Statistical contributions to the study of contamination in abandoned mining areas. The case study of the Vale das Gatas Mine-Portugal.

Abstract

The objective of this work is to apply a selected set of geomathematical models that analyze the relationships between different Potentially Toxic Elements (PTEs) and spatial dispersion in the areas surrounding former abandoned mines. The use of multivariate statistical techniques within the framework of Factorial Methods (Principal Component Analysis and Correspondence Analysis), combined with geostatistical models characterizing the spatial behavior of PTEs, allows not only an environmental diagnosis of the site but also sanctions the evaluation of the potential economic feasibility of the site rehabilitation (through remining or remediation). The Vale das Gatas mine was one of the main centers of tungsten extraction in Portugal, heavily exploited during both World War II and Korean War, given its high economic and strategic value (Ávila, 2003). With the closure of mining operations and the abandonment of mining facilities, the area was neglected, with climatic factors being the main agents of weathering, allowing the continued degradation of exposed materials on the slopes, the waste rocks disposals, and consequent mobilization of potentially toxic elements (PTE) present. As documented by several authors (Almeida et al., 2023; Antunes et al., 2016; Cardenes et al., 2013; Durães et al., 2021; Favas et al., 2017, 2024; Fonseca et al., 2020), contamination in abandoned mining areas represents a significant environmental risk factor, impacting various environmental compartments such as soil, surface and groundwater, atmosphere, sediments and surrounding ecosystems. Keywords: Multivariate Statistics; Geostatistics; Potentially Toxic Elements.