British Journal of Pharmacology and Toxicology 3(3): 140-146, 2012
ISSN: 2044-2467
© Maxwell Scientific Organization, 2012
Submitted: May 11, 2012
Accepted: May 29, 2012
Published: June 30, 2012
Content of Copper in Maize and Soil Collected from Selected Agricultural Areas
in Kaduna, Nigeria
S.S. Mohammed, M.B. Mohammed and N. Musa
Department of Applied Science, College of Science and Technology, Kaduna Polytechnic,
Kaduna, Nigeria
Abstract: This study was conducted to determine the content of maize in soil so as to evaluate its mobility,
bioavailability and eco-toxicity. The copper content of maize and soil samples was 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 Cu and was distributed between Residual,
Oxide and Carbonate/Organic fractions. The result of the study also showed that, in some of the sampling
locations, the Cu content in the soil was above the tolerance limit of 100 mg/kg and the ANOVA (p =
0.000<0.05) indicated a significant difference in both the copper concentrations across the various maize
crops and maize grown soils.
Keywords: Atomic absorption spectrometry, copper content, kaduna metropolis, maize, soil
INTRODUCTION
oxalic acid, 0.05 M Na2EDTA and 1.0 M acetic acid
were used.
Concerns over the possible build-up of heavy
metals in soils resulting from large applications of
sewage sludge has prompted research on the fate of
these chemicals in soils. Most attention has been given
to Zinc, Copper, Nickel, Cadmium and Lead which are
present at significant levels in sludge (Jones, 1991).
Heavy metal contamination in arable soils through
industrial and anthropogenic activities is a serious
problem in Nigeria. Metals uptake by plants may pose
risks to human health when such plants are grown on or
near contaminated areas. Metal accumulation in plants
depends on plant species, growth stages, types of soil
and metals, soil conditions, weather and environment
(Chang et al., 1984; Petruzzelli, 1989). A large number
of extracting solutions have been used to assess plant
available trace elements (Gupta and Aten, 1993; He and
Singh, 1993; Mohammed and Ayodele, 2011). In this
research, the extractable Cu in soil samples was
determined by Flame Atomic Absorption Spectrometry
(FAAS). The soil samples were extracted using the
chemical reagents, 0.05 M EDTA, 1.0 M acetic acid
and 1.0 M oxalic acid. The relation between the maize
and soil extracts lead contents was investigated.
Preparation of samples: The research covered seven
agricultural sites in Kaduna, Nigeria. The sites are:
Nasarawa (NS), Sabon Tasha (ST), UnguwarMuazu
(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. Guinea
corn was chosen for the purpose of this research study
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 guinea
corn sample was accurately weighed into an
evaporating dish and ashed at 480°C in an ashing
furnace for 4 h. Ten cm³ of a mixture of nitric acidhydrogen peroxide (2+1) was added to the ashed
sample and dried with occasional shaking on a hot plate
MATERIALS AND METHODS
A flame atomic absorption spectrophotometer
model 8010 Young Lin was used for the Cu
determination. In the extraction procedures, 1.0 M
Corresponding Author: S.S. Mohammed, Department of Applied Science, College of Science and Technology, Kaduna
Polytechnic, Kaduna, Nigeria
140
Br. J. Pharmacol. Toxicol., 3(3): 140-146, 2012
Fig. 1: Map of Kaduna metropolis showing the sampling sites
141 Br. J. Pharmacol. Toxicol., 3(3): 140-146, 2012
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
Cu 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 Cu 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 Cu using
FAAS model 8010 Young Lin. A blank digest was
carried out in the same way.
to agricultural processes and other human activities in
the sampling locations. Similar results were reported by
other workers working under similar conditions (AnaIrina et al., 2008; Urunmatsoma et al., 2010). A higher
Cu concentration was observed in soil than the
corresponding maize samples in NS and ST (Takac
et al., 2009; Urunmatsoma et al., 2010).
In some of these sampling locations, the Cu
concentration in the soil was above the tolerance limit
of 100 mg/kg (Lindsay and Norvell, 1978).
The Cu highest concentration in the areas is not
only a problem to plant nutrition and food chain; it may
constitute a direct health hazard as well Seward and
Richardson (1990).
The ANOVA (p = 0.000<0.05) indicated a
significant difference in the Copper concentrations
across the various maize crops. The differences in
Copper concentrations can further be deduced by a
post-hoc test using the Duncan Multiple range test
where means of homogeneous subgroups are clearly
displayed. Moreover, the mean plots that follow will
clearly depict the mean values of the Copper
concentrations across the various maize crops.
The Duncan multiple range tests showed that, Kakuri,
Nasarawa, among others had the least Copper
concentration in maize crops. While Sabon Tasha and
Ungwan Muazu had the highest copper concentration as
depicted in Fig. 2.
RESULTS
Copper content in maize and soils: The copper
content for the sample collected from the sampling
locations is shown in Table 1-8. The results of the Cu
concentration in maize and soil varied from one
location to the other. The results of the Cu
concentrations in KB, MD, KK, TW, UM and KC
indicate higher concentrations of the metal in maize
than in corresponding soil samples. This could be due
Metal speciation: The Cu distribution in the soil
samples from the sampling locations varied from one
sampling site to another. The metal exists in the forms;
the residual, oxide and carbonate/organic. The
concentration of the metal bound to carbonate/organic
phase is highest in KB, TW. The copper in these soils
was organically bound and hence bioavailable and
mobile (Hickey and Kittrick, 1984; Urunmatsoma et al.,
2010).
Table 1: Results of Cu concentrations in maize and soil samples at Kabala
Hot extraction
--------------------------------------------------------------------------------------------------------Metal conc in
Metal conc in soil
G/corn sample
sample HNO3/H2O2
Oxalic
Acetic
Sample site
pH
HNO3/H2O2 (2+1)
(2+1)
EDTA 0.05 M
acid 1.0 M
acid 1.0 M
5.16
nd
nd
1.15±0.6
1.73±0.6
0.63±0.5
KB1
KB2
5.46
12.69±0.6
2.88±0.6
6.92±0.6
1.73±0.6
3.46±1.2
KB3
5.36
13.85±0.6
2.88±0.6
7.50±1.2
2.31±0.6
2.88±0.6
KB4
5.26
12.12±0.6
10.96±1.2
1.73±1.2
2.31±0.6
1.73±0.6
KB5
5.66
13.27±0.6
3.46±0.6
7.50±0.6
2.31±0.6
4.04±0.6
KB6
6.12
13.85±0.6
4.04±0.6
7.50±1.2
2.88±0.6
4.62±0.6
KB7
6.12
13.85±0.6
3.46±0.6
8.08±1.2
2.31±0.6
4.04±1.2
KB8
6.12
13.85±0.6
3.46±0.6
8.65±0.6
2.88±1.2
3.46±0.6
Results of mean values (mg/kg) ± standard deviation (n = 3)
142 Br. J. Pharmacol. Toxicol., 3(3): 140-146, 2012
Table 2: Results of cu concentrations in maize and soil samples at Nasarawa
Hot extraction
----------------------------------------------------------------------------------------------------Metal conc in
Metal conc in soil
G/corn sample
sample HNO3/H2O2
Oxalic
Acetic
(2+1)
EDTA 0.05 M
acid 1.0 M
acid 1.0 M
Sample site
pH
HNO3/H2O2 (2+1)
NS1
5.49
nd
nd
3.46±0.6
3.46±0.6
2.31±0.6
NS2
6.12
5.77±0.6
6.92±0.6
4.62±0.6
5.19±0.6
4.62±0.6
NS3
5.33
5.77±0.6
6.92±0.6
4.04±1.2
4.62±0.6
4.62±1.2
NS4
5.92
5.77±0.6
4.62±0.6
4.04±1.2
3.46±0.6
2.88±1.2
NS5
6.12
6.35±0.6
7.50±0.6
5.19±0.6
5.77±0.6
5.19±1.2
NS6
6.45
6.92±0.6
8.08±1.2
5.77±0.6
6.35±0.6
5.77±1.2
NS7
6.45
6.35±0.6
8.08±0.6
5.19±1.2
6.35±0.6
5.19±1.2
NS8
6.45
7.50±0.6
8.65±1.2
5.77±0.6
6.35±0.6
5.77±0.6
Results of mean values (mg/kg) ± standard deviation (n = 3)
Table 3: Results of cu concentrations in maize and soil samples at Mando
Hot extraction
---------------------------------------------------------------------------------------------------Metal conc in
Metal conc in soil
G/corn sample
sample HNO3/H2O2
Oxalic
Acetic
(2+1)
EDTA 0.05 M
acid 1.0 M
acid 1.0 M
Sample site
pH
HNO3/H2O2 (2+1)
MD1
4.15
nd
nd
2.31±0.6
4.04±0.6
4.04±0.6
MD2
4.45
31.15±1.2
8.65±0.6
8.08±1.2
13.27±1.2
9.81±1.2
MD3
4.56
31.73±0.6
9.23±1.2
8.08±1.2
13.85±0.6
10.38±0.6
MD4
4.35
26.34±5.9
29.27±2.9
17.56±2.9
26.34±5.9
23.41±2.9
MD5
4.26
160.98±2.9
160.98±2.9
43.90±5.9
67.32±2.9
52.68±5.9
MD6
4.75
163.90±2.9
49.76±2.9
46.83±2.9
73.17±2.9
55.61±5.9
MD7
4.75
163.90±2.9
46.83±5.9
46.83±2.9
70.24±2.9
55.61±5.9
MD8
4.75
160.98±2.9
49.76±2.9
46.83±2.9
73.17±2.9
52.68±2.9
Results of mean values (mg/kg) ± standard deviation (n = 3)
Table 4: Results of Cu concentrations in maize and soil samples at Kakuri
Hot extraction
---------------------------------------------------------------------------------------------------Metal conc in
Metal conc in soil
G/corn sample
sample HNO3/H2O2
Oxalic
Acetic
Sample site
pH
HNO3/H2O2 (2+1)
(2+1)
EDTA 0.05 M
acid 1.0 M
acid 1.0 M
KK1
5.08
nd
nd
1.73±0.6
1.15±0.6
1.73±0.6
KK2
4.98
20.77±1.2
8.08±1.2
9.81±1.2
9.23±1.2
9.23±1.2
5.14
13.85±0.6
11.54±0.6
10.96±1.2
9.23±0.6
9.23±1.2
KK3
KK4
5.14
5.19±1.2
3.46±0.6
2.88±1.2
2.31±0.6
2.88±0.6
KK5
4.34
13.85±0.6
13.85±0.6
9.23±0.6
10.38±0.6
9.81±1.2
KK6
5.15
14.42±0.6
6.35±0.6
11.54±0.6
9.81±1.2
10.96±0.6
4.5
14.42±0.6
11.54±0.6
10.96±1.2
9.81±0.6
10.38±0.6
KK7
KK8
4.5
13.85±0.6
11.54±1.2
10.96±1.2
9.23±0.6
10.38±0.6
Results of mean values (mg/kg) ± standard deviation (n = 3)
Table 5: Results of cu concentrations in maize and soil samples at T/WADA
Hot extraction
---------------------------------------------------------------------------------------------------Metal conc in
Metal conc in soil
Oxalic
Acetic
G/corn sample
sample HNO3/H2O2
Sample site
pH
HNO3/H2O2 (2+1)
(2+1)
EDTA 0.05 M
acid 1.0 M
acid 1.0 M
TW1
5.07
nd
nd
1.73±0.6
1.15±0.6
1.73±0.6
TW2
5.12
20.77±1.2
8.08±1.2
9.81±1.2
9.23±1.2
9.23±0.6
TW3
5.25
21.92±0.6
8.65±0.6
10.38±0.6
9.23±1.2
9.23±0.6
5.27
5.77±0.6
4.62±0.6
2.88±0.6
2.31±0.6
2.88±0.6
TW4
TW5
5.17
21.35±0.6
21.35±0.6
10.38±0.6
9.81±0.6
9.81±0.6
5.49
21.92±1.2
9.23±0.6
10.96±0.6
10.38±0.6
10.38±1.2
TW6
TW7
5.49
21.35±0.6
9.23±0.6
10.38±1.2
10.38±0.6
9.81±1.2
5.49
21.35±0.6
9.23±0.6
10.96±0.6
9.81±0.6
9.81±1.2
TW8
Results of mean values (mg/kg) ± standard deviation (n = 3)
143 Br. J. Pharmacol. Toxicol., 3(3): 140-146, 2012
Table. 6: Results of cu concentrations in maize and soil samples at S/TASHA
Hot extraction
---------------------------------------------------------------------------------------------------Metal conc in
Metal conc in soil
Oxalic
Acetic
G/corn sample
sample HNO3/H2O2
(2+1)
EDTA 0.05 M
acid 1.0 M
acid 1.0 M
Sample site
pH
HNO3/H2O2 (2+1)
ST1
5.14
ND
ND
2.88±0.6
2.89±0.6
2.31±0.6
ST2
5.20
10.96±1.2
12.69±0.6
9.81±0.6
8.65±1.2
5.77±0.6
5.25
11.54±1.2
13.27±1.2
9.81±1.2
8.65±0.6
6.35±0.6
ST3
5.82
3.46±0.6
7.50±0.6
4.62±0.6
4.62±1.2
4.04±1.2
ST4
5.25
11.54±0.6
13.27±0.6
10.38±0.6
9.23±0.6
6.35±0.6
ST5
6.10
12.12±0.6
13.85±0.6
10.96±0.6
9.81±1.2
6.92±0.6
ST6
6.10
11.54±0.6
13.85±0.6
10.38±1.2
9.81±1.2
6.35±0.6
ST7
6.10
10.96±1.2
13.27±0.6
10.38±0.6
9.23±1.2
5.77±0.6
ST8
Results of mean values (mg/kg) ± standard deviation (n = 3)
Table 7: Results of cu concentrations in maize and soil samples at U/Muazu
Hot extraction
---------------------------------------------------------------------------------------------------Metal conc in
Metal conc in soil
Oxalic
Acetic
G/corn sample
sample HNO3/H2O2
(2+1)
EDTA 0.05 M
acid 1.0 M
acid 1.0 M
Sample site
pH
HNO3/H2O2 (2+1)
UM1
4.01
ND
ND
1.15±0.6
1.15±0.6
1.15±0.6
UM2
4.10
21.92±1.2
7.50±1.2
7.50±0.6
109.62±11.5
126.92±11.5
4.22
22.50±0.6
8.08±0.6
8.08±1.2
109.62±0.6
126.92±1.2
UM3
5.82
5.77±0.6
6.92±0.6
3.46±1.2
3.46±1.2
4.62±0.6
UM4
4.11
22.50±1.2
8.13±0.7
8.08±1.2
115.38±5.8
126.92±5.8
UM5
4.54
23.08±0.6
8.65±0.6
8.65±1.2
121.15±1.2
138.46±1.2
UM6
4.54
22.50±0.6
7.50±0.6
8.65±1.2
8.08±0.6
110.19±0.6
UM7
4.54
22.50±0.6
8.71±0.5
8.65±1.2
109.62±5.8
126.92±0.6
UM8
Results of mean values (mg/kg) ± standard deviation (n = 3)
Table 8: Results of cu concentrations in Maize and soil samples at Kachia
Hot extraction
---------------------------------------------------------------------------------------------------Metal conc in
Metal conc in soil
Oxalic
Acetic
G/corn sample
sample HNO3/H2O2
(2+1)
EDTA 0.05 M
acid 1.0 M
acid 1.0 M
Sample site
pH
HNO3/H2O2 (2+1)
KC 1
6.16
6.35±0.6
14.42±0.6
3.46±0.6
1.15±0.6
1.73±1.2
KC 2
6.24
2.88±1.2
3.46±0.6
2.31±0.6
2.88±0.6
2.31±0.0
KC 3
6.15
79.02±5.9
23.41±2.9
20.49±5.9
32.20±2.9
26.34±2.9
KC 4
6.08
7.50±0.6
5.19±1.2
4.62±1.2
4.04±1.2
4.62±0.6
KC 5
6.07
10.38±0.6
4.04±0.6
5.19±1.2
4.62±1.2
4.62±1.2
KC 6
6.14
4.62±0.6
6.35±0.6
5.19±1.2
4.62±1.2
2.88±1.2
KC 7
6.01
10.96±0.6
4.62±0.6
4.62±1.2
5.19±1.2
6.35±0.6
KC 1
6.16
6.35±0.6
14.42±0.6
3.46±0.6
1.15±0.6
1.73±1.2
Results of mean values (mg/kg) ± standard deviation (n = 3)
The concentration of the metal bound to oxide fraction
is highest in MD. The copper in these locations is said
to be oxide species. Thus, it is bioavailable and mobile.
Similar findings were reported by Hickey and Kittrick
(1984), Takac et al. (2009) and Urunmatsoma et al.
(2010).
The concentration of Cu bound to carbonate
fraction is highest in UM. The metal is said to be
organically bound or carbonate species and hence
bioavailable and mobile. This is in agreement with
other results (Hickey and Kittrick, 1984; Urunmatsoma
et al., 2010). The concentration of the metal bound to
residual fraction is highest in NS, KK, ST and KC. The
metal is said to be residual species in these areas. Thus,
it is bioavailable and mobile (Hickey and Kittrick,
1984; Chamon et al., 2009; Takac et al., 2009;
Urunmatsoma et al., 2010).
The HNO3/H2O2 extractable, EDTA extractable,
CH3COOH extractable, COOH)2 extractable and
C6H8O7 extractable are considered as available Cu in
these locations.
The pH of the soil samples is acidic. Due to the
various agricultural processes (Kashem et al., 2007;
Chamon et al., 2009). The bioavailability of the metal
decreases with increasing pH (Moraghan and Mascani,
1991; Morel, 1997). The acidity of the soils increases
144 Br. J. Pharmacol. Toxicol., 3(3): 140-146, 2012
80.00
60.00
40.00
20.00
a
c hi
Un
gw
an
mu
tas
on
Sa b
Ka
azu
ha
da
ri
wa
ku
dun
Tu
Ka
n do
Ma
Na
b al
aw
sa r
aw
es t
a
0.00
Ka
Mean of copper concentration
in maize sample (mg/Kg)
CONCLUSION
100.00
Sites
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
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.
Fig. 2: Mean plot for copper concentration in maize crops
The authors show great appreciation to Kaduna
Polytechnic, Nigeria for providing facilities to analyze
thesamples and to Kabiru Shehu and Yusuf Abdul
Raheem, for the help in sample collection, metal and
statistical analyses.
40.00
30.00
20.00
REFERENCES
wa
da
on
tas
Un
ha
gw
an
mu
az
u
Ka
ch
ia
Sites
Sab
Ka
kur
i
Ma
n do
Tu
du
n
Ka
ba
Na
s ar
aw
a
10.00
la
we
st
Mean of copper concentration
in soil sample (mg/Kg)
ACKNOWLEDGMENT
50.00
Fig. 3: Mean plot for copper concentration in maize grown
soil
the solubility and mobility of the metal in the soils.
Thus, increasing the availability of the metal for plant
uptake (Baranowski et al., 2002; Takac et al., 2009).
The ANOVA (p = 0.000<0.05) indicated a
significant difference in the Copper concentrations
across the various maize soils. The differences in
Copper concentrations can be deduced by a post-hoc
test using the Duncan Multiple range test where means
of homogeneous subgroups are clearly displayed.
Moreover, the mean plots that follow will clearly depict
the mean values of the Copper concentrations across the
various maize soils.
The Duncan multiple range tests showed that
Kabala West had the least Copper concentration in
maize grown soils. While Mando had the highest
Copper concentration in soil as depicted in Fig. 3.
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