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

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