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Non-parametric approach to analysing PAHs data in atmospheric settled particles: Valencia City, Venezuela

Abstract:

Non-parametric statistics and cluster analysis have been found useful to evaluate differences/similarities of PAHs presence/absence in atmospheric settled particles (ASPs) collected on building roofs in Valencia City, Venezuela, as an alternative tool in the study of air pollutants. The sampling focused on variables such as size particles, building heights, location, and sampling months. ASPs were extracted by Soxhlet with dichloromethane. The organic extracts were fractionated by liquid column chromatography, and PAHs were identified by GC-MS. The study used nominal data, and a cluster was built from Jaccard’s matrix. The results show three groups: 1 and 2 correspond to not impacted and poorly impacted zone and group 3 is associated with moderate to strongly impacted zone. The results of chi-square test of independence show that height was related to the number of PAHs detected. Non-parametric and multivariate statistical tools are useful to derive conclusions from categorical data of PAHs.