© by PSP Volume 16 – No 8. 2007
Fresenius Environmental Bulletin
PARTICULATE MATTER (PM10 AND PM2.5)
FROM DIFFERENT AREAS OF PUERTO RICO
Adriana Gioda, Ulda Peréz, Zenaida Rosa and Braulio D. Jimenez-Velez*
Center For Environmental and Toxicological Research, University of Puerto Rico,
Medical Sciences Campus, Biochemistry Department, School of Medicine, PO Box 365067, San Juan, PR, 00936-5067
SUMMARY
Fine (PM2.5) and coarse (PM10) particles were characterized in different sites of Puerto Rico during 2000 to 2003.
The sites were established in urban areas (Guaynabo, Salinas
and Vieques) and in a reference site (Fajardo) at the east
coast. Particulate matter (PM) samples were collected in
Teflon and quartz filters then weighed and processed. PM
mass concentrations in Teflon filter were determined gravimetrically and estimated for quartz. Samples were digested for metal analyses with appropriate field blanks.
Seven to eight metals (Cd, Co, Cu, Fe, Ni, Pb, V and Zn)
plus arsenic (As) were analyzed in each sample by Atomic
Absorption Spectroscopy. Average PM10 levels were around
25 µg m-3 in all sites being, lower than the limits established
by USEPA (50 µg m-3). The annual average level of PM2.5
in Guaynabo was 11.6 µg m-3 versus 8.5 µg m-3 in Fajardo.
Most of the metals were present at higher levels in the urban
sites (Guaynabo, Vieques and Salinas) than at the reference
site (Fajardo). All species analyzed in PM2.5, except Fe,
were significantly higher at Guaynabo when compared to
Fajardo. Ni and V exhibited the highest metal concentrations (Ni = 17 ng m-3 and V = 40 ng m-3) in Guaynabo. Fe
showed stronger relationships between PM at each site suggesting their release from similar sources at that particular
location, probably due to Sahara dust.
matter is associated with epidemiological studies which has
shown an increased mortality, morbidity, decreased lung
function [1,3], asthma, bronchitis and lung cancer [4] and is
pertinent to the development of chronic diseases as pneumoconiosis and emphysema [4].
Recent studies carried out in vitro or in vivo using animal models, showed strong correlation between metal content from particulate matter and pulmonary toxicity [5,6].
Trace metals distributed widely throughout the lung on
particles could catalyze the formation of oxidants within the
lung, which in turn produce tissue damage [7,8]. Laboratory
studies show that some metals (Mn, Cd, Cu, Pb and Zn) are
initiators or promoters of carcinogenic activity in animals
[9]. Pollutant metals may accumulate in the fatty tissues of
the body and in the circulatory system, affecting the central
nervous system and internal organs [9].
This is the first integrated study developed in Puerto
Rico to evaluate levels of PM10 and PM2.5 and their composition. Previous studies determined the concentration and
characteristic of particulate matter in only one city (Ponce)
in the south of the Puerto Rico Island [10-12].
The objective of this paper is to integrate all available
data on particulate matter in Puerto Rico and expand the
knowledge of the size distribution of particles contaminated
with heavy metals.
KEYWORDS: heavy metal, arsenic, air pollution, Sahara dust,
respiratory uptake.
MATERIAL AND METHODS
Sampling
INTRODUCTION
Airborne particulate matter is one of the most important constituents of atmospheric pollution. Consequently,
exposure to airborne particles is a common event. The effects on health caused by particulate matter depend mainly
on particle size, but also a number of factors such as their
content of toxic substances, their solubility in biological
fluids, total human exposure, and others [1, 2]. Particulate
Air samples were obtained from Salinas, Vieques,
Guaynabo and Fajardo (reference site). Salinas is a small
town in the southern coast where the Aguirre Thermoelectric Plant is located. Vieques is an island where a marine is
placed. Guaynabo is a city in the metropolitan area with
urban and industrial activities. Fajardo was chosen as the
reference site, because it is located in an ecological reserve
at the east coast with no human activities upwind from the
station. Air samples (PM10) were obtained from Salinas
during August 2002 to May 2003, Vieques during June to
861
© by PSP Volume 16 – No 8. 2007
Fresenius Environmental Bulletin
December 2001 and April 2002 and Fajardo from June 2001
to May 2003. The PM2.5 samples were collected in Guaynabo and Fajardo beginning in November 2000 and lasting
in September 2001. Air samples were collected using a
Partisol Plus Model 2025 sequential PM10 air monitor that
collects airborne particles on a 47 mm Teflon filter. All
samples were collected on a weekly basis at a flow rate of
16.7 L min-1 for 72 hours period. PM2.5 was collected on
quartz filters using the Fine Particulate Chemical Speciation Air Sampler (RAAS 2.5-400) from Andersen Instruments Inc. The flow meter (FM) units were set to intake air
at 17 L min-1 (FM 1 and 4), 4.1 L min-1 (FM 2 and 5) and
3.5 L min-1 (FM 3 and 6).
Each Teflon filter was placed and stored flat on a clean
Petri dish during and after conditioning, weighing and storage. Pre-sampling and post-sampling weigh of filters were
performed in an electronic microbalance (M-220D, Denver
Instruments, Denver, CO, USA) with a sensitivity of five
decimal points. All filters (either with or without mass) were
stably weighed until a constant weight was achieved, following the USEPA methodology [13].
Reagents and solutions
HNO3 Trace Metal Grade (Fisher Scientific, Pittsburg,
PA), stock standard solution 1000 mg L-1 (Mixed standard
Perkin Elmer) and QCI 700 and 701 Ultracheck Metals
Samples (Ultra Scientific, North Kingston, RI) were used.
The modifiers used were Pd (Perkin Elmer AA modifier
solution 10 g L-1), Mg (Perkin Elmer AA modifier solution
10 g L-1) and NH4 (Perkin Elmer AA modifier solution 10%
NH4H2PO4). All solutions were prepared fresh on a dailybasis.
Analyses
Teflon filter samples (PM10) collected were analyzed individually. For PM2.5, a composite sample (around 4-8 quartz
filters per composite) combined filters from either FM 2
or FM 5 of each month. The digestion process was performed by adding nitric acid with ultra pure water. Extraction was conducted on a hot plate, heated and refluxed at
90°C ± 5°C for 2 hrs. Acidified extracts were stored in
polypropylene nalgene bottles until used for analysis [14,
15].
ated using spike blanks of known metal concentration and
a standard reference material (Urban Particulate Matter
SRM 1648, National Institute of Standards and Technology
(NIST), Gaithersburg, MD). The recovery efficiency was
calculated on the base of the heavy metal concentration
reported for the SRM [14,15]. The blanks were processed
simultaneously and were handled in an identical manner as
the samples. The average heavy metal and arsenic values in
the blanks were subtracted from the levels obtained in each
samples.
Statistical analyses were performed using the computerized software program “GraphPad Prism” version 4.0a.
The t-test analyses were performed to establish statistical
differences between the means of particulate matter, metal
and arsenic concentrations from sites at the 95% confidence
interval. Linear regressions were performed between trace
elements and particulate matter analyzed per site in order
to elucidate possible relationships among them.
RESULTS AND DISCUSSION
Particulate Matter
Average annual concentrations of PM10 and PM2.5 from
2000 to 2003 at different sites in Puerto Rico are shown in
Figure 1. Average annual concentration of PM2.5 in Guaynabo was 11.6 µg m-3 and Fajardo 8.5 µg m-3. The levels
found for PM10 in Fajardo (2001-2003) was 25.5 µg m-3
(n = 83; standard error ± 1.2), while Vieques (2001-2002)
and Salinas (2002-2003) were 23.6 µg m-3 (n = 44; standard
error ± 3.4) and 22.9 µg m-3 (n = 43; standard error ± 3.8),
respectively. The greatest difference in PM annual concentration between sites was observed for PM2.5 (P value
0.0013). Differences between urban and reference sites were
not as marked for PM10. PM10 concentrations at Guaynabo
were obtained from the Environmental Quality Board. The
sampling period was from April to July 2001. The PM10
average concentration at Guaynabo was 41.4 µg m-3 (n = 97;
standard error ± 1.9) with a maximum of 106.2 µg m-3
(during a Sahara event on July 3, 2001).
Metals were analyzed by Atomic Absorption (AA) using a Perkin-Elmer AA Spectrometer Model AAnalyst 800
(Norwalk, CT, USA). USEPA [16] methods 7060A, 7131A,
7201, 7211, 7381, 7421, 7521, 7911 and 7951 were used for
the following elements: As, Cd, Co, Cu, Fe, Pb, Ni, V and
Zn, respectively.
30
25
20
*
15
10
5
Quality Control and Statistical Analyses
Field blank filters were obtained during each sampling
period at each site and consisted of exposure to all field
process except air filtering. Unused filters, field and laboratory blanks were included in the analyses to determine
possible background contamination, as a quality control
measure. The accuracy of the method employed was evalu-
862
0
PM10 -Faj
PM10 -Vie
PM10 -Sal
PM2.5 -Faj
PM2.5 -Guay
Site
FIGURE 1 - Average annual concentrations (standard error) of
PM10 and PM2.5 obtained in several sites in Puerto Rico. Salinas
(Sal) PM10 (2002-2003), Vieques (Vie) PM10 (2001-2002), Fajardo
(Faj) PM10 (2001-2003) and PM2.5 (2000-2001). (*) P value < 0.05.
© by PSP Volume 16 – No 8. 2007
Fresenius Environmental Bulletin
Metallic Elements
Comparison with other places in the world and standard limits
Annual mean concentrations of heavy metals in PM2.5
and PM10 for all sampling sites in Puerto Rico are presented
in Table 1.
Particulate matter concentrations determined throughout these studies were below the range established by
USEPA [17]. While the average PM10 concentrations were
half the standard value (50 µg m-3 - annual arithmetic mean,
[17]) the PM2.5 concentrations were close to the limit (15 µg
m-3 - annual arithmetic mean, [17]). A total of 58 events
(18%) of particulate matter collections were greater than
the standard (15 µg m-3) were registered in Guaynabo and
26 events (8.5%) in Fajardo. With respect to the PM10 concentration obtained at both site (Salinas and Fajardo), only
two events during the year exceeded the USEPA PM10
annual standard of 50 µg m-3. In Vieques and Fajardo
(2001-2002) only one event in both sites exceeded the standard. These events were traced to the dates of Sahara events
(discussed below). Monthly mean levels of PM2.5 in Guaynabo ranged between 7.6 and 14.3 µg m-3 and in Fajardo
between 6.4 and 12.0 µg m-3. Monthly means of PM10 varied from 20.3 to 37.8 µg m-3 in Fajardo, 13.2 to 39.2 µg m-3
in Salinas and 10.8 to 33.5 µg m-3 in Vieques. Annual
means of PM10 in the US ranged from 18 to 47 µg m-3 and
for PM2.5 from 11 to 30 µg m-3 [19]. In other cities in Greece
and Turkey the average PM10 levels reached up to 200 µg
m3 and around 50 µg m3 for PM2.5 [18-20]. In a remote site
in Italy the average concentration of PM10 was 55 µg m3
and 48 µg m3 for PM2.5 [21]. When compared to other cities,
PM2.5 and PM10 concentrations in Puerto Rico were relatively lower.
In the PM10 fraction, Fe was the most enriched element
at all sites, followed by V, Cu and Ni. In the PM2.5 fraction,
Fe also was in the highest concentration followed by V, Zn
and Ni. In previous studies, Fe was also one of the most enriched metals in TSP in Puerto Rico [10]. The means showed
the concentration follows this order in TSP Fe>Pb>Cu>Zn=
V. In another study developed in Ponce city [12] a size distribution of heavy metals showed Fe, Zn and Pb were the
most enriched elements in particles size of 7µm and 2.03.3µm. These results, although not directly comparable to
ours, showed different metal distribution.
Most of the metals in PM10 (As, Co, Fe, Pb and V)
presented slightly higher levels in Vieques than in Fajardo
(2001-2002). In Salinas all metals presented higher concentrations than in Fajardo (2002-2003). The metal concentrations in Salinas were 1.2 to 3.4 fold higher than Fajardo
(2001-2003) and Vieques (2001-2002). These results are in
agreement of what is expected since Salinas is more of an
urban site when compared to Vieques or Fajardo. This must
be related to local inputs of PM from industrial sources in
that region. The average PM2.5 concentration of all heavy
metals analyzed, with the exception of Fe, were significantly higher (3.6 to 28) in Guaynabo than in Fajardo.
Guaynabo is an urban and industrialized area with several
sources of trace metal output.
TABLE 1 - Average arsenic and heavy metal levels (mean ± SE) found in particulate
matter from Fajardo, Guaynabo, Salinas and Vieques in Puerto Rico (2000 – 2003).
As
(ng m-3)
Fajardo - PM10
0.23
(2001-2002)
(± 0.1)
(n = 28)
Vieques - PM10
0.29
(2001-2002)
(± 0.03)
(n = 44)
Fold difference
1.2
Vieques/Fajardo
Fajardo - PM10
0.13
(2002-2003)
(± 0.01)
(n = 29)
Salinas - PM10
0.34*
(2002-2003)
(± 0.03)
(n = 30)
Fold difference
2.6
Salinas/Fajardo
Fajardo - PM2.5
0.09
(2000-2001)
(± 0.03)
(n = 158)
Guaynabo - PM2.5
0.39*
(2000-2001)
(± 0.02)
(n = 158)
Fold difference
4.3
Guaynabo/Fajardo
(-) not analyzed
(*)Significantly different at P<0.05 level
Cd
(ng m-3)
Co
(ng m-3)
Cu
(ng m-3)
Fe
(µg m-3)
Ni
(ng m-3)
Pb
(ng m-3)
V
(ng m-3)
Zn
(ng m-3)
0.023
(± 0.01)
0.14
(± 0.04)
1.87
(± 0.6)
0.27
(± 0.09)
0.78
(± 0.1)
0.72
(± 0.2)
1.87
(± 0.2)
-
0.020
(± 0.004)
0.16
(± 0.04)
1.00
(± 0.1)
0.33
(± 0.11)
0.68
(± 0.2)
0.90
(± 0.1)
2.50
(± 0.3)
-
0.9
1.1
0.5
1.2
0.9
1.2
1.3
-
0.028
(± 0.003)
-
1.5
(± 0.2)
0.36
(± 0.08)
1.70
(± 0.1)
0.86
(± 0.08)
1.60
(± 0.2)
-
0.058*
(±0.005)
-
2.50*
(± 0.1)
0.55
(± 0.09)
2.30
(± 0.2)
1.40*
(± 0.1)
2.50
(± 0.3)
-
2.0
-
1.7
1.5
1.3
1.6
1.6
-
0.015
(± 0.004)
-
0.7
(± 0.1)
0.10*
(± 32)
1.9
(± 0.6)
0.57
(± 0.06)
1.4
(± 0.2)
3.0
(± 1)
0.055*
(± 0.007)
-
5.5*
(± 0.6)
0.09
(± 12)
17.0*
(± 2)
3.0*
(± 0.5)
40.0*
(± 3)
12.0*
(± 3)
3.6
-
7.8
0.9
8.9
5.2
28.6
4.0
863
© by PSP Volume 16 – No 8. 2007
Fresenius Environmental Bulletin
rate 15 m3 day-1 and absorption rate 50% are in range 6081845 ng day-1 and 8-27 ng day-1 (from TSP), respectively
[33]; Zhang et al. [32] found for Pb 2.15 µg day-1 and for
Cd 0.00215 µg day-1 in Bangkok, Thailand. Voutsa and
Samara [30] estimated respiratory update based on 20 m3
day-1 inhalation rate and absorption variable according to
the bioaccessible metal fraction from PM7.2. They found
DRU values for urban and industrial sites for the following
metals: Cd (3.4-5.9 ng day-1), Cu (1290-652 ng day-1), Ni
(56-65 ng day-1), Pb (3.8-4.5 ng day-1) and Zn (574-1513
ng day-1). In spite of different methodologies adopted to
estimate DRU, our results show lower levels of metals absorbed daily, except for Ni and Pb when compared with the
results obtained by Voutsa and Samara [30]. However Pb
was lower than that reported by Zhang et al [32] and Ikeda
et al. [33]. When compared to the daily intake suggested by
WHO, our estimated values were lower. There is no procedure or standard limit established for DRU, which will
provide an accurate exposure estimates for the airborne pollutants. Our data establishes that Ni and V are highly absorbed in the Guaynabo area in Puerto Rico and that they
are significantly higher than other regimes reported throughout other cities of the world.
None of the metals (Cd, Co, Pb, V and Zn) exceeded
the limit suggested by national [17] and international [22,
23] organization. These agencies do not have guideline
values for Fe and Cu.
In general, most airborne trace metals in Puerto Rico
are below the average limit values reported for collected urban particulates [23]. However, Ni and V present in PM2.5
hence the highest concentrations among all metals analyzed
and also higher than other urban locations [24-26]. These
high levels of Ni and V in inhalable particles have been
suggested to be associated with pulmonary toxicity [27-29]
and can be responsible or contribute to the development of
respiratory diseases in Puerto Rico.
Respiration uptake
Human exposure to airborne contaminants can be estimated by air quality monitoring. Daily respiratory uptake
(DRUi) of heavy metals in ambient air can be estimated
from the equation: DRUi = CiAR, where Ci is the concentration of the “i” inhaled metal, R is the daily inhalation rate
(m3 day-1) and A is the absorption rate of this metal after inhalation [30]. There are different values for these three variables used by different authors. We calculated the DRU of
heavy metals by multiplying the concentration of metals in
both PM10 and PM2.5 by the inhalation rate (R) and dividing
by 2 (A). Therefore, R can be set to 20 m3 day-1 as the inhalation rate constant which has been used by the USEPA
[31] (for adults that work 16h in light activities and 8h of
rest) and A is approximately 50% [23, 32, 33]. Intake equal
the metal concentrations times the inhalation rate (20 m3
day-1). The DRU and intake for metals analyzed are shown
in Table 2.
Sources
Dust from Sahara and Sofriere Hill volcano has a strong
impact on the airborne environment in Puerto Rico. However, the volcano impact is not very frequent and depends
on the intensity of the eruption. Frequent dust outbreaks
from the Sahara affect the island especially during summer months although big events have been also detected in
winter. According to NASA’s Earth Probe TOMS (Total
Ozone Mapping Spectrometer) (http://toms.gsfc.nasa.gov/
aerosols/aerosols.html) most of the episodes occurred from
June to September.
The lowest daily respiratory uptake was obtained for
Cd at all sites, followed by Co and As. The highest uptake
was obtained for Fe followed by V, Cu and Ni. Literature
data on the respiratory uptake of Pb and Cd, on inhalation
TABLE 2 - Estimated metal mass concentration absorbed daily (DRU) and
intake in various areas of Puerto Rico and estimated daily intake suggested by WHO.
Element
Salinas
(2002-2003)
PM10
(n = 30)
Inhaled
(ng day-1)
Fe
(µg day-1)
V
Cu
Ni
Pb
As
Cd
Co
Zn
PM2.5
(µg m-3)
PM10
(µg m-3)
Uptake
(ng day-1)
Fajardo
(2001-2003)
PM10
(n = 57)
Vieques
(2001-2002)
PM10
(n = 44)
Inhaled
(ng day-1)
Uptake
(ng day-1)
Inhaled
(ng day-1)
Guaynabo
(2000-2001)
PM2.5
(n = 158)
Uptake
(ng day-1)
Inhaled
(ng day-1)
Fajardo
(2000-2001)
PM2.5
(n = 158)
Uptake
(ng day-1)
Inhaled
(ng day-1)
WHO
Estimated daily
intake (breathing
rate 20 m3 day-1)
(µg day-1)
Uptake
(ng day-1)
Rural
Urban
11.0
5.5
6.3
3.15
6.6
3.3
1.8
0.9
2.0
1.0
-
25.0
50.0
50.0
46.0
28.0
6.8
1.16
-
25.0
25.0
23.0
14.0
3.4
0.58
-
34.7
33.7
24.8
15.8
3.6
0.51
-
17.3
16.8
12.4
7.9
1.8
0.26
-
50.0
20.0
13.6
18.0
5.8
0.4
3.2
-
25.0
10.0
6.8
9.0
2.9
0.2
1.6
-
800.0
110.0
340.0
60.0
7.8
1.2
240.0
400.0
55.0
170.0
30.0
3.9
0.6
14.0
7.0
19.0
5.7
0.9
0.15
30.0
0.2
-
120.0
28.0
14.0
38.0
11.4
1.8
0.3
60.0
0.02-0.2
0.01
-
1.5
0.28
0.1-0.8
4-200
0.4-0.6
0.2
0.7
-
-
-
-
-
-
132.0
116.0
170.0
85.0
-
-
458.0
229.0
486.0
243.0
472.0
236.0
-
-
-
-
-
-
864
© by PSP Volume 16 – No 8. 2007
Fresenius Environmental Bulletin
The information of volcanic eruption obtained from
(http://www.volcano.si.edu/gvp/reports/usgs/archive.cfm)
indicated that only 1 or 2 events a year with duration of 1 or
2 days have reached PR during the last 5 years. Some metals as As, Cd and V come from volcanic activities [23],
while Fe is associated to Sahara dust [34]. Approximately
twenty millions tons of Sahara dust reaches the Caribbean
annually [35]. Sahara and volcanic events influence the
amount of PM and metal distribution and concentrations
throughout the island environment. Figure 2 shows PM
distribution per month in our sampling sites in Puerto Rico
indicating the dates and number of events from Sahara and
Montserrat storms. Notice that the increase in PM concentrations correlates with the increase in number of Sahara
events during the summer months. This effect is noticed
throughout the island and is also evident at the Fajardo
(reference site). Although several Sahara events occurred in
April and May, the PM levels were lower not reaching those
in summer. This could also be influenced by the rainy period, which begins in late April-May.
Average PM10 concentrations at Fajardo and Salinas
(August 2002 to May 2003)
60.0
50.0
40.0
20.0
10.0
2 SE
(8 days)
2 SE
(8 days)
1 VE
5 SE
(9 days)
2 SE
((8 days)
1 VE
0.0
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Month
Fajardo
Salinas
Average PM10 concentrations at Fajardo and Vieques
(June 2001 to April 2002)
50
40
30
2 SE
(4 days)
1 VE
4 SE
(9 days)
20
10
0
The highest levels of PM10 in Salinas and Fajardo
(2002-2003) were obtained during September. The maximum concentration reached 30.2 µg m-3 in Fajardo and
39.0 µg m-3 in Salinas. Five Sahara events (9 days) occurred
during this month and apparently they influenced the
amount of PM10 in air (Figure 2 A). The same behavior in
terms of concentrations was observed in both sites (Salinas
and Fajardo) during this period (September 2002) that could
corroborate the influence of Sahara events. Other months
(November 2002 to February 2003) showed lower levels of
PM10 and no Sahara event occurred. Volcanic events seemed
not to have strong influence in PM concentrations in Puerto
Rico. Although in April to May 2003 two Sahara events
occurred, the PM10 concentration was lower than September
2002. This difference can be related to cloud size and intensity of particulate matter from Sahara and with time over
the island. Moreover the rainy days are frequent during
some months as March to May.
Monthly PM10 maxima were registered in Vieques in
August 2001 (33.5 µg m-3) and Fajardo in June 2001 (34.9
µg m-3). As shown in Figure 2 B, the number of Sahara dust
events seem to have a direct relation associated increases
in PM10. When we compare June 2001 and July 2001 the
relationship seems directly proportional to the number of
Sahara events, but when we compare with April 2002, this
relationship becomes weak, probably due to rainy days. The
higher frequency of Sahara dust episodes registered during summer could lead to an increase in PM levels including at the reference site. The difference among concentrations in summer in both sites (June to August) is minimum
and it could prove the influence of Sahara dust in PM10
levels. Also, the volcanic activity does not have a direct
effect on PM levels (since many of these events do not
reach the island because the eruptions are not of significant magnitude and the prevailing winds at these times are
not strong enough to drive the particles to the Northwest).
2 SE
((8 days)
30.0
Jun
Jul
3 SE
(17 days)
Aug
Sep
Dec
Nov
Month
Oct
Fajardo
Jan
Feb
Mar
Apr
Vieques
Average PM2.5 concentrations at Fajardo and Guaynabo
(November 2000 to September 2001)
16
2 SE
(6 day)
14
2 SE
(4 day)
2 SE
(4 day)
12
4 SE
(7 day)
10
8
6
1 SE
(1 day)
4
4 SE
(10 day)
4 SE
(7 day)
2
0
Nov
Dec
Jan
Feb
Mar
Apr
May
Month
Guaynabo
Jun
Jul
Aug
Sep
Fajardo
FIGURE 2 - Monthly average PM concentrations (µg m-3) in
different sites in Puerto Rico and their relationship with Sahara
Events (SE) and Montserrat Volcano Events (VE) during the
sampling period. 2A) Average PM10 concentrations at Fajardo
and Salinas (August 2002 to May 2003); 2B) Average PM10 concentrations at Fajardo and Vieques (June 2001 to April 2002);
2C) Average PM2.5 concentrations at Fajardo and Guaynabo
(November 2000 to September 2001).
In Guaynabo and Fajardo the maximum PM2.5 levels
were obtained during June 2001 where Fajardo reached (12.0
µg m-3) and in Guaynabo (14.3 µg m-3) in July 2001. Sahara events have shown to have more impact than volcanic
activities in the concentrations of airborne particulate matter on the island (Figure 2C). The maximum PM levels were
obtained during the summer and this fact is evidence that
links Sahara events to increases of PM exposure on the island. Certainly Sahara events are more frequent than volcanic events making Sahara dust a stronger influence on air
quality in Puerto Rico.
865
© by PSP Volume 16 – No 8. 2007
Fresenius Environmental Bulletin
Sahara dust has been reported to be associated with
respiratory illness in Caribbean countries. Since 1970 the
amount of African dust that reaching the Caribbean islands has increased and the respiratory diseases have increased proportionally [34-36]. However, a recent report
did not find any association between Sahara dust and increase in respiratory illness (Prospero, personal communications) in the Island of Barbados. In addition effects on
Caribbean coral reefs have been reported [36,37] which
links increase in dust deposition in shallow waters due to
Sahara dust deposition. In Puerto Rico high incidence of
asthma has been found, but it is not necessarily associated
with Sahara events [38,39], although anecdotal information
from physician and residents on the island indicate that respiratory diseases worsen during Sahara episodes. This phenomenon has to be investigated and needs to be studied
more carefully in order to support or reject such hypothesis.
African dust is a major source of dissolved Fe in the
tropical North Atlantic [36, 40]. The Fe levels present similar behavior or profile as the PM levels. This evidence is
corroborated by good correlation obtained from all sites
between Fe and PM concentrations: Fajardo (PM10: r2 =
0.5, P value 0.06; r2 = 0.7, P value 0.0048; PM2.5: r2 = 0.8,
P<0.0001), Salinas (r2 = 0.5, P value 0.0184), Vieques (r2 =
0.8, P value 0.0028) and Guaynabo (r2 = 0.6, P value 0.009).
A certain influence of Sahara dust can be appreciated by the
increase in Fe concentration with storm events (Figure 3).
Viana et al. [41] reported levels of Fe in PM10 ranging from
5 to 8 µg m-3 during Sahara episodes and 0.4-0.6 µg m-3
during non- African scenarios at the Canary Island. These
values are a little higher than that we find in Puerto Rico
(monthly average 0.7-1.5 µg m-3) during the months that
have Sahara events. However these levels represent the
average obtained for these months and not for the episode
itself. We also need to keep in mind that these differences
could be attributed to the proximity of the sources. This
slight difference is probably due to differences in size distribution among PM material. Fe content > 2% in PM is a
reliable indicator of Sahara dust transport [42], which has
been already demonstrated for Puerto Rico [14]. Our results
show some correlation between Sahara episodes and % Fe
(Figure 3). In the rainy period, March to May, the correlations are not so clear. Most of the Sahara events that reached
the island showed high levels of Fe, higher than 2% in PM
therefore corroborating the influence of this source. While
normal levels of Fe during non-Sahara periods being lower
than < 1%.
The literature shows that Fe is broadly considered as
tracers characterizing soil erosion and dust in the absence
of smelters and or steel industries [43]. Fe, predominantly
in PM10, comes from natural sources as resuspended airborne soil dust. In Puerto Rico, in spite of the relatively
large density of industries, iron remains greatly associated
to Sahara dust except in center of industrial activity such
as near coal plants as the case in Salinas (Figure 3A). Iron
also composes the major fraction of PM2.5 (> 2%) collected
during Sahara events.
%Fe in PM10 at Fajardo and Salinas
(August 2002 to May 2003)
6
1 VE
5 SE
(9 days)
5
4
3
2
1
2 SE
(8 days)
2 SE
(8 days)
1 VE
2 SE
(8 days)
2 SE
(8 days)
0
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Month
Salinas
Fajardo
%Fe in PM10 at Fajardo and Vieques
(June 2001 to April 2002)
3
2.5
2
1.5
2 SE
(4 days)
1 VE
4 SE
(9 days)
1
0.5
3 SE
(17 days)
0
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Apr
Month
Fajardo
Vieques
%Fe in PM2.5 at Fajardo and Guaynabo
(November 2000 to September 2001)
2.5
2 SE
(6 days)
2
1.5
2 SE
(4 days)
1
1 SE
(1 days)
4 SE
(7 days)
4 SE
4 SE
(7 days) (10 days)
0.5
2 SE
(4 days)
0
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Month
Guaynabo
Fajardo
FIGURE 3 - Fe% in PM from different sites in Puerto Rico and
the relationship with Sahara events (SE) and volcano events (VE)
during the sampling period. 3A) Fe% in PM10 at Fajardo and
Salinas (August 2002 to May 2003); 3B) Fe% in PM10 concentrations at Fajardo and Vieques (June 2001 to April 2002); 3C)
Fe% PM2.5 concentrations at Fajardo and Guaynabo (November 2000 to September 2001).
Although volcanic ash is known to contain heavy metals such as Cd, Hg, V plus As its contribution was not evident in particulate collected during our study, however our
work was not directed towards dressing this question.
Most of the metals found in the fine particles (PM2.5)
at the urban/industrial site (Guaynabo) are higher than the
coarse fraction (PM10) at the reference site of Fajardo and
also in Vieques and Salinas. The high levels of trace elements (Ni, V, Pb and As) at the urban site originate from
anthropogenic sources mainly from fuel combustion and
automobile exhaust. This is consistent with what is reported
in the literature, which states that metal concentrations (Cd,
Cu, Pb, Ni, V and Zn) from anthropogenic sources predominate in small particles [23]. It was associated Cd and
Zn with diesel and fuel products combustion. V is linked
866
© by PSP Volume 16 – No 8. 2007
Fresenius Environmental Bulletin
to combustion of fuel-oil that in turn, is one of the main
fuels release from the furnace of refineries [43]. There is a
refinery and two power plants in the Guaynabo site that
have contributed to the output of As, Cd, Cu and Zn. High
Ni and V concentrations as well as the amount of heavy
traffic in the area (related with handling of goods from the
commercial port).
CONCLUSIONS
Characterization of PM2.5 and PM10 was determined
during the period of 2000 to 2003 at different sites in Puerto
Rico. Average levels of PM10 and PM2.5 were below standard limit suggested by EPA (15 µg m-3 and 50 µg m-3,
respectively). Also they were lower as compared to those
of other cities in the US. Metals also presented low levels, except for Ni and V that were one of the highest of
those reported in the literature for PM2.5 trend. Associating
Fe and PM levels with Sahara events was found and reported herein. However, this is relatively good for both
PM10 and PM2.5 when expressed in Fe%. In all cases, the
highest concentration of PM10 and Fe were obtained during summer when Sahara events occurred. Anthropogenic
sources contribute to the presence of Ni, Pb, Zn and V. Only
Ni presented high levels of DRU when compared with literature data. Ni and V have been reported to exert toxic
effects and are known to induce proinflammatory cytokines
in animals and in human cell cultures. The effect and relationship of these elements to respiratory illness at the urban site should be evaluated and studied further. These data
are one of the few available for Puerto Rico and should be
available for comparison of future research of particulate
matter and characteristic of air quality.
ACKNOWLEDGEMENTS
This work was supported by GM61838 NIGMS-RISE
Program, SO6 GM08224 NIH-MBRS SCORE Program and
NIH NCRR RCMI G12RR03051. The publication's contents are solely the responsibility of the authors and do not
necessarily represent the official views of NCRR or NIH".
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CORRESPONDING AUTHOR
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868
Braulio D. Jimenez-Velez
Center for Environmental and Toxicological Research
University of Puerto Rico
Medical Sciences Campus
Biochemistry Department
School of Medicine
PO Box 365067
San Juan 00936-5067
PUERTO RICO
Phone/Fax: +1 787 7538784
e-mail: [email protected]
FEB/ Vol 16/ No 8/ 2007 – pages 861 - 868