Variation Of Wind Speed With Attitude In The Dispersion Of Gasseous Pollutants

1.0 Introduction

Natural resources have been exploited by the man for meeting his needs from the dawn of civilization (Richa et al., 2011). However, the acceleration of exploitation has been increasing at a high rate and in non-judicious manner during past few decades especially with the advent of industrial revolution. Industrialization has provided humanity with materials and social benefits. It has also brought in its wake up many unwanted substances and social problems. One of these problems is the degradation of the environment. These environmental problems are becoming threats to the existence of living beings. The environment upon which our life is most dependent, has fallen victim of pollution brought by man himself through unplanned and unscientific urbanization, industrialization and mineral exploitation (Richa et al., 2011).

Literally environment means surrounding. Environment influences all aspects of life. Until the conference on Human Environment held at Stockholm in 1972, the importance of environmental protection for improving the standard of living of human being was not realized. In 1991 at the World Commission on Environment held at Rio de Janeiro, the Heads of different countries met and decided to take immediate action to improve the Global Environment.

Air pollution has become an extremely serious problem for the modern industrialized world. Air pollution may be defined as any atmospheric condition in which certain substances are present in such concentrations that may produce undesirable effects on man and ecosystem. These substances include gases (sulphur dioxide, nitrogen oxides, carbon monoxides, hydrocarbons, etc.), particulate matters (smoke, dust, fumes, aerosols, etc.), radioactive materials and many others. Air pollution may or will have harmful effects on living things and materials. It may interfere with biochemical and physiological processes of plants to an extent, which ultimately leads to yield losses (Heck et al., 1988).

Air pollution was earlier considered as a local problem around large point sources. But due to use of tall stacks and long range transport of pollutants, it has become a regional problem. The trans-boundary nature of pollutants was clearly evident when areas remote from sources of air pollution also showed higher concentrations of air pollutants. Uncontrolled use of fossil fuels in industries and transport sectors has led to the increase in concentrations of gaseous pollutants such as SO2, NOx, etc.

Contaminate gases, liquid and particulate matter discharges into the air are transported over a long distance by large-scale air-flows and dispersed by small-scale air-flows or turbulence, which mix contaminates with clean air. This dispersion by the wind is a very complex process due to the presence of different sized eddies in atmospheric flow (National Institute of Water and Atmospheric Research, 2004).

The major portion of the recognized gaseous pollutants are gases such as carbon monoxide (CO), the oxides of nitrogen (NOx), the oxides of sulfur (SO2), unburned hydrocarbons and particulate matter (dusts, smokes, mists, aerosol). These pollutants are emitted by different sources, such as: transportation, electric power generation, refuses burning, industrial and domestic fuel burning) (Smith, 2004). Increasing air pollution levels due to rapid urbanization and growth in industrial emissions are now causes of major concern in many large cities of the world (Abdul-Kareem, 2005). When strategies to protect public health are under consideration, establishing ambient air quality standards and regulations have been introduced in order to set limits on the emissions of pollutant (US EPA, 1999). To achieve these limits, consideration was given to the variation of wind speed in the dispersion of gaseous pollutants. Therefore, air quality models are indispensable tools for assessing the impact of gaseous pollutants on human health and the urban environment (Gokhale and Khare, 2004)

The necessity for such models has increased tremendously especially with the rising interest in the early warning systems in order to have the opportunity to take emergent and preventive action to reduce gaseous pollutants when conditions that encourage high concentrations are predicted.

On the other hand, long-term forecasting and controlling of wind speed in dispersion are also needed in order to prevent the situation from becoming worse in the long run. Such forecasting is especially important to sensitive groups i.e. children, asthmatics, pregnant women and elderly people (Kolehmainen, 2004).

Kim et al. (2010) focused and discussed emission factor and sources profiles of gaseous pollutants particulate matter, PM2.5 and (CO, NOx, CO2) emitted from in-use diesel vehicles. Kim et al. (2006), Gupta & Kumar et al. (2006) and Marieq et al. (2007), showed diesel vehicles contribute significantly to the fine particulate and its chemical composition which they have important health, atmospheric and climate implications. Krewit et al. (1998) investigated that the particulate (less than 2.5μm diameter) has one of the highest health risks attributable to electricity generation and it can be treated as a conserved species in outdoor air on the time scale of transport within 100Km.

Thermal power generation is the largest source of SO2 and other gas pollutants in the city besides other industrial processes (Naik, 1992). It is commonly understood that SO2 reduces atmospheric visibility, damages various materials and agricultural crops and is detrimental to human health (Naik, 1992). When SO2 is oxidized and hydrolyzed it gives rise to acid rain. The quantitative estimation of the long-term average of SO2, NO2, CO and fly ash has been dealt with by many researchers (Patil and Patil, 1990).

Chih-Chung and Hui-Hsuan (2010) investigated how gaseous pollutants (PM10, SO2, NO, CO) and meteorological conditions (wind speed) affect atmospheric turbidity.

The relation between the concentration of gaseous pollutants SO2 in the air in the vicinity of Bratislava and the degree of injury to local was studied by Navara and Kaleta (1970) and from their results they concluded that vegetation visibility and is injured most seriously near the industrial complex of Bratislava, where the SO2 concentration in the air reach annual average in the range 20-100μg/m3 and SO2 of 10-70μg/m3 occurring in the region at the distance of 5-15Km from the pollution sources cause chronic damage to the vegetation.

1.1 Statement of the Research Problem

The concentration of gaseous pollutants at a given place is a function of a number of variables, including the emission rate, the distance of the receptor from the source, and the atmospheric conditions. The most important atmospheric conditions are wind speed, wind direction, and the vertical temperature structure of the local atmosphere. If the temperature decreases with height at a rate higher than the adiabatic lapse rate, the atmosphere is in unstable equilibrium and vertical motions are enhanced. This is to keep pollution concentrations moderate or weak at ground level. But, if the temperature decreases with height at a rate lower than the adiabatic lapse rate (stable atmosphere) or increases with height (inversion), vertical motions are reduced or damped. This will lead to potentially high pollution concentrations (APTI, 2005).

1.2 Aim of the Research Work

The aim of this research is to determine the variation of wind speed with attitude in the dispersion of gaseous pollutants.

The specific objectives of the research work are:

• To estimate the daily wind speed within Makurdi metropolis.
• To use the determined result to evaluate the rate of dispersion of gaseous pollutants based on the estimated values.
• To describe the trends of dispersion of gaseous pollutants

1.3 Significance of the Study

This research work will provide adequate information about wind speed, attitude in the dispersion of gaseous pollutants, hence providing vital information for planning on health. It will attempt to justify the importance of integrating air pollution climatology in spatial planning, to ensure that the desire for agricultural and environmental sustainability is achieved.

1.4 Scope and Limitation of the Study

This research work is limited to the daily mean maximum wind speed data over Makurdi metropolis sourced from Federal University of Agriculture Makurdi, Benue State for the period of thirty (30) days.