Journal of Environmental Protection, 2013, 4, 1502-1509
Published Online December 2013 (http://www.scirp.org/journal/jep)
http://dx.doi.org/10.4236/jep.2013.412172
Open Access JEP
Spatial Variations of Particle-Bound Trace Metals in
Ambient Air of Selected Niger Delta Communities of
Rivers State, Nigeria
Godson R. E. E. Ana1*, Mynepalli K. C. Sridhar1, Jerome Nriagu2
1Department of Environmental Health Sciences, Faculty of Public Health, University of Ibadan, Ibadan, Nigeria; 2Department of
Environmental Health Sciences, School of Public Health, University of Michigan, Ann Arbor, USA.
Received August 14th, 2013; revised September 15th, 2013; accepted October 12th, 2013
Copyright © 2013 Godson R. E. E. Ana et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
In accordance of the Creative Commons Attribution License all Copyrights © 2013 are reserved for SCIRP and the owner of the
intellectual property Godson R. E. E. Ana et al. All Copyright © 2013 are guarded by law and by SCIRP as a guardian.
ABSTRACT
The objective of this study was to determine the spatial variation of particle-bound heavy metals in two communities
with different industrial status in Nigeria’s Niger Delta Area. Fourteen ambient respirable particulate matter (PM10)
samples 7 each from Eleme (highly industrialized) and Ahoada East (less industrialized) communities were collected
according to standard methods using Anderson High volume sampler. Samples were analyzed for trace metals including
Fe, Zn, Ni, Cd, and Pb using Atomic Absorption Spectrophotometer. Data were analyzed using descriptive statistics,
Man Whitney U test and Spearman Rank Correlation all at P < 0.05. PM10 levels were 1.83 times higher at Eleme than
Ahoada East (P < 0.05) and all the values were higher than both the USEPA and WHO limits. At Eleme spatial varia-
tion of PM10 was in the following order: APE5 > APE3 > APE7 > APE1 > APE4 > APE6 > APE2. Fe, Zn and Cd were
higher at Eleme than Ahoada East and the EC/WHO values. Pb was poorly correlated with PM10 (r2 = 0.0819, P > 0.05)
at Eleme. Communities with higher industrial presence in the Niger Delta are more exposed to particulate burden. Rou-
tine monitoring and strict adherence to regulatory limits must be enforced.
Keywords: Industrial Pollution; Particulate Matter; Trace Metals; Spatial Variation; Niger Delta Communities
1. Introduction
Particulate matter (PM) one of the major contributors of
air pollution remains a big threat to human health. The
WHO indicates that 4% - 6% of the world population die
annually due to air pollution related morbidities [1].
PM10 is particularly considered to be a reliable indicator
for possible health effects [2,3].
The airborne PM is usually composed of and or ad-
sorbed by organic and inorganic toxic pollutants and
studies [4] have established links between high levels of
PM and health effects including respiratory and cardiac
diseases [5,6]. Current studies have revealed that the mor-
tality and morbidity rate is directly related to concentra-
tion and number of particles in the aerosol [7-12].
The nature of PM can be organic, inorganic or a mix-
ture with the organic compounds contributing 10% to
40% of the mass of PM. Heavy metals are among the
inorganic elements constituting the PM [13]. Some of
these elements, such as As, Pb, Cd, Hg, Zn, Ni, Cu, Mn
and Cr are of major concern due to their toxic nature
while others, such as Fe, Ca, Ba, and Mn are mainly
linked to the earth’s crust or resuspended soil.
Overall, the effect of PMs depends on its shape, size,
composition, mass and number concentrations and the
receptor cells. The fine particles provoke lung inflamma-
tion and are responsible for cardiovascular diseases [14]
and are potentially toxic to human health because of their
large surface areas, which are coated with different che-
mical constituents and carcinogens [15]. The chemical
characteristics of atmospheric PM are important for
both particle toxicity and its role in climate change
[16-18].
The source of toxic trace metals in ambient PM is de- *Corresponding autho
r
.

Spatial Variations of Particle-Bound Trace Metals in Ambient Air of Selected Niger
Delta Communities of Rivers State, Nigeria
Open Access JEP
1503
pendent on the various anthropogenic processes in a par-
ticular area. These include industrial emissions, power
plants, urban traffic and combustion by-products. Com-
bustion from automobiles constitutes one of the major
sources of particulate emissions, especially the respirable
fraction and is directly related to human health [19]. Ac-
cording to Kisku et al. [20] and Sharma et al. [21] vehi-
cle related emissions is the main source of particulate
pollution in Lucknow. Except for storage batteries, paint
and gasoline additives were the two major high-volume
products containing Pb; about the same quantity of Pb, 5
to 6 million metric tons, was used to manufacture each
[22]. Pb is associated with the smallest particles, the clay
grain size fraction in urban soils [23], therefore the con-
centration of Pb in dust originating from urban soils [24]
is higher than that from simple measurements of the Pb
content of the soil [25].
Several reports show that Pb induces severe neuro-
logical and hematological effects on the exposed popula-
tion especially children [26]. Cd and Ni are known for
inducing carcinogenic effects in humans through inhala-
tion. Occupational level of Cd exposure is a risk factor
for chronic lung diseases [27]. Cr is known for its toxic
and carcinogenic effect on the bronchial tree [28,29]. Mn
exposure leads to increased neurotoxic impairments [30].
The increased level of Cu can lead to respiratory irritancy
[23,31].
In Nigeria, Ana et al. [32] showed varying concentra-
tions of particulate matter in selected Niger Delta com-
munities. However, other researchers [33-35] reported
suspended particulates and their elemental concentrations
within and around industrial complexes, road side dust,
and its effect on soil, vegetation and crops in other parts
of the country. Efe [36] reported on spatial distribution of
particulate air pollution in Nigerian cities and their im-
plication for human health. The study showed that over
70% of Nigerian urban environments have mean annual
ambient PM10 value of over 120 μg/m3. Okuo and Ndi-
okwere [37] studied elemental concentration of Total
Suspended Particles with levels as high as 1332.75 μg/m3
in Warri and elemental concentrations range (μg/m3) for
metals including As (3.01 - 5.21), Cd (0.02 - 0.23), Pb
(1.01 - 1.04) and Fe (1.13 - 1.38). Also Akeredolu et al.,
[38] and Asubiojo et al. [39] reported levels of particu-
late matter 40,000 μg/m3 in industrial sites and 1033
μg/m3 in ambient air. But in all these studies there were
no indications on the varying pollution levels arising
from different sources.
Our study therefore elucidated the spatial variations of
the particle-bound trace metals between two communi-
ties of different urban and industrial status in Nigeria’s
Niger Delta Area.
2. Material and Methods
2.1. Description of the Study Area
The study was carried out in two local government areas
(LGAs): Eleme a highly industrialized LGA located
about 20 km away from Port Harcourt city, the Rivers
state capital and Ahoada East a less industrialized LGA
located about 80 km from the state capital. The major
industries at Eleme include Shell Petroleum Develop-
ment Corporation (SPDC) oil wells at Ebubu, Petro-
chemicals at Akpajo/Agbonjia, Refinery at Alesa/Okirika
and a fertilizer complex at Onne. Both LGAs share a
similar tropical climate. Their vegetation is a mixture of
rainforest and mangrove/swamp forest. In addition, the
aquatic resources are equally a mixture of fresh and
brackish water.
2.2. Sampling Locations and Conditions
Particle-bound heavy metal samples from outdoor ambi-
ent air were collected systematically from 14 locations: 7
from Eleme and 7 from Ahoada East communities re-
spectively (see Figure 1). Samples were collected during
late dry season conditions (February-March).The average
meteorological conditions recorded showed temperature
range of 28˚C - 31˚C. Average windy conditions with
wind speed hardly exceeding 3.5 m·s−1 at the sample
locations with no cloud cover. A low relative humidity of
less than 12 - 33 mm was recorded throughout the period
of sampling.
2.3. Determination of Respirable Particulate
Matter (PM10)
The respirable particulate matter (PM10) samples were
obtained using a high volume sampler Anderson model
reference method No RFPS-1287-063 with 10 μm cut off
inlet at a flow rate of 1 - 1.2 m3 for 4 hr. Preweighed
glass fibre filter papers with dimension 20.3 × 25.4 cm (8
× 10 in) (eCat No: 1882 866) EPM 2000 were used and
reweighed after sampling in order to determine the mass
of the particles collected. The concentration of the par-
ticulate matter (μg/m3) was computed on the basis of the
net mass collected divided by the volume of air sampled.
2.4. Trace Metals Analysis
The concentration of heavy metals in air was determined
with slight modifications using methods described by
Dorn et al. [40]. The filter papers shredded into tiny frac-
tions were carefully digested with 10 ml of concentrated
HNO3 inside a Teflon beaker and heated at about 120˚C
until solution became clear. The content was filtered
through a Whatman filter (No. 42) and final volume was

Spatial Variations of Particle-Bound Trace Metals in Ambient Air of Selected Niger
Delta Communities of Rivers State, Nigeria
Open Access JEP
1504
Figure 1. Air sampling locations in study communities.
made up to 50 ml with Milli Q water. The concentrations
of heavy metals (mg/m3) Fe, Zn, Ni, Cd, and Pb were
determined using Perkin Elmer AAS model 929 with
double beam background corrector. Air-acetylene flame
and graphite furnace with appropriate cathode lamps were
used.
2.5. Statistical Analysis
Data obtained from the field and laboratory were proc-
essed statistically using SPSS version 15. Data were ana-
lyzed using descriptive statistics, Mann-Whitney test and
Spearman correlation for quantitative variables all at 5%
level of significance.
3. Results
3.1. Concentration of Respirable Particulate
Matter (PM10)
The PM10 and trace metals: Fe, Zn, Pb, Cd and Ni con-
centration were determined in the ambient air at Eleme.
Table 1 indicates that the highest PM10 levels were re-
corded at Alesa (232.5 ± 23.2 µg/m3) and Ebubu (260.6 ±
47.7 µg/m3) compared to all other sampling locations and
the mean PM10 levels recorded at Eleme was observed to
be higher than Nigeria’s minimum (100 µg/m3) but lower
than maximum (250 µg/m3) guideline limits (Figure 2)
respectively. The spatial variation in the concentration of
PM10 in the ambient air at Eleme is in the following or-
der: APE5 > APE3 > APE7 > APE1 > APE4 > APE6 >
Figure 2. PM10 levels at study locations in comparison with
guideline limits.
APE2.
At Ahoada East Table 2 shows that the highest PM10
concentrations were recorded at Ahoada (161.4 ± 10.2
g/m3) and Ula Ehuda (141.9 ± 7.92 g/m3) as compared
to other sampling locations. The mean PM10 levels were
both lower than Nigeria’s Minimum guideline limit of
100 g/m3 and the maximum guideline limit of (250
µg/m3) (Figure 2).The spatial variation in the PM10 con-
centration in descending order is as follows APA2 >
APA3 > APA4 > APA1 > APA5 > APA7 > APA6 with
the most prominent urban communities of Ahoada (APA2)
and Ula Ehuda (APA3) recording the highest concentra-
tions.

Spatial Variations of Particle-Bound Trace Metals in Ambient Air of Selected Niger
Delta Communities of Rivers State, Nigeria
Open Access JEP
1505
Table 1. PM10 and trace metal concentrations in ambient air at Eleme.
Sample ID/Location/Parameter APE1 Akpajo APE2 AletoAPE3 AlesaAPE4 OgaleAPE5 Ebubu APE6 Ekporo APE7 Onne
PM10 (g/m3) 75.0 ± 6.51 37.2 ± 0.35232.5 ± 23.261.0 ± 2.26260.6 ± 47.7 43.2 ± 7.49 154.4 ± 16.5
Fe (g/m3) 0.09 ± 0.02 0.09 ± 0.040.10 ± 0.07 0.10 ± 0.080.10 ± 0.09 0.10 ± 0.06 0.10 ± 0.08
Zn (g/m3) 0.04 ± 0.01 0.03 ± 0.020.05 ± 0.04 0.02 ± 0.010.05 ± 0.03 0.05 ± 0.02 0.10 ± 0.05
Pb (g/m3) 0.07 ± 0.02 0.10 ± 0.020.07 ± 0.03 0.02 ± 0.010.10 ± 0.05 0.05  0.02 0.03 ± 0.03
Cd (g/m3) 0.02 ± 0.02 0.01 ± 0.010.02 ± 0.02 0.01 ± 0.030.002 ± 0.003 0.003 ± 0.002 0.004 ± 0.001
Ni (g/m3) 0.03 ± 0.02 0.03 ± 0.010.05 ± 0.03 0.02 ± 0.020.03 ± 0.04 0.04 ± 0.02 0.03 ± 0.02
Table 2. PM10 and trace metal concentrations in ambient air at Ahoada East.
Sample ID/Location/Parameter APA1 Ulapata APA2 AhoadaAPA3 Ula EhudaAPA4 IhuboguAPA5 Ihuoho APA6 Ikata APA7 Odiabidi
PM10 (g/m3) 25.9 ± 3.89 161.4 ± 10.2141.9 ± 7.92 104.7 ± 8.41 20.4 ± 1.06 8.84 ± 0.50 10.4 ± 0.06
Fe (g/m3) 0.01 ± 0.01 0.03 ± 0.02 0.04 ± 0.02 0.04 ± 0.02 0.03 ± 0.01 0.03 ± 0.02 0.05 ± 0.04
Zn (g/m3) 0.08 ± 0.04 0.03 ± 0.01 0.05 ± 0.03 0.05 ± 0.03 0.04 ± 0.01 0.05 ± 0.03 0.42 ± 0.14
Pb (g/m3) 0.05 ± 0.02 0.04 ± 0.03 0.13 ± 0.08 0.03 ± 0.02 0.11 ± 0.10 0.11 ± 0.09 0.13 ± 0.07
Cd (g/m3) 0.01 ± 0.03 0.004 ± 0.0020.01 ± 0.01 0.01 ± 0.03 0.002 ± 0.001 0.004 ± 0.002 0.01 ± 0.01
Ni (g/m3) 0.01 ± 0.01 0.02 ± 0.02 0.03 ± 0.02 0.03 ± 0.02 0.05 ± 0.03 0.03 ± 0.03 0.04 ± 0.02
3.2. Concentration of Trace Metals
Table 1 indicates that the highest Pb level was recorded
at Ebubu (0.10  0.05 g/m3) while the highest Cd levels
was recorded at Akpajo (0.02  0.02 g/m3) and Alesa
(0.02  0.02 g/m3) respectively. At Ahoada East the
highest Pb levels were recorded at locations in Ula Ehuda
(0.13 ± 0.08 g/m3) and Odiabidi (0.13 ± 0.07 g/m3)
(Table 2). Of the five heavy metals assessed three viz Fe,
Zn and Cd recorded higher concentrations at Eleme.
Only Pb recorded a higher concentration at Ahoada East
(Figure 3).
3.3. Relationship between PM10 and
Trace Metals
The relationship between the PM10 and trace metals was
assessed based on the level of correlations. Given the
place of Pb among the most toxic heavy metals in the
EPA priority list only the result of the correlation test for
PM10 and Pb is reported here (Figures 4(a) and (b)). In
all the cases no significant correlations were observed.
4. Discussion
The concentrations of PM10 were assessed in relation to
trace metals in two communities of Nigeria’s premium
oil producing area with different levels of industrial ac-
tivities and urbanization. The results of the respirable
fraction of particulate matter and the trace metals ad-
Fe Zn Pb
Cd
Ni
0.00
0.05
0.10
0.15
0.20
Eleme
Ahoada East
METALS
Mean  SD
Figure 3. Comparison of mean values of heavy metals be-
tween Eleme and Ahoada East.
sorbed on the surface of the particles are given in Tables
2(a) and (b) with Figures 4(a) and (b) showing the cor-
relation between these two parameters.
At Eleme the spatial distribution of PM10 in the vari-
ous sampling locations showed the following order:
APE5 > APE3 > APE7 > APE1 > APE4 > APE6 >
APE2.The first four sampling points represent locations
at Ebubu where Shell Petroleum has its oil locations
(APE5), refinery complex at Alesa (APE3), chemical fer-
tilizer complex at Onne (APE7) and the petrochemical
complex at Akpajo (APE1) recorded the highest concen-
trations.
The presence of these industrial facilities associated
with increased human activities viz automobile emissions,
burning of biomass, must have contributed to the higher
PM10 concentrations in these locations than the others.

Spatial Variations of Particle-Bound Trace Metals in Ambient Air of Selected Niger
Delta Communities of Rivers State, Nigeria
Open Access JEP
1506
y = 1E-04x + 0.0509
R
2
= 0. 0819
0
0. 02
0. 04
0. 06
0. 08
0. 1
0. 12
050100 150 200250 300
PM10 Level s(ug/m 3)
Pb Conc(mg/ m3)
(a)
y = -0.0003x + 0. 1028
R
2
= 0. 14 62
0
0. 02
0. 04
0. 06
0. 08
0. 1
0. 12
0. 14
050100 150 200
PM10 Leve l s(ug/m3)
Pb Conc(mg/m3)
(b)
Figure 4. (a) Correlation between PM10 and Pb in ambient
Air at Eleme; (b) Correlation between PM10 and Pb in am-
bient air at Ahoada East.
This observation is in concert with studies by Efe [37]
where PM10 concentrations were higher in more urban-
ized settings with higher industrial and traffic conditions.
In the same vein at Ahoada East, the order of PM10 was:
APA2 > APA3 > APA4 > APA1 > APA5 > APA7 >
APA6 with the most prominent urban communities of
Ahoada (APA2) and Ula Ehuda (APA3) recording the
highest concentrations.
The mean PM10 concentration observed at Eleme was
expectedly higher (1.83 times) than that recorded at
Ahoada East. This could be explained by the fact that
there are more anthropogenic activities especially auto-
mobile and industrial emissions at Eleme which is con-
sidered to be more urbanized than Ahoada East. The
presence of the refinery, petrochemical complex, chemi-
cal fertilizer company and other industries have certainly
contributed to the burden of particulate emissions in the
ambient air environment of these localities.
The mean levels of PM10 at Eleme though higher than
the values from Ahoada East were comparable to that
reported by Efe [37], close to that reported by Singh et al.
[41], higher than that reported in most European coun-
tries [42,43] and some American countries [44]. Overall,
these levels were lower than Nigerian Max permissible
limits [45] but higher than USEPA limits.
The spatial variation in the concentration of Pb in the
ambient air at Eleme is as follows: APE5 > APE2 >
APAE3 = APE1 > APE6 > APE7 > APE4.Excluding
APE2, the first four locations have very high industrial
presence with its attendant human activities and this must
have contributed to the high levels of Pb in the ambient
air. Also the spatial variation at Ahoada East shows the
following trend: APA7 = APA3 > APA5 = APA6 >
APA1 > APA2 > APA4.
In contrast to the observations at Eleme, Ahoada
(APA2) the most urbanized community and the adminis-
trative headquarters of the local government area re-
corded the lowest Pb level. The spatial variation for other
trace metals was also noted. Pb mainly from anthropo-
genic sources was found to be higher at Ahoada East
than Eleme and about a 1000 times higher than values
reported by Lopez et al. [43], despite the higher indus-
trial outlook of Eleme. These values were 60 folds (for
Eleme) and 90 folds (for Ahoada East) higher than WHO
limits. Fe had higher concentrations at Eleme than
Ahoada East and these levels were higher than levels
recorded by Sharma et al. [21], Singh et al. [41]. The Fe
could have been from both natural and anthropogenic
origin [46].
The concentration of Zn was higher at Eleme than
Ahoada East and these levels are higher than the values
reported by Singh et al. [41] as well as the WHO guide-
line [2]. Nowadays, Zn has been proposed as a reliable
tracer of unleaded fuel and diesel oil-powered motor ve-
hicle emissions. Cd mostly from occupational origin was
highest with values almost 10 times at Eleme as com-
pared to Ahoada East. Ni emitted from both stationary
and mobile sources had same mean concentrations for
Eleme and Ahoada East suggesting similar inputs from
probably automobile emissions.
Several studies have shown some level of correlation
and linear relationship between the PM10 concentrations
and trace metals. For instance Singh et al. [41] showed a
correlation of PM10 with Zn (r = 0.39, p < 0.05) and Ni (r
= 0.36, p < 0.05). Also Barman et al. [45] showed a cor-
relation of Ni (r = 0.71, p < 0.01), Cd (r = 0.65 < 0.01)
with PM10 and similarly Sharma et al. [21] showed cor-
relation of Fe (r = 0.71, p > 0.05) with PM10.This sug-
gests that trace metals adsorbed on particulate matter are
linearly dependent on the PM10 levels. In the present
study nearly all the metals were poorly correlated with
PM10 even though only the correlation between Pb and
PM10 is being reported. The result was however at vari-
ance with those hitherto reported. This suggests that most
of the sources of PM10 were not rich in the trace metals
determined.
It is considered that elevated concentrations of PM10
and particle-bound trace metals have direct relation to
adverse human health as well as on the environment

Spatial Variations of Particle-Bound Trace Metals in Ambient Air of Selected Niger
Delta Communities of Rivers State, Nigeria
Open Access JEP
1507
[47-49] Other studies have also implicated high levels of
PM10 with various forms of respiratory and cardiovascu-
lar disorders as well as increased hospital visitations [7].
In this study the levels of PM10 and the associated trace
metals were higher in the ambient air at Eleme as com-
pared with Ahoada East, implying that the populations in
the former than the later would be more prone to adverse
health outcomes.
5. Conclusions
The study revealed that respirable particulate matter was
nearly two folds higher in the ambient air at Eleme com-
pared to Ahoada East and the levels even though lower
than FEPA guidelines were higher than USEPA and
WHO limits.
Three out of the five trace metals namely Fe, Zn and
Cd recorded higher concentrations at Eleme compared to
Ahoada East with Pb only recording the highest concen-
tration at Ahoada East.
The concentrations of all the trace metals were higher
than those from previously reported studies as well as the
EC and WHO guideline limits.
Although linear relationship was established between
the PM10 levels and Pb the correlation was poor and not
statistically significant for both Eleme and Ahoada East.
Industrialized communities with elevated levels of
PM10 and associated toxic elements are more likely to be
vulnerable to related health hazards posed by these sub-
stances in the ambient air. Therefore as a matter of policy
routine air monitoring and strict adherence to regulatory
limits by industries operating in the Niger Delta area
should be enforced.
6. Acknowledgements
We are thankful to the management and staff of Research
and Development of the Nigeria National Corporation
NNPC for providing facility and logistic support towards
the completion of this study
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