Mass Balance of PAHs at the Scale of the Seine River Basin

Abstract

The Seine River basin (France) is representative of the large urbanised catchments (78,650 km2) located in Northwestern Europe. As such, it is highly impacted by anthropogenic activities and their associated emissions of pollutants such as polycyclic aromatic hydrocarbons (PAHs). These compounds, originating from household heating and road traffic, are responsible for serious environmental issues across the basin. This study aims at establishing and using mass balance analyses of PAHs at the Seine River basin scale as an efficient tool for understanding PAH pathways in the environment. A dual-scale approach (urban vs. rural areas) was used successfully, and mass balances provided useful knowledge on the environmental fate of PAHs. In urban areas, runoff and domestic and industrial discharges contributed similarly to the PAH supply to the sewer system. During the wastewater treatment process, PAHs were mainly eliminated through sludge removal. At the basin scale, substantial amounts of PAHs were quantified in soils, and the limited annual inputs and outputs through atmospheric deposition and soil erosion, respectively, suggest that these compounds have long residence times within the basin. While wastewater and runoff discharges from urban areas account for a substantial part of PAH urban fluxes to the Seine River, soil erosion seems to be the predominant contributor at the basin scale. Overall, the PAH flux at the basin outlet was greater than supplies, suggesting that the Seine River system may currently be undergoing a decontamination phase.

Rivers help us to quantify the socio-ecological functioning of their basin at the Anthropocene: the Seine example (1850–2020)

“…Other metabolism studies have been established for heavy metals [Meybeck et al, 2007, for PAHs, drug residues and emerging pollutants [Gateuille et al, 2021, Labadie et al, 2021, Tamtam et al, 2008, for specific micropollutants as PCBs, PAHs, phthalates, PBDE, pesticides, microplastics, in rural, and peri-urban areas [Blanchoud et al, 2013, Dris et al, 2015, Gateuille et al, 2014, Teil et al, 2014. These studies show the extent to which the material is imported, transported, transformed, recycled, and exported within the anthroposphere.…”

Legacy‐micropollutant contamination levels in major river basins based on findings from the Rhône Sediment Observatory

“…; Noyes et al, 2009;Eschbach et al, 2018;Cornwall, 2020) and/or chemical processes (increasing solubility of some micropollutants; Stigliani, 1991;Schwarzenbach et al, 2010) are likely to confound the relationship between economic development phases and freshwater quality due to lag times (decadal to millennial time scales). Legacy contaminated sediments along the river continuum pertain to the issue of (i) contaminant residence times along river corridors (Pizzuto, 2014;Sutfin & Wohl, 2019;Wohl, 2015Wohl, , 2019, (ii) total time for contaminant transfer to river outlets and (iii) the theoretical decontamination time of a river basin (Gateuille et al, 2014(Gateuille et al, , 2020Singer et al, 2013).…”

Trajectories of the Seine River Basin

“…The reconstruction of these fluxes and of their evolution over time makes it necessary to correlate the knowledge on the circulation of substances in the anthroposphere (manufacturing, importation, consumption, and evolution of uses) with field data provided by official water surveys or collected by the teams involved in the PIREN-Seine programme. Mass balances at the scale of the Seine River basin were undertaken for nitrogen [58], non-ferrous metals [59], and polycyclic aromatic hydrocarbons (PAHs) [60].…”

“…In addition to laboratory analyses (e.g. characterization of organic matter [83], analysis of contaminants [60,84], ecotoxicology [85], microbiology [40]), the field activities range from agricultural plot studies to interannual river exports assessed at the basin outlet. Various intermediate time and spatial scales are considered, depending on the scientific or societal question being addressed.…”