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.
Highlights
Mining and industrial activities commonly release contaminants, which in turn affect the quality of environmental compartments [1,2]
In the case of mining activities in hilly regions and subsequent waste disposal, residues are exposed to hard weathering and a challenging geomorphology
Pollutants can be widely dispersed, and the costs and uncertainties of geochemical campaigns may be very high [6]. Given these considerations and in the context of soil pollution studies, there is a need to find appropriate non-invasive approaches that reduce the cost and time required for these campaigns
Summary
Mining and industrial activities commonly release contaminants, which in turn affect the quality of environmental compartments [1,2] In this regard, pollution has been reported in urban zones [3,4] and in more rural or natural areas, where the quality of sensitive ecosystems is being seriously compromised [5]. Data are gathered through measurements of electromagnetic reflectance and different frequencies [30] Within this discipline, UAVs are one of the supports used for the development of remote sensing tools for soil applications, with most of the required information being collected by means of optical sensors, which have been recently used in geological applications [31,32]
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