Biology atmosphere

Biological sources account for the overwhelming fraction of O2 found in the present atmosphere. Considerable controversy and no small degree of uncertainty surrounds the mechanism of oxygen formation in the pre-biological atmosphere (Levine et al., 1981 Levine, 1982). The attractive suggestion that the photodecomposition of H2O by vacuum ultraviolet light in... 

Thus it should be stated in spite of the fact that some free oxygen could be formed in the pre-biologic atmosphere by the photodissociation of water vapour, its present level cannot be explained by this process alone. 

Nitrogen (N2). the principal constituent of the earth s atmosphere today, is believed to be produced from ammonia photolysis in the pre-biological atmosphere ... 

As mentioned above, thermotropic phase transitions may be brought about at constant pressure by adding or removing heat. (In biology, atmospheric pressure is considered constant for all practical purposes.) This is the case when ice is heated up to give liquid water, or when a lipid bilayer in the Lp phase is heated up to give an La phase. In thermodynamics, the amount of heat gained or lost by a system at constant pressure is called enthalpy (H). We can write ... 

Phthalates in Air. Atmospheric levels of phthalates in general are very low. They vary, for DEHP, from nondetectable to 132 ng/m (50). The latter value, measured in 1977, is the concentration found in an urban area adsorbed on airborne particulate matter and hence the biological avaUabUity is uncertain. More recent measurements (52) in both industrial and remote areas of Sweden showed DEHP concentrations varying from 0.3 to 77 ng/m with a median value of 2 ng/m. ... 

Sulfolane causes minimal and transient eye and skin irritation (19,20). Inhalation of sulfolane vapors in a saturated atmosphere is not considered biologically significant. However, when aerosol dispersions have been used to elevate atmospheric concentration, blood changes and convulsions have been observed in laboratory animals (22,31). Convulsions caused by sulfolane injected intraperitoneaHy have also been studied (32). 

Dimethyl sulfoxide occurs widely at levels of <3 ppm. It has been isolated from spearmint oil, com, barley, malt, alfalfa, beets, cabbage, cucumbers, oats, onion, Swiss chard, tomatoes, raspberries, beer, coffee, milk, and tea (5). It is a common constituent of natural waters, and it occurs in seawater in the 2one of light penetration where it may represent a product of algal metaboHsm (6). Its occurrence in rainwater may result from oxidation of atmospheric dimethyl sulfide, which occurs as part of the natural transfer of sulfur of biological origin (7,8). 

Pollutant Distribution. Of particular importance for the aquatic ecosystem is the distribution of volatile substances, eg, gases and volatile organic compounds, between the atmosphere and water, and the sorption of compounds at soHd surfaces, eg, settling suspended matter, biological particles, sediments, and soils (41,42). 

Some hydrogen cyanide is formed whenever hydrocarbons (qv) are burned in an environment that is deficient in air. Small concentrations are also found in the stratosphere and atmosphere. It is not clear whether most of this hydrogen cyanide comes from biological sources or from high temperature, low oxygen processes such as coke production, but no accumulation has been shown (3). 

Oceanic biology is a sink for atmospheric CO2 because of the involvement of the aqueous form of this gas in planktonic photosynthesis. This complex process can be summarized by... 

Changes in surface temperature elsewhere in the globe are likely to have a lesser impact on carbon or DMS production. For example, the warming that a doubling of atmospheric COj could produce in the Southern Ocean has been modelled to lead to decreased carbon uptake, but enhanced biological productivity, due to the temperature effect on phytoplankton growth." This would lead to an approximately 5% increase in DMS production and a lesser increase in CCN. There is thus a negative feedback here, but only of minor impact. 

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