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In this layer ozone concentrations are about 2 to 8 parts per million, which is much higher than in the lower atmosphere but still very small compared to the main components of the atmosphere. It is mainly located in the lower portion of the stratosphere from about 15–35 km (9.3–21.7 mi; 49,000–115,000 ft), though the thickness varies ...
Other estimates of the oceanic contribution to atmospheric oxygen are higher, while some estimates are lower, suggesting oceans produce ~45% of Earth's atmospheric oxygen each year. [78] A simplified overall formula for photosynthesis is [79] 6 CO 2 + 6 H 2 O + photons → C 6 H 12 O 6 + 6 O 2. or simply carbon dioxide + water + sunlight → ...
Dry air (mixture of gases) from Earth's atmosphere contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and traces of hydrogen, helium, and other "noble" gases (by volume), but generally a variable amount of water vapor is also present, on average about 1% at sea level. [5]
Photosynthetic prokaryotic organisms that produced O 2 as a byproduct lived long before the first build-up of free oxygen in the atmosphere, [5] perhaps as early as 3.5 billion years ago. The oxygen cyanobacteria produced would have been rapidly removed from the oceans by weathering of reducing minerals, [citation needed] most notably ferrous ...
Oxygen, O 2, meanwhile, was present in the atmosphere at just 0.001% of its present atmospheric level. [ 11 ] [ 12 ] The Sun shone at about 70% of its current brightness 4 billion years ago, but there is strong evidence that liquid water existed on Earth at the time.
The concentration of oxygen in the air (mmols O 2 per liter of air) therefore decreases at the same rate as the atmospheric pressure. [26] At sea level, where the ambient pressure is about 100 kPa, oxygen constitutes 21% of the atmosphere and the partial pressure of oxygen (P O 2) is 21 kPa (i.e. 21% of 100 kPa).
The Air Quality Index (AQI) — which measures the concentration of pollutants in the air — seemed to confirm all was well in the L.A. atmosphere, with low numbers that suggested clean, healthy air.
The order of elements by volume fraction (which is approximately molecular mole fraction) in the atmosphere is nitrogen (78.1%), oxygen (20.9%), [20] argon (0.96%), followed by (in uncertain order) carbon and hydrogen because water vapor and carbon dioxide, which represent most of these two elements in the air, are variable components. Sulfur ...