Novel Multi-Isotope Am and Cm Signatures Trace Temporal Changes in Nuclear Inputs in a Baltic Sediment Core

Abstract Anthropogenic radionuclides have been present in the environment since 1945 due to civil and military uses of nuclear energy. This study represents an extensive characterization of Am and Cm isotopes (241Am, 242mAm, 243Am, 244Cm, 245Cm, 246Cm), and 237Np, in a Baltic Sea sediment core directly impacted by discharges from the Studsvik nuclear research facility (Sweden). Distinct isotopic signatures were identified throughout the sediment core, enabling discrimination between inputs from atmospheric nuclear weapons testing (1952–1965), Sweden’s nuclear-weapons-related activities during the 1970s, and subsequent releases associated with civil nuclear-energy development. The findings demonstrate that higher actinides provide powerful isotopic fingerprints for resolving complex nuclear contamination histories and attributing release sources in environmental archives. This study further establishes the utility of actinide isotopic tracers beyond U and Pu and presents the first environmental application of the 243Am/241Am ratio in a system with well-constrained inputs from distinct nuclear sources.