70-Year Anthropogenic Uranium Imprints of Nuclear Activities in Baltic Sea Sediments

A strongly stratified water structure and a densely populated catchment make the Baltic Sea one of most polluted seas. Understanding its circulation pattern time scale is essential to predict dynamics hypoxia, eutrophication, pollutants. Anthropogenic 236U 233U have been demonstrated as excellent transient tracers in oceanic studies, but unclear input history inadequate long-term monitoring records limit their application Sea. From two dated sediment cores, we obtained high-resolution anthropogenic uranium imprints originating from three major human nuclear activities throughout Atomic Era. Using novel 233U/236U signature, distinguished quantified inputs global fallout (45.4–52.1%), Chernobyl accident (0.3–1.8%), discharges civil industries (46.1–54.3%) We estimated total release (7–15 kg) atmospheric weapon testing pinpointed peak signal mid-to-late 1950s potential marker for onset Anthropocene Epoch. This work also provides fundamental data on early facilities, prompting worldwide 233U–236U tracer studies. anticipate our be used broader model-observation interdisciplinary research pollutant