Does external phosphorus loading diminish the effect of sediment dredging on internal phosphorus loading? An in-situ...

Sediment dredging is an effective method to reduce internal phosphorus (P) loading of eutrophic lakes. However, external P loading may diminish the longevity of the effect of sediment dredging on P internal loading, and the mechanism of the same is unclear. Here, we used one-year in-situ simulation experiments to study the migration and transformation processes of P under the effect of external loading (suspended particle matter, SPM) input and internal loading control by dredging. The results showed that dredging can effectively reduce the internal loading and mobility of P, increase the P adsorption and retention capacity of the sediment, and improve the oxidation environment at the sediment-water interface (SWI), thus, inhibiting the release of internal P. The input of SPM, however, can significantly inhibit the above processes and increase the risk of P resupply and release. Temperature, dissolved oxygen, and the P resupply capacity (R) are the key factors affecting the P flux across the SWI. Therefore, it is necessary to control the input of SPM to effectively inhibit eutrophication after dredging. More measures to control the input of SPM, such as establishing buffer zones, ecological wetlands, and forebays, should be explored and applied.