Short-term variation in benthic phosphorus transfer due to discontinuous aeration/oxygenation operation

The 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 using laboratory and field experimental and analytical procedures. According to a laboratory incubation experiment using intact sediment cores, SRP release from the sediment was clearly suppressed by aeration, and substantial negative SRP transfer was observed during oxygenation treatment, while a positive value was observed for N₂ bubbled cores. A remarkable but impermanent increase in SRP release rate was observed within 1 or 2 days of discontinuing the aeration and oxygenation, respectively, and the release rate rapidly deceased to a quasi-steady value under N₂ bubbling conditions. An analytical model could quantitatively reproduce these laboratory experimental results for anoxic and aerated conditions, showing that this impermanent increase was attributable to the rapid release of accumulated SRP in the oxic surface layer of the sediment. Field experiments using an in situ oxygenator showed the same tendency as the laboratory experiments, but with much larger values of the benthic SRP transfer rate. Overall, the short-term dynamics of benthic SRP transport caused by discontinuous aeration and oxygenation are considered to be an important process for the phosphorus cycle in the field.