Abstract

To immobilize the activity and bioavailability of soil Cd, the single treatment only flooding (F) and the combined treatments with flooding plus bauxite residue (F-B) or lime (F-L) were designed to investigate the impacts of different treatments on the toxicity and bioavailability of Cd in contaminated soil. Compared with the single treatment (F), the combined treatments (F-B and F-L) improved soil-associated organic functional groups and aggregated stability in soil. The average particle sizes of soil aggregates increased from 126 nm (F-treated soil) to 256 and 270 nm following F-B and F-L treatments, respectively. Relative to F treatment, the combined treatments (F-B and F-L) increased soil pH, soil EC, and residual Cd content in soil and reduced exchangeable Cd and acid-soluble Cd content in soil. The exchangeable Cd contents in soils were decreased to 3.17 and 3.42 mg/kg following F-B and F-L treatments in comparison with F-treated soils (4.31 mg/kg), respectively. For the soils with F-B and F-L treatments, soil residual Cd contents increased from 54% (F treatment) to 57 and 56%, respectively, and soil acid-soluble Cd contents decreased from 46% (F treatment) to 37 and 43%, respectively. A negative correlation was found in soil pH versus soil exchangeable Cd and soil acid-soluble Cd. In addition, the F-B treatment exhibited superiority in suppressing toxicity and bioavailability of soil Cd, owing to that F-B treatment is easy to induce neutralization reaction and immobilization effect in contaminated soil. The findings offer evidences that F-B treatment is a facile approach to suppress toxicity and bioavailability of soil Cd, which shows potential for immobilization of Cd in soil.