International Research Journal of Biotechnology (ISSN: 2141-5153) Vol. 2(9) pp. 198-212, December, 2011
Available online http://www.interesjournals.org/IRJOB
Copyright © 2011 International Research Journals
Full Length Research Paper
Seasonal and depth effects on the physico-chemical
parameters of the soils of farm settlements with
bitumen deposit
Fagbote, Emmanuel Olubunmi* and Olanipekun, Edward Olorunsola
Department of ChemistryUniversity of Ado-Ekiti, Ado-Ekiti, Nigeria.
Accepted 03 January, 2011
Soils of Agbabu and Temidire villages in western Nigeria were analyzed for pH, Total Organic Carbon,
Total Nitrogen, Available Phosphorous, K+, Na+, Ca2+, Mg2+, Mn2+, Cation Exchange Capacity and soil
texture using standard analytical procedures in the dry season (March) and rainy season (August) of
year 2008. pH in both seasons ranged between 3.99 and 6.70. Most of the stations had values that were
lower than the recommended range of 6.0 to 7.5. Magnesium ion values ranged from 1.15±0.06cmol/kg to
8.04±0.02cmol/kg. Most of the stations had values that were above 0.5cmol/kg to 1.5cmol/kg
recommended. Coefficient of variation by the general linearized model of statistical analytical system
and Duncan multiple range grouping at α = 0.05, show that sources of the parameters varied from one
2+
location to another apart from Mn that had a common source which was bitumen. Most of the
parameters had higher values in the topsoil than bottom soil. The means of values of the parameters
were higher in the rainy season than in the dry season and most of the means of the parameters show
significant differences indicating that rains had effects on the concentrations of these parameters in soil.
Keywords: Soil, characterization, parameters, bitumen, general linearized model, Duncan multiple range
grouping
INTRODUCTION
Soil quality can be defined by the interactions of a
particular soil’s measurable chemical, physical, and
microbiological properties (Baldwin, 2006). Soils vary
naturally in their capacity to function; therefore, quality of
soil can be inherent or dynamic. Inherent quality of soil is
determined by the innate properties of soil such as
texture, mineralogy, etc. These properties are determined
by the factors of soil formation such as climate,
topography, vegetation, parent material, and time.
Dynamic quality of soils is defined as the changing nature
of soil properties from human use and management. For
example, use of cover crops increase organic matter and
can have a positive effect on soil quality (Soil Quality
*Corresponding author
+2347035483300
E-mail:
bunmifag@yahoo.comTel.:
Institute, 2001). Assessment of soil quality is the basis for
assessing sustainable soil management (Chen, 1999).
Basic soil properties or indicators for screening soil
quality and health are physical, chemical and biological
indicators. Physical indicators are soil texture, depth of
soils, topsoil or rooting, infiltration, soil bulk density, and
water holding capacity. Chemical indicators are soil
organic matter or organic carbon and nitrogen, soil pH,
electric conductivity, and extractable N, P, and K.
Biological indicators are microbial carbon and nitrogen,
potential mineral nitrogen (anaerobic incubation), soil
respiration, water content, and soil temperature (Doran
and Parkin, 1994). The utility of each variable is
determined by several factors, including whether changes
which can be measured over time, sensitivity of the data
to the changes being monitored, relevance of information
to the local situation, and statistical techniques which
can be employed for processing information.
Olubunmi and Olorunsola 199
Figure 1. Map of Nigeria showing Agbabu sampling points in Ondo State
Quality of soils should be ascertained in order to
understand the limits that can be set to its use and
treatment. This also helps to minimize soil degradation
and to adopt management techniques that contribute to
the maintenance or recovery of soil fertility (Chaudhuri et
al., 2009).
Bitumen was discovered in Nigeria in 1907 (Adewole,
2010). It occurs in the south-western part of Nigeria
covering Ondo, Ogun, Edo and part of Lagos. Between
1907 and 1970, close to 40 wells, boreholes and
exploration wells had been drilled within the area of
surface occurrence. One of the wells, NBC-7 located at
Agbabu village remains open to the surface and
periodically flow heavy oil. The net thickness of the
sections range between 4m and 32m with relatively thin
overburden sections and consequently good ‘stripping
potential’. Large strip out of bitumen was observed at
Temidire village in Ondo State (Figure 1).
Agbabu and Temidire are farm settlements in Ondo
state in the western area of Nigeria. These villages are
about 210 kilometers to Lagos in the south-western part
of Nigeria. Agbabu is a village of about 400 inhabitants in
the coordinates of E004o48-49′ and N06o34-36′. Temidire
is a smaller village of about 200 people located in the
o
o
coordinates E004 49-50′ and N06 36-37′, about 2
kilometers to Agbabu. Farmers at Agbabu and Temidire
deal mainly in cash crops such as cocoa and colanut and
food crops such as yam and plantain and fishing along
Oluwa River which flows through the whole land.
Temperature remains moderate throughout the year in
the area with the minimum around 24oC and the
maximum around 33oC. The two distinct seasons in the
year are wet and dry. The wet season is at its peak from
July to the middle of September while the dry season is
from January to March.
Seasonal and depth effect on some parameters of a
forest soil has been reported (Toni et al., 2009). They
2+
2+
observed that the concentration of Ca , Mg and pH
decreased with increase in depth. The concentrations of
Ca2+, Mg2+ and organic matter were affected by dry/wet
season.
Igwe et al. (2005) studied the mineral and elemental
distribution in soils formed on the river Niger floodplain,
eastern Nigeria and reported a decrease in organic
matter with an increase in depth.
Investigation of the hydrocarbon and toxic metal
200 Int. Res. J. Biotechnol.
contents of the bitumen-impacted soil, sediment and
water samples within the Ogun block aspect of the
Nigerian bitumen belt has been carried out (Adewole,
2010). Multi-elemental analysis of Nigerian bitumen and
the physical constants characterization of its hydrocarbon
content have been carried out (Adebiyi et al., 2006).
Twelve elements – K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn,
As and Pb were detected.
A combination of factors has prevented the exploitation
of bitumen in Nigeria to date; the most important is the
environmental effects that may pose threat to both
physical and biological components in the area of
occurrence (Akinmosin et al., 2009). In developing
countries like Nigeria, industrial growth and its associated
environmental degradation is fast increasing (Ekwozor
and Agbozu, 2001; Fakayode and Onianwa, 2002;
Nesrullah et al., 2006; Wakawa et al., 2008). It is
therefore, imperative to know the pre-exploitation status
of pollution in soil, sediment, ground water, surface water
and plant in the environment. This will make assessment
of the contribution of anthropogenic activities to
environmental contamination that may be associated with
mining project when it eventually takes off easy and
effective. No report has been made on the
characterization of soils in the bitumen deposit
environment, therefore, this research was based on the
changes of soil parameters (pH, Total Organic Carbon –
TOC, Total Nitrogen – TN, Available Phosphorous - Av.P,
Potassium ion, Sodium ion, Calcium ion, Magnesium ion,
Manganese ion, Cation Exchange Capacity – CEC and
soil textural analysis) with depth and season for samples
collected at Agbabu and Temidire villages in the bitumen
deposit area of Ondo State, western Nigeria. The result
of this study could also be used as baseline data for the
environment.
MATERIALS AND METHOD
Sampling
Soil samples were collected from 2 depths, 0- 12cm (Top
soil) and 12 – 24cm (Bottom soil) at each soil sampling
point. 5 composite soil samples were collected from each
sampling point. Samples for soil parameters were
collected in polythene bags and stored at ambient
temperature.
Samples were collected from 30 sampling
stations in the dry season
Samples were collected from 32 sampling
stations in the rainy season
Control sampling points are located in Okitipupa, about
20 kilometers to Agbabu.
Sampling points were geo-located with Geographical
Position System (GPS) to ensure consistency.
Reagent blanks were used in all analyses to check
reagent
impurities
and
other
environmental
contaminations during analyses. Analytical grade
reagents were used for all analyses. All reagents were
standardized against primary standards to determine
their actual concentrations. All glassware used were
washed with detergent and rinsed with water before use.
All instruments used were calibrated before use. Quality
checks were also performed on the instrument by
checking the absorbance after every ten sample runs.
Tools and work surfaces were carefully cleaned for each
sample. Minimum of triplicate readings were taken to
check precision of the analytical method and instrument.
Method
pH was measured in 1:2.5 slurry of soil in water using
Corning pH meter Model 7. Organic carbon was
determined by the wet combustion method (Li et al.,
2004). Available Phosphorus was measured by Bray and
Kurt No. 1 methods. Total nitrogen in the soil samples
was determined by the micro Kjeldahl’s method. Particle
Size Distribution was carried out by the Bouyoucous
hydrometer methods and classified with textural triangle.
Exchangeable Na, K, Ca, and Mg ions were extracted
with neutral (pH 7) ammonium acetate extraction method
by Thomas (1992). The filtrate was used for the
determination of Na and K by flame photometry, while Ca
and Mg by ethylene diamine tetraacetic acid (EDTA)
titration method. Cation Exchange Capacity was
determined from the filtrate transferred into microkjeldahl
flask and titrated with standard H2SO4. Analysis of
Variance (ANOVA) was carried out with the general
linearized model (GLM) of Statistical Analysis System
(SAS) and Duncan’s Multiple Range Group (DMRG) tests
were used to find out statistical differences among
various parameters and generate coefficient of variation,
means, standard errors and ranges (SAS, 2000).
RESULTS AND DISCUSSION
The average concentrations of pH, Org. C, TN and Av. P
in soil in the two seasons and the coefficients of variation
are shown in Table 1. The average concentrations of
Exchangeable ions (K+, Na+, Ca2+, Mg2+, Mn2+) and CEC
in soil in the two seasons and the coefficients of variation
are shown in Table 2. The average percentages of
distribution of particles and the textural classes are
shown Table 3. The Duncan Multiple range grouping at
alpha = 0.05 for soil quality parameters at different
sampling points are also shown in Table 4. Figures 2 to 9
Olubunmi and Olorunsola 201
Table 1. pH, Org. C, TN and Av. P in soil
Sample
AGM2(Top)
AGM2(Bot)
T0S(Top)
T0S(Bot)
T1E(Top)
T1E(Bot)
T1S(Top)
T1S(Bot)
T1N(Top)
T1N(Bot)
T1W(Top)
T1W(Bot)
T2E(Top)
T2E(Bot)
T2S(Top)
T2S(Bot)
T2N(Top)
T2N(Bot)
T3E(Top)
T3E(Bot)
T3N(Top)
T3N(Bot)
T3S(Top)
Season
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
pH
Mean S/D
4.74 0.04
4.67 0.02
5.05 0.01
4.84 0.01
5.84 0.01
6.13 0.11
5.93 0.01
6.19 0.05
5.19 0.00
5.15 0.02
5.23 0.02
5.28 0.13
5.56 0.01
4.34 0.17
5.59 0.00
5.17 0.27
5.04 0.02
5.16 0.02
5.58 0.00
5.55 0.08
6.50 0.05
6.49 0.21
6.65 0.02
6.37 0.26
5.59 0.00
5.43 0.09
6.01 0.00
6.20 0.24
5.17 0.01
4.72 0.04
5.42 0.02
5.50 0.15
5.40 0.01
5.83 0.01
5.52 0.01
5.42 0.22
5.83 0.01
6.12 0.17
5.67 0.03
3.99 0.03
6.62 0.01
6.54 0.22
6.70 0.00
5.59 0.01
5.18 0.06
5.18 0.03
Org. C
%
Mean S/D
2.64 0.05
2.64 0.08
2.03 0.01
2.40 0.02
1.21 0.00
2.02 0.67
1.20 0.00
1.30 0.04
2.01 0.00
2.02 0.06
1.17 0.02
1.85 0.02
2.38 0.00
2.60 0.01
2.27 0.03
2.70 0.14
2.31 0.13
2.63 0.10
2.03 0.01
2.45 0.06
1.11 0.02
1.18 0.02
1.01 0.01
1.07 0.01
2.23 0.02
2.41 0.16
2.28 0.01
2.38 0.03
1.83 0.04
2.07 0.12
1.24 0.02
1.31 0.02
2.29 0.00
2.80 0.19
2.21 0.03
2.95 0.27
1.22 0.01
1.43 0.11
2.10 0.03
2.10 0.04
1.04 0.01
1.05 0.02
1.04 0.00
1.38 0.02
1.29 0.01
1.45 0.01
TN
%
Mean S/D
0.22 0.00
0.20 0.05
0.01 0.00
0.21 0.00
0.15 0.00
0.21 0.02
0.11 0.00
0.18 0.01
0.20 0.00
0.22 0.01
0.13 0.00
0.17 0.01
0.22 0.00
0.23 0.00
0.21 0.00
0.25 0.01
0.21 0.00
0.22 0.01
0.20 0.00
0.20 0.02
0.13 0.00
0.17 0.00
0.10 0.00
0.15 0.01
0.23 0.00
0.26 0.01
0.20 0.00
0.23 0.01
0.21 0.00
0.24 0.01
0.19 0.00
0.22 0.01
0.24 0.00
0.23 0.02
0.23 0.01
0.25 0.03
0.14 0.00
0.18 0.02
0.17 0.00
0.46 0.00
0.13 0.00
0.15 0.01
0.14 0.00
0.46 0.00
0.19 0.00
0.21 0.01
Av.P
µg/g
Mean S/D
20.43 0.22
22.13 0.16
17.13 0.39
18.50 0.08
8.30 0.11
9.30 0.07
8.73 0.11
9.56 0.19
18.10 0.04
18.95 0.10
15.05 0.06
16.40 0.15
19.23 0.09
18.48 0.28
17.95 0.03
18.66 0.25
18.25 0.03
18.38 0.19
18.45 0.21
18.17 0.28
5.05 0.06
5.88 0.08
7.35 0.18
7.21 0.22
11.03 0.09
19.40 0.02
16.90 0.31
17.75 0.18
17.85 0.06
18.40 0.20
16.58 0.18
17.24 0.12
18.25 0.03
19.58 0.53
16.43 0.19
16.93 0.23
11.03 0.09
13.10 0.20
14.13 0.35
27.23 0.92
5.45 0.03
6.05 0.23
5.68 0.05
7.95 0.13
15.93 0.05
18.48 0.09
202 Int. Res. J. Biotechnol.
Table 1 continue
T3S(Bot)
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
T4E(Top)
T4E(Bot)
T4S(Top)
T4S(Bot)
T4N(Top)
T4N(Bot)
OKCtr(Top)
OKCtr(Bot)
Coeff. Of
Var (Top)
F-value
P-value
Coeff. Of
Var (Bot)
F-value
P-value
+
+
2+
6.01
4.57
5.06
5.31
5.05
5.23
5.18
5.07
5.13
4.89
5.03
5.13
5.24
4.89
NA
6.48
NA
5.62
0.00
0.03
0.01
0.26
0.00
0.16
0.03
0.01
0.00
0.05
0.01
0.01
0.01
0.02
0.03
0.02
1.11
2.02
2.04
2.02
2.10
2.35
2.07
2.39
2.03
2.34
2.87
3.09
2.38
3.55
NA
1.05
NA
1.24
0.00
0.03
0.01
0.07
0.01
0.08
0.01
0.01
0.00
0.01
0.03
0.04
0.04
0.02
0.01
0.02
0.13
0.23
0.17
0.20
0.21
0.21
0.19
0.22
0.20
0.25
0.26
0.33
0.20
0.39
NA
0.10
NA
0.14
0.00
0.01
0.01
0.02
0.00
0.02
0.01
0.01
0.00
0.01
0.01
0.01
0.00
0.01
0.00
0.00
15.35
16.38
17.58
18.78
19.45
18.98
19.75
23.31
18.60
21.15
20.68
20.89
18.58
23.13
NA
7.71
NA
9.43
0.03
0.16
0.17
0.21
0.14
0.28
0.13
0.90
0.11
0.29
0.13
0.34
0.17
0.30
0.19
0.09
3.73
6.59
<.0001
6.64
2.66
0.0026
14.50
1.16
0.3193
2.97
10.28
<.0001
3.75
17.03
<.0001
6.18
20.84
<.0001
9.49
33.10
<.0001
3.29
82.10
<.0001
2+
2+
Table 2. Exchangeable ions (K , Na , Ca , Mg , Mn ) and CEC in soil
K+
Sample
AGM2(Top)
AGM2(Bot)
T0S(Top)
T0S(Bot)
T1E(Top)
T1E(Bot)
T1S(Top)
T1S(Bot)
T1N(Top)
Na+
Ca2+
Season
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Mean
1.21
1.25
1.33
1.19
1.10
1.16
0.81
0.81
1.49
1.66
1.02
1.06
1.21
1.16
1.20
1.23
1.20
S/D
0.01
0.01
0.03
0.02
0.00
0.16
0.03
0.01
0.03
0.07
0.01
0.01
0.00
0.01
0.00
0.01
0.00
Mean
0.34
0.30
0.70
0.52
0.32
0.36
0.34
0.28
0.72
0.65
0.33
0.43
0.42
0.33
0.44
0.45
0.35
S/D
0.02
0.02
0.01
0.01
0.01
0.01
0.01
0.01
0.02
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.02
Mean
4.92
4.59
5.35
4.07
2.35
4.88
2.00
2.34
6.28
7.40
5.42
6.08
4.78
3.96
4.10
4.49
6.35
Mg2+
Cmol/kg
S/D Mean
0.47 3.65
0.09 3.96
0.14 2.95
0.05 2.62
0.06 2.68
0.13 2.98
0.00 2.25
0.09 2.74
0.09 3.23
0.19 4.38
0.05 2.48
0.17 2.65
0.03 3.73
0.02 4.05
0.04 3.45
0.08 3.53
0.06 3.65
Mn2+
S/D
0.06
0.03
0.03
0.48
0.05
0.09
0.03
0.04
0.09
0.17
0.05
0.10
0.02
0.02
0.06
0.13
0.06
Mean
0.16
0.22
0.17
0.16
0.02
0.12
0.02
0.14
0.16
0.16
0.19
0.26
0.17
0.17
0.15
0.10
0.18
CEC
S/D
0.01
0.01
0.01
0.01
0.00
0.01
0.00
0.01
0.00
0.01
0.01
0.05
0.00
0.01
0.00
0.06
0.01
Mean
21.85
22.68
20.73
21.63
16.43
57.28
13.83
21.83
20.50
21.10
12.85
15.63
22.68
22.65
21.83
23.60
22.70
S/D
0.06
0.25
0.15
0.17
0.17
4.02
0.08
0.21
0.15
0.37
0.06
0.09
0.29
0.10
0.21
0.58
0.15
Olubunmi and Olorunsola 203
Table 2 continue
T1N(Bot)
T1W(Top)
T1W(Bot)
T2E(Top)
T2E(Bot)
T2S(Top)
T2S(Bot)
T2N(Top)
T2N(Bot)
T3E(Top)
T3E(Bot)
T3N(Top)
T3N(Bot)
T3S(Top)
T3S(Bot)
T4E(Top)
T4E(Bot)
T4S(Top)
T4S(Bot)
T4N(Top)
T4N(Bot)
OKCtr(Top)
OKCtr(Bot)
Coeff. Of
Var (Top)
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
1.44
1.17
1.39
0.08
0.80
1.04
1.06
1.21
1.22
1.08
1.18
1.62
1.58
1.04
1.17
1.18
1.20
1.21
1.24
1.04
1.28
1.19
4.20
0.45
1.28
0.45
0.67
1.16
1.16
1.08
1.42
1.19
1.46
1.21
1.33
1.18
1.37
1.20
1.25
1.39
1.47
1.26
2.38
NA
1.25
NA
1.09
6.91
0.02
0.01
0.02
0.01
0.02
0.02
0.02
0.00
0.02
0.01
0.04
0.04
0.02
0.02
0.04
0.01
0.01
0.01
0.03
0.02
0.10
0.00
0.01
0.01
0.08
0.01
0.02
0.02
0.01
0.01
0.00
0.00
0.15
0.01
0.05
0.02
0.09
0.00
0.01
0.04
0.03
0.02
0.04
0.01
0.01
0.35
0.46
0.40
0.29
0.34
0.37
0.30
0.48
0.47
0.33
0.37
0.52
0.47
0.31
0.32
0.42
0.46
0.38
0.34
0.34
0.33
0.47
1.49
0.30
0.29
0.25
0.28
0.29
0.33
0.34
0.48
0.46
0.49
0.67
0.64
0.33
0.45
0.45
0.35
0.84
0.73
0.47
0.91
NA
0.47
NA
0.38
7.62
0.01
0.03
0.02
0.00
0.02
0.01
0.02
0.00
0.02
0.02
0.02
0.04
0.02
0.00
0.02
0.01
0.02
0.00
0.02
0.02
0.01
0.01
0.03
0.00
0.01
0.01
0.01
0.00
0.11
0.00
0.02
0.01
0.01
0.01
0.02
0.00
0.01
0.01
0.01
0.01
0.03
0.01
0.03
0.01
0.03
7.20
5.05
5.28
2.55
2.60
2.55
2.80
6.48
6.35
5.93
6.31
6.48
5.49
4.80
5.22
3.50
4.00
4.30
4.13
3.15
3.52
3.92
7.40
2.50
2.90
2.80
3.36
4.45
4.89
3.28
4.99
5.25
5.76
5.58
6.80
5.13
5.92
4.98
5.57
6.25
6.88
5.75
7.39
NA
2.81
NA
2.29
4.89
0.19
0.06
0.04
0.06
0.09
0.10
0.04
0.09
0.17
0.05
0.14
0.09
0.04
0.00
0.08
0.15
0.18
0.16
0.15
0.06
0.14
0.04
1.94
0.15
0.08
0.04
0.09
0.17
0.04
0.05
0.03
0.10
0.19
0.09
0.28
0.05
0.12
0.03
0.06
0.13
0.21
0.17
0.17
0.04
0.05
4.00
3.10
3.78
1.78
2.39
1.15
1.88
3.18
3.50
2.95
3.38
3.00
4.12
3.10
3.38
3.33
3.20
3.43
3.35
2.43
2.87
2.70
8.04
1.30
1.64
1.35
1.75
3.38
3.69
2.78
3.63
3.15
3.51
3.23
5.75
3.50
4.09
3.13
4.09
3.55
4.10
3.00
4.96
NA
1.65
NA
2.77
8.31
0.21
0.04
0.25
0.03
0.17
0.06
0.11
0.05
0.11
0.03
0.28
0.00
0.19
0.04
0.28
0.13
0.34
0.09
0.24
0.05
0.11
0.00
0.02
0.04
0.03
0.06
0.03
0.09
0.10
0.03
0.02
0.06
0.19
0.09
0.05
0.00
0.04
0.05
0.03
0.06
0.31
0.00
0.09
0.20
0.04
0.16
0.16
0.65
0.06
0.05
0.04
0.08
0.15
0.17
0.14
0.17
0.06
0.14
0.02
0.10
0.17
0.18
0.14
0.17
0.10
0.08
0.12
0.43
0.06
0.53
0.07
0.12
0.11
0.13
0.05
0.09
0.12
0.18
0.12
0.13
0.17
0.20
0.17
0.16
0.15
0.19
0.15
0.22
NA
0.24
NA
0.05
50.45
0.01
0.00
0.49
0.01
0.01
0.00
0.04
0.00
0.01
0.00
0.01
0.01
0.01
0.00
0.07
0.00
0.02
0.00
0.02
0.00
0.00
0.00
0.00
0.01
0.01
0.01
0.01
0.00
0.00
0.00
0.00
0.00
0.02
0.01
0.01
0.00
0.01
0.00
0.00
0.00
0.01
0.00
0.01
0.19
0.01
23.10
20.90
11.53
15.85
14.56
11.53
12.68
21.98
22.03
19.85
23.00
21.70
22.35
20.38
17.95
22.30
23.40
21.35
22.13
18.13
19.28
20.23
27.95
12.43
12.20
12.33
15.18
21.03
22.33
13.70
20.73
22.25
23.28
22.15
22.84
22.33
23.55
22.48
22.33
22.40
23.25
22.18
26.28
NA
12.88
NA
16.55
67.16
0.17
0.20
0.05
0.20
0.19
0.05
0.11
0.11
0.62
0.06
0.27
0.11
0.17
0.17
0.25
0.23
0.30
0.17
0.14
0.25
0.35
0.11
0.29
0.19
0.28
0.13
0.14
0.20
0.08
0.15
0.11
0.13
0.96
0.13
0.57
0.09
0.41
0.05
0.11
0.15
0.21
0.09
0.09
0.25
0.13
204 Int. Res. J. Biotechnol.
Table 2 continue 1
F-value
P-value
Coeff. Of
Var (Bot)
F-value
P-value
3.16
<.0004
4.60
<.0001
25.15
<.0001
2.91
0.0011
0.57
0.8846
1.04
0.4227
3.62
599.10
<.0001
6.83
169.00
<.0001
15.66
4.15
<.0001
8.35
53.44
<.0001
116.42
1.15
0.3242
2.15
82.67
<.0001
Table 3. Particle Size Distribution (Sand, Silt, Clay) and textural class of soil
Sand
Sample
AGM2(Top)
AGM2(Bot)
T0S(Top)
T0S(Bot)
T1E(Top)
T1E(Bot)
T1S(Top)
T1S(Bot)
T1N(Top)
T1N(Bot)
T1W(Top)
T1W(Bot)
T2E(Top)
T2E(Bot)
T2S(Top)
T2S(Bot)
T2N(Top)
T2N(Bot)
Season
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Mean
20.00
11.75
11.75
9.75
24.00
23.55
24.00
23.80
11.50
17.37
23.80
23.50
6.00
62.85
9.00
9.00
17.50
17.50
17.25
13.75
67.75
74.22
76.00
68.33
16.50
12.40
11.00
11.23
13.00
23.48
23.50
23.10
13.75
14.93
8.00
14.23
S/D
0.00
0.09
0.25
0.25
0.00
0.19
0.00
0.36
0.29
0.16
0.37
0.29
0.40
1.78
0.00
0.21
0.12
0.12
0.25
0.35
0.25
0.33
0.00
0.07
0.29
0.08
0.00
0.33
0.00
0.16
0.29
0.30
0.25
0.26
0.41
0.21
Silt
%
Mean S/D
53.75 0.25
29.55 0.21
30.00 0.00
30.38 0.06
41.00 0.00
39.78 1.32
41.00 0.00
42.60 0.23
32.50 0.29
43.35 0.41
42.00 0.00
31.95 0.42
57.50 0.29
3.90 0.09
48.00 0.00
48.08 0.13
56.00 0.00
43.41 0.19
44.00 0.00
46.08 0.13
3.50 0.29
5.26 0.23
4.00 0.00
3.33 0.22
44.25 0.25
47.28 0.37
46.00 0.00
33.70 0.13
30.50 0.29
41.53 0.32
41.75 0.25
41.98 0.18
52.75 0.48
46.33 0.32
53.75 0.25
46.23 0.35
Clay
Mean
26.25
58.90
58.50
58.25
35.00
34.05
35.00
35.50
56.00
38.43
34.25
40.70
36.50
30.68
20.00
28.20
23.00
40.38
43.00
56.20
29.00
20.76
20.00
28.20
39.00
41.85
43.00
56.20
56.50
35.03
35.00
35.65
33.25
39.18
38.50
38.85
Textural
Class
S/D
0.25
0.17
0.29
0.09
0.00
0.19
0.00
0.64
0.41
0.09
0.25
1.63
0.29
2.11
0.00
0.42
0.00
0.54
0.00
0.36
0.00
0.10
0.00
0.16
0.00
0.63
0.00
0.28
0.29
0.09
0.00
0.28
0.25
0.33
0.29
0.03
Clay loam
Clay loam
Clay loam
Clay loam
Silty clay loam
Silty clay loam
Silty clay loam
Silty clay loam
Silty clay
Silty clay
Clay loam
Clay loam
Clay loam
Clay loam
Loam
Loam
Silty clay loam
Silty clay loam
Silty clay loam
Silty clay loam
Silty clay
Silty clay
Clay loam
Clay loam
Silty clay loam
Silty clay loam
Silty clay
Silty clay
Clay loam
Clay loam
Silty clay loam
Silty clay loam
Silty clay loam
Silty clay loam
Silty clay
Silty clay
Olubunmi and Olorunsola 205
Table 3 continue
T3E(Top)
T3E(Bot)
T3N(Top)
T3N(Bot)
T3S(Top)
T3S(Bot)
T4E(Top)
T4E(Bot)
T4S(Top)
T4S(Bot)
T4N(Top)
T4N(Bot)
OKCtr(Top)
OKCtr(Bot)
Coeff. Of
Var (Top)
F-value
P-value
Coeff. Of
Var (Bot)
F-value
P-value
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
Dry
Rainy
28.50
29.00
15.00
6.10
67.75
67.68
67.25
76.53
23.00
22.75
33.00
7.60
5.00
15.40
9.75
9.47
17.00
17.10
7.75
11.68
12.00
10.83
12.75
12.15
NA
75.65
NA
78.35
0.29
1.17
0.00
0.04
0.25
0.29
0.25
0.21
0.00
0.13
0.00
0.14
0.00
0.22
0.25
0.11
0.00
0.06
0.25
0.13
0.00
0.25
0.09
0.23
5.40
38.00
37.98
46.00
33.70
4.50
4.49
4.00
3.60
41.50
42.00
30.00
53.38
54.00
44.21
40.00
38.65
44.25
44.70
53.50
30.59
30.50
30.40
46.50
47.63
NA
3.93
NA
41.18
0.00
0.20
0.00
0.13
0.29
0.16
0.00
0.22
0.29
0.04
0.00
0.25
0.00
0.13
0.00
1.04
0.25
0.15
0.29
0.31
0.29
0.40
0.29
0.19
0.05
0.06
33.25
32.60
39.00
59.38
28.00
27.88
28.50
20.05
35.25
35.35
37.00
38.88
41.00
38.48
50.50
50.90
38.50
38.13
38.88
39.00
57.50
58.43
41.00
40.25
NA
20.33
NA
34.70
0.25
0.46
0.00
0.36
0.00
0.43
0.29
0.03
0.25
0.14
0.00
0.14
0.00
1.26
0.29
0.46
0.29
0.13
0.00
0.14
0.29
0.31
0.00
0.10
0.23
0.04
3.16
630.42
<.0001
1.94
1093.41
<.0001
2.77
306.54
<.0001
81.79
0.36
0.9815
1.60
603.00
<.0001
1.89
269.02
<.0001
Sandy clay
Sandy clay
SandyClayLoam
SandyClayLoam
Silty loam
Silty loam
Silty clay loam
Silty clay loam
Silty clay loam
Silty clay loam
Silty clay loam
Silty clay loam
Sandy clay
Sandy clay
Sandy clay
Sandy clay
Sandy clay
Sandy clay
Silty clay loam
Silty clay loam
Silty loam
Silty loam
Silty clay
Silty clay
206 Int. Res. J. Biotechnol.
Table 4. Duncan Multiple range grouping for soil (alpha = 0.05)
Sampling
Point
T0S(Top)
T1S(Top)
T2S(Top)
T3S(Top)
T4S(Top)
T1E(Top)
T2E(Top)
T3E(Top)
T4E(Top)
pH
B
F,G
G
D,E
E,F,G
E,F,G
C
B
D,E,F
Org.
C
G,H
C
E
F
D
E
D
F,G
E
TN
E,F
B,C,D
B,C,D
D,E
C,D,E
C,D,E
B
F,G
E,F
Av.P
H
C,D
E
F
A
D,E
C
G
E
K+
G
E,F,G
A
F,G
C,D,E
E,F,G
E,F,G
F,G
C
Na+
E,F,G
E
C
G,H
C,D
B
C
E,F,G
C
Ca2+
H
G
D
F
E
A
C
I
E
Mg2+
D
A
B,C
B,C
A,B
A,B
C
D
C
Mn2+
E
A,B,C,D
C,D,E
B,C,D,E
A,B
B,C,D
B,C,D
D,E
B,C,D
CEC
A
A,B
A,B
A,B
A,B
A,B
A,B
B
A,B
Sand
F
D
I
G
J
L
L
E
N
Silt
E
H
G
D
C
F
B
F
A
Clay
H,I
I,J
C
G,H
F
B
E
J
M
T1W(Top)
A
H,I
F,G
J
I
F,G,H
J
E
E
B
B
I
M
T1N(Top)
E,F,G
C
B,C,D
E
C,D
E,F
A,B
A,B
A,B,C,D
A,B
H
A
K
T2N(Top)
T3N(Top)
T4N(Top)
AGM2(Top)
OKCtr(Top)
Dry
Season(Top)
Rainy
Season(Top)
T0S(Bot)
T1S(Bot)
C,D
A
E,F,G
H
A
B,C
I
A
B
I
B,C
G
A
C,D,E
H
C,D
J
B
A
I
E,F,G
J
B
D,E,F
H
D
H
A
F,G,H
C,D
H
J
B,C
F
J
C
F
A,B
A,B
F
A,B,C
E
A,B,C,D
A,B
A
A,B
B
A,B
A,B
B
L
C
M
K
A
A
I
H
D
G
L
A
D
N
A
B
B
B
B
A
B
B
B
A
B
A
A
A
B
E
A
H
C
A
H
C,D
A
I
D
A
H
D
A
G
D
A
H
E,F
A
G
C,D
A
B,C
B,C
A
I
B
A
B
B
B
E,F
B
B
J
F
T2S(Bot)
C,D,E
H
E,F
F,G
E
G
C,D,E
C,D,E
B,C
E
B
E
J
T3S(Bot)
T4S(Bot)
T1E(Bot)
T2E(Bot)
T3E(Bot)
E,F
G,H
E,F
B
H
G
E
F
D
B
G
C,D,E
H
C,D,E,F
A
H
B
H
E,F
A
C,D
C,D
G
E
A
E
E
E,F
F
A
F
C,D
B,C
A,B
B,C
D,E
C
F,G
E
A
B,C
B,C
A,B,C
B,C
A,B
F
B
H
C,D
A
B
B
B
B
B
E,F
E
H
G
G
I
D
E
C
C,D
T4E(Bot)
T1W(Bot)
T1N(Bot)
F,G
A
C,D
D,E
I
D,E
D,E,F
I
E,F
C
J
D
C
F,G
C
B
D
E,F
A,B
G,H
C,D
C,D,E
H
C,D,E
B,C
B,C
A
B
J
C,D
B
A
B
G
J
D
B
K
H
T2N(Bot)
T3N(Bot)
T4N(Bot)
C,D.E
B
F,G
C
H
A
C
H,I
B
G
J
A
C,D
I
B
F
H
B
E,F
G
A
C,D,E
H
B
B,C
B,C
B,C
C
I
A
B
A
B
A
J
C
I
K
G
G,H
C
D,E
H
F
H,I
D,E
I
C,D
E,F
C
E,F
D,E,F
G,H
F
F,G
B,C
C
D
G
B
A
I
F
A
J
A
B
B
B
B
B
B
B
B
B
A
B
B
B
A
A
A
A
A
A
A
A
A
A
A
A
AGM2(Bot)
OKCtr(Bot)
Dry
Season(Bot)
Rainy
Season(Bot)
Olubunmi and Olorunsola 207
Figure 2. pH, Org. C, TN and Av. P in AGM2and T0S
Figure 3. pH, Org. C, TN and Av. P in T1E and T1S
Figure 4. pH, Org. C, TN and Av. P in T1N and T1W
Figure 5. pH, Org. C, TN and Av. P in T2E and T2S
Figure 6. pH, Org. C, TN and Av. P in T2N and T3E
Figure 7. pH, Org. C, TN and Av. P in T3N and T3S
Figure 8. pH, Org. C, TN and Av. P in T4E and T4S
Figure 9. pH, Org. C, TN and Av. P in T4N and OKCtr
208 Int. Res. J. Biotechnol.
+
+
2+
2+
2+
+
+
2+
2+
2+
and CEC in AGM2 and T0S
+
+
2+
2+
2+
and CEC in T1E and T1S
Figure 15. K , Na , Ca , Mg , Mn
+
+
2+
2+
2+
and CEC in T1N and T1W
Figure 16. K , Na , Ca , Mg , Mn
Figure 10. K , Na , Ca , Mg , Mn
Figure 11. K , Na , Ca , Mg , Mn
Figure 12. K , Na , Ca , Mg , Mn
+
+
2+
2+
2+
Figure 13. K , Na , Ca , Mg , Mn
Figure 14. K , Na , Ca , Mg , Mn
+
and CEC in T2E and T2S
show charts of the concentrations of pH, Org. C, TN and
Av. P in dry season and rainy season in different stations.
and CEC in T2N and T3E
+
+
2+
2+
2+
and CEC in T3N and T3S
+
+
2+
2+
2+
and CEC in T4E and T4S
+
2+
2+
2+
Figure 17: K , Na , Ca , Mg , Mn
and CEC in T4N and OKCtr
Figures 10 to 17 show charts of the concentrations of
Exchangeable ions (K+, Na+, Ca2+, Mg2+, Mn2+) and CEC
Olubunmi and Olorunsola 209
in dry season and rainy season in different stations.
In the topsoil samples in the two seasons, as shown in
Tables 1, 2 and 3, at α = 0.05, the coefficient of variation
of Total Nitrogen (TN) in all locations was 14.50 (F=1.16
and p = 0.3193), Mn2+ was 50.45 (F=0.57 and p =
0.8846) and Cation Exchange Capacity (CEC) was 67.16
(F=1.04 and p = 0.4227), all showing no statistical
significance (i.e. There was no interaction between the
values of the parameters and the different stations. The
values did not change as the stations changed). This
means there was no wide variation in values of the
parameters from one location to the other. There was
probably no difference in the sources of these
parameters from one location to the other in the top soil.
In the multi-elemental analysis of Nigerian bitumen and
the physical constants characterization of hydrocarbon
content by Adebiyi et al. (2006), twelve elements – K, Ca,
Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As and Pb were detected.
Therefore, the only common source of Mn2+ in the soils of
this environment was bitumen.
In the top soil also, at α = 0.05, the remaining
parameters pH, Total Organic Carbon (TOC), Av.P, K+,
Na+, Ca2+, Mg2+, Sand, Silt and Clay had coefficient of
variation, F and p values that showed statistical
significance. This means there was wide variations in
their values from one location to the other. Therefore, for
a particular parameter, the sources varied from one
location to the other.
In the bottom soil samples in the two seasons, at α =
0.05, the coefficient of variation of Mn2+ was 116.42
(F=1.15 and P = 0.3242) and Sand (soil texture) was
81.79 (F=0.36 and P = 0.9815), also showing no
statistical significance. This means there was no wide
variation in values from one location to the other. This
confirms that there was a common source of Mn2+ in the
environment which was bitumen. In the bottom soil also,
at α = 0.05, the remaining parameters pH, Total Organic
Carbon (TOC), TN, Av.P, K+, Na+, Ca2+, Mg2+, Silt and
Clay had coefficient of variation, F and P values that
showed statistical significance indicating that, for the
parameters in this group the values varied widely and the
sources varied from one location to the other.
The Duncan Multiple Range Grouping (DMRG) at α =
0.05 as shown in Table 4 shows that the class of means
varied from location to the other, though there might be
2+
many classes in a location. In Mn and CEC, in the
topsoil and bottom soil, particular classes of means were
repeated throughout the locations showing that there
were no significant differences between the locations,
confirming further that Mn2+ had a common source in the
environment which was bitumen. In all other parameters
the classes of means varied distinctly from one station to
another, showing significant differences. This confirms
further that the means of values varied from one location
to another and the sources of the parameters were
probably different. The classes of means in the dry
season and rainy season are also shown in Table 4. In
top soil and bottom soil, the means of values of the
parameters were higher in the rainy season than in the
dry season. All the parameters in the two seasons,
except pH (topsoil), CEC (topsoil) and sand – soil texture
(bottom soil), showed significant differences. This
indicates that rains had effects on the concentrations of
these parameters in soil.
The minimum pH in the dry season was 4.74±0.04 and
the maximum was 6.70±0.00 while in the rainy season
the minimum was 3.99±0.03 and the maximum was
6.54±0.22. The recommended range of pH for optimum
nutrient availability in soil is 6.0 to 7.5. Therefore, all the
stations sampled except T1W (Top and Bot), T2E (Bot),
T3E (Top), T3N (Top and Bot) were acidic in both
seasons. pH values were lower in the rainy season than
in the dry season. This is in agreement with Onweremadu
et al. (2007). Exchangeable bases were leached through
+
the pores of soil in the rainy season, leaving behind H .
pH in the bottom soil in most of samples were higher
while some of the samples such as T2N, T3E, T3N, T4E
and T4S had higher pH in top soil. This is because the
variability in soil pH and depth depends on many factors
such as natural weathering, organic decay, chemical
fertilizers, tillage practices acid rain and some
anthropogenic activities. Soil at Agbabu bitumen deposit
area is acidic because soils acidify naturally over time.
The minimum Total organic carbon in the dry season
was 1.01±0.01% and the maximum was 2.87±0.03%
while in the rainy season the minimum was 1.05±0.02%
and the maximum is 3.55±0.02%. These were all within
the range of 1 ppm and 10 ppm given in the guidelines
developed by the Ontario Ministry of Environment,
Canada (Persaud et al., 1992). TOC was slightly higher
in the rainy season than in the dry season probably due
to higher decomposition and decay of organic matter in
the rainy season. TOC values were higher in the topsoil
than the bottom soil in most of the samples. This agrees
with the results of Claveria et al. (2004). This is because
organic matter, a primary source of organic carbon,
accumulates more at the topsoil.
The lowest total nitrogen content in the dry season was
0.01±0.00% and the highest was 0.26±0.01% while in the
rainy season the lowest was 0.15±0.01% and the highest
was 0.46±0.00%. All TN values obtained apart from that
of AGM2 (Bot) (0.01±0.00%), were within the range
obtained in most surface soils which is 0.02% to 0.5%,
with 0.15% being representative of cultivated soils
(Claveria et al., 2004). There were higher values of TN in
the rainy season than in the dry season. This was
probably due to denitrification which occurs when soils
are saturated during relatively warm conditions. Due to
210 Int. Res. J. Biotechnol.
bitumen stripping at Temidire village, it was relatively
warmer, thereby leading to higher denitrification and
consequently low TN value. More than half of the
samples also had higher percentage of TN in the topsoil
than in the bottom soil. These followed the same trend
with TOC because nitrogen is usually stored as a major
part of soil organic matter from which it is released by
mineralization; therefore, the distribution of nitrogen is
usually closely related to soil organic matter.
The lowest mean concentration of Av.P in the dry
season was 5.05±0.06µg/g and the highest was
20.68±0.13µg/g while in the rainy season the lowest
5.88±0.08µg/g and the highest was 27.23±0.92µg/g.
According to The General Guide for Crop Nutrient
Recommendations in Iowa (Mallarino et al., 2000), many
of the stations had Av. P concentrations within the
optimum Av. P range of 11 to 20 ppm while T1W (Top
and Bot.), T3N (Top and Bot.) and T0S (Top and Bot)
had concentrations in the region of 0 -10ppm that are
considered low in both seasons, while AGM2 (Top), T3E
(Bot), T4S (Top) and T4N (Bot) all in the rainy season
had concentrations in the range of 21 – 31+ that are
considered high. Except in very few locations, average
concentrations of Av.P in the rainy season were higher
than that of dry season. This is because there was less
uptake of P in cold soil, that is, less P fixation and
consequently higher Av. P in soil. High TOC leads to less
fixation of phosphorous. Av. P was evenly distributed in
the topsoil and bottom soil while TOC was higher in the
topsoil than in the bottom soil, though it is expected that
soils with high TOC will have high Av. P. The observed
trend here is probably due to anthropogenic activities and
easy absorption of phosphorous by plants.
In the dry season, sampling point T1W (Top) had the
lowest K+ value of 0.08±0.01cmol/kg while sampling point
T2S (Top) had the highest value of 1.62±0.04cmol/kg. In
the rainy season sampling point T3N (Bot) had the lowest
K+ value of 0.67±0.02cmol/kg while sampling point T3E
(Bot) had the highest value of 4.20±0.01cmol/kg. In soils,
values of K+ below 120ppm (0.3 Cmol/kg) are considered
to be too low while values above 800ppm (2.1 cmol/kg)
+
are considered to be excessive. The values of K
obtained in this study were within the recommended
range in soils except 0.08cmol/kg obtained in T1W (Top)
which was too low and 4.20±0.01cmol/kg obtained in T3E
(Bot) which was too high. Relatively low values obtained
in some of the stations were probably due to leaching
because of the sandy nature of the soil there. Most of the
+
sampling stations had higher K values in the rainy
season than in the dry season due to water logging. The
variation in concentration of K+ with depth did not follow a
specific pattern. In some of the stations it decreased with
depth while in other ones it increased. There is no
agreement in literature about variations of K+ with depth
(Toni et al., 2009).
In the dry season, sampling point T3N (Bot) had the
lowest Na+ value of 0.25±0.01cmol/kg while sampling
point T4N (Top) had the highest value of
0.84±0.01cmol/kg. In the rainy season sampling point
T0S (Bot) had the lowest Na+ value of 0.28±0.01cmol/kg
while sampling point T3E (Bot) had the highest value of
1.49±0.03cmol/kg. These values were within the
recommended range of 0.1cmol/kg to 3.0cmol/kg. Na+
values were higher in the rainy season than in the dry
season probably due to water logging. This is in
agreement with the findings of Toni et al. (2009). The
variation in concentration of exchangeable cation Na+
with depth did not follow a specific pattern. In some of the
stations it decreased with depth while in other ones it
increased. There is no agreement in literature about
variations of Na+ with depth (Toni et al., 2009).
Calcium ion values ranged between 2.0cmol/kg at
sampling point T0S (Bot) to 6.48±0.09cmol/kg at
sampling points T2E (Top) and T2S (Top) in the dry
season. In the rainy season, the values ranged between
2.34±0.09cmol/kg at sampling point T0S (Bot) and
7.40±1.94cmol/kg at T3E (Bot). Most of the stations had
values that were less than the recommended range of
1000ppm (5.0cmol/kg) to 2000ppm (10.0cmol/kg). This is
as a result of slightly low pH values obtained at Agbabu
and Temidire bitumen deposit area. Acid soils hold less
Ca2+. The values of Ca2+ obtained were higher in the
rainy season than in the dry season. This is due to water
logging which increased solubility of organic carbon thus
decreasing organic matter and releasing cations Ca2+ and
Mg2+. Variations of concentrations with depth did not
show a specific pattern probably due to inaccurate
measurement of the two depths of collecting soil
samples.
Magnesium
ion
values
ranged
between
1.15±0.06cmol/kg at sampling point T1W (Bot) to
3.73±0.02cmol/kg at sampling point T1S (Top) in the dry
season. In the rainy season, the values ranged between
1.64±0.03cmol/kg at sampling point T3N (Top) and
8.04±0.02cmol/kg at station T3E (Bot). In both dry and
rainy seasons, only T1W (Bot) in the dry season, T3N
(Top) in the dry season and T3N (Bot) in the dry season
had concentration values that were within the
recommended value of 60 ppm (0.5cmol/kg) to 180ppm
(1.5cmol/kg). The remaining stations had values that
2+
were above the normal range, though Mg toxicity is very
2+
rare. The high Mg concentration was probably due to
+
low levels of other exchangeable cations such as K or
2+
Ca and the percentage of clay in soil in the bitumen
deposit impacted environment. The calcium/magnesium
ratios were calculated by dividing the concentration of
calcium by the concentration of magnesium. Most of the
ratios obtained were less than 2 while the preferred ratio
Olubunmi and Olorunsola 211
is 3. This indicates that it was difficult for plants to take up
potassium, and there could be problems with soil
structure breakdown (Reid and Dioru, 2004).
The values of Mg2+ obtained were higher in the rainy
season than in the dry season due to water logging which
caused increased solubility of organic carbon. Variations
of concentrations with depth did not show a specific
pattern probably due to inaccurate measurement of the
two depths of collecting soil samples.
Manganese
ion
values
ranged
between
0.02±0.00cmol/kg at sampling point T0S (Top) and
0.18±0.01cmol/kg at sampling point T1N (Top) in the dry
season. In the rainy season, the values ranged between
0.05±0.00cmol/kg at sampling points T3S (Bot) and
0.65±0.49cmol/kg at station T1N (Bot). The values of
2+
Mn obtained were low. Since the maximum pH obtained
in this study was 6.12, the values were below toxicity
2+
level of Mn which occurs at pH>7.
In the dry season, the lowest CEC was
11.53±0.05cmol/kg at sampling point T1W (Bot) and the
highest was 22.48±0.05cmol/kg at sampling point T4S
(Bot). In the rainy season, the lowest CEC was
11.53±0.05cmol/kg at sampling point T1N (Bot) and the
highest was 57.28±4.02cmol/kg at sampling point T0S
(Top). These values of CEC were all within the usual
range of 11-50meq/100g (11-50cmol/kg), apart from that
of T0S (Top) in the rainy season at Agbabu village.
Values o f CEC within the usual range imply that the soil
at Agbabu bitumen deposit area will be resistant to
changes in pH and will be able to retain the cations (K+,
NH4+, Ca2+ and Mg2+) in form that is available to plants.
Statistical analysis and Duncan multiple range analysis at
α=0.05 showed that soils in the environment had a
common source of CEC variation among the stations
which was bitumen. The high value of CEC obtained at
T0S (Top) which is around bitumen well NBC-7 shows
that bitumen had impacted that environment slightly. The
values of CEC obtained were higher in the rainy season
than in the dry season leading to increase in Ca2+ and
Mg2+ concentrations. CEC values were higher in the
topsoil than in the bottom soil in most of the station. This
was in agreement with the findings of Toni et al. (2009).
Though Ca2+ and Mg2+ did not vary in any regular pattern
with depth in this study, TOC decreased with increase in
depth.
The textural classes of the sampling points were
determined with the soil textural triangle (Table 3).
Average percentage for each type of soil was calculated
for all the sampling stations and the soil textural triangle
was used to classify the soil in the whole environment.
The average percentages were as follows:
Sand = 23.90%, Silt = 36.52%, Clay = 38.77%.
Soil at Agbabu bitumen deposit was classified as clayloam. This accounts for the high values of Mg2+ and
cation exchange capacity (range 11 -50meq/100g) of soil
at Agbabu and Temidire.
CONCLUSION
This work has shown that from the Coefficient of variation
by the general linearized model of statistical analytical
system and Duncan multiple range grouping at α = 0.05,
the sources of the parameters varied from one location to
another apart from Mn2+ that had a common source which
was bitumen. Most of the parameters had higher values
in the topsoil than bottom soil. The means of values of
the parameters were higher in the rainy season than in
the dry season and most of the means of the parameters
show significant differences indicating that rains had
effects on the concentrations of these parameters in soil.
The values of most of the parameters such as Total
organic carbon, Total Nitrogen, K+, Na+, Mn2+, Cation
exchange capacity, in most of the stations were within the
recommended limits. Most of the stations were acidic in
both seasons. Values of CEC were all within the usual
range apart from that of T0S (Top) in the rainy season
that is higher due to the presence of bitumen well NBC-7
around the sampling area. pH values were lower in the
rainy season than in the dry season. TOC, TN, Av. P, K+,
Na+, Ca2+, Mg2+, CEC values were higher in the rainy
season than in the dry season. TN, TOC, CEC values
were higher in the topsoil than the bottom soil in most of
the samples. pH, Av. P, K+, Na+, Ca2+, Mg2+ variation in
concentration with depth did not follow a specific pattern.
Soil at Agbabu bitumen deposit was classified as clayloam. The quality of soils of Agbabu and Temidire farm
settlements has depreciated slightly over the years due to
continuous use, as indicated in the acidity of the soils.
Bitumen deposit has slightly impacted the soil of the
environment and it will be necessary to improve its quality
now and monitor these parameters from time to time
because mining will contaminate soil in the environment
more.
ACKNOWLEDGEMENT
The authors which to express their gratitude to the
Department of Chemistry, University of Ado-Ekiti, AdoEkiti, Nigeria and the management of the University of
Ado-Ekiti, Nigeria, for their support.
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