ABSTRACT
The study investigates the concentrations of CO, NO2, SO2, CO2 and HC arising mainly from the activities of motor vehicles on the ambient air quality of selected sites in Kaduna metropolis. The sites are situated in the Central market area, the Stadium Roundabout, and Kawo area. Others include Bakin Ruwa Junction, Abuja Junction, Sabon Tasha and a control site at the Angwa Rimi G.R.A. Furthermore, sites situated about a distance of 100m from each of the traffic sites were investigated. The sampling was carried out over both the dry and wet season. Results from dry season survey indicate that the average CO concentrations at the Stadium Roundabout peaked at 29.04ppm. The site also recorded highest concentrations for NO2, SO2, CO2 and HC at 0.042ppm, 0.040ppm, 370.92ppm and 0.030ppm respectively. In the wet season, the Stadium Roundabout recorded highest CO concentrations at 18.72ppm. NO2 was highest at 0.03ppm in Sabon Tasha. Both Stadium Roundabout and Sabon Tasha area recorded highest SO2 concentration at 0.032ppm. Sabon Tasha recorded highest concentrations for both CO2 and HC at 370.92ppm and 0.028ppm respectively. Results from comparison of the average CO concentration with the National Ambient Air Quality Standard (NAAQS), showed that CO concentrations in virtually all sites exceeded the 10ppm for an averaging time of 1 hour in both seasons. The same was true for SO2, which exceeded the 0.01ppm limit for an averaging time of 1 hour. NO2 limit of 0.04ppm for a 1 hour averaging time was exceeded at Stadium Roundabout in the morning hour, Central Market area in the afternoon, and in the evening hours at Central Market, Stadium Roundabout and Bakin Ruwa all in the dry season. All sites were within limit in the wet season. An assessment of the air quality status during the dry season as adjudged using the AQI of the United States indicates that CO concentration at all sites (except Abuja Junction) was "very unhealthy". During the wet season however, CO concentrations was "very unhealthy" in Kawo, Central Market area and Stadium Roundabout, Sabon Tasha and Bakin Ruwa were "unhealthy" while Abuja Junction was "moderate". NO2 concentrations were "good" in both seasons for all sites. SO2 in the dry season was "moderate" in all sites but was "good" in Abuja junction. In the wet season, all sites were adjudged "good. Result from the model showed a decrease in all pollutants concentrations with increased distance away from the traffic sites. The model developed is therefore useful for planning of residential and other facilities in Kaduna metropolis and beyond.