Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing 210024, PR China.
Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing 210024, PR China.
Water Res. 2024 Nov 15;266:122433. doi: 10.1016/j.watres.2024.122433. Epub 2024 Sep 11.
Anthropogenic enrichment of phosphorus (P) in water environment can cause eutrophication, harmful algal blooms, and water quality deterioration. Adsorbents are often used for the removal and recovery of P from water, however, P is highly susceptible to re-release in anoxic benthic environments. As a response, this study prepared oxygen-carrying iron-rich biochar (O-Fe-BC) as an effective oxygen micro-nanobubble carrier (Q = 8.7024 cm³/g STP at 1.5 MPa) and P adsorbent (q = 16.7097 mg P/g, q = 3.1974 mg P/g). Over the 90-day experimental period with O-Fe-BC, dissolved oxygen (DO) levels in the overlying water could maintain at ∼4 mg/L (peaking at ∼9.5 mg/L), and total phosphorus (TP) and soluble reactive phosphorus (SRP) levels decreased by over 96 %. The higher inorganic phosphorus content in the surface sediment-biochar mixture, along with the lower labile P and Fe concentration in the sediment pore water in the O-Fe-BC group compared to other groups, suggested the enhanced P immobilization. Further mechanism exploration revealed the combined roles of adsorption and microbial response, in which O-Fe-BC achieved efficient phosphate adsorption primarily through inner-sphere complexation via ligand exchange and keystone taxa (particularly Candidatus Electronema) played a crucial role in driving water chemistry divergence. Specially, these cable bacteria could provide large pools of Fe oxides in the surface sediment, binding with P to prevent its release, as supported by significant correlations between Ca. Electronema abundance and oxidation-reduction potential (ORP), TP, SRP, and sediment Fe-P variations. Additionally, a pot experiment with mung bean seedlings showed that the recovered O-Fe-BC significantly promoted the seed germination and growth, indicating its potential as a novel material for removing and recovering P from eutrophic waters. Taken together, our work provided a promising strategy for sustainable anoxia and P pollution mitigation, and also highlighted the indispensable roles of inner-sphere adsorption in P recovery and microbial keystone taxa in P cycling regulation.
人为向水环境中添加磷（P）会导致富营养化、有害藻类大量繁殖和水质恶化。吸附剂常用于从水中去除和回收磷，但在缺氧底栖环境中，磷很容易重新释放。因此，本研究制备了载氧富铁生物炭（O-Fe-BC）作为有效的氧气微纳米气泡载体（1.5 MPa 下 STP 时 Q 值为 8.7024 cm³/g）和磷吸附剂（q 值为 16.7097 mg P/g，q 值为 3.1974 mg P/g）。在 90 天的 O-Fe-BC 实验期间，上覆水中的溶解氧（DO）水平可以维持在约 4 mg/L（最高约 9.5 mg/L），总磷（TP）和可溶解性活性磷（SRP）水平下降超过 96%。与其他组相比，表面沉积物-生物炭混合物中无机磷含量较高，沉积物孔隙水中可利用磷和铁浓度较低，表明磷固定增强。进一步的机制探索表明了吸附和微生物响应的共同作用，其中 O-Fe-BC 通过配体交换和关键种（特别是 Ca. Electronema）的内圈络合实现了磷酸盐的有效吸附，这些关键种在驱动水化学分异方面发挥了关键作用。特别是，这些电缆细菌可以在表面沉积物中提供大量的铁氧化物，与磷结合以防止其释放，这与 Ca. Electronema 丰度与氧化还原电位（ORP）、TP、SRP 和沉积物 Fe-P 变化之间的显著相关性一致。此外，用绿豆幼苗进行的盆栽实验表明，回收的 O-Fe-BC 显著促进了种子的萌发和生长，表明其作为从富营养水中去除和回收磷的新型材料的潜力。总之，我们的工作为可持续缺氧和磷污染缓解提供了一种有前景的策略，并强调了内圈吸附在磷回收和微生物关键种在磷循环调节中的不可或缺作用。
