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    Atmospheric Environment 36 (2002) 949961

    Chemical characterization and source identification/

    apportionment of fine and coarse air particles

    in Thessaloniki, Greece

    E. Manoli, D. Voutsa, C. Samara*

    Environmental Pollution Control Laboratory, Department of Chemistry, Aristotle University of Thessaloniki, 540 06 Thessaloniki, Greece

    Received 23 April 2001; received in revised form 10 September 2001; accepted 17 September 2001

    Abstract

    The distribution of air particulate mass and selected particle components (trace elements and polycyclic aromatic

    hydrocarbons (PAHs)) in the fine and the coarse size fractions was investigated at a traffic-impacted urban site in

    Thessaloniki, Greece. 7676% on average of the total ambient aerosol mass was distributed in the fine size fraction.

    Fine-sized trace elemental fractions ranged between 51% for Fe and 95% for Zn, while those of PAHs were between

    95% and 99%. A significant seasonal effect was observed for the size distribution of aerosol mass, with a shift to larger

    fine fractions in winter. Similar seasonal trend was exhibited by PAHs, whereas larger fine fractions in summer were

    shown by trace elements. The compositional signatures of fine and coarse particle fractions were compared to that of

    local paved-road dust. A strong correlation was found between coarse particles and road dust suggesting strong

    contribution of resuspended road dust to the coarse particles. A multivariate receptor model (multiple regression on

    absolute principal component scores) was applied on separate fine and coarse aerosol data for source identification andapportionment. Results demonstrated that the largest contribution to fine-sized aerosol is traffic (38%) followed by

    road dust (28%), while road dust clearly dominated the coarse size fraction (57%). r 2002 Elsevier Science Ltd. All

    rights reserved.

    Keywords: Air particles; Trace elements; Polycyclic aromatic hydrocarbons; Receptor models; Principal component analysis

    1. Introduction

    Recent concern about the health effects of air

    pollution has focused on particulate matter (PM) andseveral epidemiological studies have indicated a strong

    link between elevated particle concentrations and

    increased mortality and morbidity (Dockery and Pope,

    1994). Despite the drastic reduction of urban particulate

    pollution in cities resulted from the improvement of coal

    usage and the shift toward other fossil fuels (oil or

    natural gas) for domestic heating, the densification of

    the urban net combined with population growth and

    increasing importance of traffic have contributed to

    reinforce urban particulate pollution. Furthermore,

    particles produced by cars are much smaller than coal

    particles and found in the breathable size fraction.

    A bimodal distribution of ambient aerosol has beenreported for many urban sites (Aceves and Grimalt,

    1993; Lin et al., 1999; Lioy and Daisey, 1987). The

    coarse fraction is mainly due to crustal material, paved-

    road dust, non-catalyst equipped gasoline engines and

    background sea salts. The fine fraction is a mixture of

    primary and secondary aerosol emitted from anthro-

    pogenic rather than natural sources or formed by

    vapour nucleation/condensation mechanisms (Kleeman

    and Cass, 1998; Hildemann et al., 1991). Current

    research is focused on fine particles (PM2.5) because

    they may be transported over long distances, penetrate

    deep into the lungs and are also enriched with toxicants.

    *Corresponding author. Fax: +30-31-997747.

    E-mail address: [email protected] (C. Samara).

    1352-2310/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved.

    PII: S 1 3 5 2 - 2 3 1 0 ( 0 1 ) 0 0 4 8 6 - 1

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    Since strategies to improve ambient air quality in

    large urban centres typically involve the reduction of

    emissions from primary sources, it is useful to be able to

    observe the separate contributions that different sources

    make to the ambient particle size distribution and

    chemical composition. In recent years, receptor models

    have been proved as being important tools for separatelyvisualizing source contributions to particulate air quality

    (Lioy and Daisey, 1987; Ehrman et al., 1992; Thurston

    and Spengler, 1985; Samara et al., 1994a, b). However,

    relatively limited research has been done on the

    identification and the apportionment of size-related

    aerosol sources (Ehrman et al., 1992; Thurston and

    Spengler, 1985; Kleeman and Cass, 1998; Miranda et al.,

    1996; Swietlicki et al., 1996).

    The objectives of this paper were: (a) to investigate the

    distribution of particle mass and particle components,

    such as trace elements and polycyclic aromatic hydro-

    carbons (PAHs), in the fine and the coarse size range inan urban location, and (b) to use a suite of aerosol data

    for source identification and apportionment. The

    research was conducted at a traffic-affected site of the

    city of Thessaloniki in northern Greece, in the frame-

    work of a long-term research aiming at the investigation

    of local air particles with respect to size distribution,

    chemical composition and sources of emission (Viras

    et al., 1991; Samara et al., 1990, 1994a,b, 1995;

    Misaelides et al., 1993; Tsitouridou and Samara, 1993;

    Kouimtzis et al., 1995; Samara and Tsitouridou, 2000).

    2. Experimental

    2.1. Site description

    Thessaloniki (401620E, 221950N) is one of the most

    densely populated cities in Greece and in Europe (16,000

    inhabitants km2). It is a coastal city surrounded by

    several stable residential communities while an extended

    industrial zone is located north-westerly. Oil refining,

    petrochemical, fertilizer and cement production, non-

    ferrous metal smelting, iron and steel manufacturing,

    truck and auto painting, metal recovery facilities,

    electrolytic MnO2

    production, anodized Al, scrap metalincineration, tire production and lubricating oil recovery

    are the main industrial activities in the area.

    The climate of Thessaloniki is temperate strongly

    influenced by the sea breeze. Mean monthly values of

    relative humidity range between 47% and 80%, while

    those of temperature between 5.51C (in January) and

    281C (in August). Prevailing wind directions are N/NW

    (B25%), S/SW (B30%) and calms (B20%).

    2.2. Sampling and analysis

    Aerosol sampling took place in a residential/commer-

    cial area, at a site located aside one of the citys busiest

    roadways comprising six lanes (three each way). The

    average traffic working-day rate at this site is 2800

    vehicles/day. Although there is a continuing change

    in the size and composition of motor fleet, at the time

    of the study buses accounted for about 10% of the

    overall fleet and taxis (diesel engined) for another 10%.

    The rest were gasoline engined passenger cars, about40% fitted with catalytic converters. The sampler was

    situated on the roof of an atmospheric pollution

    monitoring station (B3 m a.g.l.) located 5 m aside the

    closest lane.

    Fine (o3mm) and coarse (310 mm) aerosol samples

    were collected on 45 working days within the period

    June 1994May 1995. A high-volume cascade impactor

    (Sierra Instruments) providing a 50% cut-off point of

    3.0 mm at 40 CFM was used for this purpose. Fine and

    coarse particles were collected on glass fibre filters

    (1000 1500 sheets and 500 700 slotted sheets, respec-

    tively). All samplings had a 24 h duration. Loaded andunloaded filters were dried in a darkened desiccator for

    24 h before weighing. Loaded filters were stored in the

    dark, in aluminium foils, at 201C until extraction and

    analysis could be completed.

    Half of each loaded filter was ultrasonically treated

    with a mixture of concentrated HNO3 and HCl for trace

    element extraction (Samara et al., 1990). Extracts were

    subsequently submitted to flameless (for Cr, Cd, Cu,

    Mn, Pb, Zn, Fe, Ni, V) or hydride generation AAS (for

    As), according to standard analytical procedures. The

    analytical precision of all elemental species was better

    than 10%.

    The other half of the filter was used for PAH analysis.

    The extraction procedure and the method of determina-

    tion are described in detail elsewhere (Samara et al.,

    1995; Papageorgopoulou et al., 1999). Briefly, filter

    samples were ultrasonically extracted with acetonitrile

    under recovery rates in the range 87102%. No further

    clean-up was performed. Concentrated extracts were

    analyzed by means of reversed-phase HPLC using

    fluorescence detection. Separation was performed on a

    5 mm Hypersil Green PAH column (100 4.5 mm2) with

    corresponding guard cartridge. The mobile phase was a

    CH3CNH2O gradient comprising 50% CH3CN over

    5 min, 50100% CH3CN between 5 and 20min and100% CH3CN for 10 min. Five pairs of excitation and

    emission wavelengths were used for detection. The

    system was calibrated with 16 PAHs, 15 compounds

    (acenaphthylene was omitted since it is only weakly

    fluorescent) specified in the EPA Method 610 (US EPA,

    1977), plus benzo[e] pyrene which is frequently used as a

    reference PAH. The precision of all identified species

    was better than 10% for peak height.

    Road dust was collected from the road side near the

    aerosol sampler. The fractiono2 mm was used for trace

    element and PAH analysis employing the same methods

    as for filter samples.

    E. Manoli et al. / Atmospheric Environment 36 (2002) 949961950

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    2.3. Data analysis techniques

    Statistical analysis of data (analysis of variance,

    correlation analysis, absolute principal component

    analysis (PCA)) was performed using the SPSS statis-

    tical software (SPSS Inc., 1998).

    3. Results and discussion

    3.1. Concentrations of fine and coarse-sized species

    Tables 1 and 2 show a breakdown of the concentra-

    tions of PM and individual particle components found

    in each size fraction, while the seasonal variability of

    concentrations is given in Table 3.

    As shown, the total (fine+coarse) particle concentra-

    tions measured were towards the highest values

    reported for urban PM10 (Turnbull and Harrison,

    2000; Ruellan and Cachier, 2001; Harrison and Jones,

    1995; Balachandran et al., 2000; Kao and Friedlander,1995). Historically, Thessaloniki has been encountered

    serious air-quality problems with air particles, with TSP

    concentrations exceeding by far the annual limit of

    150 mg m3. Although a 30% reduction has been

    obtained during the last decade, current TSP levels are

    still high. According to the Directive 1999/30/EC, from

    1 January 2001 Member States are obliged to measure

    Table 1

    Particle mass (mg m3) and elemental concentrations (ng m3) in the fine and coarse fraction

    Species Fine (N 45) Coarse (N 45) ra

    Mean Median Min Max Mean Median Min Max

    PM 97 102 15 174 30 32 6 62 0.699**

    As 1.5 1.5 0.4 2.8 0.61 0.52 0.33 1.12 0.366*

    Cr 4.8 3.6 1.2 18.8 2.9 1.9 0.4 21 0.184

    Cd 0.87 0.70 0.15 3.90 0.11 0.10 0.05 0.40 0.429*

    Cu 168 142 45 542 90 92 39 160 0.256

    Mn 23 21 8 42 24 15 1 110 0.260

    Pb 127 108 32 386 29 30 7 58 0.104

    Zn 521 441 227 1631 25 24 4 56 0.167

    Fe 297 300 80 529 291 306 52 568 0.431*

    Ni 17 15 3.2 42 6.1 5.0 1.9 13 0.497*

    V 41 27 3.0 116 6.9 5.2 1.3 27 0.024

    aSpearman correlation coefficient between fine and coarse concentrations.

    *Correlation significant at the 0.01 level.

    **Correlation significant at the 0.05 level).

    Table 2

    PAH concentrations (ng m3) in the fine and coarse fraction

    Species Fine (N 45) Coarse (N 45) ra

    Mean Median Min Max Mean Median Min Max

    Ph 1.81 1.49 0.46 7.54 0.08 0.06 0.01 0.24 0.376*

    An 0.30 0.24 0.04 1.17 0.01 0.01 0.05 0.06 0.561**

    Fl 6.15 5.02 1.00 17.24 0.12 0.10 0.02 0.27 0.574**Py 10.87 7.98 0.99 48.04 0.18 0.17 0.02 0.51 0.634**

    B[a]An 1.85 1.41 0.25 5.97 0.02 0.01 0.05 0.08 0.748**

    Chry 3.12 2.43 0.45 15.31 0.05 0.04 0.01 0.27 0.722**

    B[e]Py 9.67 5.56 1.79 74.00 0.17 0.13 0.02 1.14 0.664**

    B[b]Fl 2.77 2.40 0.53 8.96 0.04 0.03 0.01 0.14 0.696**

    B[k]Fl 1.28 1.02 0.18 5.00 0.02 0.01 0.01 0.08 0.692**

    B[a]Py 2.91 1.88 0.35 20.61 0.03 0.02 0.01 0.27 0.720**

    dB[a;h] !An 0.67 0.47 0.10 3.82 0.01 0.01 0.05 0.04 0.675**B[ghi]Pe 6.58 5.11 1.23 26.00 0.10 0.08 0.01 0.36 0.734**

    I[1,2,3-cd]Py 2.53 2.10 0.50 9.66 0.04 0.03 0.01 0.18 0.768**

    aSpearman correlation coefficient between fine and coarse concentrations.

    *Correlation significant at the 0.05 level.

    **Correlation significant at the 0.01 level).

    E. Manoli et al. / Atmospheric Environment 36 (2002) 949961 951

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    ambient PM10 and PM2.5 concentrations and prepare

    action plans for their reduction. A strict PM10 standard

    (40 mg m3 annual average) has to be met by the year

    2005 (EC, 1999), while a lower annual PM2.5 limit has

    been recommended by the European Committee for

    Standardization (20 mg m3, to be met by the year 2005,

    CEN, 1997).

    Trace elements and PAHs were found at concentra-

    tions broadly consistent with those reported for various

    urban European locations (Lee et al., 1994; Halsall et al.,

    1994; Menichini et al., 1999). Mean Pb was below the

    annual EC limit (500 ng m3), however, B[a]Py exceeded

    the current standard set in Italy (1 ng m3, Valerio et al.,

    1996). The profile of PAHs in fine and coarse aerosol has

    been previously investigated by means of diagnostic

    ratios and an overwhelming contribution of traffic

    emissions was suggested (Samara et al., 1995).

    The significant correlation found between fine and

    coarse particle mass concentrations (Tables 1 and 2)suggests similar emission and dispersion processes for

    the two modes. Significant, however, low correlation has

    been reported for other sites (Burton et al., 1996). Fine

    and coarse PAH concentrations were also strongly

    correlated, particularly those of the heavier species,

    underlying similar PAH sources in the two modes.

    Moderate correlation was found between fine and coarse

    Ni, Fe, Cd and As.

    The mass concentrations of fine and coarse particle

    fractions did not show significant seasonal variation

    (Table 3). On the contrary, trace elements exhibited

    variable seasonal trend. Concentrations of fine Cd, Cu,

    Mn, Zn, Fe and V were significantly higher in summer

    than in winter, whereas from the coarse elements only

    Zn and Fe showed significant seasonal dependence.

    When the mass proportion (ng mg1 aerosol) is con-

    sidered, significant enrichment of fine particles with Cd,

    Cu, Mn, Pb, Zn, Fe, Ni and V during summer is derived,

    while coarse particles are also enriched in summer with

    Zn and Fe. It could therefore be suggested that these

    trace elements are preferably emitted from sources of the

    warm period of the year. Concentrations of PAHs

    bound to both fine and coarse particles showed a

    significant seasonal trend with higher values during the

    cold period. The reasons for that may be seasonal (as

    their decay in the atmosphere will be slowest in the

    winter months and also semi-volatile compounds will be

    relatively enriched in particles due to lower temperatures

    and high particle concentrations) and/or source-related

    (due to the greater contribution of space heating and

    road traffic in winter). On the contrary, the enrichmentof particles with PAHs was similar throughout the year.

    Enrichment factors (EF) of trace elements in the fine

    and coarse particle fraction relative to the earths crust

    were calculated to indicate the extent of contribution of

    sources other than natural crust to the ambient

    elemental levels. The EF of an element E in an aerosol

    sample is defined as

    EF E atm=R atm

    E crust=R crust;

    where R is a reference element. There is no widely

    accepted rule for the choice of the reference element; Si,

    Table 3

    Seasonal variability of particle mass and component concentrations

    Species Fine Coarse

    Colda

    (N 34)

    Warmb

    (N 11)

    Seasonal

    variationcColda

    (N 34)

    Warmb

    (N 11)

    Seasonal

    variationc

    As (ngm3) 1.5 1.4 F 0.59 0.47 F

    Cr (ngm3) 4.5 5.9 F 3.2 1.9 F

    Cd (ngm3) 0.71 1.3 ** 0.12 0.10 F

    Cu (ngm3) 135 270 ** 85 105 F

    Mn (ngm3) 21 29 ** 27 14 F

    Pb (ngm3) 122 141 F 29 29 F

    Zn (ngm3) 408 872 ** 21 38 **

    Fe (ng m3) 262 409 ** 263 377 *

    Ni (ngm3) 15 21 F 6.4 5.2 F

    V (ng m3) 35 60 * 7.0 6.7 F

    SPAH (ng m3) 60 20 ** 0.97 0.51 *

    PM (mg m3) 101 82 F 30 31 F

    a

    15 October 15 April.b15 April 15 October.c Insignificant at the 0.05 level.

    *Significant at the 0.05 level.

    **Significant at the 0.01 level.

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    Al and Fe are usually used for this purpose. In this

    study, Fe was used as reference, while the composition

    of the earths crust was taken from Mason and Moore

    (1982).

    Results given in Fig. 1 show that Pb and Zn are the

    most enriched elements in the fine size range followed by

    Cd, Cu and As. For these elements non-crustal sourcesmay be suggested. Nevertheless, enrichment of crustal

    components in fine particles can also occur as a result of

    their transport to some distance before being removed

    from the atmosphere by deposition processes (Kao and

    Friedlander, 1995). Pb and Cu were the most enriched

    elements in the coarse size fraction. On the other hand,

    Mn and Cr showed low EF in both fractions thus

    suggesting that crustal sources predominate in both size

    ranges. Emissions from crustal sources are mostly in the

    coarse particle size range, but 1130% of the PM10crustal mass has been reported as being in the fine

    fraction (Kao and Friedlander, 1995). All elements, withimportant non-crustal sources (As, Cd, Cu, Pb, Zn, Ni,

    V), exhibited lower EF values in the coarse mode. Lower

    EF values with increasing particle size have been

    reported for Pb, Zn, Ni and Cd (Bayens and Dedeur-

    waerder, 1991; Santamaria et al., 1990; Chan et al.,

    1997). On the other hand, Eleftheriadis and Colbeck,

    1993, found increasing EFs with size for coarse V, Cu

    and Cr with highest enrichment at around 10 mm and at

    the very large sizes.

    3.2. Distribution in the fine and coarse modes

    The distribution of total particle mass and aerosol

    components in the fine size range is presented in Fig. 2

    for the cold and the warm time period. Fine particles

    accounted for 7676% of the total PM, consistently to

    reported values (5090%, Chan et al., 1997; Burton

    et al., 1996; Ruellan and Cachier, 2001; Kao and

    Friedlander, 1995). The fine particle fraction during

    the cold period was slightly, yet significantly at the 0.05

    level, higher than the corresponding summer fraction.

    Similar seasonal trend was also observed in other works

    (Chow et al., 1994; Harrison et al., 1997). Severalreasons could be responsible for that: higher strength of

    fine particle emission sources (e.g. oil combustion for

    heating and/or limitation of coarse particle resuspension

    by wet precipitations during winter), aerosol dynamics

    0

    25

    50

    75

    100

    PM As Cr Cd C

    uM

    nPb Zn Fe Ni V Ph An Fl Py

    B[]A

    nCh

    ry

    B[e]Py

    B[b]

    Fl

    B[k]F

    l

    B[]P

    y

    dB[

    ,h]A

    n

    B[gh

    i]Pe

    I[1,2,

    3-cd

    ]Py

    FIN

    EFR

    AC T

    IO N

    (% )

    COLD WARM

    Fig. 2. Distribution of particle mass and particle components in the fine size fraction.

    0.1

    1

    10

    100

    1000

    10000

    Asfine

    Asco

    arse

    Crfine

    Crco

    arse

    Cufine

    Cuco

    arse

    Cdfine

    Cdco

    arse

    Pbfine

    Pbco

    arse

    Mn

    fine

    Mn

    coar

    se

    Znfine

    Znco

    arse

    Vfin

    e

    Vco

    arse

    Nifine

    Nico

    arse

    ENRICHMENTFACTOR

    Fig. 1. EF (range and geometric mean) of fine and coarse-sized elements.

    E. Manoli et al. / Atmospheric Environment 36 (2002) 949961 953

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    (e.g. particle growth, dry and wet deposition) that

    favour particle growth during summer, transfer of soil

    dust with winds, etc. Lin et al. (1999) observed that the

    distribution of ambient particles in Chicago between the

    fine and the coarse mode was strongly dependent upon

    the wind speed: low-speed winds raised the fine particle

    fraction, whereas high-speed winds raised the coarseparticle fraction. Harrison et al. (1997) also reported

    reduction of PM2.5 by increasing wind speed as a

    dilution effect.

    All elements which may be considered originating from

    anthropogenic sources such as automotive traffic, oil

    combustion or industrial processes (Pb, As, V, Ni, Zn,

    Cd) exhibited a predominant occurrence in the fine

    particle fraction (7095%). On the other hand, elements

    such as Fe and Mn, which are also originating from

    natural sources (soil dust) were almost equally distributed

    in the two fractions. These findings are in general terms

    consistent with the majority of the reported data (Chanet al., 1997; Santamaria et al., 1990; Lin et al., 1999; Rizio

    et al., 1999; Harrison and Jones, 1995; Balachandran

    et al., 2000). Nevertheless, different distributional data

    have also been reported, as for example for Arnhem

    aerosol, where the PM2.5 fractions of Zn and Cu

    accounted only 25% and 10%, respectively, of the

    corresponding PM10 fractions (Janssen et al., 1997),

    and for aerosol in Long Beach, where the fine fraction of

    Zn was found to be only 13% (Chow et al., 1994). A

    seasonal effect significant at the 0.05 level was observed

    on the distribution of Cd, Mn, and Ni, however, with

    larger fine fractions in summer, contrarily to that

    observed for particle mass. This is inconsistent with the

    drift of the mass median diameters of trace elements (Ni,

    Cu, Mn, Fe) to higher values in summer, which was

    reported by Lyons et al. (1993) for Los Angeles.

    Particle-bound PAHs were predominantly (9699%)

    found in the fine size range despite the bimodal

    distribution of particles. The proportion of PAHs in

    fine particles was about one order of magnitude higher

    than in coarse particles. The association of PAHs with

    submicron ambient particles has been well documented

    and attributed to their emission from combustion

    processes (Cecinato et al., 1999; Poster et al., 1995;

    Venkataraman and Friedlander, 1994; Aceves andGrimalt, 1993; Baek et al., 1991). Although no major

    differences between low- and high-molecular weight

    homologues were observed, a relative increase of the

    lighter PAHs in the coarse size fraction is apparent and

    might be attributed to differences in their sources, e.g. to

    contributions from street dust which is dominated by

    Ph, Fl and Py (Aceves and Grimalt, 1993) or to their

    gas-particle partitioning behaviour (Venkataraman and

    Friedlander, 1994).

    The distribution of PAHs between the fine and the

    coarse size fractions showed similar seasonal trend with

    PM. In the cold period, the fine fraction of all PAH

    species ranged between 96.1% and 98.4%, whereas in

    the warm period it decreased slightly in the range 92.2

    97.8%. This decrease was greater for the lower

    molecular weight PAHs probably due to repartition

    from the vapour phase onto larger particles under

    certain conditions. Similar seasonal effect on the size

    distribution of ambient PAHs has also been reported byother investigators (Aceves and Grimalt, 1993; Venka-

    taraman and Friedlander, 1994; Baek et al., 1991).

    Venkataraman and Friedlander (1994) observed that,

    among the 5-ring and larger PAH species, B[a]Py

    exhibited the strongest seasonal variability. The authors

    attributed this variability to its greater reactivity in

    comparison to the other non-volatile PAHs, that may

    lead to a faster loss from the fine particle fraction due to

    reactive decay in summer. In our study, the differences

    between the winter and summer distributions for all

    non-volatile PAHs were very low (0.21.1%), however,

    the highest values were observed for the reactive B[a]Pyand dB[a;h]An.

    3.3. Particle vs. road dust composition

    Road dust has been reported as being important

    contributor to airborne PM (Rogge et al., 1993; Ruellan

    and Cachier, 2001). Resuspended by wind and vehicle-

    induced turbulences, road dust particles from multiple

    sources (automobile exhausts, lubricating oil residues,

    tire and brake lining wear, street surface weathering, leaf

    detritus, garden soil, etc.) are injected into the atmo-

    sphere and redeposited. The chemical composition of

    road dust, including trace metals and PAHs, has been

    reported by several investigators (Hildemann et al.,

    1991; Rogge et al., 1993).

    The compositional signature of local road dust is

    presented in Fig. 3 in comparison to the average

    compositional signatures of fine and coarse particles.

    All signatures were significantly correlated between each

    other, however, the signature of road dust appeared to

    be more strongly correlated to coarse particles

    (r 0:568) than to fine particles (r 0:486). Thissuggests stronger contribution of road dust resuspension

    to the coarse particle fraction.

    3.4. Source identification and apportionment

    Most source identification/apportionment applica-

    tions have been based on inorganic aerosol components,

    primarily trace elements often combined with ionic

    components and/or gaseous pollutants (Kao and Fried-

    lander, 1995; Lioy and Daisey, 1987; Ehrman et al.,

    1992; Miranda et al., 1996; Swietlicki et al., 1996). The

    potential use of PAHs as tracers of different combustion

    sources has been explored by several investigators (Li

    and Kamens, 1993; Lioy and Daisey, 1987). Three major

    disadvantages make this use questionable: (a) different

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    source categories have been found to provide similar or

    overlapping fingerprints; (b) certain PAHs (e.g. B[a]An

    and B[a]Py) have a relatively short atmospheric half-life

    under photochemical smog conditions (Lioy and Daisey,

    1987; Halsall et al., 1994; Schauer et al., 1996); (c) the

    temperature-controlled vapour-particle partitioning of

    the lower molecular weight PAHs (Ph, Fl, Py) can

    probably affect PCA. (Harrison et al., 1996; Simcik et al.,

    1999).

    In the present study, source identification and

    apportionment was performed on two separate data

    sets combining trace elements and particle-bound PAHs.The model used consisted of first determining the

    number and identity of sources using PCA with Varimax

    rotation. Source contributions were calculated next by

    using backward stepwise multiple regression of particle

    mass concentration on the absolute principal component

    scores (APCS) according to the equation:

    Y r XP

    j1

    kiAPCSi;

    where Y is the particle mass concentration, Ki is the ith

    regression coefficient, p is the number of sources and r is

    a constant representing the contribution from non-

    specified sources. A detailed description of the modelling

    approach can be found elsewhere (Thurston and

    Spengler, 1985).

    Tables 4 and 5 display the rotated PC loadings for the

    fine and coarse aerosol fractions. Four PCs were

    obtained with eigenvalues >1 summing almost 85% of

    the total variance in the fine particle data set. The first

    PC presented high loadings for the heavier PAHs (Chry

    up to I[1,2,3-cd]Py) and for Pb, thus it was interpreted as

    representing vehicle emissions (Harrison et al., 1996;

    Simcik et al., 1999). The second PC was highly loadedon Ph, Fl, Py and B[a] An while showing moderate

    loadings for benzo[b; k] fluoranthenes and I[1,2,3-cd]Py.Most of these PAHs have been reported as predominat-

    ing in diesel particles (Harrison et al., 1996; Li and

    Kamens, 1993). Therefore, PC2 was selected to represent

    the diesel emission signal. The third PC was highly

    loaded on Zn, Cu, Cd, Mn, Ni, Fe, Mn and Cr and was

    interpreted as road dust. High loadings on Fe, Mn and

    Cr reflect the bulk matrix of road dust which is soil,

    while the correlation of the other metals indicate some

    other sources as road dust, such as tire wear (source of

    Zn), brakedrum abrasion (source of Fe), vehicular

    Fig. 3. Compositional signatures of fine and coarse atmospheric particles and paved-road dust.

    E. Manoli et al. / Atmospheric Environment 36 (2002) 949961 955

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    Table 4

    Rotated principal component matrix for fine aerosol (Factor loadings smaller than 70.225 are not given)

    PC1 PC2 PC3 PC4

    As F F F 0.778

    Cr F F 0.553 0.690

    Cu F F 0.792 FCd F F 0.802 F

    Pb 0.593 F 0.601 F

    Mn F F 0.747 0.476

    Zn 0.396 F 0.801 F

    V F F 0.295 0.758

    Ni 0.279 0.320 0.712 0.229

    Fe F 0.541 0.525 0.513

    Ph 0.232 0.876 F F

    An 0.640 0.510 F F

    Fl 0.445 0.790 0.294 F

    Py 0.376 0.843 F F

    B[a] !An 0.551 0.718 F F

    Chry 0.921 0.296 F F

    B[e]Py 0.920 0.290 F F

    B[b]Fl 0.893 0.395 F F

    B[k]Fl 0.886 0.357 F F

    B[a]Py 0.960 F F F

    dB[a;h]An 0.948 F F FB[ghi]Pe 0.804 0.401 F F

    I[1,2,3cd]Py 0.937 0.301 F F

    Variance % 37.0 17.8 17.3 12.7

    Source type Vehicle Diesel Road dust Fuel oil

    Table 5

    Rotated principal component matrix for coarse aerosol (factor loadings smaller than 70.225 are not given)

    PC1 PC2 PC3 PC4 PC5

    As 0.439 F 0.448 0.543 0.394

    Cr F F 0.730 F 0.630

    Cu F F 0.396 0.872 F

    Cd F F F 0.644 F

    Pb 0.297 F 0.617 F F

    Mn F F 0.554 0.696 F

    Zn F F 0.836 F F

    V F F 0.725 0.252 F

    Ni 0.338 0.387 F F 0.602

    Fe F F 0.878 F F

    Ph 0.340 0.818 0.291 F F

    An 0.834 0.405 F F FFl 0.477 0.806 F F F

    Py 0.354 0.812 0.251 F F

    B[a] !An 0.423 0.630 0.424 F F

    Chry 0.951 F F F F

    B[e]Py 0.847 F F F F

    B[b]Fl 0.857 F 0.225 F F

    B[k]Fl 0.902 0.353 F F F

    B[a]Py 0.971 0.266 F F F

    dB[a;h]An 0.954 F F F FB[ghi]Pe 0.842 0.368 F F F

    I[1,2,3-cd]Py 0.926 0.233 F F F

    Variance % 37.4 14.0 13.3 13.3 7.2

    Source type Vehicle Diesel Road dust Industrial Fuel oil

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    Fig. 4. Mean source contribution to fine aerosol.

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    Fig. 5. Mean source contribution to coarse aerosol.

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    emissions (source of Pb), diesel engines (source of Cu),

    etc. (Samara et al., 1994a; Swietlicki et al., 1996;

    Thurston and Spengler, 1985; Hildemann et al., 1991).

    The fourth PC was loaded on V, As, Fe, Mn, Cr and

    moderately on Ni. Arsenic is usually considered as coal

    burning tracer, while oil combustion has been reported

    as been characterized primarily by Ni and V andsecondarily by Fe and Mn (Harrison et al., 1996;

    Swietlicki et al., 1996; Miranda et al., 1996; Samara

    et al., 1994a). Given that coal burning in our area is very

    limited occurring only in few small-sized industrial

    activities (e.g. non-ferrous metal smelters), whereas oil

    burning is used for both space heating and industrial

    purposes, PC4 was selected to represent oil combustion.

    In the coarse particle data set, five PCs were obtained

    with eigenvalues >1 explaining 85% of the total

    variance. Four of them, PC1, PC2, PC3 and PC5

    showed similar loading patterns with PC1, PC2, PC3

    and PC4 of the fine particle data set, thus they wereinterpreted as vehicle, diesel, road dust and oil combus-

    tion source types, respectively. The fourth PC was

    primarily loaded on Cu, Cd, Mn and As and secondarily

    on V. This PC was interpreted as representing emissions

    from several metallurgical activities occurring in the

    industrial area (Samara et al., 1994a).

    The multiple regression of aerosol and individual

    constituent masses on APCS exhibited good correlation

    between observed and predicted values with correlation

    coefficients in the range 0.680.99. In cases that a

    regression constant significant at the 0.05 level was

    derived, it was interpreted as representing unidentified

    sources. Mean source contributions to fine and coarse

    aerosol are shown in Figs. 4 and 5, respectively. Results

    showed that the largest contributor to aerosol mass in

    the fine size fraction is traffic with a total contribution

    38%, whereas road dust clearly dominated the coarse

    size fraction. Vehicular emissions appeared to be the

    unique source of fine-sized PAHs, whereas coarse-sized

    PAHs were additionally originated from road dust, coal

    fired non-ferrous metal smelters and oil combustion.

    Road dust was found to be stronger contributor to fine

    and coarse Pb than vehicular emissions. These findings

    are different from those reported by Harrison et al.

    (1996) for Birmingham, where road dust was unexpect-edly found to be the major contributor to PAHs, while

    direct traffic emissions to Pb. As mentioned, sometimes

    these two sources are incompletely separated by PCA as

    road dust particles are resuspended mainly due to

    vehicular movements (Harrison et al., 1996; Okamoto

    et al., 1990). Lin et al. (1999), using B[e] Py as an

    indicator, estimated the contribution of traffic to the

    concentration of 47 ring PAHs in Birmingham city

    centre at 8082%, while 6084% of the total PAH traffic

    emissions was attributed to diesel vehicles. On the

    contrary, non-catalytic gasoline vehicles were found to

    be by far the largest contributor of PAHs in Los Angeles

    basin, despite the overwhelming contribution of diesel

    exhausts to the fine mass (33% vs. 6% for gasoline

    vehicles) (Schauer et al., 1996).

    The source apportionment findings of this study are in

    general agreement with the majority of reported data,

    which point out traffic emissions and traffic-induced

    road dust resuspension as the major sources of fineurban aerosol with sum contributions up to 80%

    (Okamoto et al., 1990; Miranda et al., 1996, 2000;

    Harrison et al., 1996; Alonso et al., 1997; Schauer et al.,

    1996).

    The source types identified in this study are similar to

    those found in a previous receptor modelling exercise

    carried out in Thessaloniki, the relative contribution of

    sources are, however, different since previous modelling

    was not oriented to specific aerosol fractions but to total

    suspended particles (Samara et al., 1994a, b). It is

    believed that current apportionment results will be

    useful to the local authorities to regulate air PM.

    4. Conclusions

    The distribution of particle mass, trace element and

    particle-bound PAH concentrations in the fine

    (o3.0 mm) and coarse (>3.0mm) size fractions was

    investigated at a trafficked-site in Thessaloniki, Greece.

    7676% on average of the total ambient aerosol mass

    was distributed in the fine size fraction. Fine-sized trace

    elemental fractions ranged from about 50% for Fe and

    Mn up to 95% for Zn. The fine-sized PAH fractions

    were between 95% and 99% for all species.

    The size distribution of aerosol mass exhibited

    significant seasonal dependence with a shift to larger

    fine fractions in winter. Similar seasonal trend was

    exhibited by PAHs, whereas larger fine fractions in

    summer were shown by trace elements.

    The compositional signature of local paved-road dust

    was found to be strongly correlated to that of coarse

    particles thus suggesting significant contribution of

    resuspended road dust to this particle fraction.

    A multivariate receptor model (multiple regression on

    absolute principal component scores, MR/APCS) ap-

    plied on separate fine and coarse aerosol data enabledmajor source types to be identified and apportioned:

    gasoline and diesel emissions, road dust, metallurgical

    processes and oil combustion. Traffic was found to be

    the largest contributor to fine-sized aerosol (total

    contribution 38%) followed by road dust (28%). Road

    dust clearly dominated the coarse size fraction (57%).

    Acknowledgements

    The authors wish to thank the Secretariat for Science

    and Technology, Ministry of Development, and the

    E. Manoli et al. / Atmospheric Environment 36 (2002) 949961 959

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    Organization for the Master Plan Implementation and

    Environmental Protection of Thessaloniki for research

    funding. They are also grateful to Prof. V. Simeonov,

    Kliment Ohridski University, Sofia, Bulgaria for

    useful comments on receptor modelling.

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