Phosphorus mobilization in sulfidic sediments in the Baltic Sea

• Published in: The Science of the total environment 2024-01, Vol.907, p.168000-168000, Article 168000
• Main Authors: Zhou, Chunyang, Gao, Yue, Zhang, Hao, Luo, Mingyue, Ma, Tianhui, Li, Guanlei, Vandeputte, Delphine, Leermakers, Martine, Baeyens, Willy
• Format: Article
• Language: English
• Subjects: Authigenic P minerals; DGT technique; P-bearing solids; Phosphorus mobilization; Resupply kinetics; Sulfidic sediments
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.168000

It is well-known that the geochemical behavior of phosphorus (P) in sediments is closely related to that of Fe and Mn, but their relations remain unclear in long-term sulfidic sediments such as those of the Gotland Basin in the Baltic Sea. Therefore, P mobilization in these sediments at both shallow and deep sites was investigated in relation to that of Fe, Mn, and S. To achieve that aim, classic sediment slicing and subsequent solid phase sequential extraction were combined with in situ DGT (Diffusive Gradients in Thin-films) sampling, DIFS (DGT induced flux in sediments) modelling, and Visual MINTEQ calculations. Correlations between total dissolved and labile dissolved concentrations of P, Mn, and Fe in porewater, and the associations between labile fractions of these elements in the solid phase suggested two kinds of sources for P: The dissolution of P-bearing Fe oxides and/or Mn carbonates was observed in the shallower sites, while P and Mn release from different solid sources was observed in the deepest sites. Although the formation of Fe sulfides leads to extremely low dissolved Fe level in porewater, the simultaneous release of P with Mn/Fe was confirmed by theoretical calculations with Visual MINTEQ. The DIFS model showed that the resupply ability of P from sediment solids is determined by labile pool size. The application of experimental and theoretical methods made it possible to clarify the relationships between P, Fe, Mn and S in sulfidic sediments which may contribute to a better understanding of the P cycle in other sulfidic regions. [Display omitted] •P mobilization in Baltic Sea sediments was investigated by integrating multi-approaches.•Dissolution of P-bearing Mn carbonates dominates the co-release of dissolved P and Mn.•P resupply from sulfidic sediment solids is determined by its labile pool size.•Fe plays a hidden role in P mobilization pathways in sulfidic sediments.