INTRODUCTION
Soil ecosystem is an
essential component of life and man depends on it for food and natural
resources while plants depend on it for their growth. It is also a medium for
the biochemical cycling of soil nutrients (Adewole and Uchegbu 2010). Soil is a vital natural resource and must be well
managed for sustainable agricultural production (Benton, 2003). Managing soil
resources for food security and sustainable environment is quite apt and
deserves great attention; considering the increasing pressure on our soils due
largely to population increase and intensive agricultural production (Ogeh and
Ukodo, 2012).
Pollution of the soil
ecosystem is a major source of soil degradation (Mbagwu, 2008). Study by Kayode
et al., (2009) opined that soil pollution with crude oil and spent lubricating
oil destroys soil structure, increased bulk density, soil porosity reduction in
soil capillary, aeration and nutrients availability and uptake by plants.
Spent engine oil (SEO)
is waste lubricating oil collected from automobile workshops, garages and
industrial sources like hydraulics oil, turbine oil, process oil and metal
working fluids (Olugboji et al., 2008). Spent engine oils are mixtures of
different chemicals including petroleum hydrocarbons, chlorinated biphenyls,
chlorodibenzofuran, lubricant additives, decomposition products and heavy metal
that are from engine parts as they wear away (Wang et al., 2000).
Different
petroleum products are common soil contaminants and often contained hazardous
chemicals especially the polycyclic aromatic hydrocarbon (Sharifi et al.,
2007). There are relatively large amounts of hydrocarbons in used oil including
the highly toxic polycyclic aromatic hydrocarbons (Okonokhua et al., 2007)
In
Nigeria, increased automobile repairs activities have contributed markedly to
the problems of soil contamination (Mba et al., 2009). The automobile
activities usually involve changing of lubricating oil, servicing and greasing
of motor parts and replacement of worn-out parts (Ajayi, 2005). This result in
the disposal of spent lubricating oil and other wastes used in cleansing during
auto-mobile servicing on the soil. Contamination of soil with toxic substances
can degrade its capacity to provide habitat for soil organism and to grow
plants that are safe to eat (Brady and Weil, 1999).
Port
Harcourt is a city in South-South a major oil producing area of Southern
Nigeria. In the area, automobile mechanics abound and spread SEO on agricultural
land rendering the land uncultivable. With the teeming population of Nigeria,
it has become essential to investigate the effect of SEO on agricultural land. This
study aims to evaluate the effects of SEO on properties of soil grown with
vetiver.
MATERIALS AND METHODS
The
experiment was conducted at the University of Port Harcourt Teaching and
Research farm, department of crop and soil science. The area is situated between latitude 40
54' and longitude 60 55' East of the equator on an elevation
of 20 meters above sea level. Annual
rainfall distribution ranges from 3000 to 4000mm (FAO, 1984). Annual temperature varies from 22 to 310C
(FDRD, 1981). The relative humidity (RH) varies between 35 to 90% depending on
the particular period of the year.
Location for Soil
Sample Collection
Soil
samples used for the study were collected from Elikohia mechanic workshop (site
1) and Choba mechanic workshop (site 2).
Composite samples of spent oil contaminated soils were collected
randomly from the two sites at a depth of 0-15, 15-30 and 0-45cm respectively
and uncontaminated samples (control) at 100 meters away from the two sites with
shovel.
Soil Sample
Preparation and Planting of Vetiver Grass
The
experiment was carried out using perforated plastic pots. Ten (10kg) each of harmonized composite soil
samples of depths 0-15, 15-30 and 30-45cm of contaminated and no vetiver (ctm
no vet), contaminated and remediated with vetiver (ctm + vet) and control
samples were placed into 10 litre perforated plastic buckets. The experiment was replicated thrice giving a
total of 54 pots.
The
pots were watered thrice weekly with 200mls of water through a watering
can. Two weeks later, vetiver grass (Vetiveria zizanioides) rhizomes obtained
from National Root Research Institute, Umudike, Abia State, Nigeria were
transplanted, 2 seedlings per pot.
Emerging weeds were removed by hand pulling. The experiment was a ‘3×2 ×3’ factorial
fitted into a completely randomized design (CRD) consisting of three depths,
three treatments, two sites replicated thrice making a total of 54 pots. The experiment was left for a period of
twelve weeks.
Soil Sampling and
Data Collection
Composite
soil samples uncontaminated (control), contaminated and no vetiver and contaminated
and remediated with vetiver were collected from each of the pots, labelled and
air dried at room temperature in the laboratory. The samples were pulverized with mortar and
pestle, sieved in a 2mm mesh screen and sent to the laboratory for the
determination of the selected parameters. Samples were collected before and
after the experiment.
Laboratory Analysis
PH
1:1 soil water ratio using pH meter with glass electrode (McLean, 1982).
Electrical Conductivity (EC) – 1:2.5 soil water ratio using Conductivity Bridge
(Rhodes 1996). Organic Carbon (OC) – Dichromate wet oxidation method Nelson and
Nelson, (1986). Total Nitrogen (TN) by micro Khejahl digestion and distillation
method (Brenner, 1996). Available Phosphorus – Bray P1 method (Bray and Kurtz,
2003).
Statistical Analysis
The
data were analysed using the analysis of variance (ANOVA) technique and the
Duncan’s multiple range test was used to compare the means (Alika, 1997)
RESULTS AND
DISCUSSIONS
Results
of the study as presented in table 1 above showed that the contaminated soils
were darker than the control.
Dark
soils absorb more heat than light ones. Donahue et al., (1990) reported that
some black coal mining wastes and dark coloured oil-shale residues reached
temperatures of 65 oC – 70 oC, which are lethal to many
plants that would otherwise grow in those soils. Soils polluted with waste-oil
result in the soil remaining unsuitable for crop growth and depending on the
degree of contamination, type of soil and soil environment, the soil may remain
unsuitable for crop growth for
months or years until the oil is degraded to tolerable levels (Atuanya, 1987).
pH
Soil
pH is a major factor influencing the availability of elements in the soil for
plant uptake (Marschner, 1995). The soil pH as shown in table 1 above ranged
from 5.8 to 6.4. There is no significant (P > 0.05) different in soil pH in
control (6.20) samples between the two sites (Choba and Elikohia). The study
revealed that the soil pH increases with depth of the soil profile. There is no
significant difference observed in soil pH between control and contaminated
samples indicating that spent engine oil has no serious negative impact on soil
pH. This agrees with the findings of Okonokhua et al., 2007 who inferred that
soil contaminated with spent engine oil had no effect on the pH of the soil. However,
the pH of the contaminated samples (ctm no vet) were slightly higher than the
control samples. Remediation of the SEO
contaminated soil with vetiver (ctm+vet) increased slightly the pH of the soil. Generally, the soils were slightly acidic.
Total Nitrogen
Total
nitrogen (TN) in the soil increases from 0.045 % to 0.16 % and 0.048 % to 0.16 %
in Choba and Elikohia sites respectively. Significant (P < 0.05) difference
was observed between the soil contaminated with no vetiver (ctm no vet) and
control in both sites (Choba and Elikohia) in all the depths indicating that
contamination of the soil with spent motor oil increased the % total nitrogen
in the soil. This corroborates with the reports of (Chukwumati and Abam, 2021;
Nwite and Alu, 2015) who reported significant higher total nitrogen in spent
oil contaminated soil over control. There is no significant (P > 0.05)
difference between the two sites (Choba and Elikohia) in the study investigated,
though % TN was slightly higher in Elikohia than Choba.
Generally,
percentage total nitrogen was low both in contaminated and uncontaminated
samples respectively. The low levels of nitrogen in the study sites is typical
of the highly weathered soils of the humid tropics and may be attributed to
high nitrogen losses through leaching resulting from high rainfall (Brady and
Weil, 1999). The study also revealed that total nitrogen decreases as you go
down the profile.
Phosphorus (P)
Available
phosphorus of the spent engine oil contaminated soils with no vetiver (ctm no
vet) were significantly (P < 0.05) reduced compared to control soils. The
values of available phosphorus in the studied areas decrease from 43.43mg/kg to
9.43mg/kg in Choba site and 45.30mg/kg to 9.87mg/kg in Elikohia sites. The observed decrease in available phosphorus in
contaminated soils conform to the report of Ihem et al., (2015) who inferred
that crude oil pollution encourage nutrients element in balance as well as
phosphorus fixation among other elements.
The
result also agrees with the finding of Uquetan et al., (2017) who related the
decrease to the conversion of H2P04- (most
available form for plant uptake) to HPO42- (less
available form) as a result of the adjustment in soil pH in the polluted soils.
There is no significant difference in available P between the two site
locations. The result indicates that
spent oil contamination of soils significantly affects negatively availability
of phosphorus in the soil as well as its uptake in plants.
Remediation
of the contaminated soils with vetiver grass (ctm + vet) significantly (P < 0.05)
increase the concentration of available phosphorus in the soil possibly due to the
ability of vetiver grass to establishing symbiotic association with soil
microbes in its rhizosphere. This corroborates with Chukwumati and Abam, (2021)
who reported an increase in available phosphorus due to remediation of crude
oil contaminated soil with vetiver grass. Khan, (2005) and Sunanthaposuk,
(2000), reported that vetiver grass has the potential of establishing a strong
symbiotic association with wide range of soil microbes in the rhizosphere that
provide nutrients (nitrogen fixing bacteria, phosphate solubilising bacteria
and fungi (mycorrhizal fungi) for plant growth.
Percentage Organic
Carbon
Percentage
carbon (organic and inorganic) represent the extent of hydrocarbon in the soil.
The greater the carbon content, the higher the level of organic pollutants
present Mansur et al., (2003). The organic carbon (OC) content increases from
0.86 % in control to 3.62 % in contaminated soil with no vetiver in Choba site
and 0.95 to 3.78 % at Elikohia for control and contaminated with no vetiver
respectively. (Table 1).
A
significant (P < 0.05) difference was observed in total organic carbon
between spent oil contaminated soil with no vetiver (3.62 %) and control (1.18 %)
in Choba site. Similar trend was also observed between contaminated no vetiver
and control in Elikohia site. This implies that contamination of the soil with
spent engine increased the percentage total organic carbon over uncontaminated
(control) samples. This finding agrees with the work of Chukwumati, et al.,
(2019), Chukwu, and Udoh, (2014) who reported higher percentage of organic
carbon in crude oil contaminated soil over control.
The
increase in total organic carbon in contaminated over control samples could
possibly be as a result of the carbon substrate which may have being added into
the soil by spent automobile oil/spent engine oil. Ihem et al., (2015)
attributed it to high mineralization process in the organic content of the soil.
Similar finding was reported by Okonokhua et al., (2007). This was in contrast
to the observation of Kayode et al., (2009) who adduced a reduction in nitrogen
content in soil treated with spent lubricant oil.
It
is worthy to note that the increased values of OC and TN contents of the
contaminated soils compared to the control (Table 1) could also be attributed
to the application of the SEO to soil. Crude oil, from which the engine oil is
produced, contains principal elements such as oxygen, nitrogen and sulphur
other than hydrogen and carbon (Selley, 1998). The increase in percentage total
organic carbon and total nitrogen in spent engine oil contamination of soil may
also implies that spent lubricant oil play beneficial effect in soil.
Percentage
organic carbon was observed to be slightly higher in Elikohia site than Choba,
though not significant. The increase in
concentration of organic carbon at Elikohia over Choba could possibly be due to
heavy volume of vehicle always found at the site for repairs because of its
location at the heart of the city thus leading to increase in pollutants.
Significant
(P < 0.05) differences were also seen in soil depth between the soil surface
and sub soil as you go down the profile. The high percentage total organic
carbon in the top soil over sub soil could be as a result of high concentration
of the remains of plants, animal and micro-organisms at different stages of
decomposition in surface soil. The study also revealed that remediation of the
soil with vetiver grass significantly increase percentage total organic carbon
in all the samples studied.
Electrical
Conductivity (EC)
The
electrical conductivity (EC) of the studied samples increased from 2.083 µs/g in
control to 13.67 µs/g in contaminated soil with no vetiver (cmt no vet) and
2.093 in control to 15.7 µs/g in contaminated with no vetiver (ctm no vet) for
Choba and Elikohia sites respectively; implying that contamination of the soil
with spent lubricant oil affected the ionic stability of the soil.
This
corroborates with the findings of Chukwumati and Abam, (2021) and Asuquo et
al., (2005) who reported higher electrical conductivity in crude oil
contaminated soil over control. This is in contrast to the result of Osuji and
Nwoye, (2007) whose result showed low electrical conductivity.
The
electrical conductivity of the soil decreases with depth as you go down the
soil profile in both Choba and Elikohia sites. The value of electrical
conductivity was significantly higher in Elikohia than Choba. Remediation of
the soil with vetiver grass (ctm + vet) significantly reduced the electrical
conductivity of the soil from the contaminated (ctm no vet) across all the soil
depths investigated.
Exchangeable Cations (Ca,
Mg and K).
Exchangeable
cations are the cations which can be exchanged by a cation of an added salt
solution (Thomas, 1982). The results of
this study focuses on exchangeable basic cations (Ca2+, Mg2+,
and K+). The concentration of calcium (Ca) ranged from 1.48 to 0.483
Cmol/kg in Choba site and 1.62 to 0.527 Cmol/kg in Elikohia. The content of
magnesium increased from 0.323 to 1.25 cmol/kg in Choba and 0.467 to 1.39
cmol/kg in Elikohia while potassium increased from 0.035 to 0.433 cmol/kg and
0.038 to 0.527 cmol/kg for Choba and Elikohia respectively.
Exchangeable
bases (Ca, Mg and K) investigated in this study were significantly (P < 0.05)
higher in control over spent oil contaminated (ctm no vet) soil in both sites
and in all the profile depths studied, showing that contamination of soil with
spent engine oil decreases the concentration of exchangeable bases (Ca, Mg and
K). This agrees with the finding of Chukwumati et al., (2016), Uhegbu et al.,
(2012) and Kayode et al., (2009) who reported decrease of exchangeable bases in
soil treated with spent lubricant oil.
The significant reduction in exchangeable basic cations in contaminated
over control soil samples could possibly be as a result of immobilization of
the nutrients by spent oil (Oyedele and Amoo (2014).
The
observed values of exchangeable bases in the study were below the critical
levels of Ca, Mg and K (3.8, 1.9 and 0.24 cmol/kg) for soils in Nigeria as
established by Agboola and Ayodele (1987) thus implying that the soil is low in
fertility.
A
significant (P < 0.05) difference was observed in the exchangeable basic cations
between soil contaminated and remediated with vetiver (ctm + vet) and soil
contaminated with no vetiver (ctm no vet) in both sites and within the soil
depths indicating that remediation of the soil with vetiver grass significantly
increase the exchangeable bases. The reason for the observed increase in
exchangeable basic cations in SEO contaminated soil remediated with vetiver
over over contaminated unremediated samples could be attributed to the presence
of soil micro-organisms in rhizosphere of vetiver plants growing in
contaminated soils. This corroborates with the studies of Khan, (2005) and
Sunanthaposuk, (2000) who reported that vetiver grass establishes strong
symbiotic association with wide range of soil microbes in their rhizospheres
which enables it to provide nutrients (nitrogen fixing bacteria, phosphate
solubilizing bacteria and fungi, mycorrhizal and cellulolytic fungi
phytohormones for plant growth.
CONCLUSION
The
results of this study have shown that application of spent engine oil has
deleterious effect on chemical properties of soil. All the chemical properties
of soil studied indicated severity as the levels of spent engine oil
application increased indicating that high disposal of hydrocarbon oil into the
soil poses a great danger of soil degradation and low productivity. It was
observed that available phosphorus, as well as exchangeable cations were
generally depressed due to spent engine oil application.
The
study concluded that improper disposal of SEO in the study area adversely
affected the soil chemical properties. Therefore, indiscriminate disposal of
spent engine oil should be avoided especially in cultivable areas to ensure
sustainable soil productivity.
REFERENCES
Adewole,
M.B. and Uchegbu, L. U, (2010) Properties of Soils and Plants Uptake within the
Vicinity of Selected Automobile Workshops in Ile-Ife Southwestern, Nigeria. Ethiopian
Journal of Environmental Studies and Management Vol.3 No.3.
Agboola,
A.A. and Ayodele, O. (1987). Soil test for upland rice in southwestern Nigeria.
Fertilizer Research, 14: 227-234.
Ajayi,
O.O, (2005). Heavy metal contents of soil in automobile workshop in Lagos.
Nigerian Journal of Soil Science. 15(2), 163-164.
Alika,
J. O, (1997). Statistics and Research Methods. Ambik Press, Benin City.269 pp.
Asuquo,
F. E., Ibang, I. J and Idungafa, N. (2005). Effects of quo Iboe crude oil
contamination on germination and growth of okra (Abelmoschus esculenta) and
fluted pumpkins (Telfaria occidentalis). 1(2) Retrieved from
http:/www.ecoserv.publisher.org/list. Htm#5
Atuanya, E I, (1987).
Effect of waste engine oil pollution on physical and chemical properties of
soil. A case study of waste oil contamination. Delta Soil in Bendel State. Nigeria
Journal of Applied Science. 5:155-176.
Benton, J (2003). Agronomic handbook: Management of
crops, soils, and their fertility. CRC Press LLC, 2000 N.W. Corporate Blvd., Boca
Raton, Florida 33431. P 482.
Brady,
N. C., and Well, R. R, (1999). The Nature and Properties of Soils. (12th
Edition). Prentice Hall, New Jersey.
Brenner,
J. M. (1996). Total nitrogen. In D.L.
Sparks (edn). Methods of soil analysis part 3. Chemical methods. SSSA Booke
Series 5.
Chukwu,
E. D. Udoh, B. T, (2014). Effect of crude oil and industrial wastes pollution
on some soil chemical properties in Ikot Abasi, Niger Delta Area, Nigeria.
Proceedings of the 38th Annual Conference of the Soil Science Society of
Nigeria, 83-88.
Chukwumati,
J. A and Abam, P. (2021). Influence of grasses amended with organic manures on
soil physico-chemical properties in crude oil polluted soil in Niger Delta of
Nigeria. International Journal of Scientific Engineering and Applied Science.
7(2), 188-199.
Chukwumati,
J. A, Ibanibo, G. C and Adedokun, O.M. (2019). Response of maize on crude oil
polluted soil after one month of Remediation with spent mushroom substrate.
Advances in Research. 20(4), 1-8.
Chukwumati,
J. A., Omovbude, S and Wokoma, C. N. (2016). Effect of spent engine oil on
maize (Zea mays) in South-South Nigeria. New York Science Journal 9(7), 45-52.
Donahue, R L; Miller,
R W; Shickluna, J C (1990). An Introduction to Soils and Plants Growth. Prentice-Hall
Inc., U.S.A. 667 pp.
Federal Department of
Rural Development Area. (1981). Programme Preparatory Report. Nov, 1981.
Food and Agricultural
Organization. (1984). Food and
Agricultural Organization Year Book, FAO. Rome, Italy. 4, 122-127.
Ihem, E. E., Osuji,
G. E., Onweremadu, E.U., Uzoho, S. O., Ndukwe, B. N., Osisi, A. S and Okoli, N.
H. (2015). Variability in selected
properties of crude oil polluted soil of Izombe Northern Niger Delta, Nigeria.
Agriculture, Forestry and Fisheries Special Issue. Environment Applied Science
Management in Changing Global Climate. 4(3-1), 29-33.
Kayode, J., Oyedeji,
A. A. and Olowoyo, O. (2009). Evaluation of the effect of pollution with spent
lubricating oil on the physical and chemical properties of soil. The Pacific
Journal of Science and Technology. 1(10):387-391.
Khan, A. G, (2005).
Role of soil microbes in the rhizospheres of plant growing on trace metal
contaminated soils in phytoremediation. Journal of Trace Element Medical
Biology. 18, 355-364.
Marschner,
H (1995). Mineral nutrition of higher plants (2nd edn). New York: Academic
Press.
Mbagwu,
J. S. C. 2008. Environment sustainability reversing the degradation trends in
sub- Saharan Africa. Proceedings of the 13th annual lecture symposium of the
international association of research scholars and fellow (IITA), 13th February
pp72- 83.
Mbah, C. N, Nwite J. N and Nweke I. A (2009).
Amelioration of Spent Oil Contaminated Ultisol with Organic Wastes and its
Effect on Soil Properties and Maize (Zea mays L) Yield. World Journal of Agricultural
Sciences 5 (2): 163-168.
Mclean, E. O. (1982).
Soil pH in Monogram, methods of soil analysis. Agronomy Monogram, Part 2, 9.
Nelson,
D. W and Somners, L. E. (1986). Total organic carbon and organic matter. In
page A. C (edn). Methods of soil analysis part 2. Agronomy Monogram 9. Madison
W. I. ASA and SSSA. 39-45.
Nwite,
J. N and Alu, M. O (2015). Effect of different levels of spent engine oil on
soil properties, grain yield of maize and its heavy metal in Abakaliki South
Eastern Nigeria. Journal of Soil Science and Environmental Management. 5(4),
44-51.
Ogeh, J. S and Ukodo, E. (2012). Profile distribution
of physical and chemical properties in Soils of a Toposequence in Benin
Rainforest of Nigeria. Nigerian Journal of Basic and Applied Science. 20(1),
68-72.
Okonokhua,
B. O., Ikhajiagbe B., Anoliefo, G. O and Emede, J. O (2007). The effect of
spent engine oil on soil properties and growth of maize (Zea mays L.). J. Appl.
Sci. Environ. Mgt 11(3):147-152.
Olugboji, O. A. and Ogunwale
O. A. (2008). Use of spent engine oil. AU J. T. 12(1):67-71.
Osuji,
L. C and Nwoye, I. (2007). An appraisal of the impacts of petroleum hydrocarbon
on soil fertility. The owaza experience. African Journal of Agricultural
Research. 3(7), 318-324.
Rhodes,
J. D. (1996). Salinity, electrical conductivity and total dissolves solids.
Methods of soil analysis part 3. In D. L. Sparks (edn). SSSA. Book Series, 5.
Selley, R. C (1998).
Elements of petroleum geology.Academic Press, UK.285 pp.
Sharifi,
M., Sadeghi, Y and Akbarpour, M. (2007). Germination and growth of six plant
species on contaminated soil spent engine oil. Intl. J. Environ. Sci. Tech.
4(4):463 - 470
Sunanthaposuk,
V. (2000). Study on soil microbial biodiversity in rhizospheres of vetiver
grass in degrading soil. In Abstract of Papers Proceedings of 2nd
Vetiver Conference (ICV-2). January 18-22. Phetchabieri, Thailand.
Thomas,
G. W. (1982) Methods of Soil Analysis pp. 159 – 165. In A.L. Page et al.
(eds.), Part 2, 2nd ed. Agron. Monogr. 9. ASA and SSSA, Madison, WI.
Uhegbu
F. O, Akubugwo, E. I, Iweala, E. J, Uhegbu O.C (2012). Impact of spent engine
oil on soil and the growth of Zea mays L. Seeds. Scientist. Journal of
environmental Science. Environ. Sci.1(1):1-8.
Uquetan,
U. I., Osang, J. E., Egor, A. O., Fasoka, P.A., Alozie, S. I and Bawan, A.U.
(2017). A case study of the effect of pollution on soil properties and growth
of tree crops in Cross Rivers State, Nigeria. International of Pure Applied
Physics 5(2), 12-28.
Wang J. J, C. R. Wong
C. K. & Wong P. K. (2000). Characterization of polycyclic aromatic
hydrocarbons created in lubricating oils. Water, Air, Soil Pollution.
120:381-396.
within the Vicinity of Selected Automobile
Workshops in Ile-Ife Southwestern, Nigeria. Ethiopian Journal of Environmental
Studies and Management Vol.3 No.3, pp 31 – 35.
