Occurrence of Polycyclic Aromatic Hydrocarbons in a Wide Variety of Soils Worldwide: a Chemometrical Approach

摘要

Principal component analysis (PCA) was applied to a data set containing the levels of 9 polycyclic aromatic hydrocarbons (PAHs) in 211 soil samples collected from various part of the world. In this way, the soil-distribution patterns of the investigated compounds and the variability amongst the soils from urban, industrial and remote sites were studied. PCA concerned the absolute values of PAHs in soils as well as the soil PAH-profiles illustrating at the same time the application of log-transformations on both kinds of data expression. Considering the individual PAHs, loading plots showed that higher molecular mass compounds (with 5 and 6 benzene rings in molecules) were responsible for the largest variation in data. The obtained results implied that when the absolute values of concentration were concerned, their log-transformation prior PCA was necessary in order to avoid misinterpretation of the data structure imposed by the outliers. However, in the case of the compositional data the outliers did not impair the PCA results as very similar results were obtained for log- and non log-transformed data. The score plots revealed that the PAH contents as well as of PAH profiles of the soils from industrial and remote sites scattered more than for those from urban locations. However, clear gap between the soils from urban, industrial and remote sites was not seen.