Pollutant flows from a phosphogypsum disposal area to an estuarine environment: An insight from geochemical signatures

• Published in: The Science of the total environment 2016-05, Vol.553, p.42-51
• Main Authors: Pérez-López, Rafael, Macías, Francisco, Cánovas, Carlos Ruiz, Sarmiento, Aguasanta Miguel, Pérez-Moreno, Silvia María
• Format: Article
• Language: English
• Subjects: Acid leachates; Calcium Sulfate - analysis; Contaminant; Environmental Monitoring; Estuaries; Estuary of Huelva; Fertilizers; Industrial Waste - analysis; Phosphogypsum stack; Phosphorus - analysis; Restoration; Water Pollutants, Chemical - analysis
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2016.02.070

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 6100mg/L for P, 1970mg/L for S, 600mg/L for F, 200mg/L for NH4+, 100mg/L for Fe, 10–30mg/L for Zn, As and U, and 1–10mg/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. [Display omitted] •Acidity and contaminants from phosphogypsum leaching are released to an estuary.•Already-restored zones act as a pollution source just as unrestored zones.•Cl/Br ratios and REE patterns were suitable to assess the restoration inefficiency.•Changes in the remediation strategies of the phosphogypsum stack are hence necessary.