Succession of sulfur-driven phosphorus release mode during malodorous river remediation

The evolution from ‘malodor’ to ‘algae bloom’ in urban rivers has become a new challenge due to relatively high phosphorus levels. Given that sulfur is another vital biogenic element, its involvement in phosphorus cycling deserves attention. Our field study revealed that total phosphorus (TP) levels in overlying water were positively correlated with sulfide before remediation, whereas they shifted to a positive correlation with sulfate after remediation. Subsequently, six sulfur compounds were used to investigate the effects of sulfur forms on phosphorus release. Na₂S, Na₂S₂O₃, and Na₂SO₄ significantly contributed to endogenous phosphorus release, while relatively stable FeS₂, FeS, and S⁰ reduced endogenous phosphorus release. Moreover, varying levels of Na₂S and Na₂SO₄ were further used to explore their effects on the fate of endogenous phosphorus. Results showed that reduced sulfur could directly provide S^2- to bind with metal ions, liberating metal-bound phosphorus into overlying water, as evidenced by a notable reduction (36.32 %-79.91 %) in NaOH-P (representing Fe/Al-bound phosphorus). Differently, the phosphorus release driven by oxidized sulfur involved the participation of microorganisms such as Petrimonas and norank_f_Anaerolineaceae . Additionally, oxidized sulfur facilitated the release of organic phosphorus, as indicated by the increased alkaline phosphatase activity (0.010–0.090 mM·g⁻¹·min⁻¹). The present work can hopefully assist in understanding sulfur-driven endogenous phosphorus release mechanisms as well as addressing the emerging eutrophication problem in remediated urban rivers.