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Analyses of Some Meteorological Parameters Pertinent to Air Pollution in the Okrika-Onne Axis of Rivers State, Nigeria.
A. E. Gobo Institute of Geosciences and Space Technology, Rivers State University of Science and Technology, P.M. B. 5080, Port Harcourt, Nigeria.
T. K. S. Abam. Institute of Geosciences and Space Technology, Rivers State University of Science and Technology, P.M. B. 5080, Port Harcourt, Nigeria.
Abstract The Okrika Onne axis or the greater Port Harcourt area is one of the most industrialized belts of Nigeria. Among the many industries in the locality are Nigerias largest and most modern oil Refineries and the Petrochemical complex, the National Fertilizer company (NAFCON), and the deep ocean harbour. These industries have the potential to generate emissions, which are propagated by meteorological agents. This study employs statistical tools to highlight the need for analyses of some meteorological data that relate to Environmental Impact of industrial emissions in the Okrika-Onne axis. It also addresses the necessity to establish existing meteorological conditions prior to the commencement of operations at the NAFCON plant. Results obtained show that the relative humidity is high and the predominant wind is mostly in the Southwesterly direction towards the densely populated Nchia-Eleme community. The study also found that although the wind speeds are relatively low, pollutants emitted could be easily dispersed and circulated in the predominant wind direction due to high temperature.
Key Words: Meteorological parameter, Okrika-Onne, Rivers State, Nigeria.
Introduction: The atmosphere has always been used as a sink for gaseous pollutants. The process of pollutant transport, dispersion, concentration and reactions are dependent on meteorological/climatological conditions. Thus air quality impact studies or air pollution prediction studies are greatly influenced by meteorological and climatological parameters such as temperature, wind speed and direction, rainfall, insolation, relative humidity, cloud cover, pressure and solar radiation ( Wark and Warner 1976). The study area is a meteorological sub-station at the Okrika Onne axis (Figure 1), adjacent to the National Fertilizer Company (NAFCON), having a reference co-ordinate (7o 0`E, 4o 31`N). The area experiences heavy rainfall from March to October and dry months from November to February with occasional rainfall (Gobo, 1988). The mean annual rainfall of the area is about 2,535.15mm and the climate could be classified as humid semi-hot equatorial type (Salau and Lawson 1986: Gobo 1998). The National Fertilizer Company (NAFCON) which may contribute to pollution emission in the area was established in 1986 and commenced production in 1987, albeit without environmental impact assessment. The objective of this study is therefore: (i) to examine the prevailing meteorological conditions of Okrika Onne Area prior to and after commencement of production at NAFCON. This will serve as a basis for future studies of the influence of the factory on atmospheric parameters and the environment. (ii) to provide samples of climate of the area for future and further detailed analysis
Data Collection and Analysis The data for this study was collected from the state meteorological sub-station at Okrika Onne area. The sampling was carried out hourly for 1986 and 1987 prior to commencement of production at the NAFCON plant. Data on rainfall and radiation were collected daily, while temperature, relative humidity, wind speed and direction measurements were taken twice daily at 0900 GMT and 1500 GMT. Rainfall was measured with the tipping bucket rain gauge, while temperature was measured with the dry and wet bulb thermometer. This thermometer was attached to a Stevenson screen that avoided direct rays from the sun, while also allowing cross-ventilation. The relative humidity on the other hand was obtained through the same wet and dry bulb thermometer using hygrometric tables. Radiation and wind direction/speed were measured using scintillation counters, and wind vane and cup anemometer respectively. The data was subjected to statistical and graphical analysis.
Results The rainfall pattern, solar radiation, relative humidity and temperature of the study area are presented in figure 2. The figure shows rainfall as low as 5.05mm obtained in January while the highest (390.1mm) was in September. The monthly variation of solar radiation indicates high values throughout the year, within the study area, with the maximum occurring from November to June and the minimum from July to October. The highest amount of solar radiation was recorded in April and the least in August. The relative humidity of Okrika Onne area varied between 71% (January) to 85.5% (August and September). The average relative humidity was about 79.98%. Also for the same period, the ambient temperature varied between 25.0oC in August to 28.1oC in (April) with average monthly temperature of 26.58oC. Wind roses have been constructed for the area based on the acquired data (Fig 3). Figure 4 is a gross representation of the annual average of wind speed and frequency in different directions. Details of characteristic monthly variations in wind speed and direction are provided in figures 4 in the form of monthly wind roses (1986 1987) for the area. The Southwesterly wind is the more dominant, with average speed of 70.63 knots. Discussion The months of July to September are characterized by heavy rainfall. These heavy rainfall events are associated with the disturbance lines, which are characterized by thunderstorms and squally winds. The observed patterns of variation in rainfall and solar radiation were confirmed by Adefolalu (1981), who reported that in the coastal areas, the sky is generally clearer with less cloud cover in the period March April, in comparison to the period June to August which has greater cloud cover. This is attributed to the presence of much water vapour in the atmosphere since the monsoon at this time advects maximum moisture from the ocean to this area. Relative humidity is a measure of water vapour in the atmosphere. In this respect, it is a quantitative approach to measuring the wetness or dryness of the air. A comparison of the temperature and relative humidity variations (Figure 2) indicates that the period (July, through October), which has the lowest temperature (25.25oC 25.75oC) correspond to the period of highest relative humidity, while the warmest months of February through April, occur just before the main rainy season. The relative frequency of occurrence of wind direction (%) and the wind speed (knots) have been deduced from an analysis of the wind roses for the area. It is observed, that the degree of calmness from January through August is very low (varying between 0o to 29. 19o). The lowest was recorded in January (0o) while the highest degree of calmness was obtained in October (54 55o). The study shows that, the Southerly winds are predominant most times of the year (Figure 1). Since the winds are predominantly southerly, pollutants or effluents emitted from the industries will be conveyed more by these winds. Though the wind speed is relatively low most times of the year, the high average temperature of 25.58oC could facilitate the dispersion of emitted pollutants. Densely populated communities that may be eminently affected by atmospheric contaminants emitted by NAFCON are shown (Figure 1). Therefore industries around this area particularly NAFCON could take cognizance of the prevailing dominant wind direction in the selection of sites for location of experimental farms, offices and residential houses. Buildings, especially residential houses should be located to take advantage of the refreshing and cooler southerlies. Relative humidity is important in the determination of comfort index of workers and those resident within the vicinity. The area is characterized by high relative humidity which will result in people around this area, having excessive perspiration and general suffocating feelings especially during the afternoons.
Conclusions The study has examined the micro-climatic characteristics of the environment of the Nitrogenous fertilizer company. The study had aimed at providing an insight into the prevailing meteorological conditions, which would govern the spread of buoyant atmospheric pollutants in the area. The study confirmed the southerlies as the most dominant wind direction that potentially influences the dispersion of atmospheric pollutants.
References Adefolalu DO (1981) The Weather and Climate of Calabar. Dept. of Geog. and Regional Planning, Univ. of Calabar. Research (Project) Pages 188 207. Gobo AE (1988) Relationship between Rainfall Trends and flooding in the Ni ger-Benue Rivers Basins. J. of Meteorology U. K., 13 (132) : 319. Gobo AE (1998). Meteorology and Mans Environment. Africa-link Books, Ibandan. Salau OA & Lawson TL.(1986) Dewfall features of a Tropical station: The case of Onne (Port Harcourt), Nigeria. Theoretical and Applied Climatology. Springer-Verlag Netherlands. 37: 233 240. Ubong IU & Gobo AE (2001). Fundamentals of Environmental Chemistry and Meteorology. Torn and Harry Publishers. Port Harcourt. Wark K & Warner CF (1976). Air Pollution for origin and Control. Harper and Row Publishers. Pg. 68 71. |
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