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SIZE DISTRIBUTIONS OF PAHs IN AMBIENT AIR PARTICLES OF
TWO AREAS OF LAS PALMAS DE GRAN CANARIA
JOSÉ A. LÓPEZ CANCIO∗, ANTONIO VERA CASTELLANO, SERGIO SANTANA
MARTÍN and JUAN F. SANTANA RODRÍGUEZ
Escuela Técnica Superior de Ingenieros Industriales, Universidad de Las Palmas de Gran Canaria,
Campus Universitario de Tafira, 35017 Las Palmas de Gran Canaria, Canary Islands, Spain
(∗ author for correspondence, e-mail: jlopez@dip.ulpgc.es)
(Received 3 December 2002; accepted 14 November 2003)
Abstract. The size distribution of 14 polycyclic aromatic hydrocarbons (PAHs) present in particulate
aerosol in two different areas of the city of Las Palmas de Gran Canaria was investigated in May
2002. One of the study areas (Bravo Murillo) was under the influence of heavy traffic and the other
(Pedro Lezcano) under that of small-scale industries of various nature. The average concentration
of total suspended particulates (TSP) at Bravo Murillo (35.2 µg m−3) was roughly one-half that at
Pedro Lezcano (73.6 µg m−3); the former, however, exhibited a higher PAH content (sum of PAHs:
6.6 ± 1.8 versus 5.1 ± 3.9 ng m−3). The aerosol size partition of total PAHs at Bravo Murillo, with
a unimodal peaking at 0.08–0.3 µm, was completely different from that at Pedro Lezcano, where
accumulation observed in the 3.8–7.4 µm range suggests the ageing of particles occurred, with PAHs
have redistributed according to surface extension of particles.
Keywords: aerosol, Gran Canaria, polycyclic aromatic hydrocarbons, size distributions, total sus-
pended particulates
1. Introduction
The city of Las Palmas de Gran Canaria lies along the narrow coastal strip in the
northeastern end of the island of Gran Canaria – one of the seven in the Canary
archipelago. The city centre and the island’s north and south are connected by a
highway built on land, reclaimed from the sea. With a population of 355,000 and
a density of 3,520 inhabitants per square km, Las Palmas is among the eight most
populated Spanish cities.
The city has two areas of special interest with respect to the impact of pollution
on the population. In the downtown area, heavy vehicle circulation and virtual
absence of industries, render road traffic is the principal source of anthropogenic
pollution (Vera, 1992). In the south end, where traffic is light, other anthropo-
genic sources such as small industries, a thermal power generator and a water
desalination plant release materials that are expected to produce a health impact.
The purpose of this work was to compare anthropogenic aerosol, collected at
both sites, to collect information about atmospheric pollution, suitable for imple-
menting corrective actions. Taking into account that all the above sources releases
Water, Air, and Soil Pollution 154: 127–138, 2004.
© 2004 Kluwer Academic Publishers. Printed in the Netherlands.
128 J. A. LÓPEZ CANCIO ET AL.
polycyclic aromatic hydrocarbons (PAHs), many of which are proven carcinogens,
and since toxicity is easier exploited when associated to smallest particles (La Voie
et al., 1979; Dipple et al., 1984), our comparison was based upon size distribution
behaviours.
2. Experimental
2.1. DESCRIPTION OF THE SITE
We determined the atmospheric particle-associated PAHs in two areas of the city of
Las Palmas de Gran Canaria, namely: a) in Bravo Murillo, a downtown street with
heavy motor vehicles traffic (80,000 cars each day), of which a high proportion is
diesel propelled (taxis, buses and trucks), and b) in Pedro Lezcano, in the south
end, nearby fixed emission sources (a thermal power plant, small industries and a
water desalination plant). The test station at Bravo Murillo was located on the roof
of a building about 10 m high in that street. The other station was located on the
roof of a school lying about 2 km SW from the nearest anthropogenic pollution
sources (viz. a thermal power generator and a water desalination plant) (Fig. 1).
The sampling sites were located near the coast (approximately 2 km). During the
sampling the trade winds (NE) were predominants.
2.2. SAMPLING AND ANALYSIS
Air samples were collected through a high-vol pumping system (CAV-P; MCV,
Collbato, Spain) equipped with a five stage cascade impactor (Sierra model 235,
Sierra Instruments Inc., USA). The sampling periods were 24 h (air volume 1200
m3). Aerosol particles were separated into six size fractions on glass-fiber filters
according to the following equivalent cutoff diameters at 50 % efficiency: first stage
> 7.4 µm, second stage 7.4–3.8 µm, third stage 3.8–2 µm, fourth stage 2–0.9 µm,
fifth stage 0.9–0.3 µm, and backup filter < 0.3 µm. After sampling, all filters were
wrapped in aluminium foil (Halsall et al., 1993; Gustafson and Dickhut, 1997) and
stored at –20 ◦C (Aceves and Grimalt, 1993; Allen et al., 1996; Baek, 1988) until
analysis in the laboratory. Samples were collected on 7 days between May 6 and
12, 1999.
Three extraction (30 min each) of each particulate sample were made ultrason-
ically (Bransonic Inc., model 2510) with dichloromethane (Nielsen, 1996; Escrivá
et al., 1991; Fromme et al., 1998). The extracts were concentrated to 2 mL in
a rotary evaporator at 35 ◦C and 800–810 mbar. The concentrated extracts were
fractionated by column chromatography (silica gel, 2.0 g) (Müller et al., 1998).
First, aliphatic compounds were cut off by eluting with n-hexane; then, PAHs were
collected (using dichloromethane), nitrogen concentrated to almost dryness and
redissolved with dichloromethane (20 %) and acetonitrile (80%). Recovery factors
were determined by spiking filters with standard NIST SRM 1647c. The recovery
SIZE DISTRIBUTIONS OF PAHs IN AMBIENT AIR PARTICLES 129
 
 
Figure 1. Location of monitoring stations. A. Power station and desalination plant. B. Highway (50
m above sea level).
factors of this extraction and fractionation process lies in the order of 90–100 %
for the 4-ring and larger PAHs.
The samples were analyzed by GC coupled to mass spectrometer (GC-MS).
These analyses were performed with a Shimadzu GC/MS system consisting of an
GC-17A gas chromatograph and Shimadzu QP-5000 mass spectrometer. A 30 m ×
0.25 mm i.d. HP-5MS (film thickness 0.25 µm) was used. The GC analyses were
performed with an oven temperature program from 50 ◦C to 300 ◦C at 8 ◦C/min;
injector and transfer line temperatures of 300 and 230 ◦C, respectively; and helium
was the carrier gas. The injector was in the splitless mode.
Compound identification was based on the GC-MS data and co-injection with
authentic standards. Quantitation was performed from the GC profiles using the ex-
ternal standard method. Samples and standards were repeatedly injected until less
than 5% dispersion in the area measurements was observed. The aromatic hydro-
carbons were quantitated with a standard containing naphthalene (Naph), acenaph-
thene (Ace), acenaphthylene (Acy), fluorene (Flu), phenanthrene (Phe), anthra-
cene (Anth), fluoranthene (Flt), pyrene (Pyr), benzo[a]anthracene (BaA), chrysene
130 J. A. LÓPEZ CANCIO ET AL.
Figure 2. Lundgren size distributions of aerosol collected at B. Murillo and P. Lezcano stations.
(Cry), benzo[b]fluoranthene and benzo[k]fluoranthene (BbkF), benzo[a]pyrene (BaP),
dibenz[a, h]anthracene, benzo[g, h, i]perylene (BgP), indeno [1,2,3-cd]pyrene (Ind).
Benzo[b]fluoranthene and benzo[k]fluoranthene with similar elution times were
quantitated together.
3. Results and Discussions
3.1. SUSPENDED PARTICLES (TSP)
Table I shows the concentrations of two cumulative atmospheric particle fractions
established according to aerodynamic diameter [viz. fine (< 2 µm) and coarse (>
2 µm)] at the two sampling sites, alongside their median mass diameters (MMD,
µm) and geometric standard deviations (GSD).
SIZE DISTRIBUTIONS OF PAHs IN AMBIENT AIR PARTICLES 131
Figure 3. Particulate PAH content in the size fractions separated by the cascade impactor.
TABLE I
Size distribution of particulate aerosol samples from the two test locations (concentrations are given
in µg m−3)BRAVO MURILLO PEDRO LEZCANO
Fine Coarse Fine Coarse
May Conc MMD GSD Conc MMD GSD Conc MMD GSD Conc MMD GSD
6 33.8 0.33 1.39 16.6 6.30 1.59 38.9 0.33 1.36 23.5 6.14 1.60
7 20.7 0.39 1.69 16.1 5.89 1.60 35.4 0.39 1.63 34.0 5.75 1.78
8 12.1 0.34 1.53 9.5 5.49 1.65 45.4 0.35 1.50 37.8 6.07 1.58
9 10.9 0.37 1.62 15.7 5.71 1.11 13.0 0.39 1.70 35.2 6.21 1.58
10 13.2 0.35 1.50 16.2 5.47 1.57 22.5 0.41 1.70 32.0 5.84 1.62
11 14.8 0.35 1.50 20.1 5.80 1.61 26.4 0.46 1.79 44.7 5.68 1.63
12 20.8 0.36 1.53 25.4 5.49 1.60 29.7 0.46 1.76 97.6 5.33 1.39
As can be seen, each particle group at Bravo Murillo (BL) accounted for roughly
one-half of total suspended matter (TSP); the median mass diameters for fine and
coarse aerosol were 0.33–0.39 and 5.47–6.30 µm, respectively. At Pedro Lezcano
(PL), with an MMD of 0.33–0.46 and 5.33–6.21 µm for the fine and coarse aerosol
fraction, respectively, the latter seemingly prevailed over the former (over all on
May 12). The concentrations of both fractions were rather different between the
two stations, reaching 35.2 µg m−3 in total in downtown and about twice (73.6 µg
m−3 ) in the south end. A special concern was attributed to samples collected on
132 J. A. LÓPEZ CANCIO ET AL.
Figure 4. Lundgren size distributions of PAHs collected at B. Murillo and P. Lezcano stations.
May 12, when a change of direction of prevailing winds carried haze from Africa
and affected both areas. At PL, more exposed to the winds, concentration of coarse
particles was 183% higher than the mean value, whereas at B.M. the increment was
only 62%.
To better envisage the size distribution of particulate aerosol in the two areas,
the Lundgren diagrams of Figure 2 were constructed by taking 0.08 µm and 30 µm
as the lower and upper limits (diameter), respectively. The lower limit was based
on the results of urban aerosol studies involving size-fraction partitioning devices
of 0.01–0.1 µm resolution (Whitby et al., 1972); the upper limit was taken from
reported data for aerosols of different origins (Slinn, 1983). As can be seen from
the Ludgren diagrams. TSP, as in other world areas (Aceves and Grimalt, 1993;
Baek, 1988; Warneck, 1988; Holsen et al., 1991), exhibited a bimodal distribution
at both locations, with the modes in correspondence of the same size ranges (viz.
0.08–0.3 and 3.8–7.4 µm). However, the two distributions were qualitatively and
SIZE DISTRIBUTIONS OF PAHs IN AMBIENT AIR PARTICLES 133
 
Figure 5. Size distributions and mass median diameters of 3-ring PAHs at B. Murillo and P. Lezcano
stations.
quantitatively different. Thus, the two modes were rather equal in the city centre,
similarly to other urban areas (Aceves and Grimalt, 1993); this suggests that most
suspended dust comes from vehicular exhaust and resuspended particulate matter
from paved roads and surfaces since unbuilt ground areas are rather scant. By
contrast at Pedro Lezcano, the mode corresponding to coarse particles (3.8–7.4
µm) prevailed, so a wider variety of emission and the presence of unbuilt areas
affected to influence the site. The May 12 did not modify this behaviour, although
the main mode (3.8–7.4µm) undergo an increment of 55%.
134 J. A. LÓPEZ CANCIO ET AL.
Figure 6a. Size distributions and mass median diameters of 4-ring PAHs at B. Murillo and P. Lezcano
stations.
Figure 6b. Size distributions and mass median diameters of 4-ring PAHs at B. Murillo and P. Lezcano
stations.
SIZE DISTRIBUTIONS OF PAHs IN AMBIENT AIR PARTICLES 135
Figure 7. Percentage of PAH associated with coarse (> 2µm) and fine (< 2µm) particles at B.Murillo
station.
TABLE II
Mean and range for total concentrations (ng m−3) of all determined PAHs at BM and PL
PAH Bravo Murillo Pedro Lezcano
Range (ng m−3) Mean (ng m−3) Range (ng m−3) Mean (ng m−3)
Naph 0.004 – 0.036 0.013 N.D. – 0.062 0.025
Acy N.D. – 0.002 0.002 N.D. —-
Ace N.D. – 0.015 0.007 N.D. —-
Flu 0.115-0.551 0.314 0.056 – 0.770 0.427
Phe 0.195-0.939 0.467 0.115 – 1.032 0.436
Anth 0.049–0.141 0.097 0.081 – 0.800 0.309
Flt 0.798–4.155 2.587 0.785 – 10.588 3.409
Pyr 0.335–0.535 0.404 0.066 – 0.383 0.185
Cry 0.171–0.278 0.228 0.013 – 0.065 0.039
BaA 0.149–0.412 0.272 0.012 – 0.138 0.062
BbkF 0.624–1.874 1.384 N.D.- 0.637 0.180
BaP 0.117–0.326 0.190 N.D.- 0.104 0.030
Ind 0.164–0.299 0.238 N.D.- 0.262 0.095
BgP 0.281–0.646 0.338 N.D.- 0.188 0.070
∑
PAH 4.037–8.672 6.602 2.218–13.645 5.143
136 J. A. LÓPEZ CANCIO ET AL.
3.2. POLYCYCLIC AROMATIC HYDROCARBONS
Dibenzo(ah)anthracene was the sole PAH that could not be quantified at either
station, while acenaphthylene or acenaphthene were below detection limit at PL.
The average concentration (arithmetic mean ± standard deviation) of total PAHs
in the particulate phase (�PAHs) was lower at the south end (5.1 ± 3.9 ng m−3)
– despite the atmospheric particles content – than in the city centre (6.6 ± 1.8
ng m−3). A comparison of the amount of hydrocarbon (ng) per microgram of
particulate matter present at each impaction stage in both areas (Fig. 3) reveals
that the two aerosols differ essentially in the PAH content in the two least stages
(5th and 6th), which is much higher in the city centre. There BaP, Ind and BgP
were only detected in the smallest particles (backup filter); by contrast at Pedro
Lezcano, these hydrocarbons were associated to particles collected in all impaction
stages corresponding to less than 2 µm of diameter. Compared to PL, BP was
characterized by heavier contents of BaP, InP, BgP, Py, Chr, BaA and BbkF (ratios
ranging from 2.2 to 7.7). Instead, light PAH exhibited higher concentrations at
Pedro Lezcano, with a ratio of 0.25, 0.73, 0.31 and 0.76 for naphthalene, fluorene,
anthracene and fluoranthene, respectively. Phenanthrene levels were similar at both
locations.
Figure 4 shows the normalized size distribution of total PAHs at the two sta-
tions. As can be seen, �PAHs exhibited a unimodal distribution in the city centre,
the maximun corresponding to 0.08–0.3 µm range. That indicates fresh vehicle
emissions dominated the PAHs and presence in the atmosphere, released with
small particles. At Pedro Lezcano, the PAH size distribution peaked in the 3.8–7.4
µm range. This finding is more consistent with those usually found in semi-rural
areas, far from major emission sources, where PAHs are associated to large aer-
osol particles (Aceves and Grimalt, 1993; Allen et al., 1996; Venkataraman and
Friedlander, 1994).
The examination of individual PAHs revealed some distribution pattern differ-
ences between the two stations. Most PAHs at Bravo Murillo exhibited a size dis-
tribution similar to that of �PAHs, except three-ring hydrocarbons (viz. fluorene,
phenanthrene and anthracene), and fluoranthene – with MMDs from 1.19 µm
(fluorene) to 1.31 µm (anthracene) –. In that case, a second mode occurred in the
3.7–7.4 µm range (Figs. 5 and 6). This mode could be due to growth of combustion
particles. Otherwise, the proportions of all PAHs in the coarse and fine aerosol
fractions would be similar (Allen et al., 1996), rather than drop to zero or near-
zero for the hydrocarbons of molecular weight above 252 (see Fig. 7). Besides that,
most light hydrocarbons (molecular weight < 202) were more or less uniformly
distributed between the coarse and fine aerosol, (39–44% in the former). Their
presence in the coarse fraction is possibly relieved to the contribution coming from
of street dust (Bidleman, 1988), which contains phenanthrene, fluoranthene and
pyrene predominantly (Takada et al., 1990).
The normalized size distributions of individual hydrocarbons at Pedro Lezcano
SIZE DISTRIBUTIONS OF PAHs IN AMBIENT AIR PARTICLES 137
were very similar to that of �PAHs for phenanthrene, anthracene, pyrene and fluor-
anthene. Fluorene and chrysene were more uniformly distributed between sizes,
whereas BaA exhibited a bimodal distribution. PAH were more abundant in the
larger particles, we think that they were associated to particles mainly released at
this site, even though similar behaviorhas been observed for light weight PAHs in
tunnels and in urban air (Miguel et al., 1998; Marr et al., 1999; Eiguren-Fernández
et al., 2003).
It is well known that the light PAHs are distributed between the gas and particu-
late phase, and that their particulate concentrations increase with suspended matter
(Nielsen, 1996). Thus, the higher concentrations of particulates at PL could explain
the finding that the ratio between the concentrations of the lighter hydrocarbons
(molecular weight < 202) and the heavy ones (molecular weight > 202) was much
higher there than that in the city centre (viz. 10.1 versus 1.46).
PAHs volatility seems to affect concentrations detected at the two sites, espe-
cially at PL. Considering that the 4-ring PAH are probably at least 50% in the
gas-phase, digits found for Phe, Flt and Pyr, very rich in diesel samples, reveal
not only the influence of diesel emissions on the city, but also a basic difference
of the two aerosols. BM was dominated by fresh vehicle emissions, whereas at
PL prevailed aged particles, on which PAH have redistributed according to surface
extension of particles.
Acknowledgements
The authors wish to express their thanks to Prof. Janet Arey, University of Califor-
nia, Riverside, for her kind and helpful discussions to improve this paper.
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