The CHRONUS project was conceived to address critical knowledge gaps regarding the distribution and origin of anthropogenic actinides in the Baltic Sea, one of the most radioactively contaminated marine environments worldwide. This contamination results from multiple sources at global, regional, and local levels, including atmospheric nuclear test fallout, the Chernobyl accident, and authorized discharges from nuclear installations, among others. Understanding the different inputs and distribution patterns of actinides represents a major challenge that can only be addressed by studying multiple radionuclides and including the most-minor isotopes, which can only be analysed using the ultra-sensitive Accelerator Mass Spectrometry (AMS) technique.
The project pursued three main objectives: i) the optimisation of sample preparation and measurement techniques, ii) the generation of a comprehensive dataset of actinides in the Baltic Sea, and iii) the interpretation of contamination patterns and assessment of the contamination sources. Sediment cores collected from stations covering the whole Baltic Sea have been studied to pursue those objectives. The development of the techniques and the analysis of the different radionuclides have been conducted by using the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA, Spain), an international centre for accelerator science and technology in which the host institution, the University of Seville (USE, Spain), participates. During the project, in response to emerging analytical opportunities, the original set of target radionuclides (233U, 236U, 237Np, 239Pu, 240Pu, 241Pu, 242Pu, 244Pu) was expanded to include americium and curium isotopes (241Am, 243Am, 244Cm, 245Cm and 246Cm).
The CHRONUS project provides novel analytical tools for environmental radioactivity studies, supports more accurate contamination source attribution, and lays the groundwork for extending these approaches to other marine environments and AMS facilities worldwide. By generating high-quality data and advancing analytical techniques, this project aims to contribute to better scientific understanding and more informed environmental monitoring and policymaking in the context of radioactive contamination.
