The rebound of black-odorous occurred in organic-rich sediments has become a critical issue due to its great harm to the ecological environment. Elements such as S, C, and N play a crucial role in the biogeochemical cycle of black-odorous rivers. As electronic acceptors, Ca(NO3)2 and CaO2 can effectively remove acidified volatile sulfide (AVS) and organic matter to control the black-odorous rebound. However, the remediation mechanisms in organic-rich sediments by Ca(NO3)2 and CaO2 are unclear. The present study explored the mechanism of C-N-S interconnection degradation in organic-rich urban river sediments by adding different ratios and sequences of Ca(NO3)2 and CaO2. The results showed that Ca(NO3)2 remediation followed by CaO2 and the accepted electron ratio 1:1 of Ca(NO3)2 to CaO2 is an effective method for controlling the rebound of black-odorous and reducing the accumulation NO2--N. Mainly attributed to that, CaO2 enhanced the degradation of organic matter by stimulating enzymatic activities in the sediments, which is also the main reason for controlling the rebound of black-odorous. Since CaO2 releases O2 and •OH, which inhibit nosZgenes, NO2--N accumulates when remedied simultaneously with Ca(NO3)2 and CaO2. Co-occurrence network analysis illustrated that sulfur-driven autotrophic denitrification bacteria, heterotrophic denitrifying bacteria, and sulfate-reducing bacteria interact strongly inside one module, clarifying a solid interaction of C-N-S substances among these bacteria. Our results reveal the C-N-S interconnection degradation mechanism and provide a new perspective on applying biochemical remediation in organic-rich urban river sediments.
Keywords: Acid volatile sulfide; Co-occurrence network; Extracellular enzymes; Functional gene; Microbial community.
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