Record of trace organic contaminants in a river sediment core: A fingerprint of regulatory changes?

This study reconstructs the historical deposition of 76 trace organic contaminants (TrOCs), comprising pharmaceuticals, pesticides, and per- and polyfluoroalkyl substances (PFAS), in a dated sediment core taken from a secondary channel of the Seine River downstream of the Paris conurbation. Sediment chronology, established through 210 Pb and 137 Cs radionuclide depth activities, spans the period from 1943 to 2022, providing a long-term record of anthropogenic influence on fluvial contamination. The vertical profiles of pharmaceutical residues reveal temporal patterns closely aligned with their respective dates of market introduction, followed by increasing concentrations and subsequent declines. Maximum TrOC sedimentary concentrations were observed during the 1980s, coinciding with incomplete wastewater collection coverage. A sharp decrease in concentrations post-2000 reflects significant improvements in wastewater collection and treatment infrastructure. For pesticides, sedimentary trends also correlate with usage history and regulatory actions, with detectable declines frequently preceding official bans, suggesting the influence of progressive restrictions or shifts in agricultural practices. In contrast, PFAS profiles display more complex dynamics: legacy compounds such as perfluorooctanesulfonic acid and its precursors peaked in the early 2000s, after which their decline was offset by the increasing presence of alternative substances (e.g., fluorotelomersulfonic acids, betaines), indicative of industrial substitution. Overall, sediment composition had a secondary influence on TrOC profiles, with external factors such as regulatory decisions and technological developments in wastewater treatment playing predominant roles. These findings underscore the utility of collecting and analyzing sedimentary archives for assessing the long-term effectiveness of environmental policies and for identifying persistent and emerging contaminants in riverine systems. • A 80-year record of contaminant occurrences from three classes in river sediments. • Good agreement between deepest contaminant detection and market launch. • Regulatory action outputs recorded in sediment support chemical quality gains. • Temporal patterns linked to use, bans and wastewater management.