Variation Characteristics of Volatile Organic Compounds in an Urban Atmosphere in Nigeria

摘要

The living patterns of people may create different variations in concentrations of air pollutants in urban setting. Ambient VOCs measured in the Nigerian urban center of Benin City were analyzed and evaluated for variation characteristics; spatial, seasonal, and diurnal patterns of air pollutants. For this purpose samples were collected (from June 2009 to May 2010) at seven locations selected to represent local activities in the city. To determine the diurnal pattern of VOCs, four hourly samplings were carried out at six-day intervals. Samples were analyzed using gas chromatography. Among the VOC species detected are 4 alkanes, 6 aromatic compounds, 4 chlorinated hydrocarbons, and lketone. The results showed that ambient VOC levels in the atmosphere of Benin City are driven by high traffic; hence high concentrations were observed in most traffic junctions sampled. The examination of the average of total VOC accumulation showed significant spatial and seasonal variability (p<0.01) in all sites. The diurnal pattern showed higher concentrations in the morning, and then evening, indicating that fresh emissions impact the air mass in the city. Analyses of the weekly variations of the pollutants showed the weekday's maxima and the weekend's minima, an indication of traffic influence.