| Presented here is the first detailed geochemical data set on the U/Th series Th, Pa, Ac, and Pb isotopes and artificial fallout radionuclides (Sr-90, Cs-137, and Pu isotopes), and some trace elements (V, Zn, Cd, Cu, Mn, and Ni) in two water columns of the Japan and Bonin trenches down to the bottom depths of 7585 m and 9750 m, respectively. Hydrographic properties such as temperature, salinity, dissolved oxygen, and nutrient content within the trench valley remain constant at the same levels as those in the bottom water of the Northwest Pacific basin (typically similar to 6000 m in depth). The radionuclide activities and most trace metal concentrations are also not very different from those in the overlying water at depths of around 5000-6000 m. This means... |
