Optical study of soil samples contaminated by heavy metals from the São Domingos Mine (Mértola, Portugal)

Abstract

The study of soils contaminated by heavy metals (HMs) is a hard task that implies the collecting of soil samples in an area representative of the contaminated space. For example, for water samples, the law requires the creation of a study grid with 5 ha spacing. Considering this spacing requirement, to the soil from the São Domingos Mine, that have an area of approximately 2000 ha, we need to collect 400 samples. This is an expensive task, but is necessary to quantify the contam-ination, and while recovery actions are being applied, more soil analysis is needed to control the evolution of the contam-ination. In this frame, we present here the project INCOME (Instru-ments for managing areas contaminated by metals) that pro-poses the creation of an environmental management model for mining areas contaminated by HMs. This model integrates the results of the application of a set of analytical methods and instruments for monitoring contaminated areas, such as biophysical analyses, soil, and water chemistry, geophysics, and satellite hyperspectral remote sensing. The resulting da-taset will be used as inputs to artificial intelligence (AI), aim-ing to create contamination models using less on field obser-vations than the standard methodologies. The optical characterization of the mining heap using satellite data available from the Copernicus program (EU Space Pro-gram) allows extracting information about the surface to make the correspondence with HMs. As a step prior to studying the hyperspectral satellite data, it is necessary to carry out an optical study of soil samples col-lected at the site, using portable devices. The first results of the project, namely the identification of HMs spectral features within the collected samples, are presented and discussed.

Funding: The work was supported by the Portuguese Founda-tion for Science and Technology (FCT) by the projects UIDB/04683/2020 - ICT (Institute of Earth Sciences). Ac-knowledgment: Promove Program of the “la Caixa” Founda-tion, in partnership with BPI and the Foundation for Science and Technology (FCT), in the scope of the project INCOME – Inputs para uma região mais sustentável: Instrumentos para a gestão de zonas contamina-das por metais (Inputs for a more sustainable region: Instru-ments for managing metal-contaminated areas), PD23-00013.