A holistic methodology to study geochemical and geomorphological control of the distribution of potentially toxic elements in soil

Control of Potentially Toxic Elements (PTEs) in soil-polluted areas is needed to address the potential risk that pollution poses to public health and the environment. This study describes an innovative holistic methodology to assess the distribution of PTEs. It is based on the application of multi-variate statistical and geostatistical algorithms, soil pollution indices and geochemical & geomorphological/climate variables (element concentration, watercourses, winds, slope, orientation and visibility). The methodology proposed is exemplified through a comprehensive soil sampling in an area surrounding a former As-Hg mine that presents several sources of pollutants (abandoned mining spoil heaps, metallurgical waste, old chimneys, etc.). Factor analysis identified four main pollutants of concern: Hg, As, Pb and Sb. The mobility of the most abundant PTEs, especially As, and, to a minor extent, Hg, showed a clear influence of climatic/geomorphological variables. Moreover, the pollution indices confirmed that although the soils in the areas around the spoil heaps contain higher concentrations of the pollutants, the influence of the chimneys is present in the whole study area and depends on factors such as orientation and visibility. In contrast, the fingerprint of the spoil heaps showed a PTE distribution more associated with the slope factor and the presence of watercourses eroding the heaps. All things considered, the methodology proposed revealed PTE sources and distribution in a highly complex site and may therefore find application in similar scenarios of contamination.

Automated summary

This study presents an innovative methodology for assessing the distribution of Potentially Toxic Elements (PTEs) in soil-polluted areas, utilizing multi-variate statistical and geostatistical algorithms, soil pollution indices, and geochemical & geomorphological/climate variables. Through comprehensive soil sampling in an area around a former As-Hg mine, factors such as Hg, As, Pb, and Sb were identified as main pollutants of concern, with their mobility influenced by climatic/geomorphological variables. The study also found that pollution from chimneys affects the entire study area, while the distribution of PTEs from spoil heaps is more associated with factors like slope and watercourses.