EFFECTS OF PETROLEUM LEVEL (WASTE OIL) ON SOIL FERTILITY IN THE VICINITY OF A MECHANIC WORKSHOP
ABSTRACT
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
INTRODUCTION
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