Kubeneck L Joëlle, Rothwell Katherine A, Notini Luiza, ThomasArrigo Laurel K, Schulz Katrin, Fantappiè Giulia, Joshi Prachi, Huthwelker Thomas, Kretzschmar Ruben
Soil Chemistry Group, Institute of Biogeochemistry and Pollutant Dynamics, CHN, ETH Zürich, 8092 Zürich, Switzerland.
School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, U.K.
Environ Sci Technol. 2025 Jan 14;59(1):523-532. doi: 10.1021/acs.est.4c10710. Epub 2024 Dec 24.
Coastal sediments are a key contributor to oceanic phosphorus (P) removal, impacting P bioavailability and primary productivity. Vivianite, an Fe(II)-phosphate mineral, can be a major P sink in nonsulfidic, reducing coastal sediments. Despite its importance, vivianite formation processes in sediments remain poorly understood. Here, we applied a novel approach to detect and quantify in situ vivianite formation in three intertidal flats. We conducted 7-week long incubations of mesh-bags filled with sediments mixed with (1) Fe-ferrihydrite, (2) Fe-ferrihydrite with adsorbed phosphate, and (3) Fe-ferrihydrite with adsorbed phosphate and some vivianite (natural Fe isotope abundance), which could serve as crystal growth sites. Synthesizing the ferrihydrite from Fe (96.1%) enabled us to detect transformation products using Fe-Mössbauer spectroscopy. Vivianite formed only in treatments containing adsorbed phosphate and only at the two sites where vivianite formation was thermodynamically feasible based on porewater chemistry. These results demonstrate vivianite formation within weeks when locally favorable Fe:P ratios exist. Although vivianite comprised a minor fraction of Fe (up to 15%), it represented a significant P pool (up to 72%), emphasizing its role in coastal P burial. Additionally, our results may apply to other environmental systems like limnic sediments.
海岸沉积物是海洋磷（P）去除的关键贡献者，影响着磷的生物有效性和初级生产力。蓝铁矿是一种磷酸亚铁矿物，在非硫化、还原性海岸沉积物中可能是主要的磷汇。尽管其很重要，但沉积物中蓝铁矿的形成过程仍知之甚少。在此，我们采用一种新方法来检测和量化三个潮间带原位蓝铁矿的形成。我们对装有沉积物的网袋进行了为期7周的培养，沉积物与（1）铁水铁矿、（2）吸附了磷酸盐的铁水铁矿以及（3）吸附了磷酸盐且含有一些蓝铁矿（天然铁同位素丰度）的铁水铁矿混合，后者可作为晶体生长位点。用铁（96.1%）合成铁水铁矿使我们能够利用铁穆斯堡尔谱检测转化产物。仅在含有吸附磷酸盐的处理组中形成了蓝铁矿，且仅在基于孔隙水化学蓝铁矿形成在热力学上可行的两个地点形成了蓝铁矿。这些结果表明，当局部存在有利的铁磷比时蓝铁矿可在数周内形成。尽管蓝铁矿仅占铁的一小部分（高达15%）但它代表了一个显著的磷库（高达72%），强调了其在海岸磷埋藏中的作用此外我们的结果可能适用于其他环境系统如湖泊沉积物。
