INFLUENCE OF TRAFFIC AND WIND SPEED ON CARBON MONOXIDE CONCENTRATION IN THE CENTRAL BUSINESS AREA OF AKURE

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.