A multivariate approach for anomaly separation of potentially toxic trace elements in urban and peri-urban soils: an application in a southern Italy area.

Geogenic soil enrichment and anthropogenic pollution by potentially toxic trace elements (PTEs) are two processes acting together. Although it is often difficult, it is necessary to separate the two processes for risk assessment and understanding the environmental implications. The aim of this study was to analyse the soil concentrations of various PTEs in a southern Italy area in order to: (1) determine their different correlation structure to isolate sources of variation acting at different spatial scales and (2) to define potential anomalies based on the correlation structure. In the urban and peri-urban area of Cosenza-Rende, 149 topsoil samples were collected (0.10 m) and analysed for different elements by X-ray fluorescence spectrometry. Principal component analysis and factorial kriging analysis were used to map the spatial distribution of PTEs in topsoil and to identify the main factors influencing their spatial variability. Two groups of PTEs were identified: the first group included As, Pb and Zn; and the second one Al, Co, Cr, Fe, La, Nb, Ni, Ti and V. The first group was related to anthropogenic causes, while the second one was more related to parent rock composition. The regionalized factors at different scales of variability allowed to aggregate and summarize the joint variability in the PTEs and consider the probable causes of soil pollution. The study allowed analysing and quantifying the sources (environmental or anthropogenic) of variation of PTEs acting at different spatial scale and defining the spatial anomalies based on the correlation structure associated at the different spatial scales.