1.1 BACKGROUND OF THE STUDY
Gasoline is a liquid fuel used in spark-ignition internal combustion engines.(Derek etal,2014),(API,2014). It is typically composed of hundreds of paraffin, olefin, naphthene and aromatic hydrocarbons (PDNA) (Derek etal 2014). The issue of public health attributed to environmental pollution in developing countries over the past three decades has been of increasing concern. Environmental pollution by toxic organic pollutants is a widespread problem confronting major cities in developing countries. Aromatics are a base component of gasoline derived from crude oil. Refiners manipulated these substances mainly mixtures of chemicals like benzene, toluene and xylene to Increase the octane rating; a standard measure of the performance of an engine or aviation fuel.
Nigeria and most nations of the world are exceedingly dependent on fossil fuels for their energy needs. For Nigeria, gasoline is the most common energy source of transportation. Due to the large quantities of pollutant species emitted and formed from the regular and diesel fuel combustion (CO2, NOx, unburned hydrocarbons, particulate matter and polycyclic aromatics hydrocarbons). There is an increasing number of air pollution regulation in the U.S and worldwide. Oxygenated compound are now added to gasoline in many parts of the U.S. The are to increase the octane number, compensate for the reduction of aromatics and olefins contents and to decrease emissions of carbon dioxide (CO2) (Calvert etal.,1993; National Academy of Sciences,1991).
Common oxygenated compounds added to gasoline include methanol, ethanol and methyl-t-butyl ether (MTBE). Due to some gasoline leakages from underground storage tanks into drinking water supplies. MTBE has been, or is the process of being phased out in many areas.
Gasoline is obtained from crude oil through blending of atmospheric distillation of naphtha and product from another complex refinery process (Handwerk,2001). Refinery process have developed in response to changing market demand and stricter environmental laws. With the advent of the internal combustion engine production of gasoline have dominated the refining processes (Hinks,2004). This is because the quantities of gasoline obtainable from distillation alone were insufficient to satisfy consumer demand. Therefore, to meet the gasoline demand some petroleum fractions must be converted to gasoline by processes like cracking, Hydro-processing, Alkylation and catalytic reforming (Handwerk,2001). The typical composition of gasoline hydrocarbons (% volume) is; Alkanes 4-8%, alkenes 2-5%, iso-alkanes 25-40%, cycloalkanes 3-7%, cycloalkenes 1-4% and total aromatics 20-50%, (benzene 0.5-2.5%) (Hoekman,1992). Additives and blending mixtures are also added to improve its performance and stability.
These compounds include anti-knock agents, anti-oxidants, metal deactivators, lead scavengers, anti-rust agents, anti-icing agents, upper-cylinder lubricants, detergents and dyes. At the ends of the productions process, finished gasoline typically contains more than 150 separate compounds although as many as 1,000 compounds have been identify in some blends (Hoekman,1992). Hence, in spite of the fact that gasoline is solely used in internal combustion engine, its chemical composition varies depending on the crude oil used, the refinery processes available, the overall balance of product demand and the product specifications.
Gasoline can be classified into three grades according to their octane rating, regular Petroleum Motor Spirit (PMS) have octane rating greater than 85 but less than 88, mid-grade petroleum motor spirit has octane rating greater than 88 but less than 90 (Olayinka,2006).
Gasoline with an octane rating of 87 would have similar characteristics of standard fuel mixture consisting of 87% isooctane and 13% heptanes. This follows that the higher the octane rating the better the fuel performance and the greater the price per gallon (i.e.87 and 90 premium fuels). In addition to a variety of non-aromatic hydrocarbons in gasoline there are many aromatics hydrocarbons some of wish are classified as toxic chemicals, one of major ones is benzene (Kelly etal., 1994). Poorly formulated gasoline with a low octane rating can cause engine knocking increase the incident of incomplete combustion (and therefore increase CO production) and increase wear and tear on the engine petroleum company closely control the content of their gasoline to yield the correct octane rating (Ondrus 1993).
Over the years, the advocacy on human health and general environmental concern has forced the refineries to balance the composition of gasoline to meet the high-performance requirements without jeopardizing human and environmental safety. But substandard gasoline still find their way into the market.
In the riverine communities of Niger Delta, cultivation of crops was one of the main source of their livelihood. The situation has changed due to environmental degradation and pollution caused by oil industries operating in Niger Delta region. Local refinering of crude is a booming trade in the creeks of the Niger Delta. For example, in Nigeria, where most of the gasoline being consume is imported through independent marketers, there is temptation of profit maximization through either adulteration or importation of substandard products.
In recent times, the Joint Task Force (JTF) has destroyed a lot of small-scale artisanal refineries that dot the landscape of region. Destroying the refineries is a superficial approach to addressing this problem because the spring up again and resume production. Instead there is need for government to explore the viability of supporting these local refiners with a few of boosting domestic production and also redistributing wealth.
1.2 STATEMENT OF THE PROBLEM
Increase in vehicular emission (exhaust gases) represents one of the most critical environmental problems in urban areas. This is because exhaust gases like CO2, CO, NO2 and SO2 posed serious environmental threat also, aromatics are carcinogenic and mutagenic in nature. Benzene and its compounds are importance additives in gasoline to increase octane number but it’s exhaust fumes are detrimental to environment and human health. Acute myeloid leukemia, drunken-type actions, memory loss have reported in persons exposed to aromatics fumes. It is on this basis that this research work was developed to achieve the following objectives.
1.3 AIMS AND OBJECTIVES
To determine the concentrations of aromatics in automotive gasoline samples distributed in Uyo metropolis.
To investigate the health implication of the aromatics compounds to human and it’s environment.
To compare the concentrations of aromatics with local and international standards.
1.5 JUSTIFICATION OF THE STUDY
Gasoline samples distributed in Nigeria contain varying concentrations of aromatics. Aromatics hydrocarbons especially from automotive source is a major cause of environmental pollution. Of recent, there have been increase cases of cancer, genetic mutation and other terminal diseases.
1.6 SCOPE OF STUDY
This study is centered on the determination of concentrations of aromatics in automotive Gasoline and its health implication. The area of study is Uyo L.G.A AKs.