The variations in concentrations of air pollutants in an urban setting depend on the living pattern of the people, traffic flow,
and meteorological conditions. Ambient VOCs (volatile organic compounds) measured in two urban centers of southwestern Nigeria
were analyzed and evaluated for the variation characteristics: spatial, seasonal, and diurnal patterns of air pollutants. For this purpose
samples were collected (from June 2009 to May 2010) at different microenvironments, selected to represent local activities in the city.
To determine the diurnal pattern of VOCs, four hourly sampling were carried out at different days of the week at six days interval.
Samples were analyzed using gas chromatographic system. Among the VOCs species detected are four alkanes, six aromatic
compounds, four chlorinated hydrocarbons and one ketone. The results showed that ambient VOCs level in atmosphere of two centers
is driven by high traffic, with highest concentrations observed in most traffic junctions sampled. The examination of the average of
total VOCs accumulation showed significant spatial and seasonal variability (p < 0.01) in all sites. The results of diurnal analysis
showed the highest TVOCs (total volatile organic compounds) concentrations were measured in the morning hours in almost all the
sampling sites of this study. The correlation between TVOCs concentrations and frequencies of wind speed and relative humidity
showed that the TVOC values were lower when the wind speed and relative humidity were high. The trend of variations indicates that
fresh emissions of VOCs concentrations are impacting the atmosphere of the study centers and suggest the importance of contributions
from sources other than vehicular emission, which are not uniform throughout the year.