Accumulation of geogenic phosphorus (P) in groundwater is an emerging environmental concern, which is closely linked to coupled processes involving FeOOH and organic matter under methanogenic conditions. However, it remains unclear how P enrichment is associated with methane cycling, particularly the anaerobic methane oxidation (AMO). This study conducted a comprehensive investigation of carbon isotopes in dissolved inorganic carbon (DIC), CO₂, and CH₄, alongside Fe isotopes, microbial communities, and functions in quaternary aquifers of the central Yangtze River plain. The study found that P concentrations tended to increase with Fe(II) concentrations, δ⁵⁶Fe, and δ¹³C-DIC, suggesting P accumulation due to the reductive dissolution of FeOOH under methanogenic conditions. The positive correlations of pmoA gene abundance versus δ¹³C–CH₄ and Fe concentrations versus δ¹³C–CH₄, and the prevalent presence of Candidatus_Methanoperedens, jointly demonstrated the potential significance of Fe(III)-mediated AMO process (Fe-AMO) alongside traditional methanogenesis. The increase of P concentration with δ¹³C–CH₄ value, pmoA gene abundance, and Fe concentration suggested that the Fe-AMO process facilitated P enrichment in groundwater. Redundancy analysis confirmed this assertion, identifying P concentration as the primary determinant and the cooperative influence of Fe-AMO microorganisms such as Candidatus_Methanoperedens and Geobacter on P enrichment. Our work provided new insights into P dynamics in subsurface environments.

中文翻译：

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厌氧甲烷氧化耦合 Fe(III) 氧化物还原导致地下水中地源磷富集

地下水中地源磷 (P) 的积累是一个新兴的环境问题，它与产甲烷条件下 FeOOH 和有机物的耦合过程密切相关。然而，目前尚不清楚磷富集如何与甲烷循环，特别是厌氧甲烷氧化（AMO）相关。本研究对长江中部平原第四系含水层中溶解无机碳（DIC）、CO ₂和CH ₄中的碳同位素以及铁同位素、微生物群落和功能进行了全面调查。研究发现，P 浓度随着 Fe(II) 浓度、δ ⁵⁶ Fe 和 δ ¹³ C-DIC 的增加而增加，这表明 P 的积累是由于 FeOOH 在产甲烷条件下的还原溶解所致。pmoA基因丰度与 δ ¹³ C-CH ₄和 Fe 浓度与 δ ¹³ C-CH ₄呈正相关，以及Candidatus_Methanoperedens的普遍存在，共同证明了 Fe(III) 介导的 AMO 过程（Fe-AMO）的潜在意义。 ）与传统的产甲烷作用一起。 P浓度随着δ ¹³ C–CH ₄值、pmoA基因丰度和Fe浓度的增加而增加，表明Fe-AMO过程促进了地下水中P的富集。冗余分析证实了这一论点，确定磷浓度是主要决定因素，以及 Fe-AMO 微生物（如Candidatus_Methanoperedens和Geobacter）对磷富集的协同影响。我们的工作为地下环境中的 P 动力学提供了新的见解。