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Updated: Aug 5, 2026

The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations
Published on: August 3, 2016
Sediment oxygen demand in a tidal river: spatial heterogeneity and associated factors
Mei Wang1, Jintao Yu2, Changbo Zhang3
1Shanghai Institute of Chemical Industry Environmental Engineering Co., Ltd., Shanghai, 200062, China; State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
None:
Sediment oxygen demand (SOD) is a key regulator of dissolved oxygen dynamics and a potential contributor to oxygen depletion processes in tidal rivers. However, its spatial heterogeneity and its controlling factors remain insufficiently understood. This study investigated the longitudinal distribution of SOD along an upstream-downstream gradient in a tidal river and quantified the relative contributions of operationally defined biological SOD (BSOD) and chemical SOD (CSOD) fractions. The upstream sandy sediments with relatively low organic matter (OM) content exhibited low SOD, with an average value of 0.19 g m-2 d-1, and BSOD contributed the dominant proportion of total SOD. In the midstream reach, SOD significantly increased (mean: 0.87 g m-2 d-1), with an enhanced contribution of the operationally defined CSOD fraction, forming a distinct zone of elevated oxygen consumption. This pattern was associated with accumulation of fine particles and OM, as well as elevated Mn concentrations and strongly reducing conditions in the midstream reach. In contrast, the downstream reach exhibited moderate SOD levels (mean: 0.28 g m-2 d-1), with BSOD again becoming the dominant oxygen-consumption fraction, which may be associated with tidal influence and sediment redox conditions. Correlation analysis revealed significant associations between SOD and sediment oxidation-reduction potential, grain-size composition, and OM content. Elevated Mn concentrations and Fe-Mn-associated SOD were observed in sediments with high SOD and strongly reducing conditions, suggesting that Fe/Mn-related redox processes may be associated with spatial variations in CSOD. Overall, the spatial heterogeneity of SOD was closely associated with sediment texture, OM enrichment, sediment redox conditions, and tidal influence. These findings provide a conceptual interpretation of factors associated with SOD variability and offer a scientific basis for understanding potential benthic oxygen demand and associated oxygen-depletion risk in tidal river systems.
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