The Influence of Red Mud, Bone Char and Lime on Uptake and Accumulation of Pb, Zn and As by Maize (Zea mays) Planted in Contaminated Soil

The effect of red mud, bone char and lime on the uptake and accumulation of lead (Pb), zinc (Zn) and arsenic (As) by maize planted in soil contaminated by heavy metals was studied. Five different treatments were designed: control, 5% red mud, 5% bone char, 5% lime, and 2.5% red mud + 2.5% bone char by weight. The maize was harvested 8 weeks after planting, and the concentrations of Pb, Zn, and As in the shoots and roots, as well as the amount of heavy metals in the soil that was available for uptake, was measured. The results showed that the different amendments could all increase the shoot biomass significantly, with the largest increase by the 5% bone char treatment. The amendments decreased the concentration of Pb and Zn in the shoots by 70.9-89.1% and 78.3-89.7%, and in root by 50.0-67.5% and 91.0-94.3%, respectively, compared with the control. The effect of the amendments differed on the concentration of As in maize compared to the control. As concentrations in both the shoots and root decreased significantly when treated with 5% red mud and 2.5% red mud + 2.5% bone char, while the concentrations increased markedly when treated by 5% bone char and 5% lime. The applications of different amendments decreased the amount of Pb and Zn in soils that was available for uptake by plants, but increased the availability of As. The results indicated that red mud, bone char and lime are potential amendments for modifying acidic soil contaminated by heavy metals.