Bull Environ Contam Toxicol (2010) 85:313317

DOI 10.1007/s00128-010-0082-1

Environmental Pollution Levels of Lead and Zinc in Ishiagu

and Uburu Communities of Ebonyi State, Nigeria
Obinna A. Oje Peter N. Uzoegwu
Ikechukwu N. E. Onwurah Uchechukwu U. Nwodo

Received: 23 January 2010 / Accepted: 9 July 2010 / Published online: 21 July 2010
 Springer Science+Business Media, LLC 2010

Abstract Water and soil samples from the area were

therefore analyzed for their lead and zinc content. Computation of pollution statuses of lead and zinc revealed topsoil
lead geoaccumulation indices of -0.143 and -0.069 and
zinc geoaccumulation indices of 1.168 and 0.713 for Ishiagu
and Uburu respectively. The pollution indices were determined to be 0.499 and 0.3564 for soil in Ishiagu and Uburu
respectively and also 5.11 and 2.42 for water in Ishiagu and
Uburu communities respectively. Water/soil concentration
ratio were found to be 0.0018 and 0.0014 for lead in Ishiagu
and Uburu respectively. On the other hand, the water/soil
concentration ratio for zinc was computed to be 0.001 and
0.0008 for Ishiagu and Uburu respectively. These results
seem to suggest that the pollution of the environment by
these heavy metals in the areas were as a result of the water
being contaminated by lead and zinc not necessarily their
concentrations in the soil.
Keywords Lead  Zinc  Geoaccumulation index 
Pollution index  Water/soil concentration ratio

Lead is a heavy metal naturally present in trace amount in

soil, water, plants and animals (Strmiskova 1992). It is a
known environmental toxicant that has no physiological
function in organisms (Neumann et al. 1990). Lead is also
known to affect almost all the organs in the body even at low
O. A. Oje (&)  P. N. Uzoegwu  I. N. E. Onwurah
Department of Biochemistry, Faculty of Biological Sciences,
University of Nigeria, Nsukka, Enugu State, Nigeria
e-mail: obinnaoje@yahoo.com
U. U. Nwodo
Department of Microbiology, University of Nigeria, Nsukka,
Nigeria

concentration. Lead can gain entrance in the environment

through both natural (leaching, weathering and erosion) and
anthropogenic (industrial activities including mining,
exhaust pipe of automobile etc.) means. Mining of lead
which takes place in Ishiagu exposes the environment to
lead. The release of these heavy metals posses a significant
threat to the environment and public health because of their
toxicity, bioaccumulation in the food chain and persistence
in nature (Ceribasi and Yetis 2001). The heavy metal zinc is
not toxic at low concentration but has some undesirable
effect at high concentration. Zinc influences cell division,
growth and development (Beach et al. 1980) as well as
sexual maturation (Coble et al. 1971). It is also a membrane
stabilizer (Chvapil 1973) and essential for the integrity of the
immune system (Schlesinger et al. 1993). Moreover, zinc is
required by more than 100 enzymes as cofactor, and it seems
to help in the proper storage and release insulin, growth and
repair of tissues, wound healing, the ability to taste food,
mineralization of bone, blood clotting, the function of vitamin A, and the functions of the thyroid hormones (Prasad
1983; Hands 1999). Some indices can be used to determine
the level of pollution caused by these metals in the environment. These indices include; the geoaccumulation index
which has been employed in assessing contamination of
soils (Kwapulinski et al. 1996; Miko et al. 2000) and pollution index, which has been used to assess the pollution
levels by putting into consideration the joint effect of all
polluting metals in soil (Lee et al. 1998). This study has
extrapolated this index to water. The use of the water/soil
concentration ratio is another index that can be used to assess
the pollution levels of these metals in the environment. With
these indices, the pollution levels and potential contaminations of these heavy metals can be determined. This study is
therefore aimed at estimating the pollution levels of lead and
zinc in Ishiagu and Uburu communities which have

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Bull Environ Contam Toxicol (2010) 85:313317

commercial accumulation of the metals with a view of

advising the natives for their safety.

Materials and Methods

PerkenElmer flame atomic absorption spectrometer
(FAAS) (model 2380 England), equipped with burner
nebulizer for airacetylene having single slot 100 mm, was
used for carrying out the AAS analysis. The wavelength
and the slit band width of the atomic absorption spectrometer are shown on Table 1.
About 200 g of soil were collected from four different
agricultural soils in Ishiagu in Ivo Local Government Area
and Uburu in Ohaozara Local Government Area both in
Ebonyi State. Top- and sub-soils (topsoil 015 cm depth
and subsoil 1530 cm depth) (Adie and Osibanjo 2009)
were collected. Both soils were collected from the same
locations. The collected soil samples were put in polyethene bag where it was transported to the laboratory and kept
in the refrigerator till use.
Lead and zinc in soil samples were prepared according
to the method of USEPA (1986). The soil samples were
oven dried for 24 h and then ground into powder and
sieved. One gram of each sieved soil sample was placed in
a small beaker and 10 mL of concentrated HNO3 was
added and allowed to stand for 4 h. It was then placed over
a hot plate until the evolution of red nitrogen (IV) oxide
(NO2) fume ceased. The beaker and its content were cooled
and 4 mL of 70% of HClO4 was added. The solution was
gently heated to evaporate to smaller volume. The digested
sample was then made up to 100 mL. This solution is used
for lead and zinc analysis.
Also 2 L of water were collected from streams, wells
and boreholes in different locations in Ishiagu and Uburu.
The water samples were stored in a two litre container at
4C till used. The water samples were prepared according
to the method modified by Eletta (2007). The collected
water samples (100 mL) measured with a measuring cylinder were poured into 200 mL beaker and the water
acidified with five drops of concentrated HNO3 to keep the
metals in solution. The solutions were then concentrated on
a hot plate to 20 mL, cooled and then stored in storage
bottles for AAS analysis.
The concentration of lead and zinc were calculated after
AAS analysis thus;
Table 1 The wavelength and slit band width of the AAS machine

AAS results
Concentration factor
Intial sample volume
Concentration factor
Final volume

Concentration of trace metal

1
2

Pollution index is determined according to the method

of Lee et al. (1998). Pollution index (PI) assesses pollution
level by considering the joint effect of all polluting metals
in soil. The PI is obtained by calculating the average ratios
of metal concentration to the tolerance levels or the metal
concentration above which crop growth are considered
unsafe for human health (Ezeh et al. 2008). It was
computed using the formula as stated below;


1 M1
M2
Mn
Pollution index PI


3
n TL1 TL2
TLn
M1, M2,, Mn are the average concentrations of the polluting metals; TL1, TL2,, TLn are the tolerable levels for
each metal; n is the number of polluting metal considered.
A pollution index of more than 1.0 indicates that the
average metal concentrations are above the permissible
levels.
The index of geoaccumulation (Igeo) measures the bottom sediment contamination (Muller 1969), and was
employed in this study to assess the contamination of soils
(Miko et al. 2000; Kwapulinski et al. 1996). The content
accepted as background in multiplied each time by the
constant 1.5 in order to take into account natural fluctuations of a given substance in the environment as well as
very small anthropogenic influences (Loska et al. 2003).
The value of the geoaccumulation index is described by the
following equation;
Igeo In

Cn
1:5  Bn

Igeo = geoaccumulation index, Cn = concentration of

lead/zinc in the soil, Bn = background value.
The index of geoaccumulation consists of seven grades,
whereby the highest grade (6) reflects 100-fold enrichment
above background values. Listed on Table 2 are the
Table 2 Geoaccumulation index classification (Forstner et al. 1993)
Sediment
geoaccumulation
index (Igeo)

Igeo classes

Contamination
intensity

[5

Very strong

[45

Strong to very strong

[34

Strong

[23

Moderate to strong

[12

Moderate

Element

Wavelength

Slit band width (mm)

Lead (Pb)

283.3

0.7

[01

Uncontaminated to moderate

Zinc (Zn)

213.9

0.7

\0

Practically uncontaminated

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315

geoaccumulation classes and the corresponding contamination intensity for different indices (Forstner et al. 1993).
The water/soil concentration ratio determines or assesses the pollution levels taking into consideration the mean
of the heavy metals in both subsoil and topsoil and the
mean of the heavy metal concentration in the water bodies.
The water/soil concentration index can be calculated thus;
Water/soil Conc: ratio w:s
Mean Conc: of metals in water bodies

Mean Conc: of metals in both top and subsoil

Results and Discussion

The concentrations of lead in the soil were shown in Fig. 1.
When compared with permissible limit of WHO, the concentrations of lead in subsoil in Ishiagu (14.03 0.8 lg/g)
were found to be lower than that in Uburu (16.3
1.70 lg/g) although both were found to be lower than the
WHO permissible limits.
The concentrations of zinc were also determined. Figure 2 shows that the concentration of zinc in topsoil
(245 7.02 lg/g) and subsoil (268.33 3.05 lg/g) in
Ishiagu were found to be higher than the concentration of
zinc in topsoil (154.33 5.68 lg/g) and subsoil
(187.00 4.35 lg/g) in Uburu. The difference in mean
values of zinc in soil in Ishiagu were found to be significantly different at p \ 0.05.

Fig. 1 The mean concentration of lead in topsoil and subsoil in

Ishiagu and Uburu communities

Fig. 2 Barchart showing the mean concentration of zinc in topsoil

and subsoil of both Ishiagu and Uburu communities

The mean concentrations of lead were also determined

in stream, well and borehole water bodies. Figure 3 shows
that the concentration of lead in boreholes in both communities were higher than those of well water and stream
water. Apart from the concentration of lead in Uburu
stream water (0.006 0.002 lg/dl), all other have concentrations significantly higher than the permissible limit
of lead in water.
Figure 4 shows significantly high concentration of zinc
above the permissible limit for zinc in drinking water. The
concentrations of zinc ranges from 0.172 0.001 to
0.383 0.001 lg/dL in well water in Ishiagu and
0.126 0.003 to 0.156 0.007 lg/dL in Uburu.
The result below in Table 3 shows that Ishiagu has
higher pollution indices for both soil and water than Uburu.
It also showed that pollution index (combined effect of lead
and zinc) is higher in water than in soil.
The geoaccumulation indices of lead and zinc were
calculated and the result showed that the level of contamination caused by zinc is within the range described as
uncontaminated to moderate contamination while lead
was calculated to show practically uncontaminated as
seen in Table 4.
The water/soil concentration ratio was found to be
higher in Ishiagu than in Uburu for both lead and zinc as
seen in Table 5.
Pollution levels of lead and zinc were investigated in the
lead mining environment of Ishiagu in Ivo local government
and non-lead mining community of Uburu in Ohaozara local
government area of Ebonyi state by measuring the concentrations of the metals in soil and water in the areas and also
by calculating their geoaccumulation, pollution indices and
the water/soil ratios of the heavy metals.
The observation of minimal lead concentration in the
stream water when compared to well water and borehole
water could be as a result of the deposition of the lead
down the earth crust resulting to its dissolution into the
ground water showing that the concentrations of lead in the
water bodies have the order borehole water [ well
water [ stream water (Fig. 2). The flowing of the stream
water could have contributed to the diminished lead concentration in the stream water. The observation of lower
concentration of lead in steam than in borehole or well
water is consistent with similar observation by Orisakwe
et al. 2006) who also reported a concentration lower than
the maximum contamination level (MCL) for lead. When
compared with maximum permissible limit of lead, it was
observed that the concentration of lead in borehole water in
both communities were higher than the permissible limits.
It was also observed that the concentration of lead in water
in Ishiagu where mining presently going on were higher in
the water bodies when compared to that of Uburu where
mining has been suspended for more than 20 years.

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Fig. 3 Lead concentrations in

different water bodies in both
Ishiagu and Uburu

Fig. 4 Barchart showing the

concentrations of zinc in water
bodies in both Ishiagu and
Uburu

Table 3 The result of the calculated pollution indices of lead and

zinc in Ishiagu and Uburu
Town

Pollution index
(soil) (PIsoil)

Interpretation [(PI [ 1 = polluted)

(PI \ 1 = not polluted)]

Ishiagu

0.50

Not polluted

Uburu

0.36

Not polluted

Town

Pollution index
(water) (PIwater)

Interpretation [(PI [ 1 = polluted)

(PI \ 1 = not polluted)]

Ishiagu

5.11

Polluted

Uburu

2.42

Polluted

Table 5 The calculated water/soil ratio in Ishiagu and Uburu

communities

Metal

Location

Lead

Topsoil (Ishiagu)
Subsoil (Ishiagu)
Topsoil (Uburu)

Zinc

123

Ishiagu

Uburu

WHO calculated values

Lead

0.0018

0.0014

0.0001

Zinc

0.001

0.0008

0.0001

1971). The results suggest no form of lead or zinc contamination exists in the soil of both communities. The Igeo
for lead in both communities gave zero (0) and one (1) for
zinc showing that the environment has higher contamination of zinc than lead. This observation is confirmed by the
calculated pollution indices of the metals in both communities which revealed that even though the pollution indices
were higher in Ishiagu than Uburu, both communities have
relatively pollution indices below the permissible

The calculated geoaccumulation indices for lead and

zinc in both communities, is an indicator of the levels of
pollution caused by these metals (Miller and Koeppe
Table 4 The calculated
geoaccumulation indices of lead
and zinc in the soil from Ishiagu
and Uburu (Forstner et al. 1993)

Metals

Igeo index

Igeo class

Extent of pollution

13

-0.143

Practically uncontaminated

14

-0.069

Practically uncontaminated

14

-0.069

Practically uncontaminated
Practically uncontaminated

Concentration
(lg/g)

Subsoil (Uburu)

16

Topsoil (Ishiagu)

246

1.168

Uncontaminated to moderate

Subsoil (Ishiagu)

156

0.713

Uncontaminated to moderate

Topsoil (Uburu)

156

0.713

Uncontaminated to moderate

Subsoil (Uburu)

189

0.904

Uncontaminated to moderate

Bull Environ Contam Toxicol (2010) 85:313317

threshold, suggesting non-contamination of the soil. The

pollution index ranged from practically uncontaminated to
moderately contaminated. But when the pollution index
was computed for water, it gave 5.11 for Ishiagu and 2.42
for Uburu. These values show significant pollution level in
the test area. On determining the water/soil concentration
ratio of lead and zinc, the results still show that Ishiagu has
higher level of contamination of lead than Uburu. But the
values were all above the permissible limit even though the
level of lead and zinc were found to be below permissible
limits in soil. These results could suggest that contamination could be caused by the level of the metals in water.
Plants also absorb this water, thereby increasing the level
of the metal in the plants and endangering the food chain.
The pollution of the metal in vegetable and some food
stuffs is our ongoing study.

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