Author(s)

Asha Mansour Hamdun¹, Takemitsu Arakaki^2*

¹Department of Aquatic Science and Fisheries, College of Natural and Applied Science, University of Dar es Salaam, Dar es Salaam, Tanzania.
²Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Okinawa, Japan.

From 2012 to 2015, we measured surface ozone, NO_x, NO₂, and NO levels at three urban sites (Mapipa, Ubungo, and Posta) and two suburban sites (Kunduchi and Vijibweni) in the city of Dar es Salaam and in the village of Mwetemo, a rural area of Bagamoyo, Tanzania. The average hourly O₃ concentrations at all sites were between 9 ppb and 30 ppb during our sampling periods. O₃ levels at suburban sites were generally higher than at urban sites. The average hourly concentrations in Dar es Salaam were 10 - 32 ppb, while in Bagamoyo they were 9 - 15 ppb. We observed a strong diurnal variation in Dar es Salaam while measurements from Bagamoyo showed little variation. At Dar es Salaam, the surface O₃ concentrations increased from their minimum level at sunrise (around 6:00 a.m.) to a maximum in the late afternoon (around 4:00 p.m.), and then decreased toward 11:00 p.m. Another secondary ozone peak appeared between midnight and ~4:00 a.m., after which the surface ozone concentrations decreased to a minimum around 7:00 a.m. NO₂ concentrations were higher at the urban sites of Ubungo and Posta, and their weekly average NO₂ concentrations were 246 ppb and 118 ppb, respectively. Weekly average NO_x concentrations ranged from 39.4 ppb at the Kunduchi site (suburban) to 738 ppb at the Ubungo site (urban). To our knowledge, there were few continuous measurements of ozone and nitrogen oxides concentrations in Tanzania. Since high NO_x concentrations were observed, continuous air quality monitoring and effective air pollution control measures are required in Dar es Salaam to prevent further deterioration of air quality and limit the possible negative impacts on humans and vegetation.

Ozone, NO_x, Daily Variation, Bagamoyo, Dar es Salaam

Hamdun, A. and Arakaki, T. (2015) Analysis of Ground Level Ozone and Nitrogen Oxides in the City of Dar es Salaam and the Rural Area of Bagamoyo, Tanzania. Open Journal of Air Pollution, 4, 224-238. doi: 10.4236/ojap.2015.44019.