assessment of the quality of the air in the city of palermo through chemical and cell analyses on...

Atmospheric Environment 35 (2001) 6435–6445

Assessment of the quality of the air in the city of Palermothrough chemical and cell analyses on Pinus needles

Maria Lombardoa, Rita M. Melatia,*, Santino Orecchiob

aDepartment of Botanical Science, University of Palermo, Via Archirafi 38, 90123 Palermo, ItalybDepartment of Inorganic Chemistry, University of Palermo, Parco d’Orleans, 90100 Palermo, Italy

Received 26 May 2000; received in revised form 16 June 2001; accepted 22 June 2001

Abstract

The influence of air pollution on the chemical composition of Pinus sp. needles was examined in polluted and controlsites in and around the city of Palermo (Sicily). The chemical composition of needles indicated the extent ofcontamination of the trees, which were cytologically examined. Cell analysis was carried out on pine samples, includingneedles and pollens, from 15 different locations. Biostructural and spectrophotometric tests were performed. In

particular, concentrations of toxic (Cd, Pb) and non-toxic metals (Fe,Cu, Zn) were determined, as well as injury causedby their accumulation in the needles. The more highly urbanised areas showed higher concentrations of metals (Pb, Cu.Zn, Fe); only the concentrations of Cd and Mn turned out to be constant in all the sites. Cell analysis revealed displasic

cells and secondary metabolite accumulations in trees from polluted sites. These changes observed were most likelycaused by the toxic effect of pollutants. r 2001 Elsevier Science Ltd. All rights reserved.

Keywords: Pinus pinea L.; Quality of air; Chemical and cell analyses; Needles; Concentrations of lead; Atomic absorption

spectroscopy

1. Introduction

Most of the trace elements (Cd, Cr, Cu, Fe, Mn, Ni,

Pb, Zn) are present in the air in the form of particles,while only few are found in the form of both gas andparticles. These elements are derived from mining, metalsmelting, coal and petroleum combustion, oil burning,

incineration of waste, cement production and otherindustrial activities (Magnavita, 1989). Pb, Cd, Zn andNi are found in petrol and motor oil; therefore motor

vehicles are an important source of these contaminants(Gordon, 1986). Trace elements are removed from theatmosphere by wet and dry deposition, diffusion and

retention on solid surfaces. Vegetation intercepts theaerosol and the concentrations of some of these elementsare high in samples of plants from urban and industrial

areas (Ravinsky et al., 1993). The high surface/volume

ratio and the waxy and resinous coating on the leaves ofmany plants facilitate the accumulation on their surfaceof substances, which are present in the air in the form of

particulate matter. Some of these pollutants are madesoluble by reacting with CO2 and with the aqueous filmof the leaf, and then they are firmly fixed to the tissues(Lorenzini, 1983).

Leaf, root and the trunk itself can effectively be usedto obtain information on the quality of the environment.They are essential components of plant biological

markers which, as in the case of pines, are widespreadand can supply integrated data over time. Plantbiomarkers continually interact with their surrounding

environment, rapidly ensnaring toxic and non-toxicchemical elements.Biomonitoring involves the use, as ‘‘living in-

struments’’, of organisms (animals and plants) capableof exhibiting the toxic effects of the pollutants (Ierardiet al., 1995; Campanella, 1996; Cardellicchio et al.,1998). Plant organisms are thought to be the most

appropriate because they are immobile; they act as

*Corresponding author. Department of Botanical Science,

University of Palermo, Via Trinacria N.8, 90144 Palermo, Italy.

E-mail address: [email protected] (R.M. Melati).

1352-2310/01/$ - see front matter r 2001 Elsevier Science Ltd. All rights reserved.

PII: S 1 3 5 2 - 2 3 1 0 ( 0 1 ) 0 0 3 4 8 - X

important receptors and so reflect environmental con-ditions (Matta and Nicolotti, 1996; Cardarelli, 1983;

Giovenco et al., 1996).Biochemical, physiological or morphological re-

sponses may be obtained from the organisms and used

for monitoring the quality of the environment. All thesereactions depend not only on the factor to be indicated,but also on nutrients, age and watering status (Market,1993). The indicator plant function is to detect and

recognise the effects of the pollutants, but these effectsmay also be measured quantitatively in order to monitortheir intensity. Low concentrations of pollutants in leaf

tissues produce physiological alterations and asympto-matic injuries, such as reduced growth, reproductiondifficulties and early senescence, which are difficult to

assess macroscopically. High concentrations producemore noticeable effects such as an alteration in thecolour and in the shape of the foliage and even complete

necrosis (Lorenzini, 1983).The organism’s tolerance to harmful substances

allows it to accumulate these substances, in turnallowing us to qualify and quantify them. The same

organism can be a bioaccumulator of a certain substancein low concentrations, and a bioindicator when con-centration levels exceed the threshold beyond which

their effects are considered toxic.The city of Palermo was chosen for this study on

heavy metal pollution, which examines Pinus sp. needles.

We chose the pine, a vascular plant, because itsphysiology, morphology and ecology make it an easyplant to identify, even for those who are neither expertsnor skilled botanists. Its needle-shaped leaves, with

amply cuticularised leaf epidermis and surface depositsof resins, are particularly sensitive to environmentalconditions (Raven et al., 1990; Elias and Irwin, 1977).

The elements (Pb, Cd, Zn, Cu) determined in the pineleaves were chosen on the basis of the risk which some ofthem pose to our health and for their potential

bioaccumulation in the food chain (Guasticchi et al.,1992) since they originate, as some authors havesuggested (Magnavita, 1989), in combustion processes.

The elements Fe and Mn are of little environmentalinterest, and were used to assess natural sources. Theobjective of the study was to identify heavy metalpollution levels in the city air, and examine cell

modifications induced in plants under stress conditions.

2. Materials and methods

2.1. Sampling methods and characteristics of the stations

Fifteen sites with different levels of traffic andurbanisation were selected in city of Palermo (Table

1). Needles and pollen samples of Pinus genus (Pinuspinea L., Pinus halepensis Miller, Pinus pinaster Aiton)

were chosen for this research because they are commonvascular plants in Palermo.

Sampling was carried out in three different periods(winter, summer, autumn) in 1997. Two sites far fromany prominent heavy metal source were selected as a

control (Fig. 1): one on the island of Ustica (site 1), theother in the Botanical Garden of Palermo (site 2). Amap of the study area with the location of the samplingsites is shown in Fig. 1.

Green or chlorotic needles were randomly collectedfrom all the way around the perimeter of the tree foliageand were preserved in polyethylene bags during trans-

portation.

2.2. Chemical and cell analyses

The chemical analyses were performed on fullydeveloped needles previously, rinsed with ‘‘agitated’’

water to get rid of the deposit on the needle surface,which is substantial in urban environments (Ferrariet al., 1994). In this way, it was possible to assess to what

extent the pollutants managed to penetrate the needles.Before starting the chemical analyses, the leaf sampleswere dried in an oven at 801C for one night. Aftercooling in a desiccator, they were reduced to a fine

powder in a porcelain mortar. Precisely weighedquantities of each sample (0.5 g) were used to preparethe solution in a microwave digester where, due to a

supply of ‘‘non-pulsed’’ power, an optimal control of theoxidation processes of the samples was performed. Amixture of nitric acid (6ml) at 65% and hydrogen

peroxide (1ml) at 30% was used. Alongside thepreparation of the leaf sample solutions, for everydigestion cycle a blank was prepared (Cenci et al., 1998).The extracted solutions, clear and free of organic

substances, were left to cool and their volume wasadjusted to 50ml with bidistilled water.The quantitative analyses of iron, zinc, manganese

and copper in the solutions were carried out with atomicabsorption spectroscopy with flame atomisation. Thosefor lead and cadmium were carried out by atomic

absorption spectroscopy and by using graphite furnaceatomisation.All the sample determinations were repeated three

times to minimise the risk of error.We calculated the mean, standard deviation, median

and geometric mean of the chemical measurements inorder to evaluate the differences between the various

sampling stations.The biological analyses started with an assessment of

the plant’s morphological characteristics (foliage regu-

larity, chlorosis and browning leaves, necrosis of theneedle tips, browning branches and curling needles),carried out ‘‘in situ’’ during the sampling.

Subsequently, in the laboratory, the needles werediaphanised in order to analyse their architecture. A

M. Lombardo et al. / Atmospheric Environment 35 (2001) 6435–64456436

batch of needles from site 7 was treated with a solution

of NaOH at 10%, kept at room temperature for a fewdays (3–4) and then stained with basic fuchsine at 1%(Fuchs, 1963).Transversal cryosections on the proximal and distal

portions of the needles, collected in the control site (site2) and in sites with greater volume of traffic (sites 7, 9),were prepared for cell evaluations and biochemical

assessment of acid phosphatase and polyphenols levels.The cryosections were stained with a solution made upof the colouring agent Fast Blu BB, substrate Naphthol

AS BI phosphate and acetate buffer 0.2M (pH=5.4).After staining, the slides were incubated for around30min, both at 371C and at room temperature (Gahan,1984), in order to highlight phosphatases sites and

polyphenol distribution.

In order to correlate the results of the examination of

the needles with those of the cytological analyses of thepollen grains, specimens were prepared using pollentaken from inflorescences. These were placed on a slidewith a drop of glycerol gelatine and then observed with

an optical microscope. If the pollen was fractured or hadonly one sac, a vitality test was carried out with diacetatefluorescein, at 0.1% in acetone.

3. Results

Table 2 gives the statistical summary of the chemicalconcentrations of heavy metals found in needle samples.

Among the 15 sites examined, Piazza Indipendenzashows the highest concentration of all metals except Cd

Table 1

Leaf collection station

No Site Location Characteristics

1 Ustica Boschetto Situated in the wood on the island

of Ustica

No traffic

2 Botanical Gardens Situated inside the Botanical

Gardens, close to the sea

Fairly distant from main road

traffic, nearby there is an

installation for the production of

city gas

3 SS113 On the trunk road heading to

Messina

Light vehicles, heavy, smooth flow

4 Palazzina Cinese Far from the city centre, in the

Favorita park

Light traffic, light flow

5 Piazza Niscemi Situated on the outskirts of the city

6 Via Regione Siciliana Situated on the Palermo ring road

which links the Palermo-Catania

and Palermo-Trapani motorways

Very heavy traffic, however, road works

have forced traffic to be diverted

7 Via. A. de Gasperi Situated in the new area of the city Various types of traffic, steady flow,

continually slowed down

8 Via Belgio

9 Piazza Indipendenza Situated in the city centre Steady flow of traffic all day, frequently

halted at traffic lights

10 Brancaccio Industrial

Zone

Situated on the outskirts of the city Area affected by a moderate amount of industrial

emissions. Practically no traffic

11 Via Giachery Situated near the fruit and

vegetable market

Area with heavy traffic, often halted

12 Via Basille Situated on the outskirts of the city Light vehicles, heavy, smooth flow

13 Piazza Tommaso Edison Situated in a central area but far

from main roads,

therefore not greatly exposed to traffic

pollution

Area with heavy traffic

14 Via V.P. Martini Situated on the outskirts of the city Light vehicles, light flow

15 Via Francesco Crispi Situated near to the port of Palermo

where there is dispersion of pollutants

The area is affected by heavy traffic and frequent

traffic jams due to traffic lights

M. Lombardo et al. / Atmospheric Environment 35 (2001) 6435–6445 6437

and Mn. The Ustica, Botanic Garden and Piazza T.Edison stations have the lowest concentrations ofpollutants, while intermediate values were found for

the other stations. As far as Pb, Fe and Zn areconcerned, the concentration values, compared to thosereported by Gonzales Soto et al. (1996), turn out to be

higher than the limit values, while Mn and Cd fall withinthe limits.Fig. 2 shows average concentrations of lead (mg/kg

d.w.) in the washed pine needles from the various sites. Inheavy traffic areas (sites 6, 7, 8, 9, 10, 11, 12), the averageconcentrations of Pb in the leaf were higher (14–22mg/

Kg). In sites 6, 7, 10, 11, 12, large number of vehicles areoperated throughout the day. In site 8, 9, the flow ofvehicles is slow due to traffic signals, with the result thatpollutants emitted by vehicles enter the atmosphere and

are gradually deposited on the needle surfaces. In thesites 3, 4, 5, 13, 14 and 15, concentrations of Pb werelower (4–10mg/kg d.w.), because these sites are at

distance from the city centre. Concentrations of Pb inthe needle samples from Ustica, Botanic Garden andPiazza T. Edison are very low (0.42–0.72mg/kg d.w.),

because the stations are far from heavy metal sources.The distribution of concentrations of iron, copper and

zinc is fairly similar to that of lead. In control sitesaverage concentrations of these metals correspond to the

normal natural range regional indicated by Gonzales

Soto et al. (1996). The areas with moderate humanactivity show middle concentrations, with the greater

values referring to the stations with high human impact.As an example, average concentrations of zinc andcopper are reported (Figs. 3 and 4).

Contrary to what we observed for the above-men-tioned metals, the average concentrations of Mn and Cdremain fairly constant (15–50 and 0.034–0.11mg/kgd.w.) throughout the sites of sampling (Fig. 5).

Despite the heterogeneity of the data obtained, acomparative study of the various heavy metal concen-trations in the different sites can lead us to some

conclusions. Comparing average concentrations of themetals (Fe, Cu, Zn) with concentrations of lead (almostexclusively from anthropogenic sources), it turns out

that an increase in concentrations of the latter isaccompanied by a similar increase in the other metalconcentrations. Fig. 6 shows a significant positive

correlation between concentrations of Fe and Pb(correlation coefficient=0.72 at confidence interval ofthe 95%). The intercept value on the ordinate axisallows us to determine the natural base concentrations,

which correspond with those reported in the literature(Gonzales Soto et al., 1996). On the other hand, nocorrelation exists between concentrations of Pb–Cd

(correlation coefficient=0.06 at confidence interval ofthe 95%) and Pb–Mn (Figs. 7 and 8) (correlationcoefficient=�0.45 at confidence interval of the 95%).

This is because the natural quantities of Cd and Mn inpine leaves, which might be derived from anthropogenicsources were higher, hence there is no significantalteration in their levels.

Furthermore, confirmation of origin of lead fromanthropogenic sources is shown in Fig. 9. This shows thecorrelation between concentrations of lead in the leaves

and concentrations of benzene determined in the air byAMIA of Palermo (Amia, 1997; Autopulita, 1997), insites geographically close to our own. The point that

diverges most from the straight line refers to the samplefrom site 2. Concentrations of benzene in this sample arehigher than those predicted by the trend of the line. This

can be attributed to the fact that the benzene in site 2mainly derives from the plant for the production of citygas, situated very near the sampling site of the leaves.Lead emissions in this site are slight compared to those

of benzene and do not derive from vehicle traffic. Thetrend described is confirmed by another work in whichconcentrations of PAH (Macaluso et al., 2000) are

correlated with concentrations of lead in the leaves ofOlea europaea L.For diagnostic purposes, the biological analyses can

be correlated with the chemical tests. Macroscopicalanalyses show that the distal portions of the needlesfrom site with heavier traffic (site 7) seem stressed, dry,

with areas of necrosis, and in subpathological conditionswith characteristic twisting (Fig. 10a).

Fig. 1. Map of Palermo showing the locations of sampling

sites.


Table 2

Basic statistical parameters for pine needles samplesa

Sites (mg/kg d.w.) Average Min. Max. Med. Std. Dev. Geom. Mean

Ustica Boschetto Pb 2 1.3 2.9 2 0.69 1.7

Cd 0.035 0.02 0.055 0.021 0.015 0.018

Fe 195 175 200 150 18.2 180.1

Cu 5 5 6 6 0.47 5.05

Zn 18 17 18 15 0.471 10

Mn 20 12 38 20 6.3 20

Botanical gardens Pb 1 0.9 1.9 2 0.45 1.85

Cd 0.045 0.02 0.08 0.02 0.025 0.024

Fe 200 180 230 190 21.6 198.8

Cu 7 4 10 7 2.44 6.54

Zn 16 9 22 17 5.35 15

Mn 25 11 36 26 10.27 21.7

SS 113 Pb 5 2.9 7.1 3.27 1.75 3.94

Cd 0.056 0.015 0.09 0.02 0.034 0.033

Fe 312 205 500 230 133.56 286

Cu 7 6 10 6 1.88 7.11

Zn 35 27 43 34 6.5 34.04

Mn 61 20 134 30 51.54 43

Palazzina Cinese Pb 5 2.3 8.2 3.2 2.42 2.69

Cd 0.075 0.075 0.22 0.11 0.062 0.124

Fe 391 215 385 385 146.62 362.1

Cu 8 5 11 9 2.49 7.91

Zn 20 14 25 20 4.5 19.1

Mn 25 19 28 28 4.24 24.6

P. zza Niscemi Pb 9 1.3 13.8 10.5 5.61 8.72

Cd 0.069 0.018 0.12 0.02 0.047 0.036

Fe 410 289 486 456 86.66 400

Cu 14 11 20 13 3.85 14.1

Zn 27 18 37 25 7.8 25.5

Mn 41 40 44 40 1.88 41.2

Via Regione Siciliana Pb 14 7.7 21 15.4 5.45 10.7

Cd 0.116 0.028 0.139 0.093 0.046 0.071

Fe 577 345 720 668 165.88 549

Cu 20 18 25 19 3.09 20

Zn 24 16 33 24 6.9 20.44

Mn 21 17 24 22 2.94 21

V. A. de Gasperi Pb 16 8 24 18.3 6.53 9.61

Cd 0.078 0.046 0.11 0.08 0.026 0.076

Fe 573 190 996 532 330.3 465

Cu 22 11 37 18 10.9 19.4

Zn 43 28 58 42 12.2 40.8

Mn 27 18 38 25 8.28 26

V. Belgio Pb 20 14.2 29.5 14.1 6.96 16.7

Cd 0.042 0.039 0.1 0.044 0.028 0.056

Fe 705 356 1350 411 456.16 582

Cu 27 16 44 22 12.03 24.9

Zn 46 27 66 45 15.9 43.1

Mn 17 10 23 18 5.35 16

(continued on next page)


The analyses, carried out on the diaphanised needlesfrom site 7, reveal injury to the stomatic structuresobstructed by secondary metabolites (waxy matter)which were produced by the plant when exposed to

various pollutants (Fig. 10b).

The cryosections reveal morphological modification,which can be attributed to phosphatase accumulation,undoubtedly concentrated more heavily where colouringis more intense and where levels of pollutants are

higher.

Table 2 (continued)

Sites (mg/kg d.w.) Average Min. Max. Med. Std. Dev. Geom. Mean

P. zza Indipendenza Pb 22 14 33 18 8.042 15.5

Cd 0.068 0.068 0.076 0.076 0.004 0.075

Fe 1056 632 1800 737 527.59 943

Cu 36 26 56 27 13.9 34

Zn 49 31 81 35 22.6 44.4

Mn 23 12 38 18 8.28 20

Brancaccio Industrial Pb 19 7.3 29 7.05 9.016 4.51

Zone Cd 0.034 0.008 0.053 0.015 0.02 0.019

Fe 308 105 525 295 171.72 253

Cu 6 3 11 3 3.77 4.62

Zn 25 15 37 23 9.2 23.1

Mn 30 18 55 18 17.44 26

V. Giachery Pb 17 11 26 10.3 6.34 18.4

Cd 0.059 0.041 0.079 0.078 0.018 0.063

Fe 801 540 1152 710 257.94 360

Cu 17 13 26 14 5.9 16.78

Zn 53 29 78 51 20.3 48.6

Mn 39 28 57 33 12.65 14

V. Basile Pb 18 5.6 26.6 4.35 8.87 5.21

Cd 0.048 0.028 0.057 0.028 0.012 0.032

Fe 233 205 253 240 20.27 232

Cu 8 7 10 8 1.24 8.24

Zn 19 12 28 17 6.7 17.7

Mn 25 20 30 24 4.1 57

P. zza Tommaso Pb 2 1.3 3 0.95 0.72 1.29

Edison Cd 0.064 0 0.1 0.028 0.042 0

Fe 147 116 205 120 41.044 141

Cu 9 6 13 7 3.09 8.17

Zn 13 8.6 15 15 3.01 12.46

Mn 27 18 39 25 8.73 24

V. V.P. Martini Pb 10 6.9 15 7.2 3.56 6.91

Cd 0.06 0.023 0.098 0.084 0.033 0.057

Fe 423 340 479 450 59.87 418

Cu 10 7 14 9 2.94 9.59

Zn 20 13 29 18 6.68 19.2

Mn 50 45 50 50 4.49 50

V. F. Crispi Pb 7 3.7 11 8.5 2.98 7.1

Cd 0.064 0.04 0.088 0.041 0.022 0.057

Fe 360 337 378 366 17.21 359

Cu 18 13 25 16 5.09 17.32

Zn 17 12 21 11.8 3.81 13.96

Mn 15 12 21 14 42 26

aData are in mg/kg dry weight.


Comparisons of transversal cryosections of the apical

and basal portions of the needles, observed with amicroscope, reveal that the needles from the urban sitesare more damaged than those from site 2 (used as a

control). The latter are integral with leaning mesophyllcells, without necrosis and dysplasia. Cytochemicalstaining reveals low qualitative levels of phosphatases

(Fig. 11a).In the cryosections of the samples from site 9

(Fig. 11b–d) there is less damage to the apical and basalportions than expected from the chemical analyses.

However, there is an abnormal accumulation of meta-

bolic matter in the resin ducts, which is a clear evidence

of the environmental ‘‘stress’’. Fig. 11b and c reveals adifferent staining pattern because of their treatment at371C (b) and at room temperature (c) to show

phosphatases and tannins. Fig. 11d is a detail of theleaf portion circumscribed by the endodermis which, insome cases, accumulates metabolites (photo taken after

incubation at room temperature).The main cytological modifications induced by

pollutant stress in the apical and basal portions of thematter, from the more polluted sites, are: the collapse

of the mesophyll cells, more or less notable, with

Fig. 2. Average concentration of lead in needles of Pinus.

Fig. 3. Average concentration of zinc in needles of Pinus.

Fig. 4. Average concentration of copper in needles of Pinus.

Fig. 5. Average concentration of Cd in needles of Pinus.

Fig. 6. Pb–Fe correlation.

Fig. 7. Pb–Cd correlation.


characteristic concentration of cytoplasm along themembranes, modified cell contours, lysis of the plastids

and vacuole plasmolysis. In the distal portions of theneedles from site 7 we can also see profuse metaboliteaccumulations (coloured dark), collapsed mesophyll and

some lacunae, which represent zones of necrosis(Fig. 11e and f). The proximal portion has a lowercontent of metabolite and compact mesophyll (Fig. 11g).

Sample, in Fig. 11h, is an intermediate case (site 6), inwhich the mesophyll cells are not yet deformed but insome of them it is possible to notice their reaction to

pollutant stress, in the form of secondary metaboliteaccumulations.The previous photos show diffuse phosphatase stain-

ing, undoubtedly concentrated more heavily where the

colour is more intense, a factor which is always relatedto higher levels of pollutants.Phosphatase activity has been regarded, for long time,

as a biochemical marker of stress; in a number of cases,

an increment or decrease of phosphatases precedes theappearance of macroscopically visible damage. For thisreason, it is an important study parameter in bioindica-

tion studies (Ferrari et al., 1994). Acid phosphatases andphenols were considered as important biomarkers forthe evaluation of the phytotoxic effects that heavy

metals and other pollutants might have on the plants.Their synthesis is usually boosted in the defencemechanisms activated by plants, in response to stress.The cytochemical reaction, which highlights phospha-

tases and phenols, produces an insoluble compound,which appears in the cell cytoplasm in the form of a redor dark brown precipitate.

The morphology of the pollen structures differsaccording to the site from which they originate. Theyare perfectly mature and vital, well formed and

measuring up to 150 mm in site 2 (Fig. 12a), while they

Fig. 8. Pb–Mn correlation.

Fig. 9. Benzene–lead correlation. Fig. 10. Pinus pinea: morphology of the pine needles (a) from a

polluted site 7, and diaphanised whole needle (b) with stoma

occluded by a dark material.

Fig. 11. Cryosection of prossimal portion of the leaf control of P. Pinaster (a). Cryosection of proximal portions of the leaves of P.

halepensis var. corsiro from the site 9 (b–d). Figs. (b) and (c) reveal a different staining pattern because they were treated at 371C (b)

and at room temperature (c). Fig. (d) is a detail of the leaf portion circumscribed by the endodermis (photo taken after incubation at

room temperature). Cryosection of the apical portion (e, f) and basal portion (g) of the leaves from site 7. Cryosection of prossimal

portion of the case intermediate from site 6 (h).

"


are immature, only slightly vital and smaller in size, evensplit, with the protoplast extruding from the exine orlacking one of the two lateral sacs in sites with higher

pollution levels (Fig. 12b).

4. Discussion and conclusions

The results on the pine needles vary considerably,

regarding both the accumulation of the metals Pb, Fe,Zn, Cu in the different areas and phosphatase accumu-lation. It is likely that urbanization and high traffic are

the major reasons for high concentrations of thesemetals in the pine needles.Pollutant injury symptoms in plants are extremely

important for bioindication or biomonitoring purposes.

Foliar analysis is particularly helpful in detectingpollutants in the air; measuring their concentrations inleaves may provide information on their incidence in the

environment.The cell diagnosis of distressed plants is complicated

because the plants may respond in a similar way to a

number of anthropogenic or natural stress inducers. It istherefore useful to gather a high number of parameters

for a comparative analysis. This type of diagnosis is animportant indicator of environmental pollution when

correlated with the morphological and biochemicalanalyses. The chemical and cell tests demonstrate that,compared to Platanus and Eucaliptus and as far as

seasonal averages are concerned, the pine is an optimalbioindicator, particularly sensitive to air-dispersedpollutants (Alaimo et al., 1998).The determination of heavy metals in the needles has

allowed us to evaluate air quality over a longer period oftime than with traditional methods. This is because theneedles accumulate pollutants over their lifetime which,

in the case of the Pinus, is from around 2–3 to 4–6 yr(full maturity, before senescence). The Pinus is anappropriate means for passive monitoring of heavy

metals over wide-spread areas without the need forprevious programming (Alaimo et al., 2000).To conclude, we believe that this research should now

be extended beyond the traditional metals (Pb, Cd, etc.),since the ever-greater use of ‘‘green’’ petrol will reducetheir concentrations over the next four years.There will be a simultaneous increase in other

elements (Pt, Pd, Ru etc.) which are used in the catalyticconverters (catalytic mufflers) of vehicles, which run onlead-free petrol.

Acknowledgements

This work was funded by Sicilian Region.

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