Evaluation of the Effects of Different In-Situ Passivation Materials on Heavy Metal Remediation in Corn Fields in Arid Regions of Northwest China

The research on cadmium (Cd) pollution remediation technologies in farmland is of great significance for ensuring food security. However, there is currently a lack of empirical research on the passivation effects of the related repair materials on alkaline farmland in arid regions. This study selected a typical experimental area in a dryland corn farmland in Ningxia, Northwest China. Field experiments were conducted on four typical remediation materials: mercapto clay minerals, sepiolite remediation materials, microbial inoculants, and bio-organic fertilizers. The effects of these four materials on the available cadmium in the soil, cadmium content in corn stems and leaves, and enrichment coefficients were analyzed. The results show that the four types of remediation fertilizers have significant differences in their effects on the available Cd content in the soil, with a reduction range of 3.33–60.94%. The order of the inhibitory effect from strong to weak is as follows: mercapto clay mineral passivation material, bio-organic fertilizer, sepiolite, and microbial inoculant. The cumulative distribution pattern of Cd in the organs of corn plants is leaf > stem > grain. It reduces the cadmium content in corn stems by 7.01–37.16% and reduces the cadmium content in corn leaves by 1.45–26.56%. Under the four types of remediation fertilizer treatments, the enrichment coefficients of corn stems and leaves all decreased. The enrichment coefficient of stems decreased by 3.78% to 29.42%, and the enrichment coefficient of leaves decreased by 3.41% to 31.92%. The mercapto clay minerals passivation material has the best effect on reducing the available cadmium in the soil of dryland corn in the arid areas of Northwest China and also has the best effect on inhibiting the absorption of cadmium by various organs of corn. It can be further verified in the field and promoted for application, providing support for the restoration of heavy metal pollution in farmland based on local conditions and differentiated measures.