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Anaerobic oxidation of methane (AOM) is a methane-consuming microbial process occurring in anoxic marine and freshwater sediments.AOM is known to occur among mesophiles, but also in psychrophiles, thermophiles, halophiles, acidophiles, and alkophiles. [1]
Water aeration is the process of increasing or maintaining the oxygen saturation of water in both natural and artificial environments. Aeration techniques are commonly used in pond, lake, and reservoir management to address low oxygen levels or algal blooms. [1]
In OMZs oxygen concentration drops to levels <10 nM at the base of the oxycline and can remain anoxic for over 700 m depth. [7] This lack of oxygen can be reinforced or increased due to physical processes changing oxygen supply such as eddy-driven advection, [7] sluggish ventilation, [8] increases in ocean stratification, and increases in ocean temperature which reduces oxygen solubility.
The mechanism of ·OH production (Part 1) highly depends on the sort of AOP technique that is used. For example, ozonation, UV/H 2 O 2, photocatalytic oxidation and Fenton's oxidation rely on different mechanisms of ·OH generation: UV/H 2 O 2: [6] [12] [13] H 2 O 2 + UV → 2·OH (homolytic bond cleavage of the O-O bond of H 2 O 2 leads to ...
Many organisms require hypoxic conditions. Oxygen is poisonous to anaerobic bacteria for example. [3] Oxygen depletion is typically expressed as a percentage of the oxygen that would dissolve in the water at the prevailing temperature and salinity. A system with low concentration—in the range between 1 and 30% saturation—is called hypoxic ...
Secondly, ocean deoxygenation occurs also in the open ocean. In that part of the ocean, there is nowadays an ongoing reduction in oxygen levels. As a result, the naturally occurring low oxygen areas (so called oxygen minimum zones (OMZs)) are now expanding slowly. [4] This expansion is happening as a consequence of human caused climate change.
In some fish, capillary blood flows in the opposite direction to the water, causing countercurrent exchange. The muscles on the sides of the pharynx push the oxygen-depleted water out the gill openings. In bony fish, the pumping of oxygen-poor water is aided by a bone that surrounds the gills called the operculum. [6]
In deep water systems (e.g. oceans), water can be out of contact with the atmosphere for extremely long periods of time (years, decades, centuries) and large positive AOU values are typical. On occasion, where near-surface primary production has raised oxygen concentrations above saturation, negative AOU values are possible (i.e. oxygen has not ...