April 2008

Four radium isotopes, decay products of the ²³⁸U–²³²Th–²³⁵U series radionuclides, occur in nature: ²²⁴Ra (t_1/2=3.66 days), ²²³Ra (t_1/2=11.4 days), ²²⁸Ra (t_1/2=5.75 years), and ²²⁶Ra (t_1/2=1600 years). Beginning with the GEOSECS program of the late 1960s – early 1970s, these radium isotopes have been widely applied to the study of a variety of oceanographic processes (Moore, 1972; Trier et al., 1972).