No abstract

Creation of Technosols with the use of different materials is a sustainable strategy to reclaim mine tailings and reduce metal mobility. For this purpose, a short‐term incubation experiment was designed with biochars derived from pig manure, crop residues and municipal solid waste added to tailings alone or in combination with marble waste. We aimed to assess the efficiency of the different amendments to decrease Cd, Pb and Zn availability in the Technosols and the fractions where metals were retained. Results showed that all amendments reduced metal mobility, directly related to increases in pH. Those materials with higher content of carbonates were more effective to immobilize metals (~99%). Municipal solid waste was highly effective to decrease metal mobility owing to the higher carbonate content, but addition of marble waste was needed to enhance metal immobilization with pig manure and crop residue. Decreases in Cd mobility were related to retention by the carbonate, Mn/Fe oxides and oxidizable (organic compounds) fractions. Decreases in Pb mobility were related to retention in the Mn/Fe oxides and residual fractions, while decreases in Zn mobility were related to retention in Mn/Fe oxides and oxidizable fractions. Association of Zn and Pb with the oxidizable fraction was also related to the recalcitrance of the organic compounds and so dependent on biochar type. Scanning electron microscopy coupled with energy dispersive X‐ray showed that biochar showed great affinity to interact with iron oxides, calcium sulfates and phyllosilicates. Copyright © 2017 John Wiley & Sons, Ltd.

Phosphorus (P) is one of the primary nutrients limiting crop production. The application of phosphate fertilizers in acidic soils leads to the formation of secondary insoluble compounds that reduces the effectiveness of the fertilizer. The addition of biochar may represent a solution to the problem of nutrients bioavailability, especially P. In this study, tests were performed to determine the effects of amending soil with five different percentages of biochar (0, 5, 10, 20, and 35% w/w) on the phenomena of P sorption and desorption. The effect of soil/ biochar contact treatments on P availability was also examined. Phosphorus sorption was lower in the soils containing biochar compared to normal soil. The accumulated desorption quantity after eight consecutive extractions was 85% higher when 35% biochar was added to the soil than soil alone. Moreover, the application of 35% biochar increased the concentration of soluble P up to 38% after 30 days of incubation. Based on these results, we deduced that biochar induces changes in P retention soil properties that may be beneficial for agricultural soils.