Multivariate Statistical Study of Spatial Patterns of Volatile Organic Compounds in an Urban Atmosphere in Nigeria

摘要

In complex environment of an urban atmosphere, variability in concentrations of pollutants from site to site within a city is often observed, hence there is need to investigate the quality parameters responsible for the variations. For this purpose, ambient VOCs (volatile organic compounds) measured on four hourly bases at different days of the week and at six days interval in Benin City, southern Nigeria were collected (from June 2009 to May 2010) at nine different microenvironments, selected to represent local activities in the city. The samples were collected at the breathing zone of 1.5meter height, extracted with carbon disulphide and were analyzed using gas chromatographic system. A total of 15 VOCs were captured during sampling period at nine urban sites and among the VOCs species detected are four alkanes, six aromatic compounds, four chlorinated hydrocarbons and one ketone. To determine the patterns of VOCs, multivariate analysis of variance (MANOVA) and factor analysis techniques were applied for evaluation of spatial variation and interpretation of complexity of data in the urban atmosphere. The result showed that the nine sites are significantly different in terms of total VOC concentrations. Factor analysis (FA) results revealed that six factors explained 95.00% of the total variance while spatial Discriminate Analysis (DA) showed that seven discriminate function (DFs) were found to discriminate the nine sites. Wilk”s Lambada test showed that only the first two functions are statistically significant. The present study shows the usefulness of multivariate statistical techniques for analysis and interpretation of complex data sets, and identifies probable source components in order to explain the atmospheric behaviors of pollutants.