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Soil gases (soil atmosphere [1]) are the gases found in the air space between soil components. The spaces between the solid soil particles, if they do not contain water, are filled with air. The primary soil gases are nitrogen, carbon dioxide and oxygen. [2] Oxygen is critical because it allows for respiration of both plant roots and soil ...
Mitigation may be by supplementary oxygen, pressurisation of the habitat or environmental protection suit, or a combination of both. In all cases the critical effect is the raising of oxygen partial pressure in the breathing gas. [1] Room air at altitude can be enriched with oxygen without introducing an unacceptable fire hazard.
[8] [9] Since the start of the Cambrian period, atmospheric oxygen concentrations have fluctuated between 15% and 35% of atmospheric volume. [10] 430-million-year-old fossilized charcoal produced by wildfires show that the atmospheric oxygen levels in the Silurian must have been equivalent to, or possibly above, present day levels. [11]
At the peak, the partial pressure of oxygen is only about 60% of that at sea level. Water boils at 186 °F (86 °C) at 14,000 feet, rather than 212 °F (100 °C) at sea level. [32] A faster rate of respiration is required by humans and animals not acclimated to high altitudes. [33]
Sensor readings seemed to show that oxygen was being made on the seabed 4,000 meters (about 13,100 feet) below the surface, where no light can penetrate. ... What he expected the sensor to detect ...
[72] [71] Platy soil structure and soil compaction (low porosity) impede gas flow, and a deficiency of oxygen may encourage anaerobic bacteria to reduce (strip oxygen) from nitrate NO 3 to the gases N 2, N 2 O, and NO, which are then lost to the atmosphere, thereby depleting the soil of nitrogen, a detrimental process called denitrification. [73]
The release rate of that soil carbon as carbon dioxide by respiration of soil microbes was an unknown that the Biosphere 2 experiment was designed to reveal. Subsequent research showed that Biosphere 2's farm soils had reached a more stable ratio of carbon and nitrogen, lowering the rate of CO 2 release, by 1998.
An aquatic system lacking dissolved oxygen (0% saturation) is termed anaerobic, reducing, or anoxic. In water, oxygen levels are approximately 7 ppm or 0.0007% in good quality water, but fluctuate. [5] Many organisms require hypoxic conditions. Oxygen is poisonous to anaerobic bacteria for example. [3]