Effect of the addition of industrial by-products on Cu, Zn, Pb and As leachability in a mine sediment

► By-products applied in situ stabilize toxic elements in mine sediments. ► Red gypsum, sugar foam and ashes from biomass combustion were used. ► Changes in element solid phase speciation have been evaluated. ► All amendments reduced significantly the leachability of Zn and Cu. ► The treatment with a mixture of by-products also decreased the mobility of As.