Spatiotemporal evolution of U and Th isotopes in a mine effluent highly polluted by Acid Mine Drainage (AMD)

J L Guerrero; N Suárez-Vaz; D C Paz-Gómez; S M Pérez-Moreno; J P Bolívar

doi:10.1016/j.jhazmat.2023.130782

Spatiotemporal evolution of U and Th isotopes in a mine effluent highly polluted by Acid Mine Drainage (AMD)

J Hazard Mater. 2023 Apr 5:447:130782. doi: 10.1016/j.jhazmat.2023.130782. Epub 2023 Jan 11.

Authors

J L Guerrero¹, N Suárez-Vaz², D C Paz-Gómez³, S M Pérez-Moreno⁴, J P Bolívar⁵

Affiliations

¹ Department of Integrated Sciences, Center on Natural Resources, Health and the Environment (RENSMA), University of Huelva, Campus El Carmen, 21071, Huelva, Spain; Department of Earth Sciences, Center on Natural Resources, Health and the Environment (RENSMA), University of Huelva, Campus El Carmen, 21071, Huelva, Spain. Electronic address: joseluis.guerrero@uhu.es.
² Department of Integrated Sciences, Center on Natural Resources, Health and the Environment (RENSMA), University of Huelva, Campus El Carmen, 21071, Huelva, Spain. Electronic address: nuria.suarez@alu.uhu.es.
³ Department of Integrated Sciences, Center on Natural Resources, Health and the Environment (RENSMA), University of Huelva, Campus El Carmen, 21071, Huelva, Spain. Electronic address: daniela.paz@dci.uhu.es.
⁴ Department of Integrated Sciences, Center on Natural Resources, Health and the Environment (RENSMA), University of Huelva, Campus El Carmen, 21071, Huelva, Spain. Electronic address: silvia.perez@dci.uhu.es.
⁵ Department of Integrated Sciences, Center on Natural Resources, Health and the Environment (RENSMA), University of Huelva, Campus El Carmen, 21071, Huelva, Spain. Electronic address: bolivar@uhu.es.

PMID: 36641853
DOI: 10.1016/j.jhazmat.2023.130782

Abstract

The spatiotemporal evolution of both U and Th isotopes in a mine effluent highly polluted by acid mine drainage (AMD) was evaluated. The acidic tributary, which born from the outflows of an abandoned sulfide mine, flows into the Odiel River. AMD comprises an important source of natural radionuclides, presenting concentrations of ²³⁸U and ²³²Th, two and four orders of magnitude higher, respectively, than the background values of surface continental waters. These natural radionuclides behave conservatively along the mine effluent (pH < 2.5) throughout the hydrological year. Under AMD conditions uranium is in the hexavalent state U(VI) and the main dissolved species are uranyl sulfate complexes. The polluted tributary has a significant impact on the Odiel River acidifying its waters during the low flow season and increasing up to one order of magnitude the activity concentrations of U and Th isotopes. U presented a conservative behavior in the Odiel River during the low flow season (pH ≈ 3), however it is removed from the liquid phase in the wet season (pH ≈ 6), probably due its coprecipitation/adsorption onto Al-phases. Th shows a high sensitivity to small increases of pH, and it is strongly coprecipitated/adsorbed with or onto Fe-oxyhydroxydizes in the river.

Keywords: Acid mine drainage; Conservative behavior; Environmental impact; Th isotopes; U isotopes.