Geochemical behaviour and transport of technology critical metals (TCMs) by the Tinto River (SW Spain) to the Atlantic Ocean

Carlos Ruiz Cánovas; María Dolores Basallote; Francisco Macías; Manuel Olías; Rafael Pérez-López; Carlos Ayora; José Miguel Nieto

doi:10.1016/j.scitotenv.2020.143796

Geochemical behaviour and transport of technology critical metals (TCMs) by the Tinto River (SW Spain) to the Atlantic Ocean

Sci Total Environ. 2021 Apr 10:764:143796. doi: 10.1016/j.scitotenv.2020.143796. Epub 2020 Dec 24.

Authors

Carlos Ruiz Cánovas¹, María Dolores Basallote², Francisco Macías², Manuel Olías², Rafael Pérez-López², Carlos Ayora³, José Miguel Nieto²

Affiliations

¹ Department of Earth Sciences and Research Center on Natural Resources, Health and the Environment, University of Huelva, Campus 'El Carmen', Fuerzas Armadas s/n, 21071 Huelva, Spain. Electronic address: carlos.ruiz@dgeo.uhu.es.
² Department of Earth Sciences and Research Center on Natural Resources, Health and the Environment, University of Huelva, Campus 'El Carmen', Fuerzas Armadas s/n, 21071 Huelva, Spain.
³ Institute of Environmental Assessment and Water Research, CSIC, Jordi Girona 18, 08034 Barcelona, Spain.

PMID: 33387768
DOI: 10.1016/j.scitotenv.2020.143796

Abstract

This paper addresses the behaviour of several technology critical metals (TCMs), i.e., rare earth elements (REEs), Y, Sc, Ga and Tl, in the Tinto River (SW Spain), quantifying their fluxes to the Atlantic Ocean and unravelling the governing geochemical processes controlling their solubility. To accomplish this goal, a high-resolution (2-24 h) sampling was performed during the hydrological year 2017/18. Mean dissolved concentrations of 380 μg/L of REE, 99 μg/L of Y, 15 μg/L of Sc, 9.2 μg/L of Ga and 4.8 μg/L of Tl were found. Most TCMs followed a behaviour similar to that of sulphate and base metals throughout the year, exhibiting a quasi-conservative behaviour due to acidic conditions. However, dissolved Tl concentrations seem to be strongly controlled by Tl incorporation onto secondary minerals and diatoms deposited on the riverbed, especially during the dry season. The remobilization of riverbed sediments led to the transport of significant amounts of TCMs associated with particulate matter, especially Al oxy-hydroxy-sulphates or Al-silicates rather than Fe precipitates (except for Tl and Ga). Around 5.8 t of REE, 1.3 t of Y, 248 kg of Sc, 139 kg of Ga and 138 kg of Tl were delivered annually in their dissolved forms by the Tinto River to the Atlantic Ocean, which constitutes around 0.09% of the dissolved global flux into the oceans of Y, 0.02% of the REE flux, 0.01% of the Ga flux and 0.001% of the Sc flux.

Keywords: Acid mine drainage (AMD); Gallium; Global metal fluxes; Rare earth elements (REEs); Thallium.