Fluctuating pH conditions can affect heavy metal mobility, thereby limiting the efficiency of biofiltration systems (BS). To address this, we developed an innovative rhizosphere sponge, biochar-based bioreactor (RBB), designed to stabilize Cd2+ removal across a pH range of 5 to 9. RBB consistently outperformed the control, achieving a notable 91.3 % Cd2+ removal at pH 5. By creating optimized oxygen and redox zoning, the rhizosphere sponge enhanced both biochar surface reactions and microbial activity. Under acidic conditions, biochar facilitated Fe2+/Mn2+ precipitation into stable (oxy)hydroxides, a process further driven by microbial oxidation. Consequently, RBB accumulated 1.54 times more Fe-Mn oxide-bound Cd than the control, effectively reducing Cd2+ mobility. Additionally, loosely bound extracellular polymeric substances claimed preferential Cd2+ sequestration after acidification. The stabilized microecology and increased ecological niches, allowing RBB to better buffer against pH fluctuations, presenting it as a robust solution for sustainable heavy metal remediation in variable environments.

中文翻译：

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利用根际海绵平滑 pH 值波动并稳定生物过滤系统中的污染物滞留


波动的 pH 条件会影响重金属的迁移率，从而限制生物过滤系统 （BS） 的效率。为了解决这个问题，我们开发了一种创新的根际海绵，即基于生物炭的生物反应器 （RBB），旨在在 5 至 9 的 pH 值范围内稳定 Cd2+ 的去除。RBB 的性能始终优于对照，在 pH 5 时实现了 91.3% 的 Cd2+ 去除率显著。通过创造优化的氧和氧化还原分区，根际海绵增强了生物炭表面反应和微生物活性。在酸性条件下，生物炭促进 Fe2+/Mn2+ 沉淀成稳定的（氧）氢氧化物，这一过程进一步由微生物氧化驱动。因此，RBB 积累的 Fe-Mn 氧化物结合 Cd 是对照的 1.54 倍，有效降低了 Cd2 + 迁移率。此外，松散结合的细胞外聚合物物质在酸化后声称优先螯合 Cd2 + 。稳定的微生态和增加的生态位，使 RBB 能够更好地缓冲 pH 值波动，使其成为在可变环境中可持续重金属修复的强大解决方案。