EFFECT OF SPENT OIL (ENGINE OIL) ON THE PHYSIOCHEMICAL PROPERTIES OF SOIL

CHAPTER ONE

INTRODUCTION

1.1      Background of the Study

Spent/used oil is any oil that has been refined from crude oil, or any synthetic oil that has been used and, as a result of that use, is contaminated by physical or chemical impurities. Examples of used oil include: used motor oil, used hydraulic fluid, used electrical insulating oil, used transmission fluid, used compressor oils, used cutting oils and used coolants. Waste oil Waste oil is defined as any petroleum-based or synthetic oil that, through contamination, has become unsuitable for its original purpose due to the presence of impurities or loss of original properties.

The difference between spent/used oil and waste oil, “used oil” as any petroleum or synthetic oil that has been used, and as a result of such use is contaminated by physical or chemical properties. “Used oil” is a precise regulatory term. “Waste oil” is a more generic term for oil that has been contaminated with substances that may or may not be hazardous. Any oil contaminated with hazardous waste may itself be a hazardous waste, and if so, must be managed subject to hazardous waste management standards. Both used oil and waste oil require proper recycling or disposal to avoid creating an environmental problem.

The disposal of spent engine oil (SEO) into gutters, water drains, open vacant plots and farms is a common practice in Nigeria especially by motor mechanics. This oil, also called spent lubricant or waste engine oil, is usually obtained after servicing and subsequently draining from automobile and generator engines and much of this oil is poured into the soil (Udom, Mbagwu, and Willie, 2018). There are relatively large amount of hydrocarbons in the used oil, including the highly toxic polycyclic aromatic hydrocarbons (Adedokun and Ataga, 2017). Also, most heavy metals such as Lead, Aluminum, and Iron, (Pb, Al, and Fe), which were below detection in unused lubricating oil, have been reported by (Udo and Fayemi, 2015) 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. Nevertheless, this is dependent on the local environmental conditions and on the kind of soil constituents present in the soil-water system. (Amadi, Samuel and Anthony, 2014) have shown that a marked change in properties occurs in soils polluted with petroleum hydrocarbons, affecting the physical, chemical and microbiological properties of the soil. Oil pollution of soil leads to build up of essential (organic C, P, Ca, Mg) and non-essential (Mg, Pb, Zn, Fe, Co, Cu) elements in soil and the eventual translocation in plant tissues. Although some heavy metals at low concentrations are essential micronutrients for plants, but at high concentrations they may cause metabolic disorders and growth inhibition for most of the plant species. However, plants respond differently to pollutants.

Okon and Udofot, (2012) reported that the contamination of soil with spent engine oil caused growth retardation in plants, with the effect more adverse for tomato (Lycopersicom esculentum) than pepper (Capsicum annum). Maize (Zea mays), a major cereal in Nigeria and many African countries, was chosen for this study because it has become increasingly popular and most farmers have adopted its cultivation. This study aims to evaluate the effects of spent engine oil on soil properties. In urban areas, various types of activities like agriculture, industry and transportation produce large amount of wastes which are classified as either agricultural, industrial, municipal or nuclear wastes.

These wastes from various sources are deposited on the soil surfaces either deliberately applied as fertilizer, sprays or pesticides (Anoliefo and Vwioko, 2015) or inadvertently through small or large leaks (Ojeniyi, 2010) as solids, plastics, crude oil or spent engine oil. Some of these wastes can be recycled into some important products that can be used to meet with the challenges arising from increasing population of Nigeria. They can be recycled into manures and fertilizers for production of crops and animals among others (Atuanya, 2017). There are others that cannot be converted into any beneficial secondary use and therefore pose a serious threat to the environment and one of such is spent engine oil.

Spent oil sometimes referred to as waste engine oil is produced from automobile mechanic shops and mechanical or electrical engine repairers’ shops (Baek and Lee, 2014) 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. 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.

According to Oguntola, (2011), 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. The presence of spent lubricant oil in soil increases bulk density, decreases water holding capacity and aeration propensity. 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, Collins & Lyne, (2016) noted buildup of essential elements such as organic carbon and organic matter and their eventual translocation to plant tissues. These conditions generally cause unsatisfactory seed germination, growth and yield in soil contaminated with spent engine oil. For instance, Ogboghodo, Azenabor and Osemwota, (2015) reported low yield and decreased growth of plant grown in spent lubricant oil contaminated soil. In most cities and towns in Nigeria, some farmers or residents grow vegetables, maize and other crops around the mechanic villages or sink borehole without considering the health risks involved. Researchers such as De Jong, (2010) had worked on effect of spent lubricant oil contamination on soil properties and crop yield but not much work has been carried out on heavy metals uptake by crops in Abakaliki areas. Therefore, the objectives of this study were to study effect of different levels of spent engine oil on soil properties, grain yield of maize and its heavy metals uptake.

1.2      Statement of the Problem

Spent oil sometimes referred to as waste engine oil is seen and get from automobile mechanic shops and mechanical or electrical engine repairers’ shops after servicing the vehicles engines, generating set and other types of engines.

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