Surface (0–15 cm) and
subsurface (15–30 cm) depth of soil samples contaminated with petroleum
hydrocarbons were collected from impacted sites at Ebudu community in River
State, Nigeria, after a field reconnaissance survey. An uncontaminated soil
sample collected 500m from the impacted sites, but within the same
geographical area, was used as a control. Trace heavy metals such as, As,
Cd, Cr, Cu, Fe, Hg, Mn, Ni, and Zn which are normal constituents of
petroleum hydrocarbon were determined by atomic absorption spectroscopy.
Trace heavy metal concentrations ( mg kg− 1) were: As, 1.00 – 4.42 mg
kg− 1; Cd, 1.76 – 7.50 mg kg− 1;Cr, 1.07 – 6.38 mg kg−
1;Cu, 1.84 – 9.78 mg kg− 1;Fe,
6.64 – 24.3 mg kg− 1; Hg 1.0– 4.18 mg kg− 1; Mn, 3.42 – 13.62 mg
kg− 1;Ni, 2.02 –7.26 mg kg− 1; Pb, 4.57 – 22.3 mg kg− 1;
and Zn, 3.38 – 21.71 mg kg− 1;in surface and subsurface soils. A positive correlation among the
heavy metal contents shows pollution is from the same source (both oil
pollution and allochthonous inputs). Fe, Mn, Pb and Zn were more enhanced
(p<0.05) in the oil-spill-polluted soils, especially at surface depth,
and this may be attributed to the fact that metal profiles in polluted soils
penetrate a little below the 10-cm region, even after many years, thereby
making the metal concentration in surface soils usually higher.
Accepted:18/03/2024
Published: 08/04/2024
*Corresponding
Author
Dr. Onyebuchi Nwadiogbu
E-mail: onyebuchinwadiogbu@ yahoo.com
Phone: +2348037573741
Keywords: Soil
Pollution, Petroleum Hydrocarbon, Heavy Metal.
INTRODUCTION
Contamination
of soil environment by hydrocarbons (mostly petroleum hydrocarbons) is becoming
prevalent across the globe. This is probably due to heavy dependence on
petroleum as a major source of energy throughout the world. The amount of
natural crude oil seepage was estimated to be 600,000 metric tons per year with
a range of uncertainty of 200,000 metric tons per year (1). Incidence of
environmental pollution due to high rate of petroleum related activities in the
Niger Delta area of southern Nigeria and other oil producing areas of the world
has been associated with frequent oil spills, especially through oil wells blow
outs, tanker accidents, bunkering, rupture of pipelines and sabotage. Disasters
arising from such incidence results in the discharge of crude oil into the
environment affecting both soil, air and water bodies.This threatens human health and that of the
organisms that are dependent on the soil (2). Pollution of the soil with
petroleum derivatives is often observed in municipal soils around industrial
plants and in areas where petroleum and natural gas are obtained.
Nigerian crude oil is known to have about
0.003 – 42.31 mg/kg of transition metals (V, Cr, Mn, Fe, Co, Ni and Cu) (15);
some of which cannot be completely removed during the crude refining processes.
Once they enter ecosystems, petroleum-based products initiate a series of
processes, affecting both biotic and abiotic elements (12). Heavy metals
contaminated soil from industrial waste; electronic wastes etc. on the other
hand pose a serious threat to both man and animals in the environment if not properly
remediated to the innocuous level. Environmental pollution by heavy metals
which are released into the environment through various anthropogenic
activities such as mining, energy and fuel production, electroplating,
wastewater sludge treatment and agriculture is one of the world’s major
environmental problem. Heavy metals or trace metals refer to a large group of
trace elements which are both industrially and biologically important.
Initially, heavy metals are naturally present in soils as natural components
but as of now, the presence of heavy metals in the environment has accelerated
due to human activities. This is a widespread problem around the world where
excessive concentration of heavy metals such as Pb, Zn, Cr, Cu, Cd, Hg, and As
can be found in soils (10).
Soil contamination by heavy metals is
consequently the most critical environmental problems as it poses significant
impacts to the human health as well as the ecosystems. The contaminants are
able to infiltrate deep into the layer of ground waters and pollute the
groundwater as well as the surface water. Heavy metals in the soil subsequently
enter the human food web through plants and they constitute risk to the
ecosystem as they tend to bio-accumulate and can be transferred from one food
chain to another. Heavy metals are discovered in various food chains where the
results are usually detrimental to microorganisms, plants, animals and humans
alike (10).
The main threats to human health from heavy
metals are related with exposure to lead, cadmium, mercury and arsenic (arsenic
is a metalloid but is usually classified as a heavy metal). Heavy metals have
been utilised by humans for thousands of years. Exposure to heavy metals
continues although several adverse health effects of heavy metals have been
known for a long time. For example, mercury is still used in gold mining in
many parts of Latin America. Arsenic is still common in wood preservatives, and
tetraethyl lead remains a common additive to petrol, although this use has
decreased dramatically in the developed countries. Waste-derived fuels are
especially prone to contain heavy metals which should be a central concern in
the consideration for their use. Since the mid 19th century, production of
heavy metals increased abruptly for more than 100 years, with associated
emissions to the environment, particularly in less developed countries though
emissions have lessened in most developed countries over the last century (10).
Some heavy metals are dangerous to health or
to the environment (e.g. mercury, cadmium, lead, chromium), some may cause
corrosion (e.g. zinc, lead), some are harmful in other ways (e.g. arsenic may
pollute catalysts). Some of these elements are actually necessary for humans in
minute amounts (cobalt, copper, chromium, manganese, nickel) while others are
carcinogenic or toxic, affecting, among others, the central nervous system
(manganese, mercury, lead, arsenic), the kidneys or liver (mercury, lead,
cadmium, copper) or skin, bones, or teeth (nickel, cadmium, copper, chromium).
One of the largest problems associated with the persistence of heavy metals is
the potential for bioaccumulation and biomagnification causing heavier exposure
for some organisms than is present in the environment alone. Through
precipitation of their compounds or by ion exchange into soils and muds, heavy
metal pollutants can localize and lay dormant. Unlike organic pollutants, heavy
metals do not decay and thus pose a different kind of challenge for remediation
(10).
The objective of this study was to examine
the impact of oil spill on the heavy metal content of soil
MATERIAL AND METHOD
Description of Study Area and Soil Sampling
Soil
samples were collected with a soil auger at surface depth (0-15cm) and
subsurface depth (15 – 30cm) from five (5) petroleum hydrocarbon polluted sites
(A, B, C, D, E) in Ebudu community, eleme Local Government Area of River State
in southern Nigeria. The community is one of the communities crossed by oil
pipelines in the Niger Delta area of Nigeria. A background sample or the
control sample (F) was similarly collected 500m away from the oil pipeline area
in the community, against the direction of drainage. Soil samples were air
dried, crushed and passed through a 2 mm sieve. Samples were digested using
4-acid digestion method for total metal, in line with the USEPA (2007)
3050/305, as in EPA document SW-846. The SOLAAR UNICAM 969 atomic absorption
spectrometer (AAS) was used for the metal analysis (5,19).
Data were analyzed using descriptive
statistics and Analysis of Variance (ANOVA). Test of significance of the means
was by the Least Significant Difference (LSD).
RESULT AND DISCUSSION
The
concentration of the different heavy metals determined in the six soil samples
at different surface depths are given in Table 1a. All petroleum hydrocarbon
contaminated soil samples were found to have reasonably higher concentration of
the heavy metals than the values of the controlled soil sample collected some
distance away from the site, with the concentrations of the elements within the
regulatory limits as defined by U.S. EPA, 1993. The presence of metals in the
uncontaminated soil indicates that heavy metals naturally occur in the environment
and natural ecosystem (21). This further shows that they are natural components
of the ecological system associated with one or more functions which may not be
harmful at reduced concentrations but could become toxic at heightened
doses.This finding is in harmony with
prior reports of Hopkins (9). Heavy metal building in soils polluted with crude
oil and its various products has been previously reported by Chen et al. (6), Agbogidi and Egbuchua (3), Chukwuma et al.(7),
Tables 1a, 2a and 3a shows that Fe, Pb, Zn,
Mn and Cu are more enhanced (P<0.05) in the oil - spill
– polluted soils, especially at surface depth but below the regulatory limits
defined by US EPA 1993. This may be attributed to the fact that metal profiles
in polluted soils penetrate a little below the 10-cm region, even after many
years, thereby making the metal concentration in surface soils usually higher
(18). Nwachukwu et al., (7) similarly
reported high values of Fe, Pb, Mn and Cu in an oil polluted soil. The high
value of Fe may be attributed to the fact that most soils are Fe- rich in
nature (17).
Heavy metals have also been shown to affect
the physical, chemical, biological and microbial properties of soils (7,14).Long term exposure may result in slowly
progressing physical, muscular and neurological degenerative processes (13). The presence of these heavy metals in
soils when absorbed by plants is capable of making plants potentially toxic and
harmful to man as well as his livestock if ingested or consumed as food (3,20).As trace elements, some of the heavy metals
like zinc, copper selenium are essential for the maintenance of body
metabolism.At higher concentration,
they can lead to poisoning.Lead,
chromium, nickel are known to have serious consequences on the brain cells
(8,11). Benson and Ebong (2005) noted that poor growth of crop plants in higher
levels of oil treatment was primarily due to the toxic effect of heavy metals
or mineral uptake.
InTables 1b, 2b and 3b, total contents of the heavy metals at different
surface depths and irrespective of the surface depths, were significantly
correlated, suggesting common origin of these elements in the soils (oil
pollution and anthropogenic) (17).
Table 1a: Heavy Metal Concentration (mg/kg)
in Soil Samples at the Different Surface Depth
Cu
Mn
Zn
Fe
Pb
Cd
Cr
Ni
Hg
As
A
0-15cm
9.6
12.24
19.08
23
21.05
6.2
5.98
7.23
4.18
4.42
15-30cm
5.32
9.61
11.84
14.25
13.09
3.09
3.06
4.42
1.82
2.32
B
0-15cm
8.8
13.2
20.02
24.3
22
7.5
6.01
6.4
4.12
4.08
15-30cm
4.96
9.84
11.98
15.26
12.23
4.08
4.48
3.89
2.26
2.2
C
0-15cm
9.2
14.43
18.04
21.6
20.01
6.24
5.24
6.18
3.11
4.02
15-30cm
4.84
8.92
10.82
12.63
11.92
3.67
3.76
4.52
1.88
2.26
D
0-15cm
9.78
13.62
21.71
22.3
22.3
7.02
6.38
7.26
3.37
3.35
15-30cm
4.84
8.45
12.38
14.33
11.58
3.73
3.35
4.28
1.97
1.97
E
0-15cm
4.57
6.63
7.43
9.3
7.48
3.08
3.12
4.16
2.23
1.83
15-30cm
2.68
3.42
4.72
6.64
4.81
1.87
1.07
2.05
1.07
1
F
0-15cm
3.89
6.53
6.36
9.28
6.98
3.66
3.31
3.92
1.98
1.98
15-30cm
1.84
3.64
3.38
6.86
4.57
1.76
1.08
2.02
1
1
Table 1b: Correlation of Heavy Metal
Concentration Irrespective of the Surface Depth and Area
Cu
Mn
Zn
Fe
Pb
Cd
Cr
Ni
Hg
As
Cu
1
Mn
0.4195
1
Zn
0.9724
0.4740
1
Fe
0.9661
0.5372
0.9859
1
Pb
0.9780
0.4999
0.9931
0.9921
1
Cd
0.9562
0.5901
0.9530
0.9600
0.9568
1
Cr
0.9455
0.4544
0.9478
0.9435
0.9425
0.9632
1
Ni
0.9778
0.3890
0.9527
0.9369
0.9538
0.9402
0.9595
1
Hg
0.9381
0.5764
0.9046
0.9323
0.9164
0.9497
0.9390
0.9376
1
As
0.9630
0.4973
0.9239
0.9575
0.9506
0.9375
0.9235
0.9455
0.9573
1
Table 2a: Heavy Metal Concentration (mg/kg) in
Soil Samples at Surface Depth 0 – 15cm
Table 3a: Heavy Metal Concentration (mg/kg)
in Soil Samples at Surface Depth 15-30cm
Cu
Mn
Zn
Fe
Pb
Cd
Cr
Ni
As
Hg
A
5.32
9.61
11.84
14.25
13.09
3.09
3.06
4.42
2.23
1.82
B
4.96
9.84
11.98
15.26
12.23
4.08
4.48
3.89
2.2
2.26
C
4.84
8.92
10.82
12.63
11.92
3.67
3.76
4.52
2.26
1.88
D
4.84
8.45
12.38
14.33
11.58
3.73
3.35
4.28
1.97
1.97
E
2.68
3.42
4.72
6.64
4.81
1.87
1.07
2.05
1
1.07
F
1.84
3.64
3.38
6.86
4.57
1.76
1.08
2.02
1
1
Table 3b: Correlation of Heavy Metal
Concentrations at Surface Depth 15 – 30cm
Cu
Mn
Zn
Fe
Pb
Cd
Cr
Ni
Hg
As
Cu
1
Mn
0.9699
1
Zn
0.9836
0.9694
1
Fe
0.9558
0.9806
0.9835
1
Pb
0.9859
0.9930
0.9794
0.9732
1
Cd
0.9007
0.9315
0.9418
0.9446
0.9121
1
Cr
0.8995
0.9514
0.9232
0.9424
0.9213
0.9861
1
Ni
0.9632
0.9544
0.9580
0.9254
0.9772
0.8904
0.8805
1
Hg
0.9270
0.9596
0.9593
0.9755
0.9375
0.9868
0.9866
0.8875
1
As
0.9721
0.9900
0.9533
0.9482
0.9926
0.9027
0.9259
0.9739
0.9230
1
CONCLUSION
The
present study investigated the heavy metal contents of five different sites in
soil contaminated with petroleum hydrocarbon in Ebudu community, River State,
Nigeria.The result indicated that
petroleum hydrocarbon contamination and anthropogenic activities has a
significant effect of increasing the concentrations of heavy metals including
iron, lead, manganese, zinc and copper when compared with the uncontaminated
soil sample. The study also showed that heavy metal contents are more enhanced
at the surface depth (0 – 15cm) at all the different sites investigated
REFERENCES
(1)Abioye, P. O. (2011). Biological Remediation
of Hydrocarbon and Heavy Metals Contaminated Soil, Soil Contamination, MSc
Simone Pascucci (Ed.), ISBN: 978-953-307-647-8.
(2)Aboribo R.I., (2001) Oil Politics and the
Niger Delta Development Commission, The tussle for control and domination, Afr. J. Environ. Studies, 2,168-175
(3)
Agbogidi, O. M. (2010) Metal contents of Rhizophoraracemosa (G.F.W. Meyer)
seedlings grown in crude oil contaminated soils. Obeche Journal, 28 (2):112– 118.
(4)
Amadi, A., Abbey, S. D. and Nma, A. 1996. Chronic effects of oil spill on soil
properties and micro flora of rainforest ecosystem in Nigeria. Water Air Soil Pollution, 86: 1 – 11.
(5)
Barabara, F.; Stephen, K.; William, W., (2002). Speciation and character of
heavy metals contaminate soil using computercontrolled scan electron
microscope. Environ. Forensic, 3 (2),
131-143.
(6)
Chen, H.M., Zheng, C.R., Tu, C., Shen, Z.G. (2000). Chemical methods and
phytoremediation of soil contaminated with heavy metals. Chemosphere, 41:229 –234.
(7)
Chukwuma, M. C., Eshett, E. T., Onweremadu, E. U. and Okorie, M. A. (2010) Zinc
availability in relation to selected soil properties in a crude oil polluted
eutrictropofluvent. International Journal
of Environmental Science and Technology, 7 (2): 261 – 270.
(8)
Edet, E.A., Etim, D.E. and Wilson, L.A. (2008) Assessment of heavy metals in
soil polluted with used engine oil. In: Ezike, K. N. N., Osakwe, I. I., Ekwu,
L.G., Utobo, E. and Mba, C. N. (eds.) Proceedings of the 42ndAnnual
Conference of the Agricultural Society of Nigeria held in Abakaliki, Ebonyi
State, between 19th and 23rd of October, 2008. Pp. 370 – 373.
(9)
Hopkins, S. (1996) Trace metals in plants nutrition. Journal of Food Chemical and Analysis 6:223 – 224.
(10)
Kvenvolden, K.A., Cooper, C.K. (2003) Natural seepage of crude oil into the
marine environment. Geo-Marine Letters,
23(3-4): 140 – 146.
(11)
Laskiwaski, W. M. (1996) Environmental pollution and the roles of metals. Journals of Environmental Science 9(3):
289 – 297.
(12)
Małachowska-Jutsz, A., Mrozowska, J., Kozielska, M. and Miksch, K. 1997.
Aktywność enzymatyczna w glebie skażonej związkami
ropopochodnymi w procesie jej detoksykacji. Biotechnology,
36: 79 – 91.
(13)
Merrill, J. C., Merton, J. J. P. and Solieau, S. D. (2009) Metals. In: Hayes,
W. A.(ed.) Principles and methods of toxicology.4thed. Taylor and Francis,
Philadelphia.Pp.649 – 683.
(14)
Nabulo, G., Origa, H. O. Nasinyama, G. W. and Cole, D. (2008) Assessment of Zn,
Cu, Pb, and Ni contamination in wetland soils and plants in the Lake basin. International Journal of Environmental of
Science and Technology 5(1): 65 – 74.
(15)
Nwachukwu, J. J., Oluwole, A. F., Asubiojo, O. I., Filby, R. H., Grimm, C. A.
and Fitzgerald, S. 1995. A geochemical evaluation of Niger Delta crude oils. In
Oti, M.N. and Postma, G. (Eds.), Geology of Deltas. Brookfield VT, USA, 287 –
300.
(16) Omubo-Pepple, V. B.,
Tamunobereton-ari, I. and E.D. Uko, E. D. (2011). Heavy Metal Speciation in
Contaminated Soils of an Abandoned Hydrocarbon Exploration Field Camp and
Workshop Site in Part of the Niger Delta, Nigeria. J. Basic. Appl. Sci. Res., 1(6)456-463
(17) Osuji L. C. andOnojake C. M.(2004).
Trace heavy metals associated with crude oil: a case study of Ebocha-8
oil-spill-polluted site in Niger Delta, Nigeria. Chem Biodivers.1(11):1708-15.
(18) Pardo, M. T., (2002). Sorption of lead,
copper, zinc and cadmium by soils, effects of nitriloacetic acid on metal
retention. Soil Sci. plant Anal., 31
(1-2), 31-40
(19)
Ross, S. (2004) Toxic metals in soil plant systems. JohnWiley and Sons.
Chichester.
(20)
Salihu, S. O., Dauda, B. E. N., Paiko, Y. B., Ocheni, C.and Kolo, M. T. (2012)
Metal ions in Carica papaya fruits from farms around a mechanic site in
Ketaran-Gwari, Minna, Niger State. Biological
and Environmental Science Journal for the Tropics 9(2): 159 – 163.
(21)
U.S. EPA. 1993. Clean Water Act, sec. 503, vol. 58, no. 32. (U.S. Environmental
Protection Agency Washington, D.C.).
Cite this
Article:Nwadiogbu, JO; Ikelle, II;
Onwuka, JC; Ikeh, OA; Nwankwo, NV; Anarado, IL (2024). Assessment of Heavy
Metals in a Soil Contaminated by Petroleum Hydrocarbons at Ebudu, Rivers
State, Nigeria. Greener Journal of
Environmental Management and Public Safety, 12(1): 10-15.
