How does the microenvironment change during the stabilization of cadmium in exogenous remediation sediment?

The pollution degree of heavy metals is closely related to the sediment microenvironment. This study aims to give a comprehensive account of the changes of microenvironment in sediment during the stabilization of cadmium (Cd) by the sodium lignosulphonate (SLS) modified chlorapatites (SLS@nClAP). Chemical speciation change demonstrated that SLS@nClAP possessed better stabilizing capacity (65.84 %-76.66 %) for Cd than unmodified chlorapatites (ClAP) (45.88 %). It might be since that the surface of SLS@nClAP presented a more dispersive thin sheet structure with sulfonate groups compared with the aggregate block structure of ClAP. High-throughput sequencing results displayed that succession of microbial community occurred after remediation in sediment. Most importantly, the dominant genus changed from massilia to phosphate-solubilizing bacterium-pseudomonas which might be due to the remediation of chlorapatites and the stabilization of Cd. Moreover, enzyme activity changes showed that the activity of catalase and urease were highly influenced by the stability and bioavailability of Cd during the incubation. This study not only provided a novel remediation technology for Cd-polluted sediment but also confirmed that the change of microenvironment was closely related to the stability and bioavailability of Cd in sediment.