TITLE:
Analysis of Ground Level Ozone and Nitrogen Oxides in the City of Dar es Salaam and the Rural Area of Bagamoyo, Tanzania
AUTHORS:
Asha Mansour Hamdun, Takemitsu Arakaki
KEYWORDS:
Ozone, NOx, Daily Variation, Bagamoyo, Dar es Salaam
JOURNAL NAME:
Open Journal of Air Pollution,
Vol.4 No.4,
December
30,
2015
ABSTRACT: From 2012
to 2015, we measured surface ozone, NOx, 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 NOx 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 NOx 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.