Effects of different passivators on heavy metal contaminated soil

Aiming to screen materials with better passivation effects, we used indoor simulated cultivation and studied the effects of rape straw biochar, capture agent TMT, mixed passivator containing sulfhydryl group and sodium sulfide on the contents of Cd and Pb in the soil as well as the physical and chemical properties of the soil under different cultivation times and dosages. The results showed: (1) The effects of the three passivating agents on the soil pH were mainly manifested in the early 15 days after the cultivation, while the pH tended to be stable at the later period. The capture agent increased the soil pH by 1.61 units, with the most effect. (2) The three passivating agents were with significant passivation effects on Cd and Pb. Among them, mixed passivator was with the most passivation effect on available Cd and Pb, with 44.9% and 29.0% of the passivation rates, respectively. (3) The contents of available Cd and Pb in soil were negatively correlated with soil pH. (4) Biochar and capture agent significantly improved soil organic matter and available phosphorus contents; while mixed passivator significantly increased the contents of soil organic matter, available nitrogen, available phosphorus and available potassium, with the most effect. The passivation agent mixed passivator significantly reduces the contents of available Cd and Pb in the contaminated soil and improves the soil physical and chemical properties, with the best passivation effect.