Distribution, speciation and composition of humic substances in a macro-tidal temperate estuary

Type Article
Date 2021-07
Language English
Author(s) Riso Ricardo1, Mastin ManonORCID2, Aschehoug Arthur1, Davy Romain2, Devesa Jeremy1, Laes Huon AgatheORCID2, Waeles Mathieu1, Dulaquais Gabriel2
Affiliation(s) 1 : Laboratoire des Sciences de l'environnement Marin, Institut Universitaire Européen de la Mer, CNRS/IRD/UBO/IFREMER (UMR 6539), Place Nicolas Copernic, F-29280, Plouzané, France
2 : Laboratoire Détection Capteurs et Mesures, Unité de Recherches et Développements Technologiques, Ifremer, France
Source Estuarine Coastal And Shelf Science (0272-7714) (Elsevier BV), 2021-07 , Vol. 255 , P. 107360 (10p.)
DOI 10.1016/j.ecss.2021.107360
Keyword(s) Humic substances, Estuary, Suspended particulate matter, Biogeochemistry

In aquatic environments, the term humic substances (HS) encompasses terrestrial and autochthonous refractory organic matter. HS are one of the main fractions of natural organic matter and are important chelators of trace elements. In environmental studies, the determination of HS is often restricted to the dissolved fraction, and the content of HS in the suspended particles remains unknown. In this work, we present the composition and dynamics of HS along the mixing gradient of a macrotidal estuary in both the dissolved and particulate fraction. After the isolation of particulate HS using a solid-liquid alkali extraction method, HS were characterized by size exclusion chromatography (SEC) and electrochemical methods. The method, validated using a certified reference material, demonstrated a low detection limit (μg-C L−1), a good repeatability (7.7%) an excellent reproducibility (1.3%) and was poorly prone to contamination (filter blank < 1 μg-C). Analyses of environmental samples showed a particulate fraction contributing significantly to the total humic pool in the estuary (3–20%) and representing up to 35% of electroactive HS. Phase transfers from the dissolved to the particulate fraction were observed and the electroactive HS were strongly affected in the maximum turbidity zone. Multi-detection SEC analyses showed differences in the molecular composition between the dissolved and particulate fractions. Particulate HS were more nitrogen-rich and electroactive than dissolved HS. The non-conservative changes in the composition of HS along the land-sea continuum evidence the existence of abiotic and biotic processes that altered HS during their transit from river to marine waters.

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Riso Ricardo, Mastin Manon, Aschehoug Arthur, Davy Romain, Devesa Jeremy, Laes Huon Agathe, Waeles Mathieu, Dulaquais Gabriel (2021). Distribution, speciation and composition of humic substances in a macro-tidal temperate estuary. Estuarine Coastal And Shelf Science, 255, 107360 (10p.). Publisher's official version : https://doi.org/10.1016/j.ecss.2021.107360 , Open Access version : https://archimer.ifremer.fr/doc/00688/80019/