Asian Journal of Agricultural Sciences 4(4): 291-297, 2012
ISSN: 2041-3890
© Maxwell Scientific Organization, 2012
Submitted: May 11, 2012
Accepted: May 29, 2012
Published: July 15, 2012
The Uptake of Lead by Maize Grown on Selected Agricultural Areas
of Kaduna Metropolis, Nigeria
S.S. Mohammed, M.B. Mohammed and N. Musa
Department of Applied Science, College of Science and Technology, Kaduna Polytechnic,
Kaduna, Nigeria
Abstract: The research was carried out to determine the uptake of the metal by maize from soil samples of
Kaduna, Nigeria. The lead concentrations of the maize and soil samples were determined using Flame
Atomic Absorption Spectrometry (FAAS). The soil samples related to the maize were digested and
extracted using different digestion and extraction reagents. The results indicated that the soil samples
collected from various locations contain varying amounts of Lead and was distributed between residual,
Oxide and carbonate/organic fractions. The result of the study also showed that in all the sample locations,
the Pb contained in the soil was below the tolerable limit of 200 mg/kg and the ANOVA (p = 0.000<0.05)
showed a significant difference in both the Lead concentrations across the various maize crops and across
the various maize grown soils.
Keywords: Atomic absorption spectrometry, kaduna metropolis, lead, maize, soil
INTRODUCTION
MATERIALS AND METHODS
In many developing countries like Nigeria, soils
are affected by mine waste disposal, acid deposition,
sewage sludge and other anthropogenic and agricultural
practices. Heavy metal contamination of arable soils
through industrial and anthropogenic activities is a
serious problem in Nigeria. The impact of
contamination on the environment should be of
scientific concern in order to minimize the threat of soil
and groundwater contamination (Matos et al., 2001).
Much research has been conducted on heavy
metals contamination in soils from various
anthropogenic sources such as industrial wastes
(Adeniyi and Okediye, 2004; Yusuf, 2006), automobile
emissions (Arowolo et al., 2000), mining activity
(Kabala and Singh, 2001) and agricultural practice
(Ayodele and Mohammed, 2011; Khairah et al., 2009).
Heavy metals may be distributed among many
components of the soil or sediment and may be
associated with them in different ways (Harrison et al.,
1981; Chlopecka et al., 1996; Kabala and Singh, 2001;
Khairah et al., 2009; Ayodele and Mohammed, 2011).
Therefore the identification of chemical forms or
phases of Pb in soil is necessary for estimating its
biological availability, physico-chemical reactivity and
transport in the environment and into the food chain
(Yaman and Yusuf, 2002a). In this research, Pb
concentration in maize and soil samples were extracted
using the chemical reagents such as the mixture of
HNO3/H2O2; Oxalic acid, Na2 EDTA and acetic acid.
The relation between the maize and soil extracts lead
contents was investigated.
A flame atomic absorption spectrophotometer
model 8010 Young Lin was used for the Pb
determination. In the extraction procedures, 1.0 M
oxalic acid, 0.05 M Na2EDTA and 1.0 M acetic acid
were used.
Preparation of samples: The research covered seven
agricultural sites in Kaduna, Nigeria. The sites are:
Nasarawa (NS), Sabon Tasha (ST), Unguwar Muazu
(UM), Tudun Wada (TW), Kakuri (KK), Mando (MD),
Kabala (KB) west and Kachia (KC). The samples were
collected during the harvest season (Oct-Nov., 2008,
2009 and 2010). The soil samples were collected from
the different areas enumerated at a depth of about 10
cm below the surface (Yaman et al., 2005). The cereal
samples were collected at each of the locations. Maize
was chosen for the purpose of this research work as it is
the staple food being produced and consumed in these
areas. Kachia, a town situated about 130 km away from
Kaduna was taken as a control Fig. 1. The cereal was
thoroughly washed with water and allowed to drain on
a filter paper. Both the cereal and soil samples were
dried at 85ºC. All the analyses were carried out in the
analytical laboratory of the department of Applied
Science, College of Science and Technology, Kaduna
Polytechnic, Kaduna-Nigeria
Wet ashing of cereal: Five (5) g of oven dried maize
sample was accurately weighed into an evaporating
dish and ashed at 480ºC in an ashing furnace for 4 h.
Ten cm³ of a mixture of nitric acid-hydrogen peroxide
Corresponding Author: S.S. Mohammed, Department of Applied Science, College of Science and Technology, Kaduna
Polytechnic, Kaduna, Nigeria
291
Asian J. Agric. Sci., 4(4): 291-297, 2012
Fig. 1: Map of Kaduna metropolis showing the sampling sites
292 Asian J. Agric. Sci., 4(4): 291-297, 2012
(2+1) was added to the ashed sample and dried with
occasional shaking on a hot plate and cooled, 4 cm³ of
1.5 mol/L nitric acid was then added and centrifuged.
Sixty cm³ water was added to the clear digest and was
filtered. This was analysed for Pb using FAAS model
8010 Young Lin. A blank digest was carried out in the
same way.
Digestion and extraction of soil: Soil pH was
measured (1:5, w/v) by digital pH meter. A modified
Tessier et al. (1979) extraction method developed by
Yaman et al. (2005) was used. Ten cm³ of a mixture of
nitric acid-hydrogen peroxide (2+1) was added to 5 g of
soil sample and dried with occasional shaking on a hot
plate and cooled. Four cm³ of 1.5 mol/L nitric acid was
added to the remainder, centrifuged and diluted to 60
cm³ with water and filtered. The clear digest was
analysed for Pb using FAAS model 8010 Young Lin. A
blank digest was carried out in the same way. Soil
extracts were obtained by shaking separately, 5 g of soil
samples with 10 cm³ of 0.05 mol/L Na2EDTA (for
carbonate and organically bound phases), 1.0 mol/L
oxalic acid (for oxide phases) and 1.0 mol/L acetic acid
(for carbonate phases). The mixture was evaporated
with occasional shaking on a hot plate. Four cm³ of 1.5
mol/L nitric acid was added to the remainder and
centrifuged. This is referred to as hot extraction. The
digest was diluted to 60 cm³ and analyzed for Pb using
FAAS model 8010 Young Lin. A blank digest was
carried out in the same way.
RESULTS
Lead content in maize and soils: The lead content for
the samples from the different sampling locations is
shown in Table 1-8. The results from the sampling
locations indicate higher concentrations of the metal in
maize than the corresponding soil. The concentration of
the metal in KK is higher in soil than the corresponding
maize sample. This is in agreement with the results by
other investigators who observed similar variations
(Yaman et al., 2000; Yaman and Bakirdere, 2002b;
Wieczorek et al., 2005; Ana-Irina et al., 2008).
The concentration of the metal in soil was highest
in MD5, MD6, MD8, KK5 and KK6. In all the
sampling locations, the Pb content in the soil was below
the tolerance limit of 200 mg/kg (Lindsay and Norvell,
1978).
The ANOVA (p = 0.000<0.05) showed a
significant difference in the Lead concentrations across
the various maize samples. The differences in Lead
concentrations can further be deduced by a post-hoc test
using the Duncan Multiple range test where the means
of homogeneous subgroups are clearly displayed.
Moreover, the mean plots that follow depict the mean
values of the Lead concentrations across the various
maize crops.
The Duncan multiple range tests indicated that
Sabon Tasha and Kachia had the least Lead
concentration in maize crops. While Mando and
Nasarawa had the highest Lead concentration as
depicted in Fig. 2.
Metal speciation: The Pb distribution in the soil
samples collected from the sampling locations, varied
from one site to other. The metal exists in the forms;
residual, oxide, Fe-Mn oxide and carbonate/organic.
The concentration of the metal bound to residual
fraction is highest in KB, KK , TW and UM .
Therefore, Pb is said to be residual species,
bioavailable, mobile and available for plant uptake in
these locations (Yaman et al., 2000; Baranowski et al.,
2002; Yaman and Bakirdere, 2002b). The concentration
of Pb bound to carbonate/organic fraction is highest in
NS and ST. The metal is said to be organically bound.
Thus, bioavailable, mobile and available for plant
Table 1: Results of Pb concentrations in maize and soil samples at Kabala
Hot extraction
----------------------------------------------------------------------------------------------------------------Metal conc in
Metal conc in
soil sample HNO3
maize sample
Sample site
pH
EDTA 0.05 M
Oxalic acid 1.0 M
Acetic acid 1.0 M
HNO3/H2O2(2+1)
H2O2 (2+1)
KB1
KB2
KB3
KB4
KB5
KB6
KB7
KB8
5.16
5.46
5.36
5.26
5.66
6.12
6.12
6.12
4.05±0.9
4.05±0.9
38.33±1.7
36.67±3.3
38.33±1.7
40.00±1.7
40.00±1.7
40.00±1.7
3.33±1.7
3.33±1.7
25.00±1.7
31.11±3.5
26.67±1.7
28.50±3.1
26.67±3.3
28.33±1.7
3.33±1.7
3.33±1.7
23.33±3.3
6.67±1.7
25.00±3.3
26.67±3.3
26.67±1.7
26.67±1.7
Results of mean values (mg/kg) ±standard deviation (n = 3)
293 6.67±1.7
6.67±1.7
31.67±1.7
5.00±1.7
30.00±1.7
33.33±1.7
31.83±3.6
31.67±3.3
11.67±1.7
11.67±1.7
25.00±1.7
6.67±3.3
25.00±1.7
26.67±1.7
26.67±3.3
28.33±3.3
Asian J. Agric. Sci., 4(4): 291-297, 2012
Table 2: Results of Pb concentrations in maize and soil samples at Nasarawa
Hot extraction
---------------------------------------------------------------------------------------------------------------Metal conc in
Metal conc in
soil sample HNO3
maize sample
Sample site
pH
EDTA 0.05 M
Oxalic acid 1.0 M
Acetic acid 1.0 M
HNO3/H2O2(2+1)
H2O2 (2+1)
NS1
5.49
5.00±1.7
5.00±1.7
6.67±1.7
21.67±1.7
13.33±1.7
NS2
6.12
58.33±3.3
51.67±1.7
91.67±3.3
71.67±3.3
51.67±3.3
NS3
5.33
60.00±3.3
53.33±1.7
91.67±3.3
74.44±3.5
53.33±1.7
NS4
5.92
40.00±1.7
31.67±3.3
6.67±1.7
5.00±3.3
6.67±1.7
NS5
6.12
60.00±1.7
53.33±1.7
93.33±1.7
73.33±1.7
53.33±1.7
NS6
6.45
61.67±3.3
53.33±1.7
95.00±3.3
75.00±1.7
55.00±3.3
NS7
6.45
60.00±1.7
55.00±3.3
93.33±3.3
75.00±1.7
53.33±1.7
NS1
5.49
5.00±1.7
5.00±1.7
6.67±1.7
21.67±1.7
13.33±1.7
Results of mean values (mg/kg) ±standard deviation (n = 3)
Table 3: Results of Pb concentrations in maize and soil samples at Mando
Hot extraction
---------------------------------------------------------------------------------------------------------------Metal conc in
Metal conc in
soil sample HNO3
maize sample
Sample site
pH
EDTA 0.05 M
Oxalic acid 1.0 M
Acetic acid 1.0 M
HNO3/H2O2(2+1)
H2O2 (2+1)
MD1
4.15
3.33±1.6
10.00±1.6
5.00±1.4
31.67±1.6
21.67±1.6
MD2
4.45
60.00±1.7
58.33±3.3
50.00±16.7
73.33±3.3
55.00±3.3
4.56
58.33±3.3
56.67±1.7
51.67±1.7
73.33±1.7
56.67±1.7
MD3
4.35
11.67±1.7
21.67±1.7
11.67±3.3
41.67±3.3
31.67±3.3
MD4
4.26
61.67±1.7
61.67±1.7
51.67±1.7
75.00±1.7
56.67±1.7
MD5
4.75
63.33±1.7
61.67±1.7
53.33±1.7
76.67±3.3
66.67±3.3
MD6
4.75
63.33±3.3
61.11±3.5
53.33±1.7
76.83±1.9
58.33±3.3
MD7
4.75
63.33±1.7
61.67±1.7
53.33±1.7
76.67±1.7
58.33±1.7
MD8
Results of mean values (mg/kg) ±standard deviation (n = 3)
Table 4: Results of Pb concentrations in maize and soil samples at Kakuri
Hot extraction
-------------------------------------------------------------------------------------------------------------Metal conc in
Metal conc in
soil sample HNO3
maize sample
HNO3/H2O2(2+1)
H2O2 (2+1)
Sample site
pH
EDTA 0.05 M
Oxalic acid 1.0 M
Acetic acid 1.0 M
5.08
2.50±1.7
2.50±1.7
6.25±1.7
15.00±1.7
10.00±7.3
KK1
KK2
4.98
56.67±3.3
58.33±3.3
46.67±3.3
43.33±1.7
46.67±1.7
5.14
58.33±1.7
60.00±1.7
48.33±3.3
45.00±3.3
48.33±1.7
KK3
5.14
11.67±1.7
21.67±1.7
11.67±3.3
41.67±3.3
31.67±3.3
KK4
KK5
4.34
61.67±1.7
61.67±1.7
51.67±1.7
75.00±1.7
56.67±1.7
5.15
63.33±1.7
61.67±1.7
53.33±1.7
76.67±3.3
66.67±3.3
KK6
4.5
63.33±3.3
61.11±3.5
53.33±1.7
76.83±0.0
58.33±3.3
KK7
KK8
4.5
26.09±0.7
26.83±0.7
22.36±1.5
20.87±0.7
21.61±1.5
Results of mean values (mg/kg) ±standard deviation (n = 3)
Table 5: Results of Pb concentrations in maize and soil samples at T/wada
Hot extraction
-------------------------------------------------------------------------------------------------------------Metal conc in
Metal conc in
soil sample HNO3
maize sample
HNO3/H2O2(2+1)
H2O2 (2+1)
Sample site
pH
EDTA 0.05 M
Oxalic acid 1.0 M
Acetic acid 1.0 M
TW1
5.07
3.33±1.7
3.33±1.7
8.33±1.7
20.00±1.7
13.33±7.3
TW2
5.12
50.00±16.7
18.33±1.7
13.33±3.3
6.67±3.3
TW3
5.25
53.33±1.7
20.00±1.7
15.00±1.7
6.67±3.3
10.00±1.7
TW4
5.27
18.33±1.7
15.00±1.7
13.33±1.7
11.67±1.7
13.33±1.7
TW5
5.17
51.67±1.7
51.67±1.7
15.00±1.7
8.33±1.7
10.00±3.3
TW6
5.49
53.33±1.7
21.67±1.7
16.67±1.7
10.00±1.7
11.67±3.3
TW7
5.49
51.67±1.7
21.67±1.7
16.67±1.7
8.33±1.7
11.67±1.7
5.49
51.67±1.7
21.67±1.7
TW8
Results of mean values (mg/kg) ±standard deviation (n = 3)
15.00±3.3
10.00±1.7
11.67±1.7
294 8.33±3.3
Asian J. Agric. Sci., 4(4): 291-297, 2012
Table 6: Results of Pb concentrations in maize and soil samples at S/tasha
Hot extraction
-------------------------------------------------------------------------------------------------------------Metal conc in
Metal conc in
soil sample HNO3
maize sample
HNO3/H2O2(2+1)
H2O2 (2+1)
Sample site
pH
EDTA 0.05 M
Oxalic acid 1.0 M
Acetic acid 1.0 M
ST1
5.14
5.00±1.7
5.00±1.7
10.00±1.7
20.00±1.7
11.67±1.7
ST2
5.20
15.00±3.3
11.67±3.3
13.33±3.3
10.00±1.7
10.00±3.3
ST3
5.25
15.00±3.3
13.33±3.3
11.67±3.3
10.00±3.3
10.00±1.7
ST4
5.82
20.00±1.7
16.67±1.7
15.00±3.3
13.33±1.7
15.00±1.7
ST5
5.25
16.67±1.7
13.33±3.3
15.00±1.7
11.67±1.7
11.67±3.3
6.10
16.67±1.7
15.00±1.7
16.67±3.3
13.33±3.3
13.33±1.7
ST6
ST7
6.10
16.67±1.7
15.00±3.3
16.67±1.7
13.33±1.7
11.67±3.3
ST8
6.10
15.00±3.3
13.33±3.3
15.00±1.7
11.67±3.3
11.67±1.7
Results of mean values (mg/kg) ±standard deviation (n = 3)
Table 7: Results of Pb concentrations in maize and soil samples at U/muazu
Hot extraction
-------------------------------------------------------------------------------------------------------------Metal conc in
Metal conc in
soil sample HNO3
maize sample
HNO3/H2O2(2+1)
H2O2 (2+1)
Sample site
pH
EDTA 0.05 M
Oxalic acid 1.0 M
Acetic acid 1.0 M
UM1
4.01
3.33±1.7
6.67±1.7
8.33±1.7
13.33±1.7
13.35±1.6
UM2
4.10
53.33±1.7
11.67±3.3
10.00±1.7
8.33±3.3
10.00±3.3
UM3
4.22
55.00±3.3
13.33±1.7
11.67±3.3
10.00±1.7
11.67±3.3
UM4
5.82
18.33±1.7
16.67±1.7
13.33±3.3
15.00±3.3
13.33±3.3
UM5
4.11
55.00±1.7
13.33±1.7
11.67±3.3
10.00±3.3
8.33±3.3
UM6
4.54
56.67±3.3
15.00±3.3
13.33±3.3
11.67±1.7
13.33±1.7
UM7
4.54
55.00±1.7
15.00±1.7
13.33±1.7
10.00±1.7
13.33±1.7
4.54
55.00±1.7
15.00±1.7
UM8
Results of mean values (mg/kg) ±standard deviation (n = 3)
11.67±3.3
10.00±1.7
13.33±1.7
Table 8: Results of Pb concentrations in maize and soil samples at Kachia
Sample site
KC1
KC2
KC3
KC4
KC5
KC6
KC7
KC1
pH
6.16
6.24
6.15
6.08
6.07
6.14
6.01
6.16
Metal conc in
maize sample
HNO3/H2O2(2+1)
18.33±1.7
30.00±3.3
30.00±3.3
30.00±10.2
25.00±1.7
17.44±21.6
26.67±1.7
18.33±1.7
Hot extraction
-------------------------------------------------------------------------------------------------------------Metal conc in
soil sample HNO3
H2O2 (2+1)
EDTA 0.05 M
Oxalic acid 1.0 M
Acetic acid 1.0 M
13.33±1.7
26.67±1.7
28.33±3.3
28.33±5.6
11.67±1.7
14.73±19.5
6.67±1.7
13.33±1.7
11.67±1.7
35.00±1.7
25.00±3.3
25.00±9.8
6.67±1.7
16.71±20.1
5.00±1.7
11.67±1.7
15.00±3.3
35.00±1.7
36.67±1.7
36.67±5.3
3.33±1.7
13.99±18.0
5.00±3.3
15.00±3.3
11.67±3.3
26.67±1.7
26.67±3.3
26.67±7.7
5.00±1.7
13.99±18.2
5.00±1.7
11.67±3.3
Results of mean values (mg/kg) ±standard deviation (n = 3)
uptake Similar results were reported by other workers
working under similar conditions (Yaman et al., 2000;
Takac et al., 2009).
The metal concentration bound to oxide fraction is
highest in KB, MD, KK and KC. Thus, is said to be
oxide species and available for plant uptake in these
locations. Similar results were observed by several
authors working in similar situations (Yaman et al.,
2000; Feng et al., 2009).
The Pb concentration associated with Fe-Mn oxide
fraction is highest in MD and ST. The metal is said to
be Fe-Mn oxide species, bioavailable, mobile and
available for plant uptake in these sampling locations
(Urunmatsoma et al., 2010).
The pH of the soil samples from all the locations is
acidic. This could be attributed to heavy traffic
anthropogenic and agricultural activities on the
sampling sites (Yusuf, 2007; Chamon et al., 2009;
Khairah et al., 2009). The bioavailability of lead
decreases with increasing pH (Moraghan and Mascani,
1991; Morel, 1997).
295 Me an of le ad concentration
in maize sample (mg/K g)
Asian J. Agric. Sci., 4(4): 291-297, 2012
contamination potential. The results on heavy metal
speciation in the study indicated that the soil samples
collected from various areas contain varying amounts
of the metal. The metal was distributed between
residual, oxide and carbonate fractions. An increase of
the metal concentration in some areas suggests that
heavy use of agrochemical materials for planting
activities could cause increase in the content of heavy
metals in the soil.
60.00
50.00
40.00
30.00
20.00
Ka
ch
ia
Ka
ba
la
we
st
Na
s ar
aw
a
Ma
nd
o
Ka
ku
ri
Tu
du
nw
ada
Sa
bo n
ta s
Un
ha
gw
an
mu
az
u
10.00
Sites
Fig. 2: Mean plot for lead concentration in maize crops
Mean of lead concentr a tion
in soil sample (mg/K g)
50.00
ACKNOWLEDGMENT
The authors show great appreciation to Kaduna
Polytechnic, Nigeria for providing facilities to analyze
the samples and to Kabiru Shehu and Yusuf Abdul
Raheem, for the help in sample collection, metal and
statistical analyses.
REFERENCES
40.00
30.00
20.00
Ka
ch i
a
Sab
on
t as
ha
Un
gw
an
mu
az
u
ri
nw
a da
Ka
ku
Tu
du
Ka
ba
la w
est
Na
sa r
aw
a
Ma
n do
10.00
Sites
Fig. 3: Mean plot for lead concentration in maize grown soil
The ANOVA (p = 0.000<0.05) indicated a
significant difference in the Lead concentrations across
the various maize soils. The real differences of Lead
concentrations in maize soils can further be analyzed by
a post-hoc test using the Duncan Multiple range test
where the means of homogeneous subgroups are
displayed. Moreover, the mean plots clearly depict the
mean values of the Lead concentrations across the
various maize soils.
The Duncan multiple range tests showed that
Sabon Tasha and Ungwan Muazu had the least Lead
concentration in maize soils. While kakuri, Nasarawa
and Mando had the highest Lead concentration in soil
as depicted in Fig. 3.
CONCLUSION
Total trace metal composition of soil is of little
importance in determining its uptake by plants and
consequently, in contaminating the food chain since the
different
forms
have
different
mobilities,
bioavailabilities
and
potential
environmental
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