Spatio-temporal assessment of the PCB sediment contamination in the four main French River Basins (1945–2018)

Abstract. Environmental pollution by Polychlorinated Biphenyls (PCBs) is a key concern about river quality because of their low degradation rates leading to their accumulation in sediments or living organisms. This original interdisciplinary work was conducted at a large scale along the four main French rivers (Seine, Rhône, Loire and Garonne Rivers), which flow into major European seas. We completed a dataset based on sediment analyses provided by monitoring agencies, port authorities and research teams on different solid matrices (cores, bed and flood sediments, suspended particulate matters, dredged sediments). This dataset (n=1416) focused on the seven indicator PCBs and their sum (∑PCBi) from 1945 to 2018. Special effort was put on the quality control to provide robust spatio-temporal information. Taking into account hydrological and human drivers, we outlined two main pollution trends: (1) from 1945 to 1975, a quick increase of ∑PCBi (up to 4 mg.kg−1 dry weight, dw) and a sharp decrease in the 1980s on the Seine and Loire Rivers; (2) increasing but moderate ∑PCBi levels (50 to 150 µg.kg−1 dw) followed by a decline after the 1990s on the Rhône and Garonne Rivers. In addition to these patterns, PCBs emissions from urban and industrial areas or accidental events were significant on each river. Finally, when calculating specific fluxes, the Rhône River exhibited the biggest ∑PCBi load (up to 12 µg.m−2.year−1 in 1977–1987), at least 25 % higher than those of the Seine and Loire Rivers, while the Garonne River showed very low fluxes. French specific ∑PCBi fluxes are two orders of magnitude lower than those found in American or Asian Rivers. In Europe, we confirmed that the Rhone and Seine Rivers provide a major supply of PCBi to the Western Mediterranean and the English Channel, respectively. The dataset is available at https://doi.pangaea.de/10.1594/PANGAEA.904277.