Correlation between Geochemical and Multispectral Patterns in an Area Severely Contaminated by Former Hg-As Mining

Abstract

In the context of soil pollution, plants suffer stress when exposed to extreme concentrations of potentially toxic elements (PTEs). The alterations to the plants caused by such stressors can be monitored by multispectral imagery in the form of vegetation indices, which can inform pollution management strategies. Here we combined geochemistry and remote sensing techniques to offer a preliminary soil pollution assessment of a vast abandoned spoil heap in the surroundings of La Soterraña mining site (Asturias, Spain). To study the soil distribution of the PTEs over time, twenty-seven soil samples were randomly collected downstream of and around the main spoil heap. Furthermore, the area was covered by an unmanned aerial vehicle (UAV) carrying a high-resolution multispectral camera with four bands (red, green, red-edge and near infrared). Multielement analysis revealed mercury and arsenic as principal pollutants. Two indices (from a database containing up to 55 indices) offered a proper correlation with the concentration of PTEs. These were: CARI2, presenting a Pearson Coefficient (PC) of 0.89 for concentrations >200 mg/kg of As; and NDVIg, PC of −0.67 for >40 mg/kg of Hg. The combined approach helps prediction of those areas susceptible to greatest pollution, thus reducing the costs of geochemical campaigns.

Analysis of the airborne mercury and particulate arsenic levels close to an abandoned waste dump and buildings of a mercury mine and the potential risk of atmospheric pollution

“…The predominant minerals are cinnabar (mercury sulfide), realgar (arsenic sulfide), and in smaller proportion oropiment (another arsenic sulfide). There are also arsenopyrite, marcasite, and pyrite hosted in fractured limestones and shales [6]. The gangue is composed of carbonates, quartz, and argillaceous minerals (kaolinite and dickite) [7].…”

Empirical Model of Gaseous Mercury Emissions for the Analysis of Working Conditions in Outdoor Highly Contaminated Sites

“…The predominant minerals are cinnabar (mercury sulfide), realgar (arsenic sulfide), and, in smaller proportion, orpiment (another arsenic sulfide). Arsenopyrite, marcasite, and pyrite are also hosted in fractured limestones and shales [36]. The gangue is composed of carbonates, quartz, and argillaceous minerals (kaolinite and dickite) [10].…”

High‐resolution mapping of soil pollution by Cu and Ni at a polar industrial barren area using proximal and remote sensing

“…Portable X‐ray fluorescence (pXRF) spectrometry provides an opportunity to measure the bulk concentration of PTEs in the field with minimal sample preparation and relatively high accuracy (Qu et al, 2019; Sacristán et al, 2016; Xia et al, 2019). Unmanned aerial vehicles (UAV) with multispectral and hyperspectral cameras enable direct (through spectral properties of polluted soils) and indirect (through the spectral signatures of pollution‐induced constrains for the vegetation growth) (Gholizadeh & Kopačková, 2019) mapping of the PTE contents in soils (Boente et al, 2020; Tan et al, 2020). Given the quasi‐complete absence of vegetation (ca.…”