User:Rotheconrad/sandbox

Lead Section:
The oxygen cycle is the biogeochemical transitions of oxygen atoms between different oxidation states in ions, oxides, and molecules through redox reactions within and between the spheres/reservoirs of the planet Earth. The word oxygen in the literature typically refers to the most common oxygen allotrope, elemental/diatomic oxygen (O2), as it is a common product or reactant of many biogeochemical redox reactions within the cycle. Knowledge of the oxygen cycle is split into past and present with the development of the oxygen cycle on the early/historic Earth followed by the modern oxygen cycle currently observed. Processes within the oxygen cycle are considered to be biological or geological and are evaluated as either a source (O2 production) or sink (O2 consumption). While there are many abiotic sources and sinks for O2, the presence of the profuse concentration of free oxygen in modern Earth's atmosphere and ocean is attributed to O2 production from the biological process of oxygenic photosynthesis in conjunction with a biological sink known as the biological pump and a geologic process of carbon burial involving plate tectonics. Biology is the main driver of O2 flux on modern Earth, and the evolution of oxygenic photosynthesis by bacteria, which is discussed as part of The Great Oxygenation Event, is thought to be directly responsible for the conditions permitting the development and existence of all complex eukaryotic metabolism and life.

Surface Reservoirs.
The atmospheric reservoir contains ~21% O2 which equates to a total of roughly 34x1018 mol of oxygen. Oxygen from the atmosphere forms an equilibrium concentration by gas exchange with the hydrosphere as a dissolved gas in aqueous solution according to Henry's law. According to this law, O2 saturates in water at 450µM at 0ºC and 270µM at 25ºC, but other dissolved solutes in seawater can reduce this saturation concentration. Oxygen concentrations in the hydrosphere can be influenced locally by the presence or absence of turbulent mixing or local production or consumption of O2 by biological metabolism. Oxygen concentration in the soil and groundwater of the pedosphere is determined by gas diffusion through soil pore space in air and rainwater and can also be influenced locally by biological processes. Seasonal high latitude O2 level fluctuations of +/- 15 p.p.m. in the northern hemisphere have been observed and attributed to seasonal cycles of primary production and respiration. Human combustion of fossil fuels has been linked to a measured decrease of around 1x1015 mol per year in O2 concentrations in recent decades. Besides elemental oxygen, oxygen atoms are also present in various forms spread throughout the surface reservoirs in the forms of biomass, H2O, CO2, HNO3, NO, NO2, CO, H2O2, O3, SO2, H2SO4, MgO, CaO, AlO, SiO2, and PO4.

Biological Sources of O2.
The more writing will be happening here.

Biological Sinks for O2.
The writing will be happening here.

Abiotic Sources of O2.
The more writing will be happening here.

Abiotic Sinks for O2.
The writing will be happening here.

Evaluating Content:
The introduction is short and completely void of references. No reference is made to historical oxygen level fluctuations. The Great Oxygenation Event is linked as well as the several other broad topic pages. There are four sections in the contents box. All four sections are short. I have not begun to study the current literature on the oxygen cycle yet and so I can not speak for the accuracy of information but it appears to be mostly from the 1980s. The first section is titled Reservoirs and is centered mainly around photosynthesis. Phytoplankton and Prochlorococcus are mentioned specifically along with respiration and photolysis. There is only one reference for the entire Reservoirs section. The second section lists capacities and fluxes in two tables with no additional text discussing them. The second reference for the page is for the table data. The third section is a very brief note on ozone that links to several pages. The references section seems to also include further reading or additional links. I do not find the page very readable or well organized. I am distracted by the lack of references. The descriptions include jargon that are linked to other pages. I think this page has room for improvement with rewriting existing sections and adding additional sections such as a history section. It also seems that the oxygen cycle is isolated in this page and so either the introduction or a separate section could be used to add context and global overview. Emphasis should be added for the imbalance between photosynthesis and respiration that leads to excess oxygen by carbon burial e.g. not all primary production is respired, some is buried and this creates excess oxygen. I will look for a reference for this. So overall the article needs restructured, additional sections, and context linking everything together in a global and historic capacity.

Evaluating Tone:
The tone of the article is briefly stated and largely undocumented but appears to be unbiased. It is more tersely informative than explanatory or enjoyable to read. The article appears neutral but very plain. I do not notice any disparities between viewpoints, but I have not yet begun to research this topic.

Evaluating Sources:
The first reference link is broken, is an article from Scientific American, and is given to support a claim from 1986 that Prochlorococcus accounts for more than half of the photosynthesis of the open ocean. So the first reference on this page is even directly related to oxygen. The second reference does not have a link but is from The Handbook of Environmental Chemistry books series by Springer published in 1980. This second reference is for two tables of data with no text telling what they are for. There are no numbered references after this but the section does include additional unnumbered bullet points not linked in the text and it looks like a mess. The references also appear to be several decades old, not to imply this is bad, but more current references are most likely available. The article itself contains many statements presented as fact without providing a reference. This section needs to be reorganized and redone.

Talk Page evaluation:
The first talk page entry is unsigned or dated. The second is a question from 22 Nov 2004 and an answer 13 Jul 2005. Another question was posted in Nov 2006 concerning free oxygen which was not answered until May 2008. There was an error in a chemical equation that was corrected. In Dec 2010 someone complained an an incomplete cycle and reservoir misinformation but it has not been discussed further or appear to have been changed/updated. Another question about decline in oxygen levels was posted in Dec 2010 with an answer in Dec 2018. It does not appear as if this changed the page. In May 2013 someone suggested to update the data on the page which is from 1980. The latest activity on the page is from Oct 2018. One comment says that the largest source of oxygen is not photosynthesis because photosynthesis is process. The actual source of oxygen is the organisms doing photosynthesis process. This article is rated as B-Class, has been listed as a level-5 vital article in Earth science, and is listed as High-importance on the WikiProject Ecology. It is listed as Mid-importance on the WikiProject Soil.

Talk Page Comment:
I have been assigned to update and make additions to this Wikipedia page for a graduate course. The reference section is disorganized, mostly unnumbered, and links are broken or absent. The references are several decades old and we have more current data. I plan to update the data with current numbers and redo the reference section. I also plan to add historical and global context to the page as well as greater depth and more accessible explanations. If anyone has requests or trepidations please share them and I will accommodate if feasible.

Planned Reference Additions

 * 1) Petsch, Steven (2014). "The global oxygen cycle". Treatise Geochem Second Ed. 10 (2014): 437-474. https://doi.org/10.1016/B978-0-08-095975-7.00811-1
 * 2) Huang, Jianping et al.  (2018). "The global oxygen budget and its future projection." Science Bulletin. 63 (18): 1180-1186. https://doi.org/10.1016/j.scib.2018.07.023
 * 3) Boyce, Daniel G.; Lewis, Marlon R.; Worm, Boris (2010). "Global phytoplankton decline over the past century." Nature. 466 (7306): 591-596. https://doi.org/10.1038/nature09268
 * 4) Behrenfeld, Michael J. et al.  (2006)l. "Climate-driven trends in contemporary ocean productivity." Nature. 444 (7120): 752-755. https://doi.org/10.1038/nature05317
 * 5) Lenton, Timothy M.; Watson, Andrew J. (2000). "Redfield revisited: 2. What regulates the oxygen content of the atmosphere?." Global Biogeochemical Cycles. 14 (1): 249-268. https://doi.org/10.1029/1999GB900076
 * 6) Resplandy, L. et al.  (2018). "Quantification of ocean heat uptake from changes in atmospheric O 2 and CO 2 composition." Nature. 563 (7729): 105-108. https://doi.org/10.1038/s41586-018-0651-8
 * Hu, Qingyang, et al. (2016). "FeO 2 and FeOOH under deep lower-mantle conditions and Earth’s oxygen–hydrogen cycles." Nature. 534 (7606): 241-244. https://doi.org/10.1038/nature18018
 * 1) Falkowski, Paul G.  (2011). "The biological and geological contingencies for the rise of oxygen on Earth." Photosynth Res. 107 (1): 7-10. https://doi.org/10.1007/s11120-010-9602-4
 * 2) Falkowski, Paul G.; Godfrey, Linda V. (2008). "Electrons, life and the evolution of Earth's oxygen cycle." Philosophical Transactions of the Royal Society B: Biological Sciences. 363 (1504): 2705-2716. https://doi.org/10.1098/rstb.2008.0054
 * 3) Keeling, Ralph F.; Körtzinger, Arne; Gruber, Nicolas (2010). "Ocean deoxygenation in a warming world". Annual Review of Marine Science. 2 (2010): 199-229. https://doi.org/10.1146/annurev.marine.010908.163855
 * 4) Holland, Heinrich D. (2006). "The oxygenation of the atmosphere and oceans." Philosophical Transactions of the Royal Society B: Biological Sciences. 361 (1470): 903-915. https://doi.org/10.1098/rstb.2006.1838
 * 5) Lyons, Timothy W.; Reinhard, Christopher T.; Planavsky, Noah J. (2014). "The rise of oxygen in Earth’s early ocean and atmosphere." Nature. 506 (7488): 307. https://doi.org/10.1038/nature13068
 * 6) Reinhard, Christopher T.; et al. (2016). "Earth’s oxygen cycle and the evolution of animal life." Proceedings of the National Academy of Sciences. 113 (32): 8933-8938. https://doi.org/10.1073/pnas.1521544113