The importance of iron redox reactions and mineral transformations for the fate of phosphorus in the environment

磷（P）是所有生物体必需但限制性的微量营养素，可以显著影响全球生态地球化学循环，最终调节全球初级生产力。环境中的磷循环与铁的氧化还原循环密切相关，因为铁矿物在自然界中含量丰富，具有高的比表面积和强的磷吸附能力。据报道，Fe（III）氧化物结合的磷约占9%的湖泊水体和高达70.4%的湖泊沉积物和土壤中的磷螯合。铁（III）氧化物在缺氧条件下容易受到微生物或非生物还原溶解，导致P动员或形成Fe（II）-磷酸盐矿物蓝铁矿。在自然环境中，水溶液和固体Fe（II）物种在好氧和缺氧条件下都可以进行微生物和非生物氧化，从而导致新形成的Fe（III）氧化物矿物对P的保留。然而，铁氧化还原循环如何影响铁相的转化和随后的命运（动员与保留）的磷仍然缺乏深入的了解。该建议的主要目的是了解铁的氧化还原反应和矿物（transforms）的关键作用，在复杂的环境设置中的P循环。具体而言，我们将（1）在存在P的情况下，在微生物还原过程中追踪非生物和生物Fe（III）氧化物矿物的（反）形成，并确定其对P的归宿的影响;（2）确定在微生物与非生物氧化过程中蓝铁矿的（反）形成及其对P的归宿的影响;（3）确定在Fe（III）-和硫酸盐还原菌共存下Fe（III）磷酸盐矿物的（反）形成及其对P的归趋的影响;（4）确定铁矿物在循环氧化还原条件下的（转化）过程及其对自然环境氧化还原过程中磷的形态和归宿的影响。预期的结果将加深我们目前的知识在自然环境中耦合铁和磷循环，将有助于全面了解全球地球上的磷循环。

Phosphorus (P) is an essential but limiting micronutrient for all living organisms and can significantly affect global biogeochemical cycles, ultimately regulating global primary productivity. Environmental P cycle is known to strongly couple with Fe redox cycling, since Fe minerals are abundant in nature, have high surface areas, and have strong P adsorption capacity. Fe(III) oxide-bound P is reported to account for about 9% of P sequestration from water columns of lakes and up to 70.4% in lake sediments and soils. Fe(III) oxides are readily subject to microbial or abiotical reductive dissolution under anoxic conditions, leading to P mobilization or the formation of the Fe(II)-phosphate mineral vivianite. Aqueous and solid Fe(II) species can undergo microbial and abiotic oxidation under both oxic and anoxic conditions in natural environments, resulting in P retention by newly formed Fe(III) oxide minerals. However, an in-depth understanding of how Fe redox cycling affects the transformation of Fe phases and the subsequent fate (mobilization vs retention) of phosphorous is still lacking. The key aim of this proposal is to understand the critical roles of Fe redox reactions and mineral (trans)formations for P cycling in complex environmental settings. Specifically, we will (1) follow the (trans)formation of abiogenic and biogenic Fe(III) oxide minerals during microbial reduction in the presence of P and determine its effect on the fate of P; (2) determine the (trans)formation of vivianite during microbial vs abiotic oxidation and its effect on the fate of P; (3) determine the (trans)formation of Fe(III) phosphate minerals in the co-presence of Fe(III)- and sulphate-reducing bacteria and its effect on the fate of P; (4) determine the (trans)formation of Fe minerals under cyclic redox conditions and its effect on the speciation and fate of P in redox transitions of natural environments. The expected results will deepen our current knowledge on the coupled Fe and P cycles in natural environments and will help to comprehensively understand global P cycling on Earth.