[Analysis of Soil Property Factors Restricting the Remediation Effect of Passivators on Arsenic and Cadmium Pollution in Purple Soil].

The effect of passivating agents on Cd and As is closely related to soil properties. Optimizing passivating agents that adapt to soil properties is the key basis for the application of passivation technology. This study uses eight types of purple soils with widely different properties as test soils, uses indoor culture experiments, sets different pollution conditions, and simultaneously compares the passivation rates of cadmium （Cd） and arsenic （As） by seven common passivators. Additionally, combined with the measurement of soil physical and chemical properties, the relationship between passivation efficiency and soil properties was explored. The results showed that among the seven common passivators tested, calcium oxide, organic fertilizer, silicon calcium magnesium fertilizer, humic acid, and hydroxyapatite had a significant passivation effect on purple soil Cd, and iron oxide, silicon calcium magnesium fertilizer, hydroxyapatite, and humic acid had a passivating effect on As. Only three passivating agents, calcium silicon magnesium fertilizer, hydroxyapatite, and humic acid, had a passivating effect on both Cd and As. Great differences exist in the key soil property factors that determined the passivation efficiency of specific passivators： soil organic matter, clay content, and total potassium were significantly positively correlated with the passivation rate of soil Cd by the tested passivators； soil pH, free iron oxide, free manganese oxide, and total phosphorus were significantly negatively correlated with them； soil CEC, free manganese oxide, and soil total As were significantly positively correlated with the As passivation rate of the tested passivators； and the content of soil clay particles was significantly negatively correlated with it. The study established the optimal multiple linear regression model between the passivation efficiency of passivating agents Cd and As and the soil properties and pollution characteristics of purple soil. The model quantitatively reflects the relationship between the passivation efficiency of heavy metals and soil properties and can be used to predict and optimize adaptation accordingly. Highly efficient passivators with different soil properties provide a scientific basis for the safe use of regionally contaminated farmland.