Table Of ContentInt. J. Pure Appl. Sci. Technol., 12(2) (2012), pp. 66-77
International Journal of Pure and Applied Sciences and Technology
ISSN 2229 - 6107
Available online at www.ijopaasat.in
Research Paper
Impact of Mining and Agriculture on Heavy Metal Levels
in Environmental Samples in Okehi Local Government
Area of Kogi State
Matthews-Amune, Omono Christiana1, * and Kakulu, Samuel1
1 Department of Chemistry, University of Abuja, Abuja, Nigeria
* Corresponding author, e-mail: ([email protected])
(Received: 25-8-12; Accepted: 14-9-12)
Abstract: Soil, plants and river near an iron mine is polluted by tailing, mine
waste and agrochemicals in Itakpe, Okehi Local Government Area of Kogi
State, Nigeria which poses a threat to the agricultural land. In this study, heavy
metals Cd, Cu, Mg, Ni, Pb and Zn concentrations in river water, soil and crop
plants in mining site were determined using Flame Atomic Absorption
Spectroscopy. Water samples from River Pompom were digested with HNO ,
3
plants were digested with a mixture of HNO and HClO (4:1) and soil with
3 4
HF-HClO acid mixture (5:1). The results showed that heavy metals mean
4
concentration in Pompom River is 0.03±0.003,0.05±0.002,0.04±0.002,
0.01±0.001,0.01 ±0.001 and 0.04±0.002 mg/ml, in plants 0.02±0.01, 0.11±0.03,
0.04±0.01, 0.10±0.02, 0.04±0.001, 0.03±0.01 mg/g and in agricultural soils
0.16±0.02, 0.15±0.03, 0.04±0.03, 0.1±0.02, 0.07±0.01 and Zn 0.04±0.04 mg/g
for Cd, Cu, Mg, Ni, Pb and Zn respectively. Seasonal variation showed
metallic levels in water to be higher during the rainy season than dry season.
The concentration of Cu, Mg, Ni, Pb and Zn in water were within the FEPA
and WHO permissible guidelines for drinking water and concentrations of
heavy metals in the studied plants were below the FAO/WHO limit guideline
for heavy metal levels in food. The soil metallic levels were lower than the
normal soil content intervals and maximum allowable limits of heavy metals in
soils. These results could have potential impacts on the mining environment if
not monitored.
Keywords: Soil, Plants, Water, Heavy metal, Tailings.
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Introduction:
With global changes resulting in new challenges in environmental protection and conservation there is
need for baseline data to evaluate the potential impacts of pollutants to ecosystems. Activity such as
metal mining release large amount of tailing and waste containing heavy metals which pose severe
threat to water sources, agricultural soils and food crops. (Jung, 2001, 2008, Prathumratana et al.,
2008, Aremua et al., 2010, Gutiérrez-Ginés et al., 2010, Ezeh and Chukwu, 2012) Thus the demand,
for a country’s economic, agricultural and industrial development needs a monitoring program for a
safe and pure environment.
Mining no doubt impacts negatively on agriculture because of the complex catena of various
interactions that occur as waste become part of the ecosystem into which it is deposited. Mining
activities has been reported to have impacts such as oxidation of metal sulphides which induces soil
acidification, impeding natural colonization of vegetation causing soil erosion and degradation of
aquatic ecosystem leading to destruction of aquatic life. In furtherance acid mine water impacts on
agricultural lands irrigated with it.(Lin et al., 2005, Lim et al., 2008, Jung, 2001, Jian-Min et al., 2007)
Impacts such as deficiencies of essential micronutrients have been reported.(Jung, 2008, Ezeh and
Chukwu, 2012) Such effect results in the use of agrochemicals introduced as soil nutrients to improve
soil fertility. Metals present in these supplements in most cases exceed the limits set for land
application and continuous use can potentially exacerbate their accumulation in agricultural soils.
(Lim et al., 2008, Hesterberg, 1998) This results in bioaccumulation and biotransfer of harmful metals
to humans through the food chain.
There is concern about the potential harmful effects of these metals because besides affecting the
productivity of ecosystems, they could also impact on animal and human health. Furthermore there is
risk of safety for mine workers and residents in the vicinity of mining environments. Lim et al (2008)
studies reported carcinogenic risk of cancer due to As exposure from in take of soil, plant and water in
abandoned Songcheon Au-Ag mine in Korea to be 3 patients among 1000 people. Risk assessment of
studies by WHO in communities in Mitrovica, Europe exposed to Pb from mining indicated children’s
blood Pb levels to be dangerously high with soil contamination as source of exposure. (Prathumratana
et al., 2008) Effects such as reduction yield in cereals, stunted foliage and increased amounts of shoots
on plants have been reported. (Ezeh and Chukwu, 2012, Lim et al., 2008, Jian-Min et al., 2007,
Prathumratana et al., 2008)
With industrialization and agriculture increasing the presence of heavy metals in our environment,
their presence in food crops and most edibles, there is an increasing need to study heavy metal
distribution and accumulation in agricultural soils. Numerous studies on mining and its effects on soil,
plants and water have been carried out in several countries with limited studies undertaken in Nigeria.
The objective of this study is to access the impact of mining on heavy metal levels in streams, soils
and crop plants in the Itakpe iron mine in Kogi State, Nigeria vicinity and comparing result with
control site. This study will contribute to awareness of the potential impacts of pollutants and provide
a key to effective management of surface soil quality in the mining area.
Materials and Methods
The study area is Nigeria Iron Ore Mining Company, Itakpe in Okehi LGA of Kogi State in the North
Central part of Nigeria. It lies within longitude 60 16’E and latitude 70 36’N. Mining began in 1979
and Beneficiation in 1993. The mine stopped production in 2008 with mine waste left untreated. Thus,
tailings and wastes are dispersed by wind and erosion on soils, plants and water in the vicinity of the
mining site. River Pompom flows across the mining site. The climate of the area is tropical and
consists of 6 months (May to October) of rainy season (RS) and 6 months (November-April) of dry
season (DS). The inhabitants of the study area are engaged in subsistence agriculture. The DS samples
were collected in January 2010 while the RS samples were collected in July 2010. Sampling locations
are shown in Figure 1.
A total of 150 water samples (75 per season) were collected from River Pom-pom at L2
(downstream), L3 (point of entry of mining effluents) and L4 (up stream). Water samples were
collected by immersion of the container below water level. The containers were completely filled with
Int. J. Pure Appl. Sci. Technol., 12(2) (2012), 66-77. 68
water. The collected water samples were not filtered prior to analysis. 1% HNO solution was added
3
to acidify the sample to a pH of < 2 as preservative. The same treatment was given to the blank
sample. Method of USEPA (2008) of evaporating the water with concentrated HNO was used to
3
digest the water samples. The extract was analyzed using AAS. The same procedure was carried out
on the blank samples. Spiking of the sample was done using standards of metal concentration of each
studied metal and extracted as above.
A total of 120 soil samples (0-15 dept) were collected from three farm lands during both season; L6
farm in the Mine Area, L7 farm in the Beneficiation Plant Area and L8 (control) farm in Osara Dam
Area-12 kilometers from Itakpe with a stainless steel knife. The collected soil samples were air–dried
for seventy-two hours, ground in an agate mortar, passed through a 0.005 mm nylon sieve and stored
in clean acid treated polythene bags. Tessier et al (1979) method for total metal analysis was carried
out by digesting 1 g (<0.005 mm) of soil sample with a mixture of 5 ml HF and 1 ml HClO . The
4
extract was analyzed using AAS. The same procedure was carried out on soil Reference sample.
A total of 140 crop plant samples (70 per season), 10 of each species were randomly collected in the
vicinity of the farms. The crops in mining site farms were; maize (zea mays), cassava (manihot
esculentus) and yam (Dioscorea rotundata) and okro (Abelmoschus esculentus) while in control farm;
maize (zea mays), yam (Dioscorea rotundata) and cassava (manihot esculentus). Plant samples were
washed with deionized water, air dried and dried to constant weight at about 1050C in an oven.
Samples were ground into powder, passed through a 0.02 mm sieve, mixed to homogenize and stored
in acid treated polythene bags. Method of 4:1 mixture of HNO and HClO by Kakulu and Jacob
3 4
(2006) was used for plant digestion. Reagent blank was prepared in similar manner. Spiking of the
sample was done using standards of concentration of each studied metal and blank samples were
extracted as above.
Absorption Spectrophotometer (AAS) model 210VGP, Buck Scientific Incorporated USA with
instrumental parameters shown on Table 1 was used for the determination of Heavy Metals in this
work.
Quality control was implemented through three replicate samples, (performed for each water, plant
and soil samples except for precision analysis where 10 replicate samples were used for water, 7 for
plants and 6 for soil) reagent blank, spiking and use of international soil reference sample (Soil
Reference Material 989 Netherland). Precision for the determination of heavy metals in water ranged
3-16 %, in plants ranged 0.30-12 % and in soil ranged 8-12 %. Recovery studies gave 79-104 % for
water and 80-120 % for plants. Analysis of soil Reference Material 989 from Netherland gave Cu
144.5±11.6 and Pb 253.8±13.8 µg/g against the standard values of 153±3.9 and 282±3.6 µg/g for Cu
and Pb respectively.
Table 1: AAS instrumental parameters
Operating Cd Cu Mg Ni Pb Zn
parameters
Wavelength(nm) 326.1 324.7 285.2 341.5 283.3 213.9
Slit width(mm) 0.7 0.7 0.7 0.2 0.7 0.7
Lamp current(mA) 2.0 1.0 3.0 2.0 2.0
Sensitivity(mg/L) 0.75 2 0.75 7 10 0.5
Detection limit 0.01 0.005 0.005 0.1 0.08 0.005
Linear 2.0 5.00 1.5 8.0 20.00 2.50
range(mg/L)
Flame type Air-Acetylene
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Results and Discussion
The statistical summary showing the mean, range and standard deviation for the analytical parameters
for soil, crop plants and water are shown in Tables 2-5. These sites show more than one heavy metal
in the soil, water and crop plants and were generally low. The summary of metal concentrations in soil
is reported on Table 2. Total soil concentration of Cd ranged 0.12-0.18, Cu ranged 0.08-0.18, Mg
ranged 0.04-0.04, Ni 0.05-0.17, Pb ranged 0.05-0.07 and Zn ranged 0.04-0.04 µg/g. The observed
level of Ni in the mining site was up to 6 times higher than the control site while Cu metal levels were
7 times higher than the control metal level. The metal level for Mg was the same for both seasons. Zn
and Pb levels were relatively low (Zn 0.04-0.04 and Pb 0.05-0.07 µg/g). The levels observed were
lower than the normal soil content intervals, maximum allowable limits of heavy metals in soils and
below the estimated toxic levels in soils for purposes of agriculture. (Pendias and Dubka, 1992, Bero
and Reaves, 1984, Ezeh and Chukwu, 2012)
The summary of the concentration of metals in the water sample for the rainy and dry seasons are
listed in Table 3. The rainy season metal levels were higher than the dry season levels. Cd in the three
locations ranged from <0.01-0.06, Cu ranged <0.01-0.10, Mg ranged 0.03-0.04, Ni ranged <0.01-0.01,
Pb ranged 0.01-0.01 and Zn ranged 0.02-0.04 µg/ml. Except for Zn the metallic levels of the studied
metals were the same in all locations during the dry season while the levels of Ni and Pb were the
same in all locations during the rainy season. The lowest metal concentration levels were observed
during the DS for Cu, Cd and Ni (<0.01 µg/ml) while the highest level was during the RS for Cu.
Levels of Cu, Mg, Ni, Pb and Zn were within the FEPA and WHO values permissible guidelines for
drinking water.
The summary of metal concentrations in crop plants is reported on Tables 4 and 5. All the studied
metals were detected in all the crop plants. Cassava plant was the only available crop plant in both
farms during the DS. Metal levels on crops planted at the mining site were relatively higher than those
in the control site. Concentration of Cd in food crops showed maize leaves to have the highest level
(0.14 µg/g) followed by Yam (0.05 µg/g), Cu showed okro leaves to have the highest level (0.22 µg/g)
followed by cassava leaves (0.18 µg/g), Mg showed cassava leaves to have the highest level (0.03
µg/g) followed by okro (0.02 µg/g), Ni showed maize leaves to have the highest level (0.15 µg/g)
followed by cassava (0.12 µg/g), Pb showed the same level (0.05 µg/g) in all the food crops while Zn
concentration in food crops showed yam leaves to have the highest level (0.87 µg/g) followed by
cassava (0.48 µg/g). Except for Zn the metallic levels of the studied metals were the same in the
mining site farm and the control farm during the dry season. Cu and Ni levels were relatively higher
than the other studied metals in all the food crops. The observed metallic levels in plants were within
the FAO/WHO limit guideline values for heavy metal levels in food.
Soil
Soil contains various functional groups which are effective agents for heavy metal sorption. Their
interactions affects the properties and processes in the soil which are determined by the level of Fe,
Al, and Mn oxides and hydroxides, rainfall distribution, erosion, soil drainage, redox potential, texture
and organic matter and clay content. The dominant process at any specific time determines the heavy
metal retention capacity. (Jung, 2001, 2008, Hesterberg, 1998, Jian-Min et al., 2007, Ekosse, et al.,
2005) The studied metals had no specific patterns of distribution during both seasons but there were
variations in their levels in soil. This could be due to seasonal changes, topography of farm,
differences in the individual metal solubility, non-equilibrium distribution of water and microbial
mediated processes. Mining activities is reported to cause impediment of natural colonization of
vegetation in mine sites which leads to severe soil erosion. (Lin et al., 2005) However anomalies in
metallic levels could occur as a result of heavy metal deposition on soil surface from various sources
such as emissions of metal-carrying dusts, gases and smoke from industrial undertakings through
atmospheric transportation.
The range and mean concentration of the studied metals in soil are shown in Table 5. In comparison
with the mining site farm, relatively low contents of heavy metals were found in soils sampled at a
nearby control area with similar geology. This shows elevated levels of the studied metals in the
Int. J. Pure Appl. Sci. Technol., 12(2) (2012), 66-77. 70
mining site due to aerial deposition. In mining sites dust laden metals spread on every surface in the
area due to blasting of the rocks during mining with concentration on soil, water and plants depending
on distance from the mine and the form in which it is transported. (Jung, 2001, 2008, Jian-Min et al.,
2007, Ekosse, et al., 2005) The spatial variation of the contaminants in the topsoil in the mining site
indicates their dispersion through wind and erosion. According to Jung (2008) metals dispersed from
mine waste are likely retained in the lower areas used for agriculture with their mobilization in
solution at the surface favouring down slope. The low levels of Cu, Zn and Ni observed could be due
to their mobility in weathering environment while the low Pb levels could be due to its ability to
adsorb onto soil constituents surfaces. In furtherance Cd is reported to be weakly sobbed and as such
is not retained in soils. (Ezeh and Chukwu, 2012)
Mine tailing indiscriminately dumped become materials for soil formation which on weathering
releases into soils the composing metals with levels depending on the total metal concentration,
speciation, geochemical characteristics and mineralization. (Jung, 2001, Ezeh and Chukwu, 2012,
Jian-Min et al., 2007) Zhou et al 2007 reported the presence of Cu, Zn, Cd and Pb from mine tailings
that contributed levels as high as 567, 1140, 2.48 and 191 µg/g respectively to the soil. Weathering
also leads to oxidation of sulphide bearing minerals which causes acid mine drainage (AMD)
characterized by release of metals leading to high concentration of heavy metals, acidity and salinity
of soil in agricultural lands in mining sites. (Lin et al., 2005, Khan et al., 2005, Jian-Min et al., 2007)
Soil contaminated with heavy metals higher than recommended values mentioned in quality
guidelines are not suitable for agricultural purposes. Mining activities in the vicinity of the Dabaoshan
Mine in China has been reported to have polluted 83 villages, 585 x 104 m2 paddy fields and 21 x 104
m2 ponds. (Jian-Min et al., 2007)
Heavy metals introduced in soils remains even after their addition to soils have been stopped due to
persistence and non degradability. (Hesterberg, 1998, Gutiérrez-Ginés et al., 2010, Ezeh and Chukwu,
2012) Elevated metal concentrations can cause negative effects on soil such as reduction of soil
microbial biomass levels which are responsible for maintenance of soil fertility for optimum crop
yield, affecting nitrogen-fixation and reduction in certain enzyme activities. (Hesterberg, 1998, Jung,
2008) Cd in soil is reported to cause transformations in microorganisms. (Sinha et al., 2010) These
contaminated soils can influence the metal uptake by plants grown on the soil. The Cu metal levels
observed to be 7 times higher than the control metal level indicate potential Cu toxicity. Cu is
reported to have synergistic effects with other soil contaminants. This result in Cu been bound and
made unavailable to plants through formation of complexes. Such effects have negativeimpact on
growth, biochemical and physiological activities of plants leading to poor yield. (Sharma, 2010, Zhou
et al., 2007, Sinha et al., 2010)
Table 2: Summary of heavy metals in soil (µg/g dry weight)
Metal Dry season Rainy season Mean Conc.
Mining Site Control Mining Site Control
Cd 0.14 ± 0.01 0.07±0.01 0.18±0.02 0.10±0.01 0.16±0.02
(0.17-0.18)a (0.06-0.08) a (0.12-0.15) a (0.09-0.11)a (0.14-0.18)a
Cu 0.16±0.03 0.05±0.02 0.13±0.03 0.07±0.01 0.15±0.03
(0.08-0.18) a (0.03-0.07) a (0.14-0.17) a (0.06-0.08)a (0.12-0.18)a
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Mg 0.04±0.002 0.04±0.002 0.04±0.002 0.03±0.003 0.04±0.03
(0.04-0.04) a (0.038-0.042) a (0.04-0.04) a (0.027-0.033)a (0.01-0.05)a
Ni 0.07±0.01 0.09±0.004 0.15±0.03 0.01±0.01 0.1±0.02
(0.05-0.09) a (0.086-0.094) a (0.13-0.17) a (0.00-0.02)a (0.08-0.12)a
Pb 0.06±0.02 0.06±0.001 0.07±0.004 0.02±0.001 0.07±0.01
(0.05-0.07) a (0.059-0.061) a (0.06-0.07) a (0.017-0.021)a (0.06-0.08)a
Zn 0.04±0.05 0.05±0.001 0.04±0.03 0.03±0.01 0.04±0.04
(0.04-0.04) a (0.049-0.051) a (0.03-0.04) a (0.02-04)a (0.00-0.08)a
a=range
Water
Studies conducted on heavy metals in natural waters in the aquatic environment reports that they have
low solubility. Their dispersion patterns depends on the solubility and mobility of each metal and
factors such as surface runoff, groundwater, dissolution from sediment and deposition from the
atmosphere affect metallic levels. (Jung, 2001, 2008, Jian-Min et al., 2007) The metallic levels of the
studied metals were relatively low in water. The low metallic levels observed could be due to the low
level of contaminants entering the river Pompom as a result of the stoppage of mining which has
resulted in low activities in the mining environment.
The higher metallic levels observed during the RS could be due to the introduction of heavy metals
from tailings, indiscriminate use of metal containing fertilizers and pesticides in agriculture, discharge
of industrial effluents, and the mineral composition of the river bed. The interaction of rain with mine
tailings could result in the decrease of the pH of the soil and increase in the acidity of the Pompom
river making more metals available. Jung (2001) reported the presence of Cd, Cu, Pb and Zn µg/g in
tailings from Au-Ag mine, Korea which resulted in lowering water in the mine site to a pH of 2.2 and
Lin et al 2005 reported the degradation of aquatic ecosystem with mine water continually flowing to
tributaries of other rivers. Effluents from Neyevli Lignite mine in India contaminated with various
metals to concentrations of 2–1,200 times higher than concentration in World rivers is used by nearby
villagers for irrigation. (Khan et al., 2005)
Contaminants in aquatic environment adversely affect many species of aquatic plants and fisheries
thereby acting as threat to the functioning of aquatic ecosystems. Elevated levels of heavy metals in
marine ecosystem can result in deleterious effect on organisms and consumers and sometimes their
death. AMD resulting from mining activities in Southern China degraded aquatic ecosystem with
mine water of pH < 3.5 which destroyed all the aquatic life to a distance of 25km downstream of the
discharge point with only one species found in contrast to a reference point where 36
microinvertebrates were found. (Lin et al., 2005)
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Table 3: Summary of metal concentrations (m g/ml) in the water
Metal Mean±SD Range
Cd 0.03±0.003 0.027-0.033
Cu 0.05±0.001 0.049-0.051
Mg 0.04±0.002 0.038-0.042
Ni 0.01±0.001 0.009-0.011
Pb 0.01±0.001 0.009-0.011
Zn 0.04±0.002 0.038-0.042
Plants
The relatively high concentrations of all the studied metals in the crop plants planted in the mining
site compared with the ones in control is an indication of presence of heavy metal pollution due to the
mining activities. Heavy metals detected in the aerial portions of plants pose a serious health risk for
herbivores. (Gutiérrez-Ginés et al., 2010) Plants can take up metals from air, water, soil and sediments
with variations in metal content dependent on several factors such as soil properties, seasonal
changes, plant species, plant age, time interval of metallic soil input, nutrient availability and
interaction among the metals. The total metal concentrations in soils and soil pH controll their intake.
(Jung, 2008, Jung and Thornton, 1997, Lee et al., 2001, Zhou et al., 2007, Ekosse, et al., 2005) The
result in the study shows that the levels of most of the metals were highly comparable with the soil
metal levels. The possible reasons for metal level variation in plant crops are; continuous atmospheric
deposition, direct deposition on plant leaves from agrochemicals, rate of metallic deposition, use of
contaminated water for irrigation, differences in physical and chemical characteristics of soil,
topography of farm and plant species. In furtherance evaporation process remove water from soil,
causing increase in metal concentration in the roots and leaves. Acid mine water used in irrigation was
reported responsible for the extremely high concentration of some heavy metals present in edible
portions of a variety of food crops planted in agricultural lands in the mine site of China. (Lin et al.,
2005)
The Cd in maize (0.14 µg/g) was higher than Cd in soil (0.07 µg/g) during the RS in the control farm.
High levels of Cd in plants results in increase in predisposition to fungal invasion and sometimes
rapid plant death. (Sinha et al., 2010) There was high level of Zn concentration in cassava (0.48 µg/g)
and yam (0.87 µg/g) in the control farm. Zn is an essential metal needed for growth. (Ezeh and
Chukwu, 2012) The higher metallic level observed in plant than soil indicate the possibility of impute
through the use of agrochemicals in the farming process. Pasquini (2006) reported metallic levels of
20 to 40 times higher than the WHO/FAO maximum recommended level and Cd content of one of the
vegetables 10 times higher than the WHO/FAO recommended limit with soil metallic levels within
normal levels. Heavy metals in plants have negative effects such as the reduction rate in
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photosynthesis, water uptake poor germination of seeds, decrease in plant height and number of
leaves, quick aging of plant, decreases in their budding, poor yield and quality of crops in growth rate
and nutrient uptake. (Singh and Agrawal, 2011, Borah and Devi, 2010, Sinha et al., 2010) Other
negative effects of heavy metals on plants are; Ni inhibits root growth, Cr decreases growth and
chlorophyll content, and Pb causes chlorosis, necrosis, stunt growth of root/shoot, and less biomass
production. Sinha et al (2010) reported the accumulation of Cr on the seeds of a plant to a level of
3.15 mg in a Cr contaminated soil.
There were significant differences (p<0.05) shown in Cu, Zn and Ni in the crops. The significant
difference (p<0.05) in Cu could be due to the relatively high Cu level in the soil which correlated with
the level in the plants. Report is given of the presence of metals in roots but non in the above-ground
parts of the plants. (Gutiérrez-Ginés et al., 2010) The significant difference (p<0.05) in Cu, Zn and Ni
could be as a result of their need as essential elements and as components of pesticides. (Borah and
Devi, 2010, Ezeh and Chukwu, 2012, Jung, 2008, Aremua et al., 2010)
Table 4: Concentration of heavy metals in crop plants in the rainy and dry season (µg/g dry weight)
Rainy Season Dry Season
Cassava Maize Yam Okro Cassava
Cd
Mining site 0.01±0.01 0.01±0.002 0.03±0.01 0.03±0.002 0.03±0.002
(0.00-0.02)a (0.008-0.012)a (0.02-0.04)a (0.018-0.032)a (0.028-0.032) a
Control 0.02±0.01 0.14±0.01 0.05±0.004 0.03±0.002
(0.01-0.03)a (0.13-0.15)a (0.046-0.054)a 0.028-0.032) a
Cu
Mining site 0.18±0.16 0.09±0.002 0.15±0.01 0.22±0.03 0.01±0.002
(0.02-0.34)a (0.088-0.092)a (0.14-0.0.16)a (0.019-0.25)a (0.018-0.012) a
Control 0.11±0.01 0.08±0.01 0.14±0.01 0.01±0.002
(0.10-0.12)a (0.07-0.09)a (0.13-0.15)a (0.018-0.012) a
Mg
Mining site 0.03±0.001 0.01±0.01 0.01±0.002 0.02±0.01 0.1±0.02
(0.029-0.031)a (0.00-0.02)a (0.008-0.012)a (0.01-0.03)a (0.08-0.12) a
Control 0.02±0.002 0.02±0.004 0.03±0.001 0.1±0.01
(0.018-0.022)a (0.016-0.024)a (0.027-0.031)a (0.09-0.11) a
Ni
Mining site 0.12±0.01 0.15±0.01 0.11±0.01 0.09±0.01 0.01±0.004
(0.11-0.13)a (0.14-0.16)a (0.10-0.12)a (0.08-0.10)a (0.006-0.014) a
Control 0.06±0.01 0.05±0.001 0.08±0.01 0.01±0.004
(0.05-0.07)a (0.049-0.051)a (0.07-0.09)a (0.006-0.014) a
Pb
Mining site 0.05±0.001 0.05±0.02 0.05±0.02 0.05±0.01 0.01±0.002
(0.049-0.051)a (0.03-0.07)a (0.03-0.07)a (0.04-0.06)a (0.008-0.012) a
Control 0.07±0.02 0.06±0.02 0.06±0.01 0.01±0.003
(0.05-0.09a (0.04-0.08)a (0.05-0.07)a (0.007-0.013) a
Zn
Mining site 0.02±0.01 0.02±0.004 0.03±0.01 0.05±0.01 0.04±0.01
(0.01-0.03)a (0.016-0.024)a (0.02-0.04)a (0.04-0.06)a (0.03-0.05) a
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Control 0.48±0.14 0.01±0.01 0.87±0.57 0.02±0.01
(0.34-0.64)a (0.00-0.02)a (0.30-1.44)a (0.01-0.03) a
a range
=
Table 5: Summary of heavy metal levels in crop plants (m g/g)
Plants Control
Metal Mean±SD Range Mean±SD Range
Cd 0.02±0.005 0.015-0.025 0.06±0.01 0.05-0.07
Cu 0.11±0.03 0.08-0.14 0.08±0.01 0.07-0.09
Mg 0.04±0.01 0.03-0.05 0.04±0.004 0.036-0.044
Ni 0.10±0.02 0.08-0.12 0.08±0.01 0.07-0.09
Pb 0.04±0.001 0.039-0.041 0.05±0.02 0.03-0.07
Zn 0.03±0.01 0.02-0.04 0.35±0.18 0.17-0.53
Conclusion
The results show that the soil in the Itakpe mining site farm is not polluted but with gradual buildup
they could become polluted. The levels observed were lower than the normal soil content intervals,
maximum allowable limits of heavy metals in soils and below the estimated toxic levels in soils for
purposes of agriculture. Seasonal variation showed metallic levels in water to be higher during the
rainy season than dry season. The concentration of Cu, Mg, Ni, Pb and Zn in water were within the
FEPA and WHO permissible guidelines for drinking water. The heavy metal concentration of crops
grown on control farm showed relatively lower concentration than those in the Itakpe mining site
farm. All the observed concentrations of heavy metals in the studied plants were within the
FAO/WHO limit guideline for heavy metal levels in food. The observations in the present study
demand for careful monitoring of the environment especially when mining resumes due to potential
environmental risk. Through monitoring database can be developed which gives a variety of useful
information and methodology towards achieving the ultimate goal of providing safe and quality food.
Int. J. Pure Appl. Sci. Technol., 12(2) (2012), 66-77. 75
Figure 1:
N
Itakpe
Map of Nigeria showing
Kogi State
Dam L8
L8
L2 R. Pompom
L4
L3
L2
L3 L6 R. PLo7m pom
L4
L7L6
Mining site
LEGEND
Sampling Points
Beneficiating Plant
Mine
River
Osara Dam
Figure 1: Map of Itakpe Mining Environment Showing Sampling Areas
Description:Abstract: Soil, plants and river near an iron mine is polluted by tailing, mine waste and agrochemicals in Itakpe, Okehi Local Government Area of Kogi.
