Induced reduction of the potential leachability of As, Cd and Tl in an element-spiked acid soil by the application of industrial by-products

A series of incubation and leaching experiments were performed to assess the feasibility of two industrial by-products (phosphogypsum —PG— and sugar foam —SF—, rich in gypsum and calcium carbonate, respectively) to reduce the potential leachability of As, Cd, and Tl in an acidic soil. The effectiveness of the treatments (SF and PG + SF) was evaluated in response to the addition of a chelating agent (DTPA solution) or weak acidification (acetic acid at pH 4.93, TCLP solution) and the resulting sorption mechanisms as a function of treatment was estimated through the application of a sequential extraction procedure. Both amendments induced a significant increment in the soil retention capacity of the three elements. The subsequent leaching tests indicated that those columns treated with SF and PG + SF significantly reduced the amount of element leached regardless the experiments were performed with DTPA or an acidifying solution. The results of the sequential extraction procedure revealed that amending contaminated soils with both SF and PG + SF results in a redistribution of the three toxic elements from soluble and exchangeable pools (FI) to the Al, Fe and Mn (hydr)oxide (FII) fraction Overall, the addition of these amendments to an acid soil contaminated with As, Cd, and Tl reduced their mobility and potential leachability.