Abstract
In order to explain the mechanism of phosphate release from lake sediments under aerobic conditions, the behavior of Fe (II) and phosphate added to yeast extract solutions under bacterial growth was examined, which is to imitate the situation where Fe (II) -phosphate is released from anaerobic sediments to aerobic overlying waters.
When Fe (II) in Fe3 (PO4) 2 was added to yeast extract solutions under bacterial growth, it was oxidized to Fe (III). Althouth a part of Fe (III) precipitated as Fe (OH) 3, the rest remained in stably soluble form by complexing with dissolved organic ligands contained in yeast extract solutions. On the other hand the most part of Fe (II) in Fe3 (PO4) 2 added to distilled water precipitated immediately as Fe (OH) 3.
Phosphate added with Fe (II) to yeast extract solutions was adsorbed to precipitated Fe (OH) 3 in the ratio of 0.41 0.46 mol phosphate to 1 mol Fe (OH) 3. Phosphate released with Fe (II) from anaerobic sediments to aerobic overlying waters was supposed to remain soluble except the portion of adsorbing to Fe (OH) 3 in the above ratio.
