The level of gaseous emissions (CO, NO 2 and SO 2) at four strategic places in Makurdi metropolitan area of Benue State was determined using handheld TO Crowcon Gasman gas meters for a period of one month, during peak periods of traffic flow at the selected locations within the city . The level of emission recorded at the major road junctions in Makurdi showed CO with highest concentration (0.57 - 10.2 ppm), followed by NO2 (0.01 - 0.11 ppm) and SO2 (0.00 - 0.1 ppm) in all the sampled sites. This showed a concentration pattern of SS1 > SS2 > SS3 > SS4 in all the sampling stations. The results established that the emission levels in metropolis especially in the afternoon were slightly higher than the Nigerian air quality standard accepted safe limits of 10 ppm for atmospheric CO, 0.04 - 0.06 ppm for NO2 and 0.1 ppm for SO2, respectively. These will have adverse health effects and may contribute to climate change, in the long term, if unmitigated.
Air pollution has long been recognized as the most fatal form of pollution due to increasing pollution levels as a result of urbanization and growth. This is a source of major concern to both modern and fast growing societies in the world to which Benue State cannot be an exception.
Air pollution can be caused by natural or man-made activities and one of such activities is vehicular emission, which derives their energy from the combustion of fossil fuels. In the process of combustion, vehicles emit into the environment exhaust gases, which create serious environmental and health concerns. These emissions contain carbon monoxide (CO), oxides of sulphur (SOx), oxides of nitrogen (NOx), Ozone (O3), hydrocarbons and particulate matter. Some of these gases are called Green House Gases (GHGs) [
The impact and complexity of traffic-related air pollution in Nigeria today, alongside concurrent emissions from industrial and domestic sources therefore necessitates a new approach to the mitigation and management of air pollution. An assessment of the potential for increased vehicular pollution requires some basic information relating to traffic volume and the intensity of pollutant emissions on road corridors [
Makurdi is the capital city of Benue State. The city is located along the Benue River bank on latitude 7.44N and longitude 8.32E situated in a valley 100 m above sea level. Makurdi can be said to be predominantly a civil service and commercial city as most of the administrative offices are situated in the city and as such most of the populace spend their time outdoors. Through careful observations, sampling sites or stations in the metropolis were identified prior to the dates of field work; the coordinates of the sites were obtained using the Global Positioning System. Busy roads in the metropolis were considered due to high traffic volume always experienced on these roads and the location of commercial activities along such roads. Four sampling sites were considered: Wurukum round-about (SS1), High Level round-about (SS2) and Wadata market Junction (SS3) in Makurdi (See
The raw data obtained at each site was recorded, accordingly for morning, afternoon and evening. Mean values were calculated for repeated measurement to obtain a representative discrete value; statistical analysis of the data was carried out using statistical software programme (SPSS version 16.0). To start measuring the gases (CO, NO2 and SO2), the switch is first turned to TEST position. Red LED with flash, sounder will operate, display will indicate battery condition (100 = fully charged). After which the switch is turned to Gas position. Unit is then in normal operation. The Green LED will flash and operational sounder will operate once every three seconds to confirm normal operation. The specification for gas and range for CO gas meter is 0 - 500 ppm, SO2 gas meter is 0 - 10 ppm and NO2 gas meter is 0 - 10 ppm respectively. While the temperature range is −10˚C to +50˚C and humidity range is 0% - 90% RH, non-condensing.
Sample Collection and quantification: The measurement of the concentration of the toxic gases (CO, NO2 and SO2) over time (3 minutes interval) for 1 hr 30 minutes were made during different phases of traffic (Morning―7:30 am to 9:00 am, Afternoon―12 pm to 1:30 pm and Evening―4:00 pm to 5:30 pm) within a week for each site. The parameters were measured simultaneously using the different meters and the reading was taken 2.0 m away from the edge of the main road.
The mean of the daily concentration of carbon monoxide (CO), nitrogen dioxide (NO2) and sulphur dioxide (SO2) obtained at Wurukum round-about, High-level round-about, Wadata Market junction and University of Agriculture Makurdi is shown in a bar chart plot of concentrations (ppm) with time (min) at each study site from morning to evening as shown in Figures 2-5. The instrument for measuring the emission was taken from one site to another for measurement in June, 2013.
The experimental data obtained in this research work for gaseous emission were calculated into discrete mean. The data were obtained from four sampling sites (Wurukum round-about (SS1), High Level round-about (SS2), Wadata Market junction (SS3) and University of Agriculture Makurdi farm site (SS4). The information was plotted into graphs for different sampling periods (morning, afternoon and evening), respectively as shown in Figures 2-5. Comparatively, CO showed highest concentration (ppm) within a range of (0.57 - 10.17), followed by NO2 (0.01 - 0.11) and SO2 (0.00 - 0.10) in all the sampled sites. The mean (±SD) concentrations (ppm) of the gases obtained in the morning afternoon and evening were; SS1: Morning, CO-8.73 ± 4.17, NO2-0.11 ± 0.03 and SO2-0.01 ± 0.03; Afternoon, CO-10.03 ± 4.31, NO2-0.09 ± 0.04 and SO2-0.09 ± 0.03; Evening, CO-8.43 ± 2.46, NO2-0.11 ± 0.03 and SO2-0.02 ± 0.04 respectively; SS2: Morning, CO-6.23 ± 2.86, NO2-0.11 ± 0.03 and SO2-0.01 ± 0.03; Afternoon, CO-10.17 ± 4.45, NO2-0.00 ± 0.02, and SO2-0.10 ± 0.00; Evening, CO-8.07 ± 3.65, NO2-0.10 ± 0.03 and SO2-0.02 ± 0.04 respectively; SS3: Morning, CO-5.27 ± 3.27, NO2-0.1 ± 0.00 and SO2-0.1 ± 0.02; Afternoon, CO-7.07 ± 2.46, NO2-0.06 ± 0.05 and SO2-0.1 ± 0.00; Evening, CO-8.64 ± 3.28, NO2-0.1 ± 0.02 and SO2-0.05 ± 0.06 respectively, while SS4 has; Morning, CO-0.57 ± 0.09, NO2-0.01 ± 0.03 and SO2-0.00 ± 0.02; Afternoon, CO-1.00 ± 1.32, NO2-0.01 ± 0.03 and SO2-0.00 ± 0.00; Evening, CO-1.03 ± 1.06, NO2-0.01 ± 0.03 and SO2-0.02 ± 0.04 respectively. This showed a concentration pattern of SS1 > SS2 > SS3 > SS4. Though the volume of traffic was high for the three sampled sites (SS 1, SS 2 and SS 3), there was less hold up at SS 3
which may be because the sampling was done during working days and as a result, vehicular traffic was low as many persons were rather driving to offices and schools. Movement towards the market (SS3) was less as such the toxic gases may not accumulate, but are quickly dispersed into the atmosphere. However, there was a rise in concentration of CO in this site in the evening which clearly showed that people usually rush in, to buy things after work, thereby increasing vehicular volume (traffic jam) and human congestion at this time of the day at SS3 [
Comparison of CO between sites shows that CO concentration was higher at Wurukum Roundabout in the morning followed by High Level Roundabout, Wadata Market Junction and University of Agriculture farm site respectively. While in the afternoon, High Level Roundabout recorded the highest concentration followed by Wurukum Roundabout, Wadata Market junction and University of Agriculture Farm sites. And lastly in the evening, Wadata Market junction recorded highest concentration followed by Wurukum Roundabout, High
Level Roundabout and University of Agriculture farm site.
Comparison of NO2 concentrations between sites shows that Wurukum Roundabout recorded highest in the morning, followed by High Level Roundabout, Wadata Market Junction and University of Agriculture farmsite. While in the afternoon, Wurukum Roundabout recorded the highest followed by Wadata Market Junction, University of Agriculture farm site and High Level Roundabout. And lastly, in the evening, Wurukum Roundabout recorded the highest followed by High Level Roundabout, Wadata Market Junction and University of Agriculture farm site.
Comparison of SO2 concentrationsbetween sites shows that Wadata Market Junction recorded highest in the morning, followed by Wurukum Roundabout, High Level Roundabout and University of Agriculture farm site. While in the afternoon, Wadata Market Junction recorded the highest followed by High Level Roundabout and University of Agriculture farm site. And lastly, in the evening, Wadata Market Junction recorded the highest followed by Wurukum Roundabout, High Level Roundabout and University of Agriculture farm site, respectively.
The total average concentration of Carbon monoxide (CO) measured at SS1, SS2, SS3 and SS4, for the four study areas was below the minimum standard (10 ppm) stipulated by the Federal Environmental Protection Agency, now known as National Environmental Standards and Regulations Enforcement Agency (NESREA). However, the level of CO emission for SS1 and SS2 for afternoon was slightly above the standard. This high concentration of CO at SS1 and SS2 may be due to increased transport activities from both vehicles and motor cycles. The result revealed that the higher the number of vehicles, the higher the emission problems to the environment. Omofonmwan and Osa-Edoh [
of the total air pollutants in developing countries [
The quantity of NO2 measured at SS1, SS2, SS3 and SS4 out of the four study areas was higher than the 0.04 - 0.06 ppm (minimum standard stipulated by the National Environmental Standards and Regulations Enforcement Agency) while SS4 fell below the standard. However, NO2 concentration was very low in the afternoon and this may be due to photochemical reaction taking place at that time of the day (VanLoon and Duffy [
The contribution of traffic related air pollution to the air quality in locations of different traffic density in Makurdi was apparent, especially in the high traffic areas. The concentration of pollutants in different traffic density areas varied significantly in the different sites. Results of this study showed that transport-related pollution in Makurdi metropolis is significant and needs to be monitored. It is likely that air quality will deteriorate as the city continues to grow which will result in possible severe health consequences. The overall comparison of data for different sections showed fluctuation in the concentrations of the pollutants depending on the volume of traffic, vehicular type and pollution level as shown in the graphs above. Therefore, Benue State environmental Protection Agency should thus recognize air quality management as a priority and work to prevent further environmental degradation by adopting effective policy, such as inspecting commercial vehicles in the metropolis. This also shows that diseases and effects such as runny nose, chest pain, coughing, eye irritation and sore throat, cardiovascular and pulmonary disease, lungs asthma, et cetera are likely to be prevalent in the metropolis.
We wish to acknowledge Peter Onuwa, Ofuegbu Obinna and Blessing Ogoh for their support during sampling and compilation of data and also staff of Benue State Environmental and Sanitation Board.
Joseph A.Ameh,Terrumun A.Tor-Anyiin,Ishaq S.Eneji, (2015) Assessment of Some Gaseous Emissions in Traffic Areas in Makurdi Metropolis, Benue State, Nigeria. Open Journal of Air Pollution,04,175-183. doi: 10.4236/ojap.2015.44015