Abstract
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.
Highlights
Phosphorus is an essential element for all organisms, excessive accumulation of this element causes eutrophication (e.g., Wang et al 2008)
The short-term dynamics of soluble reactive phosphorus (SRP) transport across the sediment surface caused by discontinuous aeration/oxygenation were investigated by experimental and analytical methods
Laboratory incubation experiments were conducted under radical conditions, with pure oxygen used as a bubbling medium and the maximum O2 concentration reaching 900 lmol L-1
Summary
Phosphorus is an essential element for all organisms, excessive accumulation of this element causes eutrophication (e.g., Wang et al 2008). As a consequence of human activity, soluble reactive phosphorus (SRP) accumulates in sediment and is released into overlying water (Fillos and Swanson 1975), acting as an internal load in various lakes and reservoirs (Gomez et al 1999). Technical approaches to supplying oxygen can be grouped into three categories: artificial destratification, hypolimnetic aeration, and hypolimnetic oxygenation. Artificial destratification can achieve substantial reductions in oxygen depletion and heavy metal release from sediment. It is regarded as a practical approach and has been used in many lakes and reservoirs
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