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In situ oxygen microprofiles, sediment organic carbon content, and pore-water concentrations of nitrate, ammonium, iron, manganese, and sulfides obtained in sediments from the Rhˆone River prodelta and its adjacent continental shelf were used to constrain a numerical diagenetic model. Results showed that (1) the organic matter from the Rhˆone River is composed of a fraction of fresh material associated to high first-order degradation rate constants (11– 33 yr−1); (2) the burial efficiency (burial/input ratio) in the Rhˆone prodelta (within 3 km of the river outlet) can be up to 80 %, and decreases to 20% on the adjacent continental shelf 10–15 km further offshore; (3) there is a large contribution of anoxic processes to total mineralization in sediments near the river mouth, certainly due to large inputs of fresh organic material combined with high sedimentation rates; (4) diagenetic by-products originally produced during anoxic organic matter mineralization are almost entirely precipitated (>97 %) and buried in the sediment, which leads to (5) a low contribution of the re-oxidation of reduced products to total oxygen consumption. Consequently, total carbon mineralization rates as based on oxygen consumption rates and using Redfield stoichiometry can be largely underestimated in such River-dominated Ocean Margins (RiOMar) environments.
Original languageEnglish
Journal publication date2011

ID: 110057