POSSIBLE COMPLEXATION OF URANIUM WITH DISSOLVED HUMIC SUBSTANCES IN PORE WATER OF MARINE-SEDIMENTS

The relation between dissolved uranium and humic substances in pore water of marine sediments was studied in three different marine environments (hemipelagic, pelagic, and Japan Trench sediments) off Hokkaido Island, Japan. Pore water samples were squeezed out from sediments collected by a box corer at these sites, and their UV-visible spectra, fluorescence emission spectra and uranium concentrations were measured. In hemipelagic sediments, a positive correlation between uranium content and fulvic acid content (fluorescence at 400 nm) in pore water was observed. In Japan Trench sediments, positive correlations between uranium content and absorbance at 280 and 320 nm of pore water are found. These results suggest that pore water uranium may be complexed with dissolved humic substances, especially fulvic acid in hemipelagic and Trench sites.