Dynamics of chemical pollution fluxes throughout the Rhône River catchment and at its outlet (France)
Abstract
Land-based human activities are known to be the largest sources of marine pollution. Once released into the hydrographic networks, metals and hydrophobic organic micropollutants reach coastal ecosystems mainly through suspended particulate matter (SPM). As a result, the accurate assessment of micropollutant fluxes discharged by rivers is critical to appraise the related environmental and health risks. Unfortunately, our current knowledge on pollutant fluxes in large river systems is limited, especially on their inter-seasonal dynamics. This is typically the case for the Rhône River, the largest source of freshwater and SPM of the Western Mediterranean Sea. Thanks to the comprehensive monitoring network implemented within the Rhône catchment, covering about 80 % of its area, daily time-series of micropollutant fluxes over the 2008-2018 period have been computed. Firstly, through the concentration levels of 29 organic and inorganic micropollutants, the stations can be ranked and the sub-catchments chemical fingerprints can be used to identify the main anthropogenic and geographical pollution sources. Secondly, the present work explores the range, seasonality, and inter-annual averages of pollutant fluxes at the Rhône River outlet and from its main tributaries. Thus, the mean inter-annual fluxes of particulate pollutants discharged to the Mediterranean are about 61 kg yr-1 for Ʃ5PCB, 3 t yr-1 for Ʃ13PAH, 1802 t yr-1 for Ʃ9TM (trace metal elements), 97 kg yr-1 for glyphosate, and 220 kg yr-1 for AMPA. Moreover, we observe a strong seasonal variability. Indeed, the inter-annual monthly pollutant fluxes display a three-mode profile with peaks centered in November, January, and May-June, respectively. During those months, two thirds of the total micropollutant annual fluxes are released at the Rhône River outlet. These micropollutant discharge periods closely follow the modes of the complex hydrological regime of the Rhône River combining Mediterranean, oceanic pluvial, and nival floods. The deconvolution of the three-mode profile of micropollutant fluxes shows that the Durance, Saône, and Isère rivers contribute at about 19% of the Mediterranean component, 18% of the oceanic pluvial component, and 59% of the nival component, respectively.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H31B..06D
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0432 Contaminant and organic biogeochemistry;
- BIOGEOSCIENCES;
- 1834 Human impacts;
- HYDROLOGY;
- 1880 Water management;
- HYDROLOGY