Spatial and temporal variability of volatile organic compounds (VOCs) pollution in Apapa industrial areas of Lagos state, southwestern-Nigeria

The results of temporal and spatial distribution of volatile organic compounds in ambient air in Apapa Industrial Area during May, 2010 to April, 2011 are presented. This results were analysed in other to present information about the detailed nature of air quality situation in the sampled areas. The air samples were collected by passive sampler (ORSA 5) . The air samplers were exposed to a height of 1.5 - 2.0 m and sampling was carried out four times a month for a period of 12 months. The adsorbed VOCs were desorbed with carbondisulphide (CS2) and the solution analysed using Gas Chromatography (GC) fitted with Flame Ionization Detector (FID). The results from analysis of the air samples collected showed that twenty (26) VOCs were captured. The VOCs were classified thus: aromatics 43%, halogenated 28%, esters 4%, ketones 13%, alcohols 6 %, ethers 6%. There is a significant difference (Pvalue < 0.05) between the levels of VOCs in Apapa. Despite a Comparatively higher concentrations of VOCs at the studied sites, there is a significant difference in the spatial distribution. At a lower wind speed, the VOCs concentrations tend to increase and become uniformly distributed around the Industrial Areas. The temporal distribution shows a decrease in ambient concentrations of VOCs from May to July due to Atmospheric( dilution) wash down by rain. The results of two - ways factor ANOVA analysis of the monthly average of total volatile organic compounds revealed that there is significant difference ( Pvalue < 0.05) in temporal and spatial variations of TVOC concentrations in the studied areas. The meteorological parameters showed significant correlations with the ambient concentrations of VOCs. The principal component analysis revealed that the major sources of VOCs in Apapa are mainly Anthropogenic and three (3) factors were identified as sources of VOCs in the studied area with Industrial and emissions from traffic dominating.

Author(s): Ojiodu C. C., 2J. M. Okuo and 3E. G. Olumayede

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