A multi-proxy sediment record of atmospheric contaminant deposition in the Paris Basin since the nineteenth century

Small ponds represent valuable but still underexploited archives for reconstructing long-term environmental contamination, particularly those disconnected to fluvial networks. In this study, a sediment core from the Saint-Denis pond (Paris Basin, France) was used to reconstruct the historical evolution of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and per- and polyfluoroalkyl substances (PFAS) over the last 150 years. The ¹³⁷Cs record, characterized to the well-defined atmospheric fallout peak in 1963, was retained as the most robust age model, particularly for the second half of twentieth century, when investigated contaminant dynamics were strongly influenced by human activities. The resulting chronology indicates continuous sediment accumulation from the late nineteenth century to 2021.Temporal trends in PAHs, PCBs, and PFAS closely match known historical production, use, and regulatory phases, providing independent validation of the ¹³⁷Cs-based age model. Although indirect contaminant transfers via surrounding forest soils cannot be entirely excluded, the sediment record predominantly reflects atmospheric-driven contamination. This multi-proxy approach demonstrates the relevance of pond sediments for environmental monitoring and retrospective assessment of long-term contamination trends at the regional scale.