Effects Of Petroleum Level (Waste Oil) On Soil Fertility In The Vicinity Of A Mechanic Workshop

Project and Seminar Material for Petroleum Engineering

Effects Of Petroleum Level (Waste Oil) On Soil Fertility In The Vicinity Of A Mechanic Workshop


This study examined the effect of petroleum level (waste oil) on soil fertility in the vicinity of a mechanic workshop. This study was carried out in Nekede automobile mechanic village in Southeastern Nigeria. Sample plots were established in a randomized method along a transect at 100m interval for five (5) different locations within the study area, these sample points were constantly receiving spent engine oil (SEO) and were labeled treatment SA, SB, SC, SD, SE. A composite soil sample was drawn from depths of 0 – 15cm and 15 – 30cm for each of the five treatments. These were air dried, passed through a 2mm sieve and properly labeled for laboratory analysis. Soil samples were then analysed for heavy metal (Pb) using Atomic Absorption Spectrophotometer (AAS). Two (2) soil samples were collected at each sample point and two (2) soil samples CF and CG were also collected 2 km away from the study area in an undisturbed forest as control. Soil pH, cation exchange capacity (CEC) and particle size distribution were also determined. Results showed that the concentrations of Pb from soil samples were random across sample point. The concentration of Pb in the contaminated soil at a depth of 0 – 15cm (topsoil) varies, the highest value was observed at SD (482.2mg/kg) and the lowest value at SE (146.8mg/kg). At the depth of 15 – 30cm (subsoil) concentration of Pb is highest at SB (397.6mg/kg) and lowest at SC (140.1mg/kg). The mean concentration of Pb in the contaminated soil sample has its highest concentration at SB (382.9mg/kg) and lowest at SC (157.8mg/kg). The level of Pb in the control site was lower (CF, 46.5mg/kg and CG, 11.8mg/kg) when compared to the various concentrations of the contaminated soil. pH range was between 5.43 and 6.79. CEC varied across the sample area and showed no variation within the control site. The highest value was observed at CF and CG (3.65cmol/kg) respectively while the lowest value was observed at SA (2.15cmol/kg). The % sand distribution varied across the sample point and showed a higher distribution in the study area than % clay and % silt, the soil texture (sandy loam) was not significantly affected by the SEO. The study concluded that improper disposal of SEO in the study area elevated the soil Pb content thereby causing Lead pollution.

Chapter One


1.1 Background of the study

Used motor oil is a very dangerous polluting product. It contains PAH’s and high levels of metals. PAH’s such as benzo[a]pyrene, are well known for their high carcinogenity. Considerable quantities of heavy metals such as Pb, Zn, Cu, Cr, Ni, and Cd are contained in used crankcase oil, these metals are highly toxic to organisms In Nigeria, it is common among motor mechanics to dispose waste oils into gutters, water drains and soil (Okonokhua et al., 2007). Waste oils is defined as used lubricating oils obtained after servicing and subsequently draining from automobile and generator engines. Spent oils contain high percentage of aromatic and aliphatic hydrocarbons, nitrogen and sulphur compounds and metals (magnesium, calcium, zinc, lead) than fresh oils, these metals are introduced into the oil as a result of wear and tear of the engine (Mohd et al., 2011) (Mohd. Mozamil Bhat; Shiv Shsankar, Shikha, Mohammad Yunus and Shukai R. N (2011): Remediation of hydrocarbon contaminated soil through microbial degradation – FTIR based prediction. Advances in Applied Science Research 2(2): 321 – 326).

As engine oil is used in automobile, it picks up a number of additional compounds from engine wear. These include iron, steel, copper, zinc, lead, barium, cadmium, sulfur, dirt and ash. Because of the additives and contaminants, used motor oil disposal can be more environmentally damaging than crude oil pollution (Abioye et al 2012). These additives and contaminants may cause both short- and long-term effect if they are allowed to enter the environment through water ways or soil (Anoliefo and Vwioko, 2001). Once engine oil is drained off an engine, it is no longer clean because it has picked up materials, dirt particles, and other chemicals during engine operation, thus such lubricating oil is now classified as SEO.

Spent oil sometimes referred to as waste engine oil is produced from automobile mechanic shops and mechanical or electrical engine repairers’ shops (Anoliefo and Vwioko, 2001) after servicing the vehicles engines, generating set and other types of engines. It has dark brown to black colour and it is harmful to the soil environment (Adedokun and Ataga, 2007). This is because it contains a mixture of different chemicals including low to high molecular weight (C15-C21) compounds, lubricants, additives and decomposition products and heavy metals which have been found to be harmful to the soil and human health (Duffus, 2002).

According to Ekundayo et al. (1989), marked change in properties occurs in the physical, chemical and microbiological properties of soils contaminated with lubricant oil. Oil displaces air and water leading to anaerobic condition (Atlas, 1977). The presence of spent lubricant oil in soil increases bulk density, decreases water holding capacity and aeration propensity (Kayode et al., 2009). The authors also noted reduced nitrogen, phosphorus, potassium, magnesium, calcium, sodium and increased levels of heavy metals in soils contaminated with spent oil. In contrast, Vwioko et al. (2006) noted buildup of essential elements such as organic carbon and organic matter and their eventual translocation to plant tissues.

There are relatively large amounts of hydrocarbons in the used oil, including the highly toxic polycyclic aromatic hydrocarbons (Wang et al., 2000). Also, most heavy metals such as V, Pb, Al, Ni and Fe, which were below detection in unused lubricating oil, have been reported by Whisman et al. (1974) to give high values (ppm) in used oil. These heavy metals may be retained in soils in the form of oxides, hydroxides, carbonates, exchangeable cations, and/or bound to organic matter in the soil (Yong, et al., 1992). Nevertheless, this is dependent on the local environmental conditions and on the kind of soil constituents present in the soil-water system.

The increase in the number of vehicles in Nigeria has necessitated a higher production and use of SEO. This has subsequently given rise to the generation of large quantities of SEO, at the time of servicing the vehicles. This SEO is considered as ordinary waste by majority of the workers of the automobile mechanic workshops in Nigeria, who dispose this oil by dumping on surface soil. This practice of disposal is a continuous exercise, except when the SEO is collected by unregistered and unregulated vendors.

Nekede Mechanic Village was selected as the study area. It was established in 1975 by the Imo State Government of Nigeria, went into full operation in 1984 and has been in use with constant growth since then. Udebuani et al (2010) reported that the quantity of SEO generated in this area is estimated at about an average of four thousand seven hundred and ten (4710) litres per week. The study area covers an area of about 3600m2 with a population of about five thousand workers. These workers are mainly motor mechanics which constitute about 60% of the total workforce and includes panel-beaters, welders, automobile electricians, painters, automobile upholstery workers, automobile spare part dealers, vulcanizers and blacksmiths.

Complimentary service workers found in the area include confectionaries, commercial phone call service operators, textile dealers, audio and video cassette retailers etc. Most of these artisans and vendors belong to the informal sector of the economy. They neither pay tax, nor register with the government. Their level of education ranges between first school leaving certificate and the senior secondary school certificate, this partly explains the difficulty of controlling their method of disposal of SEO in the area. With increasing number of automobile mechanic workshop from about 25 in 1985 to about 160 in 2007 and many more workshops under construction as evident at the Nekede Mechanic Village and the increasing number of vehicles being serviced or repaired at these mechanic workshop from an average of 3 vehicles per workshop per day in 1985 to an average of 10 vehicles per workshop per day in 2007, it can therefore be established that the amount of SEO from vehicles in Nigeria in general and Owerri in particular is on a steady increase.

This study therefore attempts to assess the effect of SEO on receiving soil with particular interest on the level of heavy metal (Pb) contamination on these soils.

1.2 Statement of the problem

Previous studies on crude oil pollution in soil had revealed its adverse effects on soil productivity. These studies had been majorly on the effects of pollution on chemical properties of the soil. There is therefore a need for continuous research on the problems associated with pollution resulting from spillage and the effects on the soil environment which has a negative impact on crops grown on it.

As a result of crude oil pollution, soil physical properties such as pore spaces might be clogged which reduces soil aeration, infiltration of water into the soil, increased bulk density of the soil which may affect plant growth. Crude oil which is denser than water may reduce and restrict permeability. Some of the effects of crude oil may have adverse effects on soil physical properties include decreased pore spaces, saturated hydraulic conductivity and increased bulk density. All these possibilities deserve empirical studies to establish their reality or otherwise.

Leaching of pollutants through soil due to their vertical movement in the soil and eventual contamination of groundwater is an environmental concern. Some heavy metals contained in these effluents from the automobile and related industries have been reported to be carcinogenic (Tamburlini, G., Ehrenstein, O. V. and Bertollini, R., 2002).

Therefore, this particular study had its main objective to examine the effects of crude oil pollution on soil physical properties.

1.3 Objectives of the study

The main objective of this study is to examine the effects of petroleum level (waste oil) on soil fertility in the vicinity of a mechanic workshop.

The following are the specific objectives of this study:

  1. To examine the effect of waste oil on Physico-Chemical Properties in Soil
  2. To examine the effect of waste oil on Pb in Soil
  3. To examine the effect of waste oil on Soil pH, Particle Size Distribution and CEC

1.4 Justification of the study

These findings have provided a stimulus for studies of known and suspected areas of SEO contamination. It is therefore necessary to assess the extent of heavy metal contamination resulting from the dumping of SEO. Such information provides a perspective when considering what level of heavy metals in soil will be defined as hazardous and would suggest the extent of remediation needed.

The activity of heavy metals in soil matrix and is dependent on the chemical species of the metals present. Thus, the knowledge of the chemical speciation of heavy metals provides information on the bioavailability and toxicity of such metals (Abdu, 2010). The data on the effects of oil waste on soil chemical indicators and micro pollutants in the soil of Nekede is lacking or under reported. This research that was designed to provide such baseline data which would provide information that will ascertain the contamination problems associated with oil waste effluents that may confront the inhabitants surrounding oil wastes and may be used for appropriate protection remedies.

1.5 Scope of the study

The study is carried out on the effects of petroleum level (waste oil) on soil fertility in the vicinity of a mechanic workshop. This study was carried out in Nekede Mechanic Village, Imo State Government of Nigeria.

Chapter Five


The result from this study shows that pH values of the contaminated soil around Nekede mechanic village are predominantly acidic. The research also shows that CEC is relatively low which implies low fertility of the soil. Particle size analysis shows that the soil is predominantly sandy. The soil in the study area shows varying level of Pb contamination, the highest concentration of lead in the study area exceeded the permissible level (limits). Based on these findings, a well coordinated waste oil collection programme should be initiated by the government in partnership with the private sector, to minimize disposal of waste oil on soil. The collected waste oil should be sent to motor oil manufactures for recycling and re-injection into the production stream. Health, Safety and Environmental workshops and seminars should be organized for the populace, especially for enlightenment of people who directly engage in activities generating SEO. There should be periodic monitoring of the contaminated areas to ascertain that pollution do not exceed permissible limits. Certain plants found in the environment which are capable of decomposing the organic constituents of SEO should be planted within the contaminated areas to help break down the complex molecules of SEO (phytoremediation).

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