Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 553, Issue -, Pages 42-51Publisher
ELSEVIER
DOI: 10.1016/j.scitotenv.2016.02.070
Keywords
Phosphogypsum stack; Acid leachates; Contaminant; Restoration; Estuary of Huelva
Categories
Funding
- Government of Andalusia through the research project 'Phosphogypsum: from the environmental assessment as a waste to its revaluation as a resource' [P12-RNM-2260]
- Spanish Ministry of Science and Innovation
- 'Ramon y Cajal Subprogramme' (MICINN-RYC)
- European Union's Seventh Framework Program
- Marie Sklodowska-Curie actions
- Ministry of Economy, Innovation, Science and Employment of the Junta de Andalucia by program TalentHub (COFUND) [291780]
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Phosphogypsum wastes from phosphate fertilizer industries are stockpiled in stacks with high contamination potential. An assessment of the environmental impact, including the use of geochemical tracers such as rare earth elements (REE) and Cl/Br ratios, was carried out in the phosphogypsum stack located at the Estuary of Huelva (SW Spain). Inside the pile, highly polluted acid pore-waters flows up to the edge of the stack, emerging as small fluvial courses, known as edge outflows, which discharge directly into the estuary. The disposal area is divided into four zones; two unrestored zones with surface ponds of industrial process water and two a priori already-restored zones. However, an extensive sampling of edge outflows conducted in the perimeter of the four zones demonstrates the high potential of contamination of the whole stack, including those zones that were supposedly restored. These solutions are characterized by a pH of 1.9 and concentrations of 6100 mg/L for P, 1970 mg/L for S, 600 mg/L for F, 200 mg/L for NH4+, 100 mg/L for Fe, 10-30 mg/L for Zn, As and U, and 1-10 mg/L for Cr, Cu and Cd. Preliminary restoration actions and those planned for the future prioritize removal of ponded process water and cover of the phosphogypsum with artificial topsoil. These actions presuppose that the ponded process water percolates through the porous medium towards the edge up to reach the estuary. However, geochemical tracers rule out this connection and point to an estuarine origin for these leachates, suggesting a possible tidal-induced leaching of the waste pile in depth. These findings would explain the ineffectiveness of preliminary restoration measures and should be considered for the development of new action plans. (C) 2016 Elsevier B.V. All rights reserved.
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