Magnetic microparticles as a new tool for lake restoration: A microcosm experiment for evaluating the impact on phosphorus fluxes and sedimentary phosphorus pools

• Magnetic particles caused a reduction in P release rate under anoxic conditions.
• No effect of magnetic particles was observed in P fluxes under oxic conditions.
• Magnetic particles reduced sedimentary mobile P concentration in oxic and anoxic conditions.
• Organic P forms were preferably adsorbed on MPs.

In the last decades, magnetic particles (MPs) as adsorbents have gained special attention due to their high adsorption capacity and the possibility of recovering them by applying a magnetic separation gradient. For the first time MPs have been tested as P adsorbents in a microcosm experiment in a context of lake restoration. MPs were added to sediment cores from a hypertrophic lake, at Fe:PMobile molar ratio of 285:1 and 560:1 under both, oxic and anoxic conditions. We have found that, under anoxic conditions (anoxic), MPs are able to reduce P release rate from the sediment to the overlying water and to reduce sedimentary PMobile concentration (a 22–25% reduction within 0–4 cm depth compared to controls). Under oxic conditions, the addition of MPs do not affect P fluxes across the sediment and water interface since the lake sediment is naturally rich in iron oxides. However a measured reduction in sedimentary PMobile concentration (12–16% reduction in 0–10 cm depth) contributes to a potential reduction in long-term P efflux.

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