Interactions between iron and sulfur on the release and dynamics of phosphorus in eutrophic lake sediments

• Published in: Journal of soils and sediments Vol. 25; no. 1; pp. 313 - 327
• Main Authors: Zhu, Dongdong, Hang, Xiaoshuai, Xu, Minqiang, You, Xiaohui, Wang, Xia, Zhou, Li, Wang, Yan
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.01.2025; Springer Nature B.V
• Subjects: Anaerobic conditions; Anaerobic processes; Anoxia; Anoxic conditions; Anoxic sediments; Bacteria; computers; Coupling; Densitometry; Earth and Environmental Science; Environment; Environmental Physics; Eutrophic environments; Eutrophic lakes; Eutrophication; Iron; Iron sulfides; Kinetics; Lake deposits; Lake sediments; lakes; Organic matter; Organic phosphorus; Phosphorus; Plates; Pore water; Sec 2 • Physical and Biogeochemical Processes • Research Article; Sediment; sediment-water interface; Sediments; Soil Science & Conservation; spatial distribution; Spectrophotometers; Sulfate reduction; Sulfate-reducing bacteria; sulfides; Sulfur; Sulphate reduction; Sulphides; Sulphur; Thin films; Vertical distribution; Water analysis; Water sampling; Sulfide; Diffusive gradient in thin films; Phosphorus; Iron; Sediment–water interface; Eutrophication
• ISSN: 1439-0108; 1614-7480
• DOI: 10.1007/s11368-024-03909-4

Purpose This study aimed to provide in situ evidence for the simultaneous coupling of iron (Fe), sulfide (S(-II)) and phosphorus (P) in the sediment‒water interface (SWI) under anaerobic conditions, thereby enhancing the understanding of the process and mechanism of phosphorus dynamics in eutrophic lake sediments. Materials and methods A 300-day redox-cycle process of aerobic-anoxic-anaerobic was conducted in six periods. High-resolution methods, including diffusive gradient in thin films (DGT) and pore water sampling technology (HR-Peeper) were used to measure Fe, S(-II) and P in the vertical sediment. A 96-well microplate spectrophotometer was employed to detect the dissolved and labile concentrations of Fe(II) and P. The determination of S(-II) was performed using the computer imaging densitometry (CID) scanning method. The ratio of the labile to the soluble concentration ( R diff , C DGT /C SOL ) was calculated to characterize the kinetics of Fe and P release from sediments into the overlying water. Results and discussion The vertical distribution of labile and soluble P, Fe(II) and S(-II) in water and sediment was measured. Findings reveal concentration peaks of these elements at 10–40 mm depth in the SWI, with a significant positive correlation between them. The Fe–P coupling is the main driver of phosphorus release, with S(-II) participating in this process. Organic matter is utilized as an electron donor by sulfate-reducing bacteria, which reduces Fe(III) to Fe(II) and forms FeS precipitation, further promoting the release of Fe–P. The ratio of labile to dissolved concentration (C DGT /C SOL ) peaks (20–40 mm in the SWI) during the transition from aerobic to anaerobic conditions, indicating a strong replenishment ability of sediment to pore water at this stage. Conclusions Under anaerobic conditions, there is a synchronous vertical distribution of P, Fe(II), and S(-II), with the reduction of Fe oxides being the main cause of P release from sediments. Under highly anaerobic conditions, S(-II) indirectly affects the dynamic of P by combining with Fe(II), potentially becoming the dominant factor. Changes in R diff -P and R diff -Fe infer that in the SWI of Lake Taihu sediments, Fe and P have a high capacity to replenish from the sediment particles to the pore water.