Origin and distribution of inositol hexaphosphate in estuarine and coastal sediments

In order to clarify the origin and the fate of inositol hexaphosphate (IP6) in coastal sediments from Tokyo Bay, we determined IP6 in several potential source materials, such as plankton, soil, riverine, and estuarine samples. IP6 was not found in zoo- and phytoplankton samples, thus eliminating these as a source to the sediments. Soils collected from the catchment areas of major rivers flowing into the bay contained high concentrations of IP6 (0.25-5.65 mu mol P g(-1)). Samples of suspended solids and estuarine sediments from the rivers also had significant amounts of IP6. The distribution pattern of IP6 in Tokyo Bay sediments exhibited relatively high concentrations in the estuarine areas, decreasing gradually toward the mouth of the bay. The IP6 in coastal sediments was composed of three isomers in the same order of abundance as those found in the terrestrial and riverine samples: myo- >> scyllo- > chiro-. From these results, IP6 in Tokyo Bay sediments was ascribed to soils transported by rivers from land into the bay. The IP6 concentration ranged from 0.01 to 0.10 mu mol P g(-1) in surface sediments (0-2.5 cm), accounting for < 1.2% of the total organic P; it was completely decomposed in the subsurface. Consequently, this compound is quite ephemeral in coastal marine environments.