Talk:Oxygen cycle

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Stuff at the beginning of the talk page, beforehand without heading[edit]

Seasonal O2/CO2 ratios: I am trying to find out how much, if any, the O2 ratio in the atmosphere changes with the seasons. Some sources show O2/CO2 ratios varying considerably in the summer and winter in each hemisphere. Other sources say that there is no seasonal variability,and that the O2 level is always around 20%. What's the true story here?

Why no hydrosphere? Just wondering why the overview paragraph and the image make no reference to the hydrosphere. Surely this is a significant resevoir for oxygen given that there is dissolved O2 and CO2 and there is H2O itself. - Drstuey 07:28, 22 Nov 2004 (UTC)

Answer: I decided not to differentiate between the hydrosphere and biosphere, mainly because I didn't have enough info to break down the biosphere reservoir into land surface and hydrosphere components. Also, dissolved O2 levels in the hydrosphere are a function of biologic activity. For an interesting theory on the relationship between the evolution of photosynthetic life, dissolved oxygen in the ocea, and the worlds main commercial source of iron, check out the banded iron formation. - Cbusch01 14:46, 13 Jul 2005 (MST)


As I am researching the subject of what regulates the oxygen content of the atmosphere, I have found the works of professor Watson and dr Lenton at East Anglia University ( see here: , particular the pieces that have Redfield Revisited in their title). It is not easy stuff (as I am but a humble journalist), but what I have understood so far is that the oxygen production by photosynthesis is a netto neutral affair, in that all the oxygen produced by trees shrubs and plankton is consumed by the breakdown of these organisms. So there must be other oxygen sources and if I understand Watson/Lenton well then one of these sources is the chemical weathering of rocks by plantroots that releases oxygen in the atmosphere and the burial of marine life in geologic time that once produced oxygen but which was buried without reclaiming the produced oxygen back. Bu~t I would be very happy to see on the Wiki page how you interpret this. Thanks

Theo Richel ( 09:52, 30 November 2006 (UTC)

Answer: The amount of "free" oxygen in the atmosphere is dominated by photosynthesis. By free oxygen I mean that in the form of O2 gas. It is true that all the oxygen produced by photosynthesis is eventually consumed by respiration and decay, but there is a lag between when it is produced and when it is consumed that allows it to remain in the atmosphere for a period of time. A good analogy for atmospheric oxygen is a stream-fed lake. Initially, the flow of water into the lake bed is greater than the flow out and the lake slowly fills up with water. Eventually the water level in the lake is high enough that the routes of escape for water can keep up with the incoming stream, thus reaching the point that the inflow and outflow are in equilibrium (the netto neutral affair you mentioned). Although the lake level is now static, it is still filled with water. In the same manner, the oxygen "lake" in the atmosphere is still full even though the level is basically static. If the photosysntesis stream were ever turned off, the free oxygen "lake" would eventually dry up. But here is the tricky part: the oxygen molecules would still remain in the atmosphere. However, instead of being in the form of free oxygen (O2), it would be converted to carbon dioxide (CO2) via respiration and decay. Without photosynthesis, the planet earth would have a nitrogen/carbon dioxide atmosphere instead of the nitrogen/oxygen atmosphere we currently enjoy. There are other sources of atmospheric free oxygen instead of photosynthesis, but these other sources produce so little oxygen that they are virtually insignificant in the big picture. By-the-way, the main source of carbon dioxide and nitrogen in the atmosphere is volcanoes. See the carbon cycle and nitrogen cycle articles for further discussion. - Cbusch01 09:23, 07 May 2008 (CST)

Oxidation of iron ores - error in chemical equation[edit]

I noticed that the stoichiometry of the equation for formation of rusts through weathering was incorrect.

4FeO + 3O2 → 2Fe2O3

I've corrected it as it shouldn't be controversial! —Preceding unsigned comment added by Parallelepipete (talkcontribs) 11:22, 14 August 2008 (UTC)

Incomplete cycle[edit]

There is something not properly noted here: the water. It's ridiculous to include photolysis in the balancing, but not, for example, the watery part of photosynthesis and metabolism. Also oceans are a far bigger reservoir than the atmosphere (I do not mean the soluble O2 here.). -- Tomdo08 (talk) 03:51, 20 December 2010 (UTC)

Decline in oxygen levels.[edit]

According to the wikipedia article about phytoplankton, phytoplankton levels have been decreasing with about 1% every year the last 111 years ( which should correspond to decline of about 67% ). I have also read that the landmass covered by rain forests have decreased from about 14% to about 6% the last century ( which should correspond to a decline of about 43% ). As phytoplankton produces about 50% of the atmospheric oxygen while rain forests produce about 28% of the atmospheric oxygen, this should correspond to a decline of about 45% in global photosynthetic activity if I am right. I also calculated from the data in this article that without any photosynthetic activity the atmospheric oxygen will be depleted in 4666.67 years ( (1.4 * 10^18) / (3.0 * 10^14) ), but the usage of oxygen must also have increased due to the combustion of fossil fuels. Perhaps some information about this should be included in the article if my calculations are right. (talk) 12:36, 30 December 2010 (UTC)

Updating the sources data[edit]

From articles I've read and videos I've watched the belief among oceanographers is that the amount of atmospheric O2 believed to be from ocean is somewhere between 50% and 80% sources. One name in particular is Dr Charles Trick who said "Over 50%" as a conservative estimate. This wikipedia article uses data from 1980 and could probably use an update from a more contemporary source.

Cheers — Preceding unsigned comment added by (talk) 19:09, 18 May 2013 (UTC)