Geochemical Survey, Health and Environmental Implication of Trace Elements in Soil Samples from Owo Area, Ondo State, Southwest Nigeria

Geochemical Survey, Health and Environmental Implication of Trace Elements in Soil Samples from Owo Area, Ondo State, Southwest Nigeria
IJGM
Geochemical Survey, Health and Environmental Implication
of Trace Elements in Soil Samples from Owo Area, Ondo
State, Southwest Nigeria
*1Jayeola, A.O., 2Odundun, O.A.
1,2
Department of Earth Sciences, Adekunle Ajasin University, Akungba Akoko, Ondo State, Nigeria
This study involves the geochemical assessment of trace elements of surface soil samples from
Owo area in Ondo State, Nigeria. In environmental studies, chemical elements are often
distinguished as lithogenic and anthropogenic based on their sources. The knowledge about their
distribution in soils is thus crucial for the assessment of the environmental hazards due to
chemical pollution of urban soils. In this area, fourteen (14) soil samples were collected and
analyzed for the following trace elements – Zinc(Zn), Copper(Cu), Lead(Pb), Arsenic(As),
Cadmium(Cd), Titanium(Ti), Strontium(Sr), Zircon(Zr), Molybdenum(Mo), Silver(Ag), Rubidium
(Rb), and Tin(Sn) using Atomic Absorption Spectrophotometry (AAS). The background values as
determined were as follows: Zn(8.30-8.70ppm), Cu(1.95-2.19ppm), Pb(0.83-0.87ppm) As(0.052-
0.054ppm), Cd(0.06-0.07ppm), Ti(0.12-0.14ppm), Sr(0.04-0.05ppm), Zr(0.04-0.05ppm), Mo(0.13-
0.14ppm), Ag(0.12 0.13ppm), Rb(0.013-0.014ppm) and Sn(0.07-0.08ppm).The threshold values in
(ppm) were: 9.12, 2.69, 0.93, 0.06, 0.07, 0.20, 0.05, 0.06, 0.20, 0.26, 0.02, and 0.11. The increase
above the background concentrations is probably anthropogenic. The Anthropogenic Factor (AF)
and Geoaccumulation Index (Igeo) were determined for Zn, Pb, Cu and As in order to quantify the
level of contamination in the soils. The result revealed an average AF of 1.1 and Igeo of -0.44, 1.00,
-1.05 and -0.37. This result indicates uncontaminated to slightly contaminated soil condition. The
pH values of the soils, ranging from (5.5-7.7) indicate a slightly acidic to slightly alkaline soils
owing to the chemical reactions of the anthropogenic additives. Anthropogenic inputs from the
few industries in the area were quite minimal, except for municipal and vehicular contributions.
Therefore, monitoring programs should be introduced to check the level of environmental
degradation that may result from future anthropogenic perturbations.
Key words: Geoaccumulation Index, Trace Element, Lithogenic, Degradation
INTRODUCTION
Soil survey is widely used in exploration geochemistry, and
very successful results have been achieved, especially
with surveys conducted in residual soils. Anomalous
concentration of metals in soils may come from the
bedrock itself and in some cases through natural transport,
but are more often due to anthropogenic input from solid
or liquid waste deposits, agricultural inputs, fallout of
industrial and urban emissions. The diagnosis of soil
contamination by potentially harmful metals has been the
subject of public interest since the 1970s countless studies
have been reported by many researchers, (Young, 1996,
Alloway and Ayres 1997). This is due to the environmental
and health problems caused by high metal contents in soils
which can affect microorganisms, plants, animals and
human beings through contaminated water and crops.
*Corresponding Author: Jayeola, A.O., Department of
Earth Sciences, Adekunle Ajasin University, Akungba
Akoko, Ondo State, Nigeria. E-mail:
jaffero2001@yahoo.com
International Journal Geology and Mining
Vol. 4(2), pp. 202-210, August, 2018. © www.premierpublishers.org. ISSN: 3019-8261
Research Article

Jayeola and Odundun 203
Geochemical surveys of urban soils have already been
carried out in many urban areas such as Osnabruck
(Bloemen, 1995), Greater London area (Kelly, 1996),
Aberdeen (Paterson, 1996), Salamanca and Valladolid
(Sanchez-Martin, 2000), and Gibraltar (Mesilio, 2003).
These studies focused on heavy metals and present
typical patterns of pollution of the most upper soil layers of
the cities. Metallic species and other contaminants in soils
and water caused by the degradation of solid wastes have
also been studied (Banar, 2005, Chen, 2005, Shukurov,
2005, Piantone, 2004).
Stefan, (2006) have also studied the mineralogical and
geochemical patterns of urban surface soils in Pforzheim,
Germany. This study revealed that surface soils around
the study area have considerable amount of trace
elements reflecting the sources to the mineral and
chemical composition of the parent rocks.
STUDY AREA AND GEOLOGIC SETTING
The study area, Owo, is located in the Northeastern part
of Ondo State, southwestern Nigeria (Fig 1). It lies
between Longitude 7°10' E and 7°14' E and Latitude 5°32'
N and 5°38' N. It covers an area of about 84.4km2. The
climate is tropical, with two distinct seasons: the dry and
the rainy seasons. The area has an average rainfall of
about 1500mm. The temperature varies from 210 C to 290C
throughout the year, with an average value of 250C. The
relief of the study area varies.
Gneiss and Migmatite
Metasediments(undefined)
Older granite
Quartzite
Coal, sandstone,shale and limestone
Sandstone
Clays and shales
Sands and clays
Alluvium
Fig. 1: Map of Ondo State showing the study area.
The geology of the study area depicts an environment
characterized by flat-lying topography while the central
portion is dominated by ridges of porphyritic schist, trending
northwest-southwest. Study shows that the study area
consists of three major rock types namely; variably
migmatized, undifferentiated biotite - biotite hornblend
gneiss (Migmatized gneiss); that occupies both the northern
as well as the south-western part of the area; the politic
schist and Quartzite which underlain the southeastern
portion of the area. The geology of the study area depicts an
environment characterized by flat-lying topography while the
central portion is dominated by ridges of porphyritic schist,
trending northwest-southwest. Study shows that the study
area consists of three major rock types namely; variably
migmatized, undifferentiated biotite - biotite hornblend
gneiss (Migmatized gneiss); that occupies both the northern
as well as the south-western part of the area; the politic
schist and Quartzite which underlain the southeastern
portion of the area (Fig 2).
Fig. 2: Geological map of the study area showing the
sampling points
MATERIALS AND METHODS
Soil samples were collected from fourteen locations
distributed across study area and were all analysed.
Caution was taken by walking some meters away from the
road into the bush before samples were collected to avoid
metal contaminated areas by the traffic activities. Soil
samples were obtained at the depth of10-15cm using a soil
core sampler from sites covered by herbaceous vegetation
and grasses which were not shaded by trees or buildings
2
4
9
10
11
172022
24 25
26
27
28
30
Legend
Quartzite
Pelitic schist
Variably migmatized gneiss
0 1000 2000 3000
Isuada
Alaaye
Ilale
M

Int. J. Geol. Min. 204
where minimal disturbances from atmospheric particles
would have been guaranteed. Samples were stored in non
- metallic containers to prevent contamination and were
labeled accordingly. These were later taken to the
laboratory for the analysis of the trace metals. In the
laboratory, the samples were dried at 400C and
disaggregated in a ceramic mortal before sieving to
separate fractions larger and smaller than 2mm for further
analyzes.
In a platinum crucible of 57ml volume, 0.5g of samples was
weighed. Three milligrams (3ml) of distilled water was
added to wet the samples followed by 10-15 Hydrofluoric
acid (HF) (40%) and 2ml concentrated H2SO4. The
platinum crucible content was then left for 30minutes. After
this, HF was vaporized on a sand bath until the SO3
escaped. Five minutes after, the appearance of the SO3
cloud, the sample was removed from the sand bath and
allowed to cool. After cooling, the crucible with its content
was filled to half with distilled water and warmed on an air
bath. The dissolved substance was then transferred to a
100ml plastic bottle and filled to the mark. The digested
soil samples were then pumped into Automatic Bulk
Scientific Atomic Absorption Spectrophotometer, model
200 to determine the concentrations of the metals. The pH
test was carried out for all the fourteen soil samples. About
50g of each sample was weighed and added to 10ml of
distilled water in a beaker. A pH meter was inserted into
each of the soil mixture and the pH values were
determined and recorded accordingly.
Statistical Data Analysis
For assessment of the heavy metal concentrations in this
area, some statistical methods were used to describe the
concentration trend to allow for easy comparison between
the parameters. These include:(1) graphical discrimination
of the numerous background values from the smaller
proportion of anomalous values on a histogram of the data;
(ii) cumulative frequency curves that help determine the
background and anomalous populations from the 50th and
95th percentile respectively; (iii) recognition of clusters of
anomalous samples on concentration maps and (iv) metal
ratio and Index of Geoaccumulation (Igeo).
RESULTS PRESENTATION AND DISCUSSIONS
The concentrations of heavy metals in the soil samples
and the summary statistics of the twelve single
parameters are shown in (Tables 1 and 2).
From the histograms and the cumulative frequency curves
(Figures 3-13), the background population for zinc is (8.3-
8.7) ppm. The threshold value is equal to 9.12ppm. Copper
has its background values within the range of (1.95-2.19)
ppm and a threshold value of 2.69ppm. The background
and threshold values of other metals are shown in (Table
3).
The concentration maps (Figures 14-17) reveal at a glance
the concentrations of each metal at each sample location.
Zinc, Copper and Lead concentrations in the study area
are highest in the following locations (SAT 04, 20, 27 and
28). This stripe of high concentrations trending from the
north-east to the south-west is linked most probably to
automobile emissions, tyre wears, volcanic activities,
asphalt, leaded gasoline, e.t.c.as these areas are fairly
densely developed and characterized by traffic artery. Tire
and break abrasion spills from lubricants, corrosion and
automobile exhaust are sources of Pb, Zn, and Cu
(Muschak, 1989; Puchelt, 1992). Lead was an indicator of
traffic emissions in former times since Pb was added to
fuel as antiknock. Because of its low mobility, Pb is still
enriched in soils polluted by traffic emissions, but does not
presently accumulate at the same rate prior to the
introduction of unleaded fuel. Silver concentration is
highest in some locations as these concentrations could
have resulted from contributions from dump sites,
galvanizing, plating and corrosion of Sn coatings.
Arsenic, which often are associated with these pollutants
(Bloemen, et al., 1995) are more related to the mineral
composition of the surface soils than to the diffuse pollution
of inner urban surface soil of Owo.

Shown below are concentration maps for selected heavy metals for the study area.
Fig 14: Concentration map for Zinc Fig 15: Concentration map for Copper
Fig 16: Concentration map for Lead Fig 17: Concentration map for Arsenic
The distribution of heavy metals within the study area was
probably as a result of anthropogenic inputs and
perturbations as the polluted samples fell within the urban
centers which were characterized by dump sites,
automobile emissions, as well as disposal of solid and
liquid wastes that can easily contaminate the environment.
The mean range of pH values of the soils (5.5-7.7)
indicated a slightly acidic to slightly alkaline soils owing to
the chemical reactions of anthropogenic additives.
The impact of anthropogenic activities on the chemical
composition of surface soils of the area of Owo can be
demonstrated exemplarily by means of Pb, Zn, Cu, Cd and
As abundances. According to Siegel (1974), the regulatory
guidelines for Pb, Zn, Cu, Cd and As are: 10ppm, 50ppm,
20ppm, 0.06ppm and 6ppm respectively. In comparison,
the geometric mean values obtained for these metals in
this study [Pb (0.844ppm), Zn (7.738ppm), Cu (2.123ppm),
Cd (0.063ppm), and As (0.051ppm)] agreed with this
standard values except for Cadmium which exceeded the
boundary value of 0.06ppm.
In order to assess the level of heavy metal contamination
within the area, the indices used included metal ratio or
anthropogenic factor (AF) and index of geoaccumulation
(Igeo). The estimated values of anthropogenic factor (AF)
for the heavy metals were: 1.10, 1.11, 1.39 and 1.14 for
Zn, Pb, Cu and As respectively. The anthropogenic
enrichment followed this decreasing order Cu>As>Pb>Zn.
Soils in this environment had low enrichment factors and
thus less contaminated.
The Geoaccumulation index (Igeo) calculated gave
average values of - 0.44, 1.0, -1.05, - 0.37 for Zn, Pb, Cu
and As respectively. According to Muller (1979), values
less than zero for Zn, Cu, and As indicates no
contamination in the soil and value > 1 (for Pb) indicates
uncontaminated to slightly contaminated soil. Therefore,
the potential primary inputs of heavy metals above the
geogenic background values in the study area may be
summarized as to include liquid sewage, domestic solid
wastes, automobile emissions and associated vehicular
repair products such as oil, grease, tyre wears and so on.
6
6.2
6.4
6.6
6.8
7
7.2
7.4
7.6
7.8
8
8.2
8.4
8.6
8.8
9
9.2
9.4
2
4
9
10
11
172022
24 25
26
27
28
30
Legend
Zn(ppm)
0 1000 2000 3000 4000 m
Isuada
Ikare road
Alaaye
Ago Asara
Iyere
Ipele roadIlale
Ojana road
Rufus Giwa
Owo
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3
3.1
2
4
9
10
11
172022
24 25
26
27
28
30
Legend
Cu(ppm)
0 1000 2000 3000 4000 m
Isuada
Ikare road
Alaaye
Ago Asara
Iyere
Ipele roadIlale
Ojana road
Rufus Giwa
Owo
0.71
0.72
0.73
0.74
0.75
0.76
0.77
0.78
0.79
0.8
0.81
0.82
0.83
0.84
0.85
0.86
0.87
0.88
0.89
0.9
0.91
0.92
0.93
0.94
0.95
0.96
Legend
Pb(ppm)
0 1000 2000 3000 4000m
2
4
9
10
11
172022
24 25
26
27
28
30
Isuada
Ikare road
Alaaye
Ago Asara
Iyere
Ipele roadIlale
Ojana road
Rufus Giwa
Owo
0.036
0.037
0.038
0.039
0.04
0.041
0.042
0.043
0.044
0.045
0.046
0.047
0.048
0.049
0.05
0.051
0.052
0.053
0.054
0.055
0.056
0.057
0.058
0.059
0.06
0.061
2
4
9
10
11
172022
24 25
26
27
28
30
Legend
As(ppm)
0 1000 2000 3000 4000 M
Isuada
Ikare road
Alaaye
Ago Asara
Iyere
Ipele roadIlale
Ojana road
Rufus Giwa
Owo

Health and Environmental Impacts (Medical Geology)
Accumulation of heavy metals in soils may pose a threat
to the lives of humans and animals. Most elements
accumulate and bio-magnify in human bodies via
consumption of heavy metals contaminated food and
water as well as during gaseous exchange. According to
ICRCL (1987), soils with values of As (>40ppm), Cd
(>15ppm), and Pb (>2000ppm) higher than the tentative
threshold trigger concentrations cannot be used for
domestic gardens, allotments, parks, playing fields and
open spaces, due to that fact that these contaminants are
toxic to health. Nickel (>70ppm) and Zn (>300ppm) do not
normally pose health risks to humans, but are plytotoxic
and soils with higher values than the tentative threshold
trigger concentrations should not be used for plant growth.
The Xstrar Mount Isa Mines lease (XMIM) for example is
Australia’s leading emitter of numerous contaminants to
study that showed 11.3% of local children (12-60) months
having blood contaminations due to Pb levels >10µg/dL.(
Urban dusts (grain size <200µm) often harbor metallic-rich
contaminants and are potentially very hazardous as they
can be easily inhaled and/ or ingested. The effect of
exposure and subsequent elevated Pb levels can cause a
range of serious health, social and intellectual problems
including impaired intellectual development, behavioral
problems, attention deficit as well as and disorder and
other associated neurobehavioral effects. (Mushak et al.,
1989; Lanphear et al., 2000; Braun et al., 2006).
Although it is not possible to quantify the hazards and
deleterious effects associated with trace elements in
common use, some elements clearly present more serious
problems than others. Examples of these among the
metals analyzed are: Arsenic, Lead and Cadmium. The
main health problem associated with chronic lead
poisoning is neurological impairment in children (including
possible permanent damage if exposed to high level at an
early age), hypertension and infertility in adults (Selinus,
2004). It also causes loss of appetite, weakness, anaemia
and renal dysfunction.
ACKNOWLEDGEMENT
I acknowledge the technical advice of Dr. Omoboriowo of
the Department of Geology, Federal University of
Petroleum Resources, Warri in the course of the research.
Also all members of staff of the Geochemistry and Geology
Laboratory of the Federal University of Technology, Akure
are highly appreciated for the success of this research. I
also acknowledge the contribution of the anonymous
reviewers of Premier Publishers who took their time to
scrutinize the contents of this research article through
thorough editing which is highly professional thus
enhancing the quality of this research.
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Accepted 9 July 2018
Citation: Jayeola, A.O., Odundun, O.A. (2018).
Geochemical Survey, Health and Environmental
Implication of Trace Elements in Soil Samples from Owo
Area, Ondo State, Southwest Nigeria. International
Journal Geology and Mining 4(2): 202-210.
Copyright: © 2018 Jayeola and Odundun. This is an
open-access article distributed under the terms of the
Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any
medium, provided the original author and source are cited.

Geochemical Survey, Health and Environmental Implication of Trace Elements in Soil Samples from Owo Area, Ondo State, Southwest Nigeria

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