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Resource: used or used up in processesOxygen
Appears in 61 processs and 135 steps. Everything below is linked: open a process to see it in context.
Top processes
Soil gas exchange and redox
10 stepsBacteria and archaea
10 stepsLiving soil system
8 steps- Soil gas exchange and redox
- Saprotrophic fungi
- Bacteria and archaea
- and 5 more in this process
- Fick's law: gas flux = -Ds dC/dz, where Ds is the soil gas diffusion coefficient
- Gases diffuse about 10,000 times faster in air than in water (O2 about 2e-5 versus 2e-9 m2/s), so water-filled pores block aeration
- Millington-Quirk model Ds/D0 = e^(10/3)/phi^2: at porosity 0.5, cutting air-filled porosity from 0.30 to 0.10 reduces Ds/D0 from about 0.07 to 0.002
- and 4 more in this process
- High-affinity oxidisers (upland soil clusters, USC-alpha and USC-gamma, and a Methylocystis pMMO2) consume atmospheric methane
- Low-affinity Type I and Type II methanotrophs oxidise elevated methane near wet soil, rice paddies and landfill covers
- Particulate methane monooxygenase (pMMO) oxidises CH4 to methanol using O2 and a reductant, then methanol dehydrogenase yields formaldehyde
- and 2 more in this process
Show 55 more processes
Saprotrophic fungi
4 stepsDecomposition
3 stepsNitrogen cycling
3 steps- Pyrite is exposed to Oxygen when drainage lowers the water table or sulfidic sediment is excavated
- Oxygen oxidises pyrite: Fe2+ and sulfate are released, giving about 2 mol H+ per mol FeS2 before Fe2+ is oxidised
- Fe2+ oxidation is rate-limiting; Acidithiobacillus ferrooxidans speeds it by orders of magnitude (about 10^5 to 10^6) below pH 3.5
- Methane reaches the surface by diffusion, bubbling or plant aerenchyma (in rice, over 90% of emitted CH4 passes through the plants)
- Methanotrophs oxidize Methane with methane monooxygenase in oxic layers and the rhizosphere, consuming roughly 20-80% of the methane produced (midpoint about 50% in paddies)
- Aerated upland soils with high-affinity methanotrophs take up atmospheric Methane: global soil sink about 30 Tg CH4 per year (range 11-49)
- A high water table excludes oxygen and the enzyme latch (phenol oxidase starved of oxygen) slows decomposition
- Methanotrophs in the oxic surface layer oxidise commonly half or more (20-90%) of the Methane before it escapes
- Drainage or drought lowers the water table, oxygen enters and peat respires CO2 (drained peatland about 0.3% of land, about 5% of human CO2-equivalent emissions)
- Waterlogging fills pores, and gas diffusion in water is roughly 10,000 times slower than in air, so soil goes anoxic within hours to days
- Wetland plants form aerenchyma (root gas space of tens of percent, up to about 40 to 50 percent in rice) that carries oxygen from shoot to root
- Radial oxygen loss leaks Oxygen into the soil, forming an oxidised zone a millimetre or so thick around roots
Organic matter decomposition
2 stepsSoil sulfur cycling
1 stepOften found with
Carbon dioxide 40Water 33Methane 19Nitrate 19Pore space 13Ammonium 12Bacteria 11Soil water 11Fungi 10Plants 10Plant roots 10Atmosphere 9
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