Simultaneous elimination of black-odor and stabilization of heavy metals in contaminated sediment using calcium peroxide/hydroxyapatite: Microbial responses and ecotoxicological effects

In this study, laboratory-scale experiments were conducted to investigate the feasibility of the combined use of calcium peroxide and hydroxyapatite (CaO₂/HAP) for simultaneous black-odor sediment remediation and heavy metal stabilization. The ecotoxicological effects of remediated sediment were also evaluated based on biological toxicity. Results showed that CaO₂/HAP effectively eliminated the black-odor and simultaneously stabilized heavy metals in the sediment. Under the optimal dosage ratio of CaO₂/HAP (1:2), the acid volatile sulfides decreased to approximately 20 mg/kg (dry weight, dw) and oxidation-reduction potential increased from − 165 mV to approximately − 90 mV. The leaching of heavy metals meets the strictest standards (Level I) of the “Technical Specification for Output Disposal of Contaminated Sediment Treatment Plant of River and Lake” (SZDB/Z 236-2017). The indigenous microbial community succession occurred (p < 0.01), Proteobacteria and Firmicutes accounting for 75.54% and 20.19%, respectively, were the predominant bacteria in the remediated sediment. Additionally, CaO₂/HAP remediated sediments were safer and more environmentally friendly than raw sediments, and were not biotoxic to the benthic environment (p < 0.01). This study provides new insights into the combined use of the beneficial amendments remediating heavy metal-contaminated black-odor river sediment.