A fraction comes from the breakup of water (photolysis) from ultraviolet radiation.
"The oxygen in today's atmosphere is almost entirely the result of photosynthetic living, which had its start with the appearance of blue-green algae among the microorganisms."The annual gain of atmospheric oxygen is shown below:
― Lewis Thomas
Plants, algae, and cyanobacteria perform photosynthesis which maintains atmospheric oxygen and supplies all of the organic compounds and most of the energy necessary to sustain life in Earth's biosphere.
Photolysis of N2O
Photolysis of H2O
16,50013,5001.30.03 Total ~ 30,000 units 1010 kg O2 per year
"One hundred and fifty years ago, the monster began, this country had become a place of industry. Factories grew on the landscape like weeds. Trees fell, fields were up-ended, rivers blackened. The sky choked on smoke and ash, and the people did, too, spending their days coughing and itching, their eyes turned forever toward the ground. Villages grew into town, towns into cities. And people began to live on the earth rather than within it."
― Patrick Ness, A Monster Calls
|An LED screen in Tiananmen Square showing the rising sun|
in a tourism advertisement for China’s Shandong province
while Beijing is shrouded in smog. 16 January 2014.
- Oxygen Cycle, Wikipedia.
- China starts televising the sunrise on giant TV screens because Beijing is so clouded in smog, by James Nye, Daily Mail, 17 January 2014.
- Late Night Thoughts on Listening to Mahler's Ninth Symphony, Lewis Thomas, 1995.
- Photosynthesis, Wikipedia.