pollution, whereas Mn, Ni, Co, Cr, V and Cdwere interpreted to be mainly inherited from parent materials. Maps of pollutant distribution were constructed for thewhole urban area pointing to vehicle traffic as the main source of diffuse pollution and also showing the contributionof point sources of pollution to urban topsoils.� 2002 Elsevier Science B.V. All rights reserved.

Keywords: Urban soils; Heavy metals; Soil pollution; Geostatistics

1. Introduction

Heavy metals in urban soils have been shownto be very useful tracers of environmental pollution(e.g. Davies and Houghton, 1984; Albasel andCottenie, 1985; Burguera et al., 1988; Bacon etal., 1992; Kelly et al., 1996).

*Corresponding author. Tel.:q39-091-6161574; fax:q39-091-6168376.

E-mail address: bellanca@unipa.it(A. Bellanca).

Urban soils are known to have peculiar charac-teristics such as unpredictable layering, poor struc-ture, and high concentrations of trace elements(Kabata-Pendias and Pendias, 1992; Tiller, 1992).They are the ‘recipients’ of large amounts of heavymetals from a variety of sources including indus-trial wastes, vehicle emissions, coal burning waste,and other activities. In areas where public gardensand parks are exposed to significant pollution

230 D.S. Manta et al. / The Science of the Total Environment 300 (2002) 229–243

Fig. 1. Map of the Palermo city(Sicily) with location of sam-pling sites of topsoils(solid circles), calcarenitic bedrocks(open squares), and cemented detritus(solid square).

levels, dust from the ground may have toxic effectsas a consequence of inhalation or ingestion byhumans, particularly children, which poses majorhealth hazards(Culbard et al., 1988; Folinsbee,1993; Sanchez-Camazano et al., 1994). Further-´more, any contamination of urban soils could causein turn groundwater contamination because metalsof the polluted soils tend to be more mobile thanthose of unpolluted ones(Steinmann and Stille,1997; Wilcke et al., 1998).Although a geographically widespread dataset

has been generated from the analysis of urbansoils, many from a single city(Farmer and Lyon,1977; Davies et al., 1987; Sanchez-Camazano et´al., 1994, Strnad et al., 1994; Markus and Mc-Bratney, 1996) or from urban agglomerations with-in a country (Carey et al., 1980; Culbard et al.,1988; Tiller, 1992), some from Italy(Facchetti etal., 1982; Bini et al., 1984; Ferretti et al., 1991;Angelone et al., 1995, 1999) and none from Sicily,concentrations of some toxic elements(e.g. Hg,Sb and V) remain poorly documented. Mercury isone of the important pollutants and it is inferredto dramatically accumulate in different environ-ments due to recent human activity. Most scientificpapers deal with Hg contamination of waters orsediments, mainly as reflection of mining andsmelting activities(Guerzoni et al., 1984; Covelliet al., 2001). Antimony and, to a certain extent,vanadium are inferred to potentially cause healthproblems when people are exposed to their rela-tively high levels. These metals have been increas-ingly entering the urban environment during recentyears coming from industrial dust and burning fueloils.In this study, we start with a general character-

ization of bulk mineralogy and geochemistry oftopsoils from the city of Palermo. Then, the con-centration data for 11 heavy metals(Pb, Hg, Cu,Cr, Zn, Sb, Mn, V, Co, Ni and Cd) are presentedand discussed. In order to highlight the extent andseverity of contamination, we take advantage ofthe availability of a dataset deriving from theanalysis of ‘natural’ soils in Sicily(Bellanca etal., 1996; Palumbo et al., 2000). Basic and multi-variate statistical procedures were used to identifyheavy metal sources and discriminate natural and

anthropic contributions as well as point and non-point sources of contamination.

2. Materials and sampling strategy

A total of 70 non-stratified topsoil samples(depths0–10 cm) were collected from green areasand public parks within the city of Palermo(Fig.1). Sampling sites were selected where the lasthuman perturbations go back to at least 10 yearsago and where chemicals(such as fertilizers,pesticides) and sewage sludges have not been used.To avoid effects due to the differential uptake ofmetals by vegetation, sampling was carried outwhere plants with superficial roots are not present.At each sampling point, three sub-samples, with a20=20 cm surface, were taken and then mixed toobtain a bulk sample. Such a sampling strategywas adopted in order to reduce the possibility ofrandom influence of urban waste not clearly visi-ble. All the samples were collected with a stainlesssteel spatula and kept in PVC packages, at roomtemperature, for not more than 12 h before startinganalytical procedures.

231D.S. Manta et al. / The Science of the Total Environment 300 (2002) 229–243

Soils in the city of Palermo are developed onPleistocene calcarenites or recent alluvial sedi-ments derived from the erosion of calcareousmountains surrounding the city. Locally, the soilshave received in the past some contribution fromTerra Rossa soils of the neighboring country. Todefine the lithologic imprint on the geochemicalcomposition of the urban soils, five calcarenitesamples were collected from different sites inPalermo and from the Monte Gallo hill(NW ofthe city); one sample of cemented detritus wastaken from the Favorita Park(Fig. 1).

3. Analytical methods

The soil samples were air-dried for approxi-mately 24 h and sieved through a 2-mm sieve.The samples were analyzed for pH, cationexchange capacity(CEC) and organic matter con-tents. Values of pH were measured in H O and in2

1 M KCl solution with a soilysolution ratio of1:25, using a Metrohn 691 with a glass electrodeAC 9101. CEC was determined in a 10%Ba(CH COO)xH O and 0.1 N MgSO extracting3 2 4

solutions(Gazzetta Ufficiale, 1992). Organic mat-ter contents were determined by soil ignition at atemperature of 4508C (Allen et al., 1974).Soil mineralogy was investigated by powder X-

ray diffraction (XRD, Philips PW1729 apparatus)using CuKa radiation filtered by Ni. The relativeproportions of minerals were determined accordingto methods and data of Schultz(1964), Barahonaet al. (1982).CaCO contents were measured by means of a3

classic gas-volumetric technique as reported inHusselmann(1966).The major element concentrations were deter-

mined by X-ray fluorescence spectrometry(XRF,Philips PW1400 apparatus), on bulk-samplepressed, boric-acid backed pellets. X-Ray countswere converted into concentrations by a computerprogram based on the matrix correction methodaccording to Franzini et al.(1975). The accuracyof determinations was checked by using certifiedreference materials. Analytical errors were below1% for Si, Al, Na, below 3% for Ti, K, Fe, Caand below 10% for Mg and P.

‘Pseudo-total metal contents’ were obtained bydigesting soil samples with aqua regia in bombsusing a microwave oven(CEM MSD 2000 equip-ment). The term ‘pseudo-total’ accounts for theaqua regia digestion not completely destroyingsilicates. This method is widely used in environ-mental geochemistry studies and recommended bythe National Government regulation.Mn, Cr, Ni, Co, Cu, Zn, Pb and Cd concentra-

tions were measured by atomic absorption spectro-photometry coupled with a graphite furnace(GF-AAS) using a 5100 Perkin–Elmer instrument.The elements Sb and V were determined byinductively coupled plasma mass spectrometry(ICP-MS) using an ELAN 6000 Perkin–Elmer.All calibration standards were prepared in the sameacid matrix used for the soil samples. Caution wasused in preparing and analyzing samples to mini-mize contamination from air, glassware and rea-gents, which were all of Suprapur quality.Replicated measures of international referencematerials (IAEA SOIL 5 and SOIL 7), reagentblanks, and duplicated soil samples(approx. 20%of the total number of soil samples was used forthis purpose) randomly selected from the set ofavailable samples were used to assess contamina-tion and precision. The analytical precision, meas-ured as relative standard deviation, was routinelybetween 5 and 6%, and never higher than 10%.Mercury concentrations were determined by

Direct Mercury Analyzer-80(DMA-80). Accuracyof analyses was checked using an international soilstandard(Best-1) and duplicate samples. The qual-ity control gave good precision(S.D.-5%) for allsamples.

4. Results and discussion

4.1. Physico-chemical parameters

The main physico-chemical parameters deter-mined for urban topsoils from Palermo include:(i) organic matter contents ranging from 3 to 25%,with most values approximately 6%;(ii) values ofpH ranging in a narrow interval(7.2–8.3), whichsuggests neutral to sub-alkaline conditions for allthe topsoils; and(iii ) cation exchange capacity(CEC) showing a very broad interval of variation,

232 D.S. Manta et al. / The Science of the Total Environment 300 (2002) 229–243

from 5 to 56 meqy100 g, with a mean value of 26meqy100 g comparable to that of soils fromtemperate regions(Wilcke et al., 1998).CaCO contents of the analyzed soils vary from3

7 to 67%, with an average value of 32% andlowest percentages for the Favorita Park samples.

4.2. Soil mineralogy

The topsoil mineralogy is dominated by carbon-ates(calcite and dolomite), alumino-silicates(clayminerals and feldspars) and quartz. Most samplesare characterized by high contents of carbonatephases()50%) while the soils from the FavoritaPark(FP) are dominated by silicate phases(mainlyclay minerals and quartz).

4.3. Major element composition

The bulk-soil major element composition ofmost samples is defined by CaOqMgO rangingfrom 15 to 65%, SiO varying between 25 and2

60%, and Al OqFe O ranging from 7 to 35%.2 3 2 3

Samples of the Favorita Park exhibit higher con-centrations of SiO , with a mean value of 60%.2

The investigated soils show chemical imprints ofboth calcarenite bedrocks and local Terra Rossasoils. This may be accounted for urban soils ofPalermo received in the past some contributionfrom Terra Rossa soils and supports the utilizationof heavy metal concentrations of these soils asbackground levels to estimate urban soilcontamination.

4.4. ‘Pseudo-total’ metal contents

Concentrations of Hg, Pb, Zn, Cu, Cd, Cr, Co,Ni, V, Sb and Mn in urban soils and bedrocks ofPalermo are listed in Table 1 together with medianvalues, standard deviations and variability ranges.Median values are given for the sites where moresamples were analyzed. Because of its anomalous-ly high heavy metal contents, sample PF11 wasconsidered as an outlier of the total dataset. Forcomparison mean values for natural soils of Sicily(Bellanca et al., 1996; Palumbo et al., 2000) andranges of variability of the same metals for unpol-luted soils estimated at world scale by Fergusson

(1990), Kabata-Pendias and Pendias(1992) arereported in the same table.The results demonstrate a general enrichment of

heavy metals in the topsoils with respect tobedrocks.Mercury, Pb, Zn, Cu and Sb concentrations are

higher for topsoils compared to their levels inunpolluted soils(at a world-scale) and in naturalsoils of Sicily. High concentrations coupled withhigh standard deviation values suggest anthropo-genic sources for these elements.Generally, the recorded V levels are similar to

those reported for unpolluted soils, although somesamples seem to be anomalously enriched in thiselement.Cobalt, Cr, Ni and Mn concentrations exhibit

generally low levels, close to those reported forunpolluted soils. Moreover, these metals displayquite homogeneous distributions across the cityand therefore lower standard deviations, thus sug-gesting a major natural(i.e. indigenous lithologic)source.Cd and Mn values in the analyzed samples are

comparable to the higher terms reported for naturalsoils worldwide (Table 1). High Cd and Mnconcentrations(greater than 1 and 500 mg kg ,y1

respectively) were measured in some soils fromthe Favorita Park and other green areas of the city.However, it is noteworthy that these values agreewith those of natural soils in Sicily and that of theFP rock sample collected in the Favorita Park.Compared to average concentrations in urban

soils in the world(Table 2), the median values ofPb in the analyzed soils are much lower than thosereported for samples from some large andyorindustrialized cities(i.e. Boston, central Madrid,central London), but they are similar to thosemeasured in smaller cities(i.e. Hamburg, Glas-gow) and residential areas of London(LondonBorough). Copper, Cr, Co, Zn, V and Ni concen-trations are generally similar to those reported forother cities, while Mn contents are generally high-er. Records for Hg and Sb levels in urban soils arescarce in the literature.Inter-element relationships provide interesting

information on heavy metal sources and pathways.Pb is best correlated with Hg(r s0.7) and well2

with Zn, Cu and Sb(r s0.6), which could indi-2

233D

.S.M

antaet

al./

The

Scienceof

theTotal

Environm

ent300

(2002)229–243

Table 1Concentrations(mg kg ) of heavy metals in topsoils and bedrocks from the urban area of Palermo listed together with median values, upper and lower quartiles,y1

and standard deviations

Sample Hg Pb Zn Cu Cd Cr Co Ni V Sb Mn

Soils (ppm)VT1 1.00 249 200 109 0.53 34 4.4 16.0 57 3.4 403VT2 1.57 256 156 87 0.62 27 5.1 14.9 50 4.7 416VT3 0.76 319 318 86 1.86 28 4.2 15.5 48 4.5 429VT4 0.37 261 128 48 0.66 19 2.3 18.3 35 4.5 329VT5 1.10 267 150 74 0.68 29 4.0 17.7 62 3.1 519VT6 1.48 398 264 71 0.81 39 5.7 25.3 62 3.3 564VT7 0.61 186 104 61 0.62 18 2.5 12.0 38 2.1 312VT8 0.72 248 156 57 1.31 33 4.5 19.5 60 2.9 494VT9 0.62 239 184 56 0.68 29 3.4 18.1 52 3.6 358VT10 0.11 178 134 45 0.81 15 1.5 9.1 21 2.0 142VT11 1.16 243 136 78 0.65 29 4.1 17.6 58 2.1 544VT12 0.08 150 68 23 0.52 14 1.9 8.8 31 1.2 256VB1 2.70 356 149 108 0.50 24 2.6 11.5 32 3.8 360VB2 3.74 423 137 106 0.43 16 3.2 12.0 27 3.3 379VB3 2.40 392 133 93 0.48 24 3.4 15.3 39 3.1 412PI1 1.23 283 161 92 0.87 40 4.3 20.1 66 3.1 514PI2 1.57 277 139 81 0.78 46 5.1 19.2 65 3 638PI 3 2.45 366 144 109 0.68 30 4.1 16.1 63 2.9 557PI4 1.71 328 135 102 0.60 30 4.5 12.7 50 4.1 519OB1 1.40 228 165 99 0.44 36 3.7 13.6 39 4.0 263OB2 1.70 295 123 82 0.48 20 3.1 11.2 36 2.2 447OB3 6.96 279 107 64 0.44 13 2.4 7.3 30 1.9 283OB4 0.64 140 85 43 0.40 26 3.6 12.6 45 1.3 492OB5 3.90 443 245 110 0.95 29 2.3 11.1 26 3.5 443OB6 0.93 140 84 12 0.35 14 1.8 7.5 28 1.3 296OB7 0.40 137 67 10 0.27 13 5.2 7.7 27 1.2 268OB8 2.14 206 138 29 0.44 18 3.4 11.8 42 2.0 383VM1 0.96 205 129 104 0.88 43 6.9 20.3 80 2.2 648VM2 0.82 192 143 121 0.81 44 6.1 21.6 79 2.1 628VM3 0.34 184 130 48 0.89 31 4.6 17.9 65 1.8 434VM4 0.51 269 85 34 0.53 15 3.9 10.5 38 1.8 322VM5 0.63 224 83 30 0.56 12 2.6 7.0 28 1.5 251VM6 0.94 239 122 76 1.26 42 8.3 23.0 89 2.3 801VM7 0.83 225 144 76 0.94 40 6.7 24.6 81 2.6 716VM8 0.72 253 187 164 1.85 15 7.3 24.0 73 2.8 705PD 0.74 169 89 16 0.50 100 2.9 7.8 30 1.2 299V.Mare 2.72 228 190 105 0.90 52 7.5 19.9 54 7.6 550Ucc 1.00XIII Vitt 0.62 181 191 108 0.80 70 11.7 32.4 98 4.0 850

234D

.S.M

antaet

al./

The

Scienceof

theTotal

Environm

ent300

(2002)229–243

Table 1(Continued)

Sample Hg Pb Zn Cu Cd Cr Co Ni V Sb Mn

Brun 0.22 103 167 65 1.30 89 14.8 36.3 107 2.4 1241

Magn 0.05 149 335 57 1.20 52 11.0 26.8 73 4.5 833Camp 0.80 138 136 51 1.40 71 12.6 28.6 84 3.3 1098Nisc 0.17 121 76 37 0.60 24 5.2 15.6 43 4.0 330Tuk 0.59 199 137 71 0.60 48 12.0 23.6 63 6.3 1046U.Ita 1 0.62 281 384 344 1.00 31 7.0 17.6 43 7.8 508U.Ita 2 0.86 198 204 113 0.89 30 7.2 16.6 41 4.6 820Ziino 0.34Mor 1.00 227 227 59 0.80 34 5.5 18.3 35 4.5 478D.Bosco 0.27 95 100 42 0.70 40 7.2 35.9 54 3.4 543Praga 0.09 169 105 53 0.60 72 14.4 22.4 124 2.5 1163Pall 0.29 119 138 47 0.80 46 9.0 20.0 64 3.6 680Garib1 4.46 682 433 304 0.80 51 6.8 11.8 34 15.7 524Garib2 3.79 406 176 104 0.60 33 4.2 10.3 30 5.6 360Garib3 1.49 355 192 108 0.56 34 4.1 12.7 25 6.6 335Gasp 0.21 85 139 42 0.70 79 12.1 32.7 98 2.8 779PF1 0.11 89 99 48 0.76 58 10.2 28.6 88 3.1 807PF2 0.12 159 100 37 0.54 38 7.4 22.3 51 3.4 526PF3 0.09 140 115 45 1.28 49 10.1 22.6 74 2.2 784PF4 0.12 57 142 50 1.62 45 13.5 38.6 99 1.2 1056PF5 0.08 68 84 33 0.53 61 8.2 23.2 71 1.4 558PF6 0.28 126 146 68 1.45 58 11.9 32.3 92 4.3 772PF7 0.21 81 98 37 0.60 34 8.1 17.7 52 1.7 643PF8 0.04 60 52 25 0.37 50 10.0 16.6 60 1.1 156PF9 0.13 103 89 43 0.97 25 11.5 23.4 72 1.7 871PF10 0.31 157 87 39 0.62 58 5.0 13.7 37 2.9 252PF11 56.00 2516 203 207 3.80 58 13.6 38.3 97 27.5 1259PF12 0.20 85 147 55 1.26 56 9.6 26.3 103 2.3 730PF13 0.29 147 170 84 1.28 50 12.5 29.1 96 4.4 949PF14 0.07 165 126 51 0.59 51 8.2 23.5 74 4.0 578

Min 0.04 57 52 10 0.27 12 1.5 7.0 21 1.1 142Max 56.00 2516 433 344 3.80 100 14.8 38.6 124 27.5 1259Media 1.85 253 151 77 0.84 39 6.5 19.1 58 3.7 566SD 6.73 302 71 56 0.51 19 3.6 8.0 25 3.6 263

BedrocksPF rock 0.01 35 71 19 1.62 103 7.7 19.7 53 0.6 5785M.Gallo 0.02 47 11 17 0.25 16 1.4 4.5 35 0.5 559C.Pisani 0.01 41 9 13 0.23 11 1.4 2.8 32 0.5 6611V.Tasca 0.02 34 15 12 0.22 36 1.5 4.9 33 0.6 20014P.Sturzo 0.03 30 15 17 0.15 40 2.1 4.9 28 0.5 10610F.Oreto 0.01 37 13 13 0.21 39 2.2 4.2 28 0.6 311

235D

.S.M

antaet

al./

The

Scienceof

theTotal

Environm

ent300

(2002)229–243

Table 1(Continued)

Sample Hg Pb Zn Cu Cd Cr Co Ni V Sb Mn

Sample(mg kg )y1 Locality Hg Pb Zn Cu Cd Cr Co Ni V Sb MnTopsoilsVT (12) Villa Trabia 0.80 250 167 66 0.81 26 3.6 16.1 48 3.1 397VB (3) Villa Bonanno 2.95 390 140 102 0.47 21 3.1 12.9 33 3.4 384PI (4) P.zza Indipendenza 1.74 314 145 96 0.73 37 4.5 17.0 61 3.3 557OB (8) Orto Botanico 2.26 234 127 56 0.47 21 3.2 10.4 34 2.2 359VM (8) Villa Malfitano 0.72 224 128 82 0.96 30 5.8 18.6 67 2.1 563U Ita (2) Unita d’Italia` 0.74 239 294 229 0.95 31 7.1 17.1 42 6.2 664Garib (3) Villa Garibaldi 3.25 481 267 172 0.65 39 5.0 11.6 30 9.3 406FP (14) Favorita Park 0.16 109 114 47 0.90 51 9.9 25.0 76 2.6 676FP11 Favorita Park 56.00 2516 203 207 3.80 58 13.6 38.3 97 27.5 1259PD Parco d’Orleans 0.74 169 89 16 0.50 100 2.9 7.8 30 1.2 299V Mare Villa a Mare 2.72 228 190 105 0.90 52 7.5 19.9 54 7.6 550XIII Vitt XIII Vittime 0.62 181 191 108 0.80 70 11.7 32.4 98 4.0 850Brun Brunelleschi 0.22 103 167 65 1.30 89 14.8 36.3 107 2.4 1241Magn Magnolie 0.05 149 335 57 1.20 52 11.0 26.8 73 4.5 833Camp Camporeale 0.80 138 136 51 1.40 71 12.6 28.6 84 3.3 1098Nisc Villa Niscemi 0.17 121 76 37 0.60 24 5.2 15.6 43 4.0 330Tuk Tukory 0.59 199 137 71 0.60 48 12.0 23.6 63 6.3 1046Mor Morello 1.00 227 227 59 0.80 34 5.5 18.3 35 4.5 478D Bosco Don Bosco 0.27 95 100 42 0.70 40 7.2 35.9 54 3.4 543Praga Praga-Belgio 0.09 169 105 53 0.60 72 14.4 22.4 124 2.5 1163Pall Pallavicino 0.29 119 138 47 0.80 46 9.0 20.0 64 3.6 680Gasp De Gasperi 0.21 85 139 42 0.70 79 12.1 32.7 98 2.8 779

Median 0.68 202 138 63 0.68 34 5.2 17.8 54 3.0 519Minimum 0.04 57 52 10 0.27 12 1.5 7.0 21 1.1 142Maximum 6.96 682 433 344 1.86 100 14.8 38.6 124 15.7 1241Lower quartile 0.22 140 104 43 0.54 25 3.7 12.6 37 2.1 360Upper quartile 1.40 269 167 99 0.90 50 8.3 23.4 73 4.0 716Std. Dev. 1.26 111 71 54 0.35 19 3.5 7.7 24 2.1 250

BedrocksBedrocks(6) 0.02 37 22 15 0.45 41 2.7 6.8 35 0.6 219Median 0.02 36 14 15 0.23 38 1.8 4.7 33 0.6 153Minimum 0.01 30 9 12 0.15 11 1.4 2.8 28 0.5 55Maximum 0.03 47 71 19 1.62 103 7.7 19.7 53 0.6 578Lower quartile 0.01 34 11 13 0.21 16 1.4 4.2 28 0.5 66

236D

.S.M

antaet

al./

The

Scienceof

theTotal

Environm

ent300

(2002)229–243

Table 1(Continued)

Sample Hg Pb Zn Cu Cd Cr Co Ni V Sb Mn

Upper quartile 0.02 41 15 17 0.25 40 2.2 4.9 35 0.6 311Std. Dev. 0.01 6 24 3 0.58 33 2.5 6.3 9 0.1 200

Unpolluted soils* 0.066 44 122 34 1.3 83 1728** 0.05y0.1 22y44 45y100 13y24 0.37y0.78 12y83 4.5y12 12y34 18y67 0.3y0.9 270y525

Mean values of different natural soils of Sicily(Bellanca et al., 1996; Palumbo et al., 2000).*

Mean ranges calculated to the world scale(Fergusson, 1990; Kabata-Pendias and Pendias, 1992).**

237D.S. Manta et al. / The Science of the Total Environment 300 (2002) 229–243

Table 2Average heavy metal concentrations(mg kg ) in urban soils from different cities in the worldy1

City Hg Pb Zn Cu Cd Cr Co Ni V Sb Mn Reference

Rome 330.8 0.31 Angelone et al.(1995)Pittsburg 0.51 398 1.2 Carey et al.(1980)Boston 800 Spittler and Feder(1979)Warsaw 57 166 31 0.73 32 5.1 12 337 Czarnowska(1980)Hamburg 218.2 516 146.6 2.0 95.4 62.5 750 Lux(1986)Salamanca 53.1 0.53 Sanchez-Camazano et al.(1994)´Coruna˜ 309 206 60 0.3 39 11 28 3 Cal-Prieto et al.(2001)Central Madrid 621 Pellicer(1985)Madrid 161 210 71.7 74.7 6.42 14.1 30 437 De Miguel et al.(1998)Bangkok 47.8 118 41.7 0.29 26.4 24.8 340 Wilcke et al.(1998)Aberdeen 94.4 58.4 27 23.9 6.4 14.9 286 Paterson et al.(1996)Birmingham 570 Department of the Environment(1982)Glasgow 216 207 97 0.53 Gibson and Farmer(1986)Central London 647 Rundle and Duggan(1980)Greater London 250 Rundle and Duggan(1980)Outer London 322 Davies et al.(1979)London boroughs 294 183 49 1.0 Culbard et al.(1988)London 294 183 73 1.0 Thornton(1991)Hong Kong 93.4 168 24.8 2.18 Li et al.(2001)Hong Kong 100 93.9 27.5 1.89 Wong et al.(1996)Hong Kong 89.9 58.8 16.1 0.94 Chen et al.(1997)Manila 213.6 440 98.7 0.57 114 20.9 1999 Pfeiffer et al.(1988)

cate common contamination sources for these met-als. Cr shows good correlation with Co, Ni, V andMn (r s0.6–0.7). These four metals exhibit2

excellent correlations with SiO , Al O and2 2 3

Fe O (r s0.8–0.9), suggesting their strong affin-22 3

ities for alumino–silicate phases and Fe-oxides ofthe soils. Chromium is significantly correlated withthese major oxides but not as well as with Co, Niand V. Cadmium is positively correlated with Co,Ni, V and major oxides(r s0.5), but a better2

correlation with Mn(r s0.6) reflects its affinity2

for soil Mn-phases.Heavy metal concentrations do not correlate

with pH, CEC and organic matter contents. Owingto the narrow range of pH(7.2–8.3) measured inthe samples, this parameter has limited importanceon the heavy metal distribution, substantially lim-iting their mobility because of the neutral-subal-kaline environment.

4.5. Enrichment factors (EFs)

Heavy metal enrichment factors(EFs) for thesoil samples were calculated by assuming as geo-

chemical background concentrations of naturalsoils in Sicily reported in Table 1. Thus,EFselement concentration in urban soilyelement con-centration in average natural soil. TheEF valuesfor Co, V and Sb were calculated as concentrationratios between the soil and average bedrock(Table1). Most significant results are represented in Fig.2.Consistent with indications of inter-element rela-

tionships,EFs are generally less than 1 for Ni,Mn, Cr and Cd, which suggests a natural sourcefor these elements in the studied soils. On theother hand, the urban soils contain much higherPb, Zn, Cu and Hg concentrations when comparedto natural soils and have highEFs confirming animportant role of the anthropogenic pollution. Inparticular, Pb is enriched on average by 5–10times and Hg exhibitsEF values as high as 35.Cobalt and V are slightly to moderately enriched

in topsoils with respect to bedrocks(2.3 and 1.6,respectively), suggesting a ‘natural’ concentrationof these metals during weathering andyor pedo-genesis processes. For Sb, highEFs (Fig. 2)

238 D.S. Manta et al. / The Science of the Total Environment 300 (2002) 229–243

Fig. 2. Enrichment factors for some metals in topsoil samples with respect to natural soils in Sicily(Hg, Pb and Zn) and bedrocks(Sb). Data used in calculating EFs are those of Table 1.

239D.S. Manta et al. / The Science of the Total Environment 300 (2002) 229–243

Fig. 3. Hierarchical clustering results(dendrogram) of theheavy metal concentrations in topsoil samples of the Palermocity.

together with a wide range of values hint at ananthropic nature of most of the metal.

4.6. Hierarchical clustering analysis

In order to discriminate distinct groups of heavymetals as tracers of natural or anthropic source, anexplorative hierarchical cluster analysis was per-formed on the available dataset. The obtainedresults(Fig. 3) enabled the identification of twomain groups of elements, clustered at level ofsimilarity 4, discriminating V, Ni, Mn, Co, Cr andCd (Group I) from Cu, Zn, Sb, Pb and Hg(GroupII). This result is consistent with elemental rela-tionships indicating that the metals of Group Istrongly correlate with the alumino-silicate phases,thus supporting a natural origin for these elements,and is also suggested by their relatively lowconcentration values and relatively low standarddeviations. In accordance withEF data, Group IIincludes metals dominated by an anthropic input.

4.7. Spatial distribution of pollutant metals andfactors controlling contamination

Distribution patterns of the main pollutant met-als in the whole urban area of Palermo are visu-alized by a set of concentration maps obtained byprocessing data in Table 1 with the Surfer program(Fig. 4).

Lead, Zn, Sb and Hg show similar spatialdistributions highlighting two significantly pollut-ed zones corresponding to:(i) the historical centerof the city (lower-right side of the maps), open toheavy vehicle traffic; and(ii) green areas close tothe crossing of major urban traffic axes(centralpart of the maps).The spatial distribution of these elements sug-

gests the dominant role of vehicle traffic as pol-lutant source. However, it is important to take intoaccount additional point sources of contaminationsuch as gas industries for all metals, chemicallaboratories for Hg, and fireworks for Sb.A moderate pollution is recorded in the Favorita

Park area(top center in Fig. 4) where the vehicletraffic is generally declining and vegetation barri-ers play an important protective role for the soils.However, it is worth noting that very high concen-tration values of heavy metals were recorded for asample from this park(FP11, see Table 1) andthat these anomalous data were discarded in thecourse of statistical treatments. The severe contam-ination of this zone is related to the activity of afiring range, located some years ago in this area.Finally, we must consider that the chemical

composition of topsoils in Palermo might havebeen affected by the use of garden fertilizers. Infact, the analyzed soils contain P O levels, rang-2 5

ing between 0.22 and 1.34, consistently higherthan those of natural soils in Sicily(P O from2 5

0.04 to 0.35; Bellanca et al., 1996; Palumbo et al.,2000). Owing to the significant correlationsbetween P O and Hg, Pb, Zn and Cu(r s0.5–2

2 5

0.6), the enhanced levels of P O are attributed to2 5

fertilizer applications.

4.8. PCA and statistical evaluation of anthropicpollution

To reduce the high dimensionality of the sam-pleyvariable space, a principal component analysis(PCA) was applied to the available dataset ofheavy metals. Normal distribution of each metalwas previously checked, since the PCA proceduresare based on linear combinations of the variablesand their correlations. The obtained Factors wererotated using a varimax normalized algorithm,which allows an easier interpretation of the prin-

240 D.S. Manta et al. / The Science of the Total Environment 300 (2002) 229–243

Fig. 4. Maps of Hg, Zn, Pb, and Sb distribution(values in mg kg ) in the urban area of Palermo(scale 1:100 000).y1

cipal component loadings and the maximization ofthe variance explained by the extracted factors.Two principal components were extracted from

the available dataset, explaining a total varianceof approximately 71%(Table 3).In Table 3 and Fig. 5, the factor loadings for

the two extracted factors are reported allowing aneasy interpretation of the master variables. FactorI is dominated by Co, Ni, V, Cr and Mn. Based

on earlier discussions suggesting that the distribu-tion of these elements is mainly controlled bynatural materials, the first factor can be inferredas a ‘lithogenic factor’. Factor II loaded by Hg,Pb, Zn, Cu and Sb can be identified as a tracer ofanthropic pollution. Cadmium shows high valuesin F I, but it is also represented in F II. Anexplanation for this may be that the distribution ofCd is affected by both lithogenic and anthropogen-

241D.S. Manta et al. / The Science of the Total Environment 300 (2002) 229–243

Table 3Values of two extracted factor loadings for the studied heavymetals; values of dominant elements in each factor reported inbold

Factor I Factor II

Hg y0.43 0.62Pb y0.40 0.83Zn 0.21 0.87Cu 0.09 0.88Cd 0.68 0.27Cr 0.71 y0.10Co 0.92 y0.14Ni 0.91 y0.12V 0.91 y0.18Sb 0.14 0.94Mn 0.91 0.01

Expl. Var. 45% 26%

Fig. 5. Map of the estimated ‘average pollution’ in the city ofPalermo(scale 1:100 000).

ic control. Addition of Terra Rossa soils to urbansoils in Palermo could be responsible for enhancedCd levels due to the presence in the Terra Rossaof Cd-enriched Fe–Mn nodules(Palumbo et al.,2001), which accounts for the strong correlationof Cd with Mn. On the other hand, a few siteswith strong positive Cd anomalies are expressionof an additional influence of pollutant sources.Conceptually, Factor II condenses the informa-

tion of the heavy metals as tracers of anthropicpollution. The calculated scores of Factor II wereplotted on the map of the urban area of Palermo(Fig. 5) to gather an ‘average image’ of theanthropic pollution in the city. This map indicatesthe occurrence of a diffuse pollution related toanthropic activity with a good correspondence ofpeaks of metal contaminations and sites of majordeposition of atmospheric particles generated pri-marily from traffic. Such an urban distributionmap can be used for direct comparison withthematic maps and database(e.g. topographic,geological, etc.) using Geographical InformationSystem(GIS) software.

5. Conclusions

The data obtained in this study demonstrate thatthe heavy metal concentrations of urban soils canbe used as powerful geochemical tracers for mon-itoring the impact of human activity, provided that

background levels have been correctly interpretedand established.Topsoil samples from green areas in the city of

Palermo show Pb, Zn, Cu, Sb and Hg concentra-tions higher than those of natural soils in Sicilyand comparable to those recorded in other impor-tant European cities. Based on the whole datasetthese metals are inferred to derive from anthropo-genic sources, whereas Co, Ni, V, Cr and Mndistributions are mainly controlled by lithogenicinputs. Except for a few anomalously high Cdvalues that are an expression of the influence ofpollutant sources, relatively high levels of cadmi-um in the investigated soils were interpreted toreflect a natural enrichment by weathering andpedogenesis processes.Results of combined multivariate statistical anal-

yses and the distribution patterns of the pollutantmetals suggested that vehicle traffic represents themost important pollutant source for the studiedurban environment. Plotting PCA results on themap of the city can be used to advantage ininvestigating urban soil pollution and its potentialdeleterious effect, especially when used for directcomparison with thematic maps and database byGIS software.

242 D.S. Manta et al. / The Science of the Total Environment 300 (2002) 229–243

Acknowledgments

We would like to thank the management of the‘Assessorato al Centro Storico’ of Palermo cityand that of the ‘Ente Gestore Riserva NaturaleMonte Pallegrino’ for authorizing soil sampling indifferent sites. We are grateful to the managementof the Serveis Cientificotecnics of Barcelona Uni-`versity (UB) and in particular to Dr A. Padro(Technical Staff) for all facilities concerning theICP-MS analyses. Thanks are also due to thankProf. C. Dazzi(Palermo University) for facilitiesrelative to chemico-physical parameters of topsoilsamples. We thank H.W. Mielke and an anonymousreferee for reviewing an earlier version of thepaper. This research was supported by the follow-ing grants to AB: CNR-99.00636.CT05; MIUR-Ex quota 60%.

References

Albasel N, Cottenie A. Heavy metal contamination near majorhighways, industrial and urban areas in Belgian Grassland.Water Air Soil Pollut 1985;24:103–109.

Allen S, Grimshaw HM, Parkinson JA, Quarmby C. Chemicalanalysis of ecological materials. Oxford: Blackwell, 1974.(521 pp).

Angelone M, Corrado T, Dowgiallo G. Lead and cadmiumdistribution in urban soil and plants in the city of Rome: apreliminary study. Proceedings of the Third InternationalConference on the Biogeochemistry of Trace Elements 1995.p. 23–24.

Angelone M, Cavaliere A, Dowgiallo G. Mercury levels innatural soils and two plant species(spartium junceum l. andavena sativa l.) in Latium (central Italy). Proceedings ofthe Fifth International Conference on the Biogeochemistryof Trace Elements 1999. p. 540–541.

Bacon JR, Berrow ML, Shand CA. Isotopic composition as anindicator of origin of lead accumulations in surface soils.Int J Environ Anal Chem 1992;46:71–76.

Barahona E, Huertas F, Pozzuoli A, Linares J. Mineralogia egenesi dei sedimenti della provincia di Granata(Spagna).Miner Petrogr Acta 1982;26:61–90.

Bellanca A, Hauser S, Neri R, Palumbo B. Mineralogy andgeochemistry of Terra Rossa soils, western Sicily: insightsinto heavy metal fractionation and mobility. Sci TotalEnviron 1996;193:57–67.

Bini C, Ferretti O, Chiara E, Gragnani R. Distribuzione ecircolazione degli elementi in traccia nei suoli. Suoli dellaRegione Puglia. Rend Soc Ital Miner Petrol 1984;39:281–296.

Burguera JL, Burguera M, Rondon C. Lead in roadside soilsof Merida City, Venezuela. Sci Total Environ 1988;77:45–49.

Cal-Prieto MJ, Carlosena A, Andrade JM, et al. Antimony astracer of the anthropogenic influence on soils and estuarinesediments. Water Air Soil Pollut 2001;129:248–333.

Carey AE, Gowen JA, Forchand TJ, Wiersma GB. Heavymetal concentrations in soils of five United States cities,1972 Urban Soils Monitoring Program. Pestic Monit J1980;13:150–154.

Chen TB, Wong JWC, Zhou HY, Wong MH. Assessment oftrace metal distribution and contamination in surface soilsof Hong Kong. Environ Pollut 1997;96:61–68.

Covelli S, Faganeli J, Horvat M, Brambati A. Mercury contam-ination of coastal sediments as the result of long-termcinnabar mining activity(Gulf of Trieste, northern Adriaticsea). Appl Geochem 2001;16:541–558.

Culbard EB, Thornton I, Watt J, Wheatley M, Moorcroft S,Thompson M. Metal contamination in British urban dustsand soils. J Environ Qual 1988;17:226–234.

Czarnowska K. Akumulacja metali ciezick w glebach, oslinachi niektoych zwieretach na erenie. Warzawy Rocz Glebozn1980;31:77–115.

Davies BE, Houghton NJ. Distance-decline patterns in heavymetal contamination of soils and plants in Birmingham,England. Urban Ecol 1984;8:285–294.

Davies BE, Conway D, Holt S. Lead pollution on Londonsoils: a potential restriction on their use for growing vege-tables. J Agric Sci Camb 1979;93:749–752.

Davies DJA, Watt JM, Thornton I. Lead levels in Birminghamdusts and soils. Sci Total Environ 1987;67:177–185.

De Miguel E, Jmenez de Grado M, Llamas JF, Martin-DoradoA, Mazadiego LF. The overlooked contribution of compostapplication to the trace element load in the urban soil ofMadrid (Spain). Sci Total Environ 1998;215:113–122.

Department of the Environment. Pollution report 15. London:Central Directorate for Environmental Pollution, D.O.E.,HMSO, 1982.

Facchetti S, Geis F, Gaglione P, Colombo A, Garibaldi G,Spallanzani G, Gilli G. CEE status report I, EUR 8352 EN,1982.

Farmer JG, Lyon TDB. Lead in Glasgow street dirt and soil.Sci Total Environ 1977;8:89–93.

Fergusson JE. The heavy elements: chemistry, environmentalimpact and health effects. Pergamon Press, 1990. (379 pp).

Ferretti M, Batistoni P, Bini M, Bussotti F, Cenni E, GrassoniP. Lead and cadmium distribution in plants and soils alongthe Italian highways network. Heavy Met Environ1991;1:66–69.

Folinsbee LJ. Human health effects of air pollution. EnvironHealth Perspect 1993;100:45–46.

Franzini M, Leoni L, Saitta M. Revisione di una metodologiaanalitica per fluorescenza-X basata sulla correlazione com-pleta degli effetti di matrice. Rend Soc It Miner Petrog1975;31(2):35–378.

Gazzetta Ufficiale della Repubblica Italiana. Approvazione deimetodi ufficiali di analisi chimica del suolo. Ministerodell’Agricoltura e delle Foreste, Roma, 25 maggio1992;121:6–90.

243D.S. Manta et al. / The Science of the Total Environment 300 (2002) 229–243

Gibson MG, Farmer JG. Multi-step chemical extraction ofheavy metals from urban soils. Environ Pollut B1986;11:117–135.

Guerzoni S, Frignani M, Giordani P, Frascari F. Heavy metalsin sediments from different environments of a NorthernAdriatic Sea area. Environ Geol Water Sci 1984;6:111–119.

Husselmann J. On the routine analysis of carbonates inunconsolidated sediments. J Sed Petr 1966;36:622–625.

Kabata-Pendias A, Pendias H. Trace elements in soils andplants, 2nd ed. CRC Press, 1992. (150 pp).

Kelly J, Thornton I, Simpson PR. Urban geochemistry: a studyof the influence of anthropogenic activity on the heavymetal content of soils in traditionally industrial and non-industrial areas of Britain. Appl Geochem 1996;11:363–370.

Li X, Poon C-s, Liu PS. Heavy metal contamination of urbansoils and street dusts in Hong Kong. Appl Geochem2001;16:1361–1368.

Lux W. Shhwermetallgehalte und isoplethen in Boden, sub-hydrishen Ablagerung und Pflanzen im Sudosten Hamburgs.Hamburger Bodenkudliche Arbeiten 1986;5:249 pp.

Markus JA, McBratney AB. An urban soil study: heavy metalsin Glebe, Australia. Aust J Soil Res 1996;34:453–465.

Palumbo B, Angelone M, Bellanca A, et al. Influence ofinheritance and pedogenesis on heavy metal distribution insoils of Sicily, Italy. Geoderma 2000;95:247–266.

Palumbo B, Bellanca A, Neri R, Roe MJ. Trace metalpartitioning in Fe–Mn nodules from Sicilian soils, Italy.Chem Geol 2001;15:257–269.

Paterson E, Sanka M, Clark L. Urban soils as pollutant sinks—a case study from Aberdeen, Scotland. Appl Geochem1996;11:129–131.

Pellicer DMJ. Boletin aula de ecologia 4, Ayuntamiento deMadrid. Madrid: Consejalia de Medio Ambiente, 1985.

Pfeiffer EM, Freytag J, Scharpenseel HW, Miehlich G, VicenteV. Trace elements and heavy metals in soils and plants ofthe southeast Asian Metropolis Metro Manila and of ricecultivation provinces in Luzon, Philippines. HamburgerBodenkundliche Arbeiten 1988;11:264 pp.

Rundle S, Duggan M. Report DEySByEDSyR91. London:Greater London Council, 1980.

Sanchez-Camazano M, Sanchez-Martın MJ, Lorenzo LF. Lead´ ´ ´and cadmium in soils and vegetables from urban gardens ofSalamanca(Spain). Sci Total Environ 1994;146y147:163–168.

Schultz LG. Quantitative interpretation of mineralogic com-position from X-ray and chemical data for the Pierre Shale.U.S. Geol Surv, Prof Pap 1964.

Spittler TM, Feder WA. Commun Soil Sci Plant Anal1979;10:1195.

Steinmann M, Stille P. Rare earth element behaviour and Pb,Sr, Nd isotope systematic in a heavy metal contaminatedsoil. Appl Geochem 1997;12:607–623.

Strnad M, Sanka M, Bohacek Z, Borkovcova I, Vondra J. Soilpollution by heavy metals and polycyclic aromatic hydro-carbons in the town of Brno(Czech Republic). Int J EnvironAnal Chem 1994;54:233–248.

Thornton I. Metal contamination of soils in urban areas. In:Bullock P, Gregory PJ, editors. Soils in the urban environ-ment. London: Blackwell, 1991. p. 47–75.

Tiller KG. Urban soil contamination in Australia. Aust J SoilRes 1992;30:937–957.

Wilcke W, Muller S, Kanchanakool N, Zech W. Urban soilcontamination in Bangkok: heavy metal and aluminiumpartitioning in topsoils. Geoderma 1998;86:211–228.

Wong MH, Chen TB, Wong JWC. Trace metal contaminationof the Hong Kong Soil environment: a review. Contaminantsand the soil environments in the Australia-Pacific region.Dordrecht: Klummer Academic Publisher, 1996. p. 501–511.