Evaluation of the application of dry covers over carbonate-rich sulphide tailings

► The pH range 7-9 is optimal for elements to precipitate as hydroxide or carbonate. ► High pH in tailings (>11) will increase the oxidation and weathering of tailings. ► Elements such as Cd, Cu, Mn, Pb and Zn will be mobilized at pH > 11. ► Dry cover consisted of paper mill sludge and fly ash is good as a sealing layer.