Abstract:
Recent observations of street level carbon monoxide (CO) concentrations in Akure city centre
show a high correlation with traffic density most of the time, however the reasons for low
correlation for other periods have not been fully understood. Thus, traffic density may not be the
only contributing factor to the observed CO concentration levels. It is hypothesized that
meteorological factors also play important roles. This study examines the variations of carbon
monoxide (CO) concentrations in relation with wind speed and traffic density .The data used for
this study were obtained between August 2013 – October, 2013 in the street canyon bordered by
the Akure central mosque to the north and the Oja-Oba (Oba’s Ultra-Modern Market) to the south
on Oba Adesida road, Akure using El-USB CO sensor and logger, while wind speed and direction
were measured using RM Young wind sentry connected to a Campbell Scientific CR200 data
logger. Traffic was also measured using a digital traffic counter. Results show that high
concentrations of CO generally occur during periods of heavy traffic density with two distinct
peaks in the morning and evening rush hours .There was a strong correlation between CO
concentration and traffic density. Average CO concentration during weekday was found to be
higher than during weekend.
The higher the traffic count the higher the CO and verse versa, but there are days when CO
concentration are lower even though traffic counts are higher showing that CO levels can vary
based on other factors, particularly climatic (wind speed and direction, air mixing zones, and other
climatic factors) . Weather variables play a major role in dispersing CO and thus the determination
of the level of their concentration. Vehicular exhaust was identified as the main CO source in the
city and inadequate traffic discipline and very low wind speed are identified as the main factors
responsible for the high emissions, accumulation, and low dilution and dispersion of the generated
CO. In this present study, two different modeling techniques are used to simulate CO concentration
at the different point.
