Unveiling the combined effects of water management and lime on remediation of Cd-contaminated soils with improved soil quality
Tao Tian, Le Yu, Ruixin Feng, Chuangye Yao, Liao‐Kuo Gong, Haifeng Xiao, Lu Liu, Feng Li
Abstract
Suppression of bioavailability and toxicity of Cd is a unique strategy to weaken environmental risks and health hazards in Cd-contaminated soils. Herein, the single treatment only water management of moisture (M) and the combined treatments with moisture plus bauxite residue (M-B)/lime (M-L) were designed to investigate the influence of different treatments on the bioavailability and toxicity of Cd in contaminated soils. Compared with the M treatment, the combined treatments (M-B and M-L) increased soil pH and reduced exchangeable Cd concentration and acid-soluble Cd proportion. The exchangeable Cd concentrations in soils were 4.65, 4.02, and 3.76 mg/kg following M, M-B, and M-L treatments after 1 month, respectively. Also, the proportions of residual Cd were 52.05 %, 57.16 %, and 63.76 % following M, M-B, and M-L treatments, respectively, and the acid-soluble Cd proportions were 44.98 %, 37.62 %, and 29.99 %, respectively. Soil pH versus exchangeable Cd (acid-soluble Cd) of soils presented a negative correlation. In addition, M-B and M-L treatments enhanced the amounts of soil-associated organic functional groups and soil aggregate stability. The average particle sizes of soil aggregates increased to ∼245 nm (M-B) and ∼295 nm (M-L) relative to ∼120 nm of M treatment. Specifically, M-L treatment exhibited superiority in suppressing bioavailability and toxicity of Cd in soils with improved soil quality, owing to that M-L treatment is conductive to trigger neutralization reaction, immobilization effect, and soil-aggregate evolution. The findings offer an evidence that M-L treatment is a facile approach to suppress bioavailability and toxicity of Cd in soils with improved soil quality, which shows promising applications for remediation of Cd-contaminated soils.