Research Journal of Environmental and Earth Sciences 4(2): 171-176, 2012
ISSN: 2041-0492
©Maxwell Scientific Organizational, 2012
Submitted: October 23, 2011
Accepted: November 15 , 2011
Published: February 01, 2012
Heavy Metal Concentrations in Top Agricultural Soils around Ceramic and
Pharmaceutical Industrial Sites in Niger State, Nigeria
1
Y.A. Iyaka and 2S.E. Kakulu
1
Department of Chemistry, Federal University of Technology, Minna, Niger State, Nigeria
2
Department of Chemistry, University of Abuja, Abuja, F.C.T., Nigeria
Abstract: Lead, copper, nickel and zinc contents in agricultural soils within the vicinity of ceramic and
pharmaceutical industrial sites in Niger State, Nigeria were determined using Flame Atomic Absorption
Spectrophotometry technique. Mean contents for all sample locations of the two industrial sites were 18±7.5,
15±5.7, 1.9±0.96 and 28±22 mg/kg for lead, copper, nickel and zinc, respectively. The obtained values were
of higher contents than the background levels measured in control soil samples, thereby showing that studied
heavy metals are mainly accounted for by anthropogenic activities, although nickel was less apparent. The
findings of this study have also revealed the need for more constant monitoring of heavy metal concentrations
in soils from the vicinity of industrial sites in developing nations in order to assess their possible potential
hazard to life and environment.
Key words: Contamination, developing nation, emission, land, trace toxic, elements
sites involve two or more heavy metals. The aim of this
research, therefore, is to determine the extent of lead (Pb),
copper (Cu), nickel (Ni) and zinc (Zn) contamination in
cultivated farmlands in the vicinity of ceramic and
pharmaceutical industrial sites in two major cities of
Suleja and Minna respectively in Niger State, Nigeria.
The study also aimed at providing a data base of Pb, Cu,
Ni and Zn in this area in order to assess the influence of
industrial activities on agricultural soils particularly
within the cultivated farmlands, since such studies are
scarce for soils in North- central zone of Nigeria.
INTRODUCTION
Heavy metals occur naturally as chemical elements
in the earth’s crust and surface soils in varying
concentrations (Ward, 1995; Alloway and Ayres, 1997),
but of concern is their emissions through industrial, man’s
agricultural and urban activities into the environment and
consequently into soils that serve as ultimate sink.
Furthermore, the persistent accumulation of heavy metals
in soils is of great concern because they constitute health
threat and toxicity problems to human life and
environment (Purves, 1985; Wild, 1994). Heavy metal
contamination of soils through anthropogenic sources
from the vicinity of industrial sites have also been
reported by various researchers (Onianwa and Fakayode,
2000; Martley et al., 2004; Kachenko and Singh, 2006;
Ngoc et al., 2009). However, in agricultural soils the
anthropogenic input of trace metals can be enhanced by
chemical applications such as fertilizers, herbicides,
pesticides as well as applications of animal manure and
sewage (Alloway and Ayres, 1997; Merrington et al.,
2003; Montagne et al., 2007; Iyaka and Kakulu, 2009).
The pace and scale of environmental contamination
by industrial activities have steadily increased in the last
two centuries due to the pronounced industrial revolution
(Stigliani et al., 1991). Hence, 40% of the approximately
1000 contaminated super fund sites identified on the
USEPA’s National Priority List involved heavy metal
contamination associated with industrial activities
(Fostner, 1995), and 70% of all the metal-contaminated
MATERIALS AND METHODS
Soil sampling: Soil samples of topsoil were collected
from 32 locations within the vicinity of ceramic and
pharmaceutical industrial sites in two major cities of
Suleja and Minna, respectively in Niger State. Control
soil samples were collected from locations within the two
cities that were far from any major pollution sources. The
sampling approach was random and systematic; at each
sampling location or point a stainless steel auger was used
to collect five sub-samples from the top layer at a depth of
0-20 cm. The collected sub-samples were then pooled
together to form a composite of each individual sample.
Analytical methods: The soil samples were air-dried for
one week, ground, passed through 2.0 mm sieve (for soil
pH and particle size analysis), and some portion of the
individual sieved sample was further pulverized to a fine
Corresponding Author: Y.A. Iyaka, Department of Chemistry, Federal University of Technology, Minna, Niger State, Nigeria,
Tel.: +2348035799257
171
Res. J. Environ. Earth Sci., 4(2): 171-176, 2012
Table 1: Soil properties of the vicinity of a ceramic industrial site
%
Sample
Distance from pH
--------------------------------------OC Sand
Silt Clay
Location factory (m)
(H2O)
East
0.0
6.7
0.92
74.1
17.7
8.2
East
50.0
5.6
0.94
73.1
13.7
13.2
East
100.0
5.6
1.50
76.1
14.7
9.2
South East 0.0
7.3
2.00
76.1
15.7
8.2
South East 50.0
6.5
1.50
69.1
17.7
13.2
South East 100.0
6.2
0.90
71.1
19.7
9.2
South
0.0
4.8
0.86
72.1
16.7
11.2
South
50.0
4.7
2.00
74.1
16.5
9.4
West
0.0
7.0
1.60
78.1
13.9
8.0
West
30.0
7.0
2.10
75.1
16.9
8.0
North West 0.0
6.3
0.98
72.1
20.3
7.6
North West 50.0
5.7
1.50
70.1
20.5
9.2
North
0.0
6.0
1.40
73.1
17.5
9.4
North
50.0
5.5
1.70
72.1
15.7
12.2
North
100.0
5.3
1.50
72.1
15.7
12.2
North East 0.0
6.6
0.68
72.1
16.7
11.2
North East 50.0
5.2
0.68
74.1
16.5
9.4
North East 100.0
5.4
1.80
69.1
22.7
8.2
average values being in excess of 90 % for Pb, Cu, Ni and
Zn analyzed.
RESULTS AND DISCUSSION
Soil physico-chemical properties: The interpretation
data for rating the obtained values of the soil physicochemical properties in this study were adapted from Baize
(1993) and Kparmwang et al. (2000). Greater than 50% of
the soil samples studied from the vicinity of the two
industrial sites were weakly acid, with approximately
more than 30% being neutral, and many few were acid
(Table 1 and 2). The pH values ranged from 4.7-7.3 and
from 4.6-7.6 with mean values of 6.0±0.8 and 6.1±0.8 for
ceramic and pharmaceutical industrial sites respectively
(Table 3). The general mean pH value of 6.0±0.8 obtained
from this study is lower than the previously reported value
by Iyaka and Kakulu (2009) in their study of cultivated
farmlands in the vicinity of abandoned industrial sites in
Niger State, but higher than the average pH value of 5.2
reported for some Nigerian soils by Onofiok and Ojobo
(1993).
The soil organic carbon contents ranged from 0.682.1% for the ceramic industrial site and from 0.42-2.7%
for the pharmaceutical industrial site. Up to 55.5% and
about 50% of the analyzed soil samples from the vicinities
of the ceramic and pharmaceutical industrial sites
respectively are within the medium range of 1.0-2.0%
organic contents. Only 30.9% of ceramic and 35.7% of
the pharmaceutical studied soils have low organic carbon
concentrations. The clay contents for all the soil samples
from the vicinities of the two studied industrial sites
ranged between 7.1 and 13.2% with mean values of
9.8±1.9 and 9.6±1.4%, respectively for ceramic and
pharmaceutical industrial sites.
Table 2: Soil properties of the vicinity of a pharmaceutical industrial site
%
Sample
Distance from pH
-------------------------------------Sand
Silt
Clay
location
factory (m)
(H2O) % OC
East
0.0
6.1
2.5
80.7
10.9
8.4
East
50.0
4.6
1.4
82.7
8.7
8.6
East
100.0
6.3
0.54
84.7
6.7
8.6
South East 0.0
6.4
1.3
81.7
9.9
8.4
South East 50.0
5.9
0.68
80.9
10.5
8.6
South East 100.0
5.1
0.42
80.7
8.7
10.6
South
0.0
7.0
1.7
80.7
9.7
9.6
South
50.0
5.5
0.92
87.7
3.7
8.6
South
100.0
6.5
1.5
83.7
6.7
9.6
North
0.0
6.9
1.6
84.7
6.7
8.6
North
50.0
6.6
2.7
82.7
8.9
8.4
North
100.0
7.6
1.2
81.7
5.7
12.6
North East 0.0
6.1
1.5
80.7
10.9
8.4
North East 50.0
5.1
0.78
82.7
5.7
11.6
powder (passed through 0.5 mm sieve) for the total metal
content and organic carbon determination. Soil pH was
measured in 1:1 (soil to water ratio) according to Tan
(1996), organic carbon was determined by Walkley-Black
titration method and particle size was determined using
hydrometer method of soil mechanical analysis. Soil
samples were digested with HNO3-H2O2-HCl using
USEPA SW-846, method 3050(1986). The USEPA SW846, method 3050 developed for total sorbed heavy
metals in soils, gives a reliable measure of the amount of
the metals added to soils as nonsilicates (Risser and
Baker, 1990) that is potentially available for natural
leaching and biological processes. The concentrations of
Pb, Cu, Ni and Zn in the digestion solution were
determined with a Unicam 969 Atomic Absorption
Spectrophotometer - solar in the flame mode.
At least one reagent blank and one duplicate sample
were run for every batch of 5 samples for background
correction and to verify the precision of the method.
Accuracy was however, assessed by analyzing three (3)
replicates of certified reference materials, soil sample S01, obtained from Canada Centre for Mineral and Energy
Technology (CANMET). Recoveries were satisfactory;
HEAVY METAL CONTENTS IN SOILS
Lead: Table 4 and 5 indicated that Pb levels in the
vicinity of the ceramic industrial site ranged from 7.7
mg/kg in North East ward direction (50.0 m) to 22 mg/kg
in East ward direction (0.0 m), and in the pharmaceutical
industrial site obtained values varied from 15 mg/kg in
East ward direction (50.0 m) to 38 mg/kg in North East
ward direction (50.0 m). The varied concentrations
obtained in this study are within the normal range of 2-60
mg/kg reported by Scheffer and Schachtschabel (1992)
for Pb in soils that are not exposed to direct air pollution,
but the obtained Pb values for the soils from the vicinity
of the pharmaceutical industrial site are generally higher
than the background value of 10 mg/kg documented by
Alloway (1990).
Honk and Lock (2000) recognized ceramic industry
as an important source of Pb and Cd pollution, thus the
172
Res. J. Environ. Earth Sci., 4(2): 171-176, 2012
Table 3: Ranges and Mean of the Soil properties from the two industrial sites studied
%
-----------------------------------------------------------------------------------------------Industrial site
pH (H2O)
OC
Sand
Silt
Clay
Ceramic
Range
4.7-7.3
0.68-2.0
69.1-79.1
13.7-20.5
7.6-13.2
(n = 18)
Mean
6.0
1.4
73.0
17.2
9.8
0.8
0.5
2.4
2.4
1.9
SDa
Pharmaceutical
Range
4.6-7.6
0.42-2.7
80.7-87.7
5.7-10.9
8.4-12.6
(n = 14)
Mean
6.1
1.3
82.6
8.1
9.6
SD
0.8
0.7
2.1
2.2
1.4
All soils
Range
4.6-7.6
0.42-2.7
69.1-87.7
5.7-20.5
7.6-11.2
(n = 32)
Mean
6.0
1.4
77.2
13.2
9.6
SD
0.8
0.6
5.3
5.1
1.7
a
: Standard deviation
Table 4: Heavy metal contents in soils from the vicinity of a ceramic
industrial site
mg/kg
Sample
Distance from
----------------------------------------------location
factory (m)
Pb
Cu
Ni
Zn
East
0.0
22
15
2.5
38
East
50.0
14
13
1.7
29
East
100.0
11
12
1.2
1.5
South East
0.0
13
14
2.3
61
South East
50.0
12
14
2.1
20
South East
100.0
8.2
12
0.5
19.0
South
0.0
13
16
2.3
22
South
50.0
13
12
2.3
27
West
0.0
9.6
10
0.70
26
West
30.0
19
16
2.3
19
North West
0.0
13
20
2.8
14
North West
50.0
20
20
1.7
1.7
North
0.0
11
16
2.5
15
North
50.0
9.9
16
2.1
9.9
North
100.0
8.0
13
1.1
7.2
North East
0.0
8.8
16
3.8
27
North East
50.0
7.7
14
2.2
7.6
North East
100.0
13
17
3.2
11
Table 6: Summary of the heavy metal contents (mg/kg) in soils from
the vicinity of industrial sites studied
Site
Heavy metal
Range
Mean
SD
Ceramic
Pb
7.7-22
13
4.1
Cu
10-20
15
2.7
Ni
0.51-3.8
2.1
0.38
Zn
7.2-61
22
14
Pharmaceutical
Pb
15-30
24
59
Cu
4.4-34
16
82
Ni
nd-3.7
1.5
1.1
Zn
5.4-106
36
28
All soils
Pb
7.7-30
18
7.5
Cu
4.4-34
15
5.7
Ni
nd-3.8
1.9
0.96
Zn
5.4-106
28
22
Control
Pb
nd
Cu
4.2-7.0
5.4
1.2
Ni
nd
Zn
8.4-16
12
3.2
(50.0 m) directions when compared to their 0.0 m location
values may probably be ascribed to passage of roadway
along those sampling locations, and vehicular emissions
have been identified with deposition of Pb in roadside soil
by various authors (Tiller, 1989; Othman et al., 1997; AlChalabi and Hawker, 2000). Furthermore, the relatively
low average content of Pb obtained from soils of ceramic
industrial site in this study, much as it presents
insignificant exposure risks; do not rule out the possibility
of increase in Pb levels with time. Other previous findings
by Madrid et al. (2002) had reported that the extent of
heavy metal pollution varied with age, particularly for Cu
and Pb (Chen et al., 2005).
Table 5: Heavy metal contents in soils from the vicinity of a
pharmaceutical industrial site
mg/kg
Sample
Distance from
--------------------------------------------location
factory (m)
Pb
Cu
Ni
Zn
East
0.0
23
15
3.70
56
East
50.0
15
34
1.30
39
12
East
100.0
24
4.4
ndb
South East
0.0
20
14
1.80
28
South East
50.0
20
7.0
0.40
9.2
South East
100.0
20
4.6
0.13
5.4
South
0.0
29
23
1.40
74
South
50.0
18
15
0.77
17
South
100.0
30
19
1.90
106
North
0.0
27
13
3.40
47
North
50.0
23
26
1.40
43
North
100.0
21
11
1.30
23
North East
0.0
26
14
0.77
31
North East
50.0
38
19
nd
13
b
: Not detected
Copper: Levels of Cu in soil samples of the vicinity of
the ceramic and pharmaceutical industrial sites are shown
in Table 4 and 5 respectively. The Cu contents in studied
soils from the vicinity of the ceramic Industrial site are
within the normal range given in literature for soil in
Europe (Besnard et al., 2001) and the obtained average
value for soils from ceramic industrial site in this study is
higher than 2.44 and 4.21 mg/kg, respectively reported for
form and fertilizer blending companies by Harami et al.
(2004) in their study of heavy metal levels in industrial
estate of Bauchi, Nigeria.
obtained values for Pb from the vicinity of the ceramic
industrial site in this study show that Pb levels generally
decreased with distance from the factory (Table4), thereby
suggesting dispersion from a point source. The higher Pb
contents obtained from West (30.0 m) and Northwest
173
Res. J. Environ. Earth Sci., 4(2): 171-176, 2012
Table 7: Correlation coefficients of elemental content with soil properties of the studied sites
Industrial site
pH
OC
Sand
Ceramic
Pb
0.219
0.334
- 0.010
Cu
0.023
- 0.004
- 0.458
Ni
0.161
- 0.024
- 0.054
Zn
0.551*
0.227
0.467
Pharmaceutical
Pb
0.427
0.327
0.025
Cu
- 0.057
0.591**
0.098
Ni
0.522
0.712**
0.199
Zn
0.511
0.890**
- 0.009
All soils
Pb
0.252
0.109
0.663**
Cu
- 0.036
0.297
- 0.094
Ni
0.180
0.263
- 0.283
Zn
0.543**
0.554**
0.355**
*: Correlation is significant at the 0.05 level; **: Correlation is significant at the 0.01 level
Silt
0.364
0.605**
0.408
- 0.187
- 0.051
- 0.009
0.063
0.215
- 0.577**
0.167
0.417**
- 0.223
Clay
- 0.350
- 0.153
- 0.245
- 0.201
0.187
- 0.112
- 0.272
- 0.244
- 0.164
- 0.108
- 0.165
- 0.270
of metal pollutants such as Zn in soils. Furthermore, the
mean Zn contents of 36±28 and 22±14 mg/kg obtained
from the soil samples of the pharmaceutical and ceramic
industrial sites respectively are within the natural
concentration range of Zn in surface soils of 17-125
mg/kg recommended by Ward (1995). However, the
obtained mean values from the two industrial sites of this
study are less than average value of 42.4 Zn mg/kg
reported by Golia et al. (2009) in their study of Zn and Cu
in surface soils of Central Greece. Nevertheless, higher
range Zn content of 30-3782 mg/kg than 5.4-106 mg/kg
obtained from this study has been reported by Asaah et al.
(2006) in their study of surface soils of the Bassa
Industrial Zone.
The mean Cu content of 16 mg/kg obtained from
soils of the pharmaceutical industrial site in this study is
similar to 17.33 mg/kg reported for agricultural topsoils
in Spain by Rodríguez-Martin et al. (2006). However, the
highest value of 34 mg/kg from the Eastward direction
may probably be ascribed to the passage of industrial
waste water along that sampling area. Generally, the
obtained mean value of 15 mg/kg from the soils of the
vicinity of the two industrial sites of this study is less than
the 28.7 mg/kg reported as mean Cu level by Belivermis
et al. (2008) in their study of heavy metal contents in
urban soils of Istanbul.
Nickel: The Ni concentrations varied considerably for the
two industrial sites (Table 4 and 5) with soil samples from
two locations of the vicinity of pharmaceutical industrial
site having Ni contents that were too low to be detectable.
Peris et al. (2008) had reported higher mean values of Ni
in their study than obtained in this study. However, the
findings of this research revealed that Ni contents in the
studied soil samples from the vicinity of the two industrial
sites decrease with increase in distance from the point
source, which may probably be ascribed to the
observation by Nriagu (1990), that the burning of fossil
fuels to generate energy needed to sustain industrial
activities account for more than 80% of pollutant Ni.
Correlation Analysis: Correlation studies of the analyzed
heavy metals with soil properties (Table 6) indicated that
for ceramic industrial site only Cu and Zn correlated
positively with silt and pH respectively. Moreover, for
pharmaceutical industrial site, there was positive
correlation between organic carbon and Cu, Zn and Ni.
Furthermore, Table 7 depicts that there is positive
correlation between Cu and Ni, as well as between Zn and
Pb in all the soils studied.
CONCLUSION
Cu and Zn contents in the soils from the vicinity
of the two industrial sites studied were substantially
higher than twice that of the control soils. Although, the
Pb and Ni concentrations in background levels were
too low to be detectable, the extent of contamination was
not well pronounced for Ni with average content of
1.9±0.96 mg/kg for all the studied soils. However, the
obtained mean value of 18±7.5 mg/kg for Pb from all the
soil samples studied signifies enrichment or accumulation
of Pb above background levels in the urban soils of this
study. Hence, the need for public awareness and
monitoring of possible risks that could arise through the
food chain from heavy metal contamination of soils.
Zinc: Table 4 and 5 revealed that only few sampling
points had zinc contents of less than 10 mg/kg in the soils
of the vicinity of the two industrial sites studied.
However, higher Zn values were obtained from the
pharmaceutical industrial site than in the ceramic
industrial site, probably due to the observation that the
whole surrounding environment of the pharmaceutical
industrial site has been converted to cultivated farmlands.
Several researchers such as Andreu and Gimeno (1996) as
well as Alloway and Ayres (1997) had stated that
agricultural chemicals or materials such as impurities in
fertilizers, pesticides and wastes from intensive poultry
production constitute the very essential non-point sources
174
Res. J. Environ. Earth Sci., 4(2): 171-176, 2012
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