Abstract
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 language | English |
|---|---|
| Pages (from-to) | 1351-1366 |
| Journal | Biogeosciences |
| Volume | 8 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - 2011 |