Mineralization of organic matter during the immobilization of heavy metals in polluted soil treated with minerals

Very little attention has been paid to the mineralization of soil organic matter (SOM) during the remediation of soil heavy metal pollution. This study observed SOM mineralization during the remediation of soil heavy metal pollution by treating polluted soil with montmorillonite, birnessite, goethite or ferrihydrite. All examined minerals significantly decreased the availability of both Cu and Cd in soil, the decrease by birnessite was the most significant. Birnessite significantly increased the percentage of reducible fraction of heavy metals. The availability of both Cu and Cd was significantly negatively correlated with the percentage of residual fraction of heavy metals. The mineralization of SOM was facilitated by montmorillonite and birnessite but was decreased by goethite and ferrihydrite. The information indicated that iron oxyhydroxides were promising additives for simultaneously stabilizing both heavy metal and organic carbon in soil. During the remediation of soil heavy metal pollution, the examined minerals regulated SOM mineralization by modulating the abundance and diversity of soil bacterial community, the activity of β-glucosidase, the content and structural complexity of dissolved organic matter (DOM), the content of soil available phosphorous, and soil pH.