Fluoride and borate-boron were determined in interstitial waters of core sediments from the Northwest Pacific.
The values of the fluoride to chloride concentration ratio in the interstitial waters are nearly equal to or lower than that in normal sea water, and derease with depth in the sediment core. And the values of borate-boron to chloride concentration ratio in the interstitial waters are higher than that in normal sea water, and show the trend to decrease with depth in the sediment core. The depletion of fluoride and borate-boron in interstitial waters in deep parts of sediment is probably due to the interaction with solid phase of the sediment.