Remediation of Cu, Pb, Zn and Cd-contaminated agricultural soil using a combined red mud and compost amendment

Red mud and compost are two inexpensive and effective materials available for the in situ treatment of soil contaminated with heavy metals. In order to investigate the specific process involved, a detailed analysis of the synergistic effects of combined red mud and compost was carried out. The efficiency of three different treatment systems, namely compost (C), red mud (R), and a mixture of compost and red mud (R + C), on the movability, ecological risk, and biological effective Cu, Zn, Cd, and Pb over time of incubation in agricultural soil was evaluated. Results showed that the pH, water extractable organic carbon (WEOC) and total organic carbon (TOC) showed significant changes after addition of these amendment materials to the target soil. The combination of red mud and compost mixture as amendment material (R + C) resulted in the largest reduction in efficiency of the available heavy metals. In addition, the microbial biomass in the treated soil increased after addition of the amendment materials, highest increase was observed with R + C. The results indicate that these amendment materials, especially R + C could lower the ecological risk of heavy metals in soil. (C) 2017 Elsevier Ltd. All rights reserved.