scholarly journals Contribution of Organic Matter Decomposition in Water Column to Oxygen Consumption in the Inner Part of the Ariake Sea

2019 ◽  
Vol 42 (5) ◽  
pp. 195-200 ◽  
Author(s):  
Koji UCHINO ◽  
Haruka INOMATA ◽  
Saki TAHARA ◽  
Hiroyuki TAKASU
Keyword(s):  
Organic Matter ◽  
Oxygen Consumption ◽  
Water Column ◽  
Organic Matter Decomposition ◽  
Ariake Sea

scholarly journals Tracing the origin of the oxygen-consuming organic matter in the hypoxic zone in a large eutrophic estuary: the lower reach of the Pearl River Estuary, China

2017 ◽  
Vol 14 (18) ◽  
pp. 4085-4099 ◽  
Author(s):  
Jianzhong Su ◽  
Minhan Dai ◽  
Biyan He ◽  
Lifang Wang ◽  
Jianping Gan ◽  
...  
Keyword(s):  
Organic Matter ◽  
Oxygen Consumption ◽  
Water Column ◽  
Algal Blooms ◽  
Dissolved Inorganic Carbon ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
Terrestrial Organic Matter ◽  
Hypoxic Zone

Abstract. We assess the relative contributions of different sources of organic matter, marine vs. terrestrial, to oxygen consumption in an emerging hypoxic zone in the lower Pearl River Estuary (PRE), a large eutrophic estuary located in Southern China. Our cruise, conducted in July 2014, consisted of two legs before and after the passing of Typhoon Rammasun, which completely de-stratified the water column. The stratification recovered rapidly, within 1 day after the typhoon. We observed algal blooms in the upper layer of the water column and hypoxia underneath in bottom water during both legs. Repeat sampling at the initial hypoxic station showed severe oxygen depletion down to 30 µmol kg−1 before the typhoon and a clear drawdown of dissolved oxygen after the typhoon. Based on a three endmember mixing model and the mass balance of dissolved inorganic carbon and its isotopic composition, the δ13C of organic carbon remineralized in the hypoxic zone was −23.2 ± 1.1 ‰. We estimated that 65 ± 16 % of the oxygen-consuming organic matter was derived from marine sources, and the rest (35 ± 16 %) was derived from the continent. In contrast to a recently studied hypoxic zone in the East China Sea off the Changjiang Estuary where marine organic matter dominated oxygen consumption, here terrestrial organic matter significantly contributed to the formation and maintenance of hypoxia. How varying amounts of these organic matter sources drive oxygen consumption has important implications for better understanding hypoxia and its mitigation in bottom waters.

scholarly journals The Roles of Resuspension, Diffusion and Biogeochemical Processes on Oxygen Dynamics Offshore of the Rhone River, France: A Numerical Modeling Study

2016 ◽  
Author(s):  
Julia M. Moriarty ◽  
Courtney K. Harris ◽  
Christophe Rabouille ◽  
Katja Fennel ◽  
Marjorie A. M. Friedrichs ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Organic Matter ◽  
Oxygen Consumption ◽  
Water Column ◽  
Bottom Boundary Layer ◽  
Water Interface ◽  
Bottom Boundary ◽  
Rhône Delta ◽  
Oxygen Dynamics

Abstract. Observations indicate that seabed resuspension of organic material and the associated entrainment of porewater into the overlying water can alter biogeochemical fluxes in some environments, but measuring the role of sediment processes on oxygen and nutrient dynamics is challenging. A modeling approach offers a means of quantifying these fluxes for a range of conditions, but models have typically relied on simplifying assumptions regarding seabed-water column interactions. Thus, to evaluate the role of resuspension on biogeochemical dynamics, we developed a coupled hydrodynamic, sediment transport, and biogeochemical model (HydroBioSed) within the Regional Ocean Modeling System (ROMS). This coupled model accounts for processes including the storage of particulate organic matter (POM) and dissolved nutrients within the seabed; entrainment of this material into the water column via resuspension and diffusion at the sediment-water interface; and biogeochemical reactions within the seabed. A one-dimensional version of HydroBioSed was then implemented for the Rhone Delta, France. To isolate the role of resuspension on biogeochemical dynamics, this model implementation was run for a two-month period that included three resuspension events; also, the supply of organic matter, oxygen and nutrients to the water column was held constant in time. Consistent with time-series observations from the Rhone Delta, model results showed that resuspension increased the diffusive flux of oxygen into the seabed by increasing the vertical gradient of oxygen at the seabed-water interface. This enhanced supply of oxygen to the seabed allowed seabed oxygen consumption to increase, primarily through nitrification. Resuspension of POM into the water column, and the associated increase in remineralization, also increased oxygen consumption in the bottom boundary layer. During these resuspension events, modeled rates of oxygen consumption increased by up to factors of ~ 2 and ~ 8 in the seabed and bottom boundary layer, respectively. When averaged over two months, the intermittent cycles of erosion and deposition led to a 20 % increase of oxygen consumption in the seabed, as well as a larger increase of ~ 200 % in the bottom boundary layer. These results imply that observations collected during quiescent periods, and biogeochemical models that neglect resuspension or use typical parameterizations for resuspension, may underestimate net oxygen consumption at sites like the Rhone Subaqueous Delta. Local resuspension likely has the most pronounced effect on oxygen dynamics at study sites with a high oxygen concentration in the bottom boundary layer, only a thin seabed oxic layer, and abundant labile organic matter.

scholarly journals The roles of resuspension, diffusion and biogeochemical processes on oxygen dynamics offshore of the Rhône River, France: a numerical modeling study

2017 ◽  
Vol 14 (7) ◽  
pp. 1919-1946 ◽  
Author(s):  
Julia M. Moriarty ◽  
Courtney K. Harris ◽  
Katja Fennel ◽  
Marjorie A. M. Friedrichs ◽  
Kehui Xu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Oxygen Consumption ◽  
Water Column ◽  
Water Interface ◽  
Regional Ocean Modeling System ◽  
Biogeochemical Models ◽  
Rhône Delta ◽  
Rhone Delta ◽  
Oxygen Dynamics

Abstract. Observations indicate that resuspension and associated fluxes of organic material and porewater between the seabed and overlying water can alter biogeochemical dynamics in some environments, but measuring the role of sediment processes on oxygen and nutrient dynamics is challenging. A modeling approach offers a means of quantifying these fluxes for a range of conditions, but models have typically relied on simplifying assumptions regarding seabed–water-column interactions. Thus, to evaluate the role of resuspension on biogeochemical dynamics, we developed a coupled hydrodynamic, sediment transport, and biogeochemical model (HydroBioSed) within the Regional Ocean Modeling System (ROMS). This coupled model accounts for processes including the storage of particulate organic matter (POM) and dissolved nutrients within the seabed; fluxes of this material between the seabed and the water column via erosion, deposition, and diffusion at the sediment–water interface; and biogeochemical reactions within the seabed. A one-dimensional version of HydroBioSed was then implemented for the Rhône subaqueous delta in France. To isolate the role of resuspension on biogeochemical dynamics, this model implementation was run for a 2-month period that included three resuspension events; also, the supply of organic matter, oxygen, and nutrients to the model was held constant in time. Consistent with time series observations from the Rhône Delta, model results showed that erosion increased the diffusive flux of oxygen into the seabed by increasing the vertical gradient of oxygen at the seabed–water interface. This enhanced supply of oxygen to the seabed, as well as resuspension-induced increases in ammonium availability in surficial sediments, allowed seabed oxygen consumption to increase via nitrification. This increase in nitrification compensated for the decrease in seabed oxygen consumption due to aerobic remineralization that occurred as organic matter was entrained into the water column. Additionally, entrainment of POM into the water column during resuspension events, and the associated increase in remineralization there, also increased oxygen consumption in the region of the water column below the pycnocline. During these resuspension events, modeled rates of oxygen consumption increased by factors of up to  ∼  2 and  ∼  8 in the seabed and below the pycnocline, respectively. When averaged over 2 months, the intermittent cycles of erosion and deposition led to a  ∼  16 % increase of oxygen consumption in the seabed, as well as a larger increase of  ∼  140 % below the pycnocline. These results imply that observations collected during quiescent periods, and biogeochemical models that neglect resuspension or use typical parameterizations for resuspension, may underestimate net oxygen consumption at sites like the Rhône Delta. Local resuspension likely has the most pronounced effect on oxygen dynamics at study sites with a high oxygen concentration in bottom waters, only a thin seabed oxic layer, and abundant labile organic matter.

Characterisation of production of organic rich topsoil from sludge

2000 ◽  
Vol 42 (9) ◽  
pp. 195-201 ◽  
Author(s):  
P. Andreasen ◽  
P. B. Mortensen ◽  
A. Stubsgaard ◽  
B. Langdahl
Keyword(s):  
Organic Matter ◽  
Oxygen Consumption ◽  
Oxygen Transport ◽  
Mineral Soil ◽  
Climatic Conditions ◽  
Growth Media ◽  
Soil Mixture ◽  
Water Suspension ◽  
Aerobic Process ◽  
Stable Product

The stabilisation of a sludge-mineral soil mixture and a method to evaluate the state of stabilisation were investigated. The organic matter and nitrogen content are reduced up to 50% during a stabilisation process of three months under Danish climatic conditions. The stabilisation was shown to be an aerobic process limited by oxygen transport within the mixture. The degree of stabilisation was evaluated by oxygen consumption in a water suspension and the results showed that a stable product was achieved when oxygen consumption was stable and in the level of natural occurring aerobic soils (0.1 mgO2/(g DS*hr). The study thereby demonstrates that a stability of a growth media can be controlled by the oxygen consumption method tested.

Design and test of a generic cohort model of soil organic matter decomposition: the SOMKO model

2001 ◽  
Vol 10 (6) ◽  
pp. 639-660 ◽  
Author(s):  
Jacques Gignoux ◽  
Joanna House ◽  
David Hall ◽  
Dominique Masse ◽  
Hassan B. Nacro ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Organic Matter Decomposition ◽  
Cohort Model ◽  
Soil Organic Matter Decomposition

Soil drying and organic matter decomposition

1967 ◽  
Vol 26 (2) ◽  
pp. 269-276 ◽  
Author(s):  
W. O. Enwezor
Keyword(s):  
Organic Matter ◽  
Organic Matter Decomposition ◽  
Soil Drying
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