Abstract:

To explore the suitable passivation materials for ameliorating the farmland polluted by both cadmium and arsenic, pot experiments were carried out to compare the effects of five passivation materials on the reduction of cadmium and arsenic in rice grain. The materials included red mud, red mud + iron powder, basalt red mud + limestone powder, limestone powder + iron powder and limestone powder + biochar + ferrous sulfate. The experimental results showed that all of the five passivation materials could change the chemical forms of Cd and As in the soil, and reduce the bioavailability of Cd and As in the soil and contents of Cd and As in rice grain. On the whole, three kinds of compound passivation materials, red mud + iron powder, limestone powder + iron powder and limestone powder + biochar + ferrous sulfate, had the most obvious effect, which could reduce Cd and As in the grain by 58%-63% and 56%-67%, respectively. Under the experimental conditions, the five passivation materials did not lead to a significant decline in soil quality. The application of the passivation materials containing limestone powder and biochar was also conducive to reducing soil acidity, increasing soil organic matter and cation exchange capacity. Based on the comprehensive effect, red mud + iron powder is considered as an ideal passivation material for the treatment of Cd and As compound pollution of farmland soils.

Key words: passivation materials, cadmium, arsenic, compound pollution, agricultural product safety, red mud, iron powder, soil remediation, rice safety