A multitechnique approach for the identification of multiple contamination sources near a polluted industrial site

Degraded land requires rapid and suitable remedial actions, thus appropriate and fast methodological approaches for estimating the spatial distribution of contaminants are needed. In this context, a methodological approach combining isotopic measurements, heavy metals concentrations mapping, X-ray diffraction, and cluster analysis, was applied to characterize a polluted industrial site where the contamination due to improper waste disposal could have spread also into the surrounding fields. This approach was applied to a set of representative topsoil (from 15 to 30 cm depth) and subsoil (from 130 to 150 cm depth) samples, selected either inside or outside the contaminated site. The X-ray diffraction analysis highlighted that only the mineralogy of the subsoil below the buried waste was noticeably altered, while the concentration mapping highlighted that the levels of several heavy metals on the edge of the contaminated site, at both depths, were very similar to those found in the samples from the outside. Based on these findings, Pb was used as a tracer for heavy metal pollution by its stable isotopes' analysis. The cluster analysis of the isotopic measurements revealed that only the contamination detected inside the industrial site could be attributed to the pollutants migration from the buried waste. Conversely, the contaminants concentrations found in the topsoil samples taken outside the site could be ascribed to contamination sources other than the polluted waste present inside the site.