Uranium series radionuclides

Abstract

The activities of 228Th, 230Th, 234Th, 226Ra, 228Ra, 210Po, and 210Pb have been reported in the East Sea (Japan Sea) over the past few decades. The activities of thorium isotopes over the entire depth of the East Sea ranged from 0.4 to 8.3 dpm 100 L-1 for 228Th, 0.06 to 0.37 dpm 1000 L-1 for 230Th, and 0.4 to 2.1 dpm L-1 for 234Th. Thorium isotopes in the East Sea were used for determining the collection efficiency of sediment traps (using 230Th) and the annual vertical flux of particulate organic carbon (using 234Th). The activities of radium isotopes over the entire depth of the East Sea ranged from 0.3 to 11 dpm 100 L-1 for 228Ra and 6.4 to 16 dpm 100 L-1 for 226Ra. Radium isotopes in the East Sea were used for determining the vertical eddy diffusion coefficient (using 228Ra) and the residence time of deep water (using 226Ra). The activities of 210Pb over the entire depth ranged from 4.4 to 27 dpm 100 L-1, and the activities for 210Po over the entire depth ranged from 1.5 to 11 dpm 100 L-1. The 210Pb and 210Po in the East Sea were used for estimating the residence time of trace elements in the dissolved, colloid, and particulate phases. In summary, U-series radioisotopes have provided useful information on various physical and biogeochemical processes in the East Sea.