Pollutants in Air and Heavy Metals in Street Dust of Some Selected Locations in Zaria
Aim and Objectives
The aim of this research is to determine the presence and concentrations of some gaseous pollutants in ambient air and some trace metals in street dust at the Sabon-Gari Market Zaria and Aliyu Mustapha Social Centre, Ahmadu Bello University, Zaria, thus, serving as the base data for gaseous pollution level in these locations in Zaria. This aim would be achieved through the following objectives:
- To ascertain the presence and concentration of some gaseous pollutants such as CO, H2S and SO2 at the Sabon-Gari Market Zaria and Aliyu Mustapha Social Centre, Ahmadu Bello University
- To determine how the concentration of these gases varies daily from morning through afternoon to evening.
- To determine the levels of heavy metals such as Cr, Cd, Ni, Pb and Fe in street dust from Sabon-gari market in Zaria.
Carbon Monoxide (CO)
Ever since man learned how to break stone by heat or to burn wood with resisted flow of air to produce charcoal, he has been affected by carbon monoxide (Wellbum, 1988). Whilst smoking is the major source of carbon monoxide for humans, most of the hazards at work connected with gas come from motor vehicles. During their repairs, testing, raising or servicing (Cuddenback et al., 1976, Wellbum, 1988). Blasting, fire-fighting, methanol production, wood distillation and cooking over charcoal have similar hazards (Goldsmith 1968, Wright et al., 1975, Deckoning et al., 19852, Albalak et al., 1999).
Carbon monoxide unlike many toxic gases is a colourless, odourless and life threatening gas, can be breathed without giving any warning to the victim. It is a poisonous gas produce by the partial combustion of wood, coal, tobacco, car emission, gas water heater, leaking chimney and furnaces, generators and other gasoline powered equipment (Deckoning et al., 1985). Carbon monoxide is the next most abundant atmospheric pollutants in the troposphere. Emission of carbon monoxide caused by man far exceeds those of other pollutants (Thompson et al., 1973). Sources of air pollutants are diverse and are often impossible to discriminate between them. Domestic sources often surround industrial sources and power or heat generation by particular activities without making distinction between industrial and domestic apportionment.
In areas away from major sources, the atmospheric level of carbon monoxide is fairly constant which meant that significant natural sinks exist to remove this vast excess of gas. The natural sinks and their relative importance are the oxidation to carbon dioxide in the troposphere by hydroxyl radicals. Oxidation in the stratosphere or absorption by soil microbes, the ocean, or plant and animals. (Wellbum 1988, Abbey et al., 1993).Wood, stubble, dunk and grass are use daily in about half of the world’s household as energy for cooking. In most part of the third world, they are burnt in open fire or inefficient stoves in poorly ventilated kitchen. (Hayes,1989; Engel et al., 1998, Bouce et al., 2002a). The result is toll in death and ill health far greater than the outdoor air pollution. The first of severe poisoning is loss of consciousness and further inhalation of high concentrations readily lead to death (Raub et al., 2000). During normal combustion each atom of carbon in the burning fuel joins with two atoms of oxygen forming a harmless gas called carbon dioxide. When there is lack of oxygen to ensure complete combustion of the fuel, each atom of carbon links up with only one atom of oxygen forming carbon monoxide gas.
Carbon monoxide inhibits the blood capacity to carry oxygen in our lungs. Carbon monoxide quickly passes into our blood stream and attaches itself to haemoglobin (oxygen carrying pigment in red blood cell). Haemoglobin readily accepts carbon monoxide even over the life giving oxygen atom (as 210 times as readily as oxygen), forming a toxic compound known as carboxyhaemoglobin (COHb); consequently, disrupting oxygen transport to the tissues (Raub, 2000). Depending on the amount inhaled, CO impedes coordination, worsen cardiovascular conditions and produce fatigue, (Cuddenback et al., 1976, Hayes 1989, Lippmann 1989, Bruce., et al 2002a & b). The elderly, the fetus and persons with cardiovascular and pulmonary diseases are particularly sensitive to elevated CO level (Raub et al., 1989). Methylene chloride found in some common household products such as paint strippers can be metabolized to form carbon monoxide which combines with the haemoglobin to form carbonyl haemoglobin. Carbonyl haemoglobin levels of the order 60% COHb saturation are normally fatal. Lower concentration of 40% saturation can also be lethal for young or elderly people. (Behera et al., 1988).
MATERIALS AND METHODS
The Study Area
Zaria lies at latitude 10o28’N and longitude 7o25’E (Africa Atlas, 2002). It is located in the centre area of what used to be called the North Region of Nigeria. The mean annual rainfall in the area ranges from 924.3-1543.6mm. Annual temperature varies between 29oC-38.6oC (Africa Atlas 2002). Today Zaria is a local government in Kaduna State.
The selected areas for this investigation were areas with high traffic and business activities. These areas were busy within the hours of 6.30 – 8.30am when offices and commercial activities commences and 4.00 – 7.30pm in the evening at the close of work and market activities.
Two locations were considered for this analysis. Location one (1) is the Sabon-Gari Market Zaria. Here, four (4) sampling sites were randomly selected and labeled (A-D) with an average distance of 50metres from one another. Site A known as kasuwa mata is characterized by mini- park for trucks, petroleum dispensing station, groundnut oil sales points, and runoff from gutter. Site B otherwise known as Samaru bus-stop, houses a mini-park for vehicles and motorcycles, with shops surrounding the site and presence of refuse dump site.
Site C has boutiques and shops with regular use of generator and other gasoline-powered equipment. The sale of food stuff is also noticed around the site as well as gutter presence.
Site D has around it a T-junction and a mini-park for motorcycles and tricycles.
The location two (2) of this study is the Aliyu Mustapha Social Center A.B.U Zaria. Three sampling sites were also randomly selected and labeled (A-C). Site A has around it a mini-park for motorcycles, gutter, drainage channels from kitchens and also a very close vicinity to the road.
CHAPTER FOUR RESULTS AND DISCUSSION
General Discussion of Gaseous Pollutants
The pollutant gases sulphur dioxide (SO2), carbon-monoxide (CO) and hydrogen-sulphide (H2S) are dispersed throughout the atmosphere at the Sabon-Gari market and Aliyu Mustapha Social Centre A.B.U. Zaria. The concentration of these gases especially the criteria pollutants sulphur dioxide and carbon-monoxide are high in some sites with respect to the timing of the day and low in some other sites; though, they are not high enough to cause serious health problems; but information on their spatial distribution is of importance. It may be useful in tighter emission standards, closer monitoring of the gases, creating alternative sources of energy to reduce over dependence on fossil and natural fuels thus, creating a cleaner air.
CONCLUSION AND RECOMMENDATIONS
The result of the studies conducted is serving as the base data for gaseous pollutant level at the location in Zaria and showed that the concentration of the gaseous pollutant do not pose an immediate threat to humans and the environment, however, it is necessary to check periodically the levels of these pollutant especially sulphur dioxide (SO2) which rate very poor (E) for all the sessions at all the sites in location 1 and 2 respectively except for the morning hours where best rating is poor (D) for all the site in location 2, for their increase or decrease. These results can serve as evidence to policy maker to enacting laws and regulations that could serve to checkmate further pollution activities and provide treatments to polluted air.
The concentration of heavy metal Cr, Cd, Ni, Pb and Fe and their contamination levels in street dust collected from Sabon- gari market has being studied in this work. The concentrations of the metal in the soil are in the order of Fe>Pb>Cr>Ni>Cd. This order is in congruency with those reported by Abechi et al., 2010. The level of Fe at the moment is high compared in other studies in Nigeria this is perhaps because Fe forms a composition of soils in Northern Nigeria (Abechi et al., 2010). Hence, possible accumulation in the soil and inhalation by human around could occur as a result of continual usage of the road by automobiles and motorcycles. This can thus lead to accumulation of metal in the tissue of human.
The distribution and concentrations of heavy metals in all the sites shows that automobile originated sources (emission or by wear and tear of different parts of the car) are the main source of pollution.
It is hereby suggested that, for a cleaner environment in air quality, proper air quality management programmes; improve traffic flow and control which requires good road network, improve fuel quality through reduction of sulphur, proper legislative frame work to regulate and control emission and finally with proper implementation of these control measures be encouraged.
- A comparative analysis should be carried out to correlate the use of chemical and automatic method for gaseous pollutants determination, to ensure a better air quality assessment method.
- Periodic analysis should be embarked on for air quality analysis in the study area and other areas to be able to monitor the pollution level.
- Other gaseous pollutant aside CO, H2S and SO2 can as well be monitored to be abreast of their pollution levels.
- Most individuals spent long hours n their work places, it is thus suggested that further studies be carried out to ascertain air quality in work place atmosphere with particular reference to densely populated workplaces like, lecture Halls, factories t.c.
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