DIURNAL AND SEASONAL VARIATIONS OF CARBON MONOXIDE (CO) CONCENTRATION AT URBAN AND RURAL SITES IN AKURE, NIGERIA.

Abstract

The variations in carbon monoxide (CO) concentrations has been examined at an urban and a rural site in Akure, a medium-sized tropical city in south western Nigeria using Lascar EL-USB-CO portable data loggers for the period of one year (Feb. 2009-Jan. 2010).Daily mean,maximum averages was carried out for twelve months for both the urban and rural sites. The data set were ploted using contour plots and Microsoft Excell package. The level of significance were tested using one way Anova and Standard deviation. It was shown that Carbon monoxide (CO) concentrations at the city Centre showed an exclusive distinct variation throughout the day of the week variations with respect to traffic rush hours, and were 2-3 times that of the rural concentrations. The 9 ppm statutory limit set by the WHO was clearly exceeded at the 8 hours average , while the rural site exhibited a consistent cyclic diurnal pattern throughout the week. The diurnal variations at the rural site recorded significant value of +0.029 at 1hour average and + 0.0078 at 8hours average. While the city recorded a significant value of +0.54 at 1hour average and + 0.667 at 8hours average. There is a significant variation(p<0.001) in the concentration of the carbon monoxide with the highest CO of 12-16 ppm recorded between October and March in the city. A weekend effect was significantly observed, which is attributed to the emission of Carbon monoxide as a result of high vehicular traffic during party activities on Saturdays and the rush for Church attendance on Sundays There was a sharp reduction in the CO concentration in the month June/July and August/September. The sharp reduction could be due to rain out effect of the CO concentration.The major source of CO in the city was due to high vehicular traffic, while bush burning was the major source of CO in the rural site. Keywords: Carbon monoxide, Concentrations, Urban, Rural, Akure, Nigeria