Abstract
In order to investigate the chemical form of authigenic phosphate compounds being precipitated in coastal sediemnt, vertical distributions of dissolved phophate and fluoride in pore water from the sediments of Funka Bay Japan, were determined.
We found an inverse relationship between interstitial phosphate and fluoride concentrations, suggesting precipitation of an authigenic fluoro-phosphorus compound with a P/F atomic ratio of around 1/3 in the sediemnt. The solubility experiments of biogenic silica were done using the Funak Bay sediments. The solubility coefficients were estimated from temporal change of interstitial silicate in a temperature controlled room of 6, 11 and 22°C. The change of silicate concentrartion is irreversible for temperature, the irreversibility is larger at surface than in a deeper layer. This suggested that biogenic silicate in a deeper layer is more crystallized than at surface.
