Radium and Lead Radioisotopes Composition of Sediment and Its Biogeochemical Implication in Polymetallic Nodule Area of Clario-Clipperton Zone

Radioactivity levels of (210)Pb and (226)Ra were detected in a sediment core obtained using a multi-corer from the polymetallic nodule area inside the Clarion-Clipperton Zone (CCZ), a contract area of the China Ocean Mineral Resources Association (COMR) in the eastern Pacific Ocean. The profile of excess (210)Pb ((210)Pb(ex)) shows that the specific activity of (210)Pb(ex) has three parts with different distributions at depths of 0–16 cm (I), 17–36 cm (II), and 37–48 cm (III). When the I section of nonlocal mixing was excluded, using a steady-state diffusion mode, the bioturbation coefficients of the core were estimated to be 24.2 cm(2)/a at 17–36 cm deep and 5.9 cm(2)/a at 37–48 cm deep, which were greater compared to previously published results. This is most likely owing to bioturbations caused by various organism species in the two sections.