CHAPTER ONE
INTRODUCTION
- Background
Industrialization is highly desirable for the sustenance of a nation’s economy and the enhancement of the citizenry’s well-being. In the face of its numerous benefits, industrialization is characterized by environmental problems, chief among which is the release of the noxious substances into the atmosphere. Such releases come as a result of the combustion of associated gases following oil-field development, and combustion of hydrocarbon gases in oil refineries and vehicular as well as fugitive emissions, amongst others.
There is concern about the presence of persistent semi-volatile organic and inorganic compounds in the atmosphere. This is especially for those that are subject to long-range atmospheric transport and as a result, display toxic effect at low concentrations. A key regulatory response to the increasing levels of contaminants and green house gases is to monitor their concentrations in the atmosphere as well as other media, in an effort to establish source and distance trends. The presence of one or more of these contaminants in the outdoor or indoor atmosphere in quantities and duration such as to be injurious to human, animal or plant life is known as Air pollution. Since the issue of pollution is global, any study that is aimed at establishing trends in concentration levels of green house gases, particulates and other unfriendly substances in the atmosphere using analytical or numerical techniques is highly desirable.
1.2 Statement of the problem
Activities associated with Gas field development and other exploration and production activities usually deposit unwanted by-products into the ecological system. The effects may be catastrophic if their levels are uncontrolled or unchecked at least. In Nigeria, there is paucity of data on the major cities in Nigeria which involves a high level of sampling and analysis. On the other hand, simple sampling techniques can be adopted to evaluate urban and rural air quality for a few cities in order to generate a data base which can serve as base-line information for numerical studies in air quality in those cities. A combined monitoring-modeling approach, in which the concentration of inorganic species, total hydrocarbons and particulate matter in the atmosphere is obtained at various distances from a datum by analytical techniques followed by modeling and simulation of atmospheric dispersion, is a good starting point for generating a large of body information in atmospheric discharges.
1.3 Study objectives
The objective of this work is to evaluate the adaptability of a modified Gaussian dispersion model and has necessitated the following aims and objectives of this study:
- To develop a dispersion model suitable for predicting air quality for various atmospheric stability conditions.
- To design a simple quality simulator based on developed model.
- To simulate the concentration profiles of pollutants using computer program (Engineering Equation Solver)
1.4 Methodology
A modified Gaussian dispersion model was developed by applying Fick`s law of diffusion and conservation of species on a differential portion of a plume. This application led to a steady-state equation, whose general solution is given by Robert (1996).The expression for calculating the steady-state concentration field from point source was derived by substituting the turbulent diffusivities that are related to dispersion coefficients as shown by Robert (1996) into the general solution equation.
An algorithm for implementing the solution of the governing equation was developed using computer program as illustrated in a flow chart. The concentration profiles of pollutants were simulated using computer program (EES) and the results obtained were compared to those of SCREEN 4.
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