Short-term dynamics of soluble reactive phosphorus (SRP) transport across the sediment surface in a brackish lake due to discontinuous aeration and oxygenation operations were investigated by experimental and analytical methods. SRP release from the sediment was obviously suppressed by aeration and substantial negative SRP transfer was observed in oxygenation treatment, while a positive value was observed for N2 bubbled cores. The negative SRP transfer was considered to be diffusive transport, caused by the SRP concentration decrease in the pore water of the sediment surface due to oxygenation. A remarkable and temporal increase in the SRP release rate was observed within one or two days after discontinuing the aeration and oxygenation, respectively, and the release rate rapidly deceased to a quasi-steady value under N2 bubbling conditions. This temporal increase was due to the rapid release of desorbed SRP from the sediment surface, and these time-scales of unsteady dynamics in SRP transfer were well explained by the desorption and diffusion processes of SRP in the sediment surface. The results claimed the importance of SRP desorption from ferric hydroxide.
　An analytical model, which is modified to express the adsorbed-SRP dynamics, could quantitatively reproduce these experimental results for anoxic and aerated conditions, but failed for oxygenation. This failure might be because that the numerical model did not formulate oxidation-reduction potential and the SRP desorption started immediately after the O2 depletion in the model calculation.
　To summarize, continuous hypolimnetic aeration and oxygenation are definitely effective approaches to suppressing SRP release from the sediment, but the effects will not be maintained without aeration/oxygenation operations. Moreover, such temporal and spatial discontinuity of oxygenation may make it difficult to understand the effects of the operations.